TWM445302U - Power converter with a self-driven synchronous rectification circuit - Google Patents

Abstract

A power converter with a self-driven synchronous rectification (SR) circuit is provided. The self-driven synchronous rectification (SR) circuit equipped in the provided power converter can be self-operated without additionally adding any peripheral circuit relating to control. Accordingly, by equipping the self-driven SR circuit in the provided power converter, not only the efficiency of the provided power converter can be improved, but also the cost of the provided power converter can be reduced. Besides, all of power switches relating to the self-driven SR circuit are changed to SMD fabricated for directly mounting on a solder side of a PCB. Accordingly, not only the circuit volume of the applied power converter can be compressed, but also the problem of accumulating heat caused by gathering multi-element with high temperature can be improved.

Description

Power converter with self-excited synchronous rectification line

This creation is related to a power conversion technique, and in particular to a power converter having a self-excited synchronous rectification line.

Today's more common power converter architecture can be forward or flyback, but whether it is a forward or reverse power converter, it is placed twice in the transformer. Most of the rectification circuits on the side are implemented as rectification diodes. However, since the rectifying diode generates a considerable conduction loss when it is turned on and off, the power loss of the applied power converter increases, thereby affecting the applied power conversion. The overall efficiency of the device.

In view of this, a synchronous rectification circuit (SR circuit) consisting of a power switch gradually replaces the internal side of the conventional forward or reverse power converter on the secondary side of the transformer. Polar body) rectification line. Since the conduction loss caused by the turn-on of any power switch in the synchronous rectification line is low, the power loss of the applied power converter can be reduced, thereby improving the overall efficiency of the applied power converter.

Today's synchronous circuit (SR circuit) is driven by two types, externally-driven and self-driven. In terms of its exciting drive, it must be additionally designed in the power converter. An independent control circuit is used to generate control signals to control the operation of each power switch in the synchronous rectification line. In addition, in the self-excited driving mode, a set of auxiliary windings must be additionally added on the secondary side of the transformer to generate control signals to control the operation of each power switch in the synchronous rectification line.

However, whether it is an excitation or a self-excited drive, additional control-related peripheral lines must be added to control the operation of each power switch in the synchronous rectification line. As a result, the cost of the power converter will increase.

On the other hand, each power switch in the conventional self-excited synchronous rectification line is arranged on the component surface of the printed circuit board in a component type of a plug-in package (DIP), and its three pins (PIN) are printed. The component surface of the circuit board is drilled and inserted into the soldering surface of the printed circuit board, and is connected by soldering to the related components (for example, the secondary side of the transformer, the passive component for storing energy, etc.). Under this condition, since each power switch in the self-excited synchronous rectification circuit generates high temperature during operation, in order to avoid damage to the power switch operation, most of the current power switches are locked/posted on the back of each power switch ( A heat sink for the heat sink. Thus, based on the height of the heat sink that is locked/applied, the circuit board of the applied power converter becomes bulky.

In addition, in the self-excited synchronous rectification line, most of the power switches are mostly disposed in the same area on the component surface of the printed circuit board and gathered in the vicinity of the transformer. Under these conditions, so many high-temperature components are concentrated on the component surface of the printed circuit board, and it is also very easy to cause heat build-up.

In view of this, the present invention provides a power converter having a self-excited synchronous rectification line, which can operate by itself without additional control-related peripheral lines, thereby reducing the cost of the applied power converter. In addition, all the power switches associated with the self-excited synchronous rectification line are modified to be directly adhered to the soldering surface of the printed circuit board by the surface-adhesive element, thereby minimizing the board volume of the applied power converter and improving The problem of accumulated heat accumulated by high temperature components.

The present application provides a power converter that includes a printed circuit board, a transformer, and a self-excited synchronous rectification line. The printed circuit board has a component surface and a solder surface. The transformer is disposed on the component surface of the printed circuit board and has a primary side and a first secondary side. The self-excited synchronous rectification circuit includes a plurality of surface-adhesive power switches directly adhered to the soldering surface of the printed circuit board, and the first portion of the plurality of surface-adhesive power switches is coupled to the first secondary side of the transformer.

In an embodiment of the present invention, the first portion of the surface-adhesive power switch comprises: a first surface-adhesive power switch and a second surface-adhesive power switch. The first end of the first surface-adhesive power switch is coupled to the same end of the first secondary side of the transformer, and the control end of the first surface-adhesive power switch is coupled to a first node. The first end of the second surface-adhesive power switch is coupled to the different end of the first secondary side of the transformer, and the second end of the second surface-adhesive power switch is coupled to the second end of the first surface-adhesive power switch, and The control end of the second surface-adhesive power switch is coupled to A second node.

In an embodiment of the present invention, the transformer may have a second secondary side, and the second portion of the plurality of surface-adhesive power switches is coupled to the second secondary side of the transformer. Under this condition, the second portion of the surface-adhesive power switch comprises: a third surface-adhesive power switch and a fourth surface-adhesive power switch. The first end of the third surface-adhesive power switch is coupled to the same end of the second secondary side of the transformer, and the control end of the third surface-adhesive power switch is coupled to the first node. The first end of the fourth surface adhesive power switch is coupled to the second end of the second secondary side of the transformer, and the second end of the fourth surface adhesive power switch is coupled to the second end of the third surface adhesive power switch. The control end of the fourth surface-adhesive power switch is coupled to the second node.

In an embodiment of the present invention, the transformer may have a third secondary side, and the third portion of the plurality of surface-adhesive power switches is coupled to the third secondary side of the transformer. Under this condition, the third surface of the surface-adhesive power switch comprises: a fifth surface-adhesive power switch and a sixth surface-adhesive power switch. The first end of the fifth surface-adhesive power switch is coupled to the same end of the third secondary side of the transformer, and the control end of the fifth surface-adhesive power switch is coupled to the first node. The first end of the sixth surface-adhesive power switch is coupled to the different end of the third secondary side of the transformer, and the second end of the sixth surface-adhesive power switch is coupled to the second end of the fifth surface-adhesive power switch, and The control end of the sixth surface-adhesive power switch is coupled to the second node.

In an embodiment of the present invention, the first node is coupled to a transformer The second end of the transformer is coupled to the second end of the transformer, and the second node is coupled to the same end of the first secondary side of the transformer.

Based on the above, the self-excited synchronous rectification line provided in the power converter can be operated by itself without additionally adding a control-related peripheral line. In this way, the self-excited synchronous rectification circuit provided in the power converter can not only improve the overall efficiency of the power converter, but also reduce the cost of the power converter. In addition, all of the power switches associated with the self-excited synchronous rectification line are modified to be surface-bonded components and adhere directly to the soldering surface of the printed circuit board. In this way, the board volume of the power converter to be applied can be miniaturized, and the problem of accumulated heat accumulated by the high-temperature components can also be improved.

In order to make the above features and advantages of the present invention more comprehensible, the following embodiments are described in detail with reference to the accompanying drawings.

Reference will now be made in detail to the exemplary embodiments embodiments In addition, wherever possible, the same reference numerals in the drawings

FIG. 1 is a schematic diagram of a power converter 10 according to an exemplary embodiment of the present invention. Referring to FIG. 1, a power converter 10 of the present exemplary embodiment includes a print circuit board (PCB) 101, a transformer T, and a self-driven synchronous rectification circuit (self-driven synchronous rectification circuit). Self-driven SR circuit) 103. Among them, the printed circuit board 101 has a component side 101a (shown in FIG. 2A) and a solder side 101b (shown in FIG. 2B).

On the other hand, FIG. 3 is a schematic diagram showing the circuit implementation of the power converter 10 of FIG. 1 to 3, in the present exemplary embodiment, the transformer T is disposed on the element surface 101a of the printed circuit board 101, and has a primary winding NP and a first winding. NS1, second secondary side NS2, and third secondary side NS3.

The self-excited synchronous rectification line 103 includes a plurality of surface-mounted power switches (SMD power switches) Q1 to Q6 that are directly adhered to the soldering surface 101b of the printed circuit board 101. The first part of the surface-adhesive power switches Q1 to Q6 (for example, Q1 and Q2) is connected to the first secondary side NS1 of the transformer T. More specifically, the first end of the surface-adhesive power switch Q1 is coupled to the common-polarity terminal of the first secondary side NS1 of the transformer T, and the control end of the surface-adhesive power switch Q1. Then coupled to node ND1. The first end of the surface-adhesive power switch Q2 is coupled to the opposite-polarity terminal of the first secondary side NS1 of the transformer T, and the second end of the surface-adhesive power switch Q2 is coupled to the surface. The second end of the power switch Q1, and the control end of the surface-adhesive power switch Q2 is coupled to the node ND2.

In addition, the second part of the surface-adhesive power switches Q1 to Q6 (for example, Q3 and Q4) is connected to the second secondary side NS2 of the transformer T. More specifically, the first end of the surface-adhesive power switch Q3 is coupled to the transformer T. The second end side of the same name end of the NS2, and the control end of the surface adhesive power switch Q3 is coupled to the node ND1. The first end of the surface-adhesive power switch Q4 is coupled to the different end of the second secondary side NS2 of the transformer T, and the second end of the surface-adhesive power switch Q4 is coupled to the second end of the surface-adhesive power switch Q3, and the surface The control end of the adhesive power switch Q4 is coupled to the node ND2. In the present exemplary embodiment, the node ND1 may be coupled to the different end of the second secondary side NS2 of the transformer T, and the node ND2 is coupled to the same-named end of the first secondary side NS1 of the transformer T.

Furthermore, the third portion of the surface-adhesive power switches Q1 to Q6 (for example, Q5 and Q6) is connected to the third secondary side NS3 of the transformer T. More specifically, the first end of the surface-adhesive power switch Q5 is coupled to the same end of the third secondary side NS3 of the transformer T, and the control end of the surface-adhesive power switch Q5 is coupled to the node ND1. The first end of the surface-adhesive power switch Q6 is coupled to the different end of the third secondary side NS3 of the transformer T, and the second end of the surface-adhesive power switch Q6 is coupled to the second end of the surface-adhesive power switch Q5, and the surface The control end of the adhesive power switch Q6 is coupled to the node ND2. It can be seen that the surface-adhesive power switches Q1, Q3 and Q5 are respectively disposed on the low side path of the first to third secondary sides NS1 to NS3 of the transformer T.

In addition, the power converter 10 may further include: an input stage 301, an output stage 303-1 to 303-3, and a clamping circuit 305-1 to 305-3. . The input stage 301 is configured to receive an input voltage VIN. Moreover, the primary side NP of the transformer T is coupled to the input stage 301 and is responsive to at least one control signal. The control signal (eg, control signals CS1 and/or CS2) receives the input voltage VIN from the input stage 301 (described in more detail later).

The output stage 303-1 is connected to the first end and the second end of the surface-adhesive power switch Q2 for reacting with the input voltage VIN and the turns ratio of the primary side NP of the transformer T to the first secondary side NS1 (turns) The ratio, NP/NS1) generates the first power source V1. Similarly, the output stage 303-2 is coupled to the first end and the second end of the surface-adhesive power switch Q4 for reacting to the input voltage VIN and the number of turns of the primary side NP of the transformer T and the second secondary side NS2. The second power source V2 is generated in comparison with (NP/NS2). In addition, the output stage 303-3 is coupled to the first end and the second end of the surface-adhesive power switch Q6 for reacting to the input voltage VIN and the turns ratio of the primary side NP of the transformer T to the third secondary side NS3. (NP/NS3) generates a third power source V3.

In the present exemplary embodiment, the output stages 303-1~303-3 may all be forward-based output stages. Under this condition, as shown in FIG. 4, the output stages 303-1 to 303-3 may respectively include an output inductor LO and an output capacitor CO, and the power converter 10 may be a forward direction. Forward power converter.

The clamp line 305-1 includes a pair of back-to-back Zener diodes ZD1 and ZD2, and is connected to the same name and the opposite end of the first secondary side NS1 of the transformer T. Between the voltage of the first secondary side NS1 of the transformer T is clamped. More specifically, the cathode of the Zener diode ZD1 is coupled to the same-named end of the first secondary side NS1 of the transformer T. Cathode coupling transformer T of Zener diode ZD2 The anode of the first secondary side NS1, and the anode of the Zener diode ZD2 is coupled to the anode of the Zener diode ZD1.

The clamp line 305-2 includes a diode D1 and a capacitor C1 connected in series, and is connected between the same name end and the different name end of the second secondary side NS2 of the transformer T for the second of the transformer T The voltage of the secondary side NS2 is clamped. More specifically, the cathode of the diode D1 is coupled to the different end of the second secondary side NS2 of the transformer T. The first end of the capacitor C1 is coupled to the anode of the diode D1, and the second end of the capacitor C1 is coupled to the same end of the second secondary side NS2 of the transformer T3.

The clamp line 305-3 includes a pair of back-to-back Zener diodes ZD3 and ZD4, and is connected between the same-named end and the different-named end of the third secondary side NS3 of the transformer T for the third of the transformer T The voltage of the secondary side NS3 is clamped. More specifically, the cathode of the Zener diode ZD3 is coupled to the same name end of the third secondary side NS3 of the transformer T. The cathode of the Zener diode ZD4 is coupled to the opposite end of the third secondary side NS3 of the transformer T, and the anode of the Zener diode ZD4 is coupled to the anode of the Zener diode ZD3.

On the other hand, if the input stage 301 receives only a single control signal, such as the control signal CS1, the input stage 301 is a single switch input stage. Under this condition, as shown in FIG. 5, the input stage 301 can include a power switch Q7. The first end of the power switch Q7 is coupled to the same end of the primary side NP of the transformer T, the second end of the power switch Q7 is coupled to the ground potential, and the control end of the power switch Q7 is used for receiving control. Signal CS1. In addition, the different end of the primary side NP of the transformer T1 is used to receive the input voltage VIN.

In the exemplary embodiment, the control signal CS1 may be a pulse width modulation signal (PWM signal). Under these conditions, the surface-adhesive power switches Q2, Q4 and Q6 and the power switch Q7 are only turned on-on in response to the enable of the control signal (pulse width modulation signal) CS1. In addition, the surface-adhesive power switches Q1, Q3, and Q5 are only turned on in response to the disable of the control signal (pulse width modulation signal) CS1.

Accordingly, when the input stage 301 is a single crystal input stage and the output stages 303-1~303-3 are output stages based on a forward architecture, when surface mount power switches Q2, Q4 and Q6 and power When the switch Q7 is synchronously turned on in response to the enable of the control signal (pulse width modulation signal) CS1, the energy of the output inductor LO previously stored in the output stages 303-1 to 303-3 will be separately directed to the output stage 303-1. The output capacitor CO of ~303-3 is charged, so that the output stages 303-1~303-3 respectively supply the first to third power sources V1~V3 to the load (load, not shown, for example, a computer system, but Not limited to this). In addition, when the surface-adhesive power switches Q1, Q3, and Q5 are turned on in response to the disable of the control signal (pulse width modulation signal) CS1, the output inductors LO of the output stages 303-1 to 303-3 are stored separately. can. In this way, in response to the control signal (pulse width modulation signal) CS1 being alternately enabled and disabled, the (forward) power converter 10 having a single crystal input stage can continuously supply the first to third power sources. V1~V3 to the load (computer system).

On the other hand, if the input stage 301 receives the control signals CS1 and CS2 at the same time, the input stage 301 is a dual switch input (dual switch input). Stage). Under this condition, as shown in FIG. 6, the input stage 301 can include power switches Q8 and Q9. The first ends of the power switches Q8 and Q9 are used to receive the input voltage VIN, and the second ends of the power switches Q8 and Q9 are respectively coupled to the different names of the primary side NP of the transformer T and the same name end, and the power switches Q8 and Q9 The control terminals receive control signals CS1 and CS2, respectively.

In the exemplary embodiment, the control signals CS1 and CS2 can both be PWM signals. Under these conditions, the surface-adhesive power switches Q2, Q4, and Q6 and the power switches Q8 and Q9 are only turned on in response to the enable of the control signals (pulse width modulation signals) CS1 and CS2. In addition, the surface-adhesive power switches Q1, Q3, and Q5 are only turned on in response to the disable of the control signals (pulse width modulation signals) CS1 and CS2.

Accordingly, when the input stage 301 is a dual crystal input stage and the output stages 301-1~301-3 are output stages based on a forward architecture, when surface mount power switches Q2, Q4 and Q6 and power When the switches Q8 and Q9 are turned on in response to the enable of the control signals (pulse width modulation signals) CS1 and CS2, the energy of the output inductors LO previously stored in the output stages 303-1 to 303-3 will be output separately. The output capacitors CO of the stages 303-1 to 303-3 are charged, so that the output stages 303-1 to 303-3 respectively supply the first to third power sources V1 to V3 to the load (computer system). In addition, when the power switches Q1, Q3 and Q5 are turned on in response to the disable of the control signals (pulse width modulation signals) CS1 and CS2, the output inductors LO of the output stages 303-1 to 303-3 are separately stored. . In this way, in response to the control signal (pulse width modulation signal) CS1 and CS2 alternately enabling and disabling, the (forward) power converter 10 having a dual crystal input stage is continuously supplied first to the first three Power supply V1~V3 is given to the load (computer system).

Therefore, it can be seen that the self-excited synchronous rectification line 103 provided in the power converter 10 can operate by itself without additionally adding a peripheral line related to the control, which is completely only reflected on the first secondary side NS1 of the transformer T. The voltage at the same name end and the second-order side NS2 operates at the different name end. Moreover, the self-excited synchronous rectification line 103 provided in the power converter 10 can be used simultaneously in applications of single crystal and twin crystal input stages. As a result, the self-excited synchronous rectification line 103 provided in the power converter 10 can not only improve the overall efficiency of the power converter 10, but also reduce the cost of the power converter 10.

On the other hand, since all of the power switches Q1 to Q6 of the self-excited synchronous rectification line 103 are changed to be surface-mounting elements (SMD), they are directly adhered to the bonding surface 101b of the printed circuit board 101. As a result, since the volume of the surface-adhesive power switches Q1 to Q6 is relatively small, the board size of the power converter 10 to be applied can be miniaturized.

In addition, since all of the surface-adhesive power switches Q1 to Q6 of the self-excited synchronous rectification line 103 are directly adhered to the soldering surface 101b of the printed circuit board 101, instead of using a plug-in package (DIP) as conventionally. The component type is disposed on the element surface 101a of the printed circuit board 101. In addition, if a large-scale layout metal is independently planned on the soldering surface 101b of the printed circuit board 101 as the heat dissipation region of the surface-adhesive power switches Q1 to Q6, the accumulated heat of the high-temperature components can be effectively improved. problem. Of course, assuming that the layout metal is also provided on the component surface 101a of the printed circuit board 101, it can pass through the via to be in the printed circuit. Another large-scale layout metal is independently planned on the component surface 101a of the board 101 as a heat dissipation area of the surface-adhesive power switches Q1 to Q6. In this way, the problem of accumulated heat accumulated by the high-temperature elements can be more effectively improved.

In summary, the self-excited synchronous rectification line provided in the power converter can operate on its own without additional control-related peripheral lines. In this way, the self-excited synchronous rectification circuit provided in the power converter can not only improve the overall efficiency of the power converter, but also reduce the cost of the power converter. In addition, all of the power switches associated with the self-excited synchronous rectification line are modified to be surface-bonded components and adhere directly to the soldering surface of the printed circuit board. In this way, the board volume of the power converter to be applied can be miniaturized, and the problem of accumulated heat accumulated by the high-temperature components can also be improved.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and any person having ordinary knowledge in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of protection of this creation is subject to the definition of the scope of the patent application attached. In addition, any embodiment or application of the present invention is not required to achieve all of the objects or advantages or features disclosed in the present disclosure. In addition, the abstract sections and headings are only used to assist in the search for patent documents and are not intended to limit the scope of the invention.

10‧‧‧Power Converter

101‧‧‧Printed circuit board

101a‧‧‧Component surface of printed circuit board

101b‧‧‧Welded surface of printed circuit board

103‧‧‧Self-excited synchronous rectification line

301‧‧‧ input level

303-1~303-3‧‧‧Output level

305-1~305-3‧‧‧Clamp line

T‧‧‧Transformer

Primary side of NP‧‧‧ transformer

Secondary side of NS1~NS3‧‧‧ transformer

Q1~Q6‧‧‧ surface adhesive power switch

Q7~Q9‧‧‧Power switch

ZD1~ZD4‧‧‧Zina diode

D1‧‧‧ diode

C1‧‧‧ capacitor

LO‧‧‧Output inductor

CO‧‧‧ output capacitor

V1~V3‧‧‧ power supply

VIN‧‧‧ input voltage

CS1, CS2‧‧‧ control signals

The following drawings are part of the specification of the present invention, illustrating an exemplary embodiment of the present invention, which is illustrated with the description of the specification. The principle of this creation.

FIG. 1 is a schematic diagram of a power converter according to an exemplary embodiment of the present invention.

2A is a schematic view showing the component surface of the printed circuit board of FIG. 1.

2B is a schematic view showing a soldering surface of the printed circuit board of FIG. 1.

3 is a schematic diagram of a circuit implementation of the power converter of FIG. 1.

4 is a schematic diagram of an output stage based on a forward architecture for an exemplary embodiment of the present invention.

FIG. 5 is a schematic diagram of a single crystal input stage based on a forward architecture according to an exemplary embodiment of the present invention.

FIG. 6 is a schematic diagram of a dual crystal input stage based on a forward architecture according to an exemplary embodiment of the present invention.

101b‧‧‧Welded surface of printed circuit board

103‧‧‧Self-excited synchronous rectification line

Q1~Q6‧‧‧ surface adhesive power switch

Claims (22)

A power converter comprising: a printed circuit board having a component surface and a soldering surface; a transformer disposed on the component surface and having a primary side and a first secondary side; and a self-excited The synchronous rectification circuit includes a plurality of surface-adhesive power switches directly adhered to the soldering surface, wherein a first portion of the surface-adhesive power switches is coupled to the first secondary side. The power converter of claim 1, wherein the first surface of the surface-adhesive power switch comprises: a first surface-adhesive power switch, the first end of which is coupled to the same-side end of the first secondary side The second end is coupled to the first surface of the second secondary side, and the second end is coupled to the first surface. The second end of the adhesive power switch is coupled to a second node. The power converter of claim 2, wherein the transformer further has a second secondary side, and a second portion of the surface-adhesive power switches is coupled to the second secondary side. The power converter of claim 3, wherein the second surface of the surface-adhesive power switch comprises: a third surface-adhesive power switch, the first end of which is coupled to the second a second end of the same name end, and a control end coupled to the first node; and a fourth surface adhesive power switch, the first end of which is coupled to the second secondary side of the different name end, the second end of the coupling The second end of the third surface-adhesive power switch is connected, and the control end is coupled to the second node. The power converter of claim 4, wherein the transformer further has a third secondary side, and a third portion of the surface-adhesive power switches is connected to the third secondary side. The power converter of claim 5, wherein the third surface of the surface-adhesive power switch comprises: a fifth surface-adhesive power switch, the first end of which is coupled to the third secondary side of the same name And a second surface-adhesive power switch, the first end of which is coupled to the different end of the third secondary side, and the second end of which is coupled to the fifth end The second end of the surface-adhesive power switch is coupled to the second node. The power converter of claim 6, wherein the first node is coupled to the different end of the second secondary side, and the second node is coupled to the same end of the first secondary side. . The power converter of claim 7, further comprising: an input stage for receiving an input voltage, wherein the primary side is coupled to the input stage and reacts to at least one control The signal is received and the input voltage from the input stage is received. The power converter of claim 8, wherein the at least one control signal comprises a single control signal. The power converter of claim 9, wherein the input stage is a single crystal input stage, and the single crystal input stage comprises: a seventh power switch, the first end of which is coupled to the same name of the primary side The second end is coupled to a ground potential, and the control end is configured to receive the single control signal, wherein the different side of the primary side is configured to receive the input voltage. The power converter of claim 10, wherein the single control signal is a pulse width modulation signal. The power converter of claim 11, wherein: the second, the fourth and the sixth surface-adhesive power switch and the seventh power switch are only responsive to the enabling of the pulse width modulation signal And synchronously conducting; and the first, the third, and the fifth surface-adhesive power switches are simultaneously turned on only in response to the disable of the pulse width modulation signal. The power converter of claim 8, wherein the at least one control signal comprises a first control signal and a second control signal. number. The power converter of claim 13, wherein the input stage is a twin input stage, and the dual input stage comprises: a seventh and an eighth power switch, the first end is for receiving The second end of the input voltage is coupled to the different end of the primary side and the end of the same name, and the control end receives the first and second control signals respectively. The power converter of claim 14, wherein the first and second control signals are respectively a pulse width modulation signal. The power converter of claim 15, wherein: the second, the fourth and the sixth surface-adhesive power switch, and the seventh and the eighth power switch are only responsive to the pulse width adjustment The first and third and the fifth surface-adhesive power switches are simultaneously turned on in response to the disable of the pulse width modulation signal. The power converter of claim 8, further comprising: a first output stage coupled to the first end and the second end of the second surface-adhesive power switch for reacting to the input voltage And generating a first power source by the first turn ratio of the primary side and the first secondary side; a second output stage, and the first surface of the fourth surface adhesive power switch The second end is connected to the second end to generate a second power source in response to the input voltage and a second turn ratio of the primary side and the second secondary side; and a third output stage, The first end of the six-surface adhesive power switch is coupled to the second end for generating a third power source in response to the input voltage and a third turn ratio of the primary side to the third secondary side. The power converter of claim 17, wherein the first to the third output stages are respectively an output stage based on a forward architecture, and each output is based on a forward architecture. The stage includes an output inductor and an output capacitor, and the power converter is a forward power converter. The power converter of claim 7, further comprising: a first clamp line comprising a first pair of back-to-back Zener diodes, and spanning the same name end of the first secondary side Between the different end, the voltage is clamped to the first secondary side; a second clamp line includes a diode and a capacitor connected in series, and is connected to the second Between the same-named end and the different-named end of the secondary side, for clamping the voltage of the second secondary side; and a third clamping line, including a second pair of back-to-back Zener diodes, and bridging The voltage between the same name end and the different name end of the third secondary side is used to clamp the voltage on the third secondary side. A power converter as described in claim 19, wherein The first pair of back-to-back Zener diodes include: a first Zener diode having a cathode coupled to the same end of the first secondary side; and a second Zener diode coupled to the cathode The opposite end of the first secondary side, and the anode thereof is coupled to the anode of the first Zener diode. The power converter of claim 19, wherein: the cathode of the diode is coupled to the opposite end of the second secondary side; and the first end of the capacitor is coupled to the anode of the diode, The second end of the capacitor is coupled to the same end of the second secondary side. The power converter of claim 19, wherein the second pair of back-to-back Zener diodes comprise: a first Zener diode, the cathode of which is coupled to the third end of the same name end And a second Zener diode having a cathode coupled to the opposite end of the third secondary side and an anode coupled to the anode of the first Zener diode.