TWI838224B - Power supply device with high output stability - Google Patents

Abstract

A power supply device with high output stability includes a bridge rectifier, a transformer, a first sense resistor, a power switch element, an output stage circuit, and an MCU (Microcontroller Unit). The transformer includes a main coil and a secondary coil. A magnetizing inductor is built in the transformer. The first sense resistor is coupled in series with the magnetizing inductor. An inductive current flows through the magnetizing inductor and the first sense resistor. The MCU detects a voltage difference of the first sense resistor, so as to calculate a responsive slope of the inductive current. If the MCU determines that the responsive slope of the inductive current is abnormal, the MCU will generate an alert voltage.

Description

High output stability power supply

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

The power supply is an indispensable component in the field of laptop computers. However, if the output stability 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 power supply with high output stability, comprising: a bridge rectifier, generating a rectified potential according to a first input potential and a second input potential; a transformer, comprising a main coil and a secondary coil, wherein the transformer further has a built-in excitation inductor, the main coil is used to receive the rectified potential, and the secondary coil is used to output an induced potential; a first sensing resistor, wherein the first sensing resistor is coupled in series with the excitation inductor, and an inductor current flows through the excitation inductor. A magnetic inductor and the first sensing resistor; a power switch selectively coupling the first sensing resistor to a ground potential according to a clock potential; an output stage circuit generating an output potential according to the sensing potential; and a microcontroller generating the clock potential, wherein the microcontroller further detects a potential difference of the first sensing resistor to calculate a response slope of the inductor current; wherein if the microcontroller determines that the response slope of the inductor current is abnormal, the microcontroller will further generate a warning potential.

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, The cathode of the second diode is coupled to the first node; a third diode has 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 has 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 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 a third node, the secondary coil has a first end and a second end, the first end of the secondary coil is coupled to a fourth node to output the induced potential, the second end of the secondary coil is coupled to a common node, the first sensing resistor has a first end and a second end, the first end of the first sensing resistor is coupled to the third node, and the second end of the first sensing resistor is coupled to the second node.

In some embodiments, the power switch includes: 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 clock potential, the first end of the first transistor is coupled to a fifth node, and the second end of the first transistor is coupled to the second node.

In some embodiments, the power supply further includes: a second sensing resistor having a first end and a second end, wherein the first end of the second sensing resistor is coupled to the fifth node, and the second end of the second sensing resistor is coupled to the ground potential; wherein the microcontroller further receives a detection potential from the fifth node.

In some embodiments, the output stage circuit includes: a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is used to receive an inverted clock potential, the first terminal of the second transistor is coupled to an output node to output the output potential, and the second terminal of the second transistor is coupled to the fourth node to receive the induced potential; an output capacitor having a first terminal and a second terminal, wherein the output capacitor The first end is coupled to the output node, and the second end of the output capacitor is coupled to a sixth node; and a third sensing resistor having a first end and a second end, wherein the first end of the third sensing resistor is coupled to the sixth node, and the second end of the third sensing resistor is coupled to the common node; wherein the microcontroller further generates the inverted clock potential according to the clock potential; wherein the microcontroller further receives a feedback potential from the sixth node.

In some embodiments, if the microcontroller determines that the detection potential drops to 0 for the first time at a specific time point, the microcontroller is ready to continuously monitor the response slope of the inductor current.

In some embodiments, after the specific time point, when the clock potential has a high logic level, the microcontroller calculates a sampling slope of the inductor current according to the potential difference of the first sensing resistor.

In some embodiments, after the specific time point, when the clock potential has a low logic level, the microcontroller compares the response slope of the inductor current with an inverse of the sampling slope within a plurality of detection time intervals, and if the response slope of the inductor current and the inverse of the sampling slope are not equal, the microcontroller determines that the response slope of the inductor current has been abnormal.

In some embodiments, if the feedback potential is higher than or equal to a critical potential, the microcontroller will further shorten the length of each of the detection time intervals.

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:Microcontroller

500: Mobile device

510: Main circuit board

520:Embedded Controller

530: Display

540: Warning window

CO: output capacitor

CP: Parasitic capacitor

D1: First diode

D2: Second diode

D3: The third diode

D4: The fourth second pole

D5: The fifth diode

IL: Inductor current

IOUT: output current

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

RS1: First sensing resistor

RS2: Second sensing resistor

RS3: The third sensing resistor

SR: Response slope

SS: Sampling slope

T1, T2, TM, TN: detection time interval

TE: Test time point

TS: specific time point

VA: pulse potential

VB: reverse phase pulse potential

VD: Detection potential

VF: Feedback potential

VIN1: first input potential

VIN2: Second input potential

VL: warning potential

VOUT: output voltage

VR: Rectification potential

VS: Induction potential

VSS: ground potential

VTH: critical potential

ΔV: 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 signal waveform of the power supply according to an embodiment of the present invention.

Figure 4 shows the signal waveform of the power supply according to an embodiment of the present invention.

Figure 5 is a schematic diagram showing a mobile device according to an embodiment of the present invention.

Figure 6 is a three-dimensional diagram showing a mobile device according to an embodiment of the present invention.

Figure 7 shows a signal waveform diagram of a 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 transformer 120, a first sensing resistor RS1, a power switch 130, an output stage circuit 140, and a microcontroller unit (MCU) 150. 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 any frequency and any 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 about 50Hz or 60Hz, and the root mean square value (RMS) of the AC voltage can be between 90V and 264V, but is not limited thereto. The transformer 120 includes a main coil 121 and an auxiliary coil 122, wherein the transformer 120 can further have a built-in excitation inductor LM. The main coil 121 and the magnetizing inductor LM can be located on the same side of the transformer 120, and the secondary coil 122 can be located on the opposite 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 a sensed potential VS. The first sensing resistor RS1 is coupled in series with the magnetizing inductor LM, wherein an inductor current IL can flow through the magnetizing inductor LM and the first sensing resistor RS1. The power switch 130 can selectively couple the first sensing resistor RS1 to a ground potential VSS (e.g., 0V) according to a clock potential VA. For example, if the clock potential VA is a high logic level (i.e., logic "1"), the power switch 130 can couple the first sensing resistor RS1 to the ground potential VSS (i.e., the power switch 130 can be similar to a short circuit path); conversely, if the clock potential VA is a low logic level (i.e., logic "0"), the power switch 130 will not couple the first sensing resistor RS1 to the ground potential VSS (i.e., the power switch 130 can be similar to a break path). The output stage circuit 140 can generate an output potential VOUT according to the sense potential VS. For example, the output potential VOUT can be a DC potential, and its potential level can be between 18V and 20V, but it is not limited thereto. The microcontroller 150 can be used to generate a clock potential VA. In addition, the microcontroller 150 can further detect a potential difference ΔV of the first sensing resistor RS1 to calculate a response slope SR of the inductor current IL. If the microcontroller 150 determines that the response slope SR of the inductor current IL is abnormal, the microcontroller 150 can further generate a warning potential VL. Under the design of the present invention, the user can immediately discover the abnormal state of the power supply 100 based on the warning potential VL, which will effectively prevent the output potential VOUT of the power supply 100 from oscillating or fluctuating. Therefore, the power supply 100 of the present invention will greatly improve its own output stability.

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 shows 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 transformer 220, a first sensing resistor RS1, a second sensing resistor RS2, a power switch 230, an output stage circuit 240, and a microcontroller 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 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 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 generated when the transformer 220 is manufactured, and 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), while 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 a third node N3. 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 fourth node N4 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 be regarded as another ground potential, which can be the same as or different from the aforementioned ground potential VSS.

The first sensing resistor RS1 has a first end and a second end, wherein the first end of the first sensing resistor RS1 is coupled to the third node N3, and the second end of the first sensing resistor RS1 is coupled to the second node N2. The first sensing resistor RS1 may have a relatively small resistance value. For example, the resistance value of the first sensing resistor RS1 may be less than or equal to 0.5Ω. In some embodiments, an inductor current IL may flow through the excitation inductor LM and the first sensing resistor RS1, so that a potential difference ΔV may be formed between the first end and the second end of the first sensing resistor RS1, which can also be regarded as the potential difference ΔV obtained by subtracting the potential at the third node N3 from the potential at the second node N2.

The 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 clock potential VA, the first terminal of the first transistor M1 is coupled to a fifth node N5, and the second terminal of the first transistor M1 is coupled to the second node N2.

The second sensing resistor RS2 has a first end and a second end, wherein the first end of the second sensing resistor RS2 is coupled to the fifth node N5, and the second end of the second sensing resistor RS2 is coupled to the ground potential VSS. The second sensing resistor RS2 may have a very small resistance value. For example, the resistance value of the second sensing resistor RS2 may be less than or equal to 1 mΩ, so it can almost be regarded as a short circuit path. In some embodiments, the aforementioned inductor current IL may flow through the second sensing resistor RS2, so that a detection potential VD can be established at the fifth node N5.

The output stage circuit 240 includes a second transistor M2, an output capacitor CO, and a third sensing resistor RS3. For example, the second transistor M2 may be an 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 an inverted clock potential VB, the first terminal of the second transistor M2 is coupled to the output node NOUT, and the second terminal of the second transistor M2 is coupled to the fourth node N4 to receive the sensed potential VS. In some embodiments, the second transistor M2 may further have a built-in parasitic capacitor CP. In detail, the parasitic capacitor CP has a first end and a second end, wherein the first end of the parasitic capacitor CP is coupled to the fourth node N4, and the second end of the parasitic capacitor CP is coupled to the output node NOUT. It must be understood that the total parasitic capacitance (Parasitic Capacitance) between the first end and the second end of the second transistor M2 can be simulated as the aforementioned parasitic capacitor CP, which is not an external independent component.

The output capacitor CO has a first end and a second end, wherein the first end of the output capacitor CO is coupled to the output node NOUT, and the second end of the output capacitor CO is coupled to a sixth node N6. The third sensing resistor RS3 has a first end and a second end, wherein the first end of the third sensing resistor RS3 is coupled to the sixth node N6, and the second end of the third sensing resistor RS3 is coupled to the common node NCM. The third sensing resistor RS3 may have a relatively small resistance value. For example, the resistance value of the third sensing resistor RS3 may be less than or equal to 1Ω. In some embodiments, an output current IOUT may flow through the output capacitor CO and the third sensing resistor RS3, so that a feedback potential VF may be established at the sixth node N6.

The microcontroller 250 can generate a clock potential VA. For example, the clock potential VA can be maintained at a fixed potential when the power supply 200 is just initialized, and can provide a periodic clock waveform after the power supply 200 enters the normal use stage. The microcontroller 250 can also generate an inverted clock potential VB based on the clock potential VA, wherein the inverted clock potential VB can have the same operating frequency and complementary logic level as the clock potential VA. In addition, the microcontroller 250 can also detect and receive the potential difference ΔV of the first sensing resistor RS1, the detection potential VD at the fifth node N5, and the feedback potential VF at the sixth node N6. It must be understood that according to Ohm's law, the inductor current IL of the excitation inductor LM is proportional to the potential difference ΔV of the first sensing resistor RS1. Therefore, the microcontroller 250 can obtain various characteristics of the inductor current IL by analyzing the potential difference ΔV, such as a current value or a current slope (Current Slope), but it is not limited to this.

FIG. 3 shows a signal waveform diagram of the power supply 200 according to an embodiment of the present invention, wherein the horizontal axis represents time and the vertical axis represents potential level. Please refer to FIG. 2 and FIG. 3 together. As shown in FIG. 3, if the microcontroller 250 determines that the detection potential VD drops to 0 for the first time at a specific time point TS, it means that the first transistor M1 is disabled for the first time, and the second transistor M2 is enabled for the first time, so that the parasitic capacitor CP of the second transistor M2 is fully charged. Because the fully charged parasitic capacitor CP may resonate abnormally with the excitation inductor LM, the microcontroller 250 is ready to continuously monitor the response slope of the inductor current IL to see if there is any abnormality at the specific time point TS. In some embodiments, the abnormal response slope of the inductor current IL may occur after the first transistor M1 is disabled for the second time, that is, after a test time point TE.

FIG. 4 is a signal waveform diagram of the power supply 200 according to an embodiment of the present invention, wherein the horizontal axis represents time and the vertical axis represents potential level or current value. Please refer to FIG. 2 and FIG. 4 together. It should be noted that the waveform of the inductor current IL in FIG. 4 appears after the aforementioned specific time point TS. As shown in FIG. 4, when the clock potential VA has a high logic level, the microcontroller 250 calculates a sampling slope SS of the inductor current IL according to the potential difference ΔV of the first sensing resistor RS1. Next, when the clock potential VA has a low logic level, the microcontroller 250 calculates a response slope SR of the inductor current IL according to the potential difference ΔV of the first sensing resistor RS1 in a plurality of detection time intervals T1, T2, ..., TN, and then compares the response slope SR of the inductor current IL with a negative number of the aforementioned sampling slope SS. For example, the aforementioned "N" value can be any positive integer greater than or equal to 2, and each of the aforementioned detection time intervals T1, T2, ..., TN can be between 1μs and 3μs. If the response slope SR of the inductor current IL and the inverse of the sampling slope SS are not equal, the microcontroller 250 will determine that the response slope SR of the inductor current IL has become abnormal, and the microcontroller 250 will generate a warning voltage VL.

For example, when the clock pulse potential VA has a high logic level, the microcontroller 250 calculates that the sampling slope SS of the inductor current IL is equal to 2. Ideally, when the clock pulse potential VA has a low logic level, the response slope SR of the inductor current IL should be equal to -2 (i.e., the inverse of 2). However, if the response slope SR of the inductor current IL is detected to be equal to -0.5 within the detection time interval TN, the microcontroller 250 will determine that the response slope SR of the inductor current IL has been abnormal, and it will immediately output the warning level VL.

FIG. 5 is a schematic diagram showing a mobile device 500 according to an embodiment of the present invention. For example, the mobile device 500 may be a notebook computer or a tablet computer. In the embodiment of FIG. 5, the mobile device 500 includes a mother board (MB) 510 and an embedded controller (EC) 520 thereon. The mother board 510 may receive an output potential VOUT from the power supply 200, and the embedded controller 520 may receive a warning potential VL from the power supply 200.

FIG. 6 is a three-dimensional diagram of a mobile device 500 according to an embodiment of the present invention. In the embodiment of FIG. 6, the mobile device 500 further includes a display 530, which can be controlled by an embedded controller 520. When the embedded controller 520 receives the warning voltage VL, the embedded controller 520 can display a warning window 540 on the display 530 to notify the user that an abnormality has occurred in the power supply 200. At this time, the user can temporarily remove the external input power of the power supply 200 and then restart the power supply 200. Since the parasitic capacitor CP of the second transistor M2 can be completely discharged, the aforementioned reset action can easily solve the problem of abnormal resonance between the parasitic capacitor CP and the excitation inductor LM.

FIG. 7 is a signal waveform diagram of the power supply 200 according to an embodiment of the present invention, wherein the horizontal axis represents time and the vertical axis represents current value. Please refer to FIG. 2 and FIG. 7 together. In the embodiment of FIG. 7, if the feedback potential VF is detected to be higher than or equal to a critical potential VTH, the microcontroller 250 can further shorten the length of each of the plurality of detection time intervals T1, T2, ..., TM. For example, the aforementioned "M" value can be any positive integer greater than or equal to the aforementioned "N" value, and each of the aforementioned detection time intervals T1, T2, ..., TM can be between 0.5μs and 1.5μs. According to actual measurement results, more intensive detection operations of the microcontroller 250 help improve its overall detection accuracy. In some embodiments, the critical potential VTH may correspond to 70% of the maximum value of the output current IOUT of the power supply 200, but is not limited thereto.

The present invention proposes a novel power supply. According to actual measurement results, the power supply with the above design can significantly improve the overall output stability, 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 1-7. The present invention may include only one or more features of any one or more embodiments of Figures 1-7. In other words, not all the features shown in the diagrams need to 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: Power switch

140: Output stage circuit

150: Microcontroller

IL: Inductor current

LM: Magnetizing inductor

RS1: First sensing resistor

SR: Response slope

VA: pulse potential

VIN1: first input potential

VIN2: Second input potential

VL: warning potential

VOUT: output voltage

VR: Rectification potential

VS: Induction potential

VSS: ground potential

△V: potential difference

Claims (10)

A power supply with high output stability, comprising: a bridge rectifier, generating a rectified potential according to a first input potential and a second input potential; a transformer, comprising a main coil and a secondary coil, wherein the transformer further has a built-in excitation inductor, the main coil is used to receive the rectified potential, and the secondary coil is used to output an induced potential; a first sensing resistor, wherein the first sensing resistor is coupled in series with the excitation inductor, and an inductive current flows through the excitation inductor and the first sensing resistor; a power switch, selectively coupling the first sensing resistor to a ground potential according to a clock potential; an output stage circuit, generating an output potential according to the induced potential; and A microcontroller generates the clock potential, wherein the microcontroller further detects a potential difference of the first sensing resistor to calculate a response slope of the inductor current; If the microcontroller determines that the response slope of the inductor current is abnormal, the microcontroller will further generate a warning potential. A power supply as claimed 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. A power supply as in claim 2, wherein 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 a third node, the secondary coil has a first end and a second end, the first end of the secondary coil is coupled to a fourth node to output the induced potential, the second end of the secondary coil is coupled to a common node, the first sensing resistor has a first end and a second end, the first end of the first sensing resistor is coupled to the third node, and the second end of the first sensing resistor is coupled to the second node. A power supply as claimed in claim 3, wherein the 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 clock potential, the first end of the first transistor is coupled to a fifth node, and the second end of the first transistor is coupled to the second node. The power supply of claim 4 further comprises: a second sensing resistor having a first end and a second end, wherein the first end of the second sensing resistor is coupled to the fifth node, and the second end of the second sensing resistor is coupled to the ground potential; wherein the microcontroller further receives a detection potential from the fifth node. A power supply as claimed in claim 5, wherein the output stage circuit comprises: a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is used to receive an inverted clock potential, the first terminal of the second transistor is coupled to an output node to output the output potential, and the second terminal of the second transistor is coupled to the fourth node to receive the induced potential; 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 a sixth node; and a third sensing resistor having a first terminal and a second terminal, wherein the first terminal of the third sensing resistor is coupled to the sixth node, and the second terminal of the third sensing resistor is coupled to the common node; The microcontroller further generates the inverted clock potential according to the clock potential; The microcontroller further receives a feedback potential from the sixth node. A power supply as claimed in claim 6, wherein if the microcontroller determines that the detection potential drops to 0 for the first time at a specific time point, the microcontroller is ready to continuously monitor the response slope of the inductor current. A power supply as claimed in claim 7, wherein after the specific time point, when the clock potential has a high logic level, the microcontroller calculates a sampling slope of the inductor current based on the potential difference of the first sensing resistor. As in the power supply of claim 8, wherein after the specific time point, when the clock potential has a low logical level, the microcontroller compares the response slope of the inductor current with an inverse of the sampling slope within a plurality of detection time intervals, and wherein if the response slope of the inductor current and the inverse of the sampling slope are not equal, the microcontroller will determine that an abnormality has occurred in the response slope of the inductor current. As in the power supply of claim 9, if the feedback potential is higher than or equal to a critical potential, the microcontroller will further shorten the length of each of the detection time intervals.

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