阅读说明：本技术 开关电源电路 (Switching power supply circuit ) 是由 侯松林 岳丹金 王凯莉 于 2019-05-21 设计创作，主要内容包括：一种开关电源电路,包括：电压变换模块,适于将其接入的第一电压信号转换为脉冲交流信号并输出,所述电压变换模块包括用于控制所述脉冲交流信号的频率和/或占空比的脉宽调制控制电路和晶体管开关元件；第二整流滤波电路,与所述电压变换模块耦接,适于将所述电压变换模块输出的脉冲交流信号转换为第二电压信号并输出；以及反馈电路,适于接入所述第二整流滤波电路输出的第二电压信号,并向所述电压变换模块输出用于指示所述第二整流滤波电路的输出电压大小的反馈信号；其中,所述电压变换模块还适于根据所述反馈信号调节所述开关电源电路的输出电压,形成了反激准谐振式的电路拓扑结构,实现了开关电源的高频化和小型化。(A switching power supply circuit comprising: the voltage conversion module is suitable for converting a first voltage signal connected into the voltage conversion module into a pulse alternating current signal and outputting the pulse alternating current signal, and comprises a pulse width modulation control circuit and a transistor switching element, wherein the pulse width modulation control circuit is used for controlling the frequency and/or the duty ratio of the pulse alternating current signal; the second rectification filter circuit is coupled with the voltage conversion module and is suitable for converting the pulse alternating current signal output by the voltage conversion module into a second voltage signal and outputting the second voltage signal; the feedback circuit is suitable for being connected with a second voltage signal output by the second rectifying and filtering circuit and outputting a feedback signal for indicating the output voltage of the second rectifying and filtering circuit to the voltage conversion module; the voltage conversion module is also suitable for adjusting the output voltage of the switching power supply circuit according to the feedback signal, a flyback quasi-resonant circuit topology structure is formed, and high frequency and miniaturization of the switching power supply are achieved.)

1. A switching power supply circuit, comprising:

the voltage conversion module is suitable for converting a first voltage signal connected into the voltage conversion module into a pulse alternating current signal and outputting the pulse alternating current signal, and comprises a pulse width modulation control circuit and a transistor switching element, wherein the pulse width modulation control circuit is used for controlling the frequency and/or the duty ratio of the pulse alternating current signal;

the second rectification filter circuit is coupled with the voltage conversion module and is suitable for converting the pulse alternating current signal output by the voltage conversion module into a second voltage signal and outputting the second voltage signal; and

the feedback circuit is suitable for being connected with a second voltage signal output by the second rectifying and filtering circuit and outputting a feedback signal for indicating the output voltage of the second rectifying and filtering circuit to the voltage conversion module;

the voltage conversion module is further suitable for adjusting the output voltage of the switching power supply circuit according to the feedback signal.

2. The switching power supply circuit according to claim 1, wherein the voltage conversion module further comprises a transformer, the transformer comprising a magnetic core, a primary winding and a secondary winding, the primary winding of the transformer being adapted to be coupled to the first voltage signal, the secondary winding of the transformer being coupled to the input of the second rectifying and filtering circuit; the first end of the transistor switch element is coupled with the primary winding of the transformer, and the output end of the pulse width modulation control circuit is coupled with the second end of the transistor switch element so as to control the on and off of the transistor switch element.

3. The switching power supply circuit according to claim 2, wherein said output terminal of said pwm control circuit is adapted to output a pulse signal for controlling the on and off of said transistor switching element, and a maximum frequency of said pulse signal is greater than 150 KHz.

4. The switching power supply circuit according to claim 2 or 3, wherein the output power of the switching power supply circuit is 45W, the inductance of the primary winding of the transformer is 240 μ H, the primary winding of the transformer has 30 turns, and the secondary winding of the transformer has 5 turns; or

The output power of the switching power supply circuit is 65W, the inductance of a primary winding of the transformer is 200 muH, the number of primary windings of the transformer is 24, and the number of secondary windings of the transformer is 4.

5. A switching power supply circuit according to claim 2 or 3, characterized in that the primary winding and the secondary winding of the transformer each comprise a plurality of strands of litz wire connected in parallel.

6. A switching power supply circuit according to claim 1 or 3, wherein the transistor switching element comprises a gallium nitride transistor or a silicon carbide transistor.

7. The switching power supply circuit according to claim 6, wherein said gallium nitride transistor comprises a gallium nitride MOSFET.

8. A switching power supply circuit according to claim 1 or 3, wherein the transistor switching element includes a gallium nitride transistor and a driver chip adapted to drive the gallium nitride transistor.

9. The switching power supply circuit according to claim 3, wherein the transistor switching element includes a silicon transistor and a heat dissipation member.

10. The switching power supply circuit according to claim 2, wherein said pulse width modulation control circuit has a first input terminal coupled to a primary winding of said transformer and a second input terminal coupled to an output terminal of said feedback circuit.

11. The switching power supply circuit according to claim 10, wherein the first input terminal of the pwm control circuit is coupled to a third terminal of the transistor switching element, and the third terminal of the transistor switching element is grounded via an impedance element; or

A first input terminal of the pulse width modulation control circuit is coupled between a first terminal of the transistor switching element and an output terminal of the primary winding of the transformer, and the first terminal of the transistor switching element is coupled with the output terminal of the primary winding of the transformer through the transformer; or

The first input end of the pulse width modulation control circuit is coupled between the input end of the primary winding of the transformer and the input end of the switching power supply circuit, and the input end of the primary winding of the transformer is coupled with the input end of the switching power supply circuit through a mutual inductor.

12. The switching power supply circuit according to claim 1, wherein the first voltage signal is a first dc signal, the switching power supply circuit further comprises a first rectifying and filtering circuit, the first rectifying and filtering circuit is adapted to convert an ac signal received by the first rectifying and filtering circuit into a first dc signal and output the first dc signal, and the voltage converting module is adapted to receive the first dc signal output by the first rectifying and filtering circuit.

13. The switching power supply circuit according to claim 1, wherein the second voltage signal is a second direct current signal.

14. The switching power supply circuit according to claim 12, further comprising: an input end of the EMI circuit is suitable for being connected into an alternating current power grid, and an output end of the EMI circuit is coupled with an input end of the first rectifying and filtering circuit.

15. The switching power supply circuit according to claim 1, wherein the feedback circuit comprises a photo coupler or an isolation chip.

16. The switching power supply circuit according to claim 1, wherein an output power of the switching power supply circuit is less than 150W.

Technical Field

The invention relates to the technical field of electronic circuits, in particular to a switching power supply circuit.

Background

The high frequency of the switching power supply is an important development direction of modern switching power supplies, because the high frequency can miniaturize the switching power supply, and further improve the power density of the switching power supply, so that the switching power supply enters a wider application field. Especially, the application in the high and new technology field accelerates the development of the switch power supply. Every year, switching power supplies are rapidly advancing towards being light, small, thin, low-noise, highly reliable and anti-interference with an increasing rate of more than two digits.

The traditional power supply scheme based on the silicon material MOSFET cannot meet the practical requirements due to the defects of low working frequency, large volume, low power density, low efficiency and the like.

Disclosure of Invention

In order to improve the operating frequency of the switching power supply and to achieve miniaturization of the switching power supply, an embodiment of the present invention provides a switching power supply circuit, including: the voltage conversion module is suitable for converting a first voltage signal connected into the voltage conversion module into a pulse alternating current signal and outputting the pulse alternating current signal, and comprises a pulse width modulation control circuit and a transistor switching element, wherein the pulse width modulation control circuit is used for controlling the frequency and/or the duty ratio of the pulse alternating current signal; the second rectification filter circuit is coupled with the voltage conversion module and is suitable for converting the pulse alternating current signal output by the voltage conversion module into a second voltage signal and outputting the second voltage signal; the feedback circuit is suitable for being connected with a second voltage signal output by the second rectifying and filtering circuit and outputting a feedback signal for indicating the output voltage of the second rectifying and filtering circuit to the voltage conversion module; the voltage conversion module is further suitable for adjusting the output voltage of the switching power supply circuit according to the feedback signal.

Optionally, the voltage conversion module further comprises a transformer, the transformer comprising a magnetic core, a primary winding and a secondary winding, the primary winding of the transformer being adapted to be coupled to the first voltage signal, the secondary winding of the transformer being coupled to the input of the second rectifying and filtering circuit; the first end of the transistor switch element is coupled with the primary winding of the transformer, and the output end of the pulse width modulation control circuit is coupled with the second end of the transistor switch element so as to control the on and off of the transistor switch element.

Optionally, the output terminal of the pwm control circuit is adapted to output a pulse signal, the pulse signal is used to control the transistor switching element to be turned on and off, and a maximum frequency of the pulse signal is greater than 150 KHz.

Optionally, the output power of the switching power supply circuit is 45W, the inductance of the primary winding of the transformer is 240 μ H, the number of primary windings is 30, and the number of secondary windings is 5; or the output power of the switching power supply circuit is 65W, the inductance of the primary winding of the transformer is 200 muH, the primary winding is 24 turns, and the secondary winding is 4 turns.

Optionally, the primary winding and the secondary winding of the transformer each comprise a plurality of strands of litz wire connected in parallel.

Optionally, the transistor switching element comprises a gallium nitride transistor or a silicon carbide transistor.

Optionally, the gallium nitride transistor comprises a gallium nitride MOSFET.

Optionally, the transistor switching element comprises a gallium nitride transistor and a driving chip, and the driving chip is adapted to drive the gallium nitride transistor.

Optionally, the transistor switching element comprises a silicon transistor and a heat dissipation member.

Optionally, the pwm control circuit has a first input coupled to the primary winding of the transformer and a second input coupled to the output of the feedback circuit.

Optionally, the first input terminal of the pwm control circuit is coupled to a third terminal of the transistor switch, and the third terminal of the transistor switch is grounded through an impedance element; or the first input end of the pulse width modulation control circuit is coupled between the first end of the transistor switching element and the output end of the primary winding of the transformer, and the first end of the transistor switching element is coupled with the output end of the primary winding of the transformer through the mutual inductor; or the first input end of the pulse width modulation control circuit is coupled between the input end of the primary winding of the transformer and the input end of the switching power supply circuit, and the input end of the primary winding of the transformer is coupled with the input end of the switching power supply circuit through a mutual inductor.

Optionally, the first voltage signal is a first dc signal, the switching power supply circuit further includes a first rectifying and filtering circuit, the first rectifying and filtering circuit is adapted to convert an ac signal received by the first rectifying and filtering circuit into a first dc signal and output the first dc signal, and the voltage conversion module is adapted to receive the first dc signal output by the first rectifying and filtering circuit.

Optionally, the second voltage signal is a second direct current signal.

Optionally, the switching power supply circuit further includes: an input end of the EMI circuit is suitable for being connected into an alternating current power grid, and an output end of the EMI circuit is coupled with an input end of the first rectifying and filtering circuit.

Optionally, the feedback circuit comprises a photo coupler or an isolation chip.

Optionally, the output power of the switching power supply circuit is less than 150W.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:

compared with a traditional silicon transistor, the switching element such as gallium nitride or silicon carbide has the advantages of high working frequency, strong high temperature resistance, low on-state resistance, small switching loss and the like, and particularly, the volume of the gallium nitride switching element is much smaller under the same current capability. The switching power supply circuit of the embodiment of the invention adopts the pulse width modulation control circuit and the transistor switching element such as gallium nitride or silicon carbide and the like which is suitable for working under the high-frequency condition to control the frequency and/or the duty ratio of the pulse alternating current signal output by the voltage conversion module, fully utilizes the performance advantages that the switching element can keep high performance and high efficiency under the high-frequency condition, and is beneficial to realizing the high frequency and miniaturization of the switching power supply. The switching power supply circuit of the embodiment of the invention further comprises a feedback circuit, wherein the feedback circuit can output a feedback signal for indicating the output voltage of the second rectifying and filtering circuit to the voltage conversion module, so that the voltage conversion module can adjust the output voltage of the switching power supply circuit according to the feedback signal, and a flyback Quasi-Resonance (QR) mode power supply circuit topological structure is formed.

Further, the voltage conversion module further includes a transformer, the first terminal of the transistor switching element is coupled to the primary winding of the transformer, the transistor switching element may include a gallium nitride transistor or a silicon carbide transistor, and the like, because the gallium nitride transistor or the silicon carbide transistor has higher electron mobility and higher switching response speed, the operating frequency of the switching power supply circuit according to the embodiment of the present invention is greatly increased compared to the conventional power supply circuit using a silicon transistor as the switching element, the inductance of the primary winding of the transformer is accordingly reduced, the small-sized transformer can meet the requirement of the power supply circuit, and is beneficial to reducing the core size and the number of turns of the coil of the transformer, thereby further promoting the miniaturization of the switching power supply.

Further, the primary winding and the secondary winding of the transformer respectively comprise a plurality of strands of litz wires connected in parallel, which is beneficial to reducing the heat increase of the transformer caused by the increase of the working frequency of the switching power supply circuit.

Further, the pulse width modulation control circuit includes: a first input terminal and a second input terminal, the first input terminal coupled to the primary winding of the transformer, the pulse width modulation control circuit operable to detect a current through the primary winding of the transformer; the second input terminal is coupled to the output terminal of the feedback circuit, so that the pwm control circuit can also be used to detect the output voltage of the switching power supply circuit. Through the two feedback mechanisms, the pulse width modulation control circuit can maintain the stability of the output voltage of the switching power supply circuit by adjusting the frequency and/or the duty ratio of the pulse signal output by the pulse width modulation control circuit no matter the change of the current in the primary winding of the transformer and/or the change of the output voltage of the switching power supply circuit caused by the change of the voltage of a power grid or the change of the load.

Drawings

Fig. 1 is a block diagram of a switching power supply circuit 10 according to an embodiment of the present invention;

fig. 2 is a block diagram of the PWM control circuit 123 of the switching power supply circuit 10 according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a switching power supply circuit 20 according to another embodiment of the present invention.

Detailed Description

An embodiment of the present invention is provided in a switching power supply circuit 10, and is described in detail below with reference to the accompanying drawings.

Referring to fig. 1, fig. 1 is a block diagram of a switching power supply circuit 10 according to an embodiment of the present invention.

In some embodiments, the switching power supply circuit 10 includes: a voltage conversion module 12, a second rectifying and filtering circuit 13 and a feedback circuit 14. The voltage conversion module 12 is adapted to convert the first voltage signal received by the voltage conversion module 12 into a Pulse ac signal and output the Pulse ac signal, and the voltage conversion module 12 includes a transistor switching element 122 and a Pulse Width Modulation (PWM) control circuit 123 for controlling the frequency and/or duty ratio of the Pulse ac signal. The second rectifying and filtering circuit 13 is coupled to the voltage converting module 12 and adapted to convert the pulse ac signal output by the voltage converting module 12 into a second voltage signal and output the second voltage signal. The feedback circuit 14 is adapted to receive the second voltage signal output by the second rectifying and filtering circuit 13 and output an output voltage U indicating the second rectifying and filtering circuit 13 to the voltage converting module 12₀A magnitude feedback signal; wherein the voltage conversion module 12 is further adapted to adjust the output voltage U of the switching power supply circuit 10 according to the feedback signal connected thereto₀。

In some embodiments, the switching power supply circuit 10 further includes a first rectifying and filtering circuit 11, and the first rectifying and filtering circuit 11 is adapted to convert an ac signal received by the first rectifying and filtering circuit into the first voltage signal and output the first voltage signal. For example, the input terminal of the first rectifying and filtering circuit 11 may be coupled to an ac power grid, and the first voltage signal may be a first dc signal.

In some embodiments, the voltage conversion module 12 further includes a transformer 121, the transformer 121 may include a magnetic core, a primary winding and a secondary winding, the primary winding of the transformer 121 is adapted to receive the first voltage signal, for example, a first dc signal output by the first rectifying and filtering circuit 11, and the secondary winding of the transformer 121 is coupled to the input terminal of the second rectifying and filtering circuit 13; a first terminal of the transistor switching element 122 is coupled to the primary winding of the transformer 121. An output terminal of the PWM control circuit 123 is coupled to the second terminal of the transistor switch element 122 to control the transistor switch element 122 to be turned on and off.

In some embodiments, the transistor switching element 122 may be connected in series with the primary winding of the transformer 121.

In some embodiments, the output terminal of the PWM control circuit 123 is adapted to output a pulse signal, the pulse signal is used to control the transistor switch element 122 to turn on and off, and the maximum frequency of the pulse signal is greater than 150KHz, so that the maximum frequency of the pulsed ac signal output by the voltage conversion module 12 is greater than 150 KHz.

In some embodiments, the transformer 121 may include a primary winding and one or more secondary windings. Since the PWM control circuit 123 outputs a high-frequency pulse signal, the transistor switching element 122 is controlled by the high-frequency pulse signal to turn on and off at a higher frequency, so that the operating frequency of the transformer 121 is increased, the inductance of the primary winding of the transformer 121 is reduced, and the transformer 121 with a small size can meet the requirements of a power circuit, which is beneficial to reducing the size of the magnetic core and the number of turns of the coil of the transformer 121, and further promotes the miniaturization of the switching power supply.

In some embodiments, the output power of the switching power supply circuit 10 is 45W, the inductance of the primary winding of the transformer 121 is 240 μ H, the primary winding has 30 turns, and the secondary winding has 5 turns.

In some embodiments, the output power of the switching power supply circuit 10 is 65W, the inductance of the primary winding of the transformer 121 is 200 μ H, the primary winding has 24 turns, and the secondary winding has 4 turns.

In some embodiments, the primary winding and each secondary winding of the transformer 121 may respectively include a plurality of strands of litz wire connected in parallel to reduce an increase in heat of the transformer 121 due to an increase in the operating frequency of the switching power supply circuit 10.

Since the PWM control circuit 123 outputs a high frequency pulse signal, the transistor switching element 122 needs to have a high response speed, and in some embodiments, the transistor switching element 122 may include a gallium nitride (GaN) transistor or a silicon carbide (SiC) transistor. In particular, the gallium nitride transistor may be a gallium nitride power transistor, such as a gallium nitride MOSFET, which may be an enhancement mode MOSFET, including an enhancement mode P-channel MOSFET or an enhancement mode N-channel MOSFET. The gallium nitride transistor may employ a GaN-on-Si process suitable for Si fabrication flows. The silicon carbide transistor may be a silicon carbide MOSFET.

In some embodiments, the transistor switching element 122 may include a gallium nitride transistor and a driving chip for driving the gallium nitride transistor, and the gallium nitride transistor and the driving chip may be integrated together.

In some embodiments, the transistor switching element 122 may also include a silicon transistor, but since the silicon transistor has low carrier mobility and slow switching response speed, under the control of the high-frequency pulse signal output by the PWM control circuit 123, high heat may be generated, and thus heat generation of the silicon transistor may be reduced by providing a heat dissipation component.

In addition, in the conventional low-frequency switching power supply circuit based on the Si transistor, the volume and the weight of the energy storage element are large, resulting in a reduction in the power density of the switching power supply. Compared with the traditional Si transistor, the transistor such as gallium nitride or silicon carbide has higher working frequency, smaller switching loss and high switching speed, and is applied to a switching power supply circuit, so that the size and the weight of an energy storage element are reduced, the miniaturization of the switching power supply is realized, and the power density of the switching power supply is improved.

Here, the high-frequency performance of the switching power supply circuit according to the embodiment of the present invention is described by taking a gallium nitride transistor or a silicon carbide transistor as an example, but the embodiment of the present invention is not limited thereto. In other embodiments, the transistor switch element 122 may comprise other types of transistors that need to maintain high performance and high efficiency at higher operating frequencies, where the "higher operating frequency" may be 10²On the order of KHz.

In some embodiments, the PWM control circuit 123 may further have a first input coupled to the primary winding of the transformer and a second input coupled to the output of the feedback circuit. The first input terminal may be coupled to the primary winding of the transformer 121 in various ways, so that the first input terminal of the PWM control circuit 123 can detect the current passing through the primary winding of the transformer 121.

In some embodiments, the first input terminal of the PWM control circuit 123 may be coupled to the third terminal of the transistor switch 122, and the third terminal of the transistor switch 122 is grounded through an impedance element, so that the first input terminal may be used to detect the voltage of the third terminal of the transistor switch 122, and thus the current passing through the primary winding of the transformer 121. A second input terminal of the PWM control circuit 123 is coupled to the output terminal of the feedback circuit 14, and can be used for detecting the output voltage U of the switching power supply circuit 10₀。

In some embodiments, the voltage conversion module 12 adjusts the frequency or duty ratio of the pulsed ac signal output by the voltage conversion module according to the feedback signal received by the voltage conversion module, so as to adjust the output voltage U of the switching power supply circuit 10₀。

With combined reference to FIG. 2, FIG. 2 is the bookThe PWM control circuit 123 according to an embodiment of the present invention is a block diagram. In some embodiments, the PWM control circuit 123 may include: the pulse width modulation circuit comprises a first comparing module 1231, a second comparing module 1232, a pulse frequency adjusting module 1233 and a pulse duty ratio adjusting module 1234, wherein the pulse frequency adjusting module 1233 is adapted to adjust the frequency f of the pulse signal output by the PWM control circuit 123, and the pulse duty ratio adjusting module 1234 is adapted to adjust the duty ratio D of the pulse signal output by the PWM control circuit 123. A first input end a of the first comparing module 1231 may serve as a first input end of the PWM control circuit 123 to connect the voltage of the third end of the transistor switching element 122, and a second input end b of the first comparing module 1231 is adapted to connect a first reference voltage U1_RefAn output terminal of the first comparing module 1231 is coupled to an input terminal of the pulse frequency adjusting module 1233. The first input c of the second comparing module 1232, which serves as the second input of the PWM control circuit 123, is coupled to the output of the feedback circuit 14, and the second input d of the second comparing module 1232 is adapted to be connected to a second reference voltage U2_RefAn output of the second comparing module 1232 is coupled to an input of the pulse duty cycle adjusting module 1234.

In some embodiments, the pulse frequency adjustment module 1233 and the pulse duty cycle adjustment module 1234 may be two separate modules. In other embodiments, the pulse frequency adjustment module 1233 and the pulse duty cycle adjustment module 1234 may also be integrated, i.e., the adjustment of the pulse frequency and duty cycle is achieved by a single module.

When the network voltage changes or the output load changes, the output voltage U of the switching power supply circuit 10 is caused₀And the current in the primary winding of the transformer 121, respectively, the PWM control circuit 123 may maintain the output voltage U of the switching power supply circuit 10 by adjusting the frequency f and/or the duty ratio D of the pulse signal output therefrom₀The stability of (2).

In some embodiments, the second rectifying and filtering circuit 13 may include a unidirectional rectifying circuit or a bidirectional rectifying circuit. For example, the second rectifying and smoothing circuit 13 may include a rectifying diode connected in series with the secondary winding of the transformer 121, the rectifying diode is turned off when the PWM control circuit 123 controls the transistor switching element 122 to be turned on, the transformer 121 stores energy, and the rectifying diode is turned on when the PWM control circuit 123 controls the transistor switching element 122 to be turned off, the transformer 121 releases energy to a load.

In some embodiments, the feedback circuit 14 may include an optical coupler, and the optical coupler may include a light emitting diode and a photo transistor, wherein an anode of the light emitting diode is coupled to the output terminal of the second rectifying and filtering circuit 13, and a collector of the photo transistor is coupled to the second input terminal of the PWM control circuit 123.

In other embodiments, the feedback circuit 14 may comprise an isolated chip.

Since the feedback circuit 14 of the embodiment of the present invention outputs the output voltage U for indicating the switching power supply circuit 10 to the PWM control circuit 123₀A feedback signal of magnitude, the PWM control circuit 123 can output the output voltage U of the switching power supply circuit 10 according to the feedback signal₀And correspondingly adjusting to maintain the voltage-stabilized output, thereby forming a power supply circuit topological structure of a flyback Quasi-Resonance (QR) mode.

In some embodiments, the switching power supply circuit further comprises an EMI (Electro-magnetic interference) circuit 15, an input of the EMI circuit 15 is adapted to be connected to an ac power grid, and an output of the EMI circuit 15 is coupled to an input of the first rectifying and filtering circuit 11. The EMI circuit 15 may be configured to suppress electromagnetic noise and noise signals input to the switching power supply circuit 10, prevent interference from being generated in the switching power supply circuit 10, and prevent interference of high-frequency noise generated by the switching power supply circuit 10 to a power grid, thereby playing an isolation role.

In some embodiments, the maximum frequency of the pulsed ac signal output by the voltage conversion module 12 is greater than 150 KHz. Specifically, the maximum frequency range of the pulse ac signal output by the voltage conversion module 12 may be 150KHz to 300 KHz.

In some embodiments, the output power of the switching power supply circuit 10 may be less than 150W. Specifically, the output power of the switching power supply circuit 10 may be less than 100W, for example, the output power of the switching power supply circuit 10 may be 45W or 65W.

Referring to fig. 3, fig. 3 is a schematic structural diagram of a switching power supply circuit 20 according to another embodiment of the present invention.

In some embodiments, the switching power supply circuit 20 includes: the circuit comprises an EMI circuit 25, a first rectifying and filtering circuit 21, a voltage conversion module 22, a second rectifying and filtering circuit 23 and a feedback circuit 24. The first rectifying and filtering circuit 21 is adapted to convert the ac signal received by the first rectifying and filtering circuit 21 into a first dc signal and output the first dc signal, the voltage converting module 22 is adapted to convert the first dc signal output by the first rectifying and filtering circuit 21 into a pulse ac signal and output the pulse ac signal, and the voltage converting module 22 includes a transformer 221, a gallium nitride switching element 222 for controlling the frequency and/or duty ratio of the pulse ac signal output by the voltage converting module 22, and a PWM control circuit 223. An input end of the second rectifying and filtering circuit 23 is coupled to an output end of the voltage conversion module 22, and is adapted to convert the pulse ac signal output by the voltage conversion module 22 into a second dc signal and output the second dc signal, where an output voltage of the second rectifying and filtering circuit 23 is an output voltage V of the switching power supply circuit 20_out. The feedback circuit 24 is adapted to receive the second dc signal output by the second rectifying and filtering circuit 23 and output an indication (i.e. reflect) of the output voltage V of the second rectifying and filtering circuit 23 to the voltage converting module 22_outA magnitude feedback signal; wherein the voltage conversion module 22 is further adapted to adjust the output voltage V of the switching power supply circuit 20 according to the feedback signal received by the voltage conversion module_out。

In some embodiments, the EMI circuit 25 may include an inductor 251 and a first filter capacitor 252.

In some embodiments, the first rectifying and filtering circuit 21 may include a first rectifying circuit 211 and a first filtering circuit 212, wherein the first rectifying circuit 211 may be a full bridge rectifying circuit, and the first filtering circuit 212 may include a second filtering capacitor.

In some embodiments, the gallium nitride switching element 222 may include a gallium nitride transistor 2221, and the gallium nitride transistor 2221 may be a gallium nitride MOSFET. A third terminal of the gan transistor 2221 (e.g., a source of an NMOSFET) may be grounded via a resistor 26, a first terminal of the gan transistor 2221 (e.g., a drain of the NMOSFET) may be coupled to the 1 terminal of the primary winding of the transformer 221, and a second terminal of the gan transistor 2221 (e.g., a gate of the NMOSFET) may be coupled to an output terminal of the PWM control circuit 223.

In other embodiments, the gan switching element 222 may be a gan chip, the gan chip 222 may include a gan transistor 2221 and a peripheral circuit 2222, and the gan transistor 2221 may be a gan MOSFET. A third terminal (e.g., a source of an NMOSFET) and a second terminal (e.g., a gate of an NMOSFET) of the gallium nitride transistor 2221 may be coupled to the peripheral circuit 2222, and a first terminal (e.g., a drain of an NMOSFET) of the gallium nitride transistor 2221 may be coupled to a 1 terminal of the primary winding of the transformer 221 through one or more pins of the gallium nitride chip 222 (e.g., pins 5, 6, 7, and 8 of the gallium nitride chip 222 in fig. 3).

It should be noted that, a structure of the peripheral circuit 2222 is shown in a dashed box in fig. 3, but the embodiment of the present invention is not limited thereto, and the peripheral circuit 2222 may have various other circuit structures.

In some embodiments, the PWM control circuit 223 may include a control chip having a plurality of pins, the 5-pin of the control chip is coupled to the third terminal of the gan transistor 2221 (e.g., the source of the NMOSFET) and one terminal of the resistor 26, and the other terminal of the resistor 26 is grounded; the 3 pin of the control chip is coupled to the output terminal of the feedback circuit 24, the 7 pin of the control chip is adapted to output a pulse width modulated pulse signal, and the 7 pin of the control chip is coupled to the second terminal (e.g., a gate of an NMOSFET) of the gallium nitride transistor 2221 through the 2 pin of the gallium nitride chip 222.

Wherein, the pin 5 of the control chip is coupled to the third terminal of the gan transistor 2221, and can be used to detect the current passing through the primary winding of the transformer 221, as described in the foregoing embodiments, the first input terminal (i.e., pin 5) of the PWM control circuit 223 can be coupled to the primary winding of the transformer 221 in various ways, only one of which is shown in fig. 3.

In other embodiments, the first input terminal (i.e., pin 5) of the PWM control circuit 223 may be electrically connected between the first terminal (e.g., drain of NMOSFET) of the gan transistor 2221 and the output terminal (i.e., pin 1) of the primary winding of the transformer 221 (not shown), and a transformer (not shown) is connected in series between the output terminal (i.e., pin 1) of the primary winding of the transformer 221 and the first terminal of the gan transistor 2221.

In other embodiments, the first input terminal (i.e., pin 5) of the PWM control circuit 223 may be electrically connected between the output terminal of the first rectifying and filtering circuit 21 and the input terminal (i.e., pin 2) of the primary winding of the transformer 221 (not shown), and a transformer (not shown) is also connected between the output terminal of the first rectifying and filtering circuit 21 and the input terminal (i.e., pin 2) of the primary winding of the transformer 221 in series.

In some embodiments, the second rectifying and filtering circuit 23 may include a second rectifying circuit 231 and a second filtering circuit 232, the second rectifying circuit 231 may be a unidirectional rectifying circuit, and the second dc signal output by the second rectifying and filtering circuit 23 may be a pulsed dc signal.

In some embodiments, the feedback circuit 24 may include an opto-coupler including a light emitting diode and a phototransistor, a pin 1 of the light emitting diode is coupled to the output terminal of the second rectifying and filtering circuit 23, and a pin 4 of the phototransistor is coupled to a pin 3 of the PMW control circuit 223.

In some embodiments, the switching power supply circuit 20 may further include a thermistor 27 for preventing a surge, and the switching power supply circuit 20 may further include a fuse 28.

The functions and the circuit operating principles of the modules of the switching power supply circuit 20 in this embodiment may refer to the foregoing embodiments, and are not described herein again. The switching power supply circuit 20 of the present embodiment employs a gallium nitride transistor as a switching element, and can achieve both high frequency and miniaturization of the switching power supply circuit 20.

In summary, the switching element such as gan or sic has advantages of high operating frequency, high temperature resistance, low on-resistance and small switching loss compared to the conventional silicon transistor, and particularly, the gan switching element has a much smaller volume under the same current capability. The switching power supply circuit of the embodiment of the invention adopts the pulse width modulation control circuit and the transistor switching element such as gallium nitride or silicon carbide and the like which is suitable for working under the high-frequency condition to control the frequency and/or the duty ratio of the pulse alternating current signal output by the voltage conversion module, fully utilizes the performance advantages that the switching element can keep high performance and high efficiency under the high-frequency condition, and is beneficial to realizing the high frequency and miniaturization of the switching power supply. The switching power supply circuit of the embodiment of the invention further comprises a feedback circuit, wherein the feedback circuit can output a feedback signal for indicating the output voltage of the second rectifying and filtering circuit to the voltage conversion module, so that the voltage conversion module can adjust the output voltage of the switching power supply circuit according to the feedback signal, and a flyback Quasi-Resonance (QR) mode power supply circuit topological structure is formed.

Further, the voltage conversion module further includes a transformer, the first terminal of the transistor switching element is coupled to the primary winding of the transformer, the transistor switching element may include a gallium nitride transistor or a silicon carbide transistor, and the like, because the gallium nitride transistor or the silicon carbide transistor has higher electron mobility and higher switching response speed, the operating frequency of the switching power supply circuit according to the embodiment of the present invention is greatly increased compared to the conventional power supply circuit using a silicon transistor as the switching element, the inductance of the primary winding of the transformer is accordingly reduced, the small-sized transformer can meet the requirement of the power supply circuit, and is beneficial to reducing the core size and the number of turns of the coil of the transformer, thereby further promoting the miniaturization of the switching power supply.

Further, the primary winding and the secondary winding of the transformer respectively comprise a plurality of strands of litz wires connected in parallel, which is beneficial to reducing the heat increase of the transformer caused by the increase of the working frequency of the switching power supply circuit.

Further, the pulse width modulation control circuit includes: a first input terminal and a second input terminal, the first input terminal coupled to the primary winding of the transformer, the pulse width modulation control circuit operable to detect a current through the primary winding of the transformer; the second input terminal is coupled to the output terminal of the feedback circuit, so that the pwm control circuit can also be used to detect the output voltage of the switching power supply circuit. Through the two feedback mechanisms, the pulse width modulation control circuit can maintain the stability of the output voltage of the switching power supply circuit by adjusting the frequency and/or the duty ratio of the pulse signal output by the pulse width modulation control circuit no matter the change of the current in the primary winding of the transformer and/or the change of the output voltage of the switching power supply circuit caused by the change of the voltage of a power grid or the change of the load.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.