CN114696611B - Power converter and control method thereof - Google Patents
Power converter and control method thereof Download PDFInfo
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- CN114696611B CN114696611B CN202011575712.8A CN202011575712A CN114696611B CN 114696611 B CN114696611 B CN 114696611B CN 202011575712 A CN202011575712 A CN 202011575712A CN 114696611 B CN114696611 B CN 114696611B
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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
- H02M3/10—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of DC power input into DC power output without intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
-
- 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
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
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- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention relates to the technical field of integrated circuits, and provides a power converter and a control method thereof, wherein the power converter comprises a power switch tube, an inductor and a control circuit, and the power switch tube at least comprises: the power converter comprises a first power switch tube connected between the inductor and the output end of the power converter, a second power switch tube connected in parallel to two ends of the first power switch tube, and a third power switch tube positioned between the inductor and a connection node of the first power switch tube and the ground, wherein the power converter works in a negative half period, and before the output current is reduced to zero, the control circuit controls the on-off state of the power switch tube connected between the connection node and the output end of the power converter according to a control signal generated by sampling the output of the power converter and a duty ratio adjusting signal generated by logic control of a switch control signal. This can improve the accuracy of detecting the output power and the efficiency of the power converter.
Description
Technical Field
The invention relates to the technical field of integrated circuits, in particular to a power converter and a control method thereof.
Background
DC/DC switching power supply circuits are used in various fields, where power converters are an important component of DC/DC switching power supplies. With the development of technology, the functions of the DC/DC switching power supply circuit are increasingly diversified and complex, and the output power of the power converter system is also increasingly larger.
In a DC/DC switching power supply circuit, taking a Boost-type power converter (Boost) as an example, as shown in fig. 1, the Boost-type power converter 100 includes an inductor L and a power tube M11 connected between an input terminal VIN and an output terminal VOUT, a power tube M12 connected between the inductor L and ground, and a control circuit 110 and a driving circuit 120 connected to the power tube M11, a connection node SW is provided between the inductor L and the power tube M11, the control circuit 110 obtains a detection signal according to a voltage difference (assumed to be V1) across the sampling power tube M11, and provides a switching control signal PWM according to the detection signal, the driving circuit 120 generates a control signal Vg of the power tube M11 according to the switching control signal PWM, wherein, at the input terminal VIN, an inductor current IL in a negative half cycle flows from the connection node SW to the output terminal VOUT, transferring energy to the output terminal VOUT, and the inductor current IL on the inductor is reduced, and the current on the inductor cannot suddenly change, so that when the inductor current IL is small to zero-cross, the reverse current flowing from the output terminal VOUT to the connection node SW, and the reverse current flowing from the output terminal VOUT will reduce the efficiency of the power converter.
In order to increase the efficiency of the power converter, when the inductor current IL is small and approaches zero, but does not reach zero, i.e. the detection voltage v1=il×ron < V0 (preset voltage), the power transistor M11 is turned off, where RON is the on-resistance of the power transistor M11. For chips with smaller on-resistance, the detection voltage V1 is small, e.g., il=100 ma, ron=8 mohm, v1=0.8 mV. For the comparator used for comparing V1 and V0 in the detection circuit 110, the offset Voltage (VOS) of the comparator is usually 1mV, so that the voltage difference of 0.8mV cannot be accurately determined at all, and when the preset voltage V0 is smaller, the overdrive voltage of the comparator is also smaller, which results in slower flip speed and longer delay time of the comparator, and also results in failure to turn off the upper tube in time to generate reverse current, thereby reducing the efficiency of the power converter.
Disclosure of Invention
In order to solve the above technical problems, the present disclosure provides a power converter and a control method thereof, which can improve the detection accuracy of output power and the efficiency of the power converter.
In one aspect, the disclosure provides a power converter including a power switching tube and an inductor connected to each other, a control circuit connected to the power switching tube, the control circuit providing a switching control signal for controlling operation of the power switching tube such that charging and discharging of the inductor produces an inductor current to provide an output current, wherein the power switching tube includes at least:
the first power switch tube is connected between the inductor and the output end of the power converter;
The second power switch tube is connected in parallel with two ends of the first power switch tube;
The third power switch tube is positioned between the connection node of the inductor and the first power switch tube and the ground,
The power converter operates in a negative half cycle, and before the output current is reduced to zero, the control circuit controls the on-off state of a power switch tube connected between the connection node and the output end of the power converter according to a control signal generated by sampling the output of the power converter and a duty ratio regulating signal generated by logic control of the switch control signal.
Preferably, a loop control signal of a voltage loop taken from the power converter is smaller than or equal to a first preset threshold, and one of the first power switching tube and the second power switching tube is in a conducting state;
The voltage detection signal is smaller than or equal to a second preset threshold value, the first power switch tube and the second power switch tube are in an off state, the voltage detection signal is used for representing the voltage drop generated at the two ends of the first power switch tube by the output current,
And the second preset threshold is a positive number.
Preferably, the control signals include at least a first control signal and a second control signal;
And the aforementioned control circuit includes:
a first detection unit for providing the first control signal according to the comparison result of the loop control signal of the voltage loop of the power converter and the first preset threshold value;
The sampling unit is used for generating the voltage detection signal according to the pressure difference between the connecting node and the output end of the power converter;
The second detection unit is connected with the output end of the sampling unit and is used for providing the second control signal according to the comparison result of the voltage detection signal and the second preset threshold value;
And the logic control unit is respectively connected with the output end of the first detection unit and the output end of the second detection unit and is used for generating a duty ratio regulating signal according to logic control on the first control signal, the second control signal and the switch control signal so as to control the turn-off of the first power switch tube and/or the second power switch tube by the duty ratio regulating signal when the power converter works in a negative half period.
Preferably, the first detection unit includes:
A first comparator having a non-inverting input connected to the loop control signal, an inverting input connected to the first predetermined threshold, an output providing the first control signal,
And the loop control signal is used to characterize the power converter operating in the negative half-cycle as light or heavy.
Preferably, the aforementioned second detection unit includes:
And the non-inverting input end of the second comparator is connected with the output end of the sampling unit and is connected with the voltage detection signal, the inverting input end of the second comparator is connected with the second preset threshold value, and the output end of the second comparator is used for providing the second control signal.
Preferably, the aforementioned control circuit further includes:
and the driving circuit is connected with the output end of the control circuit and is used for enhancing the driving capability of the duty ratio adjusting signal and outputting the driving capability to the control end of the first power switch tube and the control end of the second power switch tube respectively.
Preferably, any one of the first power switch tube, the second power switch tube and the third power switch tube is an N-type metal oxide semiconductor field effect transistor.
In another aspect, the present disclosure also provides a control method of a power converter, the power converter including a power switching tube and an inductor connected to each other, and a control circuit connected to the power switching tube, the control circuit providing a switching control signal for controlling operation of the power switching tube such that charging and discharging of the inductor generates an inductor current to provide an output current, wherein the control method includes:
When the power converter works in a negative half period, before the output current is reduced to zero, the on-off of a power switch tube connected between the connection node and the output end of the power converter is controlled according to a control signal generated by sampling the output of the power converter and a duty ratio regulating signal generated by logic control of the switch control signal.
Preferably, the control signals include at least a first control signal and a second control signal;
and the step of controlling the on-off of the power switching tube connected between the connection node and the output end of the power converter comprises the steps of:
Providing a first control signal representative of a light load or heavy load of said power converter operating in a negative half-cycle based on a comparison of a loop control signal derived from a voltage loop of said power converter with a first predetermined threshold value as described above;
Generating a voltage detection signal according to the voltage difference between the connection node and the output end of the power converter, and providing the second control signal according to the comparison result of the voltage detection signal and the second preset threshold value, wherein the voltage detection signal is used for representing the voltage drop of the output current generated at the two ends of the first power switch tube;
And generating the duty ratio regulating signal according to logic control of the first control signal, the second control signal and the switch control signal, and controlling the on/off of the first power switch tube and/or the second power switch tube by the duty ratio regulating signal before the output current of the negative half period is reduced to zero.
Preferably, the step of controlling the turn-off of the first power switching tube and/or the second power switching tube with the duty ratio adjustment signal includes:
When the loop control signal is smaller than the first preset threshold value, one of the first power switching tube and the second power switching tube is controlled to be conducted by the duty ratio adjusting signal;
When the voltage detection signal is smaller than the second preset threshold value, the duty ratio adjusting signal is used for controlling the first power switch tube and the second power switch tube to be turned off,
And the second preset threshold is a positive number.
The power converter comprises a power switch tube, an inductor and a control circuit, wherein the power switch tube and the inductor are connected with each other, the control circuit is connected with the power switch tube, the power switch tube at least comprises a first power switch tube connected between the inductor and the output end of the power converter, a second power switch tube connected in parallel with the two ends of the first power switch tube, and a third power switch tube positioned between a connecting node of the inductor and the first power switch tube and the ground, the power converter works in a negative half cycle, and before the output current is reduced to zero, the control circuit controls the on-off state of the power switch tube connected between the connecting node and the output end of the power converter according to a control signal generated by sampling the output of the power converter and a duty ratio adjusting signal generated by logic control of the switch control signal. When the output power (output current) of the power converter is detected, the on-resistance of the output end is reduced by utilizing the two power switching tubes connected in parallel so as to expand the detection precision range of the output current, when the output current is reduced and does not reach zero, the power switching tube connected between the inductor and the output end of the power converter is turned off in time through the detection signal and the judgment result of the two-stage preset threshold value, the accurate detection of small current at the output end is improved, specifically, when the system feedback (voltage loop) is used for knowing that the power converter is in light load (loop control signal is smaller than the first preset threshold value), one of the first power switching tube and the second power switching tube is controlled to be turned on so as to increase the on-resistance of the output end, then the differential pressure at two ends of the second power switching tube (or the first power switching tube) is sampled, and when the output current is reduced to meet the preset condition (voltage detection signal is smaller than or equal to the second preset threshold value), the second power switching tube (or the first power switching tube) is turned off in time after the output current is reduced, the second power switching tube (or the first power switching tube) is turned off in time, so that the detection precision is low, the system response speed is slow, and the reverse current can not be turned off in time, and the power converter is generated. Therefore, the detection accuracy of the output power of the power converter is improved, and the efficiency of the power converter is also improved.
Furthermore, the power converter provided by the present disclosure is not limited to one type of topology, but may be applied to any suitable topology type, including but not limited to Buck converters (Buck), boost converters (Boost), flyback converters (Flyback), and Buck-Boost converters (Buck-Boost), with high applicability and reliability.
Drawings
The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of the embodiments of the present disclosure with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of a boost power converter of the prior art disclosure;
fig. 2 illustrates a schematic diagram of a boost power converter provided by an embodiment of the present disclosure;
FIG. 3 shows a schematic diagram of the control circuit in the power converter of FIG. 2;
Fig. 4 is a flow chart illustrating a control method of a power converter according to an embodiment of the disclosure.
Detailed Description
In order that the invention may be readily understood, a more complete description of the invention will be rendered by reference to the appended drawings. Preferred embodiments of the present disclosure are shown in the drawings. The present disclosure may be embodied in different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
In various embodiments, the present disclosure provides or implements improved techniques for detecting output current (inductor current) in power devices of power converter systems (e.g., dc-dc converters) having high accuracy, high speed, and good transient on-off characteristics. Unlike some previously formed techniques, techniques according to embodiments of the present invention do not require accurate sense resistors, can operate at high speed, and have good transient characteristics, making them well suited for high frequency power conversion. The current detection techniques in various embodiments may be used for various functions or features, such as current mode control or current protection in a power converter system.
The present invention will be described in detail with reference to the accompanying drawings.
Fig. 2 is a schematic diagram illustrating a structure of a boost power converter according to an embodiment of the present disclosure, and fig. 3 is a schematic diagram illustrating a control circuit in the power converter shown in fig. 2.
In one aspect, embodiments of the present disclosure provide a power converter that may be used, for example, in a DC/DC switching power supply circuit. Taking Boost as an example, referring to fig. 2 and 3, the power converter 200 includes a power switching tube and an inductor L21 connected to each other between an input terminal VIN and an output terminal VOUT, and a control circuit 210 connected to the power switching tube, the control circuit 210 providing a switching control signal PWM for controlling the operation of the power switching tube such that the inductor L21 charges and discharges to generate an inductor current, thereby providing an output current, wherein the power switching tube includes at least a first power switching tube M21 connected between the inductor L21 and the output terminal VOUT of the power converter 200, a second power switching tube M22 connected in parallel to both ends of the first power switching tube M21, and a third power switching tube M23 between a connection node SW of the inductor L21 and the first power switching tube M21 and ground,
And when the power converter 200 operates in the negative half cycle, the control circuit 210 can control the on-off state of the power switching transistor (M21 and/or M22) connected between the connection node SW and the output terminal VOUT of the power converter 200 according to the duty cycle adjustment signal DRC generated by the logic control of the control signal generated by sampling the output of the power converter 200 and the switching control signal PWM before the output current decreases to zero.
Further, any one of the first power switch tube M21, the second power switch tube M22 and the third power switch tube M23 is a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), and in this embodiment, the first power switch tube M21, the second power switch tube M22 and the third power switch tube M23 are NMOS tubes (hereinafter, corresponding simply referred to as M21, M22 and M22).
In this embodiment, the loop control signal VEA taken from the voltage loop 230 in the power converter 200 is less than or equal to a first preset threshold, one of M21 and M22 is in an on state, the voltage detection signal V1 is less than or equal to a second preset threshold, both M21 and M22 are in an off state,
The second preset threshold is a positive number, the voltage detection signal is used for representing a voltage drop generated at two ends of the M21 of the output current, and represents that the power converter 200 is heavily loaded when the loop control signal VEA is high, and represents that the power converter 200 is lightly loaded when the loop control signal VEA is low.
Referring to fig. 3, the aforementioned control circuit 210 includes, but is not limited to, a first detection unit 211, a second detection unit 212, a logic control unit 213, and a sampling unit 214.
The first detecting unit 211 is configured to provide the first control signal ea_h according to a comparison result between the loop control signal VEA of the voltage loop 230 in the power converter 200 and the first preset threshold Vref 1;
The input end of the sampling unit 214 is connected to the connection node SW and the output end VOUT of the power converter 200, respectively, for providing a voltage detection signal V1, where the voltage detection signal V1 is used for representing the voltage drop generated by the output current at two ends M21;
the second detecting unit 212 is configured to provide a second control signal Vc according to a comparison result of the voltage detecting signal V1 and the second preset threshold Vref 2;
Three input terminals of the logic control unit 213 are respectively connected to the output terminal of the first detection unit 211, the output terminal of the second detection unit 212, and the voltage loop 230, and are used for generating a duty cycle adjusting signal DRC according to logic control of the first control signal ea_h, the second control signal Vc, and the switch control signal PWM provided by the voltage loop 230, and controlling on/off of the M21 and/or M22 by the duty cycle adjusting signal DRC;
Further, in this embodiment, the power converter 200 further includes a driving circuit 220, where the driving circuit 220 is connected to an output terminal of the control circuit 210, and is configured to enhance the driving capability of the duty ratio adjustment signal DRC and output Vg1 received by the control terminal of M21 and Vg2 received by the control terminal of M22, respectively.
Further, the first detecting unit 211 at least includes a comparator 2111, the non-inverting input terminal of the comparator 2111 is connected to the loop control signal VEA, the inverting input terminal is connected to the first preset threshold Vref1, and the output terminal provides the first control signal ea_h.
The loop control signal VEA is used to characterize the magnitude of the output current, and is taken from the voltage loop 230 of the DC/DC switching power supply system. When the power converter 200 operates in the negative half cycle and the loop control signal VEA is higher and greater than the first preset threshold Vref1, the output first control signal ea_h=h is in a high level state, and the loop control signal VEA is lower and less than or equal to the first preset threshold Vref1, the output first control signal ea_h=l is in a low level state.
Further, the second detecting unit 212 includes at least a comparator 2121, wherein a non-inverting input terminal of the comparator 2121 is connected to an output terminal of the sampling unit 214, and is connected to the voltage detecting signal V1, and an inverting input terminal of the comparator is connected to the second preset threshold Vref2, and generates a second control signal Vc according to the voltage detecting signal V1 and the second preset threshold Vref 2.
Further, the logic control unit 213 may control the power converter according to, for example, detecting an operation mode of the power converter, for example, when the power converter 200 is operated in a positive half cycle, the logic control unit 213 only operates according to the switch control signal PWM provided by the voltage loop 230, the input first control signal ea_h and second control signal Vc are inactive, the duty ratio adjusting signal DRC is the same as the switch control signal PWM, and when the power converter 200 is operated in a negative half cycle, the logic control unit 213 inputs the first control signal ea_h and second control signal Vc and provides the duty ratio adjusting signal DRC according to logic control of the first control signal ea_h, second control signal Vc and switch control signal PWM before the output current decreases to zero, so as to control the on-off state of the power switching transistors (M21 and/or M23) connected between the connection node SW and the output terminal VOUT of the power converter 200.
In one embodiment, when the power converter 200 is operating in the positive half-cycle, M23 is on and M21/M22 is off;
When the power converter 200 is operating in the negative half-cycle, the output current Iout flows from the connection node SW to the output VOUT of the power converter 200, delivering energy to the load, the output current Iout decreasing:
1) When the loop control signal VEA is higher and greater than the aforementioned first preset threshold Vref1, the first control signal ea_h=h is in a high level state, and the driving circuit 220 controls both M21 and M22 to be in a conducting state through logic control, at this time, the two power switching transistors are simultaneously turned on, and the conducting impedance is smaller (assuming that the equivalent conducting impedance is 8mohm when the two transistors are simultaneously turned on);
2) When the loop control signal VEA is lower and less than or equal to the aforementioned first preset threshold Vref1, the first control signal ea_h=l is in a low level state, the duty cycle adjusting signal DRC is generated by the logic control of the second control signal Vc and the switch control signal PWM in a high level state, and one of the driving circuits 220 is controlled to be in a conductive state by using the duty cycle adjusting signal DRC, and at this time, only a single power switch tube is turned on, and the on resistance is large (at this time, the equivalent on resistance when a single tube is turned on is, for example, 30 mohm);
3) When the output current Iout decreases and has not reached zero, the on power switching transistor (M21 or M22) is turned off by the detection signal and the judgment result of the preset threshold.
The embodiments of the present disclosure mainly relate to a case where the first control signal ea_h=l is in a low level state, and will be described below by taking the case where the first control signal ea_h is in a low level state as an example.
Specifically, when the first control signal ea_h generated by comparing the loop control signal VEA with the first preset threshold Vref1 is in a low level state, M22 is turned off, and only the conduction of M21 is maintained, so as to increase the on-resistance of the output terminal VOUT.
Assuming that the critical value of the output current Iout of the power converter 200 is 100mA, the critical value of the voltage drop (i.e. the voltage detection signal V1) across the corresponding second power switch tube M22, i.e. the second preset threshold Vref2 is:
Vref2=30mohm*100mA=3mV (1)
If the on-resistance is 30mhom at this time and iout=300 mA, the voltage detection signal:
V1=30mohm*300mA=9mV (2)
9mV >3mV, so that V1 is greater than Vref2, the voltage detection signal V1 is greater than a second preset threshold Vref2, the output of the second comparator 2121 does not flip, and the high level is maintained;
With the continuing decrease of the output current Iout, the voltage difference across the second power switch tube M22 is continuously sampled, when the output current Iout decreases to meet the preset condition (the voltage detection signal V1 decreases to the second preset threshold Vref 2), the output second control signal Vc is turned to a low level, the fast response uses the duty ratio adjusting signal DRC generated by the second control signal Vc to turn off the M22, and the turn-off state of the M21 is maintained, so as to improve the situations of low detection precision and slower response speed in the prior art.
Thereby, the detection accuracy of the output power of the power converter 200 is improved, and the response speed of the power converter 200 to the dynamic change of the load end is improved.
Furthermore, the power converter 200 provided by the present disclosure is not limited to one type of topology, but may be applied to any suitable topology type, including, but not limited to, buck converters (Buck), boost converters (Boost), flyback converters (Flyback), and Buck-Boost converters Buck-Boost, with high applicability and reliability.
In embodiments of the present disclosure, all or part of power converter 200 may be implemented on a single or multiple semiconductor die (commonly referred to as a "chip") or discrete elements. Each die is a monolithic structure formed, for example, from silicon or other suitable material. For embodiments employing multiple dies or components, the dies and components may be assembled on a shared package to form a module, or on a Printed Circuit Board (PCB) having various traces in signal communication therebetween. In one embodiment, for example, an integrated DC-DC buck converter with integrated control circuit 210, first power switch tube M21, second power switch tube M22, and third power switch tube M23 may be implemented on a single chip or die, and the remaining elements, such as inductance L and capacitance, may be implemented on a PCB as discrete elements.
In another aspect, the present invention further provides a control method of a power converter, applied to the power converter 200 provided in the foregoing embodiment, where the power converter 200 includes a power switch tube and an inductor L21 connected to each other, and a control circuit 210 connected to the power switch tube, the control circuit 210 providing a switch control signal PWM for controlling the operation of the power switch tube, so that the inductor L21 charges and discharges to generate an inductor current, thereby providing an output current, and the control method includes:
Before the output current is reduced to zero in the negative half cycle of the power converter operation, the on-off of a power switching tube (M22 and/or M23) connected between the connection node SW and the output end VOUT of the power converter is controlled according to a duty cycle adjusting signal DRC generated by logic control of a control signal generated by sampling the output of the power converter and the switching control signal PWM.
Fig. 4 is a flow chart illustrating a control method of a power converter according to an embodiment of the disclosure.
Referring to fig. 4, the power converter to which the control method is applied is exemplified by the power converter 200 in the above embodiment, and the control method specifically includes:
Step S110, a loop control signal is obtained from a voltage loop of the power converter, and a first control signal is provided according to a comparison result of the loop control signal and a first preset threshold.
In step S110, a loop control signal VEA is obtained from the voltage loop 230 of the power converter 200 by using the first detection unit 211, and then the loop control signal VEA is used to obtain that the loop control signal VEA is smaller than or equal to the first preset threshold Vref1 when the power converter 200 is lightly loaded, so as to generate a low-level first control signal ea_h, and then the first control signal ea_h is used to be conducted with one of the duty ratio adjustment signals DRC control M21 and M22 generated by the switch control signal PWM.
Step S120, obtaining voltage detection signals at two ends of a power switch tube connected between the connection node and the output end of the power converter, and providing a second control signal according to a comparison result of the voltage detection signals and a second preset threshold value.
In step S120, as the output current Iout decreases, the second detection unit 212 continues to sample the differential voltage across the M21, and when the output current Iout decreases to meet the preset condition (the voltage detection signal V1 is less than or equal to the second preset threshold Vref 2), a low-level second control signal Vc is generated, and the second control signal Vc is used to control the duty ratio adjustment signal DRC generated by the first control signal ea_h and the switch control signal PWM logic control, so as to control both M21 and M22 to be turned off.
Wherein the second preset threshold Vref2 is a positive number.
Step S130, generating a duty ratio adjusting signal according to logic control of the first control signal, the second control signal and the switch control signal.
In step S130, before the output current Iout decreases to zero during the negative half cycle of the operation of the power converter 200, the first control signal ea_h and the second control signal Vc are generated according to the output detection of the power converter 200, and the logic control unit 213 in the control circuit 210 is used to logically control the first control signal ea_h, the second control signal Vc and the switching control signal PWM to generate the duty cycle adjusting signal DRC for controlling the on-off state of the first power switching transistor M21 and/or the second power switching transistor M22.
Step S140, outputting the time sequence control of the duty ratio adjusting signal to the control end of the power switch tube connected between the inductor and the output end of the power converter.
In step S140, the driving circuit 220 outputs the duty cycle adjusting signal DRC as the first switching signal Vg1 received by the control terminal of M21 and the second switching signal Vg2 received by the control terminal of M22, respectively, and the duty cycle adjusting signal DRC determines the on period of the first switching signal Vg1 and the on period of the second switching signal Vg2, so as to complete the fast response to turn off M21 and M22 successively before the output current Iout decreases to zero when the power converter 200 operates in the negative half cycle, thereby improving the efficiency of the power converter 200.
In summary, the power converter and the control method thereof provided by the present disclosure can switch off M21 and M22 connected between the inductor and the output end of the power converter in time through the detection signal and the judgment result of the two-stage preset threshold before the output current Iout is reduced to be close to zero but not reach zero in the process that the power converter 200 works in the negative half cycle to output power to the load output end VOUT, so as to improve the accurate detection of the small current at the output end and the response speed, thereby improving the situation that the power switch tube cannot be turned off in time due to low detection accuracy and slow system response speed in the prior art, resulting in the generation of reverse current and reducing the efficiency of the power converter. Thereby improving the accuracy of detection of the output power of the power converter and also improving the efficiency of the power converter 200.
It should be noted that in the description of the present disclosure, it should be understood that the terms "upper," "lower," "inner," and the like indicate an orientation or a positional relationship, and are merely for convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the components or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present disclosure.
Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element.
Finally, it should be noted that the above-mentioned examples are given for the purpose of illustration only and are not intended to limit the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. And obvious variations or modifications thereof are contemplated as falling within the scope of the present disclosure.
Claims (9)
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| EP3847741A4 (en) * | 2018-09-06 | 2022-05-25 | Cornell University | High power density power converter and uninterruptible power supply circuit and methods |
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