CN114977740A - DCM control circuit with high dynamic response and high precision and control method thereof - Google Patents

DCM control circuit with high dynamic response and high precision and control method thereof Download PDF

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Publication number
CN114977740A
CN114977740A CN202210542717.3A CN202210542717A CN114977740A CN 114977740 A CN114977740 A CN 114977740A CN 202210542717 A CN202210542717 A CN 202210542717A CN 114977740 A CN114977740 A CN 114977740A
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circuit
signal
control
error
main power
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周宗杰
许超群
喻辉洁
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Xiamen Biyi Micro Electronic Technique Co ltd
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Xiamen Biyi Micro Electronic Technique Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00—Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01—Frequency selective two-port networks
    • H03H7/06—Frequency selective two-port networks including resistors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K7/00—Modulating pulses with a continuously-variable modulating signal
    • H03K7/08—Duration or width modulation ; Duty cycle modulation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention provides a DCM control circuit with high dynamic response and high precision, which is used for controlling the voltage stabilization output of a main power circuit, and comprises: the error elimination circuit generates a second voltage reference signal according to the error control signal and the first voltage reference signal so as to eliminate the control error of the loop compensation circuit; the loop compensation circuit generates an error control signal according to the second voltage reference signal and a voltage feedback signal of the main power circuit; and the switch control circuit controls the main power switch tube based on the error control signal so as to control the circuit output voltage of the main power. The control circuit of the DC-DC converter provided by the invention has the advantages of small circuit area, effective reduction of complexity and cost, simplification of the control circuit of the system, reduction of the circuit area, high dynamic response and guarantee of high-stability and high-precision output of the control circuit.

Description

DCM control circuit with high dynamic response and high precision and control method thereof
Technical Field
The invention relates to the field of electronics, in particular to a control circuit and a control method of a DC-DC converter and the DC-DC converter.
Background
The DC-DC power supply is widely applied to the fields of electronic equipment such as modern household appliances, consumer appliances, industry appliances and the like. The application of the power switch tube combined with the loop compensation circuit is a common design mode of a low-voltage low-power DCDC power supply. Such application fields generally require that the DCDC dc converter have a sufficiently fast dynamic response and meet a certain required output voltage accuracy. In order to improve the dynamic response, a peak current control mode is generally adopted, as shown in fig. 1, that is, a peak current I is adopted L Sampling and output voltage feedback V FB In the dual closed-loop control mode, the current control inner loop 1 usually needs a more complex slope compensator to suppress subharmonic oscillation, and the signal compensation of the output voltage feedback outer loop 2 needs a capacitor with larger capacitance, i.e. a large-capacity on-chip compensation capacitor, such on-chip compensation capacitor used as loop compensation needs to occupy larger silicon chip area in the IC design.
In the prior art, the On-time control mode is adopted to replace the peak current control mode by adopting a COT (constant On time) mode. Compared with a peak current control mode, the COT control mode improves the dynamic response of the output voltage and reduces the volume of the output capacitor. However, the COT control scheme needs to solve the stability problem caused by low DCR output capacitance, and the COT control architecture uses the output of the reference comparator to trigger the timing pulse generator instead of using a clock with a fixed frequency, the frequency of the pulse occurrence is determined by the output load current, and in the continuous conduction mode with stable output requirement, the COT control operates at an approximately fixed frequency. However, in the process of the load current jumping from low to high, the timing pulse generator of the COT outputs a high frequency pulse to reduce the output voltage drop to the maximum extent until the normal output voltage is reached, and the pulse frequency is reduced to the level required for maintaining stable regulation of the output voltage, so the COT control mode needs to additionally solve the problem of how to keep the frequency constant.
For low-cost auxiliary DCDC power supplies, these control schemes are very complicated, and the loop compensation circuit size does not decrease with decreasing power level.
Disclosure of Invention
In view of one or more problems of the prior art, it is an object of the present invention to provide a method for solving at least some of the above-mentioned drawbacks.
In at least one aspect, the present invention provides a control circuit for a DC-DC converter for controlling an output in a main power circuit, the control circuit comprising: the error elimination circuit generates a second voltage reference signal according to the error control signal and the first voltage reference signal so as to eliminate the control error of the loop compensation circuit; a loop compensation circuit that generates the error control signal based on the second voltage reference signal and a voltage feedback signal of the main power circuit; and the switch control circuit controls the main power switch tube based on the error control signal so as to control the circuit output voltage of the main power.
Further, the loop compensation circuit includes an amplification circuit having a first input terminal receiving the second voltage reference signal, a second input terminal receiving the voltage feedback signal, and an output terminal generating an error control signal.
Further, the amplifying circuit is a transconductance amplifying circuit, a first input end of the transconductance amplifying circuit is a non-inverting input end and receives the second voltage reference signal, a second input end of the transconductance amplifying circuit is an inverting input end and receives the voltage feedback signal, an output end of the transconductance amplifying circuit is coupled to the first resistor, and an output end of the transconductance amplifying circuit generates an error control signal having a positive relationship with the peak value of the current sampling signal.
Further, the gain value of the error cancellation circuit reflects the inverse of the product of the transconductance amplification circuit and the first resistance in the loop compensation circuit.
Furthermore, the conduction time of a main power switch tube of the main power circuit is the same as the variation trend of the error control signal.
Further, the switch control circuit comprises a comparison circuit and a trigger circuit, the comparison circuit is used for comparing the error control signal with the current sampling signal of the main power circuit to generate a trigger signal of a reset end of the trigger circuit so as to adjust the conduction time of the main power switch tube, and a set end of the comparison circuit receives a clock signal.
Further, the error cancellation circuit includes: a gain circuit for performing gain control on the error control signal to generate a gain; the adder adds the error control signal or the gain signal of the error control signal and the first voltage reference signal to generate the second voltage reference signal;
further, the error cancellation circuit further includes: and the filter is used for filtering the error control signal at low frequency.
Furthermore, the filter is a switched capacitor filter, and the on or off of at least one switching tube in the switched capacitor filter is adjusted according to a trigger signal in the reset end of the trigger circuit.
Furthermore, the adder is a four-input operational amplifier circuit, the first non-inverting input terminal receives the error control signal subjected to filtering and isolation processing, a second resistor is connected between the first non-inverting input terminal and the first inverting input terminal in a bridge manner and then grounded through a third resistor, the third non-inverting input terminal receives the first voltage reference signal Vref, and the fourth inverting input terminal is coupled to the output terminal of the adder and outputs a second voltage reference signal as an input signal of the non-inverting input terminal of the transconductance amplifier circuit.
In at least one other aspect, the present disclosure generally describes a direct current power supply circuit including the control circuit of the above DC-DC converter and a main power switch tube.
Further, the direct current power supply circuit operates in an interrupted current mode.
In at least another aspect, the present invention also provides a control method of a DC-DC converter, including: generating a second voltage reference signal for eliminating the control error of the loop compensation circuit according to the error control signal and the first voltage reference signal; and controlling a main power switch tube in the main power circuit according to the error control signal generated according to the second voltage reference signal and the voltage feedback signal of the main power circuit so as to control the output voltage of the main power circuit.
Further, the step of generating a second voltage reference signal for eliminating the control error of the loop compensation circuit according to the error control signal and the first voltage reference signal comprises: performing gain calculation on the error control signal to obtain a gain signal; and
and adding the gain signal and the first voltage reference signal to obtain a second voltage reference signal, or adding the error control signal and the first voltage reference signal and then obtaining the second voltage reference signal through gain calculation.
Further, the step of generating a second voltage reference signal for eliminating the control error of the loop compensation circuit according to the error control signal and the first voltage reference signal further comprises: the error control signal is low frequency filtered.
Furthermore, the error control signal is compared with the current sampling signal to generate a trigger signal connected to a reset end of the trigger circuit, so that the trigger circuit controls the conduction time of the main power switch tube to control the output voltage of the main power circuit.
In at least another aspect, the invention also provides a direct current voltage converter, which comprises at least part of the control circuit of the DC-DC converter, and is applied to the direct current voltage converter.
The control circuit of the DC-DC converter provided by the invention has the advantages that the circuit volume is smaller, the system complexity and the cost are effectively reduced, the control circuit of the system is simplified, the circuit volume is reduced, the control circuit has quick dynamic response, and the output voltage of the control circuit is ensured to be high in precision and stable within the set voltage error allowable range.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
fig. 1 is a schematic diagram of a peak current control mode circuit of the prior art.
Fig. 2 is a block diagram of a control circuit system of the DC-DC converter according to the first embodiment of the present invention.
Fig. 3 is a block diagram of a control circuit system of a DC-DC converter according to a second embodiment of the present invention.
Fig. 4 is a schematic diagram of a control circuit of a DC-DC converter according to a third embodiment of the present invention.
Fig. 5 is a schematic diagram of a control circuit of a DC-DC converter according to a fourth embodiment of the present invention.
FIG. 6 is a graph of the associated signal without the addition of an error cancellation circuit over time.
FIG. 7 is a graph of signals associated with a control system based on time for a possible embodiment of the present invention.
Detailed Description
In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present technology, and the present invention may be practiced without these specific details. It should be noted that structures and devices are shown in block diagram form in order to avoid obscuring the invention.
The description in this section is for several exemplary embodiments only and the invention is not to be limited in scope by the embodiments described. Reference herein to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in this specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
"coupled" in this specification includes direct connection and also includes indirect connection, such as connection through an electrically conductive medium, such as a conductor, where the electrically conductive medium may include parasitic inductance or parasitic capacitance. But also may include connections through other active or passive devices, such as through switches, follower circuits, etc., that are known to those skilled in the art for achieving the same or similar functional objectives.
In practical application of the low-voltage low-power direct-current power supply circuit, the load current is usually small, the output duty ratio is generally less than 50%, and the inductance of the main power circuitStream I L Is smaller, so that the inductance I L The influence of current ripple can be ignored, and the main power circuit can be simplified into a first-order system with poles formed by an output capacitor and a load. Even if the DC voltage converter works in an inductive current discontinuous mode (DCM), harmonic oscillation is not easy to generate, so that a complex slope compensation circuit is not needed. By adopting the proportional compensation mode, the system can obtain rapid dynamic response characteristics, a compensation capacitor in a loop compensation circuit can be omitted, a control circuit is simplified, and the circuit size is reduced.
The invention describes a control circuit and a method for a DC-DC converter, which are applied to the stability adjustment of an output voltage in a DC voltage converter, in particular to the voltage delivered to a load by a converter circuit in a DCM mode. The disclosed circuit and method can be used in different DC voltage conversion circuits, such as Buck, Boost, Buck-Boost, flyback, etc., as the main power circuit of the DC voltage converter.
The low-voltage low-power direct-current power supply of the circuit and the method disclosed by the invention provides a control circuit which is small in size and simplified in system. When the input or load changes, a control signal with quick dynamic response can be provided for the converter, and the voltage output by the direct-current voltage converter when the input or load changes is ensured to be stabilized within the set voltage error allowable range with high precision.
Fig. 2 is a block diagram of a control circuit system for a DC-DC converter according to a first embodiment of the present invention. As shown in fig. 2, the present embodiment is applied to a circuit system block diagram of a DC voltage converter for a DC-DC converter. In the present embodiment, the DCM control mode is used to control the output voltage value of the DC-DC converter. Control circuit 100 includes switch control circuit 20, loop compensation circuit 30, and error cancellation circuit 40 to control DCM main power circuit 10. The main power circuit 10 may be any one of different dc voltage converting circuits such as Buck, Boost, Buck-Boost, flyback, etc., and the main power circuit 10 includes at least one main power switching tube, where the main power switching tube may be a power switching tube such as MOS, IGBT, BJT, SiC, GaN, etc. The switching control circuit 20 controlling the main power switch tubeThe switch control circuit 20 comprises a trigger circuit and an amplifier circuit, the inverting input terminal of the amplifier circuit is coupled with the main power circuit, and receives the current sampling signal I of the main power circuit 10 L The non-inverting input terminal is coupled to an output of the loop compensation circuit 30, and receives the error control signal Vcomp generated by the loop compensation circuit 30. When the current samples the signal I L When the peak value reaches the amplitude of the error control signal Vcomp, the trigger circuit generates a signal for turning off the main power switch tube, the reset end R of the trigger circuit is coupled with the output of the amplifying circuit, and the set end S of the trigger circuit receives a clock signal CLK. The switch control circuit 20 controls the current feedback signal I of the main power circuit according to the error control signal Vcomp L And a clock signal CLK, which generates a control signal for driving the main power switch tube of the main power circuit 10 to turn on or off at its output terminal to control the on time of the main power switch tube and to control the output voltage Vout of the main power circuit 10, so that the output voltage Vout of the output voltage Vout is stabilized within the set voltage error allowable range with high precision.
The error cancellation circuit 40 comprises at least two input terminals, wherein one input terminal receives the first voltage reference signal Vref, and the other input terminal receives the error control signal Vcomp output by the loop compensation circuit 30, so that the output terminal of the error cancellation circuit 40 generates the second voltage reference signal Vref _ buf for canceling the control error of the loop compensation circuit 30. The loop compensation circuit 30 has an input coupled to the output of the error cancellation circuit 40 for receiving the second voltage reference signal Vref _ buf, and an input coupled to the output of the main power circuit 10 for receiving the voltage feedback signal V of the main power circuit 10 FB The error control signal Vcomp is generated at the output of the loop compensation circuit 30. According to the design of parameters in the error elimination circuit 40, the error control signal Vcomp is compensated based on the error between the error control signal Vcomp and the first voltage reference signal Vref, the response precision of the error control signal Vcomp is improved, the output voltage Vout of the main power circuit 10 can be controlled within a high-precision amplitude value, the system can obtain quick dynamic response when input change, load fluctuation or other disturbance is ensured, and the output voltage of the main power circuit 10 is stabilized at a set voltage error with high precisionWithin a certain range. The driving signal for driving the main power switch tube to be turned on or off is generated by a trigger circuit, the control signal of the trigger circuit includes a clock CLK signal with a fixed frequency, and the main power circuit 10 can operate in a frequency constant mode without additional adjustment of frequency constant. The on-time of the main power switch of the main power circuit 10 is the same as the variation trend of the error control signal Vcomp. Such as voltage feedback signal V of main power circuit 10 FB When the voltage drop is reduced, the error control signal Vcomp output by the error cancellation circuit 40 is configured to increase, and the on time of the main power switch tube becomes longer following the increase of the error control signal Vcomp, so that the output voltage Vout of the main power circuit is restored to the range allowed by the set voltage error.
Fig. 3 is a block diagram of a control circuit system of a DC-DC converter according to a second embodiment of the present invention. The second embodiment is one of the first embodiments, but is not limited to this embodiment.
In the control circuit 200 of fig. 3, the loop compensation circuit 40 comprises an amplifying circuit, a first input terminal of the amplifying circuit receives the second voltage reference signal Vref _ buf, and a second input terminal of the amplifying circuit receives the voltage feedback signal V FB The output end generates the current sampling signal I L Is positive-going with respect to the peak value of the error control signal Vcomp.
The amplifying circuit is a transconductance amplifying circuit 31, a first input terminal of which is a non-inverting input terminal and receives the second voltage reference signal Vref _ buf, and a second input terminal of which is an inverting input terminal and receives a voltage feedback signal V FB The output end of the transconductance amplifying circuit is coupled with the first resistor R and then grounded. The current amplified at the output terminal of the transconductance amplifying circuit 31 passes through the first resistor R to generate the error control signal Vcomp having a positive relationship with the peak value of the current sampling signal. The transconductance amplifying circuit can realize signal subtraction operation through a simple structure, so that the control circuit is simple. Further, the loop compensation circuit may be formed by other subtraction circuits and gain circuits, and is not limited to the above-mentioned exemplary range.
Further, the error control signal Vcomp is calculated by the following formula:
V comp ＝(V ref_buf -V FB )·G m ·R
in the above formula, Gm represents the transconductance of the transconductance amplifier circuit. That is to say that the first and second electrodes,
Figure BDA0003650905270000061
from the above formula, when the second voltage reference signal Vref _ buf is a fixed value, the voltage feedback signal V FB Depends on Vcomp/GmR. And the main power circuit is a pole first-order system consisting of an output capacitor and a load, and the instability problem does not exist. In order to quickly restore the output voltage Vout of the main power circuit to within a certain amplitude during input changes, load fluctuations or other disturbances, i.e. a voltage feedback signal V varying synchronously with the output voltage FB When the voltage returns to be slightly less than the second voltage reference signal Vref _ buf, Gm × R needs to be large enough to counteract the change of Vcomp. In the embodiment, the dynamic response speed of the system is high, the circuit system is in a relatively excellent response speed state, the main power circuit is applied to the small-power-tube direct-current converter, the influence of ripples can be ignored, the main power circuit is controlled by the inductor current discontinuous mode DCM without additionally increasing slope compensation, the control circuit is simplified, and the circuit area is reduced. However, in an actual circuit, Gm × R cannot take an infinite value, and therefore, there is always an error when no compensation is performed.
Fig. 6 shows a time-based plot of the associated signal without the addition of an error cancellation circuit. As shown in the figure, the main power converter adopts a DCM mode to realize peak current control, and controls the conduction time of a main power switch tube M through an error control signal Vcomp. Current sampling signal I of main power circuit when input or load is in steady state L And the error control signal Vcomp is stabilized in a specific amplitude value and is unchanged, the trigger circuit generates a PWM control signal with specific frequency under the control of a fixed clock signal CLK which is respectively input at a set end S and a reset end R and an output signal of the amplifying circuit, and the main power switch tube M is switched on or switched off under the control of the PWM control signal. Instantaneous moment of loadWhen the voltage increases, the output voltage Vout of the main power circuit decreases, and the voltage feedback signal V FB Following the decrease, the voltage feedback signal V FB Generates a follow voltage feedback signal V through the operation of the loop compensation circuit 30 FB The error control signal Vcomp is decreased while synchronously increased. As the amplitude of the error control signal Vcomp rises, the PWM control signal T is generated ON The time of the main power switch tube M is prolonged, and the on-time of the main power switch tube M is increased under the control of the PWM control signal. The loop compensation circuit 30 alone cannot make the voltage feedback signal V FB The amplitude returns to the original amplitude and the larger the load, the larger the difference. It can be seen that a fast dynamic response control signal can be obtained without compensation, but there is always a steady state error.
To eliminate this steady state control error, the present invention introduces an error cancellation circuit 40.
Further, the error cancellation circuit 30 includes an adder 42, a gain circuit 41, and a filter 43, and the error cancellation circuit 30 superimposes the error control signal Vcomp and the first voltage reference signal Vref to generate the second voltage reference signal Vref _ buf. The expression of the technical scheme is as follows:
V ref_buf ＝V ref +K·V comp
by combining the above two calculation formulas,
Figure BDA0003650905270000071
in the above equation, K represents the gain of the gain circuit 41 of the error cancel circuit 30.
It can be seen that when
Figure BDA0003650905270000072
Time, voltage feedback signal V FB The amplitude follows the amplitude variation of the first voltage reference signal Vref and is approximately equal, at which time the error control signal Vcomp is mostly eliminated or completely compensated, i.e. the control error of the error control signal Vcomp is mostly eliminated or completely eliminated. In practical application, the gain of the gain circuit in the error elimination circuit and the transconductance in the loop compensation circuit are amplifiedWhen the product reciprocal of the transconductance Gm of the circuit 131 is equal to the product reciprocal of the first resistor R1, since the design of system parameters cannot be precisely controlled, in the positive feedback circuit, when the product reciprocal of the gain K of the gain circuit is equal to the product reciprocal of the transconductance Gm and the first resistor R1, the positive feedback is easily over-compensated and unstable due to the influence of external factors or other interference, and therefore the gain value K of the error cancellation circuit 140 may be smaller or slightly smaller (that is, the gain value K is smaller than or close to that of the first resistor R1), so that the system is easily affected by the external factors or other interference, and the gain value K is unstable
Figure BDA0003650905270000073
) The inverse of the product of the transconductance Gm of the transconductance amplifying circuit 131 and the first resistance R in the loop compensation circuit, i.e. the inverse of the product of the transconductance Gm of the transconductance amplifying circuit and the first resistance in the loop compensation circuit is reflected by the gain value of the error cancellation circuit. Therefore, in the invention, by adopting a loop compensation mode in a DCM mode, the dynamic response speed of the system is high, the voltage output by the main power circuit when the input or the load changes can be stabilized within a set voltage error allowable range in high precision under the control of the error compensation circuit, and the accurate control of the output voltage can be realized without large capacitance compensation. And the main power circuit is applied to the small-power tube direct current converter, the influence of ripples can be ignored, the main power circuit is controlled by an inductive current discontinuous mode (DCM) without additionally increasing slope compensation, the control circuit is simplified, and the circuit volume is reduced.
Since the error cancellation circuit is a feedforward type positive feedback compensation circuit, it is easy to have an adverse effect on the stability of the circuit system, and the influence of the error control signal Vcomp on the circuit system can be eliminated by filtering through the filter 43. Specifically, a filter 43 is connected in series between the output end of the loop compensation circuit 30 and the gain circuit, and the filtered Vcomp is superimposed on the first voltage reference signal Vref by an adder to generate the second voltage reference signal Vref _ buf after being controlled by the gain of the gain circuit.
On the other hand, the error control signal Vcomp may be overlapped with the first voltage reference signal Vref, gain-controlled by the gain circuit, and then filtered by the filter 43; or, the error control signal Vcomp is first subjected to gain control by the gain circuit, then superposed with the first voltage reference signal Vref, and then filtered by the filter 43. That is, in the present invention, there is no sequential limitation between the gain circuit, the filter circuit, and the adder circuit.
Fig. 7 shows a time-based plot of signals associated with a control system of a possible embodiment of the present invention. As shown in the figure, the main power converter adopts a DCM mode to realize peak current control, and controls the on-time of the main power switch M through an error control signal Vcomp. Current sampling signal I of main power circuit when input or load is in steady state L And the error control signal Vcomp is stabilized in a specific amplitude value and is unchanged, the fixed clock signal CLK and the amplifying circuit output signal which are respectively input into the set end S and the reset end R by the trigger circuit are used for generating a PWM control signal with specific frequency at the output end of the trigger circuit, and the main power switch tube M is switched on or switched off under the control of the PWM control signal. Taking the instant load becoming larger as an example, the output voltage Vout of the main power circuit is reduced at this time, i.e. the voltage feedback signal V changes synchronously with the output voltage FB Following the decrease, a following voltage feedback signal V is generated by operation of the loop compensation circuit 30 FB While synchronizing the increasing error control signal Vcom. With the rising amplitude of the error control signal Vcomp, the main power switch tube M is conducted for a time T under the control of the PWM control signal ON Increase, output current rises to feed back signal V to voltage FB Increased compensation of the fall. On the other hand, the error elimination circuit causes the second voltage reference signal Vref _ buf to increase, and further compensates the voltage feedback signal V FB To make the voltage feedback signal V FB The stable amplitude is consistent with the amplitude of the first voltage reference signal Vref _ and the output voltage Vout of the main power circuit 10 can be controlled within a high-precision amplitude, which not only ensures that the system can obtain a fast dynamic response when input changes, load fluctuations or other disturbances, but also stabilizes the output voltage of the main power circuit 10 within a set voltage error tolerance range with high precision.
Fig. 4 is a block diagram of a control circuit system of a DC-DC converter of a third embodiment of the present invention. The main power circuit of this embodiment is a buck converter 110. The third embodiment is one of the second embodiment and the first embodiment, but is not limited to this embodiment.
In the control circuit 300 of the present embodiment, the buck converter 110 may include a main power switch M1, an inductor L1, and a diode D1, and the buck converter 110 is configured to receive an input voltage Vin and output a constant, precision requirement of the voltage Vout to the load. For example, when the input changes, the load fluctuation or other disturbances occur, the switch control circuit 120 applies the pulse width modulation signal PWM to the main power switch M1 to turn on or off the main power switch M1 under the control of the PWM signal, and the on time of the main power switch M1 is controlled by the error control signal Vcomp, i.e., the error control signal Vcomp determines the duty ratio or the peak current information of the main power circuit. The main power switch M1 increases its on time in response to the increase of the error control signal Vcomp, and the output voltage of the main power circuit 110 is stabilized within the set voltage error allowable range with high accuracy.
The switch control circuit 120 generates a PWM control signal to control the switching state of the main power switch M1, and includes a trigger circuit 122 and a comparison circuit 121, wherein an inverting input terminal of the comparison circuit 121 is coupled to the main power circuit 110, and receives a current sampling signal I of the main power circuit 110 L The non-inverting input terminal is coupled to the output of the loop compensation circuit 130, and receives the error control signal Vcomp generated by the loop compensation circuit 130. A reset terminal R of the trigger circuit 122 is coupled to an output terminal of the comparison circuit 121, and the comparison circuit 121 is configured to couple the error control signal Vcomp and the current sampling signal I of the main power circuit L The comparison is performed to generate a trigger signal at the reset terminal R of the flip-flop circuit, and the set terminal S of the flip-flop circuit 122 receives the clock signal CLK. The switch control circuit 120 controls the current feedback signal I of the main power circuit 110 according to the error control signal Vcomp L And a clock signal CLK which generates a PWM control signal at its output terminal to turn on or off the main power switch M1 of the main power circuit 110 to control the on-time of the main power switch M1.
The trigger circuit 122 has a set terminal S receiving a clock signal CLK with a fixed frequency, and a reset terminal R receiving a reset signal, the main power switch M1 is turned on, and the inductive current I L On the linear directionAnd (5) rising. When the current samples the signal I L When the peak value reaches the amplitude of the error control signal Vcomp, the trigger circuit 122 drives the main power switch tube M1 to turn off, so that the current sampling signal I L The peak value is constant, so that the output average current is ensured to enable the output voltage Vout of the buck converter 110 to be rapidly adjusted to the set voltage error allowable range.
In the present invention, the error cancellation circuit 140 may further include an adder, a gain circuit, a filter, and an isolation circuit, and the error cancellation circuit 140 superimposes the error control signal Vcomp and the first voltage reference signal Vref to generate the second voltage reference signal Vref _ buf.
In some embodiments, the filter in the error cancellation circuit 140 is a low frequency filter, which may be a normal first order RC filter or other first order filter, to perform low frequency filtering on the error control signal Vcomp.
In the present invention, the low-frequency filter is preferably a switched capacitor filter, and the switched capacitor filter is configured to adjust the on or off of at least one switching tube in the switched capacitor filter according to the same-frequency clock signal CLK in the set end S of the RS trigger circuit 122.
Further, the switched capacitor filter comprises two switching tubes. In this embodiment, the switch capacitor filter includes a switch tube S11, a switch tube S12, a capacitor C11, and a capacitor C12, and the switch states of the switch tube S11 and the switch tube S12 are alternately turned on or off by being triggered by a same-frequency clock signal CLK. The capacitor C11, the switch tube S11 and the switch tube S12 form an equivalent resistor R ', the equivalent resistor R' and the capacitor C12 form a first-order low-pass link, and the switch tube S11 and the switch tube S12 are complementarily conducted at a switching frequency f to generate an equivalent resistor
Figure BDA0003650905270000091
The switching frequency f is the frequency of the clock signal CLK of the same frequency at the set terminal S of the flip-flop circuit 122. Obviously, the time constant affecting the frequency response of the filter circuit depends on the clock period of the clock signal CLK and the ratio of the capacitors C11 and C12, C12/C11, and the ratio of the capacitors can be adjusted with high precision regardless of the absolute values of the capacitors. The appropriate time constant can be obtained by combining the frequency of the same-frequency clock signal CLK, so that the filtering can be realizedThe interference after the wave is small, and the switch tube is triggered and switched off by the same-frequency clock signal CLK, so that an additional clock source signal is not needed, the design of the circuit is further simplified, and the occupied area is reduced.
Further, the error cancellation circuit 140 includes an operational amplifier circuit 141 having an inverting input terminal coupled to an output terminal for isolating the influence of the input front-end signal on the back-end circuit.
In the present invention, in order to simplify the circuit design and the occupied area and improve the accuracy of the circuit in controlling the steady-state error, further, the set of the adder and the gain circuit in the error cancellation circuit 140 may be a four-input operation amplification circuit 142. The first non-inverting input end of the four-input operational amplifier receives the error control signal subjected to filtering isolation processing, the first non-inverting input end and the first inverting input end are connected across a second resistor R11 and then grounded through a third resistor R12, the third non-inverting input end receives the first voltage reference signal Vref, the fourth inverting input end is coupled with the output end of the operational amplifier circuit, and a second voltage reference signal Vref _ buf is output as an input signal of the non-inverting input end of the cross-conducting amplifier circuit Gm in the loop compensation circuit 30.
The voltage division of the second resistor R11 and the third resistor R12 generates a voltage gain K':
Figure BDA0003650905270000101
after the addition operation of the four-input operation amplifying circuit 142, a second voltage reference signal Vref _ buf is obtained to compensate the control error of the loop compensation circuit 130.
The expression of the technical scheme is as follows:
Figure BDA0003650905270000102
voltage drop V of R11 in circuit R1 The method can obtain higher common mode voltage and is beneficial to the simplified design of the circuit.
Therefore, in the invention, the gain value of the error elimination circuit is easily adjusted by adjusting the resistance values of R11 and R12, and the accurate adjustment of the control circuit to the steady-state error is realized by combining the parameter control in the loop compensation circuit.
The control circuit for adjusting the steady-state error provided by the invention has the advantages that the circuit size is smaller, the complexity and the cost of a system are effectively reduced, the control circuit of the system is simplified, the circuit size is reduced, the control circuit has quick dynamic response, and the control circuit is ensured to have high steady-state precision output.
Fig. 5 is a schematic diagram of a control circuit of a DC-DC converter according to a fourth embodiment of the present invention. The main power circuit of this embodiment is the boost converter 210, and the fourth embodiment is one of the second embodiment and the first embodiment, but is not limited to this embodiment. The control method of the present embodiment is the same as that of the buck converter.
In this embodiment, the boost converter 210 may include a main power switch M2, an inductor L2, and a diode D2.
Boost converter 210 is configured to receive an input voltage Vin and output a substantially constant voltage Vout to a load. When the input or the load changes, the control circuit 400 applies a pulse width modulation signal PWM to the main power switch transistor M1 to turn on or off the main power switch transistor M1 under the control of the PWM signal, and the on time of the main power switch transistor M1 is controlled by the error control signal Vcomp, that is, the error control signal Vcomp determines the duty ratio or the peak current information of the main power circuit. The main power switch M2 has a longer on-time following the increase of the error control signal Vcomp, so that the output voltage of the main power circuit 210 returns to the allowable range of the set voltage error.
In the description or in the accompanying fig. 1-4, variants of relevant parts of the present fourth embodiment are shown, and those identical elements already described above will not be described again in connection with this embodiment.
The present invention generally describes a control circuit for a DC-DC converter for controlling an output in a main power circuit, the control circuit comprising: the error elimination circuit generates a second voltage reference signal according to the error control signal and the first voltage reference signal so as to eliminate the control error of the loop compensation circuit; the loop compensation circuit generates the error control signal according to a second voltage reference signal and a voltage feedback signal of the main power circuit; and the switch control circuit controls the main power switch tube based on the error control signal so as to control the circuit output voltage of the main power.
The invention also generally describes a direct current power supply circuit in combination with a control circuit, which comprises the control circuit of the DC-DC converter and a main power switch tube. The direct current power supply circuit operates in an interrupted current mode.
The present invention also generally describes, in conjunction with a control circuit, a method of controlling a DC-DC converter, comprising: generating a second voltage reference signal for eliminating the control error of the loop compensation circuit according to the error control signal and the first voltage reference signal; and controlling a main power switch tube in the main power circuit according to the error control signal generated according to the second voltage reference signal and the voltage feedback signal of the main power circuit so as to control the output voltage of the main power circuit.
The invention also generally describes a direct current voltage converter in combination with a control circuit, which comprises at least part of the control circuit of the DC-DC converter and is applied to the direct current voltage converter.
The invention also describes a control chip of a DC-DC converter in combination with a control circuit, which is applied to a DC-DC voltage converter, and comprises the control circuit of the DC-DC converter, which is used for controlling the output of a main power circuit, and the control circuit comprises: the error elimination circuit generates a second voltage reference signal according to the error control signal and the first voltage reference signal so as to eliminate the control error of the loop compensation circuit; the loop compensation circuit generates the error control signal according to a second voltage reference signal and a voltage feedback signal of the main power circuit; and the switch control circuit controls the main power switch tube based on the error control signal so as to control the circuit output voltage of the main power.
The description and application of the present invention are illustrative, and are not intended to limit the scope of the invention to the embodiments described above. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

Claims (18)

1. A control circuit for a DC-DC converter for controlling an output in a main power circuit, the control circuit comprising:
the error elimination circuit generates a second voltage reference signal according to the error control signal and the first voltage reference signal so as to eliminate the control error of the loop compensation circuit;
a loop compensation circuit that generates the error control signal based on the second voltage reference signal and a voltage feedback signal of the main power circuit; and
and the switch control circuit controls the main power switch tube based on the error control signal so as to control the circuit output voltage of the main power.
2. The control circuit of claim 1, wherein:
the loop compensation circuit includes an amplification circuit having a first input terminal receiving the second voltage reference signal, a second input terminal receiving the voltage feedback signal, and an output terminal generating an error control signal.
3. The control circuit of claim 2, wherein:
the amplifying circuit is a transconductance amplifying circuit, a first input end of the transconductance amplifying circuit is a non-inverting input end and receives the second voltage reference signal, a second input end of the transconductance amplifying circuit is an inverting input end and receives the voltage feedback signal, an output end of the transconductance amplifying circuit is coupled with a first resistor, and an output end of the transconductance amplifying circuit generates an error control signal which is in a positive relation with a peak value of the current sampling signal.
4. The control circuit of claim 3, wherein:
the gain value of the error cancellation circuit reflects the inverse of the product of the transconductance amplification circuit and the first resistance in the loop compensation circuit.
5. The control circuit of claim 1, wherein:
and the conduction time of a main power switch tube of the main power circuit is the same as the variation trend of the error control signal.
6. The control circuit of claim 1, wherein:
the switch control circuit comprises a comparison circuit and a trigger circuit, wherein the comparison circuit is used for comparing the error control signal with a current sampling signal of the main power circuit to generate a trigger signal of a reset end of the trigger circuit so as to adjust the conduction time of the main power switch tube.
7. The control circuit of claim 1, wherein the error cancellation circuit comprises:
a gain circuit for performing gain control on the error control signal to generate a gain; and the number of the first and second groups,
and the adder is used for generating the second voltage reference signal by adding a gain signal of the error control signal and the first voltage reference signal.
8. The control circuit of claim 1, wherein the error cancellation circuit comprises:
and the adder is used for generating the second voltage reference signal by adding the error control signal and the first voltage reference signal.
And the gain circuit is used for carrying out gain calculation on the second voltage reference signal.
9. The control circuit of claim 7 or 8, wherein the error cancellation circuit further comprises:
and the filter is used for carrying out low-frequency filtering on the error control signal or the error control signal after operation.
10. The control circuit of claim 9, wherein:
the filter is a switched capacitor filter, and the on or off of at least one switching tube in the switched capacitor filter is controlled according to a clock signal in the position end of the trigger circuit.
11. The control circuit of claim 8, wherein:
the adder is a four-input operational amplifier circuit, a first in-phase input end receives the error control signal or the error control signal subjected to filtering and isolating processing, a second resistor is connected between the first in-phase input end and a first out-of-phase input end in a bridging mode and then grounded through a third resistor, the third in-phase input end receives the first voltage reference signal Vref, and a fourth out-of-phase input end is coupled with an output end of the adder and outputs a second voltage reference signal as an input signal of the in-phase input end of the transconductance amplifier circuit.
12. A dc power supply circuit comprising a control circuit as claimed in any one of claims 1 to 11 and a main power switch tube.
13. The dc power supply circuit of claim 12 operating in discontinuous current mode.
14. A method of controlling a DC-DC converter, comprising:
generating a second voltage reference signal for eliminating the control error of the loop compensation circuit according to the error control signal and the first voltage reference signal; and the number of the first and second groups,
and controlling a main power switch tube in the main power circuit according to the error control signal generated according to the second voltage reference signal and the voltage feedback signal of the main power circuit so as to control the output voltage of the main power circuit.
15. The control method of claim 14, wherein the step of generating a second voltage reference signal for canceling the control error of the loop compensation circuit based on the error control signal and the first voltage reference signal comprises:
performing gain calculation on the error control signal to obtain a gain signal; and
and adding the gain signal and the first voltage reference signal to obtain a second voltage reference signal, or adding the error control signal and the first voltage reference signal and then obtaining the second voltage reference signal through gain calculation.
16. The method of claim 15, wherein the step of generating a second voltage reference signal for canceling the control error of the loop compensation circuit based on the error control signal and the first voltage reference signal further comprises: the error control signal is low frequency filtered.
17. The control method according to claim 11, characterized in that:
and after the error control signal is compared with the current sampling signal, a trigger signal connected to a reset end of the trigger circuit is generated, so that the trigger circuit controls the conduction time of the main power switch tube to control the output voltage of the main power circuit.
18. A DC voltage converter, characterized in that a control circuit comprising at least part of a DC-DC converter according to any of claims 1-11 is applied to a DC-DC voltage converter.
CN202210542717.3A 2022-05-18 2022-05-18 DCM control circuit with high dynamic response and high precision and control method thereof Pending CN114977740A (en)

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