CN112000164B

CN112000164B - Power supply

Info

Publication number: CN112000164B
Application number: CN201910445933.4A
Authority: CN
Inventors: 詹子增
Original assignee: Acer Inc
Current assignee: Acer Inc
Priority date: 2019-05-27
Filing date: 2019-05-27
Publication date: 2022-04-05
Anticipated expiration: 2039-05-27
Also published as: CN112000164A

Abstract

A power supply, comprising: the circuit comprises a voltage division circuit, a first transformer, a comparator, a second transformer and an output stage circuit. The voltage divider circuit generates a reference potential according to an input potential. The first transformer generates a transformation potential and a feedback potential according to the input potential. The comparator compares the feedback potential with the reference potential to generate a comparison potential. The second transformer generates a control potential according to the comparison potential. The output stage circuit selectively generates an output potential according to the transformation potential and the control potential. If one of the input potentials is higher than or equal to a threshold potential, the output stage circuit will continuously output the output potential. If the root-mean-square value of the input potential is lower than the critical potential, the output stage circuit will stop outputting the output potential.

Description

Power supply

Technical Field

The present invention relates to a power supply, and more particularly to a power supply capable of increasing output stability.

Background

When the electronic device is powered by an external power source, the external power source is not stable enough, which sometimes causes undesirable phenomena such as "Voltage Dips" (or "Short interruptions"). Fig. 1 is a graph showing the relationship between the input potential of the external power source and time. As shown in fig. 1, during the first period T1, the input potential of the external power source is reduced by about 30%, which can be regarded as the aforementioned voltage sag phenomenon; in addition, in the second period T2, the input potential of the external power supply is lowered by about 100%, which may be regarded as the aforementioned short-time interruption phenomenon.

Conventional power supplies typically provide only a very short hold-up Time (Holding-up Time) in the face of a momentary drop in voltage from an external power source, which is difficult to comply with International Electro Technical Commission (IEC) specifications. In view of the above, a new solution is needed to overcome the problems in the prior art.

Disclosure of Invention

In a preferred embodiment, the present invention provides a power supply, comprising: a voltage divider circuit for generating a reference potential according to an input potential; a first transformer for generating a transformation potential and a feedback potential according to the input potential; a comparator for comparing the feedback potential with the reference potential to generate a comparison potential; a second transformer for generating a control potential according to the comparison potential; and an output stage circuit for selectively generating an output potential according to the transformed potential and the control potential; if the root mean square value of the input potential is higher than or equal to a critical potential, the output stage circuit will continuously output the output potential, and if the root mean square value of the input potential is lower than the critical potential, the output stage circuit will stop outputting the output potential.

Drawings

Fig. 1 is a graph showing the relationship between the input potential of the external power source and time.

Fig. 2 is a schematic diagram illustrating a power supply according to an embodiment of the invention.

Fig. 3 is a schematic diagram illustrating a power supply according to an embodiment of the invention.

Fig. 4A is a diagram showing potential waveforms of a conventional power supply.

FIG. 4B is a diagram showing a potential waveform of the power supply according to an embodiment of the invention.

Fig. 5 is a schematic diagram illustrating a power supply according to another embodiment of the invention.

Description of reference numerals:

200. 300, 500-power supply; 210. 310-voltage division circuit;

220. 320-a first transformer; 230. 330 to a comparator;

240. 340-a second transformer; 250. 350-output stage circuit;

321 to a first main coil; 322-a first secondary coil;

333-auxiliary coil; 341 to a second main coil;

342 to a second sub-winding; c1-first capacitor;

c2-second capacitor; c3-third capacitor;

c4-fourth capacitor; c5-fifth capacitor;

c6 sixth capacitor; d1-a first diode;

d2-second diode; d3-third diode;

d4 fourth diode; d5-fifth diode;

d6 sixth diode; d7 seventh diode;

d8 eighth diode; m1-first transistor;

m3 third transistor; n1-first node;

n2-second node; n3-third node;

n4-fourth node; n5-fifth node;

n6-sixth node; n7-seventh node;

n8-eighth node; n9-ninth node;

n10-tenth node; n11-eleventh node;

n12-twelfth node; n13-thirteenth node;

n14 to a fourteenth node; n15-fifteenth node;

n16 sixteenth node; n17-seventeenth node;

NIN-input node; NOUT-output node;

q2-second transistor; r1-first resistor;

r2-second resistor; r3 third resistor;

r4 fourth resistor; r5-fifth resistor;

r6 sixth resistor; r7 seventh resistor;

t1-first period; t2-second period;

t3, T4-maintenance time; VC is controlled potential;

VF-feedback potential; VIN-input potential;

VL-fixed potential level; VM-comparative potential;

VOUT-output potential; VR to reference potential;

VT-transformation potential; VTH-critical potential;

VSS to ground potential.

Detailed Description

In order to make the objects, features and advantages of the present invention comprehensible, specific embodiments accompanied with figures are described in detail below.

Certain terms are used throughout the description and the following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This specification and related documents do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The term "substantially" means within an acceptable error range, within which a person skilled in the art can solve the technical problem to achieve the basic technical result. In addition, the term "coupled" is used herein to encompass any direct or indirect electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

Fig. 2 is a schematic diagram illustrating a power supply 200 according to an embodiment of the invention. For example, the power supply 200 may be applied to a desktop computer, a notebook computer, or an integrated computer. As shown in fig. 2, the power supply 200 includes: a Voltage Dividing Circuit (Voltage Dividing Circuit)210, a first transformer 220, a comparator 230, a second transformer 240, and an output stage Circuit 250. The voltage divider 210 generates a reference voltage level VR according to an input voltage level VIN, wherein the reference voltage level VR may be equal to a specific ratio (e.g., 30%, 40%, 50%, or 60%) of the input voltage level VIN. The input potential VIN may be derived from an external power source, wherein the input potential VIN may be an ac potential with any frequency and any amplitude. For example, the frequency of the input potential VIN may be about 60Hz, and the Root-Mean-Square Value (RMS Value) of the input potential VIN may be about 110V or 220V, but is not limited thereto. The first transformer 220 generates a transformation potential VT and a feedback potential VF according to the input potential VIN. The comparator 230 compares the feedback potential VF with the reference potential VR to generate a comparison potential VM. The second transformer 240 generates a control potential VC according to the comparison potential VM. The output stage circuit 250 selectively generates an output voltage VOUT according to the transformation voltage VT and the control voltage VC. The output potential VOUT may be a dc potential having an arbitrary level (level). For example, the level of the output voltage VOUT may be substantially constant 19V, but is not limited thereto. In detail, if the root-mean-square value of the input potential VIN is higher than or equal to a threshold potential VTH, the output stage circuit 250 will continuously output the output potential VOUT; on the contrary, if the root-mean-square value of the input potential VIN is lower than the threshold potential VTH, the output stage circuit 250 will stop outputting the output potential VOUT. In some embodiments, the threshold voltage VTH is set to a predetermined ratio of the maximum root mean square value of the input voltage VIN, and the predetermined ratio is lower than 70%, for example: 60%, 50%, or 40%, but is not limited thereto. Assuming that the maximum root mean square value of the input voltage VIN is 100V, the threshold voltage VTH may be 60V, 50V, or 40V. This circuit design helps to increase the output stability of the power supply 200 according to actual measurement results. It should be noted that, although not shown in fig. 2, the power supply 200 may also include other components, such as: a Voltage Regulator (and) a Negative Feedback Circuit (Negative Feedback Circuit).

The following embodiment will describe the detailed structure and operation of the power supply 200. It must be understood that these drawings and descriptions are only exemplary and are not intended to limit the scope of the present invention.

Fig. 3 shows a schematic diagram of a power supply 300 according to an embodiment of the invention. In the embodiment of fig. 3, the power supply 300 has an input node NIN and an output node NOUT, and includes a voltage divider 310, a first transformer 320, a comparator 330, a second transformer 340, and an output stage circuit 350. The input node NIN of the power supply 300 can receive an input voltage VIN from an external power source, and the output node NOUT of the power supply 300 can be used for outputting an output voltage VOUT to an electronic device (e.g., a notebook computer).

The voltage divider circuit 310 includes a first resistor R1, a second resistor R2, a first diode D1, and a first capacitor C1. 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 input node NIN for receiving the input potential VIN, and the second end of the first resistor R1 is coupled to a first node N1. The second resistor R2 has a first terminal and a second terminal, wherein the first terminal of the second resistor R2 is coupled to the first node N1, and the second terminal of the second resistor R2 is coupled to a ground potential VSS (e.g., 0V). The first diode D1 has an anode and a cathode, wherein the anode of the first diode D1 is coupled to the first node N1, and the cathode of the first diode D1 is coupled to a second node N2 for outputting a reference potential VR. The first capacitor C1 has a first terminal and a second terminal, wherein the first terminal of the first capacitor C1 is coupled to the second node N2, and the second terminal of the first capacitor C1 is coupled to the ground potential VSS.

The first transformer 320 includes a first primary winding 321, a first secondary winding 322, an auxiliary winding 323, a second diode D2, a third diode D3, a second capacitor C2, a third capacitor C3, and a first transistor M1. The first primary winding 321 and the auxiliary winding 323 can be located on the same side of the first transformer 320, and the first secondary winding 322 can be located on the opposite side of the first transformer 320. The first primary winding 321 has a first terminal and a second terminal, wherein the first terminal of the first primary winding 321 is coupled to the input node NIN for receiving the input potential VIN, and the second terminal of the first primary winding 321 is coupled to a third node N3. The first secondary winding 322 has a first end and a second end, wherein the first end of the first secondary winding 322 is coupled to a fourth node N4, and the second end of the first secondary winding 322 is coupled to the ground potential VSS. The first transistor M1 may be an nmos field effect transistor. The first transistor M1 has a control terminal (or a Gate), a first terminal (or a Source), and a second terminal (or a Drain), wherein the control terminal of the first transistor M1 is used for receiving an external control potential VE, 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 third node N3. For example, the external control voltage VE can be a Clock (Clock) or a DC voltage. The second diode D2 has an anode and a cathode, wherein the anode of the second diode D2 is coupled to the fourth node N4, and the cathode of the second diode D2 is coupled to a fifth node N5 for outputting a transforming potential VT. The second capacitor C2 has a first terminal and a second terminal, wherein the first terminal of the second capacitor C2 is coupled to the fifth node N5, and the second terminal of the second capacitor C2 is coupled to the ground potential VSS. The auxiliary coil 323 has a first end and a second end, wherein the first end of the auxiliary coil 323 is coupled to a sixth node N6, and the second end of the auxiliary coil 323 is coupled to the ground potential VSS. The third diode D3 has an anode and a cathode, wherein the anode of the third diode D3 is coupled to the sixth node N6, and the cathode of the third diode D3 is coupled to a seventh node N7 for outputting a feedback potential VF. The third capacitor C3 has a first terminal and a second terminal, wherein the first terminal of the third capacitor C3 is coupled to the seventh node N7, and the second terminal of the third capacitor C3 is coupled to the ground potential VSS.

The comparator 330 has a positive input terminal, a negative input terminal, and an output terminal, wherein the positive input terminal of the comparator 330 is for receiving the feedback potential VF, the negative input terminal of the comparator 330 is for receiving the reference potential VR, and the output terminal of the comparator 330 is coupled to an eighth node N8 to output a comparison potential VM.

The second transformer 340 includes a second primary winding 341, a second secondary winding 342, a third resistor R3, a fourth diode D4, a fifth diode D5, a fourth capacitor C4, and a fifth capacitor C5. The fourth diode D4 has an anode and a cathode, wherein the anode of the fourth diode D4 is coupled to the eighth node N8 for receiving the comparison potential VM, and the cathode of the fourth diode D4 is coupled to a ninth node N9. The third resistor R3 has a first end and a second end, wherein the first end of the third resistor R3 is coupled to the ninth node N9, and the second end of the third resistor R3 is coupled to a tenth node N10. The fourth capacitor C4 has a first terminal and a second terminal, wherein the first terminal of the fourth capacitor C4 is coupled to the tenth node N10, and the second terminal of the fourth capacitor C4 is coupled to the ground potential VSS. The third resistor R3 and the fourth capacitor R4 may collectively form a low pass filter. The second primary winding 341 has a first end and a second end, wherein the first end of the second primary winding 341 is coupled to the tenth node N10, and the second end of the second primary winding 341 is coupled to the ground potential VSS. The second sub-coil 342 has a first end and a second end, wherein the first end of the second sub-coil 342 is coupled to an eleventh node N11, and the second end of the second sub-coil 342 is coupled to the ground potential VSS. The fifth diode D5 has an anode and a cathode, wherein the anode of the fifth diode D5 is coupled to the eleventh node N11, and the cathode of the fifth diode D5 is coupled to a twelfth node N12 for outputting a control potential VC. The fifth capacitor C5 has a first terminal and a second terminal, wherein the first terminal of the fifth capacitor C5 is coupled to the twelfth node N12, and the second terminal of the fifth capacitor C5 is coupled to the ground potential VSS.

The output stage circuit 350 includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a sixth diode D6, a sixth capacitor C6, a second transistor Q2, and a third transistor M3. The fourth resistor R4 has a first terminal and a second terminal, wherein the first terminal of the fourth resistor R4 is coupled to the twelfth node N12 for receiving the control potential VC, and the second terminal of the fourth resistor R4 is coupled to a thirteenth node N13. The second transistor Q2 may be an NPN type bipolar junction transistor. The second transistor Q2 has a control terminal (or a Base), a first terminal (or an Emitter), and a second terminal (or a Collector), wherein the control terminal of the second transistor Q2 is coupled to the thirteenth node N13, the first terminal of the second transistor Q2 is coupled to the ground potential VSS, and the second terminal of the second transistor Q2 is coupled to a fourteenth node N14. The sixth diode D6 has an anode and a cathode, wherein the anode of the sixth diode D6 is coupled to the fifth node N5 for receiving the transforming potential VT, and the cathode of the sixth diode D6 is coupled to a fifteenth node N15. The fifth resistor R5 has a first end and a second end, wherein the first end of the fifth resistor R5 is coupled to the fifteenth node N15, and the second end of the fifth resistor R5 is coupled to the fourteenth node N14. The sixth resistor R6 has a first end and a second end, wherein the first end of the sixth resistor R6 is coupled to the fifteenth node N15, and the second end of the sixth resistor R6 is coupled to a sixteenth node N16. The seventh resistor R7 has a first end and a second end, wherein the first end of the seventh resistor R7 is coupled to the fourteenth node N14, and the second end of the seventh resistor R7 is coupled to a seventeenth node N17. The third transistor M3 may be an nmos field effect transistor. The third transistor M3 has a control terminal (or a Gate), a first terminal (or a Source), and a second terminal (or a Drain), wherein the control terminal of the third transistor M3 is coupled to the seventeenth node N17, the first terminal of the third transistor M3 is coupled to the output node NOUT to output the output potential VOUT, and the second terminal of the third transistor M3 is coupled to the sixteenth node N16. The sixth capacitor C6 has a first terminal and a second terminal, wherein the first terminal of the sixth capacitor C6 is coupled to the output node NOUT, and the second terminal of the sixth capacitor C6 is coupled to the ground potential VSS.

The operation principle of the power supply 300 may be as follows. The comparator 330, the second transistor Q2, and the third transistor M3 are used as the main switching elements of the power supply 300, and can be used to determine whether to output the aforementioned output voltage VOUT. The first transformer 320 may provide a negative feedback control mechanism, which may be used to adjust the switching operation of the comparator 330. Generally, if the root-mean-square value of the input voltage VIN is higher than or equal to a threshold voltage VTH, the feedback voltage VF will drop below the reference voltage VR, and the comparator 330 will generate the comparison voltage VM with a low logic level. The second transformer 340 generates the control potential VC of a low logic level according to the comparison potential VM, such that the second transistor Q2 is disabled and the third transistor M3 is enabled. Therefore, the output stage circuit 350 can continuously output the output potential VOUT. Conversely, if the root-mean-square value of the input voltage VIN is lower than the threshold voltage VTH, the feedback voltage VF will rise above the reference voltage VR, and the comparator 330 will generate the comparison voltage VM with a high logic level. The second transformer 340 generates the control voltage VC with a high logic level according to the comparison voltage VM, such that the second transistor Q2 is enabled. Since the enabled second transistor Q2 can pull down the potential at the seventeenth node N17, the third transistor M3 will be disabled. Therefore, the output circuit stage 350 will stop outputting the aforementioned output potential VOUT. It should be noted that the threshold voltage VTH is related to the setting of the reference voltage VR. By changing the ratio of the resistances of the first resistor R1 and the second resistor R2 (i.e., a voltage division ratio of the voltage divider 310), the designer can freely adjust the reference voltage VR and the corresponding threshold voltage VTH. In some embodiments, the threshold voltage VTH is equal to a predetermined ratio of the maximum root mean square value of the input voltage VIN, and the predetermined ratio is lower than 70%. For example, if the maximum root mean square value of the input potential VIN is 100V, the threshold potential VTH may be set to 60V (lower than 70V), but is not limited thereto.

Assuming that the frequency of the input voltage VIN is 60Hz and the maximum root mean square value of the input voltage VIN is 100V, the output characteristics of the power supply 300 of the present invention and the conventional power supply can be compared in the following fig. 4A and 4B.

Fig. 4A is a diagram showing potential waveforms of a conventional power supply. As shown in fig. 4A, in the conventional design, when the Voltage droop (Voltage Dips) occurs in the external power source and the input Voltage VIN reaches only 70% of its maximum root mean square value, the output Voltage VOUT will quickly drop from a fixed Voltage level VL back to 0V (i.e., the ground Voltage VSS). According to the measurement results of fig. 4A, if a test of voltage transient drop (duration is about 17ms) is encountered, the Holding-up Time T3 of the conventional power supply may be only about 10ms, which cannot meet the general application requirements.

Fig. 4B is a diagram illustrating a potential waveform of the power supply 300 according to an embodiment of the invention. As shown in fig. 4B, under the design of the present invention, when the voltage of the external power supply drops instantaneously and the input voltage VIN only reaches 70% of its maximum root mean square value, the output voltage VOUT can still be maintained at the fixed voltage level VL without any drop-back (since the input voltage VIN is still higher than 60% of its maximum root mean square value). According to the measurement results of fig. 4B, if a voltage sag test is performed (the duration is also about 17ms), the holding time T4 of the power supply 300 of the present invention is considered to be approaching infinity. It should be noted that by properly controlling the threshold potential VTH, the power supply 300 of the present invention can be completely free from the negative effects of voltage transient drops.

In some embodiments, the component parameters of the power supply 300 may be as follows. The first resistor R1 may have a resistance value between 380k Ω and 420k Ω, preferably 400k Ω. The resistance value of the second resistor R2 may be between 570k Ω to 630k Ω, preferably 600k Ω. The resistance value of the third resistor R3 may be between 9.5k Ω and 10.5k Ω, preferably 10k Ω. The resistance value of the fourth resistor R4 may be between 9.5k Ω and 10.5k Ω, preferably 10k Ω. The resistance value of the fifth resistor R5 may be between 9.5k Ω and 10.5k Ω, preferably 10k Ω. The resistance value of the sixth resistor R6 may be between 9.5k Ω and 10.5k Ω, preferably 10k Ω. The resistance value of the seventh resistor R7 may be between 95 Ω to 105 Ω, preferably 100 Ω. The capacitance of the first capacitor C1 may be between 42.3 μ F and 51.7 μ F, preferably 47 μ F. The capacitance of the second capacitor C2 may be between 42.3 μ F and 51.7 μ F, preferably 47 μ F. The capacitance of the third capacitor C3 may be between 42.3 μ F and 51.7 μ F, preferably 47 μ F. The capacitance value of the fourth capacitor C4 may be between 0.95nF and 1.05nF, preferably 1 nF. The capacitance of the fifth capacitor C5 may be between 42.3 μ F and 51.7 μ F, preferably 47 μ F. The capacitance of the sixth capacitor C6 may be between 612 μ F and 748 μ F, preferably 680 μ F. The ratio of the number of turns of the first primary winding 321 to the first secondary winding 322 may be between 1 and 10, preferably 5. The ratio of the number of turns of the first main coil 321 to the auxiliary coil 323 may be between 1 and 10, preferably 5. The ratio of the number of turns of the second primary winding 341 to the second secondary winding 342 may be between 0.5 and 2, preferably 1. The above parameter ranges are derived from a plurality of experimental results, which help to optimize the conversion efficiency and the maintenance time of the power supply 300.

Fig. 5 is a schematic diagram illustrating a power supply 500 according to another embodiment of the invention. Fig. 5 is similar to fig. 3. In the embodiment of fig. 5, the power supply 500 further includes a seventh diode D7 and an eighth diode D8. The seventh diode D7 has an anode and a cathode, wherein the anode of the seventh diode D7 is coupled to the first terminal of the second transistor Q2, and the cathode of the seventh diode D7 is coupled to the ground potential VSS. The eighth diode D8 has an anode and a cathode, wherein the anode of the eighth diode D8 is coupled to the first terminal of the third transistor M3, and the cathode of the eighth diode D8 is coupled to the output node NOUT. The addition of the seventh diode D7 and the eighth diode D8 can block undesired reverse current in the power supply 500, thereby further improving the reliability of the power supply 500. The remaining features of the power supply 500 of fig. 5 are similar to those of the power supply 300 of fig. 3, so that the embodiments can achieve similar operation effects.

The invention provides a novel power supply, which comprises a comparator capable of automatically switching different output modes. According to the actual measurement result, the power supply using the comparator can have a longer holding time to meet the International Electrotechnical Commission (IEC) specification. Generally, the present invention has at least the advantage of higher output stability compared to the conventional design, so it is very suitable for various electronic devices.

It should be noted that the above-mentioned potential, current, resistance, inductance, capacitance, and other device parameters are not limitations of the present invention. The designer can adjust these settings according to different needs. The power supply of the present invention is not limited to the states illustrated in fig. 1 to 5. The present invention may include only any one or more features of any one or more of the embodiments of fig. 1-5. In other words, not all illustrated features may be implemented in a power supply of the present invention. Although embodiments of the present invention use mosfets and bjts as examples, the present invention is not limited thereto, and other types of transistors can be used by those skilled in the art, such as: junction field effect transistors, fin field effect transistors, etc., without affecting the effect of the present invention.

Ordinal numbers such as "first," "second," "third," etc., in the specification and in the claims, do not have a sequential relationship with each other, but are used merely to identify two different elements having the same name.

Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A power supply, comprising:

a voltage divider circuit for generating a reference potential according to an input potential;

a first transformer for generating a transformation potential and a feedback potential according to the input potential;

a comparator for comparing the feedback potential with the reference potential to generate a comparison potential;

a second transformer for generating a control potential according to the comparison potential; and

an output stage circuit for selectively generating an output potential according to the transformation potential and the control potential;

wherein if the root mean square value of the input potential is higher than or equal to a critical potential, the output stage circuit will continue to output the output potential, and if the root mean square value of the input potential is lower than the critical potential, the output stage circuit will stop outputting the output potential;

wherein this bleeder circuit includes:

a first resistor having a first end and a second end, wherein the first end of the first resistor is coupled to an input node for receiving the input potential, and the second end of the first resistor is coupled to a first node;

a second resistor having a first end and a second end, wherein the first end of the second resistor is coupled to the first node and the second end of the second resistor is coupled to a ground potential;

a first diode having an anode and a cathode, wherein the anode of the first diode is coupled to the first node, and the cathode of the first diode is coupled to a second node to output the reference potential; and

a first capacitor having a first terminal and a second terminal, wherein the first terminal of the first capacitor is coupled to the second node and the second terminal of the first capacitor is coupled to the ground potential.

2. The power supply of claim 1, wherein the first transformer comprises:

a first primary winding having a first end coupled to the input node for receiving the input potential and a second end coupled to a third node;

a first secondary coil having a first end and a second end, wherein the first end of the first secondary coil is coupled to a fourth node and the second end of the first secondary coil is coupled to the ground potential;

a first transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the first transistor is configured to receive an external control 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 third node;

a second diode having an anode and a cathode, wherein the anode of the second diode is coupled to the fourth node, and the cathode of the second diode is coupled to a fifth node to output the transformed voltage potential; and

a second capacitor having a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the fifth node and the second terminal of the second capacitor is coupled to the ground potential.

3. The power supply of claim 2, wherein the first transformer further comprises:

an auxiliary coil having a first end and a second end, wherein the first end of the auxiliary coil is coupled to a sixth node and the second end of the auxiliary coil is coupled to the ground potential;

a third diode having an anode and a cathode, wherein the anode of the third diode is coupled to the sixth node, and the cathode of the third diode is coupled to a seventh node to output the feedback potential; and

a third capacitor having a first terminal and a second terminal, wherein the first terminal of the third capacitor is coupled to the seventh node and the second terminal of the third capacitor is coupled to the ground potential.

4. The power supply according to claim 2, wherein the comparator has a positive input terminal for receiving the feedback potential, a negative input terminal for receiving the reference potential, and an output terminal coupled to an eighth node for outputting the comparison potential.

5. The power supply of claim 4, wherein the second transformer comprises:

a fourth diode having an anode and a cathode, wherein the anode of the fourth diode is coupled to the eighth node for receiving the comparison potential, and the cathode of the fourth diode is coupled to a ninth node;

a third resistor having a first end and a second end, wherein the first end of the third resistor is coupled to the ninth node and the second end of the third resistor is coupled to a tenth node;

a fourth capacitor having a first terminal and a second terminal, wherein the first terminal of the fourth capacitor is coupled to the tenth node and the second terminal of the fourth capacitor is coupled to the ground potential; and

a second primary winding having a first end and a second end, wherein the first end of the second primary winding is coupled to the tenth node and the second end of the second primary winding is coupled to the ground potential.

6. The power supply of claim 5, wherein the second transformer further comprises:

a second secondary winding having a first end and a second end, wherein the first end of the second secondary winding is coupled to an eleventh node and the second end of the second secondary winding is coupled to the ground potential;

a fifth diode having an anode and a cathode, wherein the anode of the fifth diode is coupled to the eleventh node, and the cathode of the fifth diode is coupled to a twelfth node for outputting the control potential; and

a fifth capacitor having a first terminal and a second terminal, wherein the first terminal of the fifth capacitor is coupled to the twelfth node and the second terminal of the fifth capacitor is coupled to the ground potential.

7. The power supply of claim 6, wherein the output stage circuit comprises:

a fourth resistor having a first end and a second end, wherein the first end of the fourth resistor is coupled to the twelfth node for receiving the control potential, and the second end of the fourth resistor is coupled to a thirteenth node; and

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 the thirteenth node, the first terminal of the second transistor is coupled to the ground potential, and the second terminal of the second transistor is coupled to a fourteenth node.

8. The power supply of claim 7, wherein the output stage circuit further comprises:

a sixth diode having an anode and a cathode, wherein the anode of the sixth diode is coupled to the fifth node for receiving the transforming potential, and the cathode of the sixth diode is coupled to a fifteenth node;

a fifth resistor having a first end and a second end, wherein the first end of the fifth resistor is coupled to the fifteenth node and the second end of the fifth resistor is coupled to the fourteenth node;

a sixth resistor having a first end and a second end, wherein the first end of the sixth resistor is coupled to the fifteenth node and the second end of the sixth resistor is coupled to a sixteenth node;

a seventh resistor having a first end and a second end, wherein the first end of the seventh resistor is coupled to the fourteenth node and the second end of the seventh resistor is coupled to a seventeenth node;

a third transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the third transistor is coupled to the seventeenth node, the first terminal of the third transistor is coupled to an output node for outputting the output voltage, and the second terminal of the third transistor is coupled to the sixteenth node; and

a sixth capacitor having a first terminal and a second terminal, wherein the first terminal of the sixth capacitor is coupled to the output node and the second terminal of the sixth capacitor is coupled to the ground potential.

9. The power supply of claim 8, wherein the output stage circuit further comprises:

a seventh diode having an anode and a cathode, wherein the anode of the seventh diode is coupled to the first terminal of the second transistor, and the cathode of the seventh diode is coupled to the ground potential; and

an eighth diode having an anode and a cathode, wherein the anode of the eighth diode is coupled to the first terminal of the third transistor, and the cathode of the eighth diode is coupled to the output node.