Power converter and control method thereof

Abstract

The present 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 and an inductor, and a control circuit, and the power switch tube at least comprises: a first power switch tube connected between the aforementioned inductor and the output end of the power converter, a second power switch tube connected in parallel at both ends of the first power switch tube, and a third power switch tube located between the connection node of the aforementioned inductor and the first power switch tube and the ground, wherein the power converter operates in a negative half cycle, and before the output current decreases to zero, the control circuit controls the on-off state of the power switch tube connected between the aforementioned 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 cycle adjustment signal generated by logical control of the switch control signal. This can improve the detection accuracy of the output power and improve the efficiency of the power converter.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and particularly to a power converter and a control method thereof. Background Art

[0002] DC / DC switching power supply circuits are applied in various fields, and among them, the power converter is an important part of the DC / DC switching power supply. With the development of technology, the functions of DC / DC switching power supply circuits are becoming more and more diverse and complex, and the output power of the power converter system is also increasing.

[0003] In the DC / DC switching power supply circuit, taking the boost-type power converter (Boost) as an example, as Figure 1 shown, the boost-type power converter 100 includes: an inductor L and a power transistor M11 connected between the input terminal VIN and the output terminal VOUT, a power transistor M12 connected between the inductor L and the ground, and a control circuit 110 and a drive circuit 120 connected to the power transistor M11. There is a connection node SW between the inductor L and the power transistor M11. The control circuit 110 obtains a detection signal according to the detected voltage difference (assumed to be V1) across the power transistor M11, and provides a switching control signal PWM according to the detection signal. The drive circuit 120 generates a control signal Vg for the power transistor M11 according to the switching control signal PWM. Among them, at the input terminal VIN, the inductor current IL in the 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 decreases; and the current on the inductor cannot change suddenly, so when the inductor current IL becomes small to zero, it will reverse and flow from the output terminal VOUT to the connection node SW. At this time, the reverse灌 current will reduce the efficiency of this power converter.

[0004] In order to improve the efficiency of the power converter, when the inductor current IL is small and close to zero but has not reached zero, that is, the detected 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 a small on-resistance, the detected voltage V1 is very small. For example: IL = 100 mA, RON = 8 mohm, V1 = 0.8 mV. For the comparator in the detection circuit 110 used to compare V1 and V0, usually the self-offset voltage (VOS) of the comparator is 1 mV, and it is simply impossible to accurately judge the voltage difference of 0.8 mV. And when the preset voltage V0 is relatively small, the overdrive voltage of the comparator is also relatively small, resulting in a slower switching speed and a longer delay time of the comparator, which will also cause the upper transistor to fail to be turned off in time, generating a reverse灌 current and reducing the efficiency of the power converter. Summary of the Invention

[0005] 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 the output power and improve the efficiency of the power converter.

[0006] In one aspect, the present disclosure provides a power converter, the power converter comprising a power switch tube and an inductor connected to each other, and a control circuit connected to the power switch tube, the control circuit providing a switch control signal for controlling the operation of the power switch tube, so that the inductor is charged and discharged to generate an inductor current, thereby providing an output current, wherein the power switch tube at least comprises:

[0007] A first power switch tube is connected between the inductor and the output end of the power converter;

[0008] A second power switch tube is connected in parallel to two ends of the first power switch tube;

[0009] The third power switch tube is located between the connection node between the inductor and the first power switch tube and the ground.

[0010] The power converter operates in the negative half cycle. Before the aforementioned output current decreases to zero, the control circuit controls the on-off state of the power switch tube connected between the aforementioned connection node and the output end of the power converter based on the control signal generated by output sampling of the power converter and the duty cycle adjustment signal generated by the logic control of the aforementioned switch control signal.

[0011] Preferably, the loop control signal taken from the voltage loop of the power converter is less than or equal to a first preset threshold, and one of the first power switch tube and the second power switch tube is in a conducting state;

[0012] The voltage detection signal is less than or equal to the second preset threshold value, the first power switch tube and the second power switch tube are both in the off state, and the voltage detection signal is used to represent the voltage drop generated by the output current at both ends of the first power switch tube.

[0013] And the aforementioned second preset threshold is a positive number.

[0014] Preferably, the aforementioned control signal includes at least a first control signal and a second control signal;

[0015] And the aforementioned control circuit includes:

[0016] A first detection unit, configured to provide the first control signal according to a comparison result between a loop control signal obtained from a voltage loop of the power converter and the first preset threshold;

[0017] A sampling unit, used for generating the aforementioned voltage detection signal according to the voltage difference between the aforementioned connection node and the output end of the power converter;

[0018] a second detection unit connected to the output end of the sampling unit, and configured to provide the second control signal according to a comparison result between the voltage detection signal and the second preset threshold;

[0019] A logic control unit, which is respectively connected to the output end of the first detection unit and the output end of the second detection unit, and is used to generate a duty cycle adjustment signal according to the logic control of the first control signal, the second control signal and the switch control signal, so that when the power converter operates in the negative half cycle, the duty cycle adjustment signal is used to control the shutdown of the first power switch tube and / or the second power switch tube.

[0020] Preferably, the first detection unit comprises:

[0021] A first comparator, wherein the non-inverting input terminal of the first comparator is connected to the aforementioned loop control signal, the inverting input terminal is connected to the aforementioned first preset threshold, and the output terminal provides the aforementioned first control signal,

[0022] And the loop control signal is used to indicate whether the power converter working in the negative half cycle is lightly loaded or heavily loaded.

[0023] Preferably, the second detection unit comprises:

[0024] A second comparator, wherein the non-inverting input terminal of the second comparator is connected to the output terminal of the sampling unit and connected to the voltage detection signal, the inverting input terminal is connected to the second preset threshold, and the output terminal is used to provide the second control signal.

[0025] Preferably, the aforementioned control circuit further includes:

[0026] A driving circuit is connected to the output end of the control circuit, and is used to enhance the driving capability of the duty cycle adjustment signal and output it to the control end of the first power switch tube and the control end of the second power switch tube respectively.

[0027] 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.

[0028] On the other hand, the present disclosure also provides a control method for a power converter, the power converter comprising a power switch tube and an inductor connected to each other, and a control circuit connected to the power switch tube, the control circuit providing a switch control signal for controlling the operation of the power switch tube, so that the inductor is charged and discharged to generate an inductor current, thereby providing an output current, wherein the control method comprises:

[0029] When the power converter operates in the negative half cycle, before the output current decreases to zero, the on and off of the power switch tube connected between the aforementioned connection node and the output end of the power converter is controlled based on the control signal generated by output sampling of the power converter and the duty cycle adjustment signal generated by the logic control of the aforementioned switch control signal.

[0030] Preferably, the aforementioned control signal includes at least a first control signal and a second control signal;

[0031] The step of controlling the on / off of the power switch tube connected between the connection node and the output end of the power converter by using the control signal generated by the output sampling of the power converter and the duty cycle adjustment signal generated by the logic control of the switch control signal comprises:

[0032] Providing the first control signal according to a comparison result of a loop control signal taken from a voltage loop of the power converter and the aforementioned first preset threshold, the loop control signal being used to characterize whether the power converter operating in a negative half cycle is lightly loaded or heavily loaded;

[0033] Generate a voltage detection signal according to the voltage difference between the aforementioned connection node and the output end of the power converter, and provide the second control signal according to the comparison result of the voltage detection signal and the aforementioned second preset threshold, wherein the voltage detection signal is used to represent the voltage drop generated by the aforementioned output current at both ends of the aforementioned first power switch tube;

[0034] According to the logic control of the aforementioned first control signal, the second control signal and the aforementioned switch control signal, the aforementioned duty cycle adjustment signal is generated, and before the aforementioned output current decreases to zero in the negative half cycle, the duty cycle adjustment signal is used to control the conduction and shutdown of the aforementioned first power switch tube and / or the aforementioned second power switch tube.

[0035] Preferably, the step of controlling the shutdown of the first power switch tube and / or the second power switch tube by using the duty cycle adjustment signal comprises:

[0036] When the loop control signal is less than the first preset threshold, the duty cycle adjustment signal is used to control one of the first power switch tube and the second power switch tube to be turned on;

[0037] When the voltage detection signal is less than the second preset threshold, the duty cycle adjustment signal is used to control the first power switch tube and the second power switch tube to be turned off.

[0038] And the aforementioned second preset threshold is a positive number.

[0039] The beneficial effect of the present invention is as follows: the present disclosure provides a power converter and a control method thereof, wherein the power converter comprises a power switch tube and an inductor connected to each other, and a control circuit connected to the power switch tube, and the power switch tube at least comprises: a first power switch tube connected between the aforementioned inductor and the output end of the power converter, a second power switch tube connected in parallel at both ends of the first power switch tube, and a third power switch tube located between the connection node between the aforementioned inductor and the first power switch tube and the ground, wherein the power converter operates in a negative half cycle, and before the aforementioned output current decreases to zero, the control circuit controls the on-off state of the power switch tube connected between the aforementioned connection node and the output end of the power converter according to a control signal generated by output sampling of the power converter and a duty cycle adjustment signal generated by logical control of the aforementioned switch control signal. When detecting the output power (output current), the power converter uses two parallel power switch tubes to reduce the on-resistance of the output end, so as to expand the detection accuracy range of the output current. When the output current decreases but does not reach zero, the power switch tube connected between the inductor and the output end of the power converter is timely turned off through the judgment result of the detection signal and the two-stage preset threshold value, so as to improve the accurate detection of the small current at the output end. Specifically, when it is known through the system feedback (voltage loop) that the power converter is under light load (the loop control signal is less than the first preset threshold), one of the first power switch tube and the second power switch tube is controlled to be turned on to increase the on-resistance of the output end, and then the voltage difference across the second power switch tube (or the first power switch tube) is sampled. When the output current decreases to meet the preset condition (the voltage detection signal is less than or equal to the second preset threshold), the turned-on second power switch tube (or the first power switch tube) is quickly responded and then turned off, so as to improve the situation in the prior art that the power switch tube cannot be turned off in time due to low detection accuracy and slow system response speed, resulting in the generation of reverse current and thus reducing the efficiency of the power converter. This improves the detection accuracy of the output power of the power converter and also improves the efficiency of the power converter.

[0040] In addition, the power converter provided by the present invention is not limited to one type of topology, but can be applied to any suitable topology type, including but not limited to buck converter (Buck), boost converter (Boost), flyback converter (Flyback) and buck-boost converter (BUCK-BOOST), with strong applicability and high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings.

[0042] Figure 1 A schematic diagram showing the structure of a boost power converter disclosed in the prior art is shown;

[0043] Figure 2 A schematic structural diagram of a boost power converter provided by an embodiment of the present disclosure is shown;

[0044] Figure 3 Show Figure 2 A schematic diagram of the structure of a control circuit in the power converter shown;

[0045] Figure 4 A flow chart of a method for controlling a power converter provided in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0046] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The drawings provide preferred embodiments of the present disclosure. However, the present disclosure can be implemented in different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the present disclosure more thorough and comprehensive.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0048] In various embodiments, the present disclosure provides or realizes an improved technology for detecting output current (inductor current) in a power device of a power converter system (e.g., a DC-DC converter) with high precision, high speed and good transient on-off characteristics. Unlike some previously formed technologies, the technology according to an embodiment of the present invention does not require accurate detection resistors, can be operated at high speeds, and has good transient characteristics, making them very suitable for high-frequency power conversion. The current detection technology in various embodiments can be used for various functions or characteristics, such as current mode control or current protection in a power converter system.

[0049] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

[0050] Figure 2 A schematic diagram of the structure of a boost power converter provided by an embodiment of the present disclosure is shown. Figure 3 Show Show Figure 2 Schematic diagram of the structure of the control circuit in the power converter shown.

[0051] On the one hand, the present disclosure provides a power converter, which can be used in a DC / DC switching power supply circuit. Figure 2 and Figure 3The 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, located between an input terminal VIN and an output terminal VOUT. The control circuit 210 provides a switch control signal PWM for controlling the operation of the power switch tube, so that the inductor L21 is charged and discharged to generate an inductor current, thereby providing an output current. The power switch tube at least includes: a first power switch tube M21 connected between the inductor L21 and the output terminal VOUT of the power converter 200, a second power switch tube M22 connected in parallel at both ends of the first power switch tube M21, and a third power switch tube M23 located between a connection node SW between the inductor L21 and the first power switch tube M21 and ground.

[0052] And when the power converter 200 operates in the negative half cycle, before the aforementioned output current decreases to zero, the control circuit 210 can control the on-off state of the power switch tube (M21 and / or M22) connected between the aforementioned connection node SW and the output end VOUT of the power converter 200 based on the control signal generated by the output sampling of the power converter 200 and the duty cycle adjustment signal DRC generated by the logic control of the aforementioned switch control signal PWM.

[0053] Furthermore, 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). In the present embodiment, the first power switch tube M21, the second power switch tube M22 and the third power switch tube M23 are all NMOS tubes (hereinafter referred to as M21, M22 and M22 respectively).

[0054] 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 the first preset threshold, and one of M21 and M22 is in the on state; the voltage detection signal V1 is less than or equal to the second preset threshold, and both M21 and M22 are in the off state.

[0055] Among them, the aforementioned second preset threshold is a positive number, and the voltage detection signal is used to characterize the voltage drop generated by the aforementioned output current at both ends of M21, and when the loop control signal VEA is higher, it characterizes that the power converter 200 is overloaded; when the loop control signal VEA is lower, it characterizes that the power converter 200 is lightly loaded.

[0056] refer to Figure 3 The 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 .

[0057] The first detection unit 211 is used to provide the first control signal EA_H according to the comparison result between the loop control signal VEA obtained from the voltage loop 230 in the power converter 200 and the first preset threshold Vref1;

[0058] The input terminal of the sampling unit 214 is respectively connected to the aforementioned connection node SW and the output terminal VOUT of the power converter 200 to provide a voltage detection signal V1, and the voltage detection signal V1 is used to represent the voltage drop generated by the aforementioned output current at both ends of M21;

[0059] The second detection unit 212 is used to provide a second control signal Vc according to a comparison result between the voltage detection signal V1 and the aforementioned second preset threshold value Vref2;

[0060] The 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 aforementioned voltage loop 230, and are used to generate a duty cycle adjustment signal DRC according to the 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 control the on and off of M21 and / or M22 with the duty cycle adjustment signal DRC;

[0061] Furthermore, in this embodiment, the power converter 200 also includes a drive circuit 220, which is connected to the output end of the control circuit 210, and is used to enhance the driving capability of the duty cycle adjustment signal DRC and output it as Vg1 received by the M21 control end and Vg2 received by the M22 control end respectively.

[0062] Furthermore, the first detection unit 211 at least includes a comparator 2111 , a non-inverting input terminal of the comparator 2111 is connected to the aforementioned loop control signal VEA, an inverting input terminal is connected to the first preset threshold Vref1 , and an output terminal provides a first control signal EA_H.

[0063] The loop control signal VEA is used to characterize the magnitude of the output current, and the loop control signal VEA 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, when the loop control signal VEA is higher and greater than the aforementioned first preset threshold value Vref1, the output first control signal is EA_H=H, which is a high level state; when the loop control signal VEA is lower and less than or equal to the aforementioned first preset threshold value Vref1, the output first control signal is EA_H=L, which is a low level state.

[0064] Furthermore, the second detection unit 212 at least includes a comparator 2121, wherein the in-phase input terminal of the comparator 2121 is connected to the output terminal of the sampling unit 214 and connected to the aforementioned voltage detection signal V1, and the inverting input terminal is connected to the aforementioned second preset threshold value Vref2, and the second control signal Vc is generated based on the comparison between the voltage detection signal V1 and the aforementioned second preset threshold value Vref2.

[0065] Furthermore, the logic control unit 213 can, for example, control the power converter according to the working mode detected. For example, when the power converter 200 operates in the positive half cycle, the logic control unit 213 only operates according to the switch control signal PWM provided by the aforementioned voltage loop 230, and the input first control signal EA_H and the second control signal Vc are invalid. At this time, the duty cycle adjustment signal DRC is the same as the switch control signal PWM; when the power converter 200 operates in the negative half cycle, the first control signal EA_H and the second control signal Vc input by the logic control unit 213 are valid, and before the aforementioned output current decreases to zero, the duty cycle adjustment signal DRC is provided according to the logic control of the first control signal EA_H, the second control signal Vc and the switch control signal PWM to control the on-off state of the power switch tube (M21 and / or M23) connected between the aforementioned connection node SW and the output end VOUT of the power converter 200.

[0066] In a specific embodiment, when the power converter 200 operates in the positive half cycle, M23 is turned on and M21 / M22 is turned off;

[0067] When the power converter 200 operates in the negative half cycle, the output current Iout flows from the connection node SW to the output terminal VOUT of the power converter 200, transfers energy to the load, and the output current Iout decreases:

[0068] 1) When the loop control signal VEA is high and greater than the aforementioned first preset threshold value Vref1, the first control signal EA_H=H, which is in a high level state. Through logic control, the drive circuit 220 controls M21 and M22 to be in a conducting state. At this time, the two power switch tubes are turned on at the same time, and the conduction impedance is small (assuming that the equivalent conduction impedance when the two tubes are turned on at the same time is 8mohm);

[0069] 2) When the loop control signal VEA is low and less than or equal to the aforementioned first preset threshold value Vref1, the first control signal EA_H=L, which is in a low level state, and the duty cycle adjustment signal DRC is generated by logical control with the second control signal Vc in a high level state and the switch control signal PWM. The duty cycle adjustment signal DRC is used to make the drive circuit 220 control one of M21 and M22 to be in a conducting state. 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 of a single tube when it is turned on is, for example, 30mohm);

[0070] 3) When the output current Iout decreases but has not yet reached zero, the aforementioned turned-on power switch tube (M21 or M22) is turned off through the judgment result of the detection signal and the preset threshold.

[0071] The embodiments of the present disclosure mainly involve the case where the first control signal EA_H=L, that is, the state of the low level. The following description will be made by taking the state of the first control signal EA_H being the low level as an example.

[0072] 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 M21 is kept turned on to increase the on-resistance of the output terminal VOUT.

[0073] Assuming that the critical value of the output current Iout of the power converter 200 is 100 mA, the corresponding critical value of the voltage drop across the second power switch tube M22 (ie, the voltage detection signal V1), ie, the second preset threshold value Vref2 is:

[0074] Vref2=30mohm*100mA=3mV (1)

[0075] If the on-resistance is 30mhom, Iout=300mA, then the voltage detection signal is:

[0076] V1=30mohm*300mA=9mV (2)

[0077] 9mV>3mV, so V1>Vref2, the voltage detection signal V1 is greater than the second preset threshold Vref2, the output of the second comparator 2121 does not flip, and maintains a high level;

[0078] As the output current Iout continues to decrease, the voltage difference across the second power switch tube M22 continues to be sampled. When the output current Iout decreases to meet the preset condition (the voltage detection signal V1 decreases to the second preset threshold value Vref2), the output second control signal Vc is flipped to a low level, and the duty cycle adjustment signal DRC generated by the second control signal Vc is quickly responded to to turn off M22, and maintain the off state of M21, thereby improving the low detection accuracy and slow response speed in the prior art.

[0079] This improves the detection accuracy of the output power of the power converter 200 and improves the response speed of the power converter 200 to dynamic changes at the load end.

[0080] In addition, the power converter 200 provided by the present disclosure is not limited to one type of topology, but can be applied to any suitable topology type, including but not limited to a buck converter (Buck), a boost converter (Boost), a flyback converter (Flyback) and a buck-boost converter BUCK-BOOST, and has strong applicability and high reliability.

[0081] In an embodiment of the present disclosure, all or part of the power converter 200 may be implemented on a single or multiple semiconductor die (commonly referred to as a "chip") or discrete components. Each die is a monolithic structure formed, for example, by silicon or other suitable materials. For embodiments using multiple dies or components, these dies and components may be assembled on a shared package to form a module, or assembled on a printed circuit board (PCB) having various tracks for signal communication therebetween. In one embodiment, for example, an integrated DC-DC buck converter having an integrated control circuit 210, a first power switch tube M21, a second power switch tube M22, and a third power switch tube M23 may be implemented on a single chip or die, and the remaining components such as an inductor L and a capacitor may be implemented on a PCB as discrete components.

[0082] On the other hand, the present invention further provides a control method for a power converter, which is applied to the power converter 200 provided in the above embodiment. 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 provides a switch control signal PWM for controlling the operation of the power switch tube, so that the inductor L21 is charged and discharged to generate an inductor current, thereby providing an output current. The control method includes:

[0083] In the negative half cycle of the power converter, before the output current decreases to zero, the power switch tube (M22 and / or M23) connected between the connection node SW and the output terminal VOUT of the power converter is controlled to be turned on and off according to the control signal generated by the output sampling of the power converter and the duty cycle adjustment signal DRC generated by the logic control of the switch control signal PWM.

[0084] Figure 4 A flow chart of a method for controlling a power converter provided in an embodiment of the present disclosure is shown.

[0085] refer to Figure 4 The power converter to which the control method is applied takes the power converter 200 in the above embodiment as an example, and the control method specifically includes:

[0086] Step S110: Obtain a loop control signal from the voltage loop of the power converter, and provide a first control signal according to a comparison result between the loop control signal and a first preset threshold.

[0087] In step S110, the first detection unit 211 is used to obtain the loop control signal VEA from the voltage loop 230 of the power converter 200, and then the loop control signal VEA is used to determine that the power converter 200 is lightly loaded, that is, the loop control signal VEA is less than or equal to the first preset threshold value Vref1, and a low-level first control signal EA_H is generated. Then, the duty cycle adjustment signal DRC generated by the first control signal EA_H and the switch control signal PWM is used to control one of M21 and M22 to turn on.

[0088] Step S120: obtaining a voltage detection signal at both ends of the power switch tube connected between the aforementioned 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 signal with a second preset threshold.

[0089] In step S120, as the output current Iout decreases, the second detection unit 212 continues to sample the voltage difference across M21. 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 Vref2), a low-level second control signal Vc is generated. The duty cycle adjustment signal DRC generated by the second control signal Vc and the aforementioned first control signal EA_H and the switch control signal PWM logic control is used to control both M21 and M22 to be turned off.

[0090] The second preset threshold Vref2 is a positive number.

[0091] Step S130: Generate a duty cycle adjustment signal according to the logic control of the first control signal, the second control signal and the switch control signal.

[0092] In step S130, in the negative half cycle of the power converter 200, before the output current Iout decreases to zero, 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 then the logic control unit 213 in the control circuit 210 performs logical control on the first control signal EA_H, the second control signal Vc and the switch control signal PWM to generate the duty cycle adjustment signal DRC, which is used to control the on / off state of the first power switch tube M21 and / or the second power switch tube M22.

[0093] Step S140: The duty cycle adjustment signal is controlled to be output to the control terminal of the power switch tube connected between the inductor and the output terminal of the power converter.

[0094] In step S140, the driving circuit 220 is used to control the duty cycle adjustment signal DRC timing to output the first switch signal Vg1 received by the M21 control terminal and the second switch signal Vg2 received by the M22 control terminal, and the duty cycle adjustment signal DRC determines the conduction period of the first switch signal Vg1 and the conduction period of the second switch signal Vg2, so as to complete the quick response to successively turn off M21 and M22 when the output current Iout decreases to zero before it reaches zero when the power converter 200 operates in the negative half cycle, thereby improving the efficiency of the power converter 200.

[0095] In summary, the power converter and control method provided by the present disclosure can timely shut down M21 and M22 connected between the aforementioned inductor and the output terminal of the power converter through the judgment result of the detection signal and the two-stage preset threshold value when the power converter 200 is working in the negative half-cycle to output power to the load output terminal VOUT, thereby improving the accurate detection of small currents at the output terminal and improving the response speed, thereby improving the situation in the prior art where the power switch tube is not turned off in time due to low detection accuracy and slow system response speed, resulting in the generation of reverse injection current and reducing the efficiency of the power converter. Thereby, the detection accuracy of the output power of the power converter is improved, and the efficiency of the power converter 200 is also improved.

[0096] It should be noted that in the description of the present disclosure, it needs to be understood that the terms "upper", "lower", "inner" and the like indicating orientation or positional relationship are only for the 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 constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present disclosure.

[0097] In addition, in this article, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device that includes the element.

[0098] Finally, it should be noted that: Obviously, the above embodiments are only examples for clearly illustrating the present disclosure, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from this are still within the scope of protection of the present disclosure.

Claims

1. A power converter, comprising a power switch tube and an inductor connected to each other, and a control circuit connected to the power switch tube, wherein the control circuit provides a switch control signal for controlling the operation of the power switch tube, so that the inductor is charged and discharged to generate an inductor current, thereby providing an output current, wherein: The power switch tube at least includes: A first power switch tube, connected between the inductor and the output end of the power converter; A second power switch tube is connected in parallel to two ends of the first power switch tube; A third power switch tube is located between a connection node between the inductor and the first power switch tube and ground, The power converter operates in a negative half cycle. Before the output current decreases 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 the control signal generated by sampling the output of the power converter and the duty cycle adjustment signal generated by logical control of the switch control signal. Wherein, the loop control signal taken from the voltage loop of the power converter is less than or equal to a first preset threshold, and one of the first power switch tube and the second power switch tube is in a conducting state; The voltage detection signal is less than or equal to a second preset threshold value, the first power switch tube and the second power switch tube are both in an off state, and the voltage detection signal is used to characterize the voltage drop generated by the output current at both ends of the first power switch tube. And the second preset threshold is a positive number.

2. The power converter according to claim 1, wherein: The control signal includes at least a first control signal and a second control signal; And the control circuit includes: a first detection unit, configured to provide the first control signal according to a comparison result between a loop control signal obtained from a voltage loop of the power converter and the first preset threshold; a sampling unit, configured to generate the voltage detection signal according to a voltage difference between the connection node and an output terminal of the power converter; a second detection unit connected to the output end of the sampling unit, and configured to provide the second control signal according to a comparison result between the voltage detection signal and the second preset threshold; A logic control unit, the logic control unit is respectively connected to the output end of the first detection unit and the output end of the second detection unit, and is used to generate a duty cycle adjustment signal according to the logic control of the first control signal, the second control signal and the switch control signal, so that when the power converter operates in the negative half cycle, the duty cycle adjustment signal is used to control the on and off of the first power switch tube and / or the second power switch tube.

3. The power converter according to claim 2, wherein: The first detection unit comprises: a first comparator, wherein a non-inverting input terminal of the first comparator is connected to the loop control signal, an inverting input terminal is connected to the first preset threshold, and an output terminal provides the first control signal, The loop control signal is used to indicate whether the power converter operating in the negative half cycle is lightly loaded or heavily loaded.

4. The power converter according to claim 2, wherein: The second detection unit comprises: A second comparator, wherein the non-inverting input terminal of the second comparator is connected to the output terminal of the sampling unit and connected to the voltage detection signal, the inverting input terminal is connected to the second preset threshold, and the output terminal is used to provide the second control signal.

5. The power converter according to claim 4, wherein: The control circuit further comprises: A driving circuit is connected to the output end of the control circuit and is used to enhance the driving capability of the duty cycle adjustment signal and output it to the control end of the first power switch tube and the control end of the second power switch tube respectively.

6. The power converter according to claim 1, wherein: 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.

7. A control method for a power converter according to any one of claims 1 to 6, wherein the power converter comprises a power switch tube and an inductor connected to each other, and a control circuit connected to the power switch tube, wherein the control circuit provides a switch control signal for controlling the operation of the power switch tube, so that the inductor is charged and discharged to generate an inductor current, thereby providing an output current, wherein: The control method comprises: When the power converter operates in the negative half cycle, before the output current decreases to zero, the on and off of the power switch tube connected between the connection node between the inductor and the first power switch tube and the output end of the power converter is controlled according to the control signal generated by output sampling of the power converter and the duty cycle adjustment signal generated by the logic control of the switch control signal.

8. The control method of the power converter according to claim 7, wherein: The control signal includes at least a first control signal and a second control signal; The step of controlling the on / off of the power switch tube connected between the connection node and the output end of the power converter according to the control signal generated by sampling the output of the power converter and the duty cycle adjustment signal generated by logic control of the switch control signal comprises: Providing the first control signal according to a comparison result between a loop control signal obtained from a voltage loop of the power converter and a first preset threshold value; generating a voltage detection signal according to a voltage difference between the connection node and the output end of the power converter, and providing the second control signal according to a comparison result of the voltage detection signal and a second preset threshold, wherein the voltage detection signal is used to characterize a voltage drop generated by the output current at both ends of the first power switch tube; and A duty cycle adjustment signal is generated according to the logic control of the first control signal, the second control signal and the switch control signal, and before the output current decreases to zero in the negative half cycle, the duty cycle adjustment signal is used to control the conduction and shutdown of the first power switch tube and / or the second power switch tube connected in parallel at both ends of the first power switch tube.

9. The control method of the power converter according to claim 8, wherein: The step of controlling the shutdown of the first power switch tube and / or the second power switch tube by using the duty cycle adjustment signal comprises: When the loop control signal is less than the first preset threshold, the duty cycle adjustment signal is used to control one of the first power switch tube and the second power switch tube to be turned on; When the voltage detection signal is less than the second preset threshold, the duty cycle adjustment signal is used to control the first power switch tube and the second power switch tube to be turned off. And the second preset threshold is a positive number.

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