CN102055335A

CN102055335A - Boost-buck type power supply converter and control method thereof

Info

Publication number: CN102055335A
Application number: CN2009102120789A
Authority: CN
Inventors: 陈科宏; 吴纬权; 何心欣
Original assignee: Richtek Technology Corp
Current assignee: Richtek Technology Corp
Priority date: 2009-11-03
Filing date: 2009-11-03
Publication date: 2011-05-11
Anticipated expiration: 2029-11-03
Also published as: CN102055335B

Abstract

The invention relates to a control method of a boost-buck type power supply converter, and the power supply converter comprises an inductor, a first switch connected between the input end of the power supply converter and the first end of the inductor, a second switch connected between the first end of the inductor and the grounding end, a third switch connected between the second end of the inductor and the grounding end, and a fourth switch connected between the second end of the inductor and the output end of the power supply converter; and the control method is characterized in that the control method comprises the following steps: detecting voltage at the input end and the output end and load current at the output end for deciding whether the power supply converter performs the operation in the buck mode, the first boost-buck mode, the second boost-buck mode or the boost mode; and controlling the first, the second, the third and the fourth switches during the first and the second boost-buck modes.

Description

Step-down/up type power supply changeover device and control method thereof

Technical field

The present invention relates to a kind of power supply changeover device, specifically, is a kind of step-down/up type power supply changeover device and control method thereof of improving switch cost and correct switch mode.

Background technology

Fig. 1 shows known step-down/up type power supply changeover device 10, and it comprises power stage 12 and control circuit 14.In power stage 12, switch SW 1 is connected between input voltage vin and the inductance L, and switch SW 2 is connected between inductance L and the earth terminal GND, and switch SW 3 is connected between inductance L and the earth terminal GND, and switch SW 4 is connected between inductance L and the output voltage V out.Resistance R 1 and R2 pressure-dividing output voltage Vout produce feedback signal VFB, in control circuit 14, error amplifier 24 produces error signal VEA according to feedback signal VFB and reference voltage Vref, sawtooth generator 22 provides two sawtooth signal SAW1 and SAW2, comparator 18 comparison error signal VEA and sawtooth signal SAW1 produce signal PWM1, comparator 20 comparison error signal VEA and sawtooth signal SAW2 produce signal PWM2, and control logic circuit 16 produces signal VA according to signal PWM1 and PWM2, VB, VC and VD be diverter switch SW1 respectively, SW2, SW3 and SW4 are to transfer input voltage vin to output voltage V out.When error signal VEA only switched to sawtooth signal SAW1 or SAW2, power supply changeover device 10 operated in decompression mode or boost mode, and when error signal VEA switched to two sawtooth signal SAW1 or SAW2, power supply changeover device 10 operated in the buck pattern.Yet, in fact, the waveform of sawtooth signal SAW1 and SAW2 is not an ideal linearity at peak value and valley, therefore, in input voltage vin during near output voltage V out, just the responsibility cycle of signal PWM1 or PWM2 near 100% o'clock, will make the ripple of output voltage V out become big than (duty ratio) because of nonlinear problem.

People such as Chen are at U.S. Patent number the 7th, 176, a kind of step-down/up type power supply changeover device is proposed in No. 667, it is when the buck pattern, utilize a sawtooth signal and error signal to cut out the responsibility cycle of needed buck or boost, and within described responsibility cycle, insert fixing boosting or the step-down responsibility cycle.Yet, no matter be the power supply changeover devices that the people proposed such as Fig. 1 or Chen, when the buck pattern, the switching circulation of switch is opened (turn on) switch SW 2 and SW4 and is closed (turn off) switch SW 1 and SW3 for (1), (2) open switch SW 1 and SW4 and off switch SW2 and SW3, (3) open switch SW 1 and SW3 and off switch SW2 and SW4, (4) open switch SW 1 and SW4 and off switch SW2 and SW3, because the number of times that switch switches in each cycle is more, so switch cost (switching loss) is also bigger.

Therefore known step-down/up type power supply changeover device exists above-mentioned all inconvenience and problem.

Summary of the invention

Purpose of the present invention is to propose a kind ofly to use new switching sequence at input voltage during near output voltage, reduces the step-down/up type power supply changeover device and the control method thereof of switch cost and conducting loss.

Another object of the present invention is to propose a kind ofly to prolong the switching cycle of switch to reduce the step-down/up type power supply changeover device and the control method thereof of switch cost at input voltage during near output voltage.

A further object of the present invention is to propose a kind ofly to consider that load current makes it can be at correct some switch mode to the influence of buck responsibility cycle, thus output voltage can be because of the change pattern affected step-down/up type power supply changeover device and control method thereof.

For achieving the above object, technical solution of the present invention is:

A kind of control method of step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one second switch is connected between first end and an earth terminal of described inductance, one the 3rd switch is connected between second end and described earth terminal of described inductance, and one the 4th switch be connected between the output of second end of described inductance and described power supply changeover device, it is characterized in that described control method comprises the following steps:

First step: the voltage and the load current on described output that detect on described input and the output operate in decompression mode, the first buck pattern, second buck pattern or the boost mode to determine described power supply changeover device;

Second step: when described first and second buck pattern, described first, second, third and the control of the 4th switch comprise:

(a) close described first switch, open described second switch, close described the 3rd switch, open described the 4th switch;

(b) open described first switch, close described second switch, keep described the 3rd switch and close, keep described the 4th switch opens;

(c) keep described first switch opens, keep described second switch and close, open described the 3rd switch, close described the 4th switch.

The control method of step-down/up type power supply changeover device of the present invention can also be further achieved by the following technical measures.

The step that aforesaid control method, the described power supply changeover device of wherein said decision operate in decompression mode, the first buck pattern, the second buck pattern or boost mode comprises the following steps:

First step: the multiplier value at the described inductance two ends that voltage and load current determined on described input and output determines described power supply changeover device to operate in decompression mode less than one first critical value;

Second step: the multiplier value at the described inductance two ends that voltage and load current determined on described input and output determines described power supply changeover device to operate in the described first buck pattern greater than described first critical value and less than one second critical value;

Third step: the multiplier value at the described inductance two ends that voltage and load current determined on described input and output determines described power supply changeover device to operate in the described second buck pattern less than one the 3rd critical value and greater than described second critical value;

The 4th step:, determine described power supply changeover device to operate in described boost mode when the multiplier value at the described inductance two ends that voltage and load current determined on described input and the output during greater than described the 3rd critical value.

Aforesaid control method wherein more comprises:

The difference of amplifying one first letter and reaching between the reference voltage produces a secondary signal, and described first signal is the function of voltage on the described output;

One first frequency and a second frequency are provided;

Operator scheme and described first frequency according to described power supply changeover device produce one the 3rd signal and one the 4th signal;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

Operator scheme, the described the 5th and the 6th signal, first frequency and second frequency according to described power supply changeover device are controlled the described first, second, third and the 4th switch.

Aforesaid control method, wherein when described decompression mode, the switching cycle of described first and second switch is a period 1; When the described first buck pattern described first, second, third and the switching cycle of the 4th switch be a second round greater than the described period 1; When the described second buck pattern described first, second, third and the switching cycle of the 4th switch be a period 3 greater than the described period 1; When described boost mode the described the 3rd and the switching cycle of the 4th switch be a period 4 less than described second and third cycle.

Aforesaid control method, wherein when the described first buck pattern, the described the 3rd and the responsibility cycle of the 4th switch fix.

Aforesaid control method, wherein when the described second buck pattern, the responsibility cycle of described first and second switch is fixed.

A kind of step-down/up type power supply changeover device is characterized in that, comprising:

One inductance;

One first switch is connected between first end of the input of described power supply changeover device and described inductance;

One second switch is connected between first end and an earth terminal of described inductance;

One the 3rd switch is connected between second end and described earth terminal of described inductance;

One the 4th switch is connected between the output of second end of described inductance and described power supply changeover device;

One control circuit, control described first, second, third and the switching of the 4th switch, and determine described power supply changeover device to operate in decompression mode, the first buck pattern, second buck pattern or the boost mode according to the load current on voltage on described input and the output and the described output;

Wherein, when described first and second buck pattern, described first, second, third and the control of the 4th switch comprise (a) and close described first switch, open described second switch, close described the 3rd switch and open described the 4th switch, (b) open described first switch, close described second switch, keep described the 3rd switch and close and keep described the 4th switch opens, and (c) keep described first switch opens, keep described second switch and close, open described the 3rd switch and close described the 4th switch.

Aforesaid power supply changeover device, the multiplier value at the described inductance two ends that voltage and described load current determined of wherein said control circuit on described input and output determines described power supply changeover device to operate in described decompression mode during less than one first critical value; The multiplier value at the described inductance two ends that voltage and described load current determined on described input and output determines described power supply changeover device to operate in the described first buck pattern during greater than described first critical value and less than one second critical value; The multiplier value at the described inductance two ends that voltage and described load current determined on described input and output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that voltage and load current determined on described input and output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

Aforesaid power supply changeover device, wherein said control circuit comprises:

One error amplifier produces a secondary signal according to one first signal and a reference voltage, and described first signal is the function of voltage on the described power supply changeover device output;

One frequency generator provides a first frequency and a second frequency;

One mode detector detects the input of described power supply changeover device and the voltage on the output and produces one the 3rd signal and operate in decompression mode, the first buck pattern, second buck pattern or the boost mode to determine described power supply changeover device;

One sawtooth generator provides one the 4th signal or one the 5th signal according to described the 3rd signal and first frequency;

One first comparator, more described secondary signal and described the 4th signal produce one the 6th signal;

One second comparator, more described secondary signal and described the 5th signal produce one the 7th signal;

One control logic circuit is according to the switching of described the 3rd, the 6th and the 7th signal and first and second FREQUENCY CONTROL described first, second, third and the 4th switch.

Aforesaid power supply changeover device, wherein said control logic circuit comprises:

One frequency eliminator produces one the 3rd frequency to described first frequency frequency elimination;

One first logical circuit produces one first control signal, second control signal, the 3rd control signal and the 4th control signal according to described the 6th signal, first frequency, second frequency, the 3rd frequency and one second reference voltage;

One first multiplexer is chosen the switching that one of them controls described first and second switch according to described three signals from the described first, second, third and the 4th control signal;

One second logical circuit produces one the 5th control signal, the 6th control signal, the 7th control signal and the 8th control signal according to described the 7th signal, first frequency, the 3rd frequency and one the 3rd reference voltage;

One second multiplexer is chosen one of them according to described the 3rd signal and is controlled the described the 3rd and the switching of the 4th switch from described the 5th, the 6th, the 7th and the 8th control signal.

Aforesaid power supply changeover device, wherein said frequency eliminator comprise D type flip-flop.

Aforesaid power supply changeover device, wherein when described decompression mode, the switching cycle of described first and second switch is a period 1; When the described first buck pattern described first, second, third and the switching cycle of the 4th switch be a second round greater than the described period 1; When the described second buck pattern described first, second, third and the switching cycle of the 4th switch be a period 3 greater than the described period 1; When described boost mode the described the 3rd and the switching cycle of the 4th switch be a period 4 less than described second and third cycle.

Aforesaid power supply changeover device, wherein when the described first buck pattern, the described the 3rd and the responsibility cycle of the 4th switch fix.

Aforesaid power supply changeover device, wherein when the described second buck pattern, the responsibility cycle of described first and second switch is fixed.

A kind of control method of step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one second switch is connected between first end and an earth terminal of described inductance, one the 3rd switch is connected between second end and described earth terminal of described inductance, and one diode have an anode and connect second end of described inductance and the output that a negative electrode connects described power supply changeover device, it is characterized in that described control method comprises the following steps:

First step: the voltage and the load current on the described output that detect on described input and the output operate in decompression mode, the first buck pattern, second buck pattern or the boost mode to determine described power supply changeover device;

Second step: when described first and second buck pattern, the control of described first, second and third switch comprises:

(a) close described first switch, open described second switch, close described the 3rd switch;

(b) open described first switch, close described second switch, keep described the 3rd switch and close;

(c) keep described first switch opens, keep described second switch and close, open described the 3rd switch.

The step that aforesaid control method, the described power supply changeover device of wherein said decision operate in decompression mode, the first buck pattern, the second buck pattern or boost mode comprises:

When the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during, determine described power supply changeover device to operate in decompression mode less than one first critical value;

When the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during, determine described power supply changeover device to operate in the described first buck pattern greater than described first critical value and less than one second critical value;

When the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during, determine described power supply changeover device to operate in the described second buck pattern less than one the 3rd critical value and greater than described second critical value; When the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during, determine described power supply changeover device to operate in described boost mode greater than described the 3rd critical value.

Aforesaid control method wherein more comprises:

The difference of amplifying between one first signal and the reference voltage produces a secondary signal, and described first signal is the function of voltage on the described output;

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

Operator scheme, the described the 5th and the 6th signal, first frequency and second frequency according to described power supply changeover device are controlled described first, second and third switch.

Aforesaid control method, wherein when described decompression mode, the switching cycle of described first and second switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described the 3rd switch is a period 4 less than described second and third cycle when described boost mode.

Aforesaid control method, wherein when the described first buck pattern, the responsibility cycle of described the 3rd switch is fixed.

One inductance;

One diode has an anode and connects second end of described inductance and the output that a negative electrode connects described power supply changeover device;

Wherein, when described first and second buck pattern, the control of described first, second and third switch comprises (a) and closes described first switch, opens described second switch and close described the 3rd switch, (b) open described first switch, close described second switch and keep described the 3rd switch and close, and (c) keep described first switch opens, keep described second switch and close and open described the 3rd switch.

Aforesaid power supply changeover device, voltage and the multiplier value at described inductance two ends that load current determined described output on during less than one first critical value of wherein said control circuit on described input and output determines described power supply changeover device to operate in described decompression mode; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described first buck pattern during greater than described first critical value and less than one second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

One frequency generator provides a first frequency and a second frequency;

One control logic circuit is according to the switching of described the 3rd, the 6th and the 7th signal and described first, second and third switch of first and second FREQUENCY CONTROL.

One first logical circuit produces one first control signal, second control signal and the 3rd control signal and the 4th control signal according to described the 6th signal, first frequency, second frequency, the 3rd frequency and one second reference voltage;

One second multiplexer is chosen the switching that one of them controls described the 3rd switch according to described the 3rd signal from described the 5th, the 6th, the 7th and the 8th control signal.

Aforesaid power supply changeover device, wherein when described decompression mode, the switching cycle of described first and second switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described the 3rd switch is a period 4 less than described second and third cycle when described boost mode.

Aforesaid power supply changeover device, wherein when the described first buck pattern, the responsibility cycle of described the 3rd switch is fixed.

A kind of control method of step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one diode has an anode and connects first end that an earth terminal and a negative electrode connect described inductance, one second switch is connected between second end and described earth terminal of described inductance, and one the 3rd switch be connected between the output of second end of described inductance and described power supply changeover device, it is characterized in that described control method comprises the following steps:

(a) close described first switch, close described second switch, open described the 3rd switch;

(b) open described first switch, keep described second switch and close, keep described the 3rd switch opens;

(c) keep described first switch opens, open described second switch, close described the 3rd switch.

When on described input and the output with described output on the multiplier value at the described inductance two ends that load current determined during greater than described first critical value and less than one second critical value, determine described power supply changeover device to operate in the described first buck pattern;

When the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during, determine described power supply changeover device to operate in the described second buck pattern less than one the 3rd critical value and greater than described second critical value;

When the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during, determine described power supply changeover device to operate in described boost mode greater than described the 3rd critical value.

Aforesaid control method wherein more comprises:

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

Aforesaid control method, wherein when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second and third switch is a period 4 less than described second and third cycle when described boost mode.

Aforesaid control method, wherein when the described first buck pattern, the responsibility cycle of described second and third switch is fixed.

Aforesaid control method, wherein when the described second buck pattern, the responsibility cycle of described first switch is fixed.

One inductance;

One diode has an anode and connects first end that an earth terminal and a negative electrode connect described inductance;

One second switch is connected between second end and described earth terminal of described inductance;

One the 3rd switch is connected between the output of second end of described inductance and described power supply changeover device;

One control circuit, control the switching of described first, second and third switch, and determine described power supply changeover device to operate in decompression mode, the first buck pattern, second buck pattern or the boost mode according to the load current on voltage on described input and the output and the described output;

Wherein, when described first and second buck pattern, the control of described first, second and third switch comprises (a) and closes described first switch, closes described second switch and open described the 3rd switch, (b) open described first switch, keep described second switch and close and keep described the 3rd switch opens, and (c) keep described first switch opens, open described second switch and close described the 3rd switch.

Aforesaid power supply changeover device, voltage and the multiplier value at described inductance two ends that load current determined described output on during less than one first critical value of wherein said control circuit on described input and output determines described power supply changeover device to operate in described decompression mode; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described first buck pattern during greater than one first critical value and less than one second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

One frequency generator provides a first frequency and a second frequency;

One first multiplexer is chosen the switching that one of them controls described first switch according to described three signals from the described first, second, third and the 4th control signal;

One second multiplexer is chosen the switching that one of them controls described second and third switch according to described the 3rd signal from described the 5th, the 6th, the 7th and the 8th control signal.

Aforesaid power supply changeover device, wherein when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second and third switch is a period 4 less than described second and third cycle when described boost mode.

Aforesaid power supply changeover device, wherein when the described first buck pattern, the responsibility cycle of described second and third switch is fixed.

42, power supply changeover device as claimed in claim 35 is characterized in that, when the described second buck pattern, the responsibility cycle of described first switch is fixed.

A kind of control method of step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one first diode has an anode and connects first end that an earth terminal and a negative electrode connect described inductance, one second switch is connected between second end and described earth terminal of described inductance, and one second diode have an anode and connect second end of described inductance and the output that a negative electrode connects described power supply changeover device, it is characterized in that described control method comprises the following steps:

Second step: when described first and second buck pattern, the control of described first and second switch comprises:

(a) close described first switch, close described second switch;

(b) open described first switch, keep described second switch and close;

(c) keep described first switch opens, open described second switch.

When the multiplier value at the described inductance two ends that voltage and load current determined on described input and the output during, determine described power supply changeover device to operate in described boost mode greater than described the 3rd critical value.

Aforesaid control method wherein more comprises:

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

Operator scheme, the described the 5th and the 6th signal, first frequency and described first and second switch of second frequency control according to described power supply changeover device.

Aforesaid control method, wherein when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first and second switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first and second switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second switch is a period 4 less than described second and third cycle when described boost mode.

Aforesaid control method, wherein when the described first buck pattern, the responsibility cycle of described second switch is fixed.

One inductance;

One first diode has an anode and connects first end that an earth terminal and a negative electrode connect described inductance;

One second diode has an anode and connects second end of described inductance and the output that a negative electrode connects described power supply changeover device;

One control circuit, control the switching of described first and second switch, and determine described power supply changeover device to operate in decompression mode, the first buck pattern, second buck pattern or the boost mode according to the load current on voltage on described input and the output and the described output;

Wherein, when described first and second buck pattern, the control of described first and second switch comprises (a) and closes described first switch and close described second switch, (b) open described first switch and keep described second switch and close, and (c) keep described first switch opens and open described second switch.

Aforesaid power supply changeover device, wherein said control circuit determines described power supply changeover device to operate in described decompression mode when the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during less than one first critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described first buck pattern during greater than described first critical value and less than one second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

One frequency generator provides a first frequency and a second frequency;

One control logic circuit is according to the switching of described the 3rd, the 6th and the 7th signal and described first and second switch of first and second FREQUENCY CONTROL.

One first logical circuit produces one first control signal, second control signal, the 3rd control signal and the 4th control signal according to described the 6th signal, first frequency, second frequency, the 3rd frequency and one the 3rd reference voltage;

One second multiplexer is chosen the switching that one of them controls described second switch according to described the 3rd signal from described the 5th, the 6th, the 7th and the 8th control signal.

Aforesaid power supply changeover device, wherein when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first and second switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first and second switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second switch is a period 4 less than described second and third cycle when described boost mode.

Aforesaid power supply changeover device, wherein when the described first buck pattern, the responsibility cycle of described second switch is fixed.

Aforesaid power supply changeover device, wherein when the described second buck pattern, the responsibility cycle of described first switch is fixed.

After adopting technique scheme, step-down/up type power supply changeover device of the present invention and control method thereof have the following advantages:

1. when power supply changeover device operates in the buck pattern,, and then reduce switch cost and conducting loss with new described at least two switches of transfer sequence control.

2. when power supply changeover device enters the buck pattern by decompression mode or boost mode, the switching cycle of described at least two switches is prolonged, with further minimizing switch cost, and consider that load current makes it put switch mode correct to the influence of buck responsibility cycle, so output voltage can be not influenced because of the change pattern.

Description of drawings

Fig. 1 is known step-down/up type power supply changeover device schematic diagram;

Fig. 2 is a first embodiment of the present invention schematic diagram;

Signal waveform when Fig. 3 operates in first pattern for power supply changeover device among Fig. 2;

Inductive current IL and switching sequence on the inductance L when Fig. 4 operates in first pattern for power supply changeover device among Fig. 2;

Signal waveform when Fig. 5 operates in second pattern for power supply changeover device among Fig. 2;

Inductive current IL and switching sequence on the inductance L when Fig. 6 operates in second pattern for power supply changeover device among Fig. 2;

Signal waveform when Fig. 7 operates in three-mode for power supply changeover device among Fig. 2;

Inductive current IL and switching sequence on the inductance L when Fig. 8 operates in three-mode for power supply changeover device among Fig. 2;

Signal waveform when Fig. 9 operates in four-mode for power supply changeover device among Fig. 2;

Inductive current IL and switching sequence on the inductance L when Figure 10 operates in four-mode for power supply changeover device among Fig. 2;

Figure 11 is the mode switch figure of power supply changeover device among Fig. 2;

Figure 12 is the embodiment schematic diagram of control logic circuit among Fig. 2;

Figure 13 is a second embodiment of the present invention schematic diagram;

Figure 14 is a third embodiment of the present invention schematic diagram;

Figure 15 is a fourth embodiment of the present invention schematic diagram;

Figure 16 is the embodiment schematic diagram of mode detector.

Among the figure, 10, power supply changeover device 12, power stage 14, control circuit 16, control logic circuit 18, comparator 20, comparator 22, sawtooth generator 24, error amplifier 30, power supply changeover device 32, power stage 34, control circuit 36, control logic circuit 3602, D type flip-flop 3604, logical circuit 3606, multiplexer 3608, logical circuit 3610, multiplexer 38, mode detector 3802, current source 3804, operational amplifier 3806, current source 3808, comparator 3810, comparator 3812, comparator 40, comparator 42, comparator 44, sawtooth generator 46, error amplifier 48, frequency generator 50, the waveform 52 of sawtooth signal SAW12, the waveform 54 of error signal VEA, the waveform 56 of signal PWM1, the waveform 58 of frequency Clk_buck, the waveform 60 of frequency Clk_boost, the waveform 62 of control signal VA, the waveform 64 of control signal VB, the waveform 66 of control signal VC, the waveform 68 of control signal VD, the waveform 70 of sawtooth signal SAW12, the waveform 72 of error signal VEA, the waveform 74 of signal PWM1, the waveform 76 of frequency Clk_buck, the waveform 78 of frequency Clk_boost, the waveform 80 of control signal VA, the waveform 82 of control signal VB, the waveform 84 of control signal VC, the waveform 86 of control signal VD, the waveform 88 of sawtooth signal SAW34, the waveform 90 of error signal VEA, the waveform 92 of signal PWM2, the waveform 94 of frequency Clk_buck, the waveform 96 of frequency Clk_boost, the waveform 98 of control signal VA, the waveform 100 of control signal VB, the waveform 102 of control signal VC, the waveform 104 of control signal VD, the waveform 106 of sawtooth signal SAW34, the waveform 108 of error signal VEA, the waveform 110 of signal PWM2, the waveform 112 of frequency Clk_buck, the waveform 114 of frequency Clk_boost, the waveform 116 of control signal VA, the waveform 118 of control signal VB, the waveform 120 of control signal VC, the waveform 130 of control signal VD, power supply changeover device 132, power stage 140, power supply changeover device 142, power stage 150, power supply changeover device 152, power stage.

Embodiment

Below in conjunction with embodiment and accompanying drawing thereof the present invention is illustrated further.

Now see also Fig. 2, Fig. 2 shows the first embodiment of the present invention.As shown in the figure, described in step-down/up type power supply changeover device 30, control circuit 34 output control signal VA, VB, VC and VD driving power level 32, input voltage vin is converted to output voltage V out, resistance R 1 and R2 pressure-dividing output voltage Vout produce feedback signal VFB and give control circuit 34.In power stage 32, switch SW 1 is connected between input voltage vin and the inductance L, and switch SW 2 is connected between inductance L and the earth terminal GND, and switch SW 3 is connected between inductance L and the earth terminal GND, and switch SW 4 is connected between inductance L and the output voltage V out.Because the responsibility cycle of whole system is not only relevant with input voltage and output voltage, load current also can influence the size of responsibility cycle, so the switching point of pattern also must be taken into account the factor of load current.In control circuit 34, mode detector 38 detects input voltage vin, output voltage V out and load current Iload produce mode select signal S[3:0] to determine the operator scheme of power supply changeover device 30, error amplifier 46 produces error signal VEA according to reference voltage Vref and feedback signal VFB, frequency generator 48 provides frequency Clk_boost and Clk_buck, frequency Clk_boost and Clk_buck have fixing period T s and fixing responsibility cycle, sawtooth generator 44 is according to frequency Clk_boost and mode select signal S[3:0] sawtooth signal SAW12 and SAW34 be provided, comparator 40 comparison error signal VEA and sawtooth signal SAW12 produce signal PWM1, comparator 42 comparison error signal VEA and sawtooth signal SAW34 produce signal PWM2, and control logic circuit 36 is according to signal PWM1 and PWM2, mode select signal S[3:0] and frequency Clk_boost and Clk_buck generation control signal VA, VB, VC and VD diverter switch SW1, SW2, SW3 and SW4 are to be converted to input voltage vin output voltage V out.

Described power supply changeover device 30 may operate in four kinds of patterns, and when the multiplier value at the inductance two ends that input voltage vin, output voltage V out and load current Iload are determined during less than first critical value, power supply changeover device 30 operates in first pattern.Signal waveform when Fig. 3 display power supply transducer 30 operates in first pattern, wherein waveform 50 is sawtooth signal SAW12, waveform 52 is error signal VEA, waveform 54 is signal PWM1, and waveform 56 is frequency Clk_buck, and waveform 58 is frequency Clk_boost, waveform 60 is control signal VA, waveform 62 is control signal VB, and waveform 64 is control signal VC, and waveform 66 is control signal VD.Inductive current IL and switching sequence on the inductance L when Fig. 4 display power supply transducer 30 operates in first pattern.First pattern is simple decompression mode, at time t1 to t2, control signal VA, VB, VC and VD are low level, shown in waveform 60,62,64 and 66, because switch SW 1 and SW4 are PMOS and switch SW 2 and SW3 are NMOS, switch SW 2 and SW3 close (turn off) so switch SW 1 and SW4 open (turn on), be defined as tAD1 during this period of time, in time tAD1, charging makes inductive current IL rise to input voltage vin to inductance L, as shown in Figure 4.At time t2 to t3, control signal VA and VB are high levle and control signal VC and VD are low level, and switch SW 1 and SW3 close so switch SW 2 and SW4 open, and this time is defined as tBD1, and in time tBD1, the inductance L discharge makes inductive current IL descend.In first pattern, the cycle of the switching cycle of switch SW 1 and SW2 and inductive current IL is Ts, and the step-down responsibility cycle is the responsibility cycle ratio of switch SW 1 than Kbuck1.

When the multiplier value at the inductance two ends that input voltage vin, output voltage V out and load current Iload are determined greater than first critical value and less than 1 the time, power supply changeover device 30 operates in second pattern.Signal waveform when Fig. 5 display power supply transducer 30 operates in second pattern, wherein waveform 68 is sawtooth signal SAW12, waveform 70 is error signal VEA, waveform 72 is signal PWM1, and waveform 74 is frequency Clk_buck, and waveform 76 is frequency Clk_boost, waveform 78 is control signal VA, waveform 80 is control signal VB, and waveform 82 is control signal VC, and waveform 84 is control signal VD.Inductive current IL and switching sequence when Fig. 6 display power supply transducer 30 operates in second pattern.Second pattern is the buck pattern, at time t4 to t5, control signal VA and VB are high levle and control signal VC and VD are low level, switch SW 2 and SW4 open so switch SW 1 and SW3 close, be defined as tBD2 during this period of time, at time t5 to t6, control signal VA, VB, VC and VD are low level, switch SW 2 and SW3 close so switch SW 1 and SW4 open, be defined as tAD2 during this period of time, at time t6 to t7, control signal A and B are low level and control signal C and D are high levle, switch SW 2 and SW4 close so switch SW 1 and SW3 open, and are defined as tAC1 during this period of time.In second pattern, the cycle of the switching cycle of switch SW 1, SW2, SW3 and SW4 and inductive current IL is 2Ts.With reference to Fig. 6, each cycle of inductive current IL comprises step-down and boost operations, in second pattern, the responsibility cycle of switch SW 3 and SW4 is determined by frequency Clk_boost, so switch SW 3 and SW4 have fixing responsibility cycle, therefore, the responsibility cycle of boosting during boost operations is fixed than Kboost1, can allow output voltage V out stable by the step-down responsibility cycle that is adjusted at during the reduced pressure operation than Kbuck2.

When the multiplier value at the inductance two ends that input voltage vin, output voltage V out and load current Iload are determined less than second critical value and greater than 1 the time, power supply changeover device 30 operates in three-mode.Signal waveform when Fig. 7 display power supply transducer 30 operates in three-mode, wherein waveform 86 is sawtooth signal SAW34, waveform 88 is error signal VEA, waveform 90 is signal PWM2, and waveform 92 is frequency Clk_buck, and waveform 94 is frequency Clk_boost, waveform 96 is control signal VA, waveform 98 is control signal VB, and waveform 100 is control signal VC, and waveform 102 is control signal VD.Inductive current IL and switching sequence when Fig. 8 display power supply transducer 30 operates in three-mode.Three-mode is the buck pattern, at time t8 to t9, control signal VA and VB are high levle and control signal VC and VD are low level, switch SW 2 and SW4 open so switch SW 1 and SW3 close, be defined as tBD3 during this period of time, at time t9 to t10, control signal VA, VB, VC and VD are low level, switch SW 2 and SW3 close so switch SW 1 and SW4 open, be defined as tAD3 during this period of time, at time t10 to t11, control signal A and B are low level and control signal C and D are high levle, switch SW 2 and SW4 close so switch SW 1 and SW3 open, and are defined as tAC2 during this period of time.In three-mode, the cycle of the switching cycle of switch SW 1, SW2, SW3 and SW4 and inductive current IL is 2Ts.With reference to Fig. 8, each cycle of inductive current IL comprises step-down and boost operations, in three-mode, the responsibility cycle of switch SW 1 and SW2 is determined by frequency Clk_buck, so the responsibility cycle of switch SW 1 and SW2 is fixed, therefore, the step-down responsibility cycle during reduced pressure operation is fixed than Kbuck3, can allow output voltage V out stable by the responsibility cycle of boosting that is adjusted at during the boost operations than Kboost2.

When the multiplier value at the inductance two ends that input voltage vin, output voltage V ou and load current Iload are determined greater than second critical value, power supply changeover device 30 operates in four-mode.The signal waveform of Fig. 9 display power supply transducer 30 behaviour's parts when four-mode, wherein waveform 104 is sawtooth signal SAW34, waveform 106 is error signal VEA, waveform 108 is signal PWM2, and waveform 110 is frequency Clk_buck, and waveform 112 is frequency Clk_boost, waveform 114 is control signal VA, waveform 116 is control signal VB, and waveform 118 is control signal VC, and waveform 120 is control signal VD.Inductive current IL and switching sequence when Figure 10 display power supply transducer 30 operates in four-mode.Four-mode is simple boost mode, at time t12 to t13, control signal VA and VB are low level and control signal VC and VD are high levle, switch SW 2 and SW4 close so switch SW 1 and SW3 open, be defined as tAC3 during this period of time, at time t13 to t14, control signal VA, VB, VC and VD are low level, switch SW 2 and SW3 close so switch SW 1 and SW4 open, and are defined as tAD4 during this period of time.In four-mode, the cycle of the switching cycle of switch SW 3 and SW4 and inductive current IL is Ts, and the responsibility cycle of boosting is the responsibility cycle ratio of switch SW 3 than Kboost3.

When power supply changeover device 30 operates in the buck pattern, the transfer sequence of switch is opened switch SW 2 and SW4 and off switch SW1 and SW3 for (1), (2) open switch SW 1 and SW4 and off switch SW2 and SW3, (3) open switch SW 1 and SW3 and off switch SW2 and SW4, compare with known techniques, in the circulation of identical time, the switch switching times of power supply changeover device 30 is less, and when the operator scheme of power supply changeover device 30 enters the buck pattern by decompression mode or boost mode, the switching cycle of switch will be extended for 2Ts by Ts, so can reduce switch cost.Moreover the duration that this new switching sequence can allow inductance L be connected with the output end vo ut of power supply changeover device 30 prolongs, so can reduce the conducting loss.

Utilize weber balance (voltage second balance) principle can derive relation between input voltage vin, output voltage V out and the load current Iload of power supply changeover device 30 under four kinds of patterns.With reference to Fig. 4, suppose that the cross-pressure on each switch SW 1, SW2, SW3 and the SW4 all is Vsw, when transducer operated in first pattern, the pass between the cross-pressure Vsw of input voltage vin, output voltage V out and switch was

Vin-2Vsw/ (tAD1/Ts)=Vout/ (tAD1/Ts) formula 1

With reference to Fig. 6, when second pattern, the pass between the cross-pressure Vsw of input voltage vin, output voltage V out and switch is

Vin-4Vsw/(Ts+tAD2_1)

＝Vout[(Ts+tAD2_2)/(Ts+tAD2_1)]

=Vout[(2-Kboost1) Ts/ (Ts+tAD2_1)] formula 2

With reference to Fig. 8, when three-mode, the pass between the cross-pressure Vsw of input voltage vin, output voltage V out and switch is

Vin-4Vsw/(Ts+tAD3_1)

＝Vout[(Ts+tAD3_2)/(Ts+tAD3_1)]

=Vout[(Ts+tAD3_2)/(1+Kbuck3) Ts] formula 3

With reference to Figure 10, when four-mode, the pass between the cross-pressure Vsw of input voltage vin, output voltage V out and switch is

Vin-2Vsw=Vout (1-tAC3/Ts) formula 4

For the nonlinear problem that prevents sawtooth signal SAW12 and SAW34 makes output voltage V out to stablize, be respectively K1 and K2 so limit the maximum liability cycle of step-down and the minimum responsibility cycle of boosting, so that input voltage vin near or when equaling output voltage V out, can allow output voltage V out stable.The mode switch figure of Figure 11 display power supply transducer 30 is from formula 1 to formula 4 and the critical value K1 that sets and the K2 mode switch that can obtain power supply changeover device 30.When power supply changeover device 30 operates in first pattern,,, input voltage vin makes that power supply changeover device 30 switched to second pattern when multiplier value at inductance L two ends equaled critical value A1 if continuing decline with reference to Figure 11.When power supply changeover device 30 operates in second pattern,,, input voltage vin makes that power supply changeover device 30 switched to three-mode when the multiplier value at inductance L two ends equaled critical value A2 if continuing decline with reference to Figure 11.When power supply changeover device 30 operates in three-mode,,, input voltage vin makes that power supply changeover device 30 switched to four-mode when the multiplier value at inductance L two ends equaled critical value A3 if continuing decline with reference to Figure 11.When power supply changeover device 30 operates in four-mode,,, input voltage vin makes that power supply changeover device 30 switched to three-mode when the multiplier value at inductance L two ends equaled critical value A3 if continuing rising with reference to Figure 11 and formula 4.When power supply changeover device 30 operates in three-mode,, input voltage vin makes that power supply changeover device 30 switched to second pattern when multiplier value at inductance L two ends equaled critical value A2 if continuing rising.When power supply changeover device 30 operated in second pattern, if input voltage vin continue to rise, power supply changeover device 30 switched to first pattern when making the multiplier value of inductance two ends L equal critical value A1.

The embodiment of control logic circuit 36 in Figure 12 displayed map 2, wherein D type flip-flop 3602 as frequency eliminator in order to frequency Clk_boost frequency elimination is produced frequency CLK2 and CLK2B, logical circuit 3604 is according to signal PWM1, frequency Clk_boost, the current potential of CLK2 and Clk_buck and earth terminal GND produces control signal S1, S2, S3 and S4, multiplexer 3606 is according to mode select signal S[3:0] from control signal S4, S3, choose one of them among S2 and the S1 as control signal VA and VB, logical circuit 3608 is according to the current potential of earth terminal GND, frequency CLK2B and Clk_boost and signal PWM2 produce control signal S5, S6, S7 and S8, multiplexer 3610 is according to mode select signal S[3:0] from control signal S8, S7, choose one of them among S6 and the S5 as control signal VC and VD.

Figure 13 shows the second embodiment of the present invention, in step-down/up type power supply changeover device 130, control circuit 34 driving power levels 132 are to be converted to input voltage vin output voltage V out, and resistance R 1 and R2 pressure-dividing output voltage Vout produce feedback signal VFB and give control circuit 34.In power stage 132, switch SW 1 is connected between input voltage vin and the inductance L, and switch SW 2 is connected between inductance L and the earth terminal GND, and switch SW 3 is connected between inductance L and the earth terminal GND, and diode D1 is connected between inductance L and the output voltage V out.Control circuit 34 comprises control logic circuit 36, mode detector 38,

comparator

40 and 42, sawtooth generator 44, error amplifier 46 and frequency generator 48 equally, and control logic circuit 36 is according to signal PWM1 and PWM2, mode select signal S[3:0] and frequency Clk_boost and Clk_buck produce control signal VA, VB and VC diverter switch SW1, SW2 and SW3 input voltage vin is converted to output voltage V out.

When power supply changeover device 130 operates in the buck pattern, the transfer sequence of its switch is opened switch SW 2 and off switch SW1 and SW3 for (1), (2) open switch SW 1 and off switch SW2 and SW3, (3) open switch SW 1 and SW3 and off switch SW2, repeating step (1) is to (3) afterwards, wherein, work as input voltage vin, the responsibility cycle that output voltage V out and load current Iload are determined is greater than first critical value and less than 1, the responsibility cycle of switch SW 3 is fixed, work as input voltage vin, the responsibility cycle that output voltage V out and load current Iload are determined is less than second critical value and greater than 1, the responsibility cycle of switch SW 1 and SW2 is fixed, and when the operator scheme of power supply changeover device 130 enters the buck pattern by decompression mode or boost mode, the switching cycle of switch will be extended for 2Ts by Ts.

Figure 14 shows the third embodiment of the present invention, in step-down/up type power supply changeover device 140, control circuit 34 driving power levels 142 are to be converted to input voltage vin output voltage V out, and resistance R 1 and R2 pressure-dividing output voltage Vout produce feedback signal VFB and give control circuit 34.In power stage 142, switch SW 1 is connected between input voltage vin and the inductance L, and diode D2 is connected between inductance L and the earth terminal GND, and switch SW 3 is connected between inductance L and the earth terminal GND, and switch SW 4 is connected between inductance L and the output voltage V out.Control circuit 34 isotype control logic circuit 36, mode detector 38,

comparator

40 and 42, sawtooth generator 44, error amplifier 46 and the frequency generators 48 of comprising, control logic circuit 36 is according to signal PWM1 and PWM2, mode select signal S[3:0] and frequency Clk_boost and Clk_buck produce control signal VA, VC and VD diverter switch SW1, SW3 and SW4 input voltage vin is converted to output voltage V out.

When power supply changeover device 140 operates in the buck pattern, the transfer sequence of its switch is opened switch SW 4 and off switch SW1 and SW3 for (1), (2) open switch SW 1 and SW4 and off switch SW3, (3) open switch SW 1 and SW3 and off switch SW4, repeating step (1) is to (3) afterwards, wherein, work as input voltage vin, the responsibility cycle that output voltage V out and load current Iload are determined is greater than first critical value and less than 1, the responsibility cycle of switch SW 3 and SW4 is fixed, work as input voltage vin, the responsibility cycle that output voltage V out and load current Iload are determined is less than second critical value and greater than 1, the responsibility cycle of switch SW 1 is fixed, and when the operator scheme of power supply changeover device 140 enters the buck pattern by decompression mode or boost mode, the switching cycle of switch will be extended for 2Ts by Ts.

Figure 15 shows the fourth embodiment of the present invention, in step-down/up type power supply changeover device 150, control circuit 34 driving power levels 152 are to be converted to input voltage vin output voltage V out, and resistance R 1 and R2 pressure-dividing output voltage Vout produce feedback signal VFB and give control circuit 34.In power stage 152, switch SW 1 is connected between input voltage vin and the inductance L, and diode D3 is connected between inductance L and the earth terminal GND, and switch SW 3 is connected between inductance L and the earth terminal GND, and diode D4 is connected between inductance L and the output voltage V out.Control circuit 34 isotype control logic circuit 36, mode detector 38,

comparator

40 and 42, sawtooth generator 44, error amplifier 46 and the frequency generators 48 of comprising, control logic circuit 36 is according to signal PWM1 and PWM2, mode select signal S[3:0] and frequency Clk_boost and Clk_buck produce control signal VA and VC diverter switch SW1 and SW3 so that input voltage Vi n is converted to output voltage V out.

When power supply changeover device 150 operates in the buck pattern, the transfer sequence of its switch is (1) off switch SW1 and SW3, (2) open switch SW 1 and off switch SW3, (3) open switch SW 1 and SW3, repeating step (1) is to (3) afterwards, wherein, work as input voltage vin, the responsibility cycle that output voltage V out and load current Iload are determined is greater than first critical value and less than 1, the responsibility cycle of switch SW 3 is fixed, work as input voltage vin, the responsibility cycle that output voltage V out and load current Iload are determined is less than second critical value and greater than 1, the responsibility cycle of switch SW 1 is fixed, and when the operator scheme of power supply changeover device 150 enters the buck pattern by decompression mode or boost mode, the switching cycle of switch will be extended for 2Ts by Ts.

The embodiment of Figure 16 display mode detector 38, in mode detector 38, when switch SW 1 was opened, switch MP1 also opened simultaneously, so voltage Vb is (Vin-Vsw-Ib * R3), wherein voltage Vsw is directly proportional with load current Iload, operational amplifier 3804 is locked in voltage Vb and Va with on the position surely, and the electric current I a that therefore flows through resistance R 4 is (Ib+Vsw/R4), and design

current source

3802 and 3806 equates, make the flow through electric current I c of resistance R 5 be (Vsw/R4), therefore can push away voltage

VDEC＝Vin-Ia×R4-Ic×R5

＝Vin-Ib×R4-Vsw-(R5/R4)×Vsw

=Vin-(1+R5/R4) Vsw-Ib * R4 formula 5

Because (Ib's * R4) can design is relatively little, so voltage

Formula 6

By formula 6 as can be known, can regulation voltage VDEC by the ratio of adjusting resistance R 5 and R4, then

comparator

3808,3810 and 3812 compare respectively (M1 * Vout), (M2 * Vout) and (M3 * Vout) and voltage VDEC, logical circuit 3814 produces mode select signal S[3:0 according to the output of comparator 3808,3810 and 3812].

Above embodiment is only for the usefulness that the present invention is described, but not limitation of the present invention, person skilled in the relevant technique under the situation that does not break away from the spirit and scope of the present invention, can also be made various conversion or variation.Therefore, all technical schemes that are equal to also should belong to category of the present invention, should be limited by each claim.

Claims

1. the control method of a step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one second switch is connected between first end and an earth terminal of described inductance, one the 3rd switch is connected between second end and described earth terminal of described inductance, and one the 4th switch be connected between the output of second end of described inductance and described power supply changeover device, it is characterized in that described control method comprises the following steps:

2. control method as claimed in claim 1 is characterized in that, the step that the described power supply changeover device of described decision operates in decompression mode, the first buck pattern, the second buck pattern or boost mode comprises the following steps:

3. control method as claimed in claim 1 is characterized in that, more comprises:

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

4. control method as claimed in claim 1 is characterized in that, when described decompression mode, the switching cycle of described first and second switch is a period 1; When the described first buck pattern described first, second, third and the switching cycle of the 4th switch be a second round greater than the described period 1; When the described second buck pattern described first, second, third and the switching cycle of the 4th switch be a period 3 greater than the described period 1; When described boost mode the described the 3rd and the switching cycle of the 4th switch be a period 4 less than described second and third cycle.

5. control method as claimed in claim 1 is characterized in that, when the described first buck pattern, the described the 3rd and the responsibility cycle of the 4th switch fix.

6. control method as claimed in claim 1 is characterized in that, when the described second buck pattern, the responsibility cycle of described first and second switch is fixed.

7. a step-down/up type power supply changeover device is characterized in that, comprising:

One inductance;

8. power supply changeover device as claimed in claim 7, it is characterized in that, the multiplier value at the described inductance two ends that voltage and described load current determined of described control circuit on described input and output determines described power supply changeover device to operate in described decompression mode during less than one first critical value; The multiplier value at the described inductance two ends that voltage and described load current determined on described input and output determines described power supply changeover device to operate in the described first buck pattern during greater than described first critical value and less than one second critical value; The multiplier value at the described inductance two ends that voltage and described load current determined on described input and output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that voltage and load current determined on described input and output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

9. power supply changeover device as claimed in claim 7 is characterized in that, described control circuit comprises:

One frequency generator provides a first frequency and a second frequency;

10. power supply changeover device as claimed in claim 9 is characterized in that, described control logic circuit comprises:

11. power supply changeover device as claimed in claim 10 is characterized in that, described frequency eliminator comprises D type flip-flop.

12. power supply changeover device as claimed in claim 7 is characterized in that, when described decompression mode, the switching cycle of described first and second switch is a period 1; When the described first buck pattern described first, second, third and the switching cycle of the 4th switch be a second round greater than the described period 1; When the described second buck pattern described first, second, third and the switching cycle of the 4th switch be a period 3 greater than the described period 1; When described boost mode the described the 3rd and the switching cycle of the 4th switch be a period 4 less than described second and third cycle.

13. power supply changeover device as claimed in claim 7 is characterized in that, when the described first buck pattern, the described the 3rd and the responsibility cycle of the 4th switch fix.

14. power supply changeover device as claimed in claim 7 is characterized in that, when the described second buck pattern, the responsibility cycle of described first and second switch is fixed.

15. the control method of a step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one second switch is connected between first end and an earth terminal of described inductance, one the 3rd switch is connected between second end and described earth terminal of described inductance, and one diode have an anode and connect second end of described inductance and the output that a negative electrode connects described power supply changeover device, it is characterized in that described control method comprises the following steps:

16. control method as claimed in claim 15 is characterized in that, the step that the described power supply changeover device of described decision operates in decompression mode, the first buck pattern, the second buck pattern or boost mode comprises:

17. control method as claimed in claim 15 is characterized in that, more comprises:

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

18. control method as claimed in claim 15 is characterized in that, when described decompression mode, the switching cycle of described first and second switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described the 3rd switch is a period 4 less than described second and third cycle when described boost mode.

19. control method as claimed in claim 15 is characterized in that, when the described first buck pattern, the responsibility cycle of described the 3rd switch is fixed.

20. control method as claimed in claim 15 is characterized in that, when the described second buck pattern, the responsibility cycle of described first and second switch is fixed.

21. a step-down/up type power supply changeover device is characterized in that, comprising:

One inductance;

22. power supply changeover device as claimed in claim 21, it is characterized in that, voltage and the multiplier value at described inductance two ends that load current determined described output on during less than one first critical value of control circuit on described input and output determines described power supply changeover device to operate in described decompression mode; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described first buck pattern during greater than described first critical value and less than one second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

23. power supply changeover device as claimed in claim 21 is characterized in that, described control circuit comprises:

One frequency generator provides a first frequency and a second frequency;

24. power supply changeover device as claimed in claim 23 is characterized in that, described control logic circuit comprises:

25. power supply changeover device as claimed in claim 24 is characterized in that, described frequency eliminator comprises D type flip-flop.

26. power supply changeover device as claimed in claim 21 is characterized in that, when described decompression mode, the switching cycle of described first and second switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described the 3rd switch is a period 4 less than described second and third cycle when described boost mode.

27. power supply changeover device as claimed in claim 21 is characterized in that, when the described first buck pattern, the responsibility cycle of described the 3rd switch is fixed.

28. power supply changeover device as claimed in claim 21 is characterized in that, when the described second buck pattern, the responsibility cycle of described first and second switch is fixed.

29. the control method of a step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one diode has an anode and connects first end that an earth terminal and a negative electrode connect described inductance, one second switch is connected between second end and described earth terminal of described inductance, and one the 3rd switch be connected between the output of second end of described inductance and described power supply changeover device, it is characterized in that described control method comprises the following steps:

30. control method as claimed in claim 29 is characterized in that, the step that the described power supply changeover device of described decision operates in decompression mode, the first buck pattern, the second buck pattern or boost mode comprises:

31. control method as claimed in claim 29 is characterized in that, more comprises:

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

32. control method as claimed in claim 29 is characterized in that, when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second and third switch is a period 4 less than described second and third cycle when described boost mode.

33. control method as claimed in claim 29 is characterized in that, when the described first buck pattern, the responsibility cycle of described second and third switch is fixed.

34. control method as claimed in claim 29 is characterized in that, when the described second buck pattern, the responsibility cycle of described first switch is fixed.

35. a step-down/up type power supply changeover device is characterized in that, comprising:

One inductance;

36. power supply changeover device as claimed in claim 35, it is characterized in that, voltage and the multiplier value at described inductance two ends that load current determined described output on during less than one first critical value of described control circuit on described input and output determines described power supply changeover device to operate in described decompression mode; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described first buck pattern during greater than one first critical value and less than one second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

37. power supply changeover device as claimed in claim 35 is characterized in that, described control circuit comprises:

One frequency generator provides a first frequency and a second frequency;

38. power supply changeover device as claimed in claim 37 is characterized in that, described control logic circuit comprises:

39. power supply changeover device as claimed in claim 38 is characterized in that, described frequency eliminator comprises D type flip-flop.

40. power supply changeover device as claimed in claim 35 is characterized in that, when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first, second and third switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first, second and third switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second and third switch is a period 4 less than described second and third cycle when described boost mode.

41. power supply changeover device as claimed in claim 35 is characterized in that, when the described first buck pattern, the responsibility cycle of described second and third switch is fixed.

42. power supply changeover device as claimed in claim 35 is characterized in that, when the described second buck pattern, the responsibility cycle of described first switch is fixed.

43. the control method of a step-down/up type power supply changeover device, described power supply changeover device comprises an inductance, one first switch is connected between first end of the input of described power supply changeover device and described inductance, one first diode has an anode and connects first end that an earth terminal and a negative electrode connect described inductance, one second switch is connected between second end and described earth terminal of described inductance, and one second diode have an anode and connect second end of described inductance and the output that a negative electrode connects described power supply changeover device, it is characterized in that described control method comprises the following steps:

(a) close described first switch, close described second switch;

(b) open described first switch, keep described second switch and close;

(c) keep described first switch opens, open described second switch.

44. control method as claimed in claim 43 is characterized in that, the step that the described power supply changeover device of described decision operates in decompression mode, the first buck pattern, the second buck pattern or boost mode comprises:

45. control method as claimed in claim 43 is characterized in that, more comprises:

One first frequency and a second frequency are provided;

More described secondary signal and the 3rd signal produce one the 5th signal;

More described secondary signal and the 4th signal produce one the 6th signal;

46. control method as claimed in claim 43 is characterized in that, when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first and second switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first and second switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second switch is a period 4 less than described second and third cycle when described boost mode.

47. control method as claimed in claim 43 is characterized in that, when the described first buck pattern, the responsibility cycle of described second switch is fixed.

48. control method as claimed in claim 43 is characterized in that, when the described second buck pattern, the responsibility cycle of described first switch is fixed.

49. a step-down/up type power supply changeover device is characterized in that, comprising:

One inductance;

50. power supply changeover device as claimed in claim 49, it is characterized in that, described control circuit determines described power supply changeover device to operate in described decompression mode when the multiplier value at the described inductance two ends that load current determined on voltage on described input and the output and the described output during less than one first critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described first buck pattern during greater than described first critical value and less than one second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in the described second buck pattern during less than one the 3rd critical value and greater than described second critical value; The multiplier value at the described inductance two ends that load current determined on voltage on described input and output and the described output determines described power supply changeover device to operate in described boost mode during greater than described the 3rd critical value.

51. power supply changeover device as claimed in claim 49 is characterized in that, described control circuit comprises:

One frequency generator provides a first frequency and a second frequency;

52. power supply changeover device as claimed in claim 51 is characterized in that, described control logic circuit comprises:

53. power supply changeover device as claimed in claim 52 is characterized in that, described frequency eliminator comprises D type flip-flop.

54. power supply changeover device as claimed in claim 49 is characterized in that, when described decompression mode, the switching cycle of described first switch is a period 1; The switching cycle of described first and second switch is a second round greater than the described period 1 when the described first buck pattern; The switching cycle of described first and second switch is a period 3 greater than the described period 1 when the described second buck pattern; The switching cycle of described second switch is a period 4 less than described second and third cycle when described boost mode.

55. power supply changeover device as claimed in claim 49 is characterized in that, when the described first buck pattern, the responsibility cycle of described second switch is fixed.

56. power supply changeover device as claimed in claim 49 is characterized in that, when the described second buck pattern, the responsibility cycle of described first switch is fixed.