Double-cut voltage conversion circuit and voltage regulator

Abstract

The utility model relates to a double-cut voltage conversion circuit for high-voltage detection, which comprises a second rectifying circuit and a first rectifying circuit which are connected to a voltage input end, an input end of a first switch and a switch control circuit are connected with the second rectifying circuit, and a high-voltage switch circuit is electrically connected to the switch control circuit; a stop working voltage value is preset in the high-voltage switch circuit, when the voltage of the voltage input end is higher than the preset value, the switch control circuit controls the first switch to be switched on, and the power supply input voltage flows back to the second rectifying circuit through the first switch; when the voltage of the voltage input end is lower than a value, the high-voltage switch circuit is conducted to work, the switch control circuit is made to control the first switch to be cut off, the power input voltage cannot flow back to the second rectifying circuit through the first switch, at the moment, the wave crest voltage of the power input is cut off, and therefore the purpose of voltage reduction is achieved. Input voltage detection and switch on-off control are carried out in real time, and detection, rectification and chopping processing of an input power supply are realized.

Description

Technical Field

[0001] The present application relates to the technical field of voltage conversion, and in particular to a double-cut voltage conversion circuit and a voltage regulator. Background Art

[0002] At present, power tools and electronic products such as mobile phones, tablets, computers, hair dryers, etc., all rely on power supply devices. Different types of electronic and electrical products have different power supply voltage requirements. The power supply systems in various countries and regions around the world have formed various voltages, so different voltage conversion devices are needed.

[0003] The step-down processing circuit of the traditional linear voltage converter generally performs rectification first, and then steps down the rectified output, which often requires complex switching and duty cycle control. As a result, the voltage converter of the prior art is relatively complex, resulting in low energy efficiency conversion, large and bulky size, and is increasingly less used in personal electrical appliances.

[0004] There is a certain demand for the lightweight and convenient thyristor converter, but this technology has inherent disadvantages and cannot be widely used. For example, the thyristor destroys the waveform of the sine wave, thereby reducing the power factor value, and the smaller the conduction angle, the worse the power factor. The non-sinusoidal waveform will increase the harmonic coefficient, and the non-sinusoidal waveform will generate serious interference signals (EMI) on the line. In addition, it is easy to be unstable at low load, so a bleeder resistor must be added. This bleeder resistor consumes at least 1-2 watts of power. Utility Model Content

[0005] In order to solve the above technical problems, the present application provides a double-cut voltage conversion circuit, including a first branch and a second branch connected to a voltage input end, the first branch including a first rectifier circuit and a high-voltage switch circuit, the second branch including a second rectifier circuit, a first switch and a switch control circuit, the second rectifier circuit and the first rectifier circuit are connected in parallel to the voltage input end, the input end of the first switch and the switch control circuit are connected to the second rectifier circuit, and the high-voltage switch circuit is electrically connected to the switch control circuit; wherein the high-voltage switch circuit is preset with a cut-off working voltage value A, when the voltage at the voltage input end is higher than the A value, the high-voltage switch circuit stops working, and the switch control circuit controls the first switch to turn on, the power supply input voltage flows back to the second rectifier circuit through the first switch, and the second rectifier circuit outputs to the load output end; when the voltage at the voltage input end is lower than the A value, the high-voltage switch circuit is turned on, and the switch control circuit controls the first switch to stop, and the power supply input voltage cannot flow back to the second rectifier circuit through the first switch.

[0006] By setting up a first rectifier circuit that is dual to the second rectifier circuit and setting up a high-voltage switch circuit connected to the first rectifier circuit, the input voltage of the first switch can be detected in real time, and when it is detected that the input voltage reaches a specific threshold, a control signal is sent to control the first switch to be turned on or off, and whether the input voltage flows back to the second rectifier circuit, thereby achieving the purpose of voltage regulation.

[0007] Preferably, the high-voltage switch circuit includes a first voltage stabilizing diode and a light emitting diode, and a phototransistor electrically connected to the light emitting diode is provided in the switch control circuit, and the voltage value A is the conduction voltage of the first voltage stabilizing diode; the light emitting diode is used to send a light control signal to the phototransistor when working. By setting the voltage stabilizing diode, when the input voltage reaches the conduction voltage of the voltage stabilizing diode, the first voltage stabilizing diode is turned on, and the high-voltage switch circuit sends a signal to the switch control circuit to control the conduction or cutoff of the first switch. This scheme only needs to use one voltage stabilizing diode to realize voltage detection and switching logic judgment, and different switching voltages or duty cycle parameter settings can be realized by replacing voltage stabilizing diodes with different conduction parameters, which greatly simplifies the circuit implementation. By using the light emitting diode to realize the sending of the switch switching control signal, there is no need to directly connect the high-voltage switch circuit and the rectifier and buck circuit of the first switch through the circuit, so as to avoid the interference of the high-voltage switch circuit on the rectifier and buck circuit, and also make the circuit simpler and modular, avoiding the complex connection and constraint relationship of the circuit.

[0008] Preferably, the switch control circuit includes a phototransistor, which is used to receive the light control signal sent by the light emitting diode and control the cut-off or conduction of the first switch according to the light control signal. The phototransistor receives the switch switching control signal of the high-voltage switch circuit, thereby avoiding the interference caused by the direct circuit connection and the complex circuit constraint relationship, so that the circuit is simplified.

[0009] Preferably, the switch control circuit includes a second switch, a three-terminal adjustable voltage regulator, a voltage divider circuit connected to the three-terminal adjustable voltage regulator, the phototransistor is connected in parallel to the voltage divider circuit, the second switch is connected to the second rectifier circuit and the control end of the first switch, and the second switch is turned on or off to control the first switch to be turned on or off. The reference terminal voltage of the three-terminal adjustable voltage regulator is determined by the voltage divider circuit composed of resistors R3 and R6. When the phototransistor is working, the reference voltage is low, thereby turning on the second switch, and then the second switch turns on the first switch, and the power input voltage flows back to the second rectifier circuit through the first switch and is output to the load.

[0010] By setting up a three-terminal adjustable regulator and the second switch, the second switch is connected to the second rectifier circuit and the control end of the first switch, and the voltage state of the control end of the first switch is quickly switched through the on-off control of the second switch, thereby realizing the fast switching control of the on-off of the first switch.

[0011] Preferably, the control end of the second switch is connected to an R2 resistor, an R4 resistor and a three-terminal adjustable voltage regulator, wherein the control end of the second switch is connected between the voltage divider circuit formed by the R2 resistor and the R4 resistor, and the three-terminal adjustable voltage regulator is connected to the other side of the R4 resistor relative to the power input end. The three-terminal adjustable voltage regulator operates in an on or off state according to the control signal of the high-voltage switch circuit, so that the control end of the second switch is in a high voltage or low voltage state, thereby realizing the on-off control of the second switch.

[0012] Preferably, the voltage divider circuit includes a resistor R3 and a resistor R6 connected in series, the phototransistor is connected in parallel to the resistor R6, and the reference end of the three-terminal adjustable voltage regulator is connected between the resistor R3 and the resistor R6. The phototransistor is used to operate in an on or off state according to the control signal of the light-emitting diode. Since the phototransistor is connected in parallel to the resistor R6, when the phototransistor operates in an on state, the voltage of the resistor R6 is pulled down, and then the reference end input voltage of the three-terminal adjustable voltage regulator is pulled down, so that the three-terminal adjustable voltage regulator operates in an off state; when the phototransistor operates in an off state, the reference end input voltage of the three-terminal adjustable voltage regulator is determined by the voltage divider circuit composed of the resistor R3 and the resistor R6. At this time, the reference end input voltage is higher than the internal Vref voltage of the voltage regulator, and the three-stage adjustable voltage regulator is in an on state.

[0013] Preferably, the switch control circuit further includes a first capacitor, which is arranged on a side of the second switch, the R2 resistor, the R4 resistor, the R3 resistor, and the R6 resistor close to the power input terminal. The first capacitor can filter or reduce the fluctuation of the AC voltage input, providing a suitable working voltage environment for the latter stage of the switch control circuit.

[0014] Preferably, the switch control circuit further includes a third switch, and the input end of the third switch is connected to the control end of the first switch. In some embodiments, the first switch adopts a MOS tube, and the gate of the MOS tube may form an equivalent capacitor. Capacitor energy storage may cause the first switch to respond slowly to the shutdown control on the one hand, and may also damage the device on the other hand. In this scheme, a third switch is set at the control end of the first switch. When the second switch is turned off, the gate voltage of the MOS tube of the first switch is higher than the control end of the third switch due to the capacitor effect, and the third switch is turned on, so that the control end of the first switch is discharged quickly, which speeds up the shutdown response speed of the first switch.

[0015] Preferably, the present solution also includes a charging device using the above-mentioned double-cut voltage conversion circuit.

[0016] From the above, it can be seen that the following beneficial effects can be obtained by applying the method provided by this application:

[0017] (1) This solution realizes input power detection, rectification and chopping by setting up a voltage detection circuit that is dual to the power processing circuit to perform input voltage detection and switch on / off control in real time.

[0018] (2) This solution uses a voltage zener diode for voltage detection. The circuit is simple and easy to implement, and does not require complex duty cycle control logic. This solution uses the cooperation of light-emitting diodes and phototransistors to achieve the transmission of switch control signals, isolates the detection module from the power processing module, avoids interference between modules, and reduces circuit complexity.

[0019] (3) This solution realizes fast switching of the working conditions of the control end of the first switch and fast discharge and fast shutdown response of the first switch by setting the second switch to control the on-off of the first switch.

[0020] (4) The switch control circuit of this scheme can reduce the impact of AC input on the back-end devices by setting up voltage-stabilizing diodes and capacitors. It can provide a suitable operating point for the back-end devices without setting up a DC power supply, thereby simplifying the circuit complexity.

[0021] (5) The conversion circuit of this scheme avoids destroying the waveform of the sine wave, thereby making the power factor value and the harmonic coefficient normal and avoiding the generation of serious interference signals.

[0022] (6) The conversion circuit of this scheme can still output stably under low load, without adding a bleeder resistor, thus simplifying the circuit and reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings required for use in the description of the embodiments of the present application or the prior art are briefly introduced below. Obviously, the drawings described below are only part of the embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor.

[0024] Figure 1 A schematic block diagram of a double-cut voltage conversion circuit according to an embodiment of the present application;

[0025] Figure 2 This is a circuit schematic diagram of a double-cut voltage conversion circuit according to an embodiment of the present application.

[0026] Figure 3 This is a circuit diagram of the first branch of the double-cut voltage conversion circuit according to an embodiment of the present application.

[0027] Figure 4 This is a circuit diagram of the second branch of the double-cut voltage conversion circuit according to an embodiment of the present application.

[0028] Reference numerals

[0029] 10. Voltage input terminal; 20. Second rectifier circuit; 30. Switch control circuit; 40. First switch; 50. First rectifier circuit; 60. High-voltage switch circuit; 31. Phototransistor; 32. Second switch; 33. R2 resistor; 34. R4 resistor; 35. Three-terminal adjustable voltage regulator; 36. R3 resistor; 37. R6 resistor; 38. First capacitor; 39. Second voltage regulator diode; 41. Third switch; 61. First voltage regulator diode; 62. Light-emitting diode. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0031] like Figure 1 As shown, this embodiment provides a double-cut voltage conversion circuit, such as Figure 1 As shown, it includes a first branch and a second branch connected to the voltage input terminal 10, the first branch includes a first rectifier circuit 50 and a high-voltage switch circuit 60, the second branch includes a second rectifier circuit 20 connected to the output terminal, a first switch 40 and a switch control circuit 30, the second rectifier circuit 20 and the first rectifier circuit 50 are connected in parallel to the voltage input terminal 10, the input terminal of the first switch 40 and the switch control circuit 30 are connected to the second rectifier circuit 20, and the high-voltage switch circuit 60 is electrically connected to the switch control circuit 30.

[0032] Among them, a cut-off working voltage value A is preset in the high-voltage switch circuit 60. When the voltage at the voltage input terminal 10 is higher than the A value, the high-voltage switch circuit 60 stops working, and the switch control circuit 30 controls the first switch 40 to be turned on, and the input voltage flows back to the second rectifier circuit 20 through the first switch 40, and then is output from the output terminal to the load; when the voltage at the voltage input terminal is lower than the A value, the high-voltage switch circuit 60 is turned on, and the switch control circuit 30 controls the first switch 40 to be cut off, and the power supply input voltage cannot flow back to the second rectifier circuit 20 through the first switch 40. At this time, the peak voltage of the power supply input is cut off, thereby achieving the purpose of voltage reduction.

[0033] Specifically, Figure 2 As shown, the high-voltage switch circuit 60 includes a first voltage-stabilizing diode 61 and a light-emitting diode 62. A phototransistor 31 electrically connected to the light-emitting diode 62 is provided in the switch control circuit 30. The voltage value A is the conduction voltage of the first voltage-stabilizing diode 61. When the light-emitting diode 62 is working, it is used to send a light control signal to the phototransistor 31. In one embodiment of the present scheme, when the input voltage of the voltage input terminal 10 reaches the conduction voltage of the first voltage-stabilizing diode 61, the first voltage-stabilizing diode 61 is turned on, and current flows through the light-emitting diode 62 to make it work. The light-emitting diode 62 emits a light signal and transmits it to the switch control circuit 30. The light-emitting diode 62 is used to realize the transmission of the switch switching control signal, and there is no need to directly connect the high-voltage switch circuit 60 and the first switch 40 or the rectifying and bucking circuit of the switch control circuit 30 through the circuit, so as to avoid the high-voltage switch circuit 60 interfering with the front-stage rectifying and bucking circuit, and also make the circuit simpler and modular, avoiding the complex connection and constraint relationship of the circuit. This solution only needs to use a voltage regulator diode to realize voltage detection, and cooperate with a light-emitting diode and a phototransistor to realize switching logic judgment. In addition, different switching voltages or duty cycle parameter settings can be achieved by replacing voltage regulator diodes with different conduction parameters, which greatly simplifies the circuit implementation.

[0034] For example, in order to reduce the voltage of 220V to 120V, the voltage value A is first set to 120V. The condition for the first voltage zener diode 61 to be turned on is that the input voltage is not less than 120V. When the input voltage is lower than 120V, the first voltage zener diode 61 is turned off, so that the light-emitting diode 62 does not work, and then the phototransistor 31 in the switch control circuit 30 does not work. At this time, the first switch 40 is controlled to be turned on by the switch control circuit 30, and the input voltage flows back to the second rectifier circuit 20 through the first switch 40, and then is output from the output end to the load; when the input voltage is greater than 120V, the first voltage zener diode 61 is turned on, so that the light-emitting diode 62 works, and then the phototransistor 31 in the switch control circuit 30 works, and the power input voltage cannot flow back to the second rectifier circuit 20 through the first switch 40. At this time, the peak voltage of the power input is cut off, thereby achieving the purpose of voltage reduction.

[0035] In the above scheme, the phototransistor 31 is used to receive the light control signal sent by the light emitting diode 62, and the switch control circuit 30 controls the cut-off or conduction of the first switch 40 according to the light control signal. The phototransistor 31 receives the switch switching control signal of the high-voltage switch circuit 60, and the interference caused by the direct circuit connection is avoided, and the circuit is simplified.

[0036] Further, the switch control circuit 30 includes a second switch 32, a three-terminal adjustable voltage regulator 35, a voltage divider circuit connected to the three-terminal adjustable voltage regulator 35, a photosensitive transistor 31 is connected in parallel to the voltage divider circuit, the second switch 32 is connected to the second rectifier circuit 20 and the control end of the first switch 40, and the second switch 32 is turned on or off to control the first switch 40 to be turned on or off. In an embodiment of the present scheme, in some embodiments, the first switch 40 adopts a MOS tube, and the second switch 32 can be a PNP transistor. At this time, the turn-off condition of the second switch 32 is that the control end works in a high potential state; the second switch 32 can also be an NPN transistor, and at this time, the turn-off condition of the second switch 32 is that the control end works in a low potential state; the second switch 32 can also be other switch devices, and it only needs to be set to the corresponding cut-off condition to realize the turn-off of the second switch 32, which will not be described in detail here. By setting the second switch 32, the second switch 32 is connected to the second rectifier circuit 20 and the control end of the first switch 40, and the voltage state of the control end of the first switch 40 is quickly switched through the on-off control of the second switch 32, so as to realize the fast switching control of the on-off of the first switch.

[0037] Further, the voltage divider circuit includes a R3 resistor 36 and an R6 resistor 37 connected in series, a phototransistor 31 is connected in parallel to the R6 resistor, and a reference end of the three-terminal adjustable voltage regulator 35 is connected between the R3 resistor 36 and the R6 resistor 37. The phototransistor 31 is used to work in an on or off state according to the control signal of the light-emitting diode 62, and the phototransistor 31 is connected in parallel to the R6 resistor 37. The reference end voltage of the three-terminal adjustable voltage regulator 35 is determined by the voltage divider circuit composed of the resistors R3 and R6. When the phototransistor 31 in the second branch is not working, its reference voltage is low, thereby making the base potential of the second switch 32 (PNP transistor) low, and then the second switch 32 is turned on, so that the gate voltage of the first switch 40 (MOS tube) is high, and the first switch 40 is turned on, so that the power input can flow back to the second bridge rectifier circuit through the first switch 40.

[0038] When the phototransistor 31 works in the on state, the voltage of the R6 resistor 37 is pulled down, and then the reference end input voltage of the three-terminal adjustable voltage regulator 35 is pulled down, so that the internal equivalent transistor of the three-terminal adjustable voltage regulator 35 works in the off state, so that the base voltage of the second switch 32 (PNP transistor) is pulled up, the second switch 32 is turned off, and then the control end voltage of the first switch 40 is pulled down, and then the first switch is turned off; when the phototransistor 31 does not receive the light signal of the light-emitting diode 62 and works in the off state, the reference end input voltage of the three-terminal adjustable voltage regulator 35 is determined by the voltage divider circuit composed of the R3 resistor 36 and the R6 resistor 37. At this time, the reference end input voltage is higher than the internal Vref voltage of the voltage regulator, and the internal equivalent transistor of the three-stage adjustable voltage regulator 35 is in the on state, so that the base voltage of the second switch PNP transistor 32 is pulled down, the second switch 32 is turned on, and then the control end voltage of the first switch 40 is pulled up, and then the first switch is turned on.

[0039] The control end of the second switch 32 is connected to the R2 resistor 33, the R4 resistor 34 and the three-terminal adjustable voltage regulator 35, wherein the control end of the second switch 32 is connected between the R2 resistor 33 and the R4 resistor 34, and the three-terminal adjustable voltage regulator 35 is connected to the other side of the R4 resistor 34 relative to the power input terminal 10. The three-terminal adjustable voltage regulator 35 operates in an on or off state according to the control signal of the high-voltage switch circuit 60, so that the control end of the second switch 32 is in a high voltage or low voltage state, thereby realizing the on-off control of the second switch 32. In one embodiment of the present scheme, the three-terminal adjustable voltage regulator 35 operates in two states: cut-off or on. The reference input terminal of the three-terminal adjustable voltage regulator 35 is connected to the phototransistor 31. When the phototransistor 31 receives the light signal sent by the light-emitting diode 62, the phototransistor 31 is turned on, so that the voltage at the reference input terminal of the three-terminal adjustable voltage regulator 35 is reduced, the internal equivalent transistor of the three-terminal adjustable voltage regulator 35 is cut off, and the cathode voltage of the three-terminal adjustable voltage regulator 35 is pulled up, that is, the base voltage of the second switch PNP transistor 32 is pulled up, and the second switch 32 is turned off, thereby causing the voltage at the control terminal of the first switch 40 to be pulled down, thereby causing the first switch to be turned off.

[0040] Furthermore, the switch control circuit 30 further includes a first capacitor 38 and a second voltage stabilizing diode 39, which are arranged on a side close to the power input terminal of the second switch 32, the R2 resistor 33, the R4 resistor 34, the R3 resistor 36, and the R6 resistor 37. The second voltage stabilizing diode 39 and the first capacitor 38 can filter or reduce the fluctuation of the AC voltage input, thereby providing a suitable working voltage environment for the latter stage of the switch control circuit.

[0041] Preferably, the switch control circuit 30 also includes a third switch 41, and the input end of the third switch 41 is connected to the control end of the first switch. In some embodiments, the first switch 40 uses a MOS tube, and the gate of the MOS tube may form an equivalent capacitor. Capacitor energy storage may cause the first switch 40 to respond slowly to the shutdown control on the one hand, and may also damage the device on the other hand. In this scheme, the third switch 41 is set at the control end of the first switch 40. When the second switch 32 is turned off, the gate voltage of the first switch MOS tube 40 is higher than the control end of the third switch 41 due to the capacitor effect, and the third switch 41 is turned on, so that the control end of the first switch 40 is discharged quickly, which speeds up the shutdown response speed of the first switch 40.

[0042] This embodiment provides a voltage regulator, which uses the above-mentioned double-cut voltage conversion circuit. Through the above-mentioned double-cut voltage conversion circuit, voltage conversion can be realized for electronic and electrical products of different categories. Compared with the existing thyristor converter, the double-cut voltage conversion circuit of this scheme can avoid the situation that the existing thyristor converter will destroy the waveform of the sine wave, thereby making the power factor value and harmonic coefficient normal and avoiding the generation of serious interference signals. In addition, the circuit can still output stably at low load, without adding a bleeder resistor, simplifying the circuit and reducing costs.

[0043] On the other hand, the existing charging device generally performs rectification first and then performs voltage reduction processing on the rectified output, and the voltage reduction processing circuit of the prior art often requires complex switch switching and duty cycle control, resulting in the prior art charging device being relatively complex. By setting a second rectifier circuit 50 that is dual to the first rectifier circuit 20, and setting a high-voltage switch circuit 60 to connect the second rectifier circuit 50, the input voltage of the first switch 40 can be detected in real time, and a control signal is sent to control the first switch 40 to be turned on or off when the input voltage reaches a specific threshold, thereby achieving the purpose of voltage regulation, and the above scheme does not need to add a voltage detection function in the voltage processing module after the first rectifier circuit 20, simplifying the circuit complexity.

[0044] please Figure 3-4 As shown, the specific working process of the circuit in this embodiment is as follows:

[0045] When the input voltage is lower than 120V, since the conduction voltage of the first voltage zener diode ZD2 of the first branch is 120V, the first voltage zener diode ZD2 is cut off at this time, and the light-emitting diode U2A does not work; since the light-emitting diode U2A does not work, the photosensitive transistor U2B in the second branch does not work, and the reference terminal voltage of the three-terminal adjustable voltage regulator U1 in the second branch is determined by the voltage divider circuit composed of resistors R3 and R6. At this time, the reference voltage is lower, which makes the base potential of the transistor Q2 (second switch) lower, and the transistor Q2 is turned on, which makes the gate voltage of the transistor Q1 (first switch) higher, and the transistor Q1 is turned on. The power input flows back to the second rectifier circuit through the transistor Q1, and then is output at the output end.

[0046] When the input voltage is higher than 120V, since the conduction voltage of the first voltage zener diode ZD2 of the first branch is 120V, the first voltage zener diode ZD2 is turned on and the light-emitting diode U2A works; since the light-emitting diode U2A works, the phototransistor U2B in the second branch works, and the reference terminal voltage of the three-terminal adjustable voltage regulator U1 in the second branch is determined by the parallel connection of the resistor R3, the resistor R6 and the phototransistor U2B. At this time, the reference voltage is higher, which makes the base potential of the transistor Q2 higher, and the transistor Q2 is cut off, which makes the gate voltage of the transistor Q1 lower, and the transistor Q1 is cut off. At this time, the power input voltage cannot be transmitted back to the second rectifier circuit through the first branch, that is, the peak voltage of the power input is cut off, thereby achieving the purpose of voltage reduction.

[0047] The above-described implementation methods do not constitute a limitation on the protection scope of the technical solution. Any modification, equivalent replacement and improvement made within the spirit and principle of the above-described implementation methods shall be included in the protection scope of the technical solution.

Claims

1. A double-cut voltage conversion circuit, Features: The invention comprises a first branch and a second branch connected to a voltage input terminal, wherein the first branch comprises a first rectifier circuit and a high-voltage switch circuit, the second branch comprises a second rectifier circuit connected to an output terminal, a first switch and a switch control circuit, the second rectifier circuit and the first rectifier circuit are connected in parallel to the voltage input terminal, the input terminal of the first switch and the switch control circuit are connected to the second rectifier circuit, and the high-voltage switch circuit is electrically connected to the switch control circuit; Among them, a cut-off working voltage value A is preset in the high-voltage switch circuit. When the voltage at the voltage input end is higher than the A value, the high-voltage switch circuit stops working, and the switch control circuit controls the first switch to be turned on, and the power input voltage flows back to the second rectifier circuit through the first switch; when the voltage at the voltage input end is lower than the A value, the high-voltage switch circuit is turned on, and the switch control circuit controls the first switch to be cut off, and the power input voltage cannot flow back to the second rectifier circuit through the first switch.

2. The double-cut voltage conversion circuit according to claim 1, Features: The high-voltage switching circuit includes a first voltage-stabilizing diode and a light-emitting diode. A phototransistor electrically connected to the light-emitting diode is provided in the switch control circuit. The voltage value A is the conduction voltage of the first voltage-stabilizing diode. When the light-emitting diode is working, it is used to send a light control signal to the phototransistor.

3. The double-cut voltage conversion circuit according to claim 2, Features: The phototransistor is used to receive the light control signal sent by the light emitting diode, and control the cut-off or conduction of the first switch according to the light control signal.

4. The double-cut voltage conversion circuit according to claim 3, Features: The switch control circuit also includes a second switch, a three-terminal adjustable voltage regulator, and a voltage divider circuit connected to the three-terminal adjustable voltage regulator. The phototransistor is connected in parallel to the voltage divider circuit. The second switch is connected to the second rectifier circuit and the control end of the first switch. The second switch is turned on or off to control the first switch to be turned on or off.

5. The double-cut voltage conversion circuit according to claim 4, Features: The voltage divider circuit includes a resistor R3 and a resistor R6 connected in series, the phototransistor is connected in parallel to the resistor R6, and the reference end of the three-terminal adjustable voltage regulator is connected between the resistor R3 and the resistor R6.

6. The double-cut voltage conversion circuit according to claim 5, Features: The control end of the second switch is connected to the R2 resistor and the R4 resistor, wherein the control end of the second switch is connected between the R2 resistor and the R4 resistor, and the three-terminal adjustable regulator is connected to the other side of the R4 resistor relative to the power input terminal.

7. The double-cut voltage conversion circuit according to claim 6, Features: The switch control circuit also includes a first capacitor and a second voltage-stabilizing diode, which are arranged on a side of the second switch, the R2 resistor, the R4 resistor, the R3 resistor, and the R6 resistor close to the power input terminal.

8. The double-cut voltage conversion circuit according to claim 4, Features: The switch control circuit further includes a third switch, an input end of the third switch is connected to a control end of the first switch.

9. A voltage regulator, Features: A double-cut voltage conversion circuit as described in any one of claims 1 to 8 is used.

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