Auxiliary circuit and power supply system

Abstract

The utility model discloses an auxiliary circuit and a power supply system, the auxiliary circuit is applied to the power supply system with a transformer and an X capacitor, the transformer is at least provided with an auxiliary winding and a primary winding, and the auxiliary circuit comprises a sampling module, the auxiliary winding and an auxiliary module; by controlling the state of the second power switch, the auxiliary circuit at least enables the X capacitor of the power supply system to rapidly discharge when the power supply system is powered down. Compared with the prior art, the efficiency of the power supply system is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of power conversion, in particular to an auxiliary circuit and a power system. Background Art

[0002] In switching power supply products, in order to improve the electromagnetic interference (EMI) characteristics of the switching power supply, it is necessary to add a filtering network to the AC input end before the rectifier bridge of the switching power supply. The X capacitor is an important component of the filtering network. The X capacitor can effectively filter out the differential mode interference from the bus AC voltage. However, after the X capacitor is added to improve EMI, at the moment when the AC voltage is disconnected, there may be a large amount of charge in the X capacitor that needs to be discharged in time, otherwise there will be a risk of electric shock to the human body. For example, after the power plug of the electrical appliance is unplugged, the human body accidentally touches the power plug of the electrical appliance immediately. If the voltage on the X capacitor has not been discharged to the human body safety voltage at this time, it will cause electric shock to the human body. The usual practice of discharging the X capacitor in the prior art is to connect a resistor in parallel to the X capacitor, and this method will also cause large losses when the switching power supply is working normally, especially in the current market environment that pursues low standby power consumption. The parallel resistor discharge method is difficult to simultaneously meet the requirements of fast discharge of the X capacitor and low standby power consumption of the switching power supply. Therefore, it is necessary to improve the shortcomings of the prior art. Utility Model Content

[0003] In a first aspect, the utility model provides an auxiliary circuit, which is applied to a power supply system having a transformer and an X capacitor, wherein the transformer has at least an auxiliary winding and a primary winding, and the auxiliary circuit comprises:

[0004] a sampling module, coupled to the X capacitor, configured to sample the voltage on the X capacitor and output the sampled voltage;

[0005] An auxiliary winding having two ends, wherein a first end is coupled to the sampling voltage, or coupled to the sampling voltage after passing through a capacitor;

[0006] an auxiliary module, coupled to the second end of the auxiliary winding, and comprising at least a second power switch;

[0007] By controlling the state of the second power switch, the auxiliary circuit enables the X capacitor of the power system to discharge quickly when the power system loses power.

[0008] Preferably, the auxiliary circuit can also provide an electrical voltage for external power supply, or the auxiliary circuit can also detect the demagnetization state of the transformer and output a demagnetization signal indicating that the demagnetization of the transformer has ended.

[0009] Preferably, the sampling module comprises a first sampling diode, a second sampling diode and a holding capacitor, wherein an anode of the first sampling diode is coupled to a first end of the X capacitor, an anode of the second sampling diode is coupled to a second end of the X capacitor, a cathode of the first sampling diode and a cathode of the second sampling diode are coupled to the holding capacitor, and the sampling voltage is generated on the holding capacitor.

[0010] Preferably, the auxiliary module has at least two ports, a first port is coupled to the second end of the auxiliary winding, and a second port is coupled to a second control signal, and the second control signal controls the on and off of the second power switch.

[0011] Preferably, the auxiliary module includes a second power switch and a power supply capacitor, a first end of the second power switch is coupled to a first port of the auxiliary module, a control end of the second power switch is coupled to a second port of the auxiliary module, a second end of the second power switch is coupled to the power supply capacitor and outputs a power supply voltage to supply power externally, and when the power supply system loses power, the second power switch transfers energy on the X capacitor to the power supply capacitor to generate a power supply voltage to supply power externally, and simultaneously realizes rapid discharge of the X capacitor; or

[0012] The auxiliary module includes a second power switch, a normally-on switch, a power supply capacitor and a detection module, wherein a first end of the normally-on switch is coupled to a first port of the auxiliary module, a second end of the normally-on switch is coupled to a first end of the second power switch, a control end of the normally-on switch is coupled to the detection module, and the detection module outputs a demagnetization signal indicating that demagnetization of the transformer is completed by detecting the control end of the normally-on switch; the control end of the second power switch is coupled to a second port of the auxiliary module, a second end of the second power switch is coupled to the power supply capacitor and outputs a power supply voltage for external power supply, and when the power supply system loses power, the second power switch and the normally-on switch transfer the energy on the X capacitor to the power supply capacitor to generate a power supply voltage for external power supply, and simultaneously realize rapid discharge of the X capacitor.

[0013] Preferably, before the auxiliary circuit starts charging the primary winding of the transformer, the second power switch is first turned on for a part or all of a pulse time, so that the current flowing through the second power switch flows through the auxiliary winding.

[0014] Preferably, the primary winding of the transformer is connected in series with the first power switch, the auxiliary winding and the primary winding have the same-named ends at the same position, the second power switch is turned on for a part or all of a pulse time before the first power switch switches from the off state to the on state, and the current flows into the auxiliary winding, and through the coupling relationship between the primary winding and the auxiliary winding of the transformer, the voltage across the first power switch is reduced from a first potential when the first power switch is turned off to a lower second potential, and then the first power switch is switched from the off state to the on state, so that the switching loss of the first power switch is lower; or

[0015] The primary winding of the transformer is connected in series with the first power switch, and the auxiliary winding has the same-named ends in opposite positions with the primary winding. During a first period of a pulse time before the first power switch switches from the off state to the on state, the second power switch is turned on, and current flows into the auxiliary winding. Through the coupling relationship between the primary winding and the auxiliary winding of the transformer, the voltage across the first power switch rises from the potential when the first power switch is turned off to the first potential; during a second period of a pulse time before the first power switch switches from the off state to the on state, the second power switch is turned off. Through the coupling relationship between the primary winding and the auxiliary winding of the transformer, the voltage across the first power switch decreases from the first potential to a lower second potential, and then the first power switch switches from the off state to the on state, so that the switching loss of the first power switch is lower.

[0016] In the second aspect, the utility model provides a power supply system, comprising at least the auxiliary circuit described in any one of the first aspect, the power supply system also comprising an input capacitor, an output capacitor, a control module and a power stage; the power stage at least comprises a primary winding of a transformer, a first power switch and a freewheeling module, the first control signal output by the control module is coupled to the control end of the first power switch to control the conduction and cutoff of the first power switch; the second control signal output by the control module is coupled to the control end of the second power switch to control the conduction and cutoff of the second power switch; the connection relationship between the power stage and the input capacitor and the output capacitor can be combined to form any one of a step-down power supply system, a step-up power supply system, a flyback power supply system and a step-up / step-down power supply system.

[0017] Preferably, before the control module controls the first power switch to switch from the off state to the on state, it controls the second power switch in the auxiliary circuit to first turn on a part or all of a pulse time, so that the current flowing through the second power switch flows through the auxiliary winding.

[0018] Preferably, the auxiliary winding of the transformer of the power supply system has the same-named end at the same position as the main winding, and the second power switch is turned on for part or all of a pulse time before the first power switch is switched from the off state to the on state, and the current flows into the auxiliary winding. Through the coupling relationship between the main winding and the auxiliary winding of the transformer, the voltage across the first power switch is reduced from a first potential when the first power switch is turned off to a lower second potential, and then the first power switch is switched from the off state to the on state, so that the switching loss of the first power switch is lower; or

[0019] The auxiliary winding of the transformer of the power supply system has the same-name ends in opposite positions to the main winding. During a first pulse time before the first power switch switches from the off state to the on state, the second power switch is turned on, and current flows into the auxiliary winding. Through the coupling relationship between the main winding and the auxiliary winding of the transformer, the voltage across the first power switch rises from the potential when the first power switch is turned off to the first potential; during a second pulse time before the first power switch switches from the off state to the on state, the second power switch is turned off. Through the coupling relationship between the main winding and the auxiliary winding of the transformer, the voltage across the first power switch is reduced from the first potential to a lower second potential, and then the first power switch is switched from the off state to the on state, so that the switching loss of the first power switch is lower.

[0020] The utility model technology includes the following advantages:

[0021] Based on an auxiliary circuit of the utility model, by controlling the state of the second power switch, the auxiliary circuit enables the X capacitor of the power supply system to discharge quickly when the power supply system loses power. Compared with the prior art, the utility model improves the efficiency of the power supply system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1a It is a simplified structural diagram of a power supply system of an embodiment of the utility model;

[0023] Figure 1b It is a structural diagram of a power supply system with an auxiliary circuit according to an embodiment of the utility model;

[0024] Figure 1c is a structural diagram of a power supply system with an auxiliary circuit according to another embodiment of the utility model;

[0025] Figure 1d It is a structural diagram of a power supply system with an auxiliary circuit according to another embodiment of the utility model;

[0026] Figure 1e It is a structural diagram of a power supply system with an auxiliary circuit according to another embodiment of the utility model;

[0027] Figure 2a-2b These are two embodiments of the auxiliary module of the utility model;

[0028] Figure 2c It is an embodiment of the detection module of the utility model;

[0029] Figure 3a-3c It is a waveform diagram of some nodes of an embodiment of the utility model;

[0030] Figure 4is a structural diagram of a power supply system of another embodiment of the utility model;

[0031] Figure 5 It is a structural diagram of a power supply system of yet another embodiment of the utility model.

[0032] According to conventional working methods, various features and components in the figures are not drawn to scale, and the drawing method is to present the specific features and components related to the utility model in the best way. In addition, the same or similar element symbols are used to refer to similar elements / components between different figures.

[0033] Description of Reference Numerals

[0034] 11: first power supply system, 100: first power stage, 110: first auxiliary circuit, 111: second auxiliary circuit, 12: second power supply system, 120: second power stage, 121: freewheeling module, 13: third power supply system, 130: third power stage, 14: fourth power supply system, 140: fourth power stage, 141: absorption circuit, 15: fifth power supply system, 150: fifth power stage, 16: sixth power supply system, 17: seventh power supply system.

[0035] Explanation of symbols

[0036] MP: first power switch, MJ: normally on switch, MA: second power switch, GP: first control signal, GA: second control signal, Coss: parasitic capacitance, CX: X capacitance, DC1: first sampling diode, DC2: second sampling diode, CIC: holding capacitor, CP: power supply capacitor, VIC: sampling voltage, VAC: AC voltage, TS: transformer, Lp: primary winding, Ls: secondary winding, La: auxiliary winding, Ip: primary winding current, Ia: auxiliary winding current, Is: secondary Winding current, Nps: turns ratio, Dlp: absorption diode, Clp: absorption capacitor, CIN: input capacitor, CO: output capacitor, VIN: input voltage, VCC: supply voltage, VO: load voltage, Cdg: transcapacitor, VREF: reference voltage, SWA: detection signal, ZXC: demagnetization signal, Rsn: pull-down resistor, P1-P4: first port - fourth port, T1-T3: time point, T13: pulse time, T12: first period, T23: second period, Vds: cross voltage. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0038] In a first aspect, the utility model provides an auxiliary circuit. Figure 1a As shown, the first auxiliary circuit 110 is applied to a first power system 11 having a transformer TS and an X capacitor CX at an AC input end. The transformer TS has at least an auxiliary winding La and a primary winding Lp. The first auxiliary circuit 110 includes: a sampling module coupled to the X capacitor CX, configured to sample the voltage on the X capacitor CX and output a sampling voltage VIC; the auxiliary winding La has two ends, wherein the first end is coupled to the sampling voltage VIC. In one embodiment, the first end of the auxiliary winding La is coupled to the sampling voltage VIC after passing through the capacitor; the auxiliary module is coupled to the second end of the auxiliary winding La, and includes at least a second power switch MA; by controlling the state of the second power switch MA, the first auxiliary circuit 110 can enable the X capacitor CX of the first power system 11 to be quickly discharged when the first power system 11 is powered off; in one embodiment, the first auxiliary circuit 110 can also provide an electric voltage VCC for external power supply; in one embodiment, the first auxiliary circuit 110 can also detect the demagnetization state of the transformer TS and output a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed.

[0039] In one embodiment, if Figure 1a As shown, the sampling module includes a first sampling diode DC1, a second sampling diode DC2 and a holding capacitor CIC, wherein the anode of the first sampling diode DC1 is coupled to the first end of the X capacitor CX, the anode of the second sampling diode DC2 is coupled to the second end of the X capacitor CX, the cathode of the first sampling diode DC1 and the cathode of the second sampling diode DC2 are coupled to the holding capacitor CIC, and the sampling voltage VIC is generated on the holding capacitor CIC.

[0040] In one embodiment, if Figure 1a As shown, the auxiliary module has at least two ports, a first port P1 coupled to the second end of the auxiliary winding La, and a second port P2 coupled to a second control signal GA, and the second control signal GA controls the on and off of the second power switch MA.

[0041] In one embodiment, if Figure 2aAs shown, the auxiliary module includes a second power switch MA and a power supply capacitor CP. The first end of the second power switch MA is coupled to the first port P1 of the auxiliary module, the control end of the second power switch MA is coupled to the second port P2 of the auxiliary module, the second end of the second power switch MA is coupled to the power supply capacitor CP and outputs a power supply voltage VCC for external power supply, and the power supply voltage VCC is equivalent to the third port P3 of the auxiliary module. When the first power supply system 11 loses power, the second power switch MA is turned on and off under the control of the second control signal GA, and firstly transfers the energy on the holding capacitor CIC to the power supply capacitor CP to generate the power supply voltage VCC for external power supply, and at the same time, the energy on the X capacitor CX is transferred to the holding capacitor CIC through the first sampling diode DC1 and the second sampling diode DC2, which is finally equivalent to the first auxiliary circuit 110 transferring the energy on the X capacitor CX to the power supply capacitor CP to generate the power supply voltage VCC for external power supply, thereby realizing the rapid discharge of the X capacitor CX.

[0042] In one embodiment, if Figure 2b As shown, the auxiliary module includes a second power switch MA, a normally-on switch MJ, a power supply capacitor CP and a detection module, wherein a first end of the normally-on switch MJ is coupled to a first port P1 of the auxiliary module, a second end of the normally-on switch MJ is coupled to a first end of the second power switch MA, a control end of the normally-on switch MJ is coupled to the detection module, and by detecting a detection signal SWA of the control end of the normally-on switch MJ, the detection module outputs a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed, and the demagnetization signal ZXC is equivalent to a fourth port P4 of the auxiliary module; the control end of the second power switch MA is coupled to a second port P2 of the auxiliary module, and when the second control signal GA is at a high level, the second power switch MA is turned on, and when the second control signal GA is at a low level, the second The power switch MA is turned off; the second end of the second power switch MA is coupled to the power supply capacitor CP and outputs the power supply voltage VCC for external power supply. The power supply voltage VCC is equivalent to the third port P3 of the auxiliary module. When the first power supply system 11 loses power, the second power switch MA is turned on and off under the control of the second control signal GA. First, the energy on the holding capacitor CIC is transferred to the power supply capacitor CP to generate the power supply voltage VCC for external power supply. At the same time, the energy on the X capacitor CX is transferred to the holding capacitor CIC through the first sampling diode DC1 and the second sampling diode DC2. Finally, it is equivalent to the first auxiliary circuit 110 transferring the energy on the X capacitor CX to the power supply capacitor CP to generate the power supply voltage VCC for external power supply, thereby realizing the rapid discharge of the X capacitor CX.

[0043] In one embodiment, if Figure 1aAs shown, before the primary winding Lp of the transformer TS starts to be charged, the second power switch MA of the first auxiliary circuit 110 is turned on for a part or all of a pulse time, so that the current flowing through the second power switch MA flows through the auxiliary winding La.

[0044] In one embodiment, if Figure 1a As shown, the primary winding Lp of the transformer TS is connected in series with the first power switch MP. In one embodiment, the auxiliary winding La and the primary winding Lp have the same-named ends at the same position. The second power switch MA is turned on for a part or all of a pulse time before the first power switch MP switches from the off state to the on state, and the current flows into the auxiliary winding La. Through the coupling relationship between the primary winding Lp and the auxiliary winding La of the transformer TS, the cross voltage Vds across the first power switch MP is reduced from the first potential when the first power switch MP is turned off to a lower second potential. Then, the first power switch MP switches from the off state to the on state, so that the switching loss of the first power switch MP is lower. In one embodiment, the auxiliary winding La and the primary winding Lp have the same-named ends at the opposite positions. In the first During a first pulse period of time before the power switch MP is switched from the off state to the on state, the second power switch MA is turned on, and current flows into the auxiliary winding La. Through the coupling relationship between the primary winding Lp of the transformer TS and the auxiliary winding La, the voltage Vds across the first power switch MP rises from the potential when the first power switch MP is turned off to the first potential. During a second pulse period of time before the first power switch MP is switched from the off state to the on state, the second power switch MA is turned off. Through the coupling relationship between the primary winding Lp of the transformer TS and the auxiliary winding La, the voltage Vds across the first power switch MP decreases from the first potential to a lower second potential. Then, the first power switch MP is switched from the off state to the on state again, so that the switching loss of the first power switch MP is lower.

[0045] The same-name ends of two windings of a transformer are defined as follows: for two windings with magnetic coupling, when current flows into (or flows out of) one end of each winding at the same time, if the magnetic flux generated by the two windings helps each other, then these two ends are called the same-name ends of the transformer winding, and are marked with a black dot "·" or an asterisk "*". The position of the same-name ends can be defined by oneself, and the inflow end can be called the same-name end, and the outflow end can also be called the same-name end.

[0046] In one embodiment, if Figure 2c As shown, the auxiliary winding La and the primary winding Lp have the same-named ends at the same position. During the demagnetization of the transformer TS, when the voltage of the detection signal SWA at the control end of the normally-on switch MJ is lower than the preset reference voltage VREF, the detection module outputs a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed.

[0047] In one embodiment, if Figure 2c As shown, the auxiliary winding La and the main winding Lp have like-named ends in opposite positions. During the demagnetization of the transformer TS, when the voltage of the detection signal SWA at the control end of the normally-on switch MJ is higher than the preset reference voltage VREF, the detection module outputs a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed.

[0048] In one embodiment, in combination Figure 2c and Figure 3c The working principle of the detection module of the utility model can be further understood. The detection module includes a hysteresis comparator and a pull-down resistor Rsn. The first input end of the hysteresis comparator is coupled to a preset reference voltage VREF. In one embodiment, the preset reference voltage VREF is zero voltage; the second input end of the hysteresis comparator is coupled to the first end of the pull-down resistor Rsn and the detection signal SWA of the control end of the normally-on switch MJ. The second end of the pull-down resistor Rsn is coupled to the preset reference voltage VREF or zero voltage. After the demagnetization of the transformer TS is completed, the oscillation signal of the second end of the auxiliary winding La will be coupled to the control end of the normally-on switch MJ through the parasitic transcapacitor Cdg between the first end and the control end of the normally-on switch MJ to generate a detection signal SWA. When the voltage of the detection signal SWA at the second input end of the hysteresis comparator is lower than the voltage VREF at the first input end (at this time, the first input end is equivalent to the non-inverting end of the hysteresis comparator, and the second input end is equivalent to the inverting end of the hysteresis comparator), the output end of the hysteresis comparator outputs a demagnetization signal ZXC indicating the end of the demagnetization of the transformer TS. In one embodiment, when the demagnetization signal ZXC changes from a low level to a high level, it indicates that the demagnetization of the transformer TS is completed.

[0049] In one embodiment, if Figure 2cAs shown, the detection module includes a hysteresis comparator and a pull-down resistor Rsn. The first input terminal of the hysteresis comparator is coupled to a preset reference voltage VREF. In one embodiment, the preset reference voltage VREF is zero voltage. The second input terminal of the hysteresis comparator is coupled to the first terminal of the pull-down resistor Rsn and the detection signal SWA of the control terminal of the normally-on switch MJ. The second terminal of the pull-down resistor Rsn is coupled to the preset reference voltage VREF or zero voltage. After the demagnetization of the transformer TS is completed, the oscillation signal at the second terminal of the auxiliary winding La will be coupled to the control terminal of the normally-on switch MJ through the parasitic transcapacitor Cdg between the first terminal and the control terminal of the normally-on switch MJ to generate the detection signal SWA. When the voltage of the detection signal SWA at the second input terminal of the hysteresis comparator is higher than the voltage VREF at the first input terminal (at this time, the second input terminal is equivalent to the non-inverting terminal of the hysteresis comparator, and the first input terminal is equivalent to the inverting terminal of the hysteresis comparator), the output terminal of the hysteresis comparator outputs the demagnetization signal ZXC indicating the completion of the demagnetization of the transformer TS. In one embodiment, when the demagnetization signal ZXC changes from a low level to a high level, it indicates that the demagnetization of the transformer TS is completed.

[0050] In one embodiment, if Figure 2b As shown, the normally-on switch MJ is a junction field effect transistor (JFET). In one embodiment, when the control terminal of the JFET is pulled down to ground by the pull-down resistor Rsn, the highest voltage at the second terminal of the JFET is the pinch-off voltage of the JFET, which is equivalent to the normally-on switch MJ charging the power supply capacitor CP using the pinch-off voltage of the JFET, and the power supply capacitor CP provides the power supply voltage VCC to the outside.

[0051] In one embodiment, if Figure 2b As shown, the normally-on switch MJ is a depletion-mode metal oxide semiconductor field effect transistor (depletion-mode MOSFET).

[0052] In one embodiment, if Figure 2b As shown, the normally-on switch MJ is a depletion-mode gallium nitride transistor GaN (D-GaN).

[0053] In a second aspect, the present utility model provides a power supply system. Figure 1aThe first power supply system 11 shown in the figure comprises the first auxiliary circuit 110 described in the first aspect, the input end of the power supply system is coupled to the AC voltage VAC, and also comprises an input capacitor CIN, an output capacitor CO of a parallel load, a control module and a power stage, the first auxiliary circuit 110 provides a power supply voltage VCC for the control module; the power stage comprises at least a primary winding Lp of a transformer TS, a first power switch MP and a freewheeling module 121, the first control signal GP output by the control module is coupled to the control end of the first power switch MP to control the on and off of the first power switch MP; the second control signal GA output by the control module is coupled to the control end of the second power switch MA to control the on and off of the second power switch MA; the connection relationship between the power stage and the input capacitor CIN and the output capacitor CO can be combined to form any one of a step-down power supply system, a step-up power supply system, a flyback power supply system and a step-up / step-down power supply system.

[0054] In one embodiment, if Figure 1a As shown, the first power supply system 11 further includes a driving chip, and the driving chip at least includes an auxiliary module and a control module.

[0055] In one embodiment, the first power supply system 11 further includes a rectifier bridge, an input end of the rectifier bridge is coupled to an AC voltage VAC and an X capacitor CX, and an input capacitor CIN is coupled to an output end of the rectifier bridge for bypassing high-frequency signals.

[0056] In one embodiment, the freewheeling module 121 is composed of a diode, and the power stage including the diode forms a non-synchronous rectification structure.

[0057] In one embodiment, the freewheeling module 121 is composed of a metal oxide semiconductor field effect transistor (MOSFET), and the power stage of the field effect transistor forms a synchronous rectification structure.

[0058] In one embodiment, if Figure 1bAs shown, the primary winding Lp and the auxiliary winding La of the transformer TS of the second power supply system 12 have the same-named ends at the same position, the input end of the second power supply system 12 is coupled to the AC voltage VAC, including the X capacitor CX, the rectifier bridge, the input capacitor CIN, the output capacitor CO coupled in parallel with the load, the first auxiliary circuit 110, the control module and the second power stage 120, the second power stage 120 includes the primary winding Lp, the freewheeling module 121 and the first power switch MP; the first end of the output capacitor CO is coupled to the first end of the input capacitor CIN and the second end of the freewheeling module 121; the second end of the input capacitor CIN is coupled to the ground; the same-named end of the primary winding Lp is coupled to the second end of the output capacitor CO; the same-named end of the auxiliary winding La is also the first end of the auxiliary winding La, the non-same-named end of the auxiliary winding La is also the second end of the auxiliary winding La, the first end of the auxiliary winding La is coupled to the sampling voltage VIC of the first end of the holding capacitor CIC, and the second end of the auxiliary winding La is coupled to the first port P1 of the auxiliary module. The non-identical end of the primary winding Lp is coupled to the first end of the first power switch MP and the first end of the freewheeling module 121; the control end of the first power switch MP is coupled to the first control signal GP output by the control module, and the second end of the first power switch MP is grounded, or grounded after passing through a current detection resistor, and the first control signal GP output by the control module controls the conduction and cutoff of the first power switch MP.

[0059] In one embodiment, if Figure 1bAs shown, when the first power switch MP is turned on, the input voltage VIN charges the primary winding Lp through the load and the output capacitor CO. At this time, the voltage drop on the primary winding Lp is approximately VIN-VO (ignoring the conduction voltage drop of the first power switch MP). Through the coupling relationship of the transformer TS, when the number of turns of the primary winding Lp and the auxiliary winding La is the same or approximately the same, the voltage drop on the auxiliary winding La is also maintained at VIN-VO or approximately equal to VIN-VO; during the charging period of the primary winding Lp, the voltage at the second end of the auxiliary winding La is VIC-(VIN-VO)=VIC-VIN+VO; during the charging period of the first power switch M During the cut-off period of P, the load voltage VO on the output capacitor CO discharges the main winding Lp. At this time, the voltage drop on the main winding Lp is approximately -VO. Through the coupling relationship of the transformer TS, when the number of turns of the main winding Lp and the auxiliary winding La is the same or approximately the same, the voltage drop on the auxiliary winding La is also maintained at -VO or approximately equal to -VO; during the discharge period of the main winding Lp, the voltage at the second end of the auxiliary winding La is VIC-(-VO)=VIC+VO. Therefore, whether during the charging or discharging period of the transformer TS, the auxiliary module can draw power from the second end of the auxiliary winding La to provide the control module with the power supply voltage VCC. After the demagnetization of the main winding Lp is completed, the parasitic capacitance Coss of the main winding Lp and the first end of the first power switch MP will resonate with LC, and the potential of the non-same-name end of the main winding Lp will start to decrease from VIN. Through the coupling relationship of the transformer TS, the potential of the non-same-name end of the auxiliary winding La will also decrease synchronously. Through the coupling effect of the parasitic transcapacitor Cdg between the first end and the control end of the normally-on switch tube MJ, as shown in Figure 2b As shown, the oscillation signal of the non-same-name end of the auxiliary winding La is coupled to the control end of the normally-on switch MJ to generate a detection signal SWA. During the demagnetization period of the primary winding Lp, the detection module compares the detection signal SWA of the control end of the normally-on switch MJ with the preset reference voltage VREF. Figure 2c and Figure 3c When the voltage of the detection signal SWA at the control end of the normally-on switch MJ is lower than the preset reference voltage VREF, the detection module outputs a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed.

[0060] In one embodiment, in combination Figure 3aAs shown in the waveform diagram, before the primary winding Lp of the transformer TS starts to charge, the second power switch MA of the first auxiliary circuit 110 of the second power supply system 12 is first turned on for part or all of a pulse time T13, so that the current flowing through the second power switch MA flows through the auxiliary winding La to form an auxiliary winding current Ia. Through the coupling effect of the transformer TS, the auxiliary winding current Ia will be coupled to the primary winding Lp to generate a primary winding current Ip in the opposite direction. The main winding current Ip will reduce the voltage Vds across the first power switch MP connected in series with the main winding Lp from the first potential when the first power switch MP is turned off to a lower second potential. The first power switch MP is then switched from the off state to the on state, so that the switching loss of the first power switch MP is lower.

[0061] exist Figure 3a In the waveform diagram shown, the time point T1 corresponds to the time point when the second power switch MA is turned on before the first power switch MP. In one embodiment, the time point T1 is generated in response to the demagnetization signal ZXC indicating the end of demagnetization of the transformer TS; in one embodiment, the time point T1 is generated in response to a trough of the voltage Vds across the first power switch MP (either the first trough or the Nth trough). After the demagnetization of the transformer TS is completed, the primary winding Lp and the parasitic capacitance Coss at the first end of the first power switch MP undergo LC resonance, and multiple troughs are generated on the voltage Vds across the first power switch MP; in one embodiment, the time point T1 is generated in response to a pulse width modulation signal (PWM signal) of the power supply system.

[0062] exist Figure 3a In the waveform diagram shown, time point T3 corresponds to the turn-on time point of the first power switch MP, and the period between time point T1 and time point T3 is the pulse time T13 when the second power switch MA is turned on before the first power switch MP. The length of the pulse time T13 and the magnitude of the auxiliary winding current Ia flowing through the auxiliary winding La determine the amplitude of the voltage Vds across the first power switch MP dropping from the initial first potential to a lower second potential. In one embodiment, after the second potential is close to zero potential by optimizing the width of the pulse time T13 and the magnitude of the auxiliary winding current Ia, the first power switch MP is turned on again, so that the first power switch MP is switched to a zero voltage state or a state with lower switching loss.

[0063] exist Figure 3aIn the waveform diagram shown, time point T3 is the cut-off time point of the second power switch MA and is also the turn-on time point of the first power switch MP. In one embodiment, the cut-off time point of the second power switch MA is a time point T2 between time point T1 and time point T3, which is equivalent to the second power switch MA not being turned on during the entire pulse time T13, but only being turned on during the first period T12 of the pulse time T13, and being cut off during the second period T23, which is equivalent to T23 being the dead time of the first power switch MP and the second power switch MA.

[0064] The second power supply system 12 is a step-down power supply system. When the second power supply system 12 is operating normally, the AC voltage VAC generates an input voltage VIN on the input capacitor CIN after passing through the rectifier bridge. The AC voltage VAC simultaneously passes through the first sampling diode DC1 and the second sampling diode DC2 to generate a sampling voltage VIC on the holding capacitor CIC. In one embodiment, the capacitance of the holding capacitor CIC is much smaller than the capacitance of the input capacitor CIN, because the holding capacitor CIC provides energy to the auxiliary winding, and the input capacitor CIN needs to provide energy to the load, so the holding capacitor CIC is only 1 / 10 of the input capacitor CIN or a smaller capacitance (the capacitance of the holding capacitor CIC is only an exemplary description, not a limitation).

[0065] When the second power supply system 12 enters the power-off state, it is equivalent to disconnecting the AC voltage VAC from the X capacitor CX. At this time, the second power supply system 12 will continue to work, and the first auxiliary circuit 110 will continue to consume the energy on the holding capacitor CIC and the X capacitor CX. Since the capacitance of the holding capacitor CIC is much smaller than the capacitance of the input capacitor CIN, the sampling voltage VIC on the holding capacitor CIC will decrease faster than the input voltage VIN on the input capacitor CIN. Therefore, the energy on the X capacitor CX will be quickly transferred to the holding capacitor CIC, and then transferred to the power supply capacitor CP through the second power switch MA to be consumed by the power supply voltage VCC. In particular, when the second power supply system 12 works under light load or no load, the voltage on the input capacitor CIN decreases more slowly. Therefore, the X capacitor CX can be quickly discharged by the first auxiliary circuit 110 when the power supply system is powered off.

[0066] In one embodiment, if Figure 5 The seventh power supply system 17 shown in the figure, the difference between the seventh power supply system 17 and the second power supply system 12 is that the primary winding Lp and the auxiliary winding La of the transformer TS of the seventh power supply system 17 have the same-name ends in opposite positions, which also leads to a large difference in the working mode of the seventh power supply system 17 and the second power supply system 12.

[0067] like Figure 5As shown in FIG. 1 , when the first power switch MP is turned on, the input voltage VIN charges the primary winding Lp through the load and the output capacitor CO. At this time, the voltage drop on the primary winding Lp is approximately VIN-VO (ignoring the conduction voltage drop of the first power switch MP). Through the coupling relationship of the transformer TS, when the number of turns of the primary winding Lp and the auxiliary winding La is the same or approximately the same, the voltage drop on the auxiliary winding La is also maintained at -(VIN-VO) or approximately equal to -(VIN-VO); during the charging of the primary winding Lp, the voltage at the second end of the auxiliary winding La is VIC+(VIN-VO)=VIC+VIN+VO; During the cut-off period of the power switch MP, the load voltage VO on the output capacitor CO discharges the main winding Lp. At this time, the voltage drop on the main winding Lp is approximately -VO. Through the coupling relationship of the transformer TS, when the number of turns of the main winding Lp and the auxiliary winding La is the same or approximately the same, the voltage drop on the auxiliary winding La remains VO or approximately equal to VO; during the discharge period of the main winding Lp, the voltage at the second end of the auxiliary winding La is VIC-(VO)=VIC-VO. Therefore, whether during the charging or discharging period of the transformer TS, the auxiliary module can draw power from the second end of the auxiliary winding La to provide the control module with the power supply voltage VCC. After the demagnetization of the main winding Lp is completed, the main winding Lp and the parasitic capacitance Coss of the first end of the first power switch MP will have LC resonance, and the potential of the non-same-name end of the main winding Lp will start to decrease from VIN. Through the coupling relationship of the transformer TS, the potential of the non-same-name end of the auxiliary winding La will also increase synchronously. Through the coupling effect of the parasitic transcapacitor Cdg between the first end and the control end of the normally-on switch tube MJ, as shown in Figure 2b As shown, the oscillation signal of the non-same-name end of the auxiliary winding La will be coupled to the control end of the normally-on switch MJ to generate a detection signal SWA. During the demagnetization of the primary winding Lp, the detection module compares the detection signal SWA of the control end of the normally-on switch MJ with a preset reference voltage VREF. When the voltage of the detection signal SWA of the control end of the normally-on switch MJ is higher than the preset reference voltage VREF, the detection module outputs a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed.

[0068] Combination Figure 5 The seventh power supply system shown and Figure 3bAs shown in the waveform diagram, the auxiliary winding La of the transformer TS has the same-named ends in opposite positions as the main winding Lp. Before the first control signal GP output by the control module changes from a low level to a high level to control the first power switch MP from a cut-off state to a conducting state, the second control signal GA output by the control module generates a high level in the first period T12 of the pulse time T13, so that the second power switch MA in the first auxiliary circuit 110 is turned on for the first period T12 to charge the auxiliary winding La. The current flows through the auxiliary winding La. Through the coupling relationship of the transformer TS, the auxiliary winding current Ia flowing through the auxiliary winding La is coupled to the main winding Lp, generating a main winding current Ip in the same direction, so that the voltage Vds across the first power switch MP rises to the first potential VIN (ignoring the conduction voltage drop on the freewheeling module 121). Figure 3b In the schematic diagram shown, during the first period T12 of the pulse time T13, the second control signal GA is at a high level, the second power switch MA is turned on, and the auxiliary winding current Ia and the main winding current Ip with the same direction are generated on the auxiliary winding La accordingly. The main winding current Ip generated by coupling will charge the voltage Vds across the first power switch MP coupled in series with the main winding to the first potential VIN; during the second period T23 of the pulse time T13, the second control signal GA is at a low level, the second power switch MA is turned off, and through the coupling relationship between the main winding Lp and the auxiliary winding La of the transformer TS, the voltage Vds across the first power switch MP is rapidly reduced from the initial first potential VIN to a lower second potential (such as zero potential or a potential close to zero) during the second period T23, and then the first control signal GP output by the control module becomes a high level, controlling the first power switch MP to switch from the off state to the on state.

[0069] exist Figure 3b In the waveform diagram shown, the T1 time point corresponds to the time point when the second power switch MA is turned on before the first power switch MP. In one embodiment, the T1 time point is generated in response to the demagnetization signal ZXC indicating the end of demagnetization of the transformer TS; in one embodiment, the T1 time point is generated in response to the trough of the cross-voltage Vds across the first power switch MP (either the first trough or the Nth trough); in one embodiment, the T1 time point is generated in response to the pulse width modulation signal (PWM signal) of the seventh power supply system 17.

[0070] exist Figure 3bIn the waveform diagram shown, time point T3 corresponds to the turn-on time point of the first power switch MP, and the first period T12 between time point T1 and time point T2 is the pulse time of the turn-on of the second power switch MA. The length of the first period T12, the length of the second period T23 and the magnitude of the auxiliary winding current Ia flowing through the auxiliary winding La determine the amplitude of the voltage Vds across the first power switch MP dropping from the initial first potential VIN to a lower second potential. In one embodiment, after optimizing these three parameters to make the second potential close to zero potential, the first power switch MP is turned on again to achieve the switching of the first power switch MP to a zero voltage state.

[0071] The principle that the first auxiliary circuit 110 of the seventh power system 17 enables the X capacitor to discharge quickly when the power system is powered off is the same as that of the second power system 12, and will not be repeated in the specification.

[0072] In one embodiment, if Figure 1c The third power supply system 13 shown, the input end of the third power supply system 13 is coupled to the AC voltage VAC, including an X capacitor CX, a rectifier bridge, an input capacitor CIN, an output capacitor CO coupled in parallel with the load, a first auxiliary circuit 110, a control module and a third power stage 130, the third power stage 130 includes a main winding Lp, a freewheeling module 121 and a first power switch MP; the first end of the output capacitor CO is coupled to the first end of the input capacitor CIN and the first end of the main winding Lp; the second end of the input capacitor CIN is coupled to the ground, and the second end of the output capacitor CO is coupled to the second end of the freewheeling module 121; the first end of the auxiliary winding La is coupled to the sampling voltage VIC of the first end of the holding capacitor CIC, and the second end of the auxiliary winding La is coupled to the first port P1 of the auxiliary module. The second end of the primary winding Lp is coupled to the first end of the first power switch MP and the first end of the freewheeling module 121; the control end of the first power switch MP is coupled to the first control signal GP output by the control module, the second end of the first power switch MP is grounded, or grounded after passing through a current detection resistor, and the first control signal GP output by the control module controls the conduction and cutoff of the first power switch MP.

[0073] The difference between the third power supply system 13 and the second power supply system 12 is that the third power supply system 13 belongs to a buck-boost power supply system, which is mainly reflected in the different positions of the output capacitor and the load of the third power supply system 13; the principle of the first auxiliary circuit 110 of the third power supply system 13 in realizing the rapid discharge of the X capacitor CX of the third power supply system 13, and the principle of the first auxiliary circuit 110 of the third power supply system 13 outputting the power supply voltage VCC to supply power to the outside, or the working principle of the first auxiliary circuit 110 of the third power supply system 13 detecting the demagnetization state of the transformer TS is completely similar to the second power supply system 12 and the seventh power supply system 17. For details, please refer to the analysis of the second power supply system 12 (the auxiliary winding La and the main winding Lp of the transformer TS have the same-named ends in the same position) and the analysis of the seventh power supply system 17 (the auxiliary winding La and the main winding Lp of the transformer TS have the same-named ends in opposite positions), and the specification will not repeat the description.

[0074] In one embodiment, if Figure 1d The fourth power supply system 14 shown, the input end of the fourth power supply system 14 is coupled to the AC voltage VAC, including an X capacitor CX, a rectifier bridge, an input capacitor CIN, an output capacitor CO coupled in parallel with the load, a first auxiliary circuit 110, a control module and a fourth power stage 140, the fourth power stage 140 includes a primary winding Lp, a secondary winding Ls, a freewheeling module 121 and a first power switch MP; a first end of the auxiliary winding La is coupled to a first end of the holding capacitor CIC, a second end of the auxiliary winding La is coupled to a first port P1 of the auxiliary module, a same-name end of the main winding Lp is coupled to a first end of the input capacitor CIN, a non-same-name end of the main winding Lp is coupled to a first end of the first power switch MP, and the first The second end of the power switch MP is grounded, or grounded after passing through a current detection resistor, the non-same-name end of the secondary winding Ls is coupled to the first end of the freewheeling module 121, the second end of the freewheeling module 121 is coupled to the first end of the output capacitor CO, and the second end of the output capacitor CO is coupled to the same-name end of the secondary winding Ls; or the non-same-name end of the secondary winding Ls is coupled to the first end of the output capacitor CO, the second end of the output capacitor CO is coupled to the first end of the freewheeling module 121, and the second end of the freewheeling module 121 is coupled to the same-name end of the secondary winding Ls; the first control signal GP output by the control module controls the conduction and cutoff of the first power switch MP, and the second control signal GA output by the control module controls the conduction and cutoff of the second power switch MA.

[0075] The difference between the fourth power supply system 14 and the second power supply system 12 is that the fourth power supply system 14 belongs to a flyback power supply system; the principle of the first auxiliary circuit 110 of the fourth power supply system 14 in realizing the rapid discharge of the X capacitor CX of the fourth power supply system 14, and the principle of the first auxiliary circuit 110 of the fourth power supply system 14 outputting the power supply voltage VCC to supply power to the outside, or the working principle of the first auxiliary circuit 110 of the fourth power supply system 14 detecting the demagnetization state of the transformer TS is completely similar to the second power supply system 12 and the seventh power supply system 17. For details, reference can be made to the analysis of the second power supply system 12 (the auxiliary winding La and the main winding Lp of the transformer TS have the same-named ends in the same position) and the analysis of the seventh power supply system 17 (the auxiliary winding La and the main winding Lp of the transformer TS have the same-named ends in opposite positions), and the specification will not repeat the description.

[0076] In one embodiment, if Figure 1e The fifth power supply system 15 shown, the input end of the fifth power supply system 15 is coupled to the AC voltage VAC, including an X capacitor CX, a rectifier bridge, an input capacitor CIN, an output capacitor CO coupled in parallel with the load, a first auxiliary circuit 110, a control module and a fifth power stage 150, the fifth power stage 150 includes a main winding Lp, a freewheeling module 121 and a first power switch MP; the first end of the output capacitor CO is coupled to the second end of the freewheeling module 121, the second end of the output capacitor CO is coupled to the ground, the first end of the input capacitor CIN is coupled to the first end of the main winding Lp; the second end of the input capacitor CIN is coupled to the ground; the first end of the auxiliary winding La is coupled to the sampling voltage VIC of the first end of the holding capacitor CIC, and the second end of the auxiliary winding La is coupled to the first port P1 of the auxiliary module. The second end of the primary winding Lp is coupled to the first end of the first power switch MP and the first end of the freewheeling module 121; the control end of the first power switch MP is coupled to the first control signal GP output by the control module, the second end of the first power switch MP is grounded, or is grounded after passing through a current detection resistor, the first control signal GP output by the control module controls the conduction and cutoff of the first power switch MP, and the second control signal GA output by the control module controls the conduction and cutoff of the second power switch MA.

[0077] The difference between the fifth power system 15 and the second power system 12 is that the fifth power system 15 belongs to a boost power system; the principle of the first auxiliary circuit 110 of the fifth power system 15 in realizing the rapid discharge of the X capacitor CX of the fifth power system 15, and the principle of the first auxiliary circuit 110 of the fifth power system 15 outputting the power supply voltage VCC to supply power to the outside, or the working principle of the first auxiliary circuit 110 of the fifth power system 15 detecting the demagnetization state of the transformer TS are completely similar to the second power system 12 and the seventh power system 17. For details, please refer to the analysis of the second power system 12 (the auxiliary winding La and the main winding Lp of the transformer TS have the same-named ends in the same position) and the analysis of the seventh power system 17 (the auxiliary winding La and the main winding Lp of the transformer TS have the same-named ends in opposite positions), and the specification will not repeat the description.

[0078] In one embodiment, if Figure 4 The sixth power supply system 16 shown in the figure, the sixth power supply system 16 and the fourth power supply system 14 are both flyback power supply systems; the difference between the sixth power supply system 16 and the fourth power supply system 14 is that the first end of the auxiliary winding La in the second auxiliary circuit 111 of the sixth power supply system 16 is not directly coupled to the sampled voltage VIC on the holding capacitor CIC, and the first end of the auxiliary winding La in the second auxiliary circuit 111 is coupled to the sampled voltage VIC on the holding capacitor CIC after passing through the absorption capacitor Clp. Figure 4It can be seen that the input end of the sixth power supply system 16 is coupled to the AC voltage VAC, including an X capacitor CX, a rectifier bridge, an input capacitor CIN, an output capacitor CO coupled in parallel to the load, a second auxiliary circuit 111, a control module, a fourth power stage 140 and an absorption circuit 141, the fourth power stage 140 includes a primary winding Lp, a secondary winding Ls, a freewheeling module 121 and a first power switch MP; the second end of the absorption capacitor Clp is coupled to the first end of the holding capacitor CIC, the first end of the absorption capacitor Clp is coupled to the cathode of the absorption diode Dlp and the first end of the auxiliary winding La, the second end of the auxiliary winding La is coupled to the first port P1 of the auxiliary module, the same-name end of the main winding Lp is coupled to the first end of the input capacitor CIN, and the non-same-name end of the main winding Lp is coupled to the first power switch MP. The first end of the rate switch MP is coupled to the anode of the absorption diode Dlp, the second end of the first power switch MP is grounded, or is grounded after passing through a current detection resistor, the non-same-name end of the secondary winding Ls is coupled to the first end of the freewheeling module 121, the second end of the freewheeling module 121 is coupled to the first end of the output capacitor CO, and the second end of the output capacitor CO is coupled to the same-name end of the secondary winding Ls; or the non-same-name end of the secondary winding Ls is coupled to the first end of the output capacitor CO, the second end of the output capacitor CO is coupled to the first end of the freewheeling module 121, and the second end of the freewheeling module 121 is coupled to the same-name end of the secondary winding Ls; the first control signal GP output by the control module controls the conduction and cutoff of the first power switch MP, and the second control signal GA output by the control module controls the conduction and cutoff of the second power switch MA.

[0079] When the first power switch MP is turned on, the input voltage VIN charges the primary winding Lp. At this time, the voltage drop on the primary winding Lp is approximately VIN (ignoring the conduction voltage drop of the first power switch MP). Through the coupling relationship of the transformer TS, when the primary winding Lp and the auxiliary winding La have the same-named ends at the same position and the number of winding turns is the same or approximately the same, the voltage drop on the auxiliary winding La is also maintained at VIN or approximately equal to VIN; during the charging of the primary winding Lp, the voltage at the second end of the auxiliary winding La is (VIC+Nps*VO)-VIN, (Nps is the turns ratio of the primary winding Lp and the secondary winding Ls) ; When the first power switch MP is turned off, the load voltage VO on the output capacitor CO discharges the secondary winding Ls, generating a secondary winding current Is to charge the output capacitor CO, which is equivalent to the voltage drop on the primary winding Lp being approximately -Nps*VO (ignoring the conduction voltage drop of the absorption diode Dlp). During the discharge of the secondary winding Ls, the voltage at the second end of the auxiliary winding La is (VIC+Nps*VO)-(-Nps*VO)=VIC+2Nps*VO; therefore, regardless of whether the transformer TS is charging or discharging, the auxiliary module can draw power from the second end of the auxiliary winding La to provide the control module with a power supply voltage VCC. After the demagnetization of the transformer TS is completed, the primary winding Lp and the parasitic capacitance Coss of the first end of the first power switch MP will generate LC resonance, and the potential of the non-same-name end of the primary winding Lp will start to decrease from VIC+Nps*VO. Through the coupling relationship of the transformer TS, the potential of the non-same-name end of the auxiliary winding La will also decrease synchronously. Through the coupling effect of the parasitic transcapacitor Cdg between the first end and the control end of the normally-on switch tube MJ, as shown in FIG. Figure 2b As shown, the oscillation signal of the non-same-name end of the auxiliary winding La is coupled to the control end of the normally-on switch MJ to generate a detection signal SWA. During the demagnetization period of the transformer TS, the detection module compares the detection signal SWA of the control end of the normally-on switch MJ with the preset reference voltage VREF. Figure 2c and Figure 3c When the voltage of the detection signal SWA at the control end of the normally-on switch MJ is lower than the preset reference voltage VREF, the detection module outputs a demagnetization signal ZXC indicating that the demagnetization of the transformer TS is completed.

[0080] When the sixth power supply system 16 is operating normally, the AC voltage VAC generates an input voltage VIN on the input capacitor CIN after passing through the rectifier bridge. The AC voltage VAC simultaneously passes through the first sampling diode DC1 and the second sampling diode DC2 to generate a sampling voltage VIC on the holding capacitor CIC. In one embodiment, the capacitance of the holding capacitor CIC is much smaller than the capacitance of the input capacitor CIN, because the holding capacitor CIC provides energy to the auxiliary winding, and the input capacitor CIN needs to provide energy to the load, so the holding capacitor CIC is only 1 / 10 of the input capacitor CIN or a smaller capacitance (the capacitance of the holding capacitor CIC is only an exemplary description, not a limitation).

[0081] When the sixth power supply system 16 enters the power-off state, it is equivalent to disconnecting the AC voltage VAC from the X capacitor CX. At this time, the sixth power supply system 16 will continue to work, and the second auxiliary circuit 111 will continue to consume the energy on the holding capacitor CIC and the X capacitor CX. Since the capacitance of the holding capacitor CIC is much smaller than the capacitance of the input capacitor CIN, the sampling voltage VIC on the holding capacitor CIC will decrease faster than the input voltage VIN on the input capacitor CIN. Therefore, the energy on the X capacitor CX will be quickly transferred to the holding capacitor CIC and consumed. In particular, when the sixth power supply system 16 works under light load or no load, the voltage on the input capacitor CIN decreases more slowly. Therefore, the X capacitor CX can be quickly discharged by the second auxiliary circuit 111 when the power supply system is powered off.

[0082] When the auxiliary winding La and the primary winding Lp of the transformer TS in the sixth power supply system 16 have the same-named ends at different positions, the working principle description thereof will not be repeated.

[0083] In the above embodiments, in order to facilitate a clearer and more concise description of the working principle of the present invention, the specification only exemplifies the case where the number of turns of the primary winding Lp and the auxiliary winding La of the transformer TS are the same. In the actual implementation process, the number of turns of the primary winding Lp and the auxiliary winding La of the transformer TS can also be kept different, but it does not affect the working principle of the present invention.

[0084] It can be seen from the above embodiments that the connection relationship between the first power stage 100 and the input capacitor CIN and the output capacitor CO can be combined to form any power system among a buck power system (Buck), a boost power system (Boost), a flyback power system (Flyback) and a buck-boost power system (BuckBoost).

[0085] In a third aspect, the utility model further provides a power supply device, comprising any power supply system described in the second aspect.

[0086] From the above description, it can be seen that the above embodiments of the present application achieve the following technical effects:

[0087] The utility model provides an auxiliary circuit, which controls the state of the second power switch, so that the X capacitor of the power supply system can be discharged quickly when the power supply system loses power. Compared with the prior art, the utility model improves the efficiency of the power supply system.

[0088] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0089] It should also be noted that, in this article, the orientation or position relationship indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the utility model. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. "And / or" means that either one of the two can be selected, or both can be selected. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. Without more restrictions, an element defined by the phrase "comprising a ..." does not exclude the existence of other identical elements in the process, method, article or terminal device comprising the element.

[0090] The technical solution provided by the utility model is described in detail above. The principle and implementation method of the utility model are described in this article using specific examples. The description of the above embodiments is only used to help understand the utility model, and the content of this specification should not be understood as limiting the utility model. At the same time, for those skilled in the art, according to the utility model, there will be different forms of changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived from them are still within the protection scope of the utility model.

Claims

1. An auxiliary circuit is applied to a power supply system having a transformer and an X capacitor, wherein the transformer has at least an auxiliary winding and a primary winding, and is characterized in that: The auxiliary circuit comprises: a sampling module, coupled to the X capacitor, configured to sample the voltage on the X capacitor and output the sampled voltage; An auxiliary winding having two ends, wherein a first end is coupled to the sampling voltage, or coupled to the sampling voltage after passing through a capacitor; an auxiliary module, coupled to the second end of the auxiliary winding, and comprising at least a second power switch; By controlling the state of the second power switch, the auxiliary circuit enables the X capacitor of the power system to discharge quickly when the power system loses power.

2. The auxiliary circuit according to claim 1, characterized in that: The auxiliary circuit can also provide a power supply voltage to supply power to the outside, or the auxiliary circuit can also detect the demagnetization state of the transformer and output a demagnetization signal indicating that the demagnetization of the transformer has ended.

3. The auxiliary circuit according to claim 1, characterized in that: The sampling module includes a first sampling diode, a second sampling diode and a holding capacitor, wherein an anode of the first sampling diode is coupled to a first end of the X capacitor, an anode of the second sampling diode is coupled to a second end of the X capacitor, a cathode of the first sampling diode and a cathode of the second sampling diode are coupled to the holding capacitor, and the sampling voltage is generated on the holding capacitor.

4. The auxiliary circuit according to claim 1, characterized in that: The auxiliary module has at least two ports, a first port coupled to the second end of the auxiliary winding, and a second port coupled to a second control signal, and the second control signal controls the conduction and cutoff of the second power switch.

5. The auxiliary circuit according to claim 4, characterized in that: The auxiliary module includes a second power switch and a power supply capacitor, a first end of the second power switch is coupled to a first port of the auxiliary module, a control end of the second power switch is coupled to a second port of the auxiliary module, a second end of the second power switch is coupled to the power supply capacitor and outputs a power supply voltage to supply power externally, and when the power supply system loses power, the second power switch transfers energy on the X capacitor to the power supply capacitor to generate a power supply voltage to supply power externally, and at the same time realizes rapid discharge of the X capacitor; or The auxiliary module includes a second power switch, a normally-on switch, a power supply capacitor and a detection module, wherein a first end of the normally-on switch is coupled to a first port of the auxiliary module, a second end of the normally-on switch is coupled to a first end of the second power switch, a control end of the normally-on switch is coupled to the detection module, and the detection module outputs a demagnetization signal indicating that demagnetization of the transformer is completed by detecting the control end of the normally-on switch; the control end of the second power switch is coupled to a second port of the auxiliary module, a second end of the second power switch is coupled to the power supply capacitor and outputs a power supply voltage for external power supply, and when the power supply system loses power, the second power switch and the normally-on switch transfer the energy on the X capacitor to the power supply capacitor to generate a power supply voltage for external power supply, and simultaneously realize rapid discharge of the X capacitor.

6. The auxiliary circuit according to claim 1, characterized in that: Before the auxiliary circuit starts charging the primary winding of the transformer, the second power switch of the auxiliary circuit is turned on for a part or all of a pulse time, so that the current flowing through the second power switch flows through the auxiliary winding.

7. The auxiliary circuit according to claim 6, characterized in that: The primary winding of the transformer is connected in series with the first power switch, the auxiliary winding and the primary winding have the same-named ends at the same position, the second power switch is turned on for a part or all of a pulse time before the first power switch switches from the off state to the on state, and the current flows into the auxiliary winding, and through the coupling relationship between the primary winding and the auxiliary winding of the transformer, the voltage across the two ends of the first power switch is reduced from a first potential when the first power switch is turned off to a lower second potential, and then the first power switch is switched from the off state to the on state, so that the switching loss of the first power switch is lower; or The primary winding of the transformer is connected in series with the first power switch, and the auxiliary winding has the same-named ends in opposite positions with the primary winding. During a first period of a pulse time before the first power switch switches from the off state to the on state, the second power switch is turned on, and current flows into the auxiliary winding. Through the coupling relationship between the primary winding and the auxiliary winding of the transformer, the voltage across the first power switch rises from the potential when the first power switch is turned off to the first potential; during a second period of a pulse time before the first power switch switches from the off state to the on state, the second power switch is turned off. Through the coupling relationship between the primary winding and the auxiliary winding of the transformer, the voltage across the first power switch decreases from the first potential to a lower second potential, and then the first power switch switches from the off state to the on state, so that the switching loss of the first power switch is lower.

8. A power supply system, comprising at least the auxiliary circuit according to any one of claims 1 to 7, characterized in that: The power supply system also includes an input capacitor, an output capacitor, a control module and a power stage; the power stage at least includes a primary winding of a transformer, a first power switch and a freewheeling module, the first control signal output by the control module is coupled to the control end of the first power switch to control the conduction and cutoff of the first power switch; the second control signal output by the control module is coupled to the control end of the second power switch to control the conduction and cutoff of the second power switch; the connection relationship between the power stage and the input capacitor and the output capacitor can be combined to form any one of a step-down power supply system, a step-up power supply system, a flyback power supply system and a step-up / step-down power supply system.

9. The power supply system according to claim 8, characterized in that: Before the control module controls the first power switch to switch from the off state to the on state, the control module controls the second power switch in the auxiliary circuit to first turn on a part or all of a pulse time, so that the current flowing through the second power switch flows through the auxiliary winding.

10. The power supply system according to claim 9, characterized in that: The auxiliary winding of the transformer of the power supply system has the same-named end at the same position as the main winding. The second power switch is turned on for part or all of a pulse time before the first power switch is switched from the off state to the on state, and the current flows into the auxiliary winding. Through the coupling relationship between the main winding and the auxiliary winding of the transformer, the voltage across the two ends of the first power switch is reduced from the first potential when the first power switch is turned off to a lower second potential. After that, the first power switch is switched from the off state to the on state again, so that the switching loss of the first power switch is lower; or The auxiliary winding of the transformer of the power supply system has the same-name ends in opposite positions to the main winding. During a first pulse time before the first power switch switches from the off state to the on state, the second power switch is turned on, and current flows into the auxiliary winding. Through the coupling relationship between the main winding and the auxiliary winding of the transformer, the voltage across the first power switch rises from the potential when the first power switch is turned off to the first potential; during a second pulse time before the first power switch switches from the off state to the on state, the second power switch is turned off. Through the coupling relationship between the main winding and the auxiliary winding of the transformer, the voltage across the first power switch is reduced from the first potential to a lower second potential, and then the first power switch is switched from the off state to the on state, so that the switching loss of the first power switch is lower.

Images