阅读说明：本技术 电源供应系统及电源转换器 (Power supply system and power converter ) 是由 陈皇颖 于 2018-07-04 设计创作，主要内容包括：本发明公开了一种电源供应系统及电源转换器,电源供应系统包含多个电源转换器,其中电源转换器的输出端彼此电性耦接。电源转换器包含整流单元、第一升压模块、启动回路、第二升压模块、第一开关及控制单元。控制单元电性耦接整流单元、第一升压模块及第一开关。第二升压模块接收第三电压后,第二升压模块通过第一开关输出第四电压至第一升压模块,当控制单元接收第一电压达预定时间时,控制单元截止第一开关进而停止将第四电压输出至第一升压模块。借此,当电源转换器没有正常工作时可将第一开关截止,从而避免从启动回路抽取电力,导致启动回路承受高压而烧毁。(The invention discloses a power supply system and a power converter. The power converter comprises a rectifying unit, a first boosting module, a starting loop, a second boosting module, a first switch and a control unit. The control unit is electrically coupled with the rectifying unit, the first boosting module and the first switch. After the second boosting module receives the third voltage, the second boosting module outputs a fourth voltage to the first boosting module through the first switch, and when the control unit receives the first voltage for a preset time, the control unit stops the first switch to further stop outputting the fourth voltage to the first boosting module. Therefore, when the power converter does not work normally, the first switch can be cut off, so that the situation that the starting circuit bears high voltage and is burnt out due to the fact that power is extracted from the starting circuit is avoided.)

1. A power supply system, comprising:

a plurality of power converters, wherein respective outputs of the plurality of power converters are electrically coupled to each other, wherein each of the plurality of power converters comprises:

a rectifying unit generating a first voltage;

the first boost module is electrically coupled with the rectifying unit and generates a second voltage according to the first voltage;

the starting circuit is electrically coupled with the first boosting module and provides a third voltage according to the second voltage;

the second boosting module is electrically coupled with the starting loop and generates a fourth voltage according to the third voltage;

a first switch electrically coupled to the first boost module and the second boost module, and selectively conducting the fourth voltage provided by the second boost module to the first boost module; and

the control unit is electrically coupled with the rectifying unit, the first boosting module and the first switch;

after the second boost module receives the third voltage, the boost module outputs the fourth voltage to the first boost module through the first switch, and when the control unit receives the first voltage for a predetermined time, the control unit turns off the first switch, thereby stopping outputting the fourth voltage to the first boost module.

2. The power supply system according to claim 1, wherein the first boost module comprises a first control unit, a first energy storage element and a second switch, the first energy storage element is configured to store power and generate the second voltage, the first control unit is activated according to the fourth voltage, and when the first control unit is activated, the first control unit controls the second switch to enable the first boost module to output the first converted voltage.

3. The power supply system of claim 2, further comprising:

a transformer winding that generates a fifth voltage when the first boost module outputs the first converted voltage;

the second boost module comprises a second control unit, the second control unit is started according to the fifth voltage, and when the second control unit is started, the second boost module is enabled to output a second conversion voltage.

4. The power supply system according to claim 3, wherein when the transformer winding generates the fifth voltage, the fifth voltage is output to the first control unit, and the fifth voltage replaces the fourth voltage to maintain the first control unit to start, so that the first boost module outputs the first converted voltage.

5. The power supply system of claim 2, wherein the start-up loop comprises a start-up resistor electrically coupled to the first energy storage element of the first boost module, the first energy storage element converting the second voltage into the third voltage through the start-up resistor and providing the third voltage to the second boost module.

6. The power supply system of claim 5, wherein the second boost module further comprises:

the first unidirectional isolation element is electrically coupled with the transformer winding and the first control unit; and

the second unidirectional isolation element is electrically coupled with the transformer winding and the second control unit;

wherein the first unidirectional isolation element and the second unidirectional isolation element are configured to prevent current from flowing back to the transformer winding.

7. The power supply system of claim 1, wherein the control unit comprises a delay circuit, the delay circuit further comprising:

a first resistor, wherein a first end of the first resistor is electrically coupled to the rectifying unit to receive the first voltage;

a second resistor, wherein a first end of the second resistor is electrically coupled to a second end of the first resistor; and

a second energy storage element, a first end of the second energy storage element being coupled to the first end of the second resistor, a second end of the second energy storage element being coupled to a second end of the second resistor;

when the first resistor receives the first voltage for the preset time, the first end of the second energy storage element is charged to a high potential to turn off the first switch.

8. A power converter, comprising:

a rectifying unit for generating a first voltage;

the first boost module is electrically coupled with the rectifying unit and generates a second voltage according to the first voltage;

the starting circuit is electrically coupled with the first boosting module and provides a third voltage according to the second voltage;

the second boosting module is electrically coupled with the starting loop and generates a fourth voltage according to the third voltage;

a first switch electrically coupled to the first boost module and the second boost module, and selectively conducting the fourth voltage provided by the second boost module to the first boost module; and

the control unit is electrically coupled with the rectifying unit, the first boosting module and the first switch;

after the second boost module receives the third voltage, the boost module outputs the fourth voltage to the first boost module through the first switch, and when the control unit receives the first voltage for a predetermined time, the control unit turns off the first switch, thereby stopping outputting the fourth voltage to the first boost module.

9. The power converter according to claim 8, wherein the first boost module comprises a first control unit and a second switch, the first control unit is activated according to the fourth voltage, and when the first control unit is activated, the first control unit controls the second switch to enable the first boost module to output the first converted voltage.

10. The power converter of claim 9, further comprising:

a transformer winding that generates a fifth voltage when the first boost module outputs the first converted voltage;

the second boost module comprises a second control unit, the second control unit is started according to the fifth voltage, when the second control unit is started, the second boost module outputs a second conversion voltage, when the transformer winding generates the fifth voltage, the fifth voltage is output to the first control unit, and the fifth voltage replaces the fourth voltage to maintain the first control unit to be started, so that the first boost module outputs the first conversion voltage.

Technical Field

The present invention relates to a power supply system and a power converter, and more particularly, to a power supply system and a power converter with protection function.

Background

In the prior art, a power supply system includes a plurality of power converters that can be connected in different ways to supply power to a load. However, since the output voltage of the power supply has an error of 5%, the power converter in the power supply system often has uneven power supply, which causes the output power of some power converters to be abnormal.

When the output power of the power converter is abnormal, the voltage may be fed back by the load through the output terminal of the power converter, which may cause the feedback detection of the internal design of the power converter to be abnormal, and cause the control chip (such as the microprocessor and the central processing unit) or the functional module (such as the boost module) to stop operating. At this time, the start-up loop of the power converter is subjected to a high voltage due to the constant attempt to start up the control chip, so that the components (such as the resistor) of the start-up loop are burned out due to the failure to withstand the high voltage.

Disclosure of Invention

The present invention provides a power supply system, which can turn off a first switch when a power converter does not work normally, so as to avoid the power extraction from a starting circuit, which is burnt out due to the high voltage of the starting circuit.

One aspect of the present invention is a power supply system. The power supply system comprises a plurality of power converters, wherein respective output ends of the power converters are electrically coupled with each other, and the power converters respectively comprise a rectifying unit, a first boosting module, a starting loop, a second boosting module, a first switch and a control unit. The rectifying unit generates a first voltage. The first boost module is electrically coupled to the rectifying unit and generates a second voltage according to the first voltage. The starting circuit is electrically coupled to the first boosting module and provides a third voltage according to the second voltage. The second boost module is electrically coupled to the start-up loop and generates a fourth voltage according to the third voltage. The first switch is electrically coupled to the first boost module and the second boost module, and selectively conducts the fourth voltage provided by the second boost module to the first boost module. The control unit is electrically coupled with the rectifying unit, the first boosting module and the first switch. After the second boosting module receives the third voltage, the second boosting module outputs a fourth voltage to the first boosting module through the first switch, and when the control unit receives the first voltage for a preset time, the control unit stops the first switch to further stop outputting the fourth voltage to the first boosting module.

In an embodiment, the first voltage boost module includes a first control unit, a first energy storage element and a second switch, the first energy storage element is used for storing electric power and generating a second voltage, the first control unit is started according to the fourth voltage, and when the first control unit is started, the first control unit controls the second switch to enable the first voltage boost module to output the first conversion voltage.

In one embodiment, the power supply system further includes a transformer winding, and the transformer winding generates a fifth voltage when the first boost module outputs the first converted voltage. The second boost module comprises a second control unit, the second control unit is started according to the fifth voltage, and when the second control unit is started, the second boost module outputs a second conversion voltage.

In an embodiment, when the transformer winding generates the fifth voltage, the fifth voltage is output to the first control unit, and the fifth voltage replaces the fourth voltage to maintain the first control unit to start, so that the first boost module outputs the first conversion voltage.

In an embodiment, the start-up circuit includes a start-up resistor electrically coupled to the first energy storage element of the first boost module, and the first energy storage element converts the second voltage into a third voltage through the start-up resistor and provides the third voltage to the second boost module.

In an embodiment, the second boost module further includes a first unidirectional isolation element and a second unidirectional isolation element. The first unidirectional isolation element is electrically coupled with the transformer winding and the first control unit. The second unidirectional isolation element is electrically coupled with the transformer winding and the second control unit. The first unidirectional isolation element and the second unidirectional isolation element are used for preventing current from flowing back to the transformer winding.

In one embodiment, the control unit includes a delay circuit, and the delay circuit further includes a first resistor, a second resistor, and a second energy storage element. The first end of the first resistor is electrically coupled to the rectifying unit to receive the first voltage. The first end of the second resistor is electrically coupled to the second end of the first resistor. The first end of the second energy storage element is coupled to the first end of the second resistor, and the second end of the second energy storage element is coupled to a second end of the second resistor. When the first resistor receives the first voltage for a preset time, the first end of the second energy storage element is charged to a high potential to turn off the first switch.

Another aspect of the invention is a power converter. The power converter comprises a rectifying unit, a first boosting module, a starting loop, a second boosting module, a first switch and a control unit. The rectifying unit generates a first voltage. The first boost module is electrically coupled to the rectifying unit and generates a second voltage according to the first voltage. The starting circuit is electrically coupled with the first boosting module and provides a third voltage according to the second voltage. The second boost module is electrically coupled to the start-up loop and generates a fourth voltage according to the third voltage. The first switch is electrically coupled to the first boost module and the second boost module, and selectively conducts the fourth voltage provided by the second boost module to the first boost module. The control unit is electrically coupled with the rectifying unit, the first boosting module and the first switch. After the second boosting module receives the third voltage, the second boosting module outputs a fourth voltage to the first boosting module through the first switch, and when the control unit receives the first voltage for a preset time, the control unit stops the first switch to further stop outputting the fourth voltage to the first boosting module.

In an embodiment, the first boost module includes a first control unit and a second switch, the first control unit is activated according to the fourth voltage, and when the first control unit is activated, the first control unit controls the second switch to enable the first boost module to output the first conversion voltage.

In one embodiment, the power converter further includes a transformer winding, and the transformer winding generates a fifth voltage when the first boost module outputs the first converted voltage. The second boost module comprises a second control unit, the second control unit is started according to a fifth voltage, when the second control unit is started, the second boost module outputs a second conversion voltage, when the transformer winding generates the fifth voltage, the fifth voltage is output to the first control unit, and the fifth voltage replaces a fourth voltage to maintain the first control unit to be started, so that the first boost module outputs the first conversion voltage.

In summary, the power supply system and the power converter of the invention can be configured in different high-wattage systems according to actual requirements, and when the first boost module and the second boost module stop working, the connection is interrupted due to the turn-off of the first switch, so that the start-up circuit cannot continue to start up the boost module, thereby protecting the elements of the start-up circuit.

Drawings

FIG. 1 is a schematic diagram of a power supply system.

Fig. 2 is a functional block diagram of a power converter according to an embodiment of the invention.

Fig. 3 is a circuit diagram of a power converter according to an embodiment of the invention.

Fig. 4 is a schematic diagram illustrating a start-up path of a power converter according to an embodiment of the invention.

Fig. 5 is a schematic diagram illustrating a path of a power converter after startup according to an embodiment of the invention.

Fig. 6 is a schematic diagram illustrating a protection path for an output abnormality of a power converter according to an embodiment of the invention.

Detailed Description

The following detailed description of the embodiments in conjunction with the accompanying drawings is provided to better understand the aspects of the present invention, but the embodiments are not intended to limit the scope of the invention, and the description of the structural operations is not intended to limit the order of execution thereof, any structure resulting from a rearrangement of elements to produce a device with equivalent efficacy is within the scope of the invention. Moreover, the drawings are for illustrative purposes only and are not drawn to scale in accordance with industry standard and conventional practice, and the dimensions of the various features may be arbitrarily increased or decreased for clarity of illustration. In the following description, the same elements will be described with the same reference numerals for ease of understanding.

Fig. 1 is a block diagram of a power supply system 100 according to some embodiments of the invention, in which the power supply system 100 includes a plurality of power converters 110, wherein output terminals of the power converters 110 are coupled to each other and output power to a load 300 at the same time. When the input power required for the load operation reaches the maximum rated value, the power converter 110 outputs the power at the rated maximum power to the load 300. Because in the power supply system 100, each power converter 110 has its own maximum output rating, each power converter 110 outputs its own maximum rated power value to the load 300.

The power supply system 100 is used to supply power to the load 300 because the output voltage supplied by the power converter 110 has a tolerance of ± 5% in the general design. In general applications, the power converter 110 includes a starter, a boost module, and the like. The functional modules such as the boost module further include a control chip (e.g., a central processing unit, a microprocessor, or a power supply integrated circuit). Because the output voltages of the power converters 110 in the power supply system 100 are not necessarily the same due to the design error, there may be a lower limit (e.g., biased to-5%) of the output voltages of one part of the power converters 110 and a higher limit (e.g., biased to + 5%) of the output voltages of another part of the power converters 110, such that the output terminals of the load 300 (e.g., from the other power converters 110 with higher limits of the output voltages) will sink the voltage to the power converter 110 with lower limit of the output voltage, and the control chip of the internal functional module (e.g., the boost module) of the power converter 110 with lower limit of the output voltage cannot work normally. The starting device in the power converter 110 is used to transmit power to start the control chip in the boost module. When the control chip of the power converter 110 does not work normally, the control chip will continuously draw power through the starting device, causing the starting device to be subjected to high voltage and burned. The following description will continue to describe the start-up device in the protection power converter 110 according to the present invention.

FIG. 2 is a functional block diagram of one of the power converters 110 of the power supply system 100 of FIG. 1 according to the present invention. The power supply system 100 includes a plurality of power converters 110. The respective output terminals of the power converters 110 are electrically coupled to each other, and each of the power converters 110 includes a rectifying unit 111, a first boost module 112, a start-up loop 113, a second boost module 114, a second control unit 114a, a voltage converting circuit 114b, a first switch 115, a control unit 116, and a transformer winding 117.

Fig. 3 is a circuit diagram of one of the power converters 110 in the power supply system 100 of fig. 2 according to the present invention. As shown in fig. 3, the rectifying unit 111 can be any rectifier capable of converting the ac power source 200 into dc power, such as a half-wave rectifier, a full-wave rectifier, a half-bridge rectifier, a full-bridge rectifier, or other relevant combinations. Wherein the rectifying unit 111 converts an input of the ac power source 200 to generate the first voltage V1. After the first voltage V1 generated by the rectifying unit 111 passes through the first boosting module 112, the first energy storage element 112c can be charged.

In general, as shown in fig. 3, the first energy storage element 112c and the second energy storage element 116c may be elements or components having charging and discharging functions. The present invention is illustrated by a capacitor, but not limited thereto.

In some embodiments, as shown in fig. 3, the control unit 116 is coupled to the rectifying unit 111. The control unit 116 receives the first voltage V1 output by the rectifying unit 111 for a period of time, and controls the first switch 115 to be selectively turned on or off according to the first voltage V1.

Referring to fig. 3, the control unit 116 includes a delay circuit. The delay circuit in the control unit 116 is composed of a first resistor 116a, a second resistor 116b and a second energy storage element 116 c. The first end of the first resistor 116a is electrically coupled to the rectifying unit 111 and receives the first voltage V1. The first terminal of the second resistor 116b is electrically coupled to the second terminal of the first resistor 116 a. A first terminal of the second energy storage element 116c is coupled to a first terminal of the second resistor 116b, and a second terminal of the second energy storage element 116c is coupled to a second terminal of the second resistor 116 b. When the first resistor 116a receives the first voltage V1, the second energy storage element 116c is charged. When the first resistor 116a receives the first voltage V1 for a predetermined time, the first terminal of the second energy storage element 116c is charged from a low potential to a high potential, so that the gate of the first switch 115 is at a high potential.

In general applications, the first switch 115 may be a power semiconductor such as a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or a Bipolar Junction Transistor (BJT). The present invention is exemplified by a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), but not limited thereto.

Referring to fig. 3, a gate of the first switch 115 is coupled to the control unit 116. The source of the first switch 115 is coupled to the transformer winding 117. In this embodiment, the first switch 115 may be a P-type power semiconductor (e.g., a P-type MOSFET), i.e., a low-voltage conducting switch device, but not limited thereto. When the gate voltage of the first switch 115 is less than the threshold voltage (Vth), the first switch 115 is turned on. On the contrary, when the gate voltage of the first switch 115 is greater than the threshold voltage (Vth), the first switch 115 is turned off.

Referring to fig. 2 and 3, the first boost module 112 is coupled to the rectifying unit 111. The first boost module 112 includes a first control unit 112a, a second switch 112b and a first energy storage element 112 c. If the first control unit 112a is activated, the first control unit 112a may control the second switch 112b to switch the switch state of the second switch 112b, so that the first boost module 112 outputs the first conversion voltage U1.

On the contrary, if the first control unit 112a is not activated, the first control unit 112a will not switch the second switch 112b, and at this time, the first boost module 112 will not generate the first conversion voltage U1. Referring to fig. 4, fig. 4 is a flowchart illustrating a start-up process of the power converter 110 shown in fig. 3 according to the present invention. As shown in fig. 3 and 4, in the starting process of the power converter 110, the first control unit 112a is not yet started in the initial state, so the first control unit 112a does not yet switch the second switch 112 b. After the first voltage V1 of the rectifying unit 111 is filtered by the first voltage boosting module 112, the first voltage V1 charges the first energy storage element 112c, and the first energy storage element 112c generates the second voltage V2. The second voltage V2 generated by the first boost module 112 is output to the start-up loop 113.

As shown in fig. 3 and 4, the start-up circuit 113 includes a start-up resistor 113 a. The first energy storage element 112c is coupled to the starting resistor 113 a. After the first energy storage element 112c is charged for a period of time, the first energy storage element 112c provides the third voltage V3 to the second boost module 114 through the starting resistor 113 a.

As shown in fig. 3 and 4, the second boost module 114 is electrically coupled to the start-up loop 113, and the second boost module 114 includes a second control unit 114a, a voltage conversion circuit 114b, a first unidirectional isolation element 114c, and a second unidirectional isolation element 114 d. The second control unit 114a generates a fourth voltage V4 according to the third voltage V3. As shown in fig. 3, since the starting resistor 113a is coupled to the second control unit 114a of the second boost module 114, the second control unit 114a is configured to receive the third voltage V3. As shown in fig. 4, when the third voltage V3 activates the second control unit 114a, the second control unit 114a transmits the fourth voltage V4 to the first switch 115.

As shown in fig. 2 and 3, the first switch 115 is electrically coupled between the first boost module 112 and the second boost module 114, and is used for selectively conducting the fourth voltage V4 provided by the second boost module 114 to the first boost module 112. The first switch 115 selectively turns on or off and thereby transmits the fourth voltage V4 or turns off the transmission of the fourth voltage V4.

As shown in fig. 3, before the second boost module 114 is activated, the gate voltage of the first switch 115 is coupled to the ground through the second resistor 116b and the second energy storage element 116c, and the second energy storage element 116c is not yet charged to the high potential, so the gate voltage of the first switch 115 is lower than the threshold voltage (Vth), and thus the first switch 115 is in the on state.

When the second control unit 114a is just started and outputs the fourth voltage V4, the first switch 115 is turned on because the second energy storage element 116c is not yet charged to the high level. As shown in fig. 4, when the first switch 115 is turned on, the first switch 115 provides the first boosting module 112 with the fourth voltage V4 output from the second control unit 114 a.

As shown in fig. 2 and 3, since the first control unit 112a of the first boost module 112 is coupled to the first switch 115, after the first control unit 112a receives the fourth voltage V4 through the first switch 115, the first control unit 112a is activated. The first control unit 112a starts controlling the second switch 112b such that the first boost module 112 outputs the first conversion voltage U1.

FIG. 5 is a flowchart illustrating the power converter 110 in FIG. 3 after being started according to the present invention. Referring to fig. 3 and 5, when the first boost module 112 outputs the first conversion voltage U1 to the second boost module 114, the transformer winding 117 generates the fifth voltage V5.

As shown in fig. 3 and 5, when the fifth voltage V5 is generated by the transformer winding 117, the first resistor 116a in the control unit 116 receives the first voltage V1 and charges the second energy storage element 116c for a predetermined time, and the second energy storage element 116c is charged to a high potential, so that the gate voltage of the first switch 115 is higher than the threshold voltage (Vth), and therefore the first switch 115 is turned off. At this time, the second control unit 114a cannot transmit the fourth voltage V4 to the first boost module 112 through the first switch 115.

In the present invention, the voltage converting circuit 114b includes a transformer winding 117 as an example, but not limited thereto. Furthermore, in the present invention, the transformer winding 117 may be an isolated transformer or other transformer with windings.

As shown in fig. 3, the second boost module 114 further includes a first unidirectional isolation element 114c and a second unidirectional isolation element 114 d. The first unidirectional isolation element 114c is electrically coupled to the transformer winding 117 and the first control unit 112 a. The second unidirectional isolation element 114d is electrically coupled to the transformer winding 117 and the second control unit 114 a. The first unidirectional isolation element 114c and the second unidirectional isolation element 114d are used to prevent the current from flowing back to the transformer winding. Since the current cannot flow back to the transformer winding 117 and the first switch 115 is turned off, so that the second control unit 114a is completely isolated from the first control unit 112a, the fourth voltage V4 cannot be transmitted from the second control unit 114a to the first control unit 112a through the transformer winding loop or the first switch 115.

As shown in fig. 3 and 5, when the first switch 115 is turned off, the transformer winding 117 transmits a fifth voltage V5 to the first control unit 112a through the first unidirectional isolation element 114c and the third unidirectional isolation element 118. And the fifth voltage V5 replaces the fourth voltage V4 to maintain the first control unit 112a activated, so that the first boost module 112 continuously outputs the first converted voltage U1.

As shown in fig. 3 and 5, the transformer winding 117 transmits a fifth voltage V5 to the second control unit 114a through the first unidirectional isolation element 114c and the second unidirectional isolation element 114 d. The second control unit 114a is activated according to the fifth voltage V5, and when the second control unit 114a is activated, starts to control the voltage conversion circuit 114b such that the second boost module 114 outputs the second converted voltage U2 to the load 300.

As shown in fig. 3 and 5, when the fifth voltage V5 output from the transformer winding 117 is simultaneously supplied to the first control unit 112a and the second control unit 114a, the starting resistor 113a stops supplying power to the second control unit 114 a.

As shown in fig. 1, when an output voltage of one of the power converters 110 is abnormal, because the terminal voltage of the load 300 is higher than the output voltage of the power converter 110, the load 300 sinks a voltage to the inside of the power converter 110 through the output terminal of the power converter 110.

FIG. 6 is a flow chart illustrating the protection of the abnormal output of the power converter 110 in FIG. 3 according to the present invention. Referring to fig. 3 and fig. 6, when the output of the voltage converter 110 is abnormal, the fifth voltage V5 of the transformer winding 117 is increased instantaneously due to the reverse sinking voltage U3 of the load 300. The first control unit 112a is turned off because it cannot withstand the fifth voltage V5 increased by the reverse-sink voltage U3.

As shown in fig. 6, when the first control unit 112a is turned off, the first control unit 112a also stops controlling the second switch 112 b. Therefore, the first boost module 112 stops outputting the first conversion voltage U1. Therefore, the first switching voltage U1 gradually decreases.

As shown in fig. 6, when the first converted voltage U1 gradually decreases, the voltage conversion circuit 114b of the second boost module 114 is turned off and gradually stops outputting the second converted voltage U2. At this time, the back-sink voltage U3 is not inputted from the output terminal of the power converter 110 and the second converted voltage U2 is continuously decreased, so the output fifth voltage V5 of the transformer winding 117 starts to gradually decrease until the fifth voltage V5 of the transformer winding 117 is insufficient to start the second control unit 114 a.

As shown in fig. 3 and 6, when the fifth voltage V5 of the transformer winding 117 is insufficient to start the second control unit 114a, the second control unit 114a starts to draw power from the first energy storage element 112c through the starting resistor 113 a.

As shown in fig. 3 and 6, when the second control unit 114a starts to draw power through the starting resistor 113a, the second control unit 114a gradually stops controlling the voltage converting circuit 114b, so that the fifth voltage V5 output by the transformer winding 117 in the voltage converting circuit 114b continues to decrease.

As shown in fig. 3 and fig. 6, during the decreasing process of the fifth voltage V5 of the transformer winding 117, the first switch 115 still exhibits the off-state because the second energy storage element 116c has not discharged to the ground through the second resistor 116b, so that the gate voltage of the first switch 115 is higher than the threshold voltage (Vth). The second control unit 114a is completely isolated from the first control unit 112a, and the fourth voltage V4 cannot be transmitted from the second control unit 114a to the first control unit 112 a.

In summary, the second control unit 114a cannot supply the fourth voltage V4 to the first control unit 112a while the first switch 115 is still in the off state, so that the second control unit 114a can be prevented from continuously drawing power from the first energy storage element 112c through the starting resistor 113 a. The starting resistor 113a does not withstand a high voltage. Therefore, when the power converter 110 outputs an abnormal output to cause the reverse sinking voltage U3 of the load 300, the starting resistor 113a will not be burned due to the high voltage.

When the ac power supply 200 stops supplying power, the first voltage V1 output by the rectifying unit 111 drops to zero, because the second energy storage element 116c continuously discharges to the ground through the second resistor 116b to a low potential, the gate voltage of the first switch 115 is lower than the threshold voltage (Vth), and the first switch 115 is turned on again. The second control unit 114a may transmit the fourth voltage V4 to the first control unit 112a through the first switch 115. At this time, referring to fig. 4, the power converter 110 re-executes the starting process as described above.

Furthermore, the features and circuits in the various figures, embodiments and examples of the invention may be combined with each other without conflict. The circuits shown in the drawings are for illustrative purposes only and are simplified to simplify the explanation and facilitate understanding, but are not intended to limit the present invention.

In addition, those skilled in the art will appreciate that in various embodiments, each circuit unit may be implemented by various types of digital or analog circuits, and may also be implemented by different integrated circuit chips. The various components may also be integrated into a single integrated circuit chip. The foregoing is merely exemplary and the invention is not limited thereto. Electronic components such as resistors, capacitors, diodes, optocouplers, etc. may be formed from any suitable devices. For example, diodes may be implemented with various types of transistors as desired.

Although the present invention has been described with reference to the above 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.