Input voltage detection circuit for switching working states of electrolytic capacitor

Abstract

The utility model relates to the technical field of voltage detection, in particular to an input voltage detection circuit for switching working states of an electrolytic capacitor, which comprises a triode Q1, a triode Q2, a metal oxide semiconductor (MOS) tube Q3 and an electrolytic capacitor E2. The emitter electrode of the triode Q1 is electrically connected with the zero line of the mains supply, the emitter electrode of the triode Q2, the source electrode of the MOS tube Q3 and an external load, the base electrode of the triode Q1 is electrically connected with the base electrode of the triode Q2, the collector electrode of the triode Q2 is electrically connected with the grid electrode of the MOS tube Q3, the drain electrode of the MOS tube Q3 is electrically connected with the other end of the electrolytic capacitor E2, when the input voltage is lower than a set value, the triode Q2 is not conducted, and when the input voltage is lower than a set value, the MOS tube Q3 is turned off. And the MOS tube Q3 is conducted, and the electrolytic capacitor E2 is connected to the circuit, so that the problem of insufficient capacity of the low-voltage electrolytic capacitor is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of voltage detection, in particular to an input voltage detection circuit for switching the working state of an electrolytic capacitor. Background Art

[0002] In view of the current global power grid characteristics, in order to be compatible with the power grid voltages of all countries, the product input voltage needs to meet 100V-240V; in order to meet the design requirements, the capacity of the rectified electrolytic capacitor needs to be twice that of the electrolytic capacitor with an input voltage of 170V-240V; and the larger the capacity of the electrolytic capacitor, the larger the size of the electrolytic capacitor required, which is contrary to the current design concept of small-size products; therefore, an input voltage detection circuit is particularly needed to solve the size problem of low-voltage electrolytic capacitors. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide an input voltage detection circuit for switching the working state of an electrolytic capacitor, which can solve the problem of insufficient capacity of a small-sized low-voltage capacitor.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is:

[0005] An input voltage detection circuit for switching the working state of an electrolytic capacitor comprises a transistor Q1, a transistor Q2, a MOS transistor Q3 and an electrolytic capacitor E2, wherein the collector of the transistor Q1 is electrically connected to the live wire of a mains power supply, one end of the electrolytic capacitor E2 and an external load respectively, the emitter of the transistor Q1 is electrically connected to the neutral wire of the mains power supply, the emitter of the transistor Q2, the source of the MOS transistor Q3 and the external load respectively, and the emitter of the transistor Q1, the emitter of the transistor Q2 and the source of the MOS transistor Q3 are all grounded, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load.

[0006] Furthermore, it also includes a resistor R1, a resistor R2 and a resistor R3, one end of the resistor R1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and the load of the external device, the other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3 and the collector of the transistor Q1, and the other end of the resistor R3 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the load of the external device.

[0007] Furthermore, it also includes a voltage regulator tube ZD1, the cathode of the voltage regulator tube ZD1 is electrically connected to the other end of the resistor R1 and one end of the resistor R2 respectively, and the anode of the voltage regulator tube ZD1 is electrically connected to the base of the transistor Q2 and the gate of the MOS tube respectively.

[0008] Furthermore, it also includes a resistor R5 and a resistor R6, one end of the resistor R5 is electrically connected to the live wire of the mains, the collector of the transistor Q1, one end of the electrolytic capacitor E2 and the external load, the other end of the resistor R5 is electrically connected to the collector of the transistor Q2, the gate of the MOS tube Q3 and one end of the resistor R6, the other end of the resistor R6 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load, and the other end of the resistor R6 is grounded.

[0009] Furthermore, it also includes a voltage regulator tube ZD2, the cathode of which is electrically connected to the other end of the resistor R5, the collector of the transistor Q2, one end of the resistor R6 and the gate of the MOS tube Q3, and the anode of the voltage regulator tube ZD2 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the other end of the resistor R6, the source of the MOS tube Q3 and the external load, and the anode of the voltage regulator tube ZD2 is grounded.

[0010] Furthermore, it also includes a resistor R4, one end of which is electrically connected to the base of the transistor Q2 and the base of the transistor Q1, respectively, and the other end of the resistor R4 is electrically connected to the neutral line of the AC power, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load, and the other end of the resistor R4 is grounded.

[0011] The beneficial effects of the utility model are:

[0012] In this scheme, a transistor Q1, a transistor Q2, a MOS tube Q3 and an electrolytic capacitor E2 are arranged. The collector of the transistor Q1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and the external load respectively. The emitter of the transistor Q1 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load respectively. The base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS tube Q3, the drain of the MOS tube Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load. When the input voltage is higher than the set value, the transistor Q2 is turned on and the MOS tube Q3 is turned off. When the input voltage is turned on, the transistor Q1 is turned on and the electrolytic capacitor E2 is disconnected, thereby preventing the electrolytic capacitor E2 from failing due to overvoltage; when the input voltage is lower than the set value, the transistor Q2 is not turned on, the MOS tube Q3 is turned on, the transistor Q1 is disconnected, and the electrolytic capacitor E2 is connected to the circuit, thereby solving the problem of insufficient capacity of the low-voltage electrolytic capacitor; the circuit designed in this scheme can connect a 200V electrolytic capacitor in parallel when the input voltage is lower than 120VAC (for electrolytic capacitors of the same capacity, the 200V withstand voltage is much smaller than the 400V withstand voltage), and disconnect the 200V electrolytic capacitor when the input voltage is higher than 120VAC, thereby solving the problem of insufficient capacity of small-size low-voltage capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The circuit schematic diagram of the input voltage detection circuit for switching the working state of the electrolytic capacitor of the utility model;

[0014] Description of labels:

[0015] 1. Load. DETAILED DESCRIPTION

[0016] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0017] Please refer to Figure 1 , the technical solution adopted by the utility model is:

[0018] An input voltage detection circuit for switching the working state of an electrolytic capacitor comprises a transistor Q1, a transistor Q2, a MOS transistor Q3 and an electrolytic capacitor E2, wherein the collector of the transistor Q1 is electrically connected to the live wire of a mains power supply, one end of the electrolytic capacitor E2 and an external load respectively, the emitter of the transistor Q1 is electrically connected to the neutral wire of the mains power supply, the emitter of the transistor Q2, the source of the MOS transistor Q3 and the external load respectively, and the emitter of the transistor Q1, the emitter of the transistor Q2 and the source of the MOS transistor Q3 are all grounded, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load.

[0019] From the above description, it can be seen that the beneficial effects of the utility model are:

[0020] In this scheme, a transistor Q1, a transistor Q2, a MOS tube Q3 and an electrolytic capacitor E2 are arranged. The collector of the transistor Q1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and the external load respectively. The emitter of the transistor Q1 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load respectively. The base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS tube Q3, the drain of the MOS tube Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load. When the input voltage is higher than the set value, the transistor Q2 is turned on and the MOS tube Q3 is turned off. When the input voltage is turned on, the transistor Q1 is turned on and the electrolytic capacitor E2 is disconnected, thereby preventing the electrolytic capacitor E2 from failing due to overvoltage; when the input voltage is lower than the set value, the transistor Q2 is not turned on, the MOS tube Q3 is turned on, the transistor Q1 is disconnected, and the electrolytic capacitor E2 is connected to the circuit, thereby solving the problem of insufficient capacity of the low-voltage electrolytic capacitor; the circuit designed in this scheme can connect a 200V electrolytic capacitor in parallel when the input voltage is lower than 120VAC (for electrolytic capacitors of the same capacity, the 200V withstand voltage is much smaller than the 400V withstand voltage), and disconnect the 200V electrolytic capacitor when the input voltage is higher than 120VAC, thereby solving the problem of insufficient capacity of small-size low-voltage capacitors.

[0021] Furthermore, it also includes a resistor R1, a resistor R2 and a resistor R3, one end of the resistor R1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and the load of the external device, the other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3 and the collector of the transistor Q1, and the other end of the resistor R3 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the load of the external device.

[0022] It can be seen from the above description that the resistors R1 , R2 and R3 play the role of current limiting and voltage dividing.

[0023] Furthermore, it also includes a voltage regulator tube ZD1, the cathode of the voltage regulator tube ZD1 is electrically connected to the other end of the resistor R1 and one end of the resistor R2 respectively, and the anode of the voltage regulator tube ZD1 is electrically connected to the base of the transistor Q2 and the gate of the MOS tube respectively.

[0024] Furthermore, it also includes a resistor R5 and a resistor R6, one end of the resistor R5 is electrically connected to the live wire of the mains, the collector of the transistor Q1, one end of the electrolytic capacitor E2 and the external load, the other end of the resistor R5 is electrically connected to the collector of the transistor Q2, the gate of the MOS tube Q3 and one end of the resistor R6, the other end of the resistor R6 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load, and the other end of the resistor R6 is grounded.

[0025] It can be seen from the above description that the resistor R5 and the resistor R6 play the role of current limiting and voltage dividing.

[0026] Furthermore, it also includes a voltage regulator tube ZD2, the cathode of which is electrically connected to the other end of the resistor R5, the collector of the transistor Q2, one end of the resistor R6 and the gate of the MOS tube Q3, and the anode of the voltage regulator tube ZD2 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the other end of the resistor R6, the source of the MOS tube Q3 and the external load, and the anode of the voltage regulator tube ZD2 is grounded.

[0027] From the above description, it can be known that the voltage regulator ZD2 can ensure that the Vgs voltage is lower than the rated value of the MOS tube Vgs, so that the MOS tube Q3 will not fail due to the excessively high Vgs voltage.

[0028] Furthermore, it also includes a resistor R4, one end of which is electrically connected to the base of the transistor Q2 and the base of the transistor Q1, respectively, and the other end of the resistor R4 is electrically connected to the neutral line of the AC power, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load, and the other end of the resistor R4 is grounded.

[0029] From the above description, it can be seen that the resistor R4 plays the role of current limiting and voltage dividing.

[0030] Please refer to Figure 1 , Embodiment 1 of the present utility model is:

[0031] An input voltage detection circuit for switching the working state of an electrolytic capacitor comprises a transistor Q1 (NPN transistor, model FMMT491), a transistor Q2 (NPN transistor, model FMMT491), a MOS transistor Q3 (model 4N60) and an electrolytic capacitor E2 (capacitance value is 20 μF), wherein the collector of the transistor Q1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and an external load 1, and the emitter of the transistor Q1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and an external load 1, respectively. The neutral line of the mains, the emitter of the transistor Q2, the source of the MOS transistor Q3 and the external load 1 are electrically connected, and the emitter of the transistor Q1, the emitter of the transistor Q2 and the source of the MOS transistor Q3 are all grounded, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load 1.

[0032] The above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor also includes a resistor R1, a resistor R2 and a resistor R3, one end of the resistor R1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and the external load 1, the other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3 and the collector of the transistor Q1, and the other end of the resistor R3 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load 1.

[0033] The above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor also includes a voltage regulator tube ZD1, the cathode of which is electrically connected to the other end of the resistor R1 and one end of the resistor R2, and the anode of which is electrically connected to the base of the transistor Q2 and the gate of the MOS tube.

[0034] The above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor also includes a resistor R5 and a resistor R6, one end of the resistor R5 is electrically connected to the live wire of the mains, the collector of the transistor Q1, one end of the electrolytic capacitor E2 and the external load 1, respectively, the other end of the resistor R5 is electrically connected to the collector of the transistor Q2, the gate of the MOS tube Q3 and one end of the resistor R6, the other end of the resistor R6 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load 1, and the other end of the resistor R6 is grounded.

[0035] The above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor also includes a voltage regulator tube ZD2, the cathode of the voltage regulator tube ZD2 is electrically connected to the other end of the resistor R5, the collector of the transistor Q2, one end of the resistor R6 and the gate of the MOS tube Q3, and the anode of the voltage regulator tube ZD2 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the other end of the resistor R6, the source of the MOS tube Q3 and the external load 1, and the anode of the voltage regulator tube ZD2 is grounded.

[0036] The above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor also includes a resistor R4, one end of the resistor R4 is electrically connected to the base of the transistor Q2 and the base of the transistor Q1, respectively, and the other end of the resistor R4 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load 1, and the other end of the resistor R4 is grounded.

[0037] The above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor also includes a rectifier bridge DB1 (model MB10F) and an electrolytic capacitor E1 (capacitance value is 10μF). For the specific connection relationship between the components, please refer to Figure 1 .

[0038] The working principle of the above-mentioned input voltage detection circuit for switching the working state of the electrolytic capacitor is:

[0039] 1. When the input voltage is higher than the set value, the MOS tube Q3 is disconnected, and the electrolytic capacitor E2 is disconnected to prevent the electrolytic capacitor E2 from failing due to overvoltage. The specific analysis is as follows:

[0040] (1) AC power is input through L (i.e. live wire) and N (i.e. neutral wire), rectified by rectifier bridge DB1, filtered by electrolytic capacitor E1, and the input voltage can be directly fed back at Vin;

[0041] (2) Resistors R1, R2 and R3 divide the voltage by resistors, so the voltage at point A can directly reflect the input voltage. When the input voltage at point A is higher than the set value, the voltage at point A is higher than the conduction threshold of the voltage regulator ZD1, and the voltage regulator ZD1 is turned on. At the same time, the voltage at point B is greater than 0.7V (the conduction threshold of the transistor Q2), and the transistor Q2 is turned on. At this time, the current direction is R1→ZD1→Q2.

[0042] (3) When transistor Q2 is turned on, the voltage at point C is close to 0V. Since MOS tube Q3 can only be turned on at a high level, the voltage at point C is close to 0V because transistor Q2 is turned on. At this time, MOS tube Q3 is turned off, so the electrolytic capacitor E2 is disconnected;

[0043] (4) This solution adds a hysteresis circuit. When the input voltage is higher than the set value, the voltage regulator ZD1 is turned on, the voltage at point B is high, and the transistor Q1 is turned on, short-circuiting the resistor R3. The resistor divider changes from the original resistors R1, R2, and R3 to resistors R1 and R2. At this time, the voltage at point A increases, and the circuit will not cause the voltage regulator ZD1 to be cut off due to a slight decrease in the input voltage. By selecting the resistance values ​​of the resistors R1, R2, and R3, the input voltage can be reduced to within 5V, and the electrolytic capacitor E2 still remains in the disconnected mode.

[0044] 2. When the input voltage is lower than the set value, the MOS tube Q3 is turned on and the electrolytic capacitor E2 is connected to the circuit, thus solving the problem of insufficient capacity of the low-voltage electrolytic capacitor. The specific analysis is as follows:

[0045] (1) When the input voltage is lower than the set value, the voltage at point A is lower than the conduction threshold of the voltage regulator ZD1. At this time, no current flows through point B, and the transistor Q2 is not turned on. At this time, the transistor Q2 exhibits high impedance. Through the voltage division of the resistors R5 and R6, the voltage at point C is high level. At this time, the MOS tube Q3 is turned on, and the electrolytic capacitor E2 is connected to the circuit, which solves the problem of insufficient capacitance when the input voltage is lower than the set value.

[0046] (2) The function of the voltage regulator ZD2 is to ensure that the Vgs voltage is lower than the rated value of the MOS tube Vgs, so that the MOS tube Q3 will not fail due to excessive Vgs voltage.

[0047] In the input voltage range of 100V-240V, the traditional solution requires connecting several large 400V electrolytic capacitors in parallel. Under the same size, the withstand voltage of an electrolytic capacitor of 200V is about twice that of an electrolytic capacitor of 400V. The circuit designed in this solution can automatically disconnect and connect the 200V electrolytic capacitor by detecting the input voltage to solve the problems of insufficient low-voltage capacity and high-voltage withstand voltage. Under the same performance, the size of the electrolytic capacitor can be made smaller, thereby reducing the size of the product to meet the current market requirements for product miniaturization.

[0048] In summary, the utility model provides an input voltage detection circuit for switching the working state of an electrolytic capacitor. By setting a transistor Q1, a transistor Q2, a MOS tube Q3 and an electrolytic capacitor E2, the collector of the transistor Q1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and an external load, the emitter of the transistor Q1 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS tube Q3, the drain of the MOS tube Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load. When the input voltage is higher than the set value, the detection circuit detects the input voltage of the electrolytic capacitor E2. value, transistor Q2 is turned on, MOS tube Q3 is turned off, transistor Q1 is turned on, and electrolytic capacitor E2 is turned off, thereby avoiding failure of electrolytic capacitor E2 due to overvoltage; when the input voltage is lower than the set value, transistor Q2 is not turned on, MOS tube Q3 is turned on, transistor Q1 is turned off, and electrolytic capacitor E2 is connected to the circuit, thereby solving the problem of insufficient capacity of low-voltage electrolytic capacitors; the circuit designed in this scheme can connect a 200V electrolytic capacitor in parallel when the input voltage is lower than 120VAC (for electrolytic capacitors of the same capacity, 200V withstand voltage is much smaller than 400V withstand voltage), and disconnect the 200V electrolytic capacitor when the input voltage is higher than 120VAC, thereby solving the problem of insufficient capacity of small-size low-voltage capacitors.

[0049] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. An input voltage detection circuit for switching the working state of an electrolytic capacitor, characterized in that: The invention comprises a transistor Q1, a transistor Q2, a MOS transistor Q3 and an electrolytic capacitor E2, wherein the collector of the transistor Q1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and an external load respectively, the emitter of the transistor Q1 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS transistor Q3 and an external load respectively, and the emitter of the transistor Q1, the emitter of the transistor Q2 and the source of the MOS transistor Q3 are all grounded, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q2 is electrically connected to the gate of the MOS transistor Q3, the drain of the MOS transistor Q3 is electrically connected to the other end of the electrolytic capacitor E2, and one end of the electrolytic capacitor E2 is electrically connected to the external load.

2. The input voltage detection circuit for switching the working state of an electrolytic capacitor according to claim 1, characterized in that: It also includes a resistor R1, a resistor R2 and a resistor R3, one end of the resistor R1 is electrically connected to the live wire of the mains, one end of the electrolytic capacitor E2 and the load of the external device, the other end of the resistor R1 is electrically connected to one end of the resistor R2, the other end of the resistor R2 is electrically connected to one end of the resistor R3 and the collector of the transistor Q1, and the other end of the resistor R3 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q2, the source of the MOS tube Q3 and the load of the external device.

3. The input voltage detection circuit for switching the working state of an electrolytic capacitor according to claim 2, characterized in that: It also includes a voltage regulator tube ZD1, the cathode of which is electrically connected to the other end of the resistor R1 and one end of the resistor R2, and the anode of which is electrically connected to the base of the transistor Q2 and the gate of the MOS tube.

4. The input voltage detection circuit for switching the working state of an electrolytic capacitor according to claim 1, characterized in that: It also includes a resistor R5 and a resistor R6, one end of the resistor R5 is electrically connected to the live wire of the mains, the collector of the transistor Q1, one end of the electrolytic capacitor E2 and the external load, the other end of the resistor R5 is electrically connected to the collector of the transistor Q2, the gate of the MOS tube Q3 and one end of the resistor R6, the other end of the resistor R6 is electrically connected to the neutral wire of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the external load, and the other end of the resistor R6 is grounded.

5. The input voltage detection circuit for switching the working state of an electrolytic capacitor according to claim 4, characterized in that: It also includes a voltage regulator tube ZD2, the cathode of which is electrically connected to the other end of the resistor R5, the collector of the transistor Q2, one end of the resistor R6 and the gate of the MOS tube Q3, and the anode of the voltage regulator tube ZD2 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the other end of the resistor R6, the source of the MOS tube Q3 and the external load, and the anode of the voltage regulator tube ZD2 is grounded.

6. The input voltage detection circuit for switching the working state of an electrolytic capacitor according to claim 1, characterized in that: It also includes a resistor R4, one end of which is electrically connected to the base of the transistor Q2 and the base of the transistor Q1, respectively, and the other end of the resistor R4 is electrically connected to the neutral line of the mains, the emitter of the transistor Q1, the emitter of the transistor Q2, the source of the MOS tube Q3 and the load of the peripheral device, and the other end of the resistor R4 is grounded.

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