TWI891201B - Power supply device with high efficiency - Google Patents

Abstract

A power supply device with high efficiency includes a bridge rectifier, a transformer, a power switch element, an output stage circuit, and a control circuit. The transformer includes a main coil and a secondary coil. The power switch element selectively couples the main coil to a ground voltage. The control circuit controls the power switch element according to a communication voltage. The control circuit operates in a first mode, a second mode, or a third mode. If the control circuit operates in the first mode, the power switch element can provide a small driving current. If the control circuit operates in the second mode, the power switch element can provide a median driving current. If the control circuit operates in the third mode, the power switch element can provide a large driving current.

Description

High-efficiency power supply

The present invention relates to a power supply, and more particularly to a power supply with high efficiency.

Power supplies are essential components in laptop computers. However, if they operate inefficiently, they can easily degrade the overall performance of the laptop. Therefore, a new solution is necessary to overcome the challenges faced by existing technologies.

In a preferred embodiment, the present invention provides a high-efficiency power supply, comprising: a bridge rectifier, generating a rectified potential based on a first input potential and a second input 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 power switch, selectively coupling the main coil to a ground potential; an output stage circuit, generating an output potential based on the induced potential; and and a control circuit that controls the power switch according to a communication potential, wherein the control circuit operates in a first mode, a second mode, or a third mode; wherein if the control circuit operates in the first mode, the power switch provides a small drive current; wherein if the control circuit operates in the second mode, the power switch provides a medium drive current; wherein if the control circuit operates in the third mode, the power switch provides a large drive current.

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.

In some embodiments, the transformer further includes a built-in excitation inductor. The primary coil has a first end and a second end. The first end of the primary coil is coupled to the first node to receive the rectified potential, and the second end of the primary 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, and 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 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 coupled to an operating node, 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; wherein the power switch further includes a built-in parasitic capacitor, the parasitic capacitor having a first terminal and a second terminal, the first terminal of the parasitic capacitor being coupled to the operating node, and the second terminal of the parasitic capacitor being coupled to the ground potential.

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 an output capacitor having a first terminal and a second terminal, wherein the first terminal of the output capacitor is coupled to the output node, and the second terminal of the output capacitor is coupled to the common node.

In some embodiments, the control circuit includes: a microcontroller configured to switch between the first mode, the second mode, and the third mode based on the communication potential; wherein in the first mode, the microcontroller outputs a first control potential to a control node; wherein in the second mode, the microcontroller outputs the first control potential and a second control potential to the control node; wherein in the third mode, the microcontroller outputs the first control potential, the second control potential, and a third control potential to the control node.

In some embodiments, the control circuit further includes: a sixth diode having an anode and a cathode, wherein the anode of the sixth diode is coupled to the operating node, and the cathode of the sixth diode is coupled to the control node; and a first resistor having a first terminal and a second terminal, wherein the first terminal of the first resistor is coupled to the control node, and the second terminal of the first resistor is coupled to the operating node.

In some embodiments, the control circuit further includes: a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is coupled to a fourth node, the first terminal of the second transistor is coupled to a fifth node, and the second terminal of the second transistor is coupled to the operating node; and a second resistor having a first terminal and a second terminal, wherein the first terminal of the second resistor is coupled to the fifth node, and the second terminal of the second resistor is coupled to the ground potential.

In some embodiments, in the third mode, if each of the first control potential, the second control potential, and the third control potential has a low logic level, the microcontroller further outputs a fourth control potential having a high logic level to the fourth node.

In some embodiments, the fourth control potential is further transmitted to an embedded controller at a system end, and the communication potential is generated by the embedded controller.

100,200: Power supply

110,210: Bridge rectifier

120,220: Transformer

121,221: Main Loop

122,222: Secondary coil

130,230: Power switch

140,240: Output stage circuit

150,250: Control circuit

255: Microcontroller

290: System side

292: Main circuit board

294:Embedded Controller

CO: output capacitor

CP: Parasitic Capacitor

D1: First diode

D2: Second diode

D3: The third diode

D4: Fourth Diode

D5: Fifth Diode

D6: Sixth Diode

I1: Smaller driving current

I2: Medium drive current

I3: Larger drive current

LM: Magnetizing Inductor

M1: First transistor

M2: Second transistor

MD1: First Mode

MD2: Second Mode

MD3: The third mode

N1: First node

N2: Second Node

N3: Third Node

N4: Fourth Node

N5: Fifth Node

NC: Control Node

NCM: Common Node

NE: Operation Node

NIN1: First input node

NIN2: Second input node

NOUT: output node

R1: First resistor

R2: Second resistor

VC1: First control voltage

VC2: Second control voltage

VC3: Third control voltage

VC4: Fourth control voltage

VIN1: First input potential

VIN2: Second input potential

VOUT: output voltage

VR: Rectification potential

VS: Induction Potential

VSS: Ground potential

VT: Communication potential

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

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

Figure 3 shows the signal waveforms of the control circuit of the power supply according to one embodiment of the present invention when operating in the first mode.

Figure 4 shows the signal waveforms of the control circuit of the power supply according to one embodiment of the present invention when operating in the second mode.

Figure 5 shows the signal waveforms of the control circuit of the power supply according to one embodiment of the present invention when operating in the third mode.

To make the purpose, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are given below, along with accompanying drawings for detailed description.

Certain terms are used throughout this specification and patent application to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different terms to refer to the same component. This specification and patent application do not distinguish components based on differences in name, but rather on differences in their functionality. The words "including" and "comprising" used throughout this specification and patent application are open-ended and should be interpreted as meaning "including, but not limited to." The word "substantially" means that within an acceptable range of error, a person skilled in the art can solve the technical problem and achieve the basic technical effect. Furthermore, the term "coupled" in this specification includes any direct and indirect electrical connection. Therefore, if a first device is described as being coupled to a second device, it means that the first device may be directly electrically connected to the second device, or indirectly electrically connected to the second device via other devices or connection means.

FIG1 is a schematic diagram of a power supply 100 according to one embodiment of the present invention. For example, the power supply 100 can be used in a desktop computer, a laptop computer, or an all-in-one computer. As shown in FIG1 , the power supply 100 includes a bridge rectifier 110, a transformer 120, a power switch 130, an output stage circuit 140, and a control circuit 150. It should be noted that, although not shown in FIG1 , the power supply 100 may also include other components, such as a voltage regulator and/or a negative feedback circuit.

The bridge rectifier 110 generates a rectified potential VR based on a first input potential VIN1 and a second input potential VIN2. An AC voltage having any frequency and amplitude can be generated 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 (RMS) value of the AC voltage can be approximately between 90 V and 264 V, but is not limited thereto. The transformer 120 includes a main coil 121 and a secondary coil 122. The main coil 121 can be located on one side of the transformer 120, while the secondary coil 122 can be located on the opposite side of the transformer 120. The main winding 121 is configured to receive a rectified potential VR. In response to the rectified potential VR, the secondary winding 122 is configured to output an induced potential VS. The power switch 130 can selectively couple the main winding 121 to a ground potential VSS (e.g., 0V). For example, if the power switch 130 couples the main winding 121 to the ground potential VSS, the power switch 130 can be considered a short-circuited path. Conversely, if the power switch 130 does not couple the main winding 121 to the ground potential VSS, the power switch 130 can be considered an open-circuited path. The output stage circuit 140 can generate an output potential VOUT based on the induced potential VS. For example, the output potential VOUT may be a DC potential whose potential level may be between 18V and 22V, but is not limited thereto. The control circuit 150 may control the power switch 130 according to a communication potential VT, wherein the control circuit 150 may operate in one of a first mode MD1, a second mode MD2, or a third mode MD3. For example, the communication potential VT may come from a system end (not shown). If the control circuit 150 operates in the first mode MD1, the power switch 130 may provide a relatively small drive current I1. If the control circuit 150 operates in the second mode MD2, the power switch 130 may provide a medium drive current I2 (i.e., I2>I1). If the control circuit 150 operates in the third mode MD3, the power switch 130 can provide a larger drive current I3 (i.e., I3 > I2). It should be understood that the terms "smaller," "medium," and "larger" in this specification are defined based on the average values of the corresponding drive currents. With the design of the present invention, the power supply 100 can appropriately adjust the current-driving capability of the power switch 130, thereby significantly improving its operating efficiency. According to actual measurement results, the overall power consumption of the power supply 100 can also be effectively reduced.

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 for illustrative purposes only and are not intended to limit the scope of the present invention.

FIG2 shows a circuit diagram of a power supply 200 according to an embodiment of the present invention. In the embodiment of FIG2 , 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 transformer 220, a power switch 230, an output stage circuit 240, and a control circuit 250. 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, respectively, from an external input power source (not shown). The output node NOUT of the power supply 200 can be used to output an output potential VOUT to a system terminal 290. For example, the system end 290 can be considered as an external device that is not part of the power supply 200.

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 the 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. The anode of the third diode D3 is coupled to a ground potential VSS, while 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. The anode of the fourth diode D4 is coupled to the ground potential VSS, while the cathode of the fourth diode D4 is coupled to the second input node NIN2.

The transformer 220 includes a main coil 221 and a secondary coil 222, wherein the transformer 220 may further include a built-in excitation inductor LM. The excitation inductor LM may be an inherent component generated during the manufacture of the transformer 220 and is not an external independent component. The main coil 221 and the excitation inductor LM may both be located on the same side of the transformer 220 (e.g., the primary side), while the secondary coil 222 may be located on the opposite side of the transformer 220 (e.g., the secondary side, which may be isolated from the primary side). Specifically, 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 magnetizing inductor LM has a first terminal and a second terminal. The first terminal of the magnetizing inductor LM is coupled to the first node N1, while the second terminal of the magnetizing inductor LM is coupled to the second node N2. The secondary coil 222 has a first terminal and a second terminal. The first terminal of the secondary coil 222 is coupled to a third node N3 to output an induced potential VS, while the second terminal 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 considered another ground potential and can be the same as or different from the aforementioned ground potential VSS.

The power switch 230 includes a first transistor M1. For example, the first transistor M1 can 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). The control terminal of the first transistor M1 is coupled to an operating node NE, the first terminal of the first transistor M1 is coupled to ground VSS, and the second terminal of the first transistor M1 is coupled to a second node N2. Furthermore, the power switch 230 may further include a built-in parasitic capacitor CP. The parasitic capacitor CP has a first terminal and a second terminal. The first terminal of the parasitic capacitor CP is coupled to the operating node NE, and the second terminal of the parasitic capacitor CP is coupled to ground VSS. It must be understood that the total parasitic capacitance between the control terminal and the first terminal of the first transistor M1 can be simulated as the aforementioned parasitic capacitor CP, which is not an external independent component.

The output stage circuit 240 includes a fifth diode D5 and an output capacitor CO. The fifth diode D5 has an anode and a cathode. The anode of the fifth diode D5 is coupled to the third node N3 to receive the induced potential VS, while the cathode of the fifth diode D5 is coupled to the output node NOUT. The output capacitor CO has a first terminal and a second terminal. The first terminal of the output capacitor CO is coupled to the output node NOUT, while the second terminal of the output capacitor CO is coupled to the common node NCM.

In some embodiments, the control circuit 250 includes a microcontroller unit 255, a second transistor M2, a sixth diode D6, a first resistor R1, and a second resistor R2. For example, the second transistor M2 can be another N-type metal oxide semiconductor field effect transistor.

The microcontroller 255 can switch between a first mode MD1, a second mode MD2, and a third mode MD3 based on a communication voltage VT. Specifically, in the first mode MD1, the microcontroller 255 can output only a first control voltage VC1 to a control node NC. In the second mode MD2, the microcontroller 255 can simultaneously output the first control voltage VC1 and a second control voltage VC2 to the control node NC. In addition, in the third mode MD3, the microcontroller 255 can simultaneously output the first control voltage VC1, the second control voltage VC2, and a third control voltage VC3 to the control node NC.

The sixth diode D6 has an anode and a cathode, wherein the anode of the sixth diode D6 is coupled to the operating node NE, and the cathode of the sixth diode D6 is coupled to the control node NC. The first resistor R1 has a first terminal and a second terminal, wherein the first terminal of the first resistor R1 is coupled to the control node NC, and the second terminal of the first resistor R1 is coupled to the operating node NE.

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). The control terminal of the second transistor M2 is coupled to a fourth node N4, the first terminal of the second transistor M2 is coupled to a fifth node N5, and the second terminal of the second transistor M2 is coupled to the operating node NE. The second resistor R2 has a first terminal and a second terminal. The first terminal of the second resistor R2 is coupled to the fifth node N5, and the second terminal of the second resistor R2 is coupled to the ground potential VSS.

The system side 290 includes a main circuit board 292 and an embedded controller (EC) 294. Generally speaking, the output voltage VOUT of the power supply 200 provides power to the main circuit board 292 of the system side 290, while the embedded controller 294 of the system side 290 generates and outputs a communication voltage VT to the microcontroller 255 of the power supply 200 based on various driving requirements.

Figure 3 shows signal waveforms when the control circuit 250 of the power supply 200 according to an embodiment of the present invention operates in the first mode MD1. The horizontal axis represents time (s) and the vertical axis represents voltage level (V). For example, the first mode MD1 can serve as a power saving mode for the power supply 200. In the first mode MD1, the microcontroller 255 may only output the first control potential VC1 to the control node NC. The first control potential VC1 can be considered a driving clock potential. On the other hand, the second control potential VC2 and the third control potential VC3 are not generated. Because the power switch 230 is driven only by the first control potential VC1, only a relatively small driving current I1 flows through the first transistor M1 of the power switch 230. When the first control voltage VC1 has a high logic level, the parasitic capacitor CP of the power switch 230 can be charged to a lower voltage level. When the first control voltage VC1 has a low logic level, the charge stored in the parasitic capacitor CP of the power switch 230 can be discharged through the sixth diode D6.

Figure 4 shows a signal waveform diagram of the control circuit 250 of the power supply 200 according to an embodiment of the present invention when operating in the second mode MD2, wherein the horizontal axis represents time (s) and the vertical axis represents the potential level (V). For example, the second mode MD2 can be used as a normal mode of the power supply 200. In the second mode MD2, the microcontroller 255 can simultaneously output the first control potential VC1 and the second control potential VC2 to the control node NC, wherein the first control potential VC1 and the second control potential VC2 can have roughly the same waveform. On the other hand, the third control potential VC3 is not generated. Because the power switch 230 is driven by the first control potential VC1 and the second control potential VC2 at the same time, a medium drive current I2 will flow through the first transistor M1 of the power switch 230. When both the first control potential VC1 and the second control potential VC2 are at a high logic level, the parasitic capacitor CP of the power switch 230 can be charged to a medium voltage level. When both the first control potential VC1 and the second control potential VC2 are at a low logic level, the charge stored in the parasitic capacitor CP of the power switch 230 can be discharged via the sixth diode D6.

FIG5 shows signal waveforms of the control circuit 250 of the power supply 200 according to one embodiment of the present invention operating in the third mode MD3, where the horizontal axis represents time (s) and the vertical axis represents potential level (V). For example, the third mode MD3 can serve as a severe dynamic load mode for the power supply 200. In the third mode MD3, the microcontroller 255 can simultaneously output the first control potential VC1, the second control potential VC2, and the third control potential VC3 to the control node NC. The first control potential VC1, the second control potential VC2, and the third control potential VC3 can have substantially the same waveform. Because the power switch 230 is driven simultaneously by the first control potential VC1, the second control potential VC2, and the third control potential VC3, a large drive current I3 flows through the first transistor M1 of the power switch 230. When the first control potential VC1, the second control potential VC2, and the third control potential VC3 are each at a high logic level, the parasitic capacitor CP of the power switch 230 can be charged to a relatively high voltage level.

In the third mode MD3, because the parasitic capacitor CP may store a significant amount of charge, the control circuit 250 may utilize a rapid discharge mechanism in addition to the sixth diode D6. In some embodiments, if the first control potential VC1, the second control potential VC2, and the third control potential VC3 are each at a low logic level, the microcontroller 255 may output a fourth control potential VC4 at a high logic level to the fourth node N4. In this case, the second transistor M2 turns on, allowing the charge stored in the parasitic capacitor CP to be discharged to ground VSS in a very short time via the second transistor M2 and the second resistor R2. For example, the fourth control potential VC4 may have a complementary logical level to the first control potential VC1, but the present invention is not limited thereto.

In other embodiments, the aforementioned fourth control potential VC4 may be further transmitted to the embedded controller 294 of the system end 290. Therefore, the embedded controller 294 of the system end 290 can monitor the instantaneous state of the fourth control potential VC4 in real time, thereby ensuring its accuracy and reducing the probability of malfunction of the power switch 230.

This invention proposes a novel power supply. Based on actual measurement results, this power supply design effectively improves overall operating efficiency and reduces corresponding power consumption, making it suitable for use in a wide variety of devices.

It is important to note that the voltage, current, resistance, inductance, capacitance, and other component parameters described above are not limiting conditions of the present invention. Designers may adjust these settings according to different needs. The power supply of the present invention is not limited to the states illustrated in Figures 1-5. The present invention may include only one or more features of any one or more of the embodiments in Figures 1-5. In other words, not all illustrated features must be implemented simultaneously in the power supply of the present invention. Although the embodiments of the present invention use metal oxide semiconductor field effect transistors as an example, the present invention is not limited to this. Those skilled in the art may use other types of transistors, such as junction field effect transistors or fin field effect transistors, without affecting the effectiveness of the present invention.

In this specification and the scope of the patent application, ordinal numbers, such as "first," "second," "third," etc., do not have a sequential relationship with each other and are only used to distinguish two different components with the same name.

Although the present invention is disclosed above with reference to preferred embodiments, these are not intended to limit the scope of the present invention. Anyone skilled in the art may make modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of the attached patent application.

100: Power supply 110: Bridge rectifier 120: Transformer 121: Main coil 122: Secondary coil 130: Power switch 140: Output stage circuit 150: Control circuit I1: Small drive current I2: Medium drive current I3: Large drive current MD1: First mode MD2: Second mode MD3: Third mode VIN1: First input voltage VIN2: Second input voltage VOUT: Output voltage VR: Rectified voltage VS: Sense voltage VSS: Ground voltage VT: Transmission voltage

Claims (7)

A high-efficiency power supply comprises: A bridge rectifier generating a rectified potential based on a first input potential and a second input potential; A transformer comprising a main coil and a secondary coil, wherein the main coil is configured to receive the rectified potential and the secondary coil is configured to output an induced potential; A power switch selectively coupling the main coil to a ground potential; An output stage circuit generating an output potential based on the induced potential; and A control circuit controlling the power switch based on a communication potential, wherein the control circuit operates in a first mode, a second mode, or a third mode; If the control circuit operates in the first mode, the power switch provides a smaller drive current; If the control circuit operates in the second mode, the power switch provides a medium drive current. If the control circuit operates in the third mode, the power switch provides a larger drive current. 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; The transformer further includes 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, and 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, and 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. The 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 coupled to an operating node, 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. The power switch further includes a built-in parasitic capacitor, the parasitic capacitor having a first terminal and a second terminal, the first terminal of the parasitic capacitor being coupled to the operating node, and the second terminal of the parasitic capacitor being coupled to the ground potential. The power supply of claim 1, 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 an output capacitor having a first terminal and a second terminal, wherein the first terminal of the output capacitor is coupled to the output node, and the second terminal of the output capacitor is coupled to the common node. The power supply of claim 1, wherein the control circuit comprises: a microcontroller configured to switch between the first mode, the second mode, and the third mode based on the communication potential; wherein, in the first mode, the microcontroller outputs a first control potential to a control node; wherein, in the second mode, the microcontroller outputs the first control potential and a second control potential to the control node; wherein, in the third mode, the microcontroller outputs the first control potential, the second control potential, and a third control potential to the control node. The power supply of claim 3, wherein the control circuit further comprises: a sixth diode having an anode and a cathode, wherein the anode of the sixth diode is coupled to the operating node, and the cathode of the sixth diode is coupled to the control node; and a first resistor having a first terminal and a second terminal, wherein the first terminal of the first resistor is coupled to the control node, and the second terminal of the first resistor is coupled to the operating node. The power supply of claim 3, wherein the control circuit further comprises: a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is coupled to a fourth node, the first terminal of the second transistor is coupled to a fifth node, and the second terminal of the second transistor is coupled to the operating node; and a second resistor having a first terminal and a second terminal, wherein the first terminal of the second resistor is coupled to the fifth node, and the second terminal of the second resistor is coupled to the ground potential. A power supply as described in claim 5, wherein in the third mode, if each of the first control potential, the second control potential, and the third control potential has a low logic level, the microcontroller further outputs a fourth control potential having a high logic level to the fourth node. The power supply as described in claim 6, wherein the fourth control potential is further transmitted to an embedded controller at a system end, and the communication potential is generated by the embedded controller.