CN117289179A

CN117289179A - Auxiliary circuit, power supply system and electronic equipment

Info

Publication number: CN117289179A
Application number: CN202311245264.9A
Authority: CN
Inventors: 请求不公布姓名
Original assignee: Ensai Semiconductor Chengdu Co ltd
Current assignee: Ensai Semiconductor Chengdu Co ltd
Priority date: 2023-09-25
Filing date: 2023-09-25
Publication date: 2023-12-26

Abstract

The invention discloses an auxiliary circuit, a power supply system and electronic equipment, wherein the auxiliary circuit is applied to the power supply system with a transformer and an input capacitor, the transformer is at least provided with an auxiliary winding and a main-stage winding, and the auxiliary circuit comprises: auxiliary winding, normally-on switch and detection module. The auxiliary circuit provided by the invention has a simple structure, can supply power to the outside, and can also realize detection of the demagnetizing state of the transformer.

Description

Auxiliary circuit, power supply system and electronic equipment

Technical Field

The invention relates to the technical field of power conversion, in particular to an auxiliary circuit, a power supply system and electronic equipment.

Background

The applicant's prior application, patent application number 2023109871153, discloses an auxiliary circuit, a power supply system and an electronic device. The auxiliary circuit is applied to a power supply system with a transformer and an input capacitor, wherein the transformer is provided with at least an auxiliary winding and a main winding, and the auxiliary circuit generates a supply voltage VCC for supplying power to a driving module through a normally-on switch MJ coupled in series with the auxiliary winding. The auxiliary circuit has the disadvantage that the normally-on switch MJ of the auxiliary circuit is only used for generating the power supply voltage VCC, and a demagnetization detecting circuit for detecting the end of demagnetization of the transformer TS is additionally required when the power supply system works normally, which increases the cost of the power supply system.

The applicant's prior application, patent application number 2023102512893, discloses a demagnetization detection circuit, a power supply system and an electronic device. The demagnetization detection circuit is applied to a power supply system with a transformer, an input capacitor and an output capacitor, the transformer is at least provided with an auxiliary winding and a main winding, the demagnetization detection circuit detects the demagnetization state of the transformer TS through a second power switch MA which is coupled in series with the auxiliary winding, and then a demagnetization signal ZXC of the demagnetization end of the transformer TS is output after the voltage of one node of the second power switch MA is compared through a comparison module. The demagnetizing detection circuit has the disadvantage that a second power switch MA with ultrahigh voltage resistance is needed to be connected in series with the auxiliary winding La to realize detection of the demagnetizing state of the transformer, which greatly increases the cost of the power supply system. There is a need to improve upon the deficiencies of the prior application.

Disclosure of Invention

In a first aspect, the present invention provides an auxiliary circuit for use in a power supply system having a transformer and an input capacitance, the transformer having at least an auxiliary winding and a primary winding, the auxiliary circuit comprising:

The auxiliary winding is provided with two ends, wherein the first end of the auxiliary winding is coupled with the first end of the input capacitor, or is coupled with the first end of the input capacitor after passing through the capacitor, and the second end of the input capacitor is grounded;

a normally-on switch having a first end, a second end and a control end, wherein the first end is coupled to the second end of the auxiliary winding, the second end is configured to provide a supply voltage for supplying power;

the detection module is coupled with the control end of the normally-on switch and is configured to compare the voltage or current of the control end of the normally-on switch with a preset reference voltage or a reference current source during the demagnetization of the transformer, so as to obtain a demagnetization signal representing the end of the demagnetization of the transformer.

Preferably, the auxiliary winding and the main winding have same-name ends at the same position, and the detection module outputs a demagnetizing signal representing the end of demagnetization of the transformer when the voltage of the control end of the normally-on switch is lower than a preset reference voltage during the demagnetization of the transformer; or (b)

The auxiliary winding and the main winding are provided with homonymous ends at the same position, and when the current flowing into the control end of the normally-on switch is larger than a preset reference current during the demagnetization of the transformer, the detection module outputs a demagnetization signal representing the completion of the demagnetization of the transformer; or (b)

The auxiliary winding and the main winding are provided with homonymous ends at opposite positions, and when the voltage of the control end of the normally-on switch is higher than a preset reference voltage during the demagnetization of the transformer, the detection module outputs a demagnetization signal representing the completion of the demagnetization of the transformer; or (b)

And the detection module outputs a demagnetizing signal representing the end of demagnetization of the transformer when the current flowing out of the control end of the normally-on switch is larger than a preset reference current during the demagnetization of the transformer.

Preferably, the detection module comprises a hysteresis comparator and a pull-down resistor, wherein the in-phase end of the hysteresis comparator is coupled with the preset reference voltage or zero voltage, the inverting end of the hysteresis comparator is coupled with the first end of the pull-down resistor and the control end of the normally-on switch, the second end of the pull-down resistor is coupled with the preset reference voltage or zero voltage, and when the voltage of the inverting end of the hysteresis comparator is lower than the voltage of the in-phase end, the output end of the hysteresis comparator outputs a demagnetization signal representing that demagnetization of the transformer is finished; or (b)

The detection module comprises a current mirror, a reference current source and a pull-down resistor, wherein the first end of the pull-down resistor is coupled with the control end of the normally-on switch and the first end of the current mirror, the second end of the pull-down resistor is grounded, the second end of the current mirror is coupled with the first end of the reference current source, the second end of the reference current source is grounded, the second end of the current mirror looks like the current of the first end of the current mirror, and a demagnetizing signal representing the end of demagnetization of the transformer is generated after the current of the second end of the current mirror is compared with the reference current of the reference current source; or (b)

The detection module comprises a hysteresis comparator and a pull-down resistor, wherein the inverting terminal of the hysteresis comparator is coupled with the preset reference voltage or zero voltage, the in-phase terminal is coupled with the first terminal of the pull-down resistor and the control terminal of the normally-on switch, the second terminal of the pull-down resistor is coupled with the preset reference voltage or zero voltage, and when the voltage of the in-phase terminal of the hysteresis comparator is higher than the voltage of the inverting terminal, the output terminal of the hysteresis comparator outputs a demagnetizing signal representing the end of demagnetization of the transformer; or (b)

The detection module comprises a current mirror, a reference current source and a pull-down resistor, wherein a first end of the pull-down resistor is coupled with a control end of a normally-on switch and a first end of the current mirror, a second end of the pull-down resistor is grounded, a second end of the current mirror is coupled with a second end of the reference current source, the first end of the reference current source is connected with a power supply, a second end of the current mirror looks like a current of the first end of the current mirror, and a demagnetizing signal representing the end of demagnetization of the transformer is generated after the current of the second end of the current mirror is compared with the reference current of the reference current source.

Preferably, the normally-on switch is one of a junction field effect transistor, a depletion type metal oxide semiconductor field effect transistor, or a depletion type gallium nitride transistor GaN.

Preferably, when the parasitic transcapacitive between the first end and the control end of the normally-on switch is smaller, an auxiliary capacitor capable of resisting high voltage is configured between the first end and the control end of the normally-on switch to assist in detecting the demagnetized state of the transformer.

In a second aspect, an embodiment of the present invention provides a power supply system, including at least the auxiliary circuit of any one of the first aspects, the power supply system further includes a control module and a driving module, the auxiliary circuit supplies power to the driving module through a second end of a normally-on switch, and outputs a demagnetization detection signal to an input end of the control module after demagnetization of the transformer is completed; the first control signal output by the control module is coupled with the control end of the first power switch after passing through the driving module, and the on and off of the first power switch are controlled.

Preferably, the power supply system further comprises an output capacitor and a power stage coupled in parallel to the load; the power stage includes at least a primary winding of a transformer, a freewheel module, and a first power switch.

Preferably, the power supply system further comprises a driving chip, wherein the driving chip at least comprises a normally-on switch, a detection module, a control module and a driving module.

Preferably, the connection relation between the power stage and the input capacitor and the connection relation between the power stage and the output capacitor can be combined to form any one of a buck power supply system, a boost power supply system, a flyback power supply system and a buck-boost power supply system.

In a third aspect, the present invention provides an electronic device comprising the power supply system of any one of the second aspects.

The technology of the invention has the following advantages:

according to the auxiliary circuit, through sharing the normally-on switching tube, the power supply voltage can be supplied to the outside, the detection of the demagnetizing state of the transformer is realized, and compared with the prior art, the ultrahigh voltage-resistant switching tube can be saved, the chip cost is saved, and the reliability of demagnetization detection is improved.

Drawings

FIG. 1 is a simplified block diagram of an auxiliary circuit of one embodiment of the present invention;

FIG. 2a is a block diagram of a power supply system with auxiliary circuitry according to one embodiment of the invention;

FIG. 2b is a block diagram of a power supply system with auxiliary circuitry in accordance with another embodiment of the present invention;

FIG. 2c is a block diagram of a power supply system with auxiliary circuitry in accordance with yet another embodiment of the present invention;

FIG. 2d is a block diagram of a power supply system with auxiliary circuitry in accordance with yet another embodiment of the present invention;

FIGS. 3 a-3 d are diagrams of one embodiment of a detection module of the present invention;

FIG. 3e is a schematic waveform diagram of a portion of a node according to one embodiment of the invention;

fig. 4 is a simplified block diagram of an auxiliary circuit of another embodiment of the present invention.

Various features and elements are not drawn to scale in accordance with conventional practice in the drawings in order to best illustrate the specific features and elements associated with the invention. In addition, like elements/components are referred to by the same or similar reference numerals among the different drawings.

Description of the reference numerals

11: first power supply system

100: first power stage

110: auxiliary circuit

111: second auxiliary circuit

12: second power supply system

120: second power stage

121: freewheel 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

Symbol description

MP: first power switch

MJ: normally-on switch

GP: first control signal

Coss: parasitic capacitance

TS: transformer

Lp: main-stage winding

Ls: secondary winding

La: auxiliary winding

Ip: main stage winding current

Ia: auxiliary winding current

Is: secondary winding current

Nps: turns ratio

Dlp: absorption diode

Clp: absorption capacitor

CIN: input capacitance

CO: output capacitor

VIN: input voltage

VCC: supply voltage

VO: load voltage

Cds: transcapacitive (scd)

Ch: auxiliary capacitor

VREF: reference voltage

IREF: reference current source

ZXC: demagnetizing signal

SWA: control terminal

Rsn: pull down the resistor.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In a first aspect, the present invention provides an auxiliary circuit. As shown in fig. 1, an auxiliary circuit 110 is applied to a first power supply system 11 having a transformer TS and an input capacitance CIN, the transformer TS having at least an auxiliary winding La and a main stage winding Lp, the auxiliary circuit 110 comprising: an auxiliary winding La having two ends, wherein a first end is coupled to a first end of the input capacitor CIN; in one embodiment, the first end of the auxiliary winding La is coupled to the first end of the input capacitor CIN after passing through the capacitor; the second terminal of the input capacitance CIN is grounded; a normally-on switch MJ having a first terminal coupled to the second terminal of the auxiliary winding La, a second terminal configured to provide a supply voltage VCC for supplying power, and a control terminal SWA; the detection module is coupled to the control terminal SWA of the normally-on switch MJ and configured to compare the voltage or current of the control terminal SWA of the normally-on switch MJ with a preset reference voltage VREF or a reference current of the reference current IREF during the demagnetization of the transformer TS, so as to obtain a demagnetization signal ZXC representing the end of the demagnetization of the transformer TS.

The homonymous ends of the two windings of the transformer are defined as follows: when current flows into (or out of) two windings simultaneously from one end of each winding respectively, if magnetic fluxes generated by the two windings are aided, the two ends are called as homonymous ends of the transformer winding, and black dots "·" or asterisks are used for marking. The positions of the homonymous terminals can be defined by themselves, the inflow terminals can be called homonymous terminals, and the outflow terminals can be called homonymous terminals.

In one embodiment, the auxiliary winding La and the main winding Lp have the same-name terminals at the same position, and the detection module outputs the demagnetizing signal ZXC indicating the end of demagnetization of the transformer TS when the voltage of the control terminal SWA of the normally-on switch MJ is lower than the preset reference voltage VREF during the demagnetization of the transformer TS.

In one embodiment, the auxiliary winding La and the main winding Lp have the same-name terminals at the same position, and the detection module outputs the demagnetizing signal ZXC indicating the end of demagnetization of the transformer TS when the current flowing into the control terminal SWA of the normally-on switch MJ is greater than the reference current of the preset reference current source IREF during the demagnetization of the transformer TS.

In one embodiment, the auxiliary winding La and the main winding Lp have the same-name ends at opposite positions, and the detection module outputs the demagnetizing signal ZXC indicating the end of demagnetization of the transformer TS when the voltage of the control end SWA of the normally-on switch MJ is higher than the preset reference voltage VREF during the demagnetization of the transformer TS.

In one embodiment, the auxiliary winding La and the main winding Lp have the same-name ends at opposite positions, and the detection module outputs the demagnetizing signal ZXC indicating the end of demagnetization of the transformer TS when the current flowing out of the control end SWA of the normally-on switch MJ is greater than the reference current of the preset reference current source IREF during the demagnetization of the transformer TS.

In one embodiment, the working principle of the detection module of the present invention can be further understood by referring to fig. 3a and 3e, the detection module includes a hysteresis comparator and a pull-down resistor Rsn, the in-phase end of the hysteresis comparator is coupled to a preset reference voltage VREF, in one embodiment, the pre-examined reference voltage VREF is zero, the inverting end of the hysteresis comparator is coupled to the first end of the pull-down resistor Rsn and the control end SWA 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, after the demagnetization of the transformer TS is finished, the oscillation signal of the second end of the auxiliary winding La is coupled to the control end SWA of the normally-on switch MJ through a parasitic transcapacitive Cds between the first end and the control end SWA of the normally-on switch MJ, and when the voltage SWA of the inverting end of the hysteresis comparator is lower than the voltage VREF of the in-phase end, the output end of the hysteresis comparator outputs a demagnetizing signal ZXC indicating the completion of the demagnetization of the transformer TS. In one embodiment, the demagnetization signal ZXC changes from low to high, indicating that the demagnetization of the transformer TS is finished.

In one embodiment, as shown in fig. 3b, the detection module includes a current mirror, a reference current source IREF and a pull-down resistor Rsn, a first terminal of the pull-down resistor Rsn is coupled to the control terminal SWA of the normally-on switch MJ and an input terminal of the current mirror, a second terminal of the pull-down resistor Rsn is grounded, an output terminal of the current mirror is coupled to the first terminal of the reference current source IREF, a second terminal of the reference current source IREF is grounded, a second terminal of the current mirror mirrors a current of the first terminal of the current mirror, and after the demagnetization of the transformer TS is completed, an oscillation signal of the second terminal of the auxiliary winding La is coupled to the control terminal SWA of the normally-on switch MJ through a parasitic transcapacitive between the first terminal of the normally-on switch MJ and the control terminal SWA, and a demagnetizing signal ZXC indicating the completion of the demagnetization of the transformer TS is generated after the current output of the current mirror is compared with the reference current of the reference current source IREF. In one embodiment, the demagnetization signal ZXC changes from low to high, indicating that the demagnetization of the transformer TS is finished.

In one embodiment, as shown in fig. 3c, the detection module includes a hysteresis comparator and a pull-down resistor Rsn, the inverting terminal of the hysteresis comparator is coupled to a preset reference voltage VREF, in one embodiment, the pre-checked reference voltage VREF is zero, the non-inverting terminal of the hysteresis comparator is coupled to the first terminal of the pull-down resistor Rsn and the control terminal SWA 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, after the demagnetization of the transformer TS is finished, the oscillation signal of the second terminal of the auxiliary winding La is coupled to the control terminal SWA of the normally-on switch MJ through a parasitic cross capacitor Cds between the first terminal and the control terminal SWA of the normally-on switch MJ, and when the voltage SWA of the non-inverting terminal of the hysteresis comparator is higher than the voltage VREF of the inverting terminal, the output terminal of the hysteresis comparator outputs a demagnetizing signal ZXC indicating the end of the demagnetization of the transformer TS. In one embodiment, the demagnetization signal ZXC changes from low to high, indicating that the demagnetization of the transformer TS is finished.

In one embodiment, as shown in fig. 3d, the detection module includes a current mirror, a reference current source IREF and a pull-down resistor Rsn, a first terminal of the pull-down resistor Rsn is coupled to the control terminal SWA of the normally-on switch MJ and an input terminal of the current mirror, a second terminal of the pull-down resistor Rsn is grounded, an output terminal of the current mirror is coupled to a second terminal of the reference current source IREF, a first terminal of the reference current source IREF is connected to a power supply, a second terminal of the current mirror mirrors a current of the first terminal of the current mirror, after the demagnetization of the transformer TS is completed, an oscillation signal of the second terminal of the auxiliary winding La is coupled to the control terminal SWA of the normally-on switch MJ through a parasitic transcapacitive between the first terminal of the normally-on switch MJ and the control terminal SWA, and a demagnetization signal ZXC indicating the completion of the demagnetization of the transformer TS is generated after the current outputted by the current mirror is compared with the reference current of the reference current source IREF. In one embodiment, the demagnetization signal ZXC changes from high to low, indicating that the demagnetization of the transformer TS is finished.

In one embodiment, as shown in fig. 1, the normally-on switch MJ is a Junction Field Effect Transistor (JFET).

In one embodiment, as shown in fig. 1, the normally-on switch MJ is a depletion-mode metal oxide semiconductor field effect transistor (depletion-mode MOSFET).

In one embodiment, as shown in FIG. 1, normally-on switch MJ is a depletion gallium nitride transistor GaN (D-GaN).

In one embodiment, when the parasitic transcapacitive Cds between the first terminal and the control terminal SWA of the normally-on switch MJ are smaller, and the oscillation signal of the second terminal of the auxiliary winding La cannot be coupled to the control terminal SWA of the normally-on switch MJ through the parasitic transcapacitive Cds, a high-voltage-tolerant auxiliary capacitor Ch is added between the first terminal and the control terminal SWA of the normally-on switch MJ to assist in detecting the demagnetized state of the transformer TS.

In one embodiment, the detection of the demagnetizing state of the transformer TS may be achieved by providing an auxiliary capacitor Ch, which is capable of withstanding an ultra-high voltage, between the second end of the auxiliary winding La and the input SWA of the detection module, and coupling the oscillation signal of the second end of the auxiliary winding La to the input of the detection module.

In a second aspect, an embodiment of the present invention provides a power supply system. The first power supply system 11 shown in fig. 1, the power supply system includes the auxiliary circuit 110 according to the first aspect, the power supply system further includes a control module and a driving module, and the auxiliary circuit 110 supplies a power supply voltage VCC to the driving module through a second terminal of the normally-on switch MJ; the first control signal GP output by the control module is coupled with the control end of the first power switch MP after passing through the driving module, and controls the on and off of the first power switch MP.

In one embodiment, as shown in fig. 1, the first power supply system 11 further includes an output capacitor CO and a first power stage 100 coupled in parallel with the load; the first power stage 100 comprises at least a main stage winding Lp of a transformer TS, a freewheel module 121 and a first power switch MP.

In one embodiment, as shown in fig. 1, the first power system 11 further includes a driving chip, where the driving chip includes at least a normally-on switch MJ, a detection module, a control module, and a driving module.

In one embodiment, the first power system 11 further includes a rectifier bridge, an input terminal of the rectifier bridge is coupled to the ac power, and an input capacitor CIN is coupled to an output terminal of the rectifier bridge for bypassing the high frequency signal.

In one embodiment, the input terminal of the first power system 11 is directly coupled to the dc input voltage VIN, and the input capacitor CIN is used for bypassing the high frequency signal of the input voltage VIN.

In one embodiment, the freewheel module 121 is composed of diodes, and the power stages including the diodes constitute an asynchronous rectification structure.

In one embodiment, the freewheel module 121 is composed of a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), and the power stage including the MOSFET constitutes a synchronous rectification structure.

In one embodiment, as shown in fig. 2a, the second power supply system 12 includes an input capacitance CIN, an output capacitance CO coupled in parallel to a load, an auxiliary circuit 110, a control module, a drive module, and a second power stage 120, the second power stage 120 including a main stage winding Lp, a freewheel module 121, and a first power switch MP; the first end of the output capacitor CO is coupled with the first end of the input capacitor CIN, the homonymous end of the auxiliary winding La and the second end of the freewheel module 121; the second terminal of the input capacitor CIN is coupled with the ground; the homonymous end of the main stage winding Lp is coupled with the second end of the output capacitor CO; the same-name end of the auxiliary winding La is also the first end of the auxiliary winding La, the non-same-name 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 with the input voltage VIN of the first end of the input capacitor CIN, the second end of the auxiliary winding La is coupled with the first end of the normally-on switch MJ, the second end of the normally-on switch MJ provides the supply voltage VCC for supplying power, and the control end of the normally-on switch MJ is coupled with the detection module. In one embodiment, the normally-on switch MJ is a Junction Field Effect Transistor (JFET), and 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 supplying power to the driving module by using the pinch-off voltage of the JFET. The non-homonymous end of the main stage winding Lp is coupled with the first end of the first power switch MP and the first end of the freewheel module 121; the control end of the first power switch MP is coupled with a first control signal GP output by the control module through the driving module, the second end of the first power switch MP is grounded, or is grounded after passing through a current detection resistor, and the first control signal GP output by the control module controls the on and off of the first power switch MP.

In one embodiment, the homonymous terminal of the auxiliary winding La of the second power supply system 12 is directly coupled to the first terminal of the input capacitance.

The second power supply system 12 belongs to a step-down power supply system, when the same-name end of the auxiliary winding La of the second power supply system 12 is directly coupled to the first end of the input capacitor, when the first power switch MP is turned on, the input voltage VIN charges the main winding Lp through the load and the output capacitor CO, at this time, the voltage drop on the main winding Lp is approximately VIN-VO (neglecting the conduction voltage drop of the first power switch MP), and by the coupling relation of the transformer TS, the voltage drop on the auxiliary winding La is also kept to be VIN-VO or approximately equal to VIN-VO under the condition that the turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during charging of the main stage winding Lp, the voltage at the first terminal of the normally-on switch MJ is VIN- (VIN-VO) =vo; during the turn-off period of the first power switch MP, the load voltage VO on the output capacitor CO discharges the main winding Lp, and at this time, the voltage drop on the main winding Lp is approximately-VO, and by the coupling relationship of the transformer TS, the voltage drop on the auxiliary winding La is also maintained at-VO or approximately-VO under the condition that the turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during the discharging period of the main stage winding Lp, the voltage at the first end of the normally-on switch MJ is VIN- (-VO) =vin+vo, so that the normally-on switch MJ can take power from the second end of the auxiliary winding La and supply the power supply voltage to the driving module, regardless of whether the transformer TS is charged or discharged. After the demagnetization of the main winding Lp is finished, LC resonance occurs between the main winding Lp and the parasitic capacitor Coss at the first end of the first power switch MP, the potential of the non-homonymous end of the main winding Lp will decrease from VIN, the potential of the non-homonymous end of the auxiliary winding La will also decrease synchronously through the coupling relationship of the transformer TS, through the coupling effect of the parasitic transcapacitive Cds between the first end of the normally-on switching tube MJ and the control end SWA, the oscillation signal of the non-homonymous end of the auxiliary winding La will be coupled to the control end of the normally-on switching tube MJ, during the demagnetization of the main winding Lp, the detection module compares the voltage or current of the control end of the normally-on switching tube MJ with the preset reference voltage VREF or the reference current source, and when the voltage of the sampling signal SWA at the control end of the normally-on switching tube MJ is lower than the preset reference voltage VREF, in conjunction with fig. 3a and 3e, the detection module outputs the demagnetization signal ZXC indicating the end of the demagnetization of the main winding Lp of the transformer TS.

In one embodiment, the first end of the auxiliary winding La of the second power supply system 12 shown in fig. 2a is coupled to the second end of the output capacitor CO, and by changing the winding ratio relationship between the auxiliary winding La and the main stage winding Lp, the power supply function of the auxiliary circuit 110 and the demagnetization status detection function of the transformer TS can be implemented, and the detailed analysis will not be repeated in the description.

In one embodiment, the auxiliary winding La and the main winding Lp of the transformer TS of the second power system 12 have opposite identical-name ends, which is equivalent to that the first end of the normally-on switch MP is coupled to the non-name end of the auxiliary winding La, and the first end of the first power switch MP is coupled to the identical-name end of the main winding Lp. When the first power switch MP is turned on, the input voltage VIN charges the main winding Lp through the load and the output capacitor CO, and at this time, the voltage drop on the main winding Lp is approximately VIN-VO (neglecting the on-voltage drop of the first power switch MP), and by the coupling relationship of the transformer TS, the voltage drop on the auxiliary winding La is kept to be- (VIN-VO) or approximately equal to- (VIN-VO) under the condition that the number of turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during charging of the main stage winding Lp, the voltage at the first terminal of the normally-on switch MJ is vin+ (VIN-VO) =2vin-VO; when the first power switch MP is turned off, 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, and by means of the coupling relationship of the transformer TS, the voltage drop on the auxiliary winding La is kept at VO or approximately equal to VO under the condition that the turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during the discharging period of the main stage winding Lp, the voltage of the first end of the normally-on switch MJ is VIN-VO; therefore, the normally-on switch MJ can take power from the second end of the auxiliary winding La and supply the power supply voltage to the driving module, regardless of whether the transformer TS is charged or discharged. The auxiliary circuit 110 can also realize a power supply function and a demagnetization state detection function for the transformer TS when the auxiliary winding La and the main winding Lp of the transformer TS have the same name ends in opposite positions.

In one embodiment, as shown in fig. 2b, the third power supply system 13 comprises an input capacitor CIN, a load coupled in parallel with an output capacitor CO, an auxiliary circuit 110, a control module, a drive module, and a third power stage 130, the third power stage 130 comprising a main stage winding Lp, a freewheel module 121, and a first power switch MP; the second end of the output capacitor CO is coupled with the first end of the input capacitor CIN and the homonymous end of the main stage winding Lp; the same-name end of the auxiliary winding La is also the first end of the auxiliary winding La, the non-same-name 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 with the first end of the output capacitor CO and the second end of the freewheel module 121, and the first end of the auxiliary winding La is equally coupled with the input voltage VIN of the first end of the input capacitor CIN after passing through the output capacitor CO, and the second end of the auxiliary winding La is coupled with the first end of the normally-on switch MJ; the second terminal of the normally-on switch MJ provides a supply voltage VCC for supplying power, and the control terminal of the normally-on switch MJ is coupled with the detection module. In one embodiment, the normally-on switch MJ is a Junction Field Effect Transistor (JFET), and 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 that the normally-on switch MJ uses the pinch-off voltage of the JFET to supply power to the driving module; the non-homonymous end of the main-stage winding Lp is coupled with the first end of the first power switch MP and the first end of the follow current module 121, the second end of the follow current module 121 is coupled with the first end of the output capacitor CO and the first end of the auxiliary winding La, and the control end of the first power switch MP is coupled with a first control signal GP output by the control module after passing through the driving 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 on and off of the first power switch MP.

The third power supply system 13 belongs to a step-up/down power supply system, and when the first power switch MP is turned on, the input voltage VIN charges the main winding Lp, at this time, the voltage drop across the main winding Lp is approximately VIN (neglecting the on voltage drop of the first power switch MP), and by means of the coupling relationship of the transformer TS, the voltage drop across the auxiliary winding La is also kept at VIN or approximately VIN when the number of turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during charging of the main stage winding Lp, the voltage at the first terminal of the normally-on switch MJ is vin+vo-vin=vo; when the first power switch MP is turned off, 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, and by the coupling relationship of the transformer TS, the voltage drop on the auxiliary winding La is also maintained to be-VO or approximately equal to-VO under the condition that the turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during the discharging period of the main stage winding Lp, the voltage at the first end of the normally-on switch MJ is vin+vo- (-VO) =vin+2vo, so that the normally-on switch MJ can take power from the second end of the auxiliary winding La and provide the power supply voltage for the driving module, regardless of the charging or discharging period of the transformer TS.

In comparison with the second power supply system 12, the auxiliary circuit 110 in the third power supply system 13 has exactly the same working principle for external power supply and demagnetization detection, and the description will not be repeated.

In one embodiment, the same-name end of the auxiliary winding La in the third power supply system 13 may also be coupled to the second end of the output capacitor CO, and the auxiliary circuit 110 may also perform the functions of external power supply and demagnetization detection by changing the turns ratio of the auxiliary winding La and the main winding Lp.

In one embodiment, the auxiliary winding La and the main winding Lp in the third power supply system 13 have opposite-positioned homonymous ends, and the detailed description will not be repeated.

In one embodiment, as shown in fig. 2c, the fourth power supply system 14 includes an input capacitor CIN, a load coupled in parallel with an output capacitor CO, an auxiliary circuit 110, a control module, a drive module, a fourth power stage 140 and an absorption circuit 141, the fourth power stage 140 including a primary winding Lp and a secondary winding Ls of a transformer TS, a freewheel module 121 and a first power switch MP; the snubber circuit 141 includes a snubber diode Dlp and a snubber capacitor Clp; the first end of the input capacitor CIN is coupled with the same-name end of the main-stage winding Lp and the second end of the absorption capacitor Clp, the second end of the input capacitor CIN is coupled with the ground, the first end of the absorption capacitor Clp is coupled with the same-name end of the auxiliary winding La and the cathode of the absorption diode Dlp, the same-name end of the auxiliary winding La is also the first end of the auxiliary winding La, the non-same-name end of the auxiliary winding La is the second end of the auxiliary winding La, the first end of the auxiliary winding La is coupled with the input voltage VIN of the first end of the input capacitor CIN after passing through the absorption capacitor Clp, and the second end of the auxiliary winding La is coupled with the first end of the normally-on switch MJ; the second end of the normally-on switch MJ provides a supply voltage VCC for supplying power, and the control end SWA of the normally-on switch MJ is coupled with the detection module; in one embodiment, the normally-on switch MJ is a Junction Field Effect Transistor (JFET), and when the control terminal of the JFET is grounded 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 supplying power to the driving module by using the pinch-off voltage of the JFET; the non-homonymous end of the main stage winding Lp is coupled with the first end of the first power switch MP and the anode of the absorption diode Dlp, and the control end of the first power switch MP is coupled with a first control signal GP output by the control module after passing through the driving module; the second end of the first power switch MP is grounded or grounded after passing through a current detection resistor, and a first control signal GP output by the control module controls the on and off of the first power switch MP; the first end of the output capacitor CO is coupled with the second end of the follow current module 121, the first end of the follow current module 121 is coupled with the non-homonymous end of the secondary winding Ls, and the homonymous end of the secondary winding Ls is coupled with the second end of the output capacitor CO; or the first end of the output capacitor CO is coupled to the non-homonymous end of the secondary winding Ls, the second end of the output capacitor CO is coupled to the first end of the freewheel module 121, and the second end of the freewheel module 121 is coupled to the homonymous end of the secondary winding Ls.

The fourth power supply system 14 belongs to a flyback power supply system, when the first power switch MP is turned on, the input voltage VIN charges the main winding Lp, at this time, the voltage drop across the main winding Lp is approximately VIN (neglecting the on-voltage drop of the first power switch MP), and by the coupling relationship of the transformer TS, the voltage drop across the auxiliary winding La is also kept at VIN or approximately VIN when the number of turns of the main winding Lp and the auxiliary winding La are the same or approximately the same; during charging of the primary winding Lp, the voltage at the first end of the normally-on switch MJ is (vin+ Nps ×vo) -vin= Nps ×vo, (Nps is the turns ratio of the primary winding Lp to 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, so that the secondary winding current Is charges the output capacitor CO, which Is equivalent to the voltage drop on the primary winding Lp being approximately-Nps ×vo (neglecting the conduction voltage drop of the snubber diode Dlp), and the voltage at the first end of the normally-on switch MJ Is (vin+ Nps ×vo) - (-Nps ×vo) =vin+2mps×vo during the secondary winding Ls discharge, so that the normally-on switch MJ can draw power from the second end of the auxiliary winding La and supply the power supply voltage to the driving module during the charging or discharging period of the transformer TS.

The operation principle of the auxiliary circuit 110 in the fourth power supply system 14 is identical to that of the second power supply system 12, and the description will not be repeated.

In one embodiment, the homonymous terminal of the auxiliary winding La in the fourth power supply system 14 may also be coupled to a first terminal of the input capacitance CIN.

In one embodiment, the auxiliary winding La and the main winding Lp in the fourth power supply system 14 have the same-name ends in opposite positions, and the detailed description will not be repeated.

In one embodiment, as shown in fig. 2d, the fifth power supply system 15 includes an input capacitor CIN, a load coupled in parallel with an output capacitor CO, an auxiliary circuit 110, a control module, a drive module, and a fifth power stage 150, the fifth power stage 150 including a main stage winding Lp, a freewheel module 121, and a first power switch MP; the first end of the input capacitor CIN is coupled with the homonymous end of the main stage winding Lp and the homonymous end of the secondary winding La; the same-name end of the auxiliary winding La is also the first end of the auxiliary winding La, the non-same-name 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 with the input voltage VIN of the first end of the input capacitor CIN, and the second end of the auxiliary winding La is coupled with the first end of the normally-on switch MJ; the second end of the normally-on switch MJ provides a supply voltage VCC for supplying power, and the control end of the normally-on switch MJ is coupled with the detection module; in one embodiment, the normally-on switch MJ is a Junction Field Effect Transistor (JFET), and when the control terminal of the JFET is grounded, the highest voltage at the second terminal of the JFET is the pinch-off voltage of the JFET, which is equivalent to that of the normally-on switch MJ supplying power to the driving module by using the pinch-off voltage of the JFET; the non-homonymous end of the main stage winding Lp is coupled with the first end of the first power switch MP and the first end of the follow current module 121, the second end of the follow current module 121 is coupled with the first end of the output capacitor CO, the second end of the output capacitor CO is grounded, and the control end of the first power switch MP is coupled with a first control signal GP output by the control module after passing through the driving 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 on and off of the first power switch MP.

The fifth power supply system 15 belongs to a boost power supply system, and when the first power switch MP is turned on, the input voltage VIN charges the main winding Lp, at this time, the voltage drop across the main winding Lp is approximately VIN (neglecting the conduction voltage drop of the first power switch MP), and by the coupling relationship of the transformer TS, the voltage drop across the auxiliary winding La is also kept to be VIN or approximately VIN when the number of turns of the main winding Lp is the same or approximately the same, and the voltage drop across the auxiliary winding La is smaller than VIN when the number of turns of the main winding Lp is greater than the number of turns of the auxiliary winding La (for example, the number of turns of the main winding Lp is 2 times the number of turns of the auxiliary winding La, and then the voltage drop across the auxiliary winding La is 0.5 times the voltage drop across the main winding Lp); when the number of turns of the main winding Lp is 2 times that of the auxiliary winding La, the voltage at the first end of the normally-on switch MJ is VIN-0.5×vin=0.5×vin during charging of the main winding Lp; when the first power switch MP is turned off, the difference between the load voltage VO on the output capacitor CO and the input voltage VIN discharges the main winding Lp, at this time, the voltage drop on the main winding Lp is approximately VO-VIN, and when the number of turns of the main winding Lp is 2 times that of the auxiliary winding La, the voltage drop on the auxiliary winding La is also kept to be 0.5 x (VO-VIN) through the coupling relationship of the transformer TS; during the discharging period of the main winding Lp, the voltage at the first end of the normally-on switch MJ is vin+0.5 (VO-VIN) =0.5 (vo+vin), so that the normally-on switch MJ can take power from the second end of the auxiliary winding La and supply the power supply voltage to the driving module during the charging or discharging period of the transformer TS.

The operation principle of the auxiliary circuit 110 in the fifth power supply system 15 is identical to that of the second power supply system 12, and the description will not be repeated.

In one embodiment, the homonymous terminal of the auxiliary winding La in the fifth power supply system 15 may also be coupled to the first terminal of the output capacitance CO.

In one embodiment, the auxiliary winding La and the main winding Lp in the fifth power supply system 15 have opposite-positioned homonymous ends, and the detailed description of the analysis will not be repeated.

In one embodiment, as shown in fig. 4, the difference between the sixth power system 16 and the first power system 11 is that, in the sixth power system, if the high-voltage transcapacitive Cds parasitic between the first terminal and the control terminal SWA of the normally-on switch MJ are smaller and the demagnetized state of the transformer cannot be detected, an auxiliary capacitor Ch is added between the first terminal and the control terminal SWA of the normally-on switch MJ by the second auxiliary circuit 111 to help to realize detection of the demagnetized state of the transformer TS.

In the above embodiments, in order to conveniently, more clearly and simply describe the working principle of the present invention, the description only exemplifies the case that the number of turns of the main winding Lp and the auxiliary winding La of the transformer TS is the same, and in the practical implementation process, the number of turns of the main winding Lp and the auxiliary winding La of the transformer TS may be kept different, but the working principle of the present invention is not affected.

As can be seen from the above embodiments, the connection relation between the first power stage 100 and the input capacitor CIN and the output capacitor CO can be combined to form any one of a Buck power supply system (Buck), a Boost power supply system (Boost), a Flyback power supply system (Flyback) and a Buck-Boost power supply system (Buck Boost).

In a third aspect, the present invention also provides an electronic device comprising any one of the power supply systems according to the second aspect.

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

the auxiliary circuit can provide power supply voltage to the outside through sharing the normally-on switching tube, and simultaneously realize detection of the demagnetizing state of the transformer.

It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to be referred to each other.

It should also be noted that, in this document, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements to be referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Moreover, relational terms such as "first" and "second" may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions, or order, and without necessarily being construed as indicating or implying any relative importance. "and/or" means either or both of which may be selected. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or terminal device comprising the element.

The foregoing has outlined rather broadly the more detailed description of the invention in order that the detailed description of the invention that follows may be better understood, and in order that the present contribution to the art may be better appreciated. While various modifications of the embodiments and applications of the invention will occur to those skilled in the art, it is not necessary and not intended to be exhaustive of all embodiments, and obvious modifications or variations of the invention are within the scope of the invention.

Claims

1. An auxiliary circuit for use in a power supply system having a transformer and an input capacitor, the transformer having at least an auxiliary winding and a primary winding, the auxiliary circuit comprising:

The detection module is coupled with the control end of the normally-on switch and is configured to compare the voltage or the current of the control end of the normally-on switch with a preset reference voltage or a preset reference current during the demagnetization of the transformer, so as to obtain a demagnetization signal representing the end of the demagnetization of the transformer.

2. The auxiliary circuit according to claim 1, wherein the auxiliary winding and the main winding have identical terminals at the same position, and the detection module outputs a demagnetization signal indicating the end of demagnetization of the transformer when the voltage of the control terminal of the normally-on switch is lower than a preset reference voltage during demagnetization of the transformer; or (b)

And the detection module outputs a demagnetizing signal representing the end of demagnetization of the transformer when the current flowing out of the control end of the normally-on switch is larger than a preset reference current source during the demagnetization of the transformer.

3. The auxiliary circuit according to claim 2, wherein the detection module comprises a hysteresis comparator and a pull-down resistor, wherein an in-phase end of the hysteresis comparator is coupled to the preset reference voltage or zero voltage, an inverting end of the hysteresis comparator is coupled to a first end of the pull-down resistor and a control end of the normally-on switch, a second end of the pull-down resistor is coupled to the preset reference voltage or zero voltage, and when the voltage of the inverting end of the hysteresis comparator is lower than the voltage of the in-phase end, an output end of the hysteresis comparator outputs a demagnetization signal representing that demagnetization of the transformer is finished; or (b)

4. The auxiliary circuit of claim 1, wherein the normally-on switch is one of a junction field effect transistor, or a depletion mode metal oxide semiconductor field effect transistor, or a depletion mode gallium nitride transistor GaN.

5. The auxiliary circuit of claim 4, wherein an auxiliary capacitor capable of withstanding high voltage is arranged between the first end and the control end of the normally-on switch to assist in detecting the demagnetized state of the transformer when the parasitic transcapacitive between the first end and the control end of the normally-on switch is small.

6. A power supply system at least comprising the auxiliary circuit as claimed in any one of claims 1 to 5, wherein the power supply system further comprises a control module and a driving module, the auxiliary circuit supplies power to the driving module through the second end of the normally-on switch, and outputs a demagnetization detection signal to the input end of the control module after demagnetization of the transformer is finished; the first control signal output by the control module is coupled with the control end of the first power switch after passing through the driving module, and the on and off of the first power switch are controlled.

7. The power system of claim 6, further comprising an output capacitor and a power stage coupled in parallel with the load; the power stage includes at least a primary winding of a transformer, a freewheel module, and a first power switch.

8. The power system of claim 7, further comprising a driver chip including at least a normally-on switch, a detection module, a control module, and a driver module.

9. The power system of claim 7, wherein the power stage is coupled to the input capacitor and the output capacitor to form any one of a buck power system, a boost power system, a flyback power system, and a buck-boost power system.

10. An electronic device comprising the power supply system of any one of claims 6 to 9.