Surge suppression circuit

Abstract

The utility model discloses a surge suppression circuit, the circuit is used for suppressing surge current, the circuit comprises an AC power supply and a connection circuit, the connection circuit comprises a bridge rectifier diode, an IC circuit board, a first capacitor, a load device, a relay, a fuse, and a fifth diode. And the output end of the alternating current power supply is used as a starting point of the circuit. The connecting circuit comprises an IC circuit board, the IC circuit board is provided with four connecting ports, a phase line of an alternating current power supply is simultaneously connected with one end of the fuse and an HV port of the IC circuit board, the other end of the fuse is connected with the bridge rectifier diode, a third connecting end of the relay is simultaneously connected with a null line of the alternating current power supply, and a fourth connecting end of the relay is connected with a null line of the alternating current power supply. The relay is controlled by the IC to be closed at the voltage zero crossing point of the alternating current power supply, the voltage difference between the alternating current power supply and the connecting circuit is reduced, the surge current is further reduced, the fuse is prevented from being broken down and the rectifier bridge is prevented from being damaged due to overlarge surge current, and the overall operation reliability of the circuit is further improved.

Description

Technical Field

[0001] The utility model relates to the technical field of circuits, in particular to a surge suppression circuit. Background Art

[0002] With the rapid development of industrial manufacturing, people have higher and higher requirements for the reliability of circuit operation. The existing switching power supply usually includes a large capacitor as a filter capacitor. Before the switching power supply is connected to the public power grid, the voltage at the input end of the switching power supply is zero. When the switching power supply is connected to the public power grid, due to the existence of the voltage difference, the public power grid will charge the filter capacitor and generate a large surge current. The switching power supply usually also includes a rectifier bridge and a fuse. Excessive surge current may cause the rectifier bridge and the fuse to break down, affecting the safety and reliability of the use of the switching power supply. In order to solve the existing problems, the existing technology is to set an NTC (Negative Temperature Coefficient, negative temperature coefficient, referred to as NTC) resistor at the input end of the switching power supply. When the switching power supply is connected to the public power grid, the temperature of the NTC resistor is low, so the NTC resistance value is relatively large, and it has a good ability to suppress surge current. However, after the switching power supply has been working for a period of time, the temperature of the NTC rises and the resistance value begins to decrease. Therefore, re-plugging in the case of a hot engine has limited effect on suppressing the surge current, and it will also bring additional losses. The existing surge suppression circuit has the problem of poor effect on suppressing the surge current and additional circuit losses. Utility Model Content

[0003] The utility model discloses a surge suppression circuit, aiming to overcome the problems of poor surge current suppression effect and extra circuit loss in the existing surge suppression circuit.

[0004] The utility model discloses a surge suppression circuit, wherein the circuit is used to suppress surge current, the circuit comprises an AC power supply and a connection circuit, the connection circuit comprises: a bridge rectifier diode, an IC circuit board, a first capacitor, a load device, a relay, a fuse, a fifth diode and a second capacitor, the output end of the AC power supply serves as the starting point of the circuit, the phase line of the AC power supply is simultaneously connected to one end of the fuse and the HV port of the IC circuit board, the other end of the fuse is connected to the first connection end of the bridge rectifier diode, the second connection end of the bridge rectifier diode is simultaneously connected to one end of the first capacitor and the current input end of the load device, the fourth connection end of the bridge rectifier diode is simultaneously connected to the other end of the first capacitor and the current input end of the load device, the third connection end of the bridge rectifier diode is simultaneously connected to the first connection end of the relay, the second connection end of the relay is connected to the G port of the IC circuit board, the third connection end of the relay is simultaneously connected to the neutral line of the AC power supply, one end of the second capacitor and the grounding end of the IC circuit board, and the other end of the second capacitor is connected to the Vcc port of the IC circuit board.

[0005] A surge suppression circuit, wherein the bridge rectifier diode comprises a first diode, a second diode, a third diode, and a fourth diode, wherein the first diode is arranged in series between a first connection end and a second connection end of the bridge rectifier diode, the second diode is arranged in series between the second connection end and the third connection end of the bridge rectifier diode, the third diode is arranged in series between the third connection end and the fourth connection end of the bridge rectifier diode, and the fourth diode is arranged in series between the first connection end and the fourth connection end of the bridge rectifier diode, the anode of the first diode is connected to one end of the fuse and the cathode of the second diode, the anode of the second diode is simultaneously connected to the cathode of the third diode and the first connection end of the relay, and the anode of the third diode and the anode of the fourth diode are simultaneously connected to the current input end of the load device.

[0006] A surge suppression circuit, wherein the capacitance of the first capacitor is 68-300uF.

[0007] A surge suppression circuit, wherein the output voltage of the AC power supply ranges from 90 to 264V.

[0008] A surge suppression circuit, wherein the relay is a normally open relay.

[0009] A surge suppression circuit, wherein the time for the impedance to drop from 5Ω to 0Ω during the relay pickup process is greater than 300us.

[0010] A surge suppression circuit, wherein the capacitance of the second capacitor is 4.7-220uF.

[0011] Compared with the prior art, the utility model has the following advantages:

[0012] The utility model discloses a surge suppression circuit, the circuit is used to suppress surge current, the circuit comprises an AC power supply and a connection circuit, the connection circuit comprises: a bridge rectifier diode, an IC circuit board, a first capacitor, a load device, a relay, a fuse, and a fifth diode, the output end of the AC power supply serves as the starting point of the circuit, the connection circuit comprises an IC circuit board, the IC circuit board is provided with four connection ports, the phase line of the AC power supply is simultaneously connected to one end of the fuse and the HV port of the IC circuit board, the other end of the fuse is connected to the bridge rectifier diode, the third connection end of the relay is simultaneously connected to the zero line of the AC power supply, the relay is controlled by the IC to be attracted at the zero point of the AC power supply voltage, the voltage difference between the AC power supply and the connection circuit is reduced, and the surge current is reduced, and the surge current is effectively prevented from being too large to break through the fuse and damage the rectifier bridge, thereby improving the reliability of the overall operation of the circuit; and when the circuit is stably running, the relay is completely attracted, the impedance is zero, and the loss caused by the traditional solution is eliminated. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0014] Figure 1 An overall circuit diagram of a surge suppression circuit provided by an embodiment of the utility model;

[0015] Figure 2 A relay characteristic curve diagram of a surge suppression circuit provided by an embodiment of the utility model;

[0016] Figure 3 A voltage variation spectrum of each time period during the surge current suppression process performed by an IC circuit board of a surge current suppression circuit provided by an embodiment of the utility model.

[0017] Figure numerals: connecting circuit S1, load device RL, IC circuit board U1, relay K, fuse F; AC power supply AC, first capacitor C1, second capacitor C2; bridge rectifier diode BD, first diode D1, second diode D2, third diode D3, fourth diode D4, fifth diode D5. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0020] It should also be understood that the terms used in the utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in the utility model specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0021] It should be further understood that the term “and / or” used in the present specification and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0022] See also Figure 1 , as shown in the figure, Figure 1The circuit disclosed in the utility model is used to suppress surge current. The circuit includes an alternating current power supply AC and a connecting circuit S1. The connecting circuit S1 includes: a bridge rectifier diode BD, an IC circuit board U1, a first capacitor C1, an alternating current power supply AC, a relay K, a fuse F, and a fifth diode D5. The output end of the alternating current power supply AC serves as the starting point of the circuit. The phase line of the alternating current power supply AC is simultaneously connected to one end of the fuse F and the HV port of the IC circuit board U1. The other end of the fuse F is connected to the first connection end of the bridge rectifier diode BD. The second connection end of the bridge rectifier diode BD is simultaneously connected to the first connection end of the bridge rectifier diode BD. One end of a capacitor C1 and the current input end of the load device RL, the fourth connection end of the bridge rectifier diode BD is simultaneously connected to the other end of the first capacitor C1 and the current input end of the load device RL, the third connection end of the bridge rectifier diode BD is simultaneously connected to the first connection end of the relay K, the second connection end of the relay K is connected to the G port of the IC circuit board U1, the third connection end of the relay K is simultaneously connected to the neutral line of the AC power supply AC, one end of the second capacitor C2 and the ground end of the IC circuit board U1, and the other end of the second capacitor C2 is connected to the Vcc port of the IC circuit board U1.

[0023] Specifically, in the embodiment of the present scheme, the circuit is used to suppress the surge current in the rectifier diode BD and the fuse F. An IC circuit board U1 is set on one side of the AC power supply AC. The circuit board is electrically connected to the AC power supply AC, and the relay K is controlled through the four connection ports on the circuit board. In one embodiment, the four connection ports included in the IC circuit board U1 are (G port, HV port, GND port, Vcc port), wherein the G port is connected to one end of the relay K to control the third connection end of the bridge rectifier diode BD. When it is detected that the AC voltage of the AC power supply AC passes through zero, the voltage difference between the voltage of the AC power supply AC and the first capacitor C1 is zero, and the switch of the control relay K is opened to connect the third connection end of the bridge rectifier diode BD to the neutral line of the AC power supply AC, and the surge current is minimized. Furthermore, in one embodiment, relay K is connected in series to the N line, and is a normally open relay K. The functions of HV PIN are high voltage startup and AC voltage phase detection. Vcc pin is a power supply PIN pin, and starts working after reaching a certain voltage. HV pin is connected through a diode, and Vcc is charged only when the LN voltage is positive. GND pin is the GND of the IC circuit board with the N line as the ground reference point. G is the driving pin of relay K. When the HV pin detects that the voltage passes through zero, that is, point B, a high level is generated, driving relay K to close. At this time, the voltage difference between the AC power supply AC and the first capacitor C1 is zero, and the surge current generated is minimal, which greatly reduces the risk of damage to the rectifier diode BD and the fuse F.

[0024] Further, in one embodiment, see Figure 1 As shown in the figure, the IC circuit board U1 includes an HV pin, which has the functions of high-voltage startup and AC voltage zero-crossing detection. On the one hand, the HV pin is connected to the phase line of the AC power supply through the fifth diode D5. When the phase line voltage to the neutral line is positive, the Vcc pin is charged through the HV Pin to generate a Vcc voltage, so that the IC circuit board U1 works normally. On the other hand, the HV pin is connected to the phase line of the AC power supply through the fifth diode D5 to realize the function of monitoring the AC voltage. When the IC circuit board U1 detects that the AC voltage crosses zero, the G pin is controlled to output a high level, and the relay K is controlled to be attracted, so that the relay is attracted when the instantaneous value of the AC voltage is zero. Then, the voltage difference between the AC power supply and the first capacitor C1 is minimized, and the surge current generated is minimized, thereby reducing the risk of damage to the fuse F and the rectifier bridge.

[0025] See also Figure 1As shown in the figure, the bridge rectifier diode BD includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The first diode D1 is connected in series between the first connection end and the second connection end of the bridge rectifier diode BD, the second diode D2 is connected in series between the second connection end and the third connection end of the bridge rectifier diode BD, the third diode D3 is connected in series between the third connection end and the fourth connection end of the bridge rectifier diode BD, and the fourth diode D4 is connected in series between the first connection end and the fourth connection end of the bridge rectifier diode BD. The anode of the first diode D1 is connected to one end of the fuse F and the cathode of the second diode D2, the anode of the second diode D2 is connected to the cathode of the third diode D3 and the first connection end of the relay K at the same time, and the anode of the third diode D3 and the anode of the fourth diode D4 are connected to the current input end of the load device RL at the same time.

[0026] Specifically, in the embodiment of the present scheme, the bridge rectifier diode BD includes four diodes (a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4), the first diode D1 is arranged in series between the first connection end and the second connection end of the bridge rectifier diode BD, the second diode D2 is arranged in series between the second connection end and the third connection end of the bridge rectifier diode BD, the third diode D3 is arranged in series between the third connection end and the fourth connection end of the bridge rectifier diode BD, and the fourth diode D4 is arranged in series between the first connection end and the fourth connection end of the bridge rectifier diode BD. And the fourth connection end, in one embodiment, the first capacitor C1 (filter capacitor) and the current input end of the load device RL are respectively arranged between the first connection end and the third connection end of the rectifier bridge, and the relay K, the fuse F and the IC circuit board U1 are used in conjunction with each other. When it is detected that the AC power supply AC voltage passes through zero, the voltage difference between the voltage of the AC power supply AC and the first capacitor C1 is zero. The relay K switch is controlled to open so that the third connection end of the bridge rectifier diode BD is connected to the zero line of the AC power supply AC, generating a minimum surge current, effectively suppressing the surge current, and preventing the surge current from damaging the rectifier diode and the fuse.

[0027] See also Figure 1 As shown in the figure, the time for the impedance to drop from 5Ω to 0Ω during the closure process of the relay K is greater than 300us.

[0028] Furthermore, the time for the impedance to drop from 5Ω to 0Ω during the energizing process of relay K is greater than 300us. In one embodiment, the impedance of the contact point of relay K changes slowly from infinity to 0. For example, when relay K is energized, the process of dropping from 5Ω (ohms) to 0Ω lasts for more than 300us as shown in the figure (t2-t1). Note: Because the power supply voltage is generally 100Vac or 240Vac, for a power supply voltage of 240Vac, considering a 10% voltage fluctuation, the maximum voltage is 264Vac. If a 5Ω (ohm) resistor is connected at the peak of 264Vac, i.e. 373VDC, the peak current is 75A, which meets the inrush current requirement of a conventional rectifier bridge. The time is counted starting from the resistance value of 5Ω. Please refer to Figure 2 ,like Figure 2 As shown, Figure 2 The first image in the figure is the voltage variation curve of the relay coil drive voltage (VG). Figure 2 The second image in the figure is the change curve of the impedance Z between the relay contacts. The time node t0 is the time node when no impact current occurs. In the 0-t0 time period, the relay switch is not turned on yet. At t0, the relay K coil drive voltage is high level, and the control contact is closed. In the t0-t1 time period, the impedance between the relay contacts drops rapidly, but the impedance between the relay contacts is large at this time, and no obvious impact current will be generated. In the t2-t1 time period, the impedance between the relay contacts is small, corresponding to the transition time of the impact current. The time difference t2-t1 should be greater than the time when the filter capacitor charges from 0 voltage to the AC voltage peak. In this way, the impact current can be maintained at a low value, reducing the current tolerance requirements for the bridge rectifier diode BD, greatly reducing the operation failure rate, and also greatly reducing the additional circuit loss, and improving the overall reliability of the circuit electrical connection.

[0029] Further, in one embodiment, the current specification of the fuse F is: 3.15A ~ 10A. When the output end of the alternating current power supply AC generates a surge current, the surge current at this time refers to the peak current caused by the instantaneous charging of the capacitor when the input voltage of the alternating current power supply AC is connected, the initial voltage of the first capacitor C1 is zero, there is a voltage difference between the two ends, and the peak current is related to the instantaneous voltage of AC connection and the capacitance of C1. For example, when the AC voltage is at the upper limit voltage of 264Vac, the maximum value of the AC transient voltage is 264V×1.414=373V. If the initial voltage connected at this time is 0V, the first capacitor C1 with a capacitance of 100uF generates a surge current peak of about 100A. This surge current may cause damage to the rectifier diode BD and the fuse F. If the relay K is controlled by the IC circuit board U1 to be attracted at the zero point of the AC voltage, the voltage difference between the voltage of the alternating current power supply AC and the first capacitor C1 is zero, thereby effectively suppressing the generation of surge current, avoiding the loss of the fuse due to surge current, and improving the reliability of the overall operation of the circuit.

[0030] See also Figure 1 , as shown in the figure, wherein the capacitance of the first capacitor C1 is 68~300uF.

[0031] Specifically, the capacitance of the first capacitor C1 is 68 to 300uF. In one embodiment, the first capacitor C1 is provided to filter the current flowing through one side of the bridge rectifier diode BD. The first capacitor C1 is a filter capacitor as a whole. The filter capacitor is usually an electrolytic capacitor, and the electrolytic capacitor usually includes an equivalent series resistor, whose resistance has a certain inhibitory effect on the surge current. Generally, the larger the capacitance of the electrolytic capacitor, the smaller the equivalent series resistance. When the AC power supply is connected to the connection circuit, the larger the capacitance, the smaller the equivalent series resistance, the greater the impact current generated under the same voltage difference, and the higher the current carrying capacity requirement of the fuse F and the rectifier bridge. When the relay F is not energized, the impedance between the contacts of the relay F is infinite, and no impact current is generated. When the relay F starts to work, the AC power supply is connected to the circuit to generate an impact current, but by controlling the relay to be energized when the AC voltage passes through zero, the voltage difference between the instantaneous voltage of the AC power supply and the first capacitor is reduced, thereby effectively reducing the impact current and reducing the current carrying capacity requirement of the fuse and the rectifier bridge. Please refer to Figure 1 ,like Figure 1 As shown, the output voltage range of the alternating current power supply AC is 90 to 264V.

[0032] Specifically, the output voltage of the AC power source AC ranges from 90 to 264V. Since the voltage is an AC output, the traditional solution needs to consider the impact current caused by the AC voltage at the peak. For example, when the AC output voltage is the maximum value of 264V, the peak voltage is 264V×1.414, that is, 373V. When it is connected to the connection circuit, it will generate a large impact current. If the patented technology is adopted, by adding a relay and an IC circuit board to monitor the instantaneous value of the AC voltage, the control relay is closed when the AC voltage passes through the zero point. In this way, when the instantaneous value of the AC voltage is zero, the voltage difference between the connection circuit and the first capacitor is zero, so the impact current generated is minimal, thereby reducing the risk of damage to the fuse and the rectifier bridge.

[0033] See also Figure 1 , as shown in the figure, wherein the relay K is a normally open relay.

[0034] Specifically, the relay K is a normally open relay, which is equivalent to a control switch. When the relay is not energized, the impedance between the relay contacts is infinite, which is a normally open state. When the relay is fully energized, the impedance between the relay contacts is zero. By adding a normally open relay, the moment when the AC power source is connected to the connection circuit is controlled, and then the instantaneous voltage of the AC power source is controlled, and the voltage difference between the AC power source and the first capacitor is controlled, and then the inrush current is controlled. Furthermore, if the relay is energized when the instantaneous value of the AC voltage is zero, the voltage difference between the AC power source and the first capacitor is minimized, and the generated inrush current is minimized, thereby reducing the risk of damage to the fuse and the rectifier bridge.

[0035] See also Figure 1 , as shown in the figure, wherein the capacitance of the second capacitor C2 is 4.7~220uF.

[0036] Specifically, the capacitance of the second capacitor C2 is 4.7~220uF. In one embodiment, one end of the second capacitor C2 is set on the Vcc pin of the IC circuit board, and the other end is set on the neutral line of the AC power supply and the reference ground of the IC circuit board. The IC circuit board charges the Vcc pin set on one side of the IC circuit board through the HVpin port set on one side, and stores energy at both ends of the second capacitor C2. When the AC voltage is detected to pass through zero, the G pin outputs a high level to control the relay to be attracted, but sufficient energy is required to drive the relay coil to be attracted, and this energy is provided by the energy stored in the second capacitor C2.

[0037] See also Figure 3 , as shown in the figure, Figure 3 It is the change curve of the AC power supply in each period of the overall voltage output, where the horizontal axis is the time node (t). Figure 3 The vertical coordinate of the first image in is (control voltage Vac), Figure 3The vertical coordinate of the second image in is (supply voltage Vcc), Figure 3 The vertical coordinate of the third image in the figure is (differential input voltage Vg). Further, in one embodiment, the control process executed by the IC circuit board U1 is as follows: (1) When the VAC voltage is in a positive phase, the high voltage startup is performed through the HV PIN to charge Vcc; (2) When the power output terminal (Vcc) in the circuit reaches the starting voltage (Vstart), the IC circuit board U1 starts to work; (3) When it is detected that the Vac voltage crosses zero, the G pin outputs a high level, controls the relay K to attract, and reduces the voltage difference between the AC (alternating current power supply AC) and the DC (direct current power supply, not shown in the figure).

[0038] The utility model discloses a surge suppression circuit, the circuit is used to suppress surge current, the circuit comprises an AC power supply and a connection circuit, the connection circuit comprises: a bridge rectifier diode, an IC circuit board, a first capacitor, a load device, a relay, a fuse, and a fifth diode, the output end of the AC power supply serves as the starting point of the circuit, the connection circuit comprises an IC circuit board, the IC circuit board is provided with four connection ports, the phase line of the AC power supply is simultaneously connected to one end of the fuse and the HV port of the IC circuit board, the other end of the fuse is connected to the bridge rectifier diode, the third connection end of the relay is simultaneously connected to the zero line of the AC power supply, the relay is controlled by the IC to be attracted at the zero point of the AC power supply voltage, the voltage difference between the AC power supply and the connection circuit is reduced, and the surge current is reduced, and the surge current is effectively prevented from being too large to break through the fuse and damage the rectifier bridge, thereby improving the reliability of the overall operation of the circuit, and when the circuit is stably running, the relay is completely attracted, the impedance is zero, and the loss caused by the traditional solution is eliminated.

[0039] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A surge suppression circuit, characterized in that: The circuit is used to suppress surge current. The circuit includes an AC power supply and a connecting circuit. The connecting circuit includes: a bridge rectifier diode, an IC circuit board, a first capacitor, a load device, a relay, a fuse, a fifth diode and a second capacitor. The output end of the AC power supply serves as the starting point of the circuit. The phase line of the AC power supply is simultaneously connected to one end of the fuse and the HV port of the IC circuit board. The other end of the fuse is connected to the first connection end of the bridge rectifier diode. The second connection end of the bridge rectifier diode is simultaneously connected to one end of the first capacitor and the current input end of the load device. The fourth connection end of the bridge rectifier diode is simultaneously connected to the other end of the first capacitor and the current input end of the load device. The third connection end of the bridge rectifier diode is simultaneously connected to the first connection end of the relay. The second connection end of the relay is connected to the G port of the IC circuit board. The third connection end of the relay is simultaneously connected to the neutral line of the AC power supply, one end of the second capacitor and the grounding end of the IC circuit board. The other end of the second capacitor is connected to the Vcc port of the IC circuit board.

2. A surge suppression circuit according to claim 1, characterized in that: The bridge rectifier diode includes a first diode, a second diode, a third diode, and a fourth diode. The first diode is arranged in series between the first connection end and the second connection end of the bridge rectifier diode, the second diode is arranged in series between the second connection end and the third connection end of the bridge rectifier diode, the third diode is arranged in series between the third connection end and the fourth connection end of the bridge rectifier diode, and the fourth diode is arranged in series between the first connection end and the fourth connection end of the bridge rectifier diode. The anode of the first diode is connected to one end of the fuse and the cathode of the second diode, the anode of the second diode is simultaneously connected to the cathode of the third diode and the first connection end of the relay, and the anode of the third diode and the anode of the fourth diode are simultaneously connected to the current input end of the load device.

3. A surge suppression circuit according to claim 1, characterized in that: The capacitance of the first capacitor ranges from 68uF to 300uF.

4. A surge suppression circuit according to claim 1, characterized in that: The output voltage of the AC power supply ranges from 90 to 264V.

5. A surge suppression circuit according to claim 1, characterized in that: The relay is a normally open relay.

6. A surge suppression circuit according to claim 1, characterized in that: The time for the impedance to drop from 5Ω to 0Ω during the relay closing process is greater than 300us.

7. A surge suppression circuit according to claim 1, characterized in that: The capacitance of the second capacitor is 4.7-220uF.

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