TWI825998B - Power supply capable of providing over-current protection for dynamic loading - Google Patents

Abstract

A power supply is coupled to a load and includes a rectifier, a transformer, a snubber circuit, a protection circuit, a voltage detecting circuit, and a path control circuit. The rectifier converts AC voltage provided by mains electricity into an input voltage. The transformer converts the input voltage into an output voltage for driving the load. The voltage detecting circuit provides a feedback voltage associated with the output voltage. When the power supply is connected to the mains electricity but the output voltage has not been established, the path control circuit deactivates the protection circuit. When determining that the output voltage has been established according to the feedback voltage, the path control circuit activates t the protection circuit for providing over-current protection.

Description

Power supply that provides over-current protection under dynamic load changes

The present invention relates to a power supply that can provide over-current protection, and in particular, to a power supply that can provide over-current protection under high dynamic load changes.

Different components in computer systems require different operating voltages, so power supplies are commonly used to convert alternating current (AC) indoor power into direct current (DC) through transformation, rectification and filtering to drive different components. components. The power supply under the traditional flyback architecture uses a power switch to control the primary side path of the transformer and a rectifier switch to control the secondary side path of the transformer. When the power switch is turned on, the input electric energy will be converted into magnetic energy and stored in the transformer. At this time, the rectifier switch will be turned off to isolate the output path; when the power switch is turned off, the energy stored in the transformer will be released to the output end through the turned on rectifier switch, and An output capacitor is used to smooth the power output to drive a load device. Power supplies usually use disposable fuses to provide overcurrent protection. When the current exceeds the capacity of the wire, the fuse will melt to cut off the current, thereby preventing components of the load device from being damaged.

When the power supply is coupled to the load device but not connected to the mains power supply, the load device It will operate in DC mode, and the power required for its operation can be supplied by the built-in battery. When the power supply is coupled to the load device and connected to the mains power supply, the load device will operate in the AC mode, and the power required for its operation can be supplied by the output voltage provided by the power supply. When switching from DC mode to AC mode, the high dynamic load change of the load device will cause an instant huge surge current in the power supply, causing its fuse to blow out, causing the power supply to be permanently damaged and unable to operate. Therefore, there is a need for a power supply that can provide over-current protection under dynamic load changes.

The invention provides a power supply that provides overcurrent protection under dynamic load changes, which includes a first input terminal, a second input terminal, a first output terminal, a second output terminal, a rectifier, a transformer, A switch, a buffer circuit, a protection circuit, a voltage detection circuit, a path control circuit and a control circuit. The first input terminal and the second input terminal are used to receive an AC voltage provided by a mains supply terminal, and the first output terminal and the second output terminal are coupled to a load device for outputting an output voltage to drive the load device. The rectifier is used to convert AC voltage into an input voltage. The transformer is used to induce energy of the input voltage from a primary side to a secondary side to supply the output voltage. It includes a primary side winding and a secondary side winding, wherein the primary side winding is disposed on the primary side and includes a A first dotted end and a second non-dotted end, and the secondary side winding is disposed on the secondary side and includes a second dotted end and a second non-dotted end. The first end of the switch is coupled to the first non-dominating end of the primary side winding of the transformer, the second end is coupled to a ground potential, and the control end is used to receive a first energy potential and a first A first control signal for switching between a disabling potential. The buffer circuit is coupled between the first input terminal and the rectifier and is used to buffer the influence of a surge current. This protection circuit is used to provide on the primary side Current protection. The voltage detection circuit is disposed on the secondary side and used to provide a feedback voltage related to the output voltage. The path control circuit is used to cut off the loop of the protection circuit after the power supply is coupled to the mains supply end but before the output voltage is established; and when receiving one of the second enabling potentials After the second control signal, the loop of the protection circuit is activated. The control circuit is arranged on the primary side and is used to provide the first control signal through a first pin and adjust the duty cycle of the first control signal according to the value of the feedback voltage; when according to the value of the feedback voltage When it is determined that the output voltage has been established, the second control signal with the second enable potential is output to the path control circuit through a second pin; and the feedback voltage is received through a third pin.

10:Buffer circuit

20: Protection circuit

30:Path control circuit

40: Rectifier

50: Voltage detection circuit

60:Control circuit

100:Power supply

200:Load device

210:Embedded controller

220:Charging integrated circuit

230:Battery

300:Electronic Systems

NP: primary side winding and number of turns

NS: Secondary side winding and number of turns

GND1, GND2: ground potential

TR: Transformer

Q1: Power switch

Q2: Auxiliary switch

C1, C2: energy storage capacitor

CX: capacitor

DO, DX1-DX2, D1-D4: Diode

RD1, RD2: voltage dividing resistor

R1-R3: Resistor

LM: magnetizing inductor

V _IN :Input voltage

V _OUT :Output voltage

V _AC : AC voltage

V _FB :Feedback voltage

Vx: detection voltage

V _BAT : battery voltage

I _IN :Input current

I _OUT : output current

GD1, GD2: control signal

VL: logic signal

PLUG1, PLUG2: Connector

JACK1, JACK2: socket

PD1, PD2: power pins

G1, G2: Ground pins

T1, T2: Detection pins

L1, L2: Live pins

N1, N2: Neutral pin position

P1-P6: Pin position

Figure 1 is a functional block diagram of an electronic system according to an embodiment of the present invention.

Figure 2 is a functional block diagram of an electronic system according to an embodiment of the present invention.

Figure 3 is a functional block diagram of a power supply in an electronic system according to an embodiment of the present invention.

Figure 4 is a schematic diagram of the implementation of the power supply in the electronic system according to the embodiment of the present invention.

Figures 1 and 2 are functional block diagrams of an electronic system 300 in an embodiment of the present invention. The electronic system 300 includes a power supply 100 and a load device 200 . The power supply 100 can be coupled to the load device 200 through a transmission interface to perform data transmission or power delivery. In the embodiments shown in Figures 1 and 2, the power supply 100 can be coupled to a socket JACK1 on the load device 200 through a connector PLUG1, where the connector PLUG1 includes a power pin PD1 and a ground pin. G1 and a detection pin T1, and the socket JACK1 includes a power pin PD2, a ground pin G2 and a detection pin T2. However, the implementation of the transmission interface between the power supply 100 and the load device 200 does not limit the scope of the present invention.

The load device 200 includes an embedded controller (EC) 210, a charger IC (charger IC) 220, and a built-in battery 230. The embedded controller 210 is used to control peripheral devices and Advanced Configuration and Power Interface (ACPI), and is used with hardware to detect motherboard temperature, fan speed, output voltage V _OUT of the power supply 100, etc. Information can effectively distribute power to system components and provide appropriate operating frequencies to achieve the goals of both power saving and efficiency. The charging integrated circuit 220 can manage the power supply of the load device 200 and the built-in power supply according to the output voltage V _OUT provided by the power supply 100 , the system voltage required for the operation of the load device 200 , and the voltage V _BAT provided by the built-in battery 230 . Battery 230 charged.

In the embodiment shown in Figure 1, the power supply 100 is not connected to the mains power. At this time, the load device 200 will operate in the DC mode, and the power required for its operation can be provided by the voltage V _BAT provided by the built-in battery 230. supply.

In the embodiment shown in FIG. 2 , the power supply 100 can be connected to a mains power supply terminal through a transmission interface to receive the AC voltage V _AC supplied by the mains power. The mains power supply end may include a socket JACK2, and the power supply 100 may be connected to the socket JACK2 through a connector PLUG2. The socket JACK2 includes a live pin L1 and a neutral pin N1, and the connector PLUG2 includes a live pin L2 and a neutral pin. Neutral pin N2. However, the implementation of the transmission interface between the power supply 100 and the mains power supply does not limit the scope of the present invention.

The power supply 100 can convert the AC voltage V _AC provided by the mains supply end into an output voltage V _OUT , and then transmit the output voltage V _OUT to the power pin PD2 of the socket JACK1 through the power pin PD1 of the connector PLUG1. At this time, the load device 200 will operate in the AC mode, and the power required for its operation can be supplied by the output voltage V _OUT provided by the power supply 100 .

Figure 3 is a functional block diagram of the power supply 100 in the embodiment of the present invention. The power supply 100 includes a power switch Q1, energy storage capacitors C1 and C2, an output diode DO, a magnetizing inductor LM, a transformer TR, a buffer circuit 10, a protection circuit 20, a path control circuit 30, a Rectifier 40, a voltage detection circuit 50, and a control circuit 60. The power switch Q1, energy storage capacitor C1, magnetizing inductor LM, snubber circuit 10, protection circuit 20, path control circuit 30, rectifier 40 and control circuit 60 are arranged on the primary side of the transformer TR, while the energy storage capacitor C2, The output diode DO and the voltage detection circuit 50 are arranged on the secondary side of the transformer TR.

The power supply circuit 100 can convert the AC voltage V _AC supplied by the commercial power into the output voltage V _OUT to drive the load device 200 . The buffer circuit 10 can suppress high-frequency oscillations caused by surge currents or voltage surges to prevent component damage. The protection circuit 20 is a disposable component used to protect the internal circuit of the load device 200. When a fault or abnormality occurs in the power supply circuit 100 and the current abnormally increases to a certain extent, the protection circuit 20 will melt itself to cut off the abnormal current. This is to prevent the internal components of the load device 200 from being damaged. When the power supply circuit 100 is first connected to the mains, the path control circuit 30 will be cut off to cut off the path of the energy of the AC voltage V _AC transmitted to the rectifier 40 through the protection circuit 20 to prevent the protection circuit from being damaged by the instantaneous high surge current. 20 melt. After receiving a control signal GD2 with an enabling potential, the path control circuit 30 will be turned on, so that the energy of the AC voltage V _AC can be transmitted to the rectifier 40 through the protection circuit 20 and the buffer circuit at the same time. At this time, the protection circuit 20 can provide Over current protection. The voltage detection circuit 50 can detect the state of the output voltage V _OUT and provide a corresponding feedback signal V _FB accordingly. The first control circuit 60 will provide a control signal GD1 based on the feedback signal V _FB so that the power switch Q1 can perform high-frequency switching between the on and off states, thereby periodically sensing the primary side energy of the transformer TR to the secondary stage side to provide the output voltage V _OUT .

Figure 4 is a schematic diagram of the implementation of the power supply 100 according to the embodiment of the present invention. In the embodiment of the present invention, the control circuit 60 may be a pulse width modulation (PWM) integrated circuit, which includes pins P1-P6. The control circuit 60 can output the control signal GD1 for switching between the enable potential and the disable potential in a specific duty cycle to the power switch Q1 through the pin P1, and output the control signal GD2 to the path control circuit 30 through the pin P2. , receives the feedback voltage V _FB provided by the voltage detection circuit 50 through the pin P3, receives a detection voltage Vx provided by the path control circuit 30 through the pins P4 and P5, and outputs a logic signal VL through the pin P6 To the detection pin T1 of connector PLUG2. In the present invention, the control circuit 60 can provide the control signals GD1 and GD2 according to the feedback voltage V _FB of the relevant output voltage V _OUT , and provide the logic signal VL according to the detection voltage Vx. The details of its operation will be discussed later in the description. There are detailed instructions. However, the implementation of the control circuit 60 does not limit the scope of the present invention.

In the embodiment of the present invention, the buffer circuit 10 includes a capacitor CX, a resistor R1, and diodes DX1 and DX2. The first end of the capacitor CX is coupled to the live pin L2 of the connector PLUG2, and the second end is coupled to the resistor R1. The first terminal of the resistor R1 is coupled to the second terminal of the capacitor CX, and the second terminal is coupled to the diodes DX1 and DX2. The anode of the diode DX1 is coupled to the second terminal of the resistor R1 and the cathode is coupled to the rectifier 40 . The anode of the diode DX2 is coupled to the rectifier 40 and the cathode is coupled to the second terminal of the resistor R1. Capacitor CX, resistor R1 and diode DX1 form a resistor-capacitor-diode buffer (RCD snubber), which can suppress high-frequency oscillations caused by spring current or voltage surges during the positive period of AC voltage V _AC . Capacitor CX, resistor R1 and diode DX2 form another resistor-capacitor-diode buffer, which can suppress high-frequency oscillations caused by inrush current or voltage surges during the negative cycle of AC voltage V _AC . However, the implementation of the buffer circuit 10 does not limit the scope of the present invention.

In the embodiment of the present invention, the protection circuit 20 may include a fuse, which is usually made of a low melting point wire or sheet material. When the input current I _IN is too large, the fuse will generate high temperature and melt, resulting in an open circuit and interrupting the input current I _IN to prevent the internal components of the load device 200 from being damaged. However, the implementation of the protection circuit 20 does not limit the scope of the present invention.

In the embodiment of the present invention, the path control circuit 30 includes an auxiliary switch Q2 and resistors R2-R3. The first terminal of the auxiliary switch Q2 is coupled to the protection circuit 20, the second terminal is coupled to the resistor R2 and the pin P4 of the control circuit 60, and the control terminal is coupled to the pin P2 of the control circuit 60 through the resistor R3 to receive control. Signal GD2. The first end of the resistor R2 is coupled to the second end of the auxiliary switch Q2 and the pin P4 of the control circuit 60 , and the second end is coupled to the rectifier 40 and the pin P5 of the control circuit 60 . The first terminal of the resistor R3 is coupled to the control terminal of the auxiliary switch Q2, and the second terminal is coupled to the pin P2 of the control circuit 60. The auxiliary switch Q2 will be selectively turned on or off according to the control signal GD2, thereby turning on or off the overcurrent protection function of the protection circuit 20 .

In the embodiment of the present invention, the rectifier 40 may be a bridge rectifier, which includes diodes D1-D4 and is used to convert the AC voltage V _AC supplied by the mains into the input voltage V _IN . However, the implementation of the rectifier 40 does not limit the scope of the present invention.

In the embodiment of the present invention, the voltage detection circuit 50 includes voltage dividing resistors RD1 and RD2. The voltage dividing resistors RD1 and RD2 are connected in series with each other and in parallel with the energy storage capacitor C2. The feedback voltage V _FB of the relevant output voltage V _OUT can be established on the voltage dividing resistor RD2, where V _FB =V _OUT *RD2/(RD1+RD2 ). However, the implementation of the voltage detection circuit 50 does not limit the scope of the present invention.

In the embodiment of the present invention, the transformer TR includes a primary side winding (represented by the number of turns NP) and a primary side winding (represented by the number of turns NS). The primary side winding NP is disposed on the primary side of the transformer TR. The secondary winding NS is set on the secondary side of the transformer TR, I _IN represents the input current flowing through the primary side, and I _OUT represents the output current flowing through the secondary side. The anode of the output diode DO is coupled to the non-junction end of the secondary winding NS in the transformer TR, and the cathode is coupled to the power pin PD1 of the connector PLUG1 (output voltage V _OUT ). The first end of the energy storage capacitor C1 is coupled to the node end of the primary side winding NP in the transformer TR, and the second end is coupled to a ground potential GND1 to store the energy of the relevant input voltage V _IN . The first end of the energy storage capacitor C2 is coupled to the cathode of the output diode DO, and the second end is coupled to a ground potential GND2 for storing energy of the relevant output voltage V _OUT . In addition, the node end of the secondary winding NS in the transformer TR is coupled to the ground potential GND2.

When the load device 200 is connected to the power supply 100 but the power supply 100 is not connected to the mains, the load device 200 will operate in the DC mode (powered by the battery). At this time, the power supply 100 does not operate and all switches are in the cut-off state, and the control circuit 60 to close.

After being connected to the mains power supply, the power supply 100 can receive the AC voltage V _AC through the live pin L2 and the neutral pin N2 of the connector PLUG2. Since the initial state of the auxiliary switch Q2 is off, the loop of the protection circuit 20 is open. Assuming that the moment of power-on is within the positive half cycle of the AC voltage V _AC (the live pin L2 is at a positive potential, and the neutral pin N2 is at a negative potential), the energy of the AC voltage V _AC will pass through the live pin L2 and the capacitor CX in sequence. , resistor R1 and diode DX1 are transmitted to the rectifier 40, and then the diodes D1 and D4 in the rectifier 40 are turned on and the diodes D2 and D3 are turned off, and then transmitted back to the neutral pin N2. After the rectifier 40 converts the _{AC voltage V AC} into the input voltage V _IN , the energy of the input voltage V _IN will charge the energy storage capacitor C1 and the magnetizing inductor LM. At this time, the control circuit 60 starts to operate and outputs the control signal GD1 through the pin P1 to cause the power switch Q1 to perform high-frequency switching, so that the magnetizing inductor LM can store and release energy, so that the transformer TR can sense the energy on the primary side to the secondary side. stage side to establish the output voltage V _OUT . At the same time, the voltage detection circuit 50 will transmit the detected feedback voltage V _FB to the pin P3 of the control circuit 60 . When the control circuit 60 determines that the value of the feedback voltage V _FB is greater than a predetermined value, it means that the output voltage V _OUT has been established. At this time, the load device 200 will operate in the AC mode (powered by the output voltage V _OUT ). In this case, the control circuit 60 outputs the control signal GD2 with the enabling potential to the path control circuit 30 through the pin P2 to turn on the auxiliary switch Q2, thereby activating the loop of the protection circuit 20. At this time, the energy of the AC voltage V _AC will not only be transmitted to the rectifier 40 through the live pin L2, capacitor CX, resistor R1 and diode DX1, but also transmitted to the rectifier through the protection circuit 20, the turned-on auxiliary switch Q2 and the resistor R2. 40, which means that the protection circuit 20 starts to operate to provide over-current protection. In addition, the control circuit 60 will adjust the duty cycle of the control signal GD1 according to the feedback voltage V _FB to achieve the effect of stabilizing the output voltage V _OUT . By first disconnecting the loop of the protection circuit 20 at the moment when the mains power is connected, and then starting the loop of the protection circuit 20 until the output voltage V _OUT is established, the present invention can avoid the mains supply end, the power supply 100 and the load device with dynamic load changes. 200 At the moment of connection, the protection circuit 20 was burned due to the huge surge current.

If the power-on moment is within the negative half cycle of the AC voltage V _AC (the live pin L2 is at a negative potential, and the neutral pin N2 is at a positive potential), the energy of the AC voltage V _AC will conduct the rectifier 40 through the neutral pin N2. Diodes D2 and D3 cut off diodes D1 and D4, and then pass back to live pin L2 via diode DX2, resistor R1 and capacitor CX. After the rectifier 40 converts the _{AC voltage V AC} into the input voltage V _IN , the energy of the input voltage V _IN will charge the energy storage capacitor C1 and the magnetizing inductor LM. At this time, the control circuit 60 starts to operate, and outputs the control signal GD1 through the pin P1 to cause the power switch Q1 to perform high-frequency switching, so that the magnetizing inductor LM can store and release energy, so that the transformer TR can induce the energy on the primary side to the secondary side. stage side to establish the output voltage V _OUT . At the same time, the voltage detection circuit 50 will transmit the detected feedback voltage V _FB to the pin P3 of the control circuit 60 . When the control circuit 60 determines that the value of the feedback voltage V _FB is greater than a predetermined value, it means that the output voltage V _OUT has been established. At this time, the load device 200 will operate in the AC mode (powered by the output voltage V _OUT ). In this case, the control circuit 60 outputs the control signal GD2 with the enabling potential to the path control circuit 30 through the pin P2 to turn on the auxiliary switch Q2, thereby activating the loop of the protection circuit 20. At this time, the energy of the AC voltage V _AC will not only be transmitted back to the live pin L2 through the diode D2, diode D3, diode DX2, resistor R1 and capacitor CX, but also through the resistor R2 and the turned-on auxiliary switch Q2 and the protection circuit 20 returns to the live pin L2, which means that the protection circuit 20 starts to operate to provide over-current protection. In addition, the control circuit 60 will adjust the duty cycle of the control signal GD1 according to the feedback voltage V _FB to achieve the effect of stabilizing the output voltage V _OUT . By first disconnecting the loop of the protection circuit 20 when the mains power is connected, and then starting the loop of the protection circuit 20 until the output voltage V _OUT is established, the present invention can avoid the mains supply end, the power supply 100 and the load device of dynamic load change. 200 At the moment when they are connected, the protection circuit 20 is burned out due to the huge surge current.

On the other hand, the control circuit 60 can know the cross-voltage of the relevant resistor R2 and the detection voltage Vx of the voltage polarity through the pins P4 and P5, and accordingly determine the positive and negative cycles of the AC voltage V _AC and whether the protection circuit 20 is activated. Then output the corresponding logic signal VL. Table 1 below shows an example of how the logic signal VL is defined, but does not limit the scope of the present invention.

When the embedded controller 210 of the load device 200 receives the logic signal VL through the detection pin T2 of the socket JACK1, it can know the positive and negative cycles of the AC voltage V _AC and the protection circuit 20 according to the logical definition of the value of the logic signal VL. Is there any action?

In the embodiment of the present invention, the power switch Q1 and the auxiliary switch Q2 may be a metal-oxide-semiconductor field-effect transistor (MOSFET) or a bipolar junction transistor. BJT), or other components with similar functions. For N-type transistors, the enabling potential is high potential and the disabling potential is low; for P-type transistors, the enabling potential is low potential and the disabling potential is high potential. However, the types of power switch Q1 and auxiliary switch Q2 do not limit the scope of the present invention. category.

To sum up, when the power supply is coupled to the load device but not connected to the mains, when the power supply is connected to the mains, the present invention will first disconnect the loop of the protection circuit until the output voltage is established. Activate the loop of the protection circuit to provide over-current protection, thereby preventing the protection circuit from being burned out due to the huge surge current at the moment of power-on, causing the power supply to be permanently damaged and unable to operate. Therefore, the present invention can provide a power supply that can provide over-current protection under highly dynamic load changes. The above are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the patentable scope of the present invention shall fall within the scope of the present invention.

10:Buffer circuit

20: Protection circuit

30:Path control circuit

40: Rectifier

50: Voltage detection circuit

60:Control circuit

100:Power supply

GND1, GND2: ground potential

TR: Transformer

Q1: Power switch

C1, C2: energy storage capacitor

DO: diode

LM: magnetizing inductor

V _OUT :Output voltage

V _AC : AC voltage

V _FB :Feedback voltage

Vx: detection voltage

GD1, GD2: control signal

VL: logic signal

PD1: power pin

G1: Ground pin

T1: Detection pin

L2: Live pin

N2; neutral pin

Claims (10)

A power supply that provides overcurrent protection under dynamic load changes, which includes: a first input terminal and a second input terminal for receiving an AC voltage provided by a mains power supply terminal; a first output terminal and a The second output terminal is coupled to a load device and is used to output an output voltage to drive the load device; a rectifier is used to convert the AC voltage into an input voltage; a transformer is used to convert the energy of the input voltage Induction from a primary side to a secondary side to supply the output voltage includes: a primary side winding disposed on the primary side and including a first dotting end and a first non-dotting end; and a primary side winding, Disposed on the secondary side, it includes a second dotting terminal and a second non-doping end; a first switch includes: a first end coupled to the first non-dominating end of the primary side winding in the transformer. a dot terminal; a second terminal coupled to a first ground potential; and a control terminal for receiving a first control signal for switching between a first enabling potential and a first disabling potential; a A buffer circuit is coupled between the first input terminal and the rectifier to buffer the influence of a surge current; a protection circuit is used to provide overcurrent protection on the primary side; a voltage detection circuit is provided on The secondary side is used to provide a voltage related to the output A feedback voltage; a path control circuit for: cutting off the loop of the protection circuit after the power supply is coupled to the city power supply but before the output voltage is established; and when receiving a signal with a After a second control signal at the second enabling potential, the loop of the protection circuit is activated; and a control circuit is provided on the primary side for: providing the first control signal through a first pin, and based on the The value of the feedback voltage adjusts the duty cycle of the first control signal; when it is determined that the output voltage has been established based on the value of the feedback voltage, a second pin with the second enable potential is output. The second control signal is sent to the path control circuit; and the feedback voltage is received through a third pin. The power supply of claim 1, wherein the buffer circuit includes: a capacitor including: a first terminal coupled to the first input terminal; and a second terminal; a first resistor including : a first terminal coupled to the second terminal of the capacitor; and a second terminal; a first diode including: an anode coupled to the second terminal of the first resistor; and a cathode coupled to the rectifier; and a second diode including: an anode coupled to the rectifier; and a cathode coupled to the second end of the first resistor. The power supply of claim 1, wherein the path control circuit includes: a second switch including: a first terminal coupled to the protection circuit; a second terminal coupled to the rectifier; and A control terminal is coupled to the second pin of the control circuit to receive the second control signal. The power supply as claimed in claim 3, further comprising a third output terminal for outputting a logic signal to the load device, wherein: the path control circuit further comprises a second resistor, the first terminal of which is coupled to to the second terminal of the second switch and a fourth pin of the control circuit, and its second terminal is coupled to the rectifier and a fifth pin of the control circuit; and the control circuit is further used for: A corresponding detection voltage is obtained based on the voltage difference between the fourth pin and the fifth pin; and the logic signal is output based on the value of the detection voltage. The power supply as claimed in claim 4, wherein: The control circuit is further used to: output the logic signal with a first value when the value of the detection voltage is a positive value; output the logic signal with a second value when the value of the detection voltage is a negative value. Logic signal; when the value of the detection voltage cannot be determined, the logic signal with a third value is output; the first value corresponds to a positive half cycle of the AC voltage and the loop of the protection circuit is activated; the second value A loop corresponding to a negative half cycle of the AC voltage and the protection circuit is activated; and the third value corresponds to a loop of the protection circuit being disconnected. The power supply of claim 3, wherein the path control circuit further includes: a third resistor, which includes: a first terminal coupled to the control terminal of the second switch; and a second terminal, Coupled to the second pin of the control circuit. The power supply of claim 1, wherein the voltage detection circuit includes: a first voltage dividing resistor, which includes: a first terminal coupled to the first output terminal; and a second terminal coupled to connected to the third pin of the control circuit; and a second voltage dividing resistor, which includes: a first end coupled to the second end of the first voltage dividing resistor; and a second end coupled to connected to a second ground potential. The power supply as claimed in claim 1, further comprising: a magnetizing inductor, the first end of which is coupled to the first terminal of the primary side winding, and the second end of which is coupled to the first terminal of the primary side winding. the first non-dot terminal; and a first energy storage capacitor, which includes: a first terminal coupled to the first dot terminal of the primary side winding; and a second terminal coupled to the first ground Potential. The power supply as claimed in claim 1, further comprising: an output diode, which includes: an anode coupled to the second non-junction terminal of the secondary side winding; and a cathode coupled to the first output terminal; and a second energy storage capacitor, which includes: a first terminal coupled to the first output terminal; and a second terminal coupled to a second ground potential and the second output end. The power supply as claimed in claim 1, wherein the protection circuit includes a fuse for performing self-fuse to cut off the input current when the value of the input current flowing through the primary side is greater than a predetermined value.

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