CN115085538A - Control circuit applied to resonant switched capacitor voltage converter - Google Patents
Control circuit applied to resonant switched capacitor voltage converter Download PDFInfo
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- CN115085538A CN115085538A CN202110273863.6A CN202110273863A CN115085538A CN 115085538 A CN115085538 A CN 115085538A CN 202110273863 A CN202110273863 A CN 202110273863A CN 115085538 A CN115085538 A CN 115085538A
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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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/06—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider
- H02M3/07—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using resistors or capacitors, e.g. potential divider using capacitors charged and discharged alternately by semiconductor devices with control electrode, e.g. charge pumps
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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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
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Abstract
A control circuit applied to a resonant switched capacitor voltage converter is characterized in that an inductor is added in the switched capacitor voltage converter and is connected with a capacitor of the switched capacitor voltage converter in series to form an LC resonant unit; the control circuit detects the inductive current in the LC resonance unit when the switching signal is in a first state in each switching period by using the detection module, when the detection module detects that the inductive current in the LC resonance unit is reduced to zero, the control module controls the switching signal adjusting module to change the switching signal from the first state to a second state, and the maintaining time of the switching signal in the second state is equal to the maintaining time of the first state in the current switching period, so that the first state and the second state respectively account for 50% in one switching period of the switching signal; after the adjustment of a plurality of switching periods, the switching frequency of the switching signal is consistent with the resonant frequency of the LC resonant unit. The invention can reduce the loss of the switch and the capacitor in the switch capacitor voltage converter and improve the conversion efficiency.
Description
Technical Field
The invention belongs to the technical field of power supply management, and relates to a control circuit applied to a resonant switched capacitor voltage converter formed by adding an inductor.
Background
The switch capacitor voltage converter is widely applied to various power management occasions as a basic power conversion structure to realize voltage and current conversion between input and output in various proportions. The switched capacitor voltage converter generally comprises a switching tube and a capacitor, and the control of the stored charge of the capacitor is realized by controlling the on and off of the switching tube, so that the charge is carried from an input end to an output end in the switched capacitor voltage converter by using the change of the stored charge of the capacitor.
Fig. 1 illustrates a typical 4:1 switch-capacitor voltage converter, wherein the input and output terminals of the switch-capacitor voltage converter are interchangeable to achieve a 1: 4 voltage conversion. In the 4:1 switch capacitor voltage converter shown in fig. 1, the capacitors C1-C3 are controlled to store charges through the switch tubes Q1-Q8, so that the charges are carried from the input end to the output end through the capacitors C1, C2 and C3, and the output voltage VOUT = VIN/4 and the output currents IOUT =4 × IIN are input voltage and input current.
The conversion efficiency is the most important index of the switch capacitor voltage converter, and determines the loading capacity and temperature rise condition of the voltage converter. The higher the conversion efficiency, the greater the load capacity of the voltage converter and the lower the temperature rise. The main loss of the switch capacitor voltage converter is from the conduction loss of each switch in the first circuit and the second circuit; secondly, driving loss of each switch; and thirdly, the Equivalent Series Resistance (ESR) loss of each capacitor. The key to improving the conversion efficiency is how to reduce the above losses, where the losses of one and three are proportional to the RMS current flowing through the switch and the capacitor, so the RMS current, i.e. the abbreviation of root mean square, represents the root mean square, and in fact the equivalent dc current, must be reduced. In addition, the conventional switch capacitor voltage converter has a large number of capacitors, which significantly increases the area/height of the whole scheme due to the large volume of the high voltage-withstanding capacitor.
Disclosure of Invention
Based on the characteristics of loss in the switch-capacitor voltage converter and RMS current flowing through a switch and a capacitor, the invention adds an inductor and the capacitor in the traditional switch-capacitor voltage converter structure to form an LC resonance unit in series, and the switching frequency of a switching signal in the switch-capacitor voltage converter automatically tracks the resonance frequency of the LC resonance unit through a control circuit, thereby reducing the RMS current flowing through each switch tube and capacitor under the same output current, reducing the loss of the switch and the capacitor and improving the conversion efficiency.
The technical scheme of the invention is as follows:
a control circuit applied to a resonant switched capacitor voltage converter comprises a plurality of switching tubes and at least one capacitor, and is used for controlling the on and off of each switching tube according to a switching signal to realize the control of the stored charges of the capacitor;
one capacitor of the switched capacitor voltage converter is connected with an inductor in series to form an LC resonance unit;
the switching signal has a first state and a second state, and is enabled to be in the first state in a switching period and then to be converted into the second state;
the control circuit comprises a detection module and a switching signal adjusting module, wherein the detection module is used for detecting the inductive current in the LC resonance unit when the switching signal is in a first state in each switching period, when the detection module detects that the inductive current in the LC resonance unit is reduced to zero, the switching signal adjusting module changes the switching signal from the first state to a second state according to the detection result of the detection module, and the switching signal adjusting module controls the maintaining time of the switching signal in the second state to be equal to the maintaining time of the first state in the current switching period, so that the first state and the second state respectively account for 50% in one switching period of the switching signal; and after the adjustment of a plurality of switching periods, the switching frequency of the switching signal is consistent with the resonant frequency of the LC resonant unit.
Specifically, the switching signal adjusting module includes a switching unit, a first current source, a fourth capacitor, a fifth capacitor, a sample-and-hold unit, and a first comparator, where capacitance values of the fourth capacitor and the fifth capacitor are equal; the first connecting end of the fourth capacitor is grounded, and the second connecting end of the fourth capacitor is controlled by the switch unit to be connected with the first current source; the first connecting end of the fifth capacitor is grounded, and the second connecting end of the fifth capacitor is controlled by the switch unit to be connected with the first current source;
when the switching signal is in a first state, the switching unit controls the first current source to be connected with the fourth capacitor, and the first current source is disconnected from the fifth capacitor, so that the first current source charges the fourth capacitor;
when the detection module detects that the inductive current in the LC resonance unit drops to zero and the switching signal is changed from a first state to a second state, the sampling and holding unit samples the voltage on the fourth capacitor and outputs the voltage to a first input end of a second comparator;
after the switching signal is converted into the second state, the switching unit controls the first current source to be connected with the fifth capacitor, and the connection between the first current source and the fourth capacitor is disconnected, so that the first current source charges the fifth capacitor; and outputting the voltage on the fifth capacitor to the second input end of the second comparator, and when the voltage of the second input end of the second comparator rises to be equal to the voltage of the first input end of the second comparator, the output of the second comparator is inverted to control the switching signal to be changed from the second state to the first state.
Specifically, the sample-and-hold unit includes a sixth capacitor, the switch unit includes a first switch, a second switch, a third switch, a fourth switch, and a fifth switch,
one end of the first switch is connected with the first current source, and the other end of the first switch is connected with the second connecting end of the fourth capacitor;
one end of the second switch is connected with the first current source, and the other end of the second switch is connected with the second connecting end of the fifth capacitor;
one end of the third switch is grounded, and the other end of the third switch is connected with the second connecting end of the fourth capacitor;
one end of the fourth switch is grounded, and the other end of the fourth switch is connected with the second connecting end of the fifth capacitor;
one end of the fifth switch is connected with the second connecting end of the fourth capacitor, and the other end of the fifth switch is connected with the first input end of the first comparator and is grounded after passing through the sixth capacitor;
the first switch, the second switch, the third switch and the fourth switch are controlled by the switch signal, when the switch signal is in a first state, the first switch and the fourth switch are controlled to be closed, and the second switch and the third switch are controlled to be opened; when the switching signal is in a second state, the second switch and the third switch are controlled to be closed, and the first switch and the fourth switch are controlled to be opened;
a pulse signal is generated for controlling the fifth switch to close when the switching signal transitions from the first state to the second state.
Specifically, the switched capacitor voltage converter comprises eight switching tubes which are respectively marked as a first switching tube to an eighth switching tube, and the switched capacitor voltage converter comprises three capacitors which are respectively marked as a first capacitor to a third capacitor;
a first switching tube, a second switching tube, a third switching tube and a fourth switching tube are sequentially connected in series between a first voltage conversion end and a second voltage conversion end of the switched capacitor voltage converter;
the fifth switching tube and the sixth switching tube are connected in series and in parallel between the second voltage conversion end of the switched capacitor voltage converter and the ground; the seventh switching tube and the eighth switching tube are connected in series and in parallel between the second voltage conversion end of the switched capacitor voltage converter and the ground;
an inductor is connected with a first capacitor in series to form an LC resonance unit, one end of the LC resonance unit is connected with a series point of a first switching tube and a second switching tube, and the other end of the LC resonance unit is connected with a series point of a fifth switching tube and a sixth switching tube;
one end of the second capacitor is connected with the series point of the second switching tube and the third switching tube, and the other end of the second capacitor is connected with the series point of the seventh switching tube and the eighth switching tube;
one end of the third capacitor is connected with the series point of the third switching tube and the fourth switching tube, and the other end of the third capacitor is connected with the series point of the fifth switching tube and the sixth switching tube;
when the switching signal is in a first state, controlling the first switching tube, the third switching tube, the fifth switching tube and the eighth switching tube to be switched on, and controlling the second switching tube, the fourth switching tube, the sixth switching tube and the seventh switching tube to be switched off; when the switching signal is in a second state, the second switching tube, the fourth switching tube, the sixth switching tube and the seventh switching tube are controlled to be switched on, and the first switching tube, the third switching tube, the fifth switching tube and the eighth switching tube are switched off.
Specifically, the detection module includes a second comparator, the second comparator is enabled when the first switching tube is turned on, a positive input end of the second comparator is connected to a series point of the first switching tube and the second switching tube, a negative input end of the second comparator is connected to a first voltage conversion end of the switched capacitor voltage converter, and when an inductive current in the LC resonance unit decreases to zero, a positive input end voltage of the second comparator is equal to a negative input end voltage of the second comparator, and an output of the second comparator is inverted.
Specifically, eight switching tubes of the switched capacitor voltage converter are all NMOS tubes, the switching signal adjusting module generates a first control signal and a second control signal according to the switching signal, the first control signal is used for controlling a first switching tube, a third switching tube, a fifth switching tube and an eighth switching tube, and the second control signal is used for controlling a second switching tube, a fourth switching tube, a sixth switching tube and a seventh switching tube; a first input end of the first comparator is a negative input end, and a second input end of the first comparator is a positive input end;
the switching signal adjusting module further comprises a first phase inverter, a second phase inverter, a first D trigger and a second D trigger; the input end of the first inverter is connected with the output end of the second comparator and the clock input end of the second D trigger, and the output end of the first inverter is connected with the position end of the first D trigger; the input end of the second inverter is connected with the output end of the first comparator and the clock input end of the first D trigger, and the output end of the second inverter is connected with the setting end of the second D trigger; the D input end of the first D trigger is connected with a high level signal, and the positive output end of the first D trigger generates the first control signal; the D input end of the second D trigger is connected with a high level signal, and the positive output end of the second D trigger generates the second control signal.
The invention has the beneficial effects that: the invention provides that an inductor and a capacitor of the inductor are introduced into a switched capacitor converter to form an LC resonance unit, and a control circuit is utilized to control the switching frequency of a switching signal in the switched capacitor converter to be consistent with the resonance frequency of the LC resonance unit, so that the loss of the switch and the capacitor is reduced, and the conversion efficiency is improved; in addition, only one inductor is required to be introduced into the switched capacitor converter, and a capacitor with larger volume is not required to be introduced, so that the conversion efficiency of the switched capacitor converter can be improved by using smaller area/height.
Drawings
The following description of various embodiments of the invention may be better understood with reference to the following drawings, which schematically illustrate major features of some embodiments of the invention. These figures and examples provide some embodiments of the invention in a non-limiting, non-exhaustive manner. For purposes of clarity, the same reference numbers will be used in different drawings to identify the same or similar elements or structures having the same function.
Fig. 1 is a schematic diagram of a conventional switched capacitor voltage converter.
Fig. 2 is a schematic connection diagram of a conventional switched capacitor voltage converter with an inductor to form an LC resonant unit, in which the control circuit of the present invention is applied.
Fig. 3 is a schematic diagram of a specific structure of a control circuit applied to a resonant switched capacitor voltage converter according to an embodiment of the present invention.
Fig. 4 is a comparison graph of waveforms of current flowing through the first capacitor C1 before and after the control circuit according to the present invention is applied to the embodiment shown in fig. 2, where IC1 represents the current flowing through the first capacitor C1 when the control circuit according to the present invention is not applied, and IC1_ new represents the current flowing through the first capacitor C1 after the control circuit according to the present invention is applied.
Fig. 5 is a waveform diagram of some key nodes after applying the present invention to a switched capacitor voltage converter in an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in detail with reference to the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The switched capacitor voltage converter generally comprises a plurality of switching tubes and at least one capacitor, and the control of the stored charges of the capacitor can be realized by controlling the on and off of each switching tube according to a switching signal, so that the voltage conversion between two voltage conversion ends of the switched capacitor voltage converter is realized. The control circuit provided by the invention is characterized in that an inductor is added into a traditional switch capacitor voltage converter and is connected with one of the original capacitors in series to form an LC resonance unit, so that the switch capacitor voltage converter is converted into a resonance type switch capacitor voltage converter; and the control circuit provided by the invention is used for controlling the switching frequency of a switching signal in the switched capacitor voltage converter to follow the resonant frequency of the LC resonant unit, so that the RMS current of the switched capacitor voltage converter is reduced, the loss is reduced, and the conversion efficiency is improved.
The switching signal has a first state and a second state, and the switching signal is enabled to be in the first state in a switching period and then to be converted into the second state. The control circuit provided by the invention is used for adjusting the switching frequency of the switching signal, and comprises a detection module and a switching signal adjusting module, wherein the detection module is used for detecting the inductive current in the LC resonance unit when the switching signal is in a first state in each switching period, and judging when the inductive current in the LC resonance unit drops to zero in the period. When the detection module detects that the inductive current in the LC resonance unit drops to zero, the switching signal adjusting module converts the switching signal from the first state to the second state according to the detection result of the detection module, and the switching signal adjusting module controls the maintaining time of the switching signal in the second state to be equal to the maintaining time of the first state in the current switching period, so that the first state and the second state respectively account for 50% in one switching period of the switching signal. Therefore, each switching period adjusts the period of the switching signal according to the inductive current in the LC resonance unit, so that the switching frequency of the switching signal is adjusted, and the switching frequency of the switching signal after being adjusted by a plurality of switching periods can be kept consistent with the resonance frequency of the LC resonance unit.
As shown in fig. 3, an implementation structure of a switching signal adjusting module is provided, where the switching signal adjusting module includes a switching unit, a first current source IOSC, a fourth capacitor C4, a fifth capacitor C5, a sample-and-hold unit, and a first comparator COMP 1; a first connection end of the fourth capacitor C4 is grounded, and a second connection end thereof is controlled by the switch unit to be connected with the first current source IOSC; a first connection end of the fifth capacitor C5 is grounded, and a second connection end of the fifth capacitor C5 is controlled by the switch unit to be connected with the first current source IOSC; when the switching signal is in the first state, the switching unit controls the first current source IOSC to be connected with the fourth capacitor C4, and disconnects the first current source IOSC from the fifth capacitor C5, so that the first current source IOSC charges the fourth capacitor C4, and the RAMP voltage RAMP1 is generated on the fourth capacitor C4; when the detection module detects that the inductor current in the LC resonant unit drops to zero and the switching signal is changed from the first state to the second state, the sample-and-hold unit samples the voltage across the fourth capacitor C4 (i.e., the PEAK voltage RAMP1_ PEAK of the RAMP voltage RAMP 1) and outputs the voltage to the first input terminal of the second comparator; when the switching signal is changed to the second state, the switching unit controls the first current source IOSC to be connected with the fifth capacitor C5, and disconnects the first current source IOSC from the fourth capacitor C4, so that the first current source IOSC charges the fifth capacitor C5, and a RAMP voltage RAMP2 is generated on the fifth capacitor C5; the voltage on the fifth capacitor C5 is output to the second input terminal of the second comparator, and when the voltage of the second input terminal of the second comparator (RAMP voltage RAMP 2) rises to be equal to the voltage of the first input terminal thereof (PEAK voltage RAMP1_ PEAK of RAMP voltage RAMP 1), the output of the second comparator is inverted, and the control switch signal is changed from the second state to the first state. Since the capacitance values of the fourth capacitor C4 and the fifth capacitor C5 are equal, it can be ensured that the holding time of the switching signal in the second state is equal to the holding time of the switching signal in the first state in each switching period, i.e. the duty ratios of the first state and the second state are 50% respectively.
In some embodiments, as shown in fig. 3, the sample and hold unit includes a sixth capacitor C6, the switch unit includes a first switch S1, a second switch S2, a third switch S3, a fourth switch S4 and a fifth switch S5, one end of the first switch S1 is connected to the first current source IOSC, and the other end is connected to the second connection terminal of the fourth capacitor C4; one end of the second switch S2 is connected to the first current source IOSC, and the other end is connected to the second connection end of the fifth capacitor C5; one end of the third switch S3 is grounded, and the other end is connected with the second connection end of the fourth capacitor C4; one end of the fourth switch S4 is grounded, and the other end is connected with the second connection end of the fifth capacitor C5; one end of the fifth switch S5 is connected to the second connection end of the fourth capacitor C4, and the other end is connected to the first input end of the first comparator COMP1 and grounded through the sixth capacitor C6.
The first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 are controlled by the switching signals, when the switching signals are in a first state, the first switch S1 and the fourth switch S4 are controlled to be closed, the second switch S2 and the third switch S3 are controlled to be open, and the first current source IOSC charges the fourth capacitor C4; when the switching signal is in the second state, the second switch S2 and the third switch S3 are controlled to be closed, the first switch S1 and the fourth switch S4 are controlled to be open, and the first current source IOSC charges the fifth capacitor C5; the peak voltage of the RAMP voltage RAMP1 on the fourth capacitor C4 may be sampled onto the sixth capacitor C6 by generating a PULSE signal CLK1_ PULSE for controlling the fifth switch S5 to close when the switching signal transits from the first state to the second state.
In the following, the control circuit provided by the present invention is applied to a specific switch capacitor voltage converter as an example, and the embodiment takes a 4:1 switch capacitor voltage converter as an example, but it should be noted that the present invention can also be applied to switch capacitor voltage converters with other voltage conversion ratios or other structures, and the embodiment is not intended to limit the protection scope of the present invention.
As shown in fig. 2, the 4:1 switch capacitor voltage converter adopted in this embodiment includes eight switch transistors, which are respectively denoted as a first switch transistor Q1 to an eighth switch transistor Q8, and includes three capacitors, which are respectively denoted as a first capacitor C1 to a third capacitor C3; a first switch tube Q1, a second switch tube Q2, a third switch tube Q3 and a fourth switch tube Q4 are sequentially connected in series between a first voltage conversion end and a second voltage conversion end of the switched capacitor voltage converter, the switched capacitor voltage converter comprises two voltage conversion ends, and as the voltage conversion ratio of 4:1 is realized in the embodiment, the first voltage conversion end connected with the first switch tube Q1 is used as an input end, and the second voltage conversion end connected with the fourth switch tube Q4 is used as an output end; of course, the second voltage conversion terminal connected to the fourth switching tube Q4 may be used as the input terminal, and the first voltage conversion terminal connected to the first switching tube Q1 may be used as the output terminal to achieve a voltage conversion ratio of 1: 4.
In the 4:1 switch capacitor voltage converter applied in this embodiment, the fifth switch tube Q5 and the sixth switch tube Q6 are connected in series and in parallel between the second voltage conversion end of the switch capacitor voltage converter and the ground; the seventh switch tube Q7 and the eighth switch tube Q8 are connected in series and in parallel between the second voltage conversion end of the switched capacitor voltage converter and the ground; in this embodiment, an inductor L1 is added, and an inductor L1 is connected in series with a first capacitor C1 to form an LC resonant unit, although in some embodiments, the inductor may also be connected in series with a second capacitor C2 or a third capacitor C3 to form an LC resonant unit, one end of the LC resonant unit is connected to a series point of a first switching tube Q1 and a second switching tube Q2, and the other end of the LC resonant unit is connected to a series point of a fifth switching tube Q5 and a sixth switching tube Q6; one end of the second capacitor C2 is connected to the series point of the second switch tube Q2 and the third switch tube Q3, and the other end thereof is connected to the series point of the seventh switch tube Q7 and the eighth switch tube Q8; one end of the third capacitor C3 is connected to the series point of the third switching tube Q3 and the fourth switching tube Q4, and the other end thereof is connected to the series point of the fifth switching tube Q5 and the sixth switching tube Q6.
The first switch tube Q1 to the eighth switch tube Q8 are controlled by the switching signal of the switch capacitor voltage converter, when the switching signal is in the first state, the first switch tube Q1, the third switch tube Q3, the fifth switch tube Q5 and the eighth switch tube Q8 are controlled to be switched on, and the second switch tube Q2, the fourth switch tube Q4, the sixth switch tube Q6 and the seventh switch tube Q7 are controlled to be switched off; when the switching signal is in the second state, the second switching tube Q2, the fourth switching tube Q4, the sixth switching tube Q6 and the seventh switching tube Q7 are controlled to be turned on, and the first switching tube Q1, the third switching tube Q3, the fifth switching tube Q5 and the eighth switching tube Q8 are controlled to be turned off.
In this embodiment, the first switch tube Q1 to the eighth switch tube Q8 may all be implemented by NMOS tubes, and therefore, the first control signal PH1 and the second control signal PH2 may be generated according to the switch signals, the first control signal PH1 and the second control signal PH2 generate driving signals of respective switches after passing through the driving circuit, when the switch signals are in the first state, the first control signal PH1 is high, the second control signal PH2 is low, the first control signal PH1 at a high level turns on the first switch tube Q1, the third switch tube Q3, the fifth switch tube Q5, and the eighth switch tube Q8, and the second control signal PH2 at a low level turns off the second switch tube Q2, the fourth switch tube Q4, the sixth switch tube Q6, and the seventh switch tube Q7. Similarly, when the switching signal is in the second state, the first control signal PH1 is low, the second control signal PH2 is high, the low-level first control signal PH1 turns off the first switch Q1, the third switch Q3, the fifth switch Q5, and the eighth switch Q8, and the high-level second control signal PH2 turns on the second switch Q2, the fourth switch Q4, the sixth switch Q6, and the seventh switch Q7. When the first control signal PH1 and the second control signal PH2 are switched, a small dead time exists in the middle, and all the switch tubes are turned off to prevent the switch from being connected in series during switching.
Since the inductor L1 and the first capacitor C1 are connected in series to form the LC resonant unit in this embodiment, the detection module can be implemented by using a second comparator, which is enabled when the first switch Q1 is turned on, and has a positive input terminal connected to the series point C1P of the first switch Q1 and the second switch Q2, and a negative input terminal connected to the first voltage conversion terminal of the switched capacitor voltage converter (in this embodiment, the input terminal VIN of the switched capacitor voltage converter), when the inductor current in the LC resonant unit drops to zero, the voltage at the point C1P is equal to the voltage at the point VIN, that is, the voltage at the positive input of the second comparator is equal to the voltage at the negative input terminal, and the second comparator outputs the flip-flop control switching signal to switch from the first state to the second state.
As shown in fig. 3, in the embodiment, an implementation structure is provided that generates a first control signal PH1 and a second control signal PH2 by using a first inverter INV1, a second inverter INV2, a first D flip-flop DFF1 and a second D flip-flop DFF2, wherein an input end of the first inverter INV1 is connected to an output end of the second comparator COMP2 and a clock input end of the second D flip-flop DFF2, and an output end thereof is connected to a set end of the first D flip-flop DFF 1; the input end of the second inverter INV2 is connected to the output end of the first comparator COMP1 and the clock input end of the first D flip-flop DFF1, and the output end thereof is connected to the set end of the second D flip-flop DFF 2; a first input end of the first comparator COMP1 is made to be a negative input end, and a second input end thereof is made to be a positive input end; the D input end of the first D flip-flop DFF1 is connected with a high level signal ONE, and the positive output end thereof generates a first control signal PH 1; the D input terminal of the second D flip-flop DFF2 is connected to the high level signal ONE, and its positive output terminal generates the second control signal PH 2. The first control signal PH1 and the second control signal PH2 are used to control the first switch Q1 to the eighth switch Q8 after passing through the driving circuit.
The working process of the present embodiment is analyzed in detail below. As shown in fig. 2, in this embodiment, an inductor L1 and a first capacitor C1 are introduced to form an LC resonant unit in series on the basis of the conventional 4:1 switch-capacitor voltage converter shown in fig. 1, and a control circuit shown in fig. 3 is used to control each switching tube in the switch-capacitor voltage converter, so as to automatically adjust the switching frequency to track the L/C frequency. Finally, as shown in fig. 4, the current flowing through the first capacitor C1 becomes sinusoidal-like in shape, reducing RMS current at the same average current, thereby reducing losses and improving conversion efficiency.
In the present embodiment, the first control signal PH1 and the second control signal PH2 are generated by using the switching signal, such that the first control signal PH1 is high and the second control signal PH2 is low when the switching signal is in the first state, and the first control signal PH1 is low and the second control signal PH2 is high when the switching signal is in the second state.
When the first switch Q1 is turned on when the first control signal PH1 is high, and the VIN point voltage and the C1P point voltage are detected, and when the current of the inductor L1 in the LC resonant unit drops to 0, the VIN point voltage is equal to the voltage of the C1P point, the second comparator COMP2 generates a CLK1 signal, so that the switch signal ends the first state and starts the second state, that is, the first control signal PH1 is turned from high to low, and the second control signal PH2 is turned from low to high. Meanwhile, when the first control signal PH1 is high, the first current source IOSC charges the fourth capacitor C4 to generate the RAMP voltage RAMP1, and when the first control signal PH1 turns from high to low, the voltage on the fourth capacitor C4 is sampled to the sixth capacitor C6 to obtain the PEAK voltage RAMP1_ PEAK of the RAMP voltage RAMP 1.
When the second control signal PH2 is high, the first current source IOSC charges the fifth capacitor C5 to generate the RAMP voltage RAMP2, and when the RAMP2 is greater than RAMP1_ PEAK, the first comparator COMP1 generates the CLK2 signal to make the switching signal end the second state and start the first state, i.e., the second control signal PH2 is turned from high to low, and the first control signal PH1 is turned from low to high. Since the capacitance values of the fourth capacitor C4 and the fifth capacitor C5 are equal, the time for the first control signal PH1 and the second control signal PH2 to maintain the high level is equal. In each switching period, the turning-down time of the first control signal PH1 is set by detecting the inductor current, and the turning-down time of the second control signal PH2 is set by the first control signal PH1, so that the duty ratios of the first control signal PH1 and the second control signal PH2 are both guaranteed to be 50%. Therefore, the time of the period can be adjusted by detecting the inductor current in each switching period, so as to adjust the switching frequency, and when the switching frequency is finally stabilized, the inductor L1 current is 0 when the first control signal PH1 is turned down, the switching frequency is matched with the L/C resonance frequency, and the waveform of the key node is as shown in fig. 5.
In summary, the present invention adds an inductor and a capacitor in series in the conventional switch-capacitor converter structure, and controls the switching frequency of the converter to automatically track the L/C frequency, so as to reduce the RMS current flowing through each switch and capacitor under the same output current, thereby reducing the loss of the switches and capacitors and improving the conversion efficiency. Although some implementation structures of the control circuit and a specific implementation architecture of the applied switched capacitor voltage converter are provided in the embodiments, the control circuit provided by the present invention is not only applicable to the 4:1 switched capacitor voltage converter structure described in the embodiments, but also applicable to other various switched capacitor voltage converter structures, and can also achieve the effects of improving the conversion efficiency and reducing the number of capacitors; those skilled in the art can make various other specific changes and combinations based on the teachings of the present invention without departing from the spirit of the invention, and these changes and combinations are within the scope of the invention.
Claims (6)
1. A control circuit applied to a resonant switched capacitor voltage converter comprises a plurality of switching tubes and at least one capacitor, and is used for controlling the on and off of each switching tube according to a switching signal to realize the control of the stored charges of the capacitor;
one capacitor of the switched capacitor voltage converter is connected with an inductor in series to form an LC resonance unit;
the switching signal has a first state and a second state, and is enabled to be in the first state in a switching period and then to be converted into the second state;
the control circuit comprises a detection module and a switching signal adjusting module, wherein the detection module is used for detecting the inductive current in the LC resonance unit when the switching signal is in a first state in each switching period, when the detection module detects that the inductive current in the LC resonance unit is reduced to zero, the switching signal adjusting module changes the switching signal from the first state to a second state according to the detection result of the detection module, and the switching signal adjusting module controls the maintaining time of the switching signal in the second state to be equal to the maintaining time of the first state in the current switching period, so that the first state and the second state respectively account for 50% in one switching period of the switching signal; and after the adjustment of a plurality of switching periods, the switching frequency of the switching signal is consistent with the resonant frequency of the LC resonant unit.
2. The control circuit applied to the resonant switched-capacitor voltage converter as claimed in claim 1, wherein the switching signal adjusting module comprises a switching unit, a first current source, a fourth capacitor, a fifth capacitor, a sample-and-hold unit and a first comparator, wherein the capacitance values of the fourth capacitor and the fifth capacitor are equal; the first connecting end of the fourth capacitor is grounded, and the second connecting end of the fourth capacitor is controlled by the switch unit to be connected with the first current source; the first connecting end of the fifth capacitor is grounded, and the second connecting end of the fifth capacitor is controlled by the switch unit to be connected with the first current source;
when the switching signal is in a first state, the switching unit controls the first current source to be connected with the fourth capacitor, and the first current source is disconnected from the fifth capacitor, so that the first current source charges the fourth capacitor;
when the detection module detects that the inductive current in the LC resonance unit drops to zero and the switching signal is changed from a first state to a second state, the sampling and holding unit samples the voltage on the fourth capacitor and outputs the voltage to a first input end of a second comparator;
after the switching signal is converted into the second state, the switching unit controls the first current source to be connected with the fifth capacitor, and the connection between the first current source and the fourth capacitor is disconnected, so that the first current source charges the fifth capacitor; and outputting the voltage on the fifth capacitor to the second input end of the second comparator, and when the voltage of the second input end of the second comparator rises to be equal to the voltage of the first input end of the second comparator, the output of the second comparator is inverted to control the switching signal to be changed from the second state to the first state.
3. The control circuit applied to the resonant switched-capacitor voltage converter as set forth in claim 2, wherein the sample-and-hold unit comprises a sixth capacitor, the switching unit comprises a first switch, a second switch, a third switch, a fourth switch and a fifth switch,
one end of the first switch is connected with the first current source, and the other end of the first switch is connected with the second connecting end of the fourth capacitor;
one end of the second switch is connected with the first current source, and the other end of the second switch is connected with the second connecting end of the fifth capacitor;
one end of the third switch is grounded, and the other end of the third switch is connected with the second connecting end of the fourth capacitor;
one end of the fourth switch is grounded, and the other end of the fourth switch is connected with the second connecting end of the fifth capacitor;
one end of the fifth switch is connected with the second connecting end of the fourth capacitor, and the other end of the fifth switch is connected with the first input end of the first comparator and is grounded after passing through the sixth capacitor;
the first switch, the second switch, the third switch and the fourth switch are controlled by the switch signal, when the switch signal is in a first state, the first switch and the fourth switch are controlled to be closed, and the second switch and the third switch are controlled to be opened; when the switching signal is in a second state, the second switch and the third switch are controlled to be closed, and the first switch and the fourth switch are controlled to be opened;
a pulse signal is generated for controlling the fifth switch to close when the switching signal changes from the first state to the second state.
4. The control circuit applied to the resonant switched-capacitor voltage converter as claimed in claim 2 or 3, wherein the switched-capacitor voltage converter comprises eight switching tubes respectively named as first switching tube to eighth switching tube, and the switched-capacitor voltage converter comprises three capacitors respectively named as first capacitor to third capacitor;
a first switching tube, a second switching tube, a third switching tube and a fourth switching tube are sequentially connected in series from a first voltage conversion end to a second voltage conversion end of the switched capacitor voltage converter;
the fifth switching tube and the sixth switching tube are connected in series and in parallel between the second voltage conversion end of the switched capacitor voltage converter and the ground; the seventh switching tube and the eighth switching tube are connected in series and in parallel between the second voltage conversion end of the switched capacitor voltage converter and the ground;
an inductor is connected with a first capacitor in series to form an LC resonance unit, one end of the LC resonance unit is connected with a series point of a first switching tube and a second switching tube, and the other end of the LC resonance unit is connected with a series point of a fifth switching tube and a sixth switching tube;
one end of the second capacitor is connected with the series point of the second switching tube and the third switching tube, and the other end of the second capacitor is connected with the series point of the seventh switching tube and the eighth switching tube;
one end of the third capacitor is connected with the series point of the third switching tube and the fourth switching tube, and the other end of the third capacitor is connected with the series point of the fifth switching tube and the sixth switching tube;
when the switching signal is in a first state, controlling the first switching tube, the third switching tube, the fifth switching tube and the eighth switching tube to be switched on, and controlling the second switching tube, the fourth switching tube, the sixth switching tube and the seventh switching tube to be switched off; when the switching signal is in a second state, the second switching tube, the fourth switching tube, the sixth switching tube and the seventh switching tube are controlled to be switched on, and the first switching tube, the third switching tube, the fifth switching tube and the eighth switching tube are switched off.
5. The control circuit as claimed in claim 4, wherein said detection module comprises a second comparator, said second comparator is enabled when said first switch tube is turned on, its positive input terminal is connected to the series point of said first switch tube and said second switch tube, its negative input terminal is connected to the first voltage converting terminal of said switched capacitor voltage converter, and when the inductor current in said LC resonant cell decreases to zero, the positive input terminal voltage of said second comparator is equal to the negative input terminal voltage thereof, the output of said second comparator is inverted.
6. The control circuit applied to the resonant switched capacitor voltage converter as claimed in claim 5, wherein the eight switching tubes of the switched capacitor voltage converter are NMOS tubes, the switching signal adjusting module generates a first control signal and a second control signal according to the switching signal, the first control signal is used for controlling the first switching tube, the third switching tube, the fifth switching tube and the eighth switching tube, and the second control signal is used for controlling the second switching tube, the fourth switching tube, the sixth switching tube and the seventh switching tube; a first input end of the first comparator is a negative input end, and a second input end of the first comparator is a positive input end;
the switching signal adjusting module further comprises a first inverter, a second inverter, a first D trigger and a second D trigger; the input end of the first inverter is connected with the output end of the second comparator and the clock input end of the second D trigger, and the output end of the first inverter is connected with the position end of the first D trigger; the input end of the second inverter is connected with the output end of the first comparator and the clock input end of the first D trigger, and the output end of the second inverter is connected with the setting end of the second D trigger; the D input end of the first D trigger is connected with a high level signal, and the positive output end of the first D trigger generates the first control signal; the D input end of the second D trigger is connected with a high level signal, and the positive output end of the second D trigger generates the second control signal.
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