Protection circuit for lightning surge

Abstract

The invention provides a protection circuit for a lightning surge. The protection circuit is formed by connecting a first bleeder circuit with a noise filtering circuit; the first bleeder circuit is formed by connecting a voltage dependent resistor MOV1 with a resistor R1, wherein the resistor R1 is connected to the position behind the voltage dependent resistor MOV1 in series; the voltage dependent resistor MOV1 is used for providing a low-resistance bleeder channel for impulse currents generated by the lightning surge; the resistor R1 is used for increasing input impedance, so that more impulse currents are bled by the voltage dependent resistor MOV1; the noise filtering circuit is formed by connecting a differential mode inductor L1 with a safety capacitor CX, wherein the differential mode inductor L1 is connected to the position in front of the safety capacitor CX in series; when the lightning surge generates the impulse currents, the noise filtering circuit is used for further filtering residual voltage peaks of the first bleeder circuit; when noise of a next-stage circuit is transmitted forwards, the noise filtering circuit is used for filtering the noise of the next-stage circuit. Compared with the prior art, the protection circuit has the advantages that damage of the lighting surge to a switch power supply in actual use is significantly reduced, and the electromagnetic compatibility (EMI) performance of the switch power supply can be improved.

Description

technical field [0001] The invention relates to the field of lightning surge protection for switching power supplies, in particular to a lightning surge protection circuit for switching power supplies. Background technique [0002] Switching power supply has a wide range of applications in industry, especially the AC-DC switching power supply connected to the mains, which is often used as a primary power supply to provide a stable bus voltage for the subsequent system. Since the AC-DC switching power supply is connected to the mains, the mains is often affected by some natural factors (such as lightning strikes) and application environments (such as the opening or closing of large inductive or capacitive loads on the mains). break), thus generating an instantaneous voltage or current peak, superimposed on the mains, causing great harm to the AC-DC switching power supply. The existing AC-DC switching power supply will add a lightning surge protection circuit at the input end...

AI Technical Summary

Problems solved by technology

Since the AC-DC switching power supply is connected to the mains, the mains is often affected by some natural factors (such as lightning strikes) and application environments (such as the opening or closing of large inductive or capacitive loads on the mains). break), resulting in an instantaneous voltage or current peak, superimposed on the mains, causing great harm to the AC-DC switching power supply

The existing AC-DC switching power supply will add a lightning surge protection circuit at the input end to suppress this part of the hazard and ensure the safe and reliable use of the product. However, adding this part of the circuit will inevitably increase the number of components, resulting in an increase in cost. The higher the surge protection requirements, the more devices are added, and the higher the cost

[0003] The lightning surge protection circuit of the prior art is as figure 1 As shown, including varistor MOV, safety X capacitor CX, differential mode inductor LDM, and common mode inductor LCM, these circuits have the functions of lightning surge current suppression and electromagnetic interference suppression, but the effect of this protection circuit is not particularly ideal. For example using figure 1 A 3W prototype of the lightning surge protection circuit in the prior art shown in the prior art can withstand a surge voltage of 2kV, and the electromagnetic interference level only meets the requirements of CLASSA, but if it wants to withstand a surge voltage of 4kV or higher, it needs to meet higher requirements. To meet the level of electromagnetic interference, it is necessary to double the differential mode inductance and common mode inductance, or to use multi-level protection to have a better suppression effect, but this will cause an increase in cost and volume

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