A simple PC-level dual power switch control circuit

Abstract

The present invention relates to a simple PC-grade dual-power switch control circuit, comprising a relay drive circuit, a load power supply circuit, and a relay K1. The relay drive circuit includes a power failure detection circuit, a trigger power supply circuit, and a relay trigger circuit. The normally open contact and normally closed contact of the switching contact of K1 are respectively connected to the main power supply and the backup power supply, and the common end is connected to M1 through the load power supply circuit. The power failure detection circuit includes a three-way step-down circuit connected to the three phases of the main power supply. The relay trigger circuit includes an optocoupler U1, a transistor Q2, and a thyristor T1. The neutral point is connected to the input end of U1. The output end of the trigger power supply circuit is respectively connected to the C pole of U1, the C pole of Q2, and the gate of T1. The E pole of U1 is connected to the B pole of Q2. The main power supply, K1, T1, and the ground wire are connected in sequence to form a loop. Compared with the existing technology, the present invention has the advantages of small size and low cost.

Description

Technical Field

[0001] The present invention relates to the field of dual-power switch electrical appliances, and in particular to a simple PC-level dual-power switch control circuit. Background Art

[0002] To prevent prolonged power outages in applications requiring continuous power, a common approach is to use two power sources: a primary power source and a backup power source. Switching to the backup power source occurs when the primary power source fails. Automatic transfer switching equipment (ATSE) is a commonly used device for power switching. Automatic transfer switching equipment (ATSE) ensures continuous and reliable power supply to critical loads. Therefore, the quality and proper use of ATSE products are crucial. An automatic transfer switching equipment consists of three parts: the switch body, the transmission mechanism, and the controller. Common switch bodies include contactors, circuit breakers, and load disconnect switches. Contactors have low reliability and are gradually being phased out. ATSEs are categorized as PC-grade and CB-grade. PC-grade ATSEs can connect and carry current but are not designed to interrupt short-circuit currents. CB-grade ATSEs are equipped with an overcurrent release, whose main contacts can connect and interrupt short-circuit currents. Simple PC-grade dual power supply products, with their compact design and use of small components to implement control functions, not only reduce product size and size but also significantly lower product costs. They also offer higher reliability than larger components such as relays or transformers. To save costs, most existing simple PC-grade dual power supply products only detect voltage loss on the standby power supply, but are unable to detect phase loss on the three-phase power supply. The new version of the standard, "GB 14048.11-2016 Low-voltage switchgear and controlgear - Part 6-1 Multi-function electrical switchgear," has introduced new requirements. Basic dual power supply controllers must detect both phase loss and voltage loss on the standby power supply, while only voltage loss detection is permitted on the standby power supply.

[0003] In order to solve the above problems, the existing technology also provides a solution. Chinese patent CN104716735A proposes a simple dual power conversion device. The control circuit of the device is as follows: Figure 9 and Figure 10 As shown in the figure, the controller power supply is obtained from phase A through a RC step-down circuit, then rectified and filtered to obtain the relay power supply VDD, which is then output through a voltage regulator chip to provide power to the detection circuit and control circuit. The commonly used power supply detection method for phase loss and voltage loss is:

[0004] When phase A is missing, the power supplies VDD and VCC are zero, the controller has no power, and the optocoupler U2 has no output; when phase B or phase C is missing, one path of the optocoupler U2 is not conductive, resulting in no output of the optocoupler U2, SO=0, causing the relay KA1 to change from being attracted to being released, and the motor MG1 is energized through the normally closed contact of KA1, and the common end of the motor MG1 is also powered to the delay circuit C5, D11, C12, VD2 and U7 through the normally closed contact. After a certain delay, the relay KA2 is attracted, the common end of the motor MG1 is connected to the N phase, and the motor switches to the backup power supply; when the normal power supply is normal, SO=1, the relay KA1 is attracted, the motor MG1 is energized through the normally open contact of KA1, and the common end of the motor MG1 is connected to the N phase through the normally open contact after the relay KA3 is attracted, realizing the conversion of the motor to the normal power supply.

[0005] This device has the following two problems:

[0006] First, both the signal and power supply in the circuit are drawn from the phase line using a RC step-down circuit. The capacitor is large and will increase the size of the PCB.

[0007] Secondly, the circuit realizes its functions through three relays, and the control circuit is complex, making it difficult to miniaturize and simplify. Summary of the Invention

[0008] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a simple PC-level dual power supply switching control circuit, which switches the load to the backup power supply when the voltage of the normal power supply for the load is abnormal, and has the advantages of small size and low cost.

[0009] The purpose of the present invention can be achieved by the following technical solutions:

[0010] A simple PC-grade dual-power switch control circuit is used to automatically switch to a backup power supply when the normal power supply for the load M1 fails. It includes a relay drive circuit, a load power supply circuit, and a relay K1. The relay drive circuit includes a power failure detection circuit, a trigger power supply circuit, and a relay trigger circuit.

[0011] The normally open contact and normally closed contact of the conversion contact of K1 are correspondingly connected to the normal power supply and the backup power supply, and the common end is connected to M1 through the load power supply circuit. The K1 includes 3-way conversion contacts. The normally closed contact and normally open contact of the first conversion contact in the 3-way conversion contacts are correspondingly connected to the N line of the backup power supply and the N line of the normal power supply. The normally closed contact and normally open contact of the second conversion contact are respectively empty and connected to the A line of the normal power supply. The normally closed contact and normally open contact of the third conversion contact are respectively connected to the A line of the backup power supply and empty. The load power supply circuit includes 3 connection circuits respectively connected to the common ends of the 3-way conversion contacts.

[0012] An automatic / manual switch is connected in series on the connection circuit between the common end of the first switching contact and M1. When M1 is a motor, when the automatic / manual switch is turned on, the neutral line of the motor is connected to the control neutral line, and the motor can be rotated forward and reverse to automatically drive the mechanism conversion; when the automatic / manual switch is turned off, the neutral line of the motor is disconnected from the control neutral line, the motor cannot be powered, and can only be converted manually.

[0013] An auxiliary switch is connected in series on each of the two-way connection circuits between the common end of the second and third switching contacts and M1 to control and detect the on / off status of the normal power supply and the backup power supply.

[0014] Furthermore, an arc absorption circuit is connected between the 2-way connection circuit connected to the 2nd and 3rd switching contacts and the connection circuit connected to the 1st switching contact, which is used to absorb the high-voltage arc generated when the switching contacts of K1 are switched. The arc absorption circuit includes a resistor and a non-polar capacitor connected in series.

[0015] The power failure detection circuit includes a three-way step-down circuit connected to the three phases of the common power supply. The three step-down circuits have the same impedance and are connected in parallel to form a neutral point. The relay trigger circuit includes an optocoupler U1, a transistor Q2 and a thyristor T1. The neutral point is connected to the input end of U1, the output end of the trigger power supply circuit is respectively connected to the C pole of U1, the C pole of Q2 and the gate of T1, the E pole of U1 is connected to the B pole of Q2, the common power supply, K1, T1 and the ground wire are connected in sequence to form a loop. When the common power supply is normal, the voltage of the neutral point is zero, the U1 is not triggered, the Q2 is turned off, the gate of T1 is triggered by the trigger power supply circuit, the loop formed by the common power supply, K1, T1 and the ground wire is connected in sequence to be turned on, the K1 is energized, and the The common ends of the 1st, 2nd and 3rd switching contacts are respectively connected to the normally open contacts, and the M1 is connected to the A line and N line of the normal power supply; when the A phase, B phase and C phase of the normal power supply are missing or lose voltage, the voltage of the neutral point is not zero, the U1 is triggered, the Q2 is turned on, the current of the triggering power supply circuit is cut off to the ground line, the gate of the T1 is not triggered, and the loop formed by the normal power supply, K1, T1 and the ground line connected in sequence is not conductive, wherein when one phase connected to K1 is missing, K1 is directly powered off. In short, when the normal power supply is missing or loses voltage, K1 is powered off, the common ends of the 1st, 2nd and 3rd switching contacts are respectively connected to the normally closed contacts, and the M1 is connected to the A line and N line of the backup power supply to realize the conversion of M1 from the normal power supply to the backup power supply.

[0016] Furthermore, the power supply fault detection circuit also includes a step-down rectifier circuit between the neutral point and the input end of U1. The step-down rectifier circuit includes a rectifier diode, a step-down resistor and a connector JP1 connected in series. The connector JP1 is used to control whether the three phases of the common power supply are connected to U1. The output end of the connector JP1 is provided with a pull-down resistor to reduce the probability of U1 being falsely triggered.

[0017] Furthermore, the trigger power supply circuit includes a step-down resistor and a rectifier diode connected in series in sequence. The trigger power supply circuit is divided into two outputs after passing through the rectifier diode. The first output is connected to the C pole of U1 after being connected in series with a current limiting resistor, and the second output is connected to the C pole of Q2 after passing through a current limiting resistor.

[0018] Furthermore, a voltage stabilizing filter circuit is connected between the output end of the rectifier diode and the ground wire, and the voltage stabilizing filter circuit includes a pull-down resistor, a voltage stabilizing diode, an electrolytic capacitor and a non-polar capacitor in parallel. Furthermore, a filter circuit is connected between the E pole of U1 and the ground wire, and the filter circuit includes a pull-down resistor, an electrolytic capacitor and a non-polar capacitor in parallel. The non-polar capacitor includes a mica, propylene or ceramic capacitor. The voltage stabilizing diode is used to stabilize the NA voltage of the C pole of the input Q2. The parallel electrolytic capacitor is used to reduce the noise generated by the voltage stabilizing diode. The electrolytic capacitor has a winding inductance and has a poor effect on filtering high-frequency noise. The non-polar capacitor has a small capacity and is used to filter out the high-frequency noise in NA, thereby fully bypassing the high-frequency and low-frequency components contained in NA, increasing the voltage stabilization effect, and reducing the overall probability of false triggering of Q2.

[0019] Furthermore, it also includes two power indicator light power supply circuits with NA and RA as inputs respectively, and the power indicator light power supply circuit includes a rectifier diode, a voltage drop resistor and a light-emitting diode connected in series in sequence, wherein the power indicator light power supply circuit with NA as input also includes a transistor Q1 for cutting off the light-emitting diode, the C pole and E pole of Q1 are correspondingly connected to the positive pole and negative pole of the light-emitting diode, and the B pole of Q1 is connected in series with a current-limiting resistor and then connected to the E pole of U1. When the common power supply is phase-lost, the E pole of U1 has an output, Q1 is turned on and then the light-emitting diode indicating the phase-lost detection status of the common power supply is cut off. The light-emitting diode goes out to indicate that the common power supply is phase-lost, thereby preventing false indication.

[0020] Furthermore, a rectifier full-bridge circuit is connected in series between K1 and T1, and a pull-down resistor is connected between the gate of T1 and the ground line to reduce the probability of false triggering of the gate of T1 due to interference.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The power supply fault detection circuit of the present invention forms a neutral point by setting up three step-down circuits with the same step-down impedance connected to the three phases of the common power supply in parallel, and at the same time, the relay trigger circuit is provided with an optocoupler, a transistor and a thyristor which are connected in sequence and powered by the trigger power supply circuit. When the common power supply is out of phase or loses voltage, the voltage of the neutral point is not zero, thereby triggering the optocoupler, the transistor and the thyristor in sequence, wherein the thyristor is connected to the power supply after being connected in series with the relay. After the thyristor is triggered, the relay is energized, and the relay completes the load switching from the common power supply to the backup power supply through the three-way switching contacts. The power supply fault detection circuit is streamlined, and the dual power supply switching is completed by only one relay. The trigger power supply circuit draws power through the step-down resistor and the rectifier diode. The overall structure of the control circuit is simple, low cost and small size.

[0023] (2) The present invention sets up a power indicator light power supply circuit, and connects the two ends of the light-emitting diode on the power supply circuit of the common power indicator light through a transistor whose B pole is connected to the E pole of the optocoupler. When the common power supply is phase-lost or voltage-lost, the optocoupler and the transistor are triggered in sequence, and the light-emitting diode indicating the common power state is cut off, thereby conveying the common power failure signal and preventing false indication. At the same time, the circuit has fewer circuit components, a simple structure, and low cost.

[0024] (3) The present invention has an auxiliary switch and a manual switch connected in series to the load power supply circuit. The auxiliary switch can detect and control the connection between the load and the power supply. When the load is a motor, the automatic / manual switch can control the connection between the motor and the control neutral line to achieve automatic and manual control of the motor.

[0025] (4) In the present invention, an arc absorption circuit is connected between one of the three circuits of the load power supply circuit connected to the power supply N and the other two circuits, which is used to absorb the high-voltage arc generated when the relay switching switch is switched, thereby improving the circuit safety and the stability of the load operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a circuit principle block diagram of the present invention;

[0027] Figure 2 This is the principle block diagram of the power failure detection circuit;

[0028] Figure 3 This is the relay drive circuit diagram;

[0029] Figure 4 Circuit diagram for power supply to power indicator light;

[0030] Figure 5 Provide a circuit diagram for the relay connections;

[0031] Figure 6 Circuit diagram for supplying power to the load;

[0032] Figure 7 This is the overall circuit diagram of the present invention;

[0033] Figure 8 This is a flow chart of the circuit operation of the present invention;

[0034] Figure 9 For comparison, the patented three-phase voltage loss detection circuit diagram is shown;

[0035] Figure 10 For comparison, the control circuit schematic of the patent;

[0036] Description of the numbers in the figure:

[0037] 11. Trigger power supply circuit, 12. Power failure detection circuit, 13. Relay trigger circuit. DETAILED DESCRIPTION

[0038] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0039] A simple PC-level dual power switch control circuit, such as Figure 1 , used to automatically switch to the backup power supply including line A and line N when the three-phase four-wire common power supply connected to the load M1 fails. The N three-phase four-wire is connected through the socket N_Input, and the A line and N line of the backup power supply are connected through the socket R_Input. The simple PC-level dual power switch control circuit includes a relay drive circuit, a load power supply circuit and a relay K1. The relay drive circuit includes a trigger power supply circuit 11, a power failure detection circuit 12 and a relay trigger circuit 13. Figure 2 and Figure 3 The power failure detection circuit 12 includes three step-down circuits connected in parallel and respectively connected to the three phases of the common power supply. The three step-down circuits have the same impedance and are connected in series with R 16 and R 17 、R 19 and R 20 and R 22 and R 23 The phase difference between the three-phase power phases is 120 degrees. When the three-phase voltages are basically the same, the three step-down circuits intersect to form a neutral point S0 with zero voltage. The rectifier diode D is connected in series between the neutral point S0 and the C pole of U1. 10 , voltage-dropping resistor R 21 And connector JP1, connector JP1 is used to control whether the three-phase common power supply is connected to U1. The output end of connector JP1 is equipped with a pull-down resistor R 24 , reducing the chance of interference falsely triggering U1.

[0040] The relay trigger circuit 13 includes an optocoupler U1, a transistor Q2, and a thyristor T1. The E pole of U1 is connected to the B pole of Q2 and the N line NN of the common power supply. The C pole of Q2 is connected to the gate of T1. One end of the relay K1 is connected to the A line NA of N, and the other end is connected in sequence to the rectifier full bridge circuit composed of rectifier diodes D5, D7, D8 and D9, T1 and the ground line to form a loop. A pull-down resistor R is connected between the gate of T1 and the ground line. 30 , reducing the chance of interference mis-triggering the gate of T1.

[0041] The trigger power supply circuit starts from NA and is connected in series with the voltage drop resistor R 12 、R 13 、R 14 and R 15 And the rectifier diode D6, after the rectifier diode D6, it is divided into two outputs, the first output is connected in series with the current limiting resistor R 29 Then connected to the E pole of U1, the second path passes through the series current limiting resistor R 11 Then connect it to the C pole of Q2.

[0042] like Figure 5 and Figure 6 The normally open contact and normally closed contact of the conversion contact of K1 are correspondingly connected to the normal power supply and the backup power supply, and the common end is connected to M1 through the load power supply circuit. K1 includes 3-way conversion contacts. The normally closed contact and normally open contact of the first conversion contact in the 3-way conversion contacts are correspondingly connected to the N line of the backup power supply and the N line of the normal power supply. The normally closed contact and normally open contact of the second conversion contact are respectively empty and connected to the A line of the normal power supply. The normally closed contact and normally open contact of the third conversion contact are respectively connected to the A line of the backup power supply and empty. The load power supply circuit includes 3 connection circuits respectively connected to the common ends of the 3-way conversion contacts.

[0043] An auxiliary switch is connected in series on each of the two-way connection circuits between the common end of the second and third transfer contacts and M1, wherein the auxiliary switch N_AUX is used to control and detect the opening and closing status of the normal power supply, and the auxiliary switch R_AUX is used to control and detect the opening and closing status of the backup power supply. An arc absorption circuit is connected between the two-way connection circuit connected to the second and third transfer contacts and the connection circuit connected to the first transfer contact, which is used to absorb the high-voltage arc generated when the transfer contacts of K1 are switched. The arc absorption circuit includes resistors R27 and R28 and non-polarized capacitors C3 and C4.

[0044] like Figure 4The simple PC-level dual power switch control circuit also includes two power indicator light power supply circuits with NA and RA as inputs respectively. The power indicator light power supply circuit of the normal power supply includes a rectifier diode D3, a voltage drop resistor R3, R7 and a light-emitting diode NPWR connected in series in sequence. The power indicator light power supply circuit of the standby power supply includes a rectifier diode D4, a voltage drop resistor R4, R8 and a light-emitting diode RPWR connected in series in sequence. When the normal power supply and the standby power supply are normal, both NPWR and RPWR are on. The power indicator light power supply circuit with NA as input also includes a transistor Q1 for cutting off NPWR. The C pole and E pole of Q1 are correspondingly connected to the positive pole and negative pole of NPWR. The B pole of Q1 is connected in series with a current-limiting resistor and then connected to the E pole of U1. When the normal power supply is phase-lost, the E pole of U1 has an output, Q1 is turned on and then cuts off NPWR, and NPWR goes out to indicate that the normal power supply is phase-lost to prevent false indication.

[0045] A voltage stabilizing filter circuit is also connected between the output end of the rectifier diode and the ground line. The voltage stabilizing filter circuit includes a pull-down resistor R 10 , Zener diode ZD1, electrolytic capacitor E2 and non-polar capacitor C1, a filter circuit is also connected between the E pole of U1 and the ground line, and the filter circuit includes a parallel pull-down resistor R 25 , electrolytic capacitor E1 and non-polar capacitor C2. Non-polar capacitors include mica, propylene or ceramic capacitors. The voltage regulator diode is used to stabilize the NA voltage of the C pole of Q2. The parallel electrolytic capacitor is used to reduce the noise generated by the voltage regulator diode. The electrolytic capacitor has a winding inductance and has a poor filtering effect on high-frequency noise. The non-polar capacitor has a small capacity and is used to filter out the high-frequency noise in NA, thereby fully bypassing the high-frequency and low-frequency components contained in NA, increasing the voltage regulation effect and reducing the probability of false triggering of Q2 as a whole. The overall circuit diagram of the simple PC-level dual power supply switch control circuit is as follows: Figure 7 .

[0046] like Figure 8The power supply fault detection circuit includes three step-down circuits connected to the three phases of the common power supply. The impedance of the three step-down circuits is the same and they are connected in parallel to form a neutral point. The relay trigger circuit includes an optocoupler U1, a transistor Q2 and a thyristor T1. The neutral point is connected to the input end of U1. The output end of the trigger power supply circuit is respectively connected to the C pole of U1, the C pole of Q2 and the gate of T1. The E pole of U1 is connected to the B pole of Q2. The common power supply, K1, T1 and the ground wire are connected in sequence to form a loop. When the common power supply is normal, the voltage of the neutral point is zero, U1 is not triggered, Q2 is turned off, and the gate of T1 is triggered by the trigger power supply circuit. The loop formed by the common power supply, K1, T1 and the ground wire is turned on, K1 is energized, and the first and second circuits are turned on. The common ends of the 2nd and 3rd switching contacts are connected to the normally open contacts respectively, and M1 is connected to the A line and N line of the normal power supply; when the A phase, B phase and C phase of the normal power supply are missing or lose voltage, the voltage of the neutral point is not zero, U1 is triggered, Q2 is turned on, the current of the triggering power supply circuit is cut off to the ground line, the gate of T1 is not triggered, and the loop formed by the normal power supply, K1, T1 and the ground line in sequence is not conductive. When one phase connected to K1 is missing, K1 is directly powered off. In short, when the normal power supply is missing or loses voltage, K1 is powered off. The common ends of the 1st, 2nd and 3rd switching contacts are connected to the normally closed contacts respectively, and M1 is connected to the A line and N line of the backup power supply to realize the conversion of M1 from the normal power supply to the backup power supply.

[0047] Load M1 is a motor that can rotate forward and reverse. An automatic / manual switch A / M is connected in series in the connection circuit between the common end of the first conversion contact and M1. When the automatic / manual switch is turned on, the neutral line of the motor is connected to the control neutral line, and the motor can rotate forward and reverse to automatically drive the mechanism conversion; when the automatic / manual switch is turned off, the neutral line of the motor is disconnected from the control neutral line, the motor cannot be powered, and can only be converted manually.

[0048] This embodiment proposes a simple PC-level dual-power supply switching switch control circuit, which implements the function of detecting phase loss and voltage loss of the normal power supply and the function of detecting voltage loss of the backup power supply. The backup power supply is not used when the normal power supply voltage is normal. The switch A / M for switching the motor between manual and automatic working modes is provided. Only one relay K1 is used to achieve dual power supply conversion. The circuit has a compact structure, small size, and low cost.

[0049] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A simple PC-grade dual-power switch control circuit, used to automatically switch to a backup power supply when the normal power supply for load M1 fails, comprising a relay drive circuit, a load power supply circuit, and a relay K1. The relay drive circuit includes a power failure detection circuit, a trigger power supply circuit, and a relay trigger circuit. The normally open contact and normally closed contact of the switching contact of the relay K1 are respectively connected to the normal power supply and the backup power supply, and the common end is connected to M1 through the load power supply circuit. The characteristics are: The power failure detection circuit includes three step-down circuits connected to the three phases of the common power supply. The three step-down circuits have the same impedance and are connected in parallel to form a neutral point. The relay trigger circuit includes an optocoupler U1, a transistor Q2, and a thyristor T1. The neutral point is connected to the input of the optocoupler U1. The output of the trigger power supply circuit is respectively connected to the C pole of the optocoupler U1, the C pole of the transistor Q2, and the gate of the thyristor T1. The E pole of the optocoupler U1 is connected to the B pole of the transistor Q2. The common power supply, relay K1, thyristor T1, and ground are connected in sequence to form a loop. The relay K1 includes three-way transfer contacts, wherein the normally closed contact and the normally open contact of the first transfer contact are respectively connected to the N line of the backup power supply and the N line of the normal power supply, the normally closed contact and the normally open contact of the second transfer contact are respectively vacant and connected to the A line of the normal power supply, and the normally closed contact and the normally open contact of the third transfer contact are respectively connected to the A line of the backup power supply and vacant. The load power supply circuit includes three connection circuits respectively connected to the common ends of the three transfer contacts; The dual power switch control circuit also includes two power indicator light power supply circuits with NA and RA as inputs respectively. The power indicator light power supply circuit includes a rectifier diode, a voltage drop resistor and a light-emitting diode connected in series in sequence. The power indicator light power supply circuit with NA as input also includes a transistor Q1 for cutting off the light-emitting diode. The C pole and E pole of the transistor Q1 are correspondingly connected to the positive pole and negative pole of the light-emitting diode, and the B pole of the transistor Q1 is connected in series with a current-limiting resistor and then connected to the E pole of the optocoupler U1.

2. A simple PC-grade dual power switch control circuit according to claim 1, characterized in that: The power failure detection circuit further includes a step-down rectifier circuit between the neutral point and the input end of the optocoupler U1. The step-down rectifier circuit includes a rectifier diode, a step-down resistor and a connector JP1 connected in series. The output end of the connector JP1 is provided with a pull-down resistor.

3. The simplified PC-grade dual power switch control circuit according to claim 1, characterized in that: The trigger power supply circuit includes a voltage-dropping resistor and a rectifier diode connected in series. The trigger power supply circuit is divided into two outputs after passing through the rectifier diode. The first output is connected to the C pole of the optocoupler U1 after being connected in series with a current-limiting resistor, and the second output is connected to the C pole of the transistor Q2 after passing through the current-limiting resistor.

4. The simplified PC-grade dual power switch control circuit according to claim 3, characterized in that: A voltage stabilizing filter circuit is also connected between the output end of the rectifier diode and the ground line. The voltage stabilizing filter circuit includes a pull-down resistor, a voltage stabilizing diode, an electrolytic capacitor and a non-polarized capacitor connected in parallel.

5. The simplified PC-grade dual power switch control circuit according to claim 1, characterized in that: An automatic / manual switch is connected in series to the connection circuit between the common end of the first switching contact and M1, and an auxiliary switch is connected in series to each of the two connection circuits between the common end of the second and third switching contacts and M1.

6. The simplified PC-grade dual power switch control circuit according to claim 1, characterized in that: An arc absorption circuit is connected between the 2-way connection circuit connected to the 2nd and 3rd switching contacts and the connection circuit connected to the 1st switching contact. The arc absorption circuit includes a resistor and a non-polar capacitor connected in series.

7. The simplified PC-grade dual power switch control circuit according to claim 1, characterized in that: A rectifier full-bridge circuit is connected in series between the relay K1 and the thyristor T1, and a pull-down resistor is connected between the gate of the thyristor T1 and the ground line.

8. The simplified PC-grade dual power switch control circuit according to claim 1, characterized in that: A filter circuit is further connected between the E pole of the optical coupler U1 and the ground line. The filter circuit includes a pull-down resistor, an electrolytic capacitor and a non-polar capacitor connected in parallel.

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