CN111509979B

CN111509979B - Voltage converter

Info

Publication number: CN111509979B
Application number: CN201910097899.6A
Authority: CN
Inventors: 詹子增
Original assignee: Acer Inc
Current assignee: Acer Inc
Priority date: 2019-01-31
Filing date: 2019-01-31
Publication date: 2021-07-30
Anticipated expiration: 2039-01-31
Also published as: CN111509979A

Abstract

The invention provides a voltage converter, which comprises a transformer, a power switch, a first control circuit and a current detection circuit. The transformer includes a primary winding, a secondary winding and an auxiliary winding. The transformer is used to convert an input voltage to an output voltage. The first end of the power switch is connected to the primary side winding, and the second end of the power switch is connected to the first control circuit. The first control circuit is used for generating a first control signal according to the current detection voltage so as to control the operation of the power switch and generating a second control signal. The current detection circuit is connected to the third terminal of the power switch, the first control circuit and the auxiliary winding, and is used for sensing a current detection voltage according to a second control signal to provide the current detection voltage to the first control circuit.

Description

Voltage converter

Technical Field

The present invention relates to a voltage converter, and more particularly, to a voltage converter capable of providing different output voltages.

Background

With the development of technology, the variety of electronic products, such as notebook computers, mobile communication devices, personal assistants, multimedia players, etc., is increasing, and these electronic products all need to use a voltage converter to convert a high-voltage ac power source or dc power source into a stable dc power source meeting the requirement, so as to be used as a power source for charging or operating. Meanwhile, as the hardware specification of electronic products is continuously increased, the demand of the electronic products for power supply is also increasing. For example, a competitive notebook computer developed for video games has a very large demand for power supply. Therefore, it is an objective of the industry to develop a voltage converter that can meet various power supply requirements.

Disclosure of Invention

Therefore, it is a primary object of the present invention to provide a voltage converter with different output voltages.

The invention discloses a voltage converter, comprising: a transformer, including a primary winding, a secondary winding and an auxiliary winding, for converting an input voltage into an output voltage; a power switch, a first end of which is connected to the primary side winding; the first control circuit is connected to a second end of the power switch and used for generating a first control signal according to a current detection voltage so as to control the operation of the power switch and generate a second control signal; and a current detection circuit, connected to a third terminal of the power switch, the first control circuit and the auxiliary winding, for sensing the current detection voltage according to the second control signal to provide the current detection voltage to the first control circuit.

The voltage converter can switch to output different output voltages according to system requirements.

Drawings

Fig. 1 is a schematic diagram of a voltage converter according to an embodiment of the invention.

Fig. 2 is a waveform diagram of related signals of the voltage converter of fig. 1.

Fig. 3 to 5 are schematic equivalent circuits of the voltage converter according to the embodiment of the invention during operation.

1 Voltage converter

10 Transformer

20 first control circuit

202. 204, 206 comparator

208 timer

210 driver

30 current detection circuit

40 second control circuit

50 output voltage switching circuit

502 voltage stabilizer

60 feedback circuit

602 photoelectric coupler

C1-C3, CA and CO capacitors

CS, FB, GD 1-GD 3, SGND and pin

SYSTEM、Vcc、Vdd

DA. DO diode

GND1 first ground

GND2 second ground

ICS Primary side winding current

IN input terminal

NA auxiliary winding

NP primary side winding

Secondary side winding of NS

OUT output terminal

R1-R2, RA, RC 1-RC 2, RS 1-resistor

RS3

Control signals S1-S3

SS system signal

SW1 power switch

Auxiliary switch SW 2-SW 3

VCC, VDD supply voltage

VCS current detection voltage

VGS _ Q1, VGS _ Q2, VGS _ Q3 voltages

VI input voltage

VNA auxiliary winding voltage

Winding voltage of VNP and VNS

VO output voltage

VR 1-VR 3 reference voltages

VRS3 cross pressure

Detailed Description

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. The present specification and claims do not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. Further, the term "coupled" is intended to encompass any direct or indirect electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections.

Referring to fig. 1, fig. 1 is a schematic diagram of a voltage converter 1 according to embodiment 1 of the present invention. The voltage converter 1 is used for providing an output voltage VO to a load. The load may be any electronic product requiring power, and the output voltage VO may be used as a power source for charging or normal operation of the electronic product. The output voltage VO is a first output voltage V1 or a second output voltage V2. For example, the first output voltage value V1 is less than the second output voltage value V2. The power supply device 1 includes a transformer 10, a first control circuit 20, a current detection circuit 30, a second control circuit 40, an output voltage switching circuit 50, a feedback circuit 60, a power switch SW1, a resistor RA, capacitors Co and CA, and diodes DA and DO. The transformer 10 can convert an input voltage VI into an output voltage VO. The transformer 10 includes a primary winding NP, a secondary winding NS and an auxiliary winding NA. The first terminal of the primary winding NP is connected to an input terminal IN for receiving an input voltage VI, and the second terminal of the primary winding NP is connected to the power switch SW 1. A first terminal of the secondary winding NS is connected to the diode DO, and a second terminal of the secondary winding NS is connected to a second ground GND 2. A first terminal of the auxiliary winding NA is connected to the diode DA and a second terminal of the auxiliary winding NA is connected to the first ground GND 1. The anode of the diode DA is connected to the first end of the auxiliary winding NA and the cathode of the diode DA is connected to the resistor RA. A first terminal of the resistor RA is connected to the cathode of the diode DA, and a second terminal of the resistor RA is connected to the power switch SW1 and the current detection circuit 30. The anode of the diode DO is connected to the first end of the secondary winding NS, and the cathode of the diode DO is connected to an output terminal OUT. A first terminal of the capacitor CO is connected to the output terminal OUT, and a second terminal of the capacitor CO is connected to a second ground GND 2.

A first terminal of the power switch SW1 is connected to a second terminal of the primary winding NP. The second terminal of the power switch SW1 is connected to the first control circuit 20 for receiving a control signal S1. The third terminal of the power switch SW1 is connected to the current detection circuit 30. The power switch SW1 can control the signal transmission path between the first terminal and the third terminal to assume a conducting state (short circuit) or a non-conducting state (open circuit) according to the potential of the control signal S1. The power switch SW1 may be a power transistor. For example, the power switch SW1 can be a Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET), a Bipolar Junction Transistor (BJT), or other devices with similar functions, but not limited thereto. When the power switch SW1 is turned on, the primary-side winding current ICS flows through the primary-side winding NP and the power switch SW1, and the primary-side winding NP stores energy. At this time, an output voltage VO is generated by the capacitor CO to supply power to the load. When the power switch SW1 is turned off, the energy stored in the primary winding NP is transferred to the secondary winding NS to supply the capacitor CO.

The first control circuit 20 may be an integrated circuit device. The first control circuit 20 is connected to the power switch SW1, the current detection circuit 30, the feedback circuit 60 and the auxiliary winding NA. The first control circuit 20 includes pins CS, FB, GD1, GD2, SGND, Vcc, and the like. The first control circuit 20 receives a power supply voltage Vcc through a pin Vcc for performing related operations. The first control circuit 20 can receive a current detection voltage VCS via the pin CS and generate control signals S1 and S2 according to the current detection voltage VCS. The first control circuit 20 may output a control signal S1 via the pin GD1 to control the operation of the power switch SW 1. The first control circuit 20 may output a control signal S2 via a pin GD2 to control the operation of the current detection circuit 30. The pin FB of the first control circuit 20 is connected to the output voltage switching circuit 50 through the feedback circuit 60 to detect the output voltage VO of the voltage converter 1, and the first control circuit 20 receives a feedback signal through the pin FB.

The first control circuit 20 includes

comparators

202, 204, 206, a timer 208 and a driver 210. The first input terminal of the comparator 202 is configured to receive the current detection voltage VCS, the second input terminal of the comparator 202 is configured to receive a reference voltage VR1, and an output terminal of the comparator 202 is configured to output a comparison signal. The comparator 202 is used for comparing signals received by the first input terminal and the second input terminal to generate a comparison signal. The comparison signal may be a voltage signal or a current signal, but is not limited thereto. The timer 208 is used to count time. For example, the timer 208 may count for a predetermined time. For example, the timer 208 may generate a time count signal to the comparator 202 every predetermined time. The timer 208 starts counting according to the indication of the comparator 202 and generates a time count signal to the comparator 202 after the predetermined time expires.

In one embodiment, the comparator 202 can compare the signals received by the first input terminal and the second input terminal according to the time count signal generated by the timer 208 to generate the comparison signal. For example, the comparator 202 determines whether the current-detected voltage VCS is greater than the reference voltage VR1 and whether the current-detected voltage VCS is greater than the reference voltage VR1 for a predetermined time according to the time counting operation of the timer 208, thereby generating the comparison signal. The driver 210 is connected to the output terminal of the comparator 202 for receiving the comparison signal and generating a driving signal S2 to the current detecting circuit 30 to control the operation of the current detecting circuit 30. When the comparator 202 determines that the current-sensed voltage VCS is greater than the reference voltage VR1 and the current-sensed voltage VCS is greater than the reference voltage VR1 for a predetermined time period according to the time count of the timer 208, the comparator 202 generates and outputs a comparison signal to the driver 210, and the driver 210 generates a control signal S2 to the auxiliary switch SW2 of the current-sensing circuit 30, such that the auxiliary switch SW2 is switched to an on state corresponding to the control signal S2. When the comparator 202 determines that the current-sensing voltage VCS is less than the reference voltage VR1, the comparator 202 generates and outputs a comparison signal to the driver 210, and the driver 210 generates a control signal S2 to the auxiliary switch SW2 of the current-sensing circuit 30, such that the auxiliary switch SW2 is switched to a non-conductive state in response to the control signal S2.

A first input of the comparator 204 is configured to receive the current detection voltage VCS, and a second input of the comparator 204 is configured to receive a reference voltage VR 2. In one embodiment, when the current detection voltage VCS is greater than the reference voltage VR2, the comparator 204 generates an over-voltage control signal to activate the over-voltage protection function, thereby controlling the first control circuit 20 to switch to the shutdown state. A first input of the comparator 206 is configured to receive the current sense voltage VCS, and a second input of the comparator 206 is configured to receive a reference voltage VR 3. In one embodiment, when the current detection voltage VCS is greater than the reference voltage VR3, the comparator 206 generates the control signal S1 to the pin GD1 to control the power switch SW1 to switch to the non-conductive state. In short, the

comparators

204 and 206 perform an over-voltage protection function according to the reference voltages VR2 and VR3 to limit the operations of the first control circuit 20 and the power switch SW1, so as to protect the voltage converter itself and the electronic products supplied by the voltage converter.

The current detection circuit 30 includes an auxiliary switch SW2 and resistors RC1 and RC 2. A first terminal of the resistor RC1 is connected to the third terminal of the power switch SW1, the second terminal of the resistor RA, a first terminal of the auxiliary switch SW2, and the pin CS of the first control circuit 20. A second terminal of resistor RC1 is connected to first ground GND 1. As shown in fig. 1, the first terminal of the auxiliary winding NA is connected to the third terminal of the power switch SW1 through a diode DA and a resistor RA. The current detection voltage VCS is output to the pin CS of the first control circuit 20 via the first terminal of the resistor RC 1. A first terminal of the auxiliary switch SW2 is connected to the third terminal of the power switch SW1, the second terminal of the resistor RA, and the pin CS of the first control circuit 20, and a second terminal of the auxiliary switch SW2 is connected to the pin GD2 of the first control circuit 20 for receiving the control signal S2. The third terminal of the auxiliary switch SW2 is connected to the resistor RC 2. The auxiliary switch SW2 can control the signal transmission path between the first terminal and the third terminal to assume a conducting state (short circuit) or a non-conducting state (open circuit) according to the potential of the control signal S2. A first terminal of the resistor RC2 is connected to the third terminal of the auxiliary switch SW2, and a second terminal of the resistor RC2 is connected to the first ground GND 1.

The second control circuit 40 may be an integrated circuit device. The second control circuit 40 includes pins GD3, Vdd, and SYSTEM. The second control circuit 40 receives a power voltage Vdd through the pin Vdd and performs related operations accordingly. The second control circuit 40 may receive the SYSTEM signal SS via the pin SYSTEM. The system signal SS is used to instruct the voltage converter 1 to provide the output voltage VO to the first output voltage V1 or the second output voltage V2. The second control circuit 40 generates a control signal S3 according to the system signal SS. The second control circuit 40 can output the control signal S3 to the output voltage switching circuit 50 via the pin GD 3.

The output voltage switching circuit 50 includes a voltage regulator 502, an auxiliary switch SW3, and resistors RS 1-RS 3. A first terminal of the resistor RS1 is connected to the output terminal OUT, and a second terminal of the resistor RS1 is connected to the resistor RS 3. The first terminal of the auxiliary switch SW3 is connected to the output terminal OUT, and the second terminal of the auxiliary switch SW3 is connected to the pin GD3 of the second control circuit 40 for receiving the control signal S3. The third terminal of the auxiliary switch SW3 is connected to the resistor RS 2. The auxiliary switch SW3 can control the signal transmission path between the first terminal and the third terminal to assume a conducting state (short circuit) or a non-conducting state (open circuit) according to the potential of the control signal S3. A first terminal of the resistor RS2 is connected to the third terminal of the auxiliary switch SW3, and a second terminal of the resistor RS2 is connected to the resistor RS 3. A first end of the resistor RS3 is connected to the second end of the resistor RS1, the second end of the resistor RS2, the regulator 502 and the feedback circuit 60, and a second end of the resistor RS3 is connected to the second ground GND 2. The voltage regulator 502 is connected to the first end of the resistor RS3 and the second ground GND2 for controlling a voltage VRS3 of the resistor RS3, such that the voltage VRS3 of the resistor RS3 has a fixed voltage difference. The voltage regulator 502 may be a TL431 voltage regulator chip, but is not limited thereto. In one embodiment, when the system signal SS indicates that the output voltage VO is the first output voltage value V1, the second control circuit 40 accordingly generates the control signal S3 such that the auxiliary switch SW3 is in a non-conductive state corresponding to the control signal S3. When the system signal SS indicates that the output voltage VO is the second output voltage value V2, the second control circuit 40 accordingly generates the control signal S3 such that the auxiliary switch SW3 is switched to the on state corresponding to the control signal S3. In addition, the feedback circuit 60 includes a photo coupler 602, resistors R1-R2, and capacitors C1-C3. The photo coupler 602 may be a PC817 photo coupler, but is not limited thereto.

Referring to fig. 2, fig. 2 is a waveform diagram of related signals of the voltage converter 1 of fig. 1. The voltage VGS _ Q1 is a gate-source voltage of the power switch SW1, the voltage VGS _ Q2 is a gate-source voltage of the auxiliary switch SW2, and the voltage VGS _ Q3 is a gate-source voltage of the auxiliary switch SW 3. In the present embodiment, the voltage converter 1 can provide the output voltage VO as a first output voltage V1 (e.g., 19 volts) or a second output voltage V2 (e.g., 25 volts). First, during the time period T0-T1, the voltage converter 1 is not powered up, the power switch SW1, the auxiliary switch SW2 and the auxiliary switch SW3 are all in the off state (i.e., turned off state), and the output voltage VO is 0.

At time T1, voltage converter 1 powers up. At this time, the power switch SW1, the auxiliary switch SW2, and the auxiliary switch SW3 are still in the non-conducting state, and the winding voltage VNP of the primary winding NP, the winding voltage VNS of the secondary winding NS, and the output voltage VO gradually rise. As shown in fig. 2, the output voltage VO gradually rises during the time T1 to T2. As shown in fig. 3, during the time T1 to T2, the auxiliary switch SW2 is in the non-conductive state, and the resistor RC2 is in the open state. As a result, the total resistance of the load resistor connected between the power switch SW1 and the first ground GND1 is the resistance of the resistor RC 1. Next, since the second control circuit 40 has not yet started operating, the auxiliary switch SW3 is in the non-conductive state and the resistor RS2 is in the open state. In this case, the output voltage dividing resistors of the output voltage switching circuit 50 are the resistor RS1 and the resistor RS 3. The total voltage dividing resistance (i.e. the total resistance from the output terminal OUT to the second ground GND 2) in the output voltage switching circuit 50 is the series resistance of the resistor RS1 and the resistor RS 3. Next, at time T2, the first control circuit 20 starts to operate and the first control circuit 20 outputs the control signal S1 to control the power switch SW1 to switch to the on state. As shown in fig. 2, the output voltage VO continues to rise during the time T2 to T3.

At time T3, power switch SW1 is still in a conductive state. The second control circuit 40 starts to operate and outputs the control signal S3 to control the power switch SW3 to switch to the on state. As shown in fig. 4, since the power switch SW3 is switched to the on state according to the control signal S3, the output voltage dividing resistors of the output voltage switching circuit 50 are the resistor RS1, the resistor RS2 and the resistor RS 3. The total voltage-dividing resistance value (i.e., the total resistance value from the output terminal OUT to the second ground GND 2) in the output voltage switching circuit 50 is an equivalent resistance value formed by connecting the resistor RS1 and the resistor RS2 in parallel and then connecting the resistor RS3 in series. The parallel resistance of the resistor RS1 and the resistor RS2 is smaller than that of the resistor RS 1. As shown in fig. 2, during the time T3 to T4, the output voltage VO continues to rise, and the power switch SW1 continues to be maintained in the on state. For example, the voltage across VRS3 via control resistor RS3 of voltage regulator 502 is 2.5 volts. The output voltage VO is (2.5 volts/resistor RS3) ((resistor RS1 ″) resistor RS2) +2.5 volts.

At time T4, when the output voltage VO reaches the first output voltage value V1, the first control circuit 20 generates a corresponding control signal S1 to control the power switch SW1 to start a switching operation, such as Pulse Width Modulation (PWM) switching. In this way, during the time period T4-T5, as shown in fig. 2, the output voltage VO is maintained at the first output voltage value V1, the power switch SW3 is continuously maintained in the on state, and the current detection voltage VCS is maintained lower than the reference voltage VR 3.

At time T5, the second control circuit 40 receives the SYSTEM signal SS via the pin SYSTEM to instruct the output voltage VO to be switched to the second output voltage value V2. The second control circuit 40 outputs a corresponding control signal S3 according to the system signal SS to control the power switch SW3 to switch to the non-conductive state. At this time, resistor RC2 becomes an open circuit state. As shown in fig. 3, the output voltage dividing resistors of the output voltage switching circuit 50 are a resistor RS1 and a resistor RS 3. The total voltage-dividing resistance value of the output voltage switching circuit 50 becomes the series resistance value of the resistor RS1 and the resistor RS 3. Since the resistance of each resistor is greater than the equivalent resistance of each resistor connected in parallel with other resistors, the resistance of the resistor RS1 is greater than the equivalent resistance of the resistor RS1 connected in parallel with the resistor RS2 during the time T3T 5. That is, the series resistance of the resistor RS1 and the resistor RS3 in the output voltage switching circuit 50 is larger than the series resistance of the resistor RS1 and the resistor RS2 connected in parallel and then connected in series with the resistor RS3 during the time T3 to T5. Meanwhile, since the voltage regulator 502 maintains the voltage across the resistor RS3 VRS3 at a constant value (e.g., 2.5 volts), the current flowing through the resistor RS3 is constant (e.g., the current flowing through the resistor RS3 is 2.5 volts/RS 3). In this case, for the output voltage switching circuit 50, when the total voltage-dividing resistance value becomes large and the current is not changed, the voltage across the output terminal OUT to the resistor RS3 (i.e., the voltage across the resistor RS 1) increases, and thus the output voltage VO also increases. As shown in FIG. 2, during the time T5-T6, the output voltage VO continuously increases, and the current-sensing voltage VCS also continuously increases. In other words, under the control of the second control circuit 40, the output voltage switching circuit 50 switches from a first output voltage mode to a second output voltage mode, and the output voltage VO can continue to increase from the first output voltage V1 to provide the output of the second output voltage V2.

At time T6, the comparator 202 determines that the current-sense voltage VCS is greater than the reference voltage VR 1. As shown in FIG. 2, assume that the time length between time T6 and T7 is D (e.g., time length D may be 200 microseconds (μ s)). During the time period T6-T7, the comparator 202 determines that the current detection voltages VCS are all greater than the reference voltage VR1 for the predetermined time D according to the time count of the timer 208. The voltage typically rises instantaneously and for an extremely short duration due to the occurrence of unexpected or unwanted system overvoltage problems. For example, when the short circuit occurs in the photocoupler 602 of the feedback circuit 60, the output voltage VO rapidly rises, the winding voltage VNS of the secondary winding NS also rapidly rises, and the winding voltage VNA induced to the auxiliary winding NA also rapidly rises and lasts for a very short time. That is, when the current-sense voltage VCS is greater than the reference voltage VR1 for a predetermined time D, it indicates that the rise of the current-sense voltage VCS is caused by switching the output voltage, and is not an unexpected or unwanted system overvoltage problem.

Therefore, at time T7, when the comparator 202 determines that the current detection voltage VCS is greater than the reference voltage VR1 during the period T6-T7, the comparator 202 generates and outputs a comparison signal to the driver 210 to notify the driver 210 to turn on the auxiliary switch SW 2. The driver 210 accordingly generates the control signal S2 to the auxiliary switch SW2, such that the auxiliary switch SW2 is switched to the on state corresponding to the control signal S2. Therefore, as shown in fig. 5, the total resistance value of the load resistors connected between the switch SW1 and the first ground GND1 is the parallel resistance value obtained by connecting the resistor RC1 and the resistor RC2 in parallel. Since the equivalent resistance of the resistors connected in parallel is smaller than the resistance of the respective resistors, the total resistance of the load resistor connected between the switch SW1 and the first ground GND1 is smaller than the resistance of the resistor RC1 (the parallel resistance of the resistor RC1 and the resistor RC2 is smaller than the resistance of the resistor RC 1), so that the current sensing voltage VCS will drop, and a higher output voltage VO can be allowed to make the current sensing voltage VCS reach the trigger voltage of the overvoltage protection. After time T7, the output voltage VO continues to rise until it reaches the second output voltage value V2. In other words, the voltage converter 1 of the embodiment of the invention provides the output voltage VO of the first output voltage value V1 during the time T4-T5 according to the system requirement. After the time T5, the second control circuit 40 controls the output voltage switching circuit 50 to switch according to the system requirement, so that the voltage converter 1 can provide the output voltage VO of the second output voltage value V1 after the time T7.

In summary, the voltage converter 1 of the embodiment of the invention can switch to output different output voltages according to the system requirement. Moreover, through the cooperation of the first control circuit 20 and the current detection circuit 30, the current detection voltage VCS can be adjusted at a proper time when the low output voltage is switched to the high output voltage without adjusting the settings of the reference voltages VR2 and VR3 applied by the comparator 204 and the comparator 206 for performing the overvoltage protection function for different output voltages.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims

1. A voltage converter, comprising:

a transformer, including a primary winding, a secondary winding and an auxiliary winding, for converting an input voltage into an output voltage;

a power switch, a first end of which is connected to the primary side winding;

the first control circuit is connected to a second end of the power switch and used for generating a first control signal according to a current detection voltage so as to control the operation of the power switch and generate a second control signal; and

a current detection circuit, connected to a third terminal of the power switch, the first control circuit and the auxiliary winding, for sensing the current detection voltage according to the second control signal and providing the current detection voltage to the first control circuit; wherein the current detection circuit comprises:

a first resistor, a first end of which is connected to the third end of the power switch, the first control circuit and the auxiliary winding, the current detection voltage is output to the first control circuit through the first end of the first resistor, and a second end of which is connected to a first ground, wherein a first end of the auxiliary winding is connected to the third end of the power switch through a diode and a resistor;

a first auxiliary switch, a first end of which is connected to the third end of the power switch, the first control circuit and the auxiliary winding, and a second end of which is connected to the first control circuit for receiving the second control signal; and

a second resistor, a first end of the second resistor is connected to a third end of the first auxiliary switch, and a second end of the second resistor is connected to the first ground; the first control circuit includes:

a timer for counting a predetermined time;

a comparator having a first input terminal, a second input terminal and an output terminal, the comparator being configured to compare signals received by the first input terminal and the second input terminal according to the counting operation of the timer to generate a comparison signal, wherein the first input terminal is configured to receive the current detection voltage, the second input terminal is configured to receive a reference voltage, and the output terminal is configured to output the comparison signal; and

a driver connected to the output end of the comparator for generating the second control signal according to the comparison signal.

2. The voltage converter according to claim 1, wherein when the current detection voltage is greater than the reference voltage and the current detection voltage is greater than the reference voltage for the predetermined time, the comparator generates and outputs the comparison signal to the driver, the driver generates the second control signal to the first auxiliary switch accordingly, and the first auxiliary switch is in a conducting state corresponding to the second control signal.

3. The voltage converter of claim 1, wherein the comparator generates and outputs the comparison signal to the driver when the current detection voltage is less than the reference voltage, the driver generates the second control signal to the first auxiliary switch accordingly, and the first auxiliary switch is in a non-conducting state due to the second control signal.

4. The voltage converter of claim 1, further comprising

A second control circuit for generating a third control signal according to a system signal; and

an output voltage switching circuit comprises

A third resistor, a first end of the third resistor is connected to a first end of the secondary side winding;

a fourth resistor, a first end of which is connected to a second end of the third resistor, and a second end of which is connected to a second ground;

the voltage stabilizer is connected to the first end of the fourth resistor and the second ground and used for controlling a cross voltage of the fourth resistor, so that the cross voltage of the fourth resistor has a fixed voltage difference value;

a second auxiliary switch, a first end of the second auxiliary switch is connected to a first end of the secondary winding and the first end of the third resistor, a second end of the second auxiliary switch is connected to the second control circuit for receiving the third control signal; and

a fifth resistor, a first end of the fifth resistor is connected to a third end of the second auxiliary switch, and a second end of the fifth resistor is connected to the second end of the third resistor, the first end of the fourth resistor, and the regulator.

5. The voltage converter according to claim 4, wherein the second control circuit generates the third control signal accordingly and the second auxiliary switch is in a non-conducting state corresponding to the third control signal when the system signal indicates that the output voltage is a first output voltage value.

6. The voltage converter according to claim 5, wherein when the system signal indicates that the output voltage is a second output voltage value, the second control circuit generates the third control signal accordingly and the second auxiliary switch is turned on by the third control signal, wherein the first output voltage value is smaller than the second output voltage value.

7. The voltage converter of claim 4, further comprising:

a first diode, an anode of the first diode is connected to the first end of the secondary side winding, and a cathode of the first diode is connected to the first end of the third resistor and the first end of the second auxiliary switch; and

a first end of the first capacitor is connected to the cathode of the first diode, the first end of the third resistor and the first end of the second auxiliary switch, and a second end of the first capacitor is connected to the second ground.