TWI871924B - Power supply device with high efficiency - Google Patents

Abstract

A power supply device with high efficiency includes a bridge rectifier, a first capacitor, a transformer, a first power switch element, a second power switch element, an output stage circuit, a feedback compensation circuit, and a synchronous control circuit. The bridge rectifier generates a rectified voltage according to a first input voltage and a second input voltage. The transformer includes a main coil and a secondary coil. Both the first power switch element and the second power switch element selectively couple the main coil to a ground voltage according to a first driving voltage. The output stage circuit generates an output voltage. The feedback compensation circuit generates a feedback voltage and a capacitive voltage according to the output voltage. The synchronous control circuit monitors the first power switch element and the second power switch element, such that the first power switch element and the second power switch element are synchronized.

Description

High efficiency power supply

The present invention relates to a power supply, and in particular to a power supply with high efficiency.

The power supply is an indispensable component in the field of laptop computers. However, if the overall efficiency of the power supply is insufficient, it will easily cause the overall operating performance of the related laptop to decline. In view of this, it is necessary to propose a new solution to overcome the difficulties faced by previous technologies.

In a preferred embodiment, the present invention provides a high-efficiency power supply, comprising: a bridge rectifier, generating a rectified potential according to a first input potential and a second input potential; a first capacitor, storing the rectified potential; a transformer, comprising a main coil and a secondary coil, wherein the main coil is used to receive the rectified potential, and the secondary coil is used to output an induced potential; a first power switch, selectively coupling the main coil to a ground potential according to a first driving potential; a second power switch, selectively coupling the main coil to a ground potential according to a first driving potential; The first driving potential is used to selectively couple the main coil to the ground potential; an output stage circuit generates an output potential according to the induced potential; a feedback compensation circuit generates a feedback potential and a capacitance potential according to the output potential; and a synchronization control circuit monitors the first power switch and the second power switch, and generates the first driving potential according to the rectified potential, the output potential, the feedback potential, and the capacitance potential, so that the first power switch and the second power switch can be synchronized.

In some embodiments, the bridge rectifier includes: a first diode having an anode and a cathode, wherein the anode of the first diode is coupled to a first input node to receive the first input potential, and the cathode of the first diode is coupled to a first node to output the rectified potential; a second diode having an anode and a cathode, wherein the anode of the second diode is coupled to a second input node to receive the second input potential, and the cathode of the second diode is coupled to the first node; a third diode having an anode and a cathode, wherein the anode of the third diode is coupled to the ground potential, and the cathode of the third diode is coupled to the first input node; and a fourth diode having an anode and a cathode, wherein the anode of the fourth diode is coupled to the ground potential, and the cathode of the fourth diode is coupled to the second input node; wherein the first capacitor has a first end and a second end, the first end of the first capacitor is used to receive and store the rectified potential, and the second end of the first capacitor is coupled to the ground potential.

In some embodiments, the transformer further has a built-in excitation inductor, the main coil has a first end and a second end, the first end of the main coil is coupled to the first node to receive the rectified potential, the second end of the main coil is coupled to a second node, the excitation inductor has a first end and a second end, the first end of the excitation inductor is coupled to the first node, the second end of the excitation inductor is coupled to the second node, the secondary coil has a first end and a second end, the first end of the secondary coil is coupled to a third node to output the induced potential, and the second end of the secondary coil is coupled to a common node.

In some embodiments, the first power switch includes: a first transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the first transistor is used to receive the first driving potential, the first terminal of the first transistor is coupled to the ground potential, and the second terminal of the first transistor is coupled to the second node.

In some embodiments, the second power switch includes: a second transistor having a control end, a first end, and a second end, wherein the control end of the second transistor is used to receive the first driving potential, the first end of the second transistor is coupled to the ground potential, and the second end of the second transistor is coupled to the second node.

In some embodiments, the output stage circuit includes: a fifth diode having an anode and a cathode, wherein the anode of the fifth diode is coupled to the third node to receive the induced potential, and the cathode of the fifth diode is coupled to an output node to output the output potential; and a second capacitor having a first end and a second end, wherein the first end of the second capacitor is coupled to the output node, and the second end of the second capacitor is coupled to the common node.

In some embodiments, the feedback compensation circuit includes: a first resistor having a first end and a second end, wherein the first end of the first resistor is coupled to the output node to receive the output potential, and the second end of the first resistor is coupled to a fourth node; a second resistor having a first end and a second end, wherein the first end of the second resistor is coupled to the fourth node, and the second end of the second resistor is coupled to the common node; a third capacitor having a first end and a second end, wherein the first end of the third capacitor is coupled to a fifth node, and the second end of the third capacitor is coupled to the fourth node; a voltage regulator having an anode, a cathode, and a reference terminal, wherein the anode of the voltage regulator is coupled to the common node, and the voltage regulator The cathode of the voltage regulator is coupled to the fifth node, and the reference terminal of the voltage regulator is coupled to the fourth node; a linear optical coupler, including a light-emitting diode and a bipolar junction transistor, wherein the light-emitting diode has an anode and a cathode, the anode of the light-emitting diode is coupled to the output node, the cathode of the light-emitting diode is coupled to the fifth node, and the bipolar junction transistor has There is a collector and an emitter, the collector of the bipolar junction transistor is used to output the feedback potential, and the emitter of the bipolar junction transistor is coupled to a sixth node; and a fourth capacitor has a first end and a second end, wherein the first end of the fourth capacitor is coupled to the sixth node to output the capacitance potential, and the second end of the fourth capacitor is coupled to the ground potential.

In some embodiments, the synchronous control circuit includes: a divider that divides the rectified potential by the product of the output potential and the capacitor potential to determine a critical potential.

In some embodiments, the synchronous control circuit further includes: a microcontroller, obtaining a first potential difference across the first power switch and a second potential difference across the second power switch, wherein the microcontroller further generates the first driving potential and a second driving potential according to the feedback potential, the first potential difference, the second potential difference, and the critical potential; wherein the first driving potential and the second driving potential have complementary logical levels, and the divider is powered by the second driving potential.

In some embodiments, if the first potential difference and the second potential difference both drop to the critical potential, the microcontroller switches the first driving potential from a low logic level to a high logic level.

100,200: Power supply

110,210: Bridge rectifier

120,220: Transformer

121,221: Main coil

122,222: Secondary coil

130,230: First power switch

140,240: Second power switch

150,250: Output stage circuit

160,260: Feedback compensation circuit

170,270: Synchronous control circuit

262: Voltage regulator

264: Linear optocoupler

272: Divider

274:Microcontroller

C1: First capacitor

C2: Second capacitor

C3: The third capacitor

C4: The fourth capacitor

D1: First diode

D2: Second diode

D3: The third diode

D4: The fourth second pole

D5: The fifth diode

DL: Light Emitting Diode

LM: Magnetizing inductor

M1: first transistor

M2: Second transistor

N1: First node

N2: Second node

N3: The third node

N4: The fourth node

N5: Fifth Node

N6: Node 6

NCM: Common Node

NIN1: first input node

NIN2: Second input node

NOUT: output node

Q1: Bipolar Junction Transistor

R1: First resistor

R2: Second resistor

T1: First time point

T2: Second time point

VF: Feedback potential

VG1: first driving potential

VG2: Second driving potential

VIN1: first input potential

VIN2: Second input potential

VOUT: output voltage

VP: Capacitor potential

VR: Rectification potential

VS: Induction potential

VSS: ground potential

VX: critical potential

△V1: first potential difference

△V2: Second potential difference

Figure 1 is a schematic diagram showing a power supply according to an embodiment of the present invention.

Figure 2 shows a circuit diagram of a power supply according to an embodiment of the present invention.

Figure 3 shows the potential waveforms of the first potential difference and the second potential difference of a conventional power supply.

Figure 4 shows the potential waveforms of the first driving potential, the first potential difference, and the second potential difference of the power supply according to an embodiment of the present invention.

In order to make the purpose, features and advantages of the present invention more clearly understood, the following specifically lists the specific embodiments of the present invention and describes them in detail with the accompanying drawings.

Certain terms are used in the specification and patent application to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and patent application do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criterion for distinction. The words "include" and "including" mentioned throughout the specification and patent application are open terms and should be interpreted as "including but not limited to". The word "substantially" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and achieve the basic technical effect. In addition, the word "coupled" in this specification includes any direct and indirect electrical connection means. Therefore, if the text describes a first device coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device via other devices or connection means.

FIG. 1 is a schematic diagram showing a power supply 100 according to an embodiment of the present invention. For example, the power supply 100 can be applied to a desktop computer, a laptop computer, or an all-in-one computer. As shown in FIG. 1, the power supply 100 includes: a bridge rectifier 110, a first capacitor C1, a transformer 120, a first power switch 130, a second power switch 140, an output stage circuit 150, a feedback compensation circuit 160, and a synchronous control circuit 170. It should be noted that, although not shown in FIG. 1, the power supply 100 may further include other components, such as: a voltage regulator or (and) a negative feedback circuit.

The bridge rectifier 110 can generate a rectified potential VR according to a first input potential VIN1 and a second input potential VIN2, wherein an AC voltage with an arbitrary frequency and an arbitrary amplitude can be formed between the first input potential VIN1 and the second input potential VIN2. For example, the frequency of the AC voltage can be approximately 50 Hz or 60 Hz, and the root mean square value (RMS) of the AC voltage can be approximately between 90 V and 264 V, but is not limited thereto. The first capacitor C1 can store the rectified potential VR. The transformer 120 includes a main coil 121 and a secondary coil 122, wherein the main coil 121 can be located on one side of the transformer 120, and the secondary coil 122 can be located on the other side of the transformer 120. The main coil 121 can be used to receive the rectified potential VR, and in response to the rectified potential VR, the secondary coil 122 can be used to output an induced potential VS. The first power switch 130 can selectively couple the main coil 121 to a ground potential VSS (e.g., 0V) according to a first driving potential VG1. In addition, the second power switch 140 can also selectively couple the main coil 121 to the ground potential VSS according to the first driving potential VG1. That is, the second power switch 140 is coupled in parallel with the first power switch 130, thereby reducing the overall switching loss. For example, if the first driving potential VG1 is a high logic level (i.e., logic "1"), the first power switch 130 and the second power switch 140 can couple the main coil 121 to the ground potential VSS (i.e., the first power switch 130 and the second power switch 140 can each be similar to a short circuit path); conversely, if the first driving potential VG1 is a low logic level (i.e., logic "0"), the first power switch 130 and the second power switch 140 will not couple the main coil 121 to the ground potential VSS (i.e., the first power switch 130 and the second power switch 140 can each be similar to a broken circuit path). The output stage circuit 150 can generate an output potential VOUT according to the induced potential VS. For example, the output potential VOUT may be a DC potential, and its potential level may be between 18V and 20V, but is not limited thereto. The feedback compensation circuit 160 may generate a feedback potential VF and a capacitor potential VP according to the output potential VOUT. The synchronous control circuit 170 is coupled to the first power switch 130 and the second power switch 140 to monitor the operating states of the first power switch 130 and the second power switch 140. In addition, the synchronous control circuit 170 may also generate a first driving potential VG1 according to the rectified potential VR, the output potential VOUT, the feedback potential VF, and the capacitor potential VP, so that the first power switch 130 and the second power switch 140 can be synchronized. Under the design of the present invention, the first power switch 130 and the second power switch 140 will not have non-ideal conditions of inconsistent operation, so the overall efficiency of the power supply 100 can be greatly improved.

The following embodiments will introduce the detailed structure and operation of the power supply 100. It must be understood that these figures and descriptions are only examples and are not intended to limit the scope of the present invention.

FIG. 2 is a circuit diagram of a power supply 200 according to an embodiment of the present invention. In the embodiment of FIG. 2, the power supply 200 has a first input node NIN1, a second input node NIN2, and an output node NOUT, and includes a bridge rectifier 210, a first capacitor C1, a transformer 220, a first power switch 230, a second power switch 240, an output stage circuit 250, a feedback compensation circuit 260, and a synchronous control circuit 270. The first input node NIN1 and the second input node NIN2 of the power supply 200 can receive a first input potential VIN1 and a second input potential VIN2 from an external input power source (not shown), respectively. The output node NOUT of the power supply 200 can be used to output an output potential VOUT to an electronic device (not shown).

The bridge rectifier 210 includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The first diode D1 has an anode and a cathode, wherein the anode of the first diode D1 is coupled to the first input node NIN1, and the cathode of the first diode D1 is coupled to a first node N1 to output a rectified potential VR. The second diode D2 has an anode and a cathode, wherein the anode of the second diode D2 is coupled to the second input node NIN2, and the cathode of the second diode D2 is coupled to the first node N1. The third diode D3 has an anode and a cathode, wherein the anode of the third diode D3 is coupled to a ground potential VSS, and the cathode of the third diode D3 is coupled to the first input node NIN1. The fourth diode D4 has an anode and a cathode, wherein the anode of the fourth diode D4 is coupled to the ground potential VSS, and the cathode of the fourth diode D4 is coupled to the second input node NIN2.

The first capacitor C1 has a first end and a second end, wherein the first end of the first capacitor C1 is used to receive and store the rectified potential VR, and the second end of the first capacitor C1 is coupled to the ground potential VSS.

The transformer 220 includes a main coil 221 and a secondary coil 222, wherein the transformer 220 may further have a built-in excitation inductor LM. The excitation inductor LM may be an inherent component that is produced when the transformer 220 is manufactured, and it is not an external independent component. The main coil 221 and the excitation inductor LM may be located on the same side of the transformer 220 (e.g., the primary side), and the secondary coil 222 may be located on the other side of the transformer 220 (e.g., the secondary side, which may be isolated from the primary side). In detail, the main coil 221 has a first end and a second end, wherein the first end of the main coil 221 is coupled to the first node N1 to receive the rectified potential VR, and the second end of the main coil 221 is coupled to a second node N2. The excitation inductor LM has a first end and a second end, wherein the first end of the excitation inductor LM is coupled to the first node N1, and the second end of the excitation inductor LM is coupled to the second node N2. The secondary coil 222 has a first end and a second end, wherein the first end of the secondary coil 222 is coupled to a third node N3 to output an induced potential VS, and the second end of the secondary coil 222 is coupled to a common node NCM. For example, the common node NCM can provide a common potential, which can be regarded as another ground potential, and can be the same as or different from the aforementioned ground potential VSS.

The first power switch 230 includes a first transistor M1. For example, the first transistor M1 may be an N-type Metal-Oxide-Semiconductor Field-Effect Transistor (NMOSFET). The first transistor M1 has a control terminal (e.g., a gate), a first terminal (e.g., a source), and a second terminal (e.g., a drain), wherein the control terminal of the first transistor M1 is used to receive a first driving potential VG1, the first terminal of the first transistor M1 is coupled to the ground potential VSS, and the second terminal of the first transistor M1 is coupled to the second node N2. In some embodiments, there is a first potential difference △V1 that can cross the first power switch 230, which can be equivalent to the potential difference between the second terminal and the first terminal of the first transistor M1.

The second power switch 240 includes a second transistor M2. For example, the second transistor M2 may be another N-type metal oxide semi-conductor field effect transistor. The second transistor M2 has a control terminal (e.g., a gate), a first terminal (e.g., a source), and a second terminal (e.g., a drain), wherein the control terminal of the second transistor M2 is used to receive the first driving potential VG1, the first terminal of the second transistor M2 is coupled to the ground potential VSS, and the second terminal of the second transistor M2 is coupled to the second node N2. In some embodiments, there is a second potential difference △V2 that can cross the second power switch 240, which can be equivalent to the potential difference between the second terminal and the first terminal of the second transistor M2. In some embodiments, since there may be some parasitic impedance on a conductor coupled to the second node N2, the first potential difference △V1 and the second potential difference △V2 may not be completely equal. In other embodiments, if the parasitic impedance of the conductor is small enough and can be ignored, the first potential difference △V1 and the second potential difference △V2 will be exactly equal to each other.

The output stage circuit 250 includes a fifth diode D5 and a second capacitor C2. The fifth diode D5 has an anode and a cathode, wherein the anode of the fifth diode D5 is coupled to the third node N3 to receive the induced potential VS, and the cathode of the fifth diode D5 is coupled to the output node NOUT. The second capacitor C2 has a first end and a second end, wherein the first end of the second capacitor C2 is coupled to the output node NOUT, and the second end of the second capacitor C2 is coupled to the common node NCM.

In some embodiments, the feedback compensation circuit 260 includes: a voltage regulator 262, a linear optical coupler 264, a third capacitor C3, a fourth capacitor C4, a first resistor R1, and a second resistor R2.

The first resistor R1 has a first end and a second end, wherein the first end of the first resistor R1 is coupled to the output node NOUT to receive the output potential VOUT, and the second end of the first resistor R1 is coupled to a fourth node N4. The second resistor R2 has a first end and a second end, wherein the first end of the second resistor R2 is coupled to the fourth node N4, and the second end of the second resistor R2 is coupled to the common node NCM. The third capacitor C3 has a first end and a second end, wherein the first end of the third capacitor C3 is coupled to a fifth node N5, and the second end of the third capacitor C3 is coupled to the fourth node N4.

In some embodiments, the voltage regulator 262 is implemented by a TL431 electronic component. Specifically, the voltage regulator 262 has an anode, a cathode, and a reference terminal, wherein the anode of the voltage regulator 262 is coupled to the common node NCM, the cathode of the voltage regulator 262 is coupled to the fifth node N5, and the reference terminal of the voltage regulator 262 is coupled to the fourth node N4.

In some embodiments, the linear optical coupler 264 is implemented by a PCX electronic component. In detail, the linear optical coupler 264 includes a light-emitting diode DL and a bipolar junction transistor Q1 (e.g., NPN type). The light-emitting diode DL has an anode and a cathode, wherein the anode of the light-emitting diode DL is coupled to the output node NOUT, and the cathode of the light-emitting diode DL is coupled to the fifth node N5. The bipolar junction transistor Q1 has a collector and an emitter, wherein the collector of the bipolar junction transistor Q1 is used to output a feedback potential VF, and the emitter of the bipolar junction transistor Q1 is coupled to a sixth node N6.

In addition, the fourth capacitor C4 has a first end and a second end, wherein the first end of the fourth capacitor C4 is coupled to the sixth node N6 to output a capacitance potential VP, and the second end of the fourth capacitor C4 is coupled to the ground potential VSS. It should be noted that the capacitance potential VP is associated with the aforementioned feedback potential VF. In some embodiments, the capacitance potential VP can be almost equal to the aforementioned feedback potential VF.

In some embodiments, the synchronous control circuit 270 includes a divider 272 and a microcontroller unit (MCU) 274, which can be coupled to each other.

其中「VX」代表臨界電位VX之位準之對應數值，「VR」代表整流電位VR之位準之對應數值，「VOUT」代表輸出電位VOUT之位準之對應數值，而「VP」代表電容電位VP之位準之對應數值。 The divider 272 can generate a critical potential VX according to the rectified potential VR, the output potential VOUT, and the capacitor potential VP. In detail, the divider 272 can divide the rectified potential VR by the product of the output potential VOUT and the capacitor potential VP to determine the aforementioned critical potential VX. In some embodiments, the divider 272 can operate according to the following equation (1):

Among them, "VX" represents the corresponding value of the level of the critical potential VX, "VR" represents the corresponding value of the level of the rectified potential VR, "VOUT" represents the corresponding value of the level of the output potential VOUT, and "VP" represents the corresponding value of the level of the capacitor potential VP.

For example, if the rectified potential VR is equal to 120V and the output potential VOUT is equal to 20V and the capacitor potential VP is equal to 3V, the critical potential VX will be equal to 2V (i.e., 120÷20÷3=2), but it is not limited to this. It must be understood that the divider 272 only performs pure numerical operations without involving any numerical units.

The microcontroller 274 is coupled to the second node N2 to obtain the first potential difference ΔV1 across the first power switch 230 and the second potential difference ΔV2 across the second power switch 240. In addition, the microcontroller 274 can also obtain the critical potential VX from the divider 272. Then, the microcontroller 274 can generate a first driving potential VG1 and a second driving potential VG2 according to the feedback potential VF, the first potential difference ΔV1, the second potential difference ΔV2, and the critical potential VX. In some embodiments, the first driving potential VG1 and the second driving potential VG2 have complementary logical levels, wherein the divider 272 can be powered by the second driving potential VG2. That is, only when the first driving potential VG1 is a low logic level and the second driving potential VG2 is a high logic level, the divider 272 can operate normally; otherwise, the divider 272 will be disabled.

Figure 3 shows the potential waveforms of the first potential difference △V1 and the second potential difference △V2 of a conventional power supply, where the horizontal axis represents time (s) and the vertical axis represents the potential level (V). As shown in Figure 3, in conventional designs, there is often an operational inconsistency problem between different power switches. However, this asynchronous phenomenon not only causes circuit malfunction and electromagnetic interference (EMI), but also causes a decline in overall efficiency.

FIG. 4 is a potential waveform diagram showing the first driving potential VG1, the first potential difference ΔV1, and the second potential difference ΔV2 of the power supply 200 according to an embodiment of the present invention, wherein the horizontal axis represents time (s) and the vertical axis represents the potential level (V). In the embodiment of FIG. 4, if it is detected that both the first potential difference ΔV1 and the second potential difference ΔV2 drop to the critical potential VX (for example, at a first time point T1 and a second time point T2), the microcontroller 274 will immediately switch the first driving potential VG1 from a low logic level to a high logic level. Therefore, the operations of the first power switch 230 and the second power switch 240 can be almost completely synchronized. In addition, according to actual measurement results, the critical potential VX determined by the divider 272 can be regarded as a better switching condition, which also helps to further improve the overall efficiency of the power supply 200.

The present invention proposes a novel power supply. According to actual measurement results, the power supply with the above-mentioned design can effectively improve the overall efficiency of the power supply, so it is very suitable for application in various types of devices.

It is worth noting that the potential, current, resistance, inductance, capacitance, and other component parameters mentioned above are not limiting conditions of the present invention. Designers can adjust these settings according to different needs. The power supply of the present invention is not limited to the states shown in Figures 1-4. The present invention may include only one or more features of any one or more embodiments of Figures 1-4. In other words, not all features shown in the diagrams must be implemented in the power supply of the present invention at the same time. Although the embodiments of the present invention use metal oxide semi-conductor field effect transistors as an example, the present invention is not limited to this. People in the technical field can use other types of transistors, such as junction field effect transistors, fin field effect transistors, etc., without affecting the effect of the present invention.

In this specification and the scope of the patent application, ordinal numbers, such as "first", "second", "third", etc., have no sequential relationship with each other and are only used to mark and distinguish two different components with the same name.

Although the present invention is disclosed as above with the preferred embodiment, it is not intended to limit the scope of the present invention. Anyone familiar with this technology can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined in the attached patent application.

100: Power supply

110: Bridge rectifier

120: Transformer

121: Main coil

122: Secondary coil

130: First power switch

140: Second power switch

150: Output stage circuit

160: Feedback compensation circuit

170: Synchronous control circuit

C1: First capacitor

VF: Feedback potential

VG1: first driving potential

VIN1: first input potential

VIN2: Second input potential

VOUT: output voltage

VP: Capacitor potential

VR: Rectification potential

VS: Induction potential

VSS: ground potential

Claims (10)

A high-efficiency power supply, comprising: A bridge rectifier, generating a rectified potential according to a first input potential and a second input potential; A first capacitor, storing the rectified potential; A transformer, comprising a main coil and a secondary coil, wherein the main coil is used to receive the rectified potential, and the secondary coil is used to output an induced potential; A first power switch, selectively coupling the main coil to a ground potential according to a first driving potential; A second power switch, selectively coupling the main coil to the ground potential according to the first driving potential; An output stage circuit, generating an output potential according to the induced potential; A feedback compensation circuit generates a feedback potential and a capacitor potential according to the output potential; and a synchronization control circuit monitors the first power switch and the second power switch, and generates the first driving potential according to the rectified potential, the output potential, the feedback potential, and the capacitor potential, so that the first power switch and the second power switch can be synchronized. A power supply as described in claim 1, wherein the bridge rectifier comprises: a first diode having an anode and a cathode, wherein the anode of the first diode is coupled to a first input node to receive the first input potential, and the cathode of the first diode is coupled to a first node to output the rectified potential; a second diode having an anode and a cathode, wherein the anode of the second diode is coupled to a second input node to receive the second input potential, and the cathode of the second diode is coupled to the first node; A third diode having an anode and a cathode, wherein the anode of the third diode is coupled to the ground potential, and the cathode of the third diode is coupled to the first input node; and A fourth diode having an anode and a cathode, wherein the anode of the fourth diode is coupled to the ground potential, and the cathode of the fourth diode is coupled to the second input node; wherein the first capacitor has a first end and a second end, the first end of the first capacitor is used to receive and store the rectified potential, and the second end of the first capacitor is coupled to the ground potential. A power supply as described in claim 2, wherein the transformer further has a built-in excitation inductor, the main coil having a first end and a second end, the first end of the main coil being coupled to the first node to receive the rectified potential, the second end of the main coil being coupled to a second node, the excitation inductor having a first end and a second end, the first end of the excitation inductor being coupled to the first node, the second end of the excitation inductor being coupled to the second node, the secondary coil having a first end and a second end, the first end of the secondary coil being coupled to a third node to output the induced potential, and the second end of the secondary coil being coupled to a common node. A power supply as described in claim 3, wherein the first power switch comprises: A first transistor having a control end, a first end, and a second end, wherein the control end of the first transistor is used to receive the first driving potential, the first end of the first transistor is coupled to the ground potential, and the second end of the first transistor is coupled to the second node. A power supply as described in claim 3, wherein the second power switch comprises: A second transistor having a control end, a first end, and a second end, wherein the control end of the second transistor is used to receive the first driving potential, the first end of the second transistor is coupled to the ground potential, and the second end of the second transistor is coupled to the second node. A power supply as described in claim 3, wherein the output stage circuit comprises: a fifth diode having an anode and a cathode, wherein the anode of the fifth diode is coupled to the third node to receive the induced potential, and the cathode of the fifth diode is coupled to an output node to output the output potential; and a second capacitor having a first end and a second end, wherein the first end of the second capacitor is coupled to the output node, and the second end of the second capacitor is coupled to the common node. A power supply as described in claim 6, wherein the feedback compensation circuit comprises: a first resistor having a first end and a second end, wherein the first end of the first resistor is coupled to the output node to receive the output potential, and the second end of the first resistor is coupled to a fourth node; a second resistor having a first end and a second end, wherein the first end of the second resistor is coupled to the fourth node, and the second end of the second resistor is coupled to the common node; a third capacitor having a first end and a second end, wherein the first end of the third capacitor is coupled to a fifth node, and the second end of the third capacitor is coupled to the fourth node; A voltage regulator having an anode, a cathode, and a reference terminal, wherein the anode of the voltage regulator is coupled to the common node, the cathode of the voltage regulator is coupled to the fifth node, and the reference terminal of the voltage regulator is coupled to the fourth node; A linear optical coupler includes a light-emitting diode and a bipolar junction transistor, wherein the light-emitting diode has an anode and a cathode, the anode of the light-emitting diode is coupled to the output node, the cathode of the light-emitting diode is coupled to the fifth node, the bipolar junction transistor has a collector and an emitter, the collector of the bipolar junction transistor is used to output the feedback potential, and the emitter of the bipolar junction transistor is coupled to a sixth node; and a fourth capacitor, having a first end and a second end, wherein the first end of the fourth capacitor is coupled to the sixth node to output the capacitance potential, and the second end of the fourth capacitor is coupled to the ground potential. A power supply as described in claim 1, wherein the synchronous control circuit includes: A divider that divides the rectified potential by the product of the output potential and the capacitor potential to determine a critical potential. A power supply as described in claim 8, wherein the synchronous control circuit further comprises: A microcontroller, which obtains a first potential difference across the first power switch and a second potential difference across the second power switch, wherein the microcontroller further generates the first driving potential and a second driving potential according to the feedback potential, the first potential difference, the second potential difference, and the critical potential; wherein the first driving potential and the second driving potential have complementary logical levels, and the divider is powered by the second driving potential. A power supply as described in claim 9, wherein if the first potential difference and the second potential difference both drop to the critical potential, the microcontroller switches the first driving potential from a low logic level to a high logic level.

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