CN114583984A

CN114583984A - Power supply circuit and power supply conversion system and control chip thereof

Info

Publication number: CN114583984A
Application number: CN202111317311.7A
Authority: CN
Inventors: 叶俊; 俞秀峰; 林官秋
Original assignee: Shenzhen Biyi Microelectronics Co ltd
Current assignee: Shenzhen Biyi Microelectronics Co ltd
Priority date: 2021-11-09
Filing date: 2021-11-09
Publication date: 2022-06-03

Abstract

The invention provides a power supply circuit, a power supply conversion system and a control chip thereof. The power supply circuit is used for supplying power for the control drive circuit, and the power supply circuit obtains the power supply input voltage through auxiliary winding, and the power supply circuit includes: a switching circuit; a linear circuit, wherein the output of the switching circuit and the output of the linear circuit are combined and provide a supply voltage for powering the control drive circuit; and a selection control circuit for selectively enabling the switch circuit or the linear circuit, and controlling the duty ratio of the switch or the conduction degree of the linear device according to the power supply voltage so as to control the power supply voltage to be stabilized near the reference voltage. The invention can expand the output range of the output voltage, has stable power supply voltage and lower standby loss, and has higher power density and power efficiency.

Description

Power supply circuit and power supply conversion system and control chip thereof

Technical Field

The invention relates to the field of electronics, in particular but not limited to a power supply circuit, a power supply conversion system and a control chip thereof.

Background

Power converters are indispensable components in electronic systems. As is well known, power converters include two main types, namely, a linear converter and a switching power converter, and can be divided into two types, namely, an isolated type and a non-isolated type in terms of conversion mode. In the case of a switching power supply, the isolated converter is widely applied, because the isolated converter can protect a load from being impacted and damaged by high voltage of an input bus, and the isolated converter has wide application in telecommunication wireless networks, automobiles and medical equipment. Among various topologies of the isolated Converter, the Flyback Converter topology does not need to output a filter inductor, so that the circuit has the advantages of simple structure, isolated output and low cost, and occupies a high proportion in the application of terminal equipment. The isolated power conversion system is used in the power adapter of the USB-PD quick-charging protocol due to the advantages.

Fig. 1 shows a schematic diagram of an isolated flyback converter applied to a medium-small power adapter, where the architecture is controlled by a secondary feedback ssr (secondary Side regulation), which is a mainstream control architecture of the medium-small power adapter at present. Fig. 1 shows a widely used flyback power conversion system for converting Alternating Current (AC) to Direct Current (DC). The system comprises: the power supply comprises a full bridge rectifier, a power controller, a transformer, a primary side power MOS switch, a current detection resistor, a secondary side rectifier filter and an isolation feedback compensation network. The power controller is used for controlling a power device MOS of the driving power supply conversion system so as to regulate the output voltage Vout. In a starting stage of the flyback conversion system, generally, power is taken from a bus through a starting resistor Rst (as shown in fig. 1) or a high-voltage starting Junction Field Effect Transistor (JFET) tube built in a chip, and the power is used for supplying power to a circuit in a power controller. After the start-up is finished, the auxiliary winding La (shown in fig. 1) continuously supplies power to the power controller chip. However, the voltage of the auxiliary winding La is limited by the variation of the output voltage Vout, which causes the supply voltage VDD of the flyback converter system to vary, approximately equal to (Na/Ns) × Vout, where Na is the number of auxiliary winding turns and Ns is the number of secondary winding turns.

However, in the PD fast charging situation, the output voltage Vout required by the load provided by the power conversion system has a large variation range, for example, for PD3.0, the output voltage Vout varies from 3V to 21V, which requires that the operating range of the power supply voltage VDD also varies greatly. For example, when the minimum operating voltage of the supply voltage VDD is 10V, which means that the supply voltage VDD needs to provide a supply voltage of 10V even when the output voltage Vout is low, for example, when the voltage is 3V, and accordingly, when the output voltage Vout is 21V, the supply voltage VDD may be as high as 70V, but a high supply voltage means that the requirement for the withstand voltage of the supply voltage pin VDD is high, and when the supply voltage VDD is high, the loss of the supply circuit inside the chip is large, and the heat generation is a big problem. In addition, in many cases, such as gan drive, the supply voltage is required to be a value that varies only slightly or is fixed and does not vary with the voltage of the auxiliary winding.

In view of the above, it is desirable to provide a new power supply circuit for supplying power to the control chip of the power conversion system, so as to be able to adapt to a larger output voltage Vout variation range in the PD fast charging situation.

Disclosure of Invention

At least in view of one or more problems in the background art, the present invention provides a power supply circuit, a power conversion system and a control chip thereof.

According to an aspect of the present invention, a power supply circuit for a power conversion system is provided, wherein the power supply circuit is configured to supply power to a control driving circuit, the control driving circuit is configured to control a power device of the power conversion system, the power supply circuit obtains a power supply input voltage by coupling to an auxiliary winding of the power conversion system, and the power supply circuit includes: the switching circuit comprises a switch, and the output voltage of the output end of the switching circuit is adjusted by adjusting the duty ratio of the switch; the linear circuit comprises a linear device, the output voltage of the output end of the linear circuit is adjusted by adjusting the conduction degree of the linear device, and the output end of the switch circuit and the output end of the linear circuit are combined and provide a power supply voltage for supplying power to the control drive circuit; and a selection control circuit for receiving a voltage detection signal representing the supply voltage and a reference signal representing the reference voltage, selectively enabling the switch circuit or the linear circuit based on the supply voltage or the supply input voltage, and controlling the duty ratio of the switch and the conduction degree of the linear device in stages according to the voltage detection signal and the reference signal to control the supply voltage to be stabilized near the reference voltage.

In one embodiment, the switch circuit comprises a boost circuit, the boost circuit comprises a switch, an inductor and a rectifier tube, wherein the first end of the inductor is coupled with the first end of the switch and the first end of the rectifier tube, the second end of the inductor is coupled with the auxiliary winding through a diode, the second end of the switch is grounded, the second end of the rectifier tube is the output end of the switch circuit, when the boost circuit is enabled by the selection control circuit, the switch and the rectifier tube are alternately conducted, a linear device in the linear circuit is turned off, and when the linear circuit is enabled by the selection control circuit, the boost circuit stops working, and the linear device is conducted.

In one embodiment, the selection control circuit includes: the voltage detection circuit is used for detecting the power supply voltage and providing a voltage detection signal; a comparison circuit that compares the voltage detection signal with a threshold signal; and a switching control circuit that enables the switching circuit or the linear circuit based on a comparison result of the comparison circuit.

In one embodiment, the selection control circuit further comprises a switch control circuit, the switch control circuit receives the voltage detection signal and the reference signal and provides a switch control signal, when the switch control circuit enables the switch circuit, the switch control signal controls the switch, and the duty ratio of the switch is controlled to control the power supply voltage to be stabilized near the reference voltage.

In one embodiment, the comparison circuit comprises a hysteresis comparison circuit, the threshold signal and the reference signal are the same signal, and the switch control circuit comprises: an oscillation circuit that provides an oscillation signal; and a switching control signal generation circuit that generates a switching control signal based on the oscillation signal and an output signal of the comparison circuit.

In one embodiment, a switch control circuit includes: a second comparison circuit that compares the voltage detection signal with the reference signal; an oscillation circuit that provides an oscillation signal; and a switching control signal generation circuit that generates a switching control signal based on the comparison result of the second comparison circuit and the oscillation signal.

In one embodiment, the selection control circuit further comprises a linear control circuit, the linear control circuit receives the voltage detection signal and the reference signal and provides a linear control signal, when the switching control circuit enables the linear circuit, the linear control signal controls the linear device, and the power supply voltage is controlled to be stabilized near the reference voltage by controlling the conduction degree of the linear device.

In one embodiment, the linear control circuit includes: and the first end of the error amplifying circuit receives the voltage detection signal, the second end of the error amplifying circuit receives the reference signal, and the output end of the error amplifying circuit is coupled with the control end of the linear device and used for providing a linear control signal.

In one embodiment, a rectifier tube in the switching circuit and a linear device in the linear circuit are multiplexed with the same switching device, and the switching device is selectively controlled to work in a switching state or a linear state according to the power supply voltage.

According to another aspect of the present invention, a power conversion system includes the power device, the power supply circuit and the control driving circuit as described in any of the above embodiments.

In one embodiment, the power conversion system is used in a power adapter of a PD fast charging protocol.

In one embodiment, the power device includes a gallium nitride field effect transistor.

According to another aspect of the present invention, a control chip for a power conversion system has a first pin and a second pin, wherein the first pin is externally used for coupling a first end of an inductor, a second end of the inductor is used for coupling a first capacitor and coupling an auxiliary winding through a diode, and the second pin is used for coupling a second capacitor, the control chip includes: the switch circuit comprises a switch and a rectifying tube, wherein the first end of the switch is coupled with the first pin, the second end of the switch is coupled with the first end of the rectifying tube, and the second end of the rectifying tube is coupled with the second pin; the linear circuit comprises a linear device, wherein a first end of the linear device is coupled with the first pin, and a second end of the linear device is coupled with the second pin; the selection control circuit controls the enabling switch circuit or the linear circuit based on the voltage on the second pin or the voltage on the first pin and controls the voltage on the second pin to be stabilized near the reference voltage based on the voltage on the second pin; and the control driving circuit is provided with a power supply end and a signal output end, wherein the power supply end is coupled with the second pin, and the signal output end is used for driving a power device of the power conversion circuit.

In one embodiment, the control chip further has a third pin for externally coupling a control terminal of the power device, wherein the signal output terminal of the control driving circuit is coupled to the third pin.

According to another aspect of the present invention, a control chip for a power conversion system has a first pin and a second pin, wherein the first pin is externally coupled to a first capacitor and is coupled to an auxiliary winding through a diode, the second pin is coupled to a second capacitor, and the control chip comprises: the switch circuit comprises an inductor, a switch and a rectifying tube, wherein the first end of the inductor is coupled with the first end of the switch, the second end of the inductor is coupled with a first pin, the second end of the switch is coupled with the first end of the rectifying tube, and the second end of the rectifying tube is coupled with a second pin; the linear circuit comprises a linear device, wherein a first end of the linear device is coupled with a first pin or a first end of an inductor, and a second end of the linear device is coupled with a second pin; the selection control circuit controls the enabling switch circuit or the linear circuit based on the voltage of the second pin or the voltage of the first pin, and controls the voltage on the second pin to be stabilized near the reference voltage based on the voltage of the second pin; and the control driving circuit is provided with a power supply end and a signal output end, wherein the power supply end is coupled with the second pin, and the signal output end is used for driving a power device of the power conversion circuit.

The power supply circuit, the power supply conversion system and the control chip thereof provided by the invention can expand the output range of the output voltage, have stable power supply voltage and lower standby loss, and have higher power density and power supply efficiency.

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

Fig. 1 shows an isolated flyback converter schematic;

FIG. 2 illustrates a schematic diagram of a power conversion system according to an embodiment of the invention;

FIG. 3 shows a schematic diagram of a power supply circuit according to an embodiment of the invention;

FIG. 4 illustrates a waveform diagram of a supply voltage versus a supply input voltage provided by an auxiliary winding, according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a switch circuit and a switch control circuit according to an embodiment of the invention;

FIG. 6 shows a control chip schematic according to an embodiment of the invention;

FIG. 7 shows a schematic diagram of a power supply circuit according to an embodiment of the invention;

fig. 8 shows a linear circuit embodiment according to an embodiment of the invention.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

The description in this section is for several exemplary embodiments only, and the present invention is not limited only to the scope of the embodiments described. Combinations of different embodiments, and substitutions of features from different embodiments, or similar prior art means may be substituted for or substituted for features of the embodiments shown and described.

The term "coupled" or "connected" in this specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a conductor, wherein the electrically conductive medium may contain parasitic inductance or parasitic capacitance, or through an intermediate circuit or component as described in the embodiments in the specification; indirect connections may also include connections through other active or passive devices that perform the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, and so on. "plurality" or "plurality" means two or more.

Fig. 2 shows a schematic diagram of a power conversion system according to an embodiment of the invention. In the illustrated embodiment, the power conversion system is an isolated Flyback power conversion (Flyback) system, which includes a primary circuit and a secondary circuit, isolated by a transformer, wherein the primary circuit has a primary winding Lp and a power device Q1. The illustrated power conversion system is a flyback voltage converter structure, and in other embodiments, the power conversion system may also adopt other topologies, such as a forward voltage converter, a Buck voltage converter, and the like, for example, an auxiliary winding obtains an auxiliary voltage source through transformer and inductive coupling. The power device Q1 may be any suitable power device for performing a switching action or regulating the output voltage Vout of the power conversion system via a controlled conduction level. In one embodiment, the power device Q1 includes a Metal Oxide Semiconductor Field Effect Transistor (MOSFET). In another embodiment, the power device Q1 includes a power transistor. In one embodiment, power device Q1 includes a gallium nitride (GaN) power tube. The secondary circuit has a secondary winding Ls and a rectifier Do. Based on the control of the power device Q1, the power conversion system converts the input bus voltage Vbus of the input primary circuit into the output voltage Vout of the output end of the secondary circuit, for driving the load. In one embodiment, the output voltage Vout is a voltage source satisfying the USB-PD fast charge protocol, and the power conversion system is used in a PD fast charge power adapter. The power conversion system further comprises an auxiliary winding La, a first capacitor C1, a second capacitor C2, a diode D1, an inductor L1 and a control chip 20, wherein the control chip 20 comprises a control driving circuit 22 for controlling the power device Q1 and a power supply circuit 21 for supplying power to the control driving circuit 22. The power supply circuit 21 may also include an inductor L1. The supply circuit 21 obtains a supply input voltage Vin by coupling the auxiliary winding La. The first end of the auxiliary winding La is coupled to the anode of the first diode D1, the second end of the auxiliary winding La is grounded GND, the cathode of the diode D1 is coupled to the inductor L1 and the first capacitor C1, and the other end of the first capacitor C1 is grounded GND. The voltage Vin across the first capacitor C1 is used to provide a voltage source to the supply circuit 21. The supply input voltage Vin may also be used to input a feedback signal to the control drive circuit 22 for control. One end of the second capacitor C2 is coupled to the output end of the power supply circuit 21, the other end is grounded, and the voltage on the second capacitor C2 is the power supply voltage VDD.

The power supply circuit 21 includes a switch circuit 211, a linear circuit 212, and a selection control circuit 213. Wherein the switching circuit 211 comprises a switch. In another embodiment, the switching circuit further comprises an inductor L1. Preferably, the switch circuit is a Boost (Boost) circuit, and includes an inductor L1 coupled to the auxiliary winding La through a diode D1, a switch T1 coupled to a first end of the inductor L1, and a rectifier tube coupled to a first end of the inductor L1 and the switch T1, and the other end of the rectifier tube serves as an output end of the switch circuit 211. In other embodiments, the first pin SW of the control chip 20 is directly coupled to the cathode of the diode D1, and the switch circuit 211 may also include a Buck-boost (Buck-boost) circuit or other types or structures of switch circuits. The linear circuit 212 includes a linear device, wherein a first terminal of the linear device is coupled to the first pin SW. The output of the switching circuit 211 and the output of the linear circuit 212 are combined to provide the supply voltage VDD. The output terminal of the switch circuit 211 may be directly coupled to the output terminal of the linear circuit 212 at the first terminal of the second capacitor C2, i.e. at the second pin VDD, for providing the supply voltage VDD. The output of the switching circuit 211 and the output of the linear circuit 212 may also be coupled to two inputs of the composite circuit and provide the supply voltage VDD through the output of the composite circuit. In one embodiment, the composite circuit includes two switching tubes, wherein input terminals of the two switching tubes are respectively coupled to the output terminal of the linear circuit and the output terminal of the switching circuit, output terminals of the two switching tubes are coupled to the output terminal of the power supply circuit, and control terminals of the two switching tubes are respectively coupled to the switch enable output terminal and the linear enable output terminal of the selection control circuit. When the output voltage Vout is low, the power supply input voltage Vin is also low, and at this time, the selection control circuit 213 selects the switch boosting circuit 211 to operate, and controls the power supply voltage VDD at the reference voltage, which is higher than the power supply input voltage Vin, so that the boosting circuit 211 boosts the power supply input signal Vin and supplies power to the control drive circuit 22. When the output voltage Vout is high, the power supply input voltage Vin is also high, the selection control circuit 213 enables the linear circuit 212, stabilizes the power supply voltage VDD at the reference voltage by controlling the conduction degree of the linear device, and is configured to lower the power supply voltage VDD than the power supply input voltage Vin, and supply power to the control drive circuit 22 after voltage reduction. Preferably, the selection control circuit 213 determines the level of the power supply input voltage Vin by detecting the power supply voltage VDD, and enables the switch circuit 211 or the linear circuit 212 based on the power supply voltage VDD. The selection control circuit 213 may receive a voltage detection signal indicative of the supply voltage VDD and a reference signal indicative of a reference voltage, and enable the switching circuit 211 or the linear circuit 212 based on a comparison of threshold signals associated with the voltage detection signal and the reference signal. In one embodiment, when the switch circuit 211 is in operation, if the power supply voltage VDD is higher than a first predetermined threshold, where the first predetermined threshold is greater than the reference voltage, which indicates that the power supply input voltage Vin is higher, the selection control circuit 213 disables the switch circuit 211, enables the linear circuit 212, and stops the operation of the switch circuit 211. When the linear circuit 212 works, if the power supply voltage is lower than a second preset threshold, where the second preset threshold is smaller than the power supply voltage reference voltage, which indicates that the power supply input voltage Vin is lower, the selection control circuit 213 disables the linear circuit 212, enables the switch circuit 211, and the switch circuit 211 starts to supply power. Further, the selection control circuit 213 controls the duty ratio of the switch in the switch circuit 211 or the conduction degree of the linear device in the linear circuit 212 according to the voltage detection signal and the reference signal to control the supply voltage VDD to be stabilized around the reference voltage.

The control drive circuit 22 is supplied with the supply voltage VDD supplied from the supply circuit 21. The control drive circuit 22 outputs a control drive signal GATE for controlling the power device Q1 to regulate the output voltage Vout of the power conversion system. The control driving circuit 22 has a power supply terminal and a signal output terminal, wherein the power supply terminal is coupled to the output terminal of the power supply circuit 21 and the pin VDD, so that the power supply circuit 21 supplies power to the control driving circuit 22. The signal output terminal provides an output driving signal GATE. Specifically, the control drive circuit 22 includes a control circuit for generating a pulse width modulation signal PWM and a drive circuit for amplifying the PWM signal for outputting a drive signal GATE to drive the power device Q1. The control circuit and the drive circuit are powered by a supply voltage VDD supplied by the supply circuit 21. By selecting the switch circuit 211 or the linear circuit 212 to operate under different power supply input voltages Vin, the power supply voltage VDD can be stabilized near the reference voltage in a wider range of the power supply input voltage Vin, and the stabilized power supply voltage VDD is provided to the control driving circuit 22, so that the power device Q1 is effectively driven, and the output voltage regulation of the power conversion system in a wider range is realized. Meanwhile, the control chip 20 has fewer external peripheral elements, the control chip has a simple circuit, and the control chip 20 has lower loss during no-load, higher power density and higher power efficiency.

In the illustrated embodiment, the control chip 20 has a first pin SW, a second pin VDD, a third pin GATE, and a ground pin GND. Of course, the control chip 20 may have other pins, for example, for receiving a current feedback signal or other feedback signals. The first pin SW is coupled to a first terminal of an inductor L1, and a second terminal of the inductor L1 is coupled to a first terminal of a capacitor C1 and a cathode of a diode D1. An anode of the diode D1 is coupled to a first end of the auxiliary winding La. The second terminal of the auxiliary winding La and the second terminal of the capacitor C1 are connected to ground GND. The first pin SW is coupled to the power supply circuit 21. Of course, in other embodiments, the inductor L1 may also be part of the power supply circuit, or may also be part of the switch circuit 211 in the power supply circuit. The first pin SW is for receiving a supply input voltage source from the auxiliary winding La. The second pin VDD is coupled to the second capacitor C2, and coupled to the output terminal of the power supply circuit 21 and the power supply terminal of the control driving circuit 22 for providing a power supply voltage for the control driving circuit 22. The third pin GATE is coupled to a signal output terminal of the control driver circuit 22 for driving the power device Q1. The selection control circuit 213 controls the enable switch circuit 211 or the linear circuit 212 based on the voltage on the second pin VDD or the voltage on the first pin SW and serves to control the voltage on the second pin VDD to be stabilized around the reference voltage based on the voltage on the second pin VDD.

In one embodiment, the control chip 20 is fabricated in an electronic package, which may have one or more dies therein. In another embodiment, the control chip 20 is fabricated on a semiconductor substrate.

In another embodiment, the power device Q1 may also be integrated inside the control chip.

Fig. 3 shows a schematic diagram of a supply circuit according to an embodiment of the invention. The power supply circuit comprises a switch circuit 31, a linear circuit 32 and a main selection control circuit 33, wherein the switch circuit 31 comprises a switch T1 and a rectifier switch T2, and the switch circuit and the inductor L1 form a booster circuit together. The switch T1 and the rectifier T2 may be MOSFETs or transistors. The rectifier T2 may be replaced by a diode. The first terminal of the inductor L1 is coupled to the first terminal of the switch T1 and the first terminal of the rectifier switch T1, the second terminal of the inductor L1 is coupled to the auxiliary winding La through the diode D1, the second terminal of the switch T1 is grounded to GND, and the second terminal of the rectifier switch T2 serves as the output terminal of the switch circuit 31. When the switch T1 is turned on, the first terminal SW of the inductor L1 is pulled to ground, the inductor L1 charges, and when the switch T1 is turned off, the rectifier T2 is turned on, and the inductor L1 charges the second capacitor C2.

The linear circuit 32 includes a linear device T3, and the linear device T3 may also be a MOSFET or a transistor, and operate in a linear region. In one embodiment, the rectifier switch T2 and the linear device T3 are both PMOS (P-type MOSFET). In the illustrated embodiment, a first terminal of the linear device T3 is coupled to the first pin SW, i.e., a first terminal of the inductor L1, and a second terminal of the linear device T3 is coupled to an output terminal of the switch circuit 31 as an output terminal of the linear circuit 32, and is commonly coupled to a first terminal of the second capacitor C2 for providing the supply voltage VDD for the control driving circuit. When the selection control circuit enables the linear circuit 32 and the disable switch circuit 31 to be not operated, the inductor L1 can be regarded as a conducting wire for transferring the rectified and filtered supply input voltage Vin transferred by the auxiliary winding La to the linear circuit 32, and after being converted by the linear circuit 32, the supply voltage VDD is provided at the first end of the second capacitor C2.

The selection control circuit 33 includes a voltage detection circuit 34, a comparison circuit 35, a switching control circuit 36, a switch control circuit 37, and a linearity control circuit 38. Wherein the voltage detection circuit 34 includes a voltage divider circuit composed of resistors R1 and R2, the voltage detection circuit providing a voltage detection signal Vs indicative of the supply voltage VDD. The comparator circuit 35 compares the voltage detection signal Vs with the threshold signal Vth, and controls the switching control circuit 36 based on the comparison result to enable the switch circuit 31 or the linear circuit 42. The threshold signal Vth may be associated with a reference signal that characterizes a stable value of the supply voltage VDD. In one embodiment, the threshold signal Vth received by the comparison circuit 35 is a reference signal. In one embodiment, the comparison circuit 35 comprises a hysteresis comparator for comparing with the first threshold signal and the second threshold signal, respectively. In another embodiment, the comparison circuit 35 includes a plurality of comparators for comparing the voltage detection signal Vs with a first threshold signal, a second threshold signal, and a reference signal, respectively, wherein the first threshold signal is greater than the reference signal, and the reference signal is greater than the second threshold signal. The switching control circuit 36 enables the switch circuit 31 or the linear circuit 32 based on the comparison result of the comparison circuit 35. When the voltage boost circuit 31 is in operation, if the voltage detection signal Vs is greater than the first threshold signal, which indicates that the power supply input voltage Vin is too high, the selection control circuit 33 disables the switch circuit 31, enables the linear circuit 32, stops the operation of the voltage boost circuit 31, and turns on the linear device T3, so that the power supply voltage VDD is lower than the power supply input voltage Vin. In the operating state of the linear circuit 32, when the voltage detection signal Vs is lower than the second threshold signal, which indicates that the power supply input voltage Vin is too low, the selection control circuit 33 enables the voltage boost circuit 31 to control the switch T1 and the rectifier tube T2 to operate in the alternate conducting state, and the linear device T3 in the linear circuit 32 is turned off, so that the power supply voltage VDD is boosted to be greater than the power supply input voltage Vin. Meanwhile, the control of the switch circuit 31 and the linear circuit 32 is also performed based on the supply voltage VDD, and by such control, stable supply voltage can be provided under the full-range output voltage Vout only based on the detection of the supply voltage VDD without inputting the supply voltage, so that the complexity of the system is reduced, the number of high-resistance devices is reduced, the volume of the system is reduced, and the density of power devices is improved.

The switch control circuit 37 receives the voltage detection signal Vs and the reference signal to provide a switch control signal CT1 for controlling the switch T1 and the rectifier T2, and when the switch control circuit 36 enables the switch circuit 31, the switch control signal controls the switch T1 to control the power supply voltage VDD to be stabilized around a reference voltage by controlling the duty ratio of the switch T1, wherein the reference voltage is the ratio of the reference signal to the gain of the voltage detection circuit. In one embodiment, the reference signal is the same signal as the threshold signal Vth. In another embodiment, the reference signal is a different signal from the threshold signal Vth, and the switch control circuit includes a second comparison circuit for comparing the voltage detection signal Vs and the reference signal, and generating the switch control signal based on the voltage detection signal Vs and the reference signal. In another embodiment, the rectifier tube is replaced with a diode.

The linear control circuit 38 receives the voltage detection signal Vs and the reference signal, and provides a linear control signal CT2, when the switching control circuit 36 enables the linear circuit (e.g., EN2 is active), the linear control signal CT2 controls the linear device T3, and controls the power supply voltage VDD to be stabilized around the reference voltage by controlling the conduction degree of the linear device T3. The linear control circuit 38 may be a closed-loop negative feedback control circuit, and may receive the voltage detection signal Vs, or may use independent voltage dividing resistors R3 and R4 to obtain the value of the supply voltage VDD. The linear control circuit comprises an error amplifying circuit EA, wherein a first end of the error amplifying circuit EA receives a voltage detection signal, a second end of the error amplifying circuit EA receives a reference signal Vref, an output end of the error amplifying circuit EA is coupled to a control end of the linear device T3 and used for providing a linear control signal CT2, and the error amplifying circuit EA is used for carrying out error amplification on a divided voltage of VDD and the reference signal Vref so as to control the conduction degree of the linear device T3. In another embodiment, the linear circuit 38 may also employ a voltage regulator clamp control as shown in fig. 8.

By such control, the supply voltage VDD does not vary with the voltage across the auxiliary winding La, i.e. with the variation of the output voltage Vout of the switching power supply converter system, and a stable supply voltage VDD can be provided, suitable for example for gallium nitride driving.

Fig. 4 shows a waveform diagram of a supply voltage versus a supply input voltage provided by an auxiliary winding according to an embodiment of the invention. The power supply input voltage Vin reflects the voltage on the auxiliary winding, i.e. the output voltage of the power conversion system. It can be seen that the supply voltage VDD is regulated around a fixed value throughout the range of variation of the supply input voltage Vin.

Fig. 5 shows a schematic diagram of a switch circuit and a switch control circuit according to an embodiment of the invention. The switch circuit is a boost circuit, and includes an inductor L1, a switch T1, and a rectifier T2, and an output terminal of the boost circuit is coupled to the capacitor C2 for providing the supply voltage VDD. The switch control circuit includes a comparison circuit 51, an oscillation circuit 52, and a switch control signal generation circuit 53, wherein the comparison circuit 51 compares a voltage detection signal Vs representing the supply voltage VDD with a reference signal Vref. The oscillation circuit 52 supplies an oscillation signal, and the switch control signal generation circuit 53 supplies a switch control signal CT1 for driving the switch T1 based on the comparison result of the comparison circuit 51 and the oscillation signal. In one embodiment, the comparison circuit 51 is shared with the comparison circuit 35 in fig. 3, and is used for comparing the voltage detection signal Vs with the reference signal Vref, and the output of the blanking oscillation circuit 52 is turned on and off by the output of the comparison circuit 51, so as to realize the voltage stabilization of the power supply voltage VDD. In another embodiment, the comparison circuit 51 is a second comparison circuit independent from the comparison circuit 35 in fig. 3, for comparing the voltage detection signal Vs and the reference signal Vref. The control mode is simple to control and does not need a loop error amplifier and a compensation loop. The control signal of the rectifier tube T2 is in anti-phase with the switching control signal CT 1. In another embodiment, the rectifier tube is a diode, and control signals are not needed for control. Of course, the switch control circuit may also adopt other manners, such as a compensation amplifying circuit can be included for closed-loop control.

FIG. 6 shows a control chip schematic according to an embodiment of the invention. In this embodiment, the inductor L1 coupled to the cathode of the diode D1 and the first capacitor C1 is fabricated inside the control chip 60. In contrast to the control chip 20 in the embodiment of fig. 2, the first pin Vin of the control chip 60 is directly coupled to the cathode of the diode D1. The connection manner of the inductor L1 and other components of the power supply circuit may be the connection manner shown in fig. 3, wherein a first end of the inductor L1 is coupled to the first end of the switch T1 and the first end of the linear device T2, and a second end of the inductor L1 is coupled to the cathode of the diode D1. In another embodiment, the first terminal of the inductor L1 is coupled to the first terminal of the switch T1, and the second terminal of the inductor L1, i.e., the first pin Vin, is coupled to the cathode of the diode D1 externally and coupled to the first terminal of the linear device internally. By arranging the inductor L1 in the control chip 60, reasonable power supply voltage can be provided under the condition of meeting the requirement of outputting voltage in a large range, the power consumption of the system is reduced, peripheral devices of the power conversion system are reduced, the volume of the system is reduced, and the integration level of the system is improved.

Fig. 7 shows a schematic diagram of a power supply circuit 70 according to an embodiment of the invention. In this embodiment, the same switching device T2 is multiplexed by the switching circuit and the linear circuit of the power supply circuit 70, so that when the selection control circuit 71 detects that the power supply input voltage Vin is low, the selection control circuit enters a first time period, the switch enable signal EN1 outputs an effective value for enabling the switching circuit, the switch T1 and the rectifier T2 are controlled by the switching signal CT1, the switching device T2 operates in a switching state, the switch T1 and the switching device T2 are alternately turned on, and the inductor L1, the switch T1 and the switching device T2 form a boost circuit for making the power supply voltage VDD higher than the power supply input voltage Vin. The switching signal CT1 may be a square wave signal with alternating positive and negative levels. When the selection control circuit 71 detects that the power supply input voltage Vin is higher, the selection control circuit enters a second time period, the second enable signal EN2 is effectively used for enabling the linear circuit, the control signal CT2 controls the switching device T2 to work in a linear state, the switch T1 is turned off, the inductor L1 is degraded into a wire function, and the power supply voltage VDD is lower than the power supply input voltage Vin by controlling the conduction degree of the linear device T2. CT2 may be the signal provided by linear control circuit 38 in fig. 3. In this way, the supply voltage VDD can always be stabilized around a fixed value in a wide output voltage range. The control driving circuit in the control chip can not only avoid the power supply of higher supply voltage to make the loss lower when the power supply conversion system has high output voltage, improve the efficiency of the power supply conversion system, but also has enough supply voltage to realize the driving when the output voltage is low. Detecting whether the supply input voltage Vin is higher or lower may be performed by detecting the supply voltage VDD, e.g. by comparing the supply voltage VDD with a first threshold signal and a second threshold signal.

Fig. 8 shows a linear circuit embodiment according to an embodiment of the invention. A linear device in the linear circuit adopts a triode and a voltage regulator tube to realize the control of the power supply voltage VDD.

The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. The descriptions related to the effects or advantages in the specification may not be reflected in practical experimental examples due to uncertainty of specific condition parameters or influence of other factors, and the descriptions related to the effects or advantages are not used for limiting the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.

Claims

1. A power supply circuit for a power conversion system, wherein the power supply circuit is configured to supply power to a control driver circuit configured to control a power device of the power conversion system, the power supply circuit obtains a power supply input voltage by coupling to an auxiliary winding of the power conversion system, the power supply circuit comprising:

the switching circuit comprises a switch, and the output voltage of the output end of the switching circuit is adjusted by adjusting the duty ratio of the switch;

the linear circuit comprises a linear device, the output voltage of the output end of the linear circuit is adjusted by adjusting the conduction degree of the linear device, and the output end of the switch circuit and the output end of the linear circuit are combined and provide a power supply voltage for supplying power to the control drive circuit; and

and the selection control circuit receives a voltage detection signal representing the power supply voltage and a reference signal representing the reference voltage, selectively enables the switch circuit or the linear circuit, and controls the duty ratio of the switch and the conduction degree of the linear device in stages according to the voltage detection signal and the reference signal so as to control the power supply voltage to be stabilized near the reference voltage.

2. The power supply circuit of claim 1, wherein the switching circuit comprises a boost circuit, the boost circuit comprises a switch, an inductor and a rectifier, wherein a first terminal of the inductor is coupled to a first terminal of the switch and a first terminal of the rectifier, a second terminal of the inductor is coupled to the auxiliary winding through a diode, a second terminal of the switch is grounded, a second terminal of the rectifier is an output terminal of the switching circuit, when the boost circuit is enabled by the selection control circuit, the switch and the rectifier are alternately turned on, a linear device in the linear circuit is turned off, and when the linear circuit is enabled by the selection control circuit, the boost circuit stops working, and the linear device is turned on.

3. The power supply circuit of claim 1, wherein the selection control circuit comprises:

the voltage detection circuit is used for detecting the power supply voltage and providing a voltage detection signal;

a comparison circuit that compares the voltage detection signal with a threshold signal; and

and a switching control circuit for enabling the switching circuit or the linear circuit based on the comparison result of the comparison circuit.

4. The power supply circuit of claim 3 wherein the selection control circuit further comprises a switch control circuit, the switch control circuit receiving the voltage sense signal and the reference signal and providing a switch control signal, the switch control signal controlling the switch when the switch control circuit enables the switch circuit, the power supply voltage being controlled to stabilize near the reference voltage by controlling a duty cycle of the switch.

5. The power supply circuit of claim 4, wherein the comparison circuit comprises a hysteresis comparison circuit, the threshold signal is the same signal as the reference signal, and the switch control circuit comprises:

an oscillation circuit that provides an oscillation signal; and

and a switching control signal generation circuit that generates a switching control signal based on the oscillation signal and an output signal of the comparison circuit.

6. The power supply circuit of claim 4, wherein the switch control circuit comprises:

a second comparison circuit that compares the voltage detection signal with the reference signal;

an oscillation circuit that provides an oscillation signal; and

and a switching control signal generation circuit that generates a switching control signal based on the comparison result of the second comparison circuit and the oscillation signal.

7. The power supply circuit of claim 4 wherein the selection control circuit further comprises a linearity control circuit, the linearity control circuit receiving the voltage sense signal and the reference signal and providing a linearity control signal, the linearity control signal controlling the linear device when the switching control circuit enables the linear circuit, the linearity control signal controlling the supply voltage to settle near the reference voltage by controlling the degree of turn-on of the linear device.

8. The power supply circuit of claim 7 wherein the linear control circuit comprises: and the first end of the error amplifying circuit receives the voltage detection signal, the second end of the error amplifying circuit receives the reference signal, and the output end of the error amplifying circuit is coupled with the control end of the linear device and used for providing a linear control signal.

9. The power supply circuit of claim 1, wherein the rectifier in the switching circuit and the linear device in the linear circuit are multiplexed with the same switching device, and the switching device is selectively controlled to operate in a switching state or a linear state according to the supply voltage.

10. A power conversion system comprising the power device of any one of claims 1-9, a power supply circuit, and a control drive circuit.

11. The power conversion system of claim 10, used in a power adapter for a PD fast charge protocol.

12. The power conversion system of claim 10, wherein the power device comprises a gallium nitride field effect transistor.

13. A control chip for a power conversion system, having a first pin and a second pin, wherein the first pin is externally used for coupling a first end of an inductor, a second end of the inductor is used for coupling a first capacitor and coupling an auxiliary winding through a diode, and the second pin is used for coupling a second capacitor, the control chip comprising:

the switch circuit comprises a switch and a rectifying tube, wherein the first end of the switch is coupled with the first pin, the second end of the switch is coupled with the first end of the rectifying tube, and the second end of the rectifying tube is coupled with the second pin;

the linear circuit comprises a linear device, wherein a first end of the linear device is coupled with the first pin, and a second end of the linear device is coupled with the second pin;

the selection control circuit controls the enabling switch circuit or the linear circuit based on the voltage on the second pin or the voltage on the first pin and controls the voltage on the second pin to be stabilized near the reference voltage based on the voltage on the second pin; and

and the control driving circuit is provided with a power supply end and a signal output end, wherein the power supply end is coupled with the second pin, and the signal output end is used for driving a power device of the power conversion circuit.

14. The control chip as claimed in claim 13, further comprising a third pin for externally coupling a control terminal of the power device, wherein the signal output terminal of the control driving circuit is coupled to the third pin.

15. A control chip for a power conversion system is provided with a first pin and a second pin, wherein the first pin is externally used for being coupled with a first capacitor and being coupled with an auxiliary winding through a diode, the second pin is used for being coupled with a second capacitor, and the control chip comprises:

the switch circuit comprises an inductor, a switch and a rectifying tube, wherein the first end of the inductor is coupled with the first end of the switch, the second end of the inductor is coupled with a first pin, the second end of the switch is coupled with the first end of the rectifying tube, and the second end of the rectifying tube is coupled with a second pin;

the linear circuit comprises a linear device, wherein a first end of the linear device is coupled with a first pin or a first end of an inductor, and a second end of the linear device is coupled with a second pin;

the selection control circuit controls the enabling switch circuit or the linear circuit based on the voltage of the second pin or the voltage of the first pin, and controls the voltage on the second pin to be stabilized near the reference voltage based on the voltage of the second pin; and