Test design of lightning surge immunity test in electronic devices

When a lightning strike occurs, when the electronic equipment is transmitted along the power line or signal line, the strong current and its generated electromagnetic pulse can generate overvoltage through conduction, induction, coupling and other ways, forming a lightning surge. Generally, lightning will sense the high voltage on the exposed power line, which will not only be directly transmitted to the equipment, but also when the power line conducts, the electromagnetic induced surge will be coupled with the surrounding signal line. This surge will cause great damage to electronic products, so the products need to have certain surge anti-interference capability.

1、 Concept

Lightning surge immunity mainly refers to the immunity of electrical and electronic equipment to unipolar surge (impact) caused by switching and lightning transient overvoltage.

2、 Test purpose

Establish a common benchmark to evaluate the performance of electrical and electronic equipment in surge. Generally, the laboratory test is to simulate the impact of lightning interference on the equipment. Surge is the rapid rise and fall of current or voltage along the power line or signal line.

1. Power system switching transient:

(1) Resonance phenomenon related to switching devices (such as thyristor);

(2) Distribution system with small local switch action or load change;

(3) Main switching disturbance of power system, such as capacitor switching;

(4) The equipment combination has various system faults such as short circuit to the grounding system, arc fault, etc.

2. Lightning transient:

(1) Direct lightning, which strikes the external circuit, and the voltage generated by the injected large current through the grounding resistance or external circuit impedance;

(2) When the nearby is coupled to the common path of the combined grounding system of the equipment, the lightning current directly discharging to the ground nearby generates the induced voltage;

(3) Indirect lightning (that is, electromagnetic field generated by lightning strikes between or in clouds or nearby objects) generates induced voltage and current on the inside and outside conductors of buildings.

3. Classification of lightning levels

●LPZ0A area: all objects in this area may be directly struck by lightning, resulting in all lightning currents; The electromagnetic field strength in the region has not been attenuated.

●LPZ0B area: objects in the area cannot be directly struck by lightning current corresponding to the selected rolling radius, but the electromagnetic field strength in the area does not decay.

●LPZ1 area: all objects in this area cannot be directly struck by lightning, and the proportion of current flowing through various conductors cannot be directly struck by lightning. LPZ0B area is small; According to the shielding measures, the electromagnetic field intensity in this area may be attenuated.

●LPZ2 subsequent lightning protection zone: when it is necessary to further reduce the current and electromagnetic field strength, the subsequent lightning protection zone shall be added, and the requirements of the subsequent lightning protection zone shall be selected according to the environmental area to be protected.

3、 Test configuration

1. Combined wave generator, coupling/decoupling network and other auxiliary equipment.

2. The combined wave generator is divided into 10/700 μ S and 1.2/50 μ S, corresponding to different port types.

3. Classification

The surge immunity test is divided into:

(1) Surge voltage immunity test (open circuit voltage)

(2) Surge current immunity test (short circuit current)

Note: Surge immunity test simulates indirect lightning stroke, and does not consider direct lightning stroke or direct lightning stroke EUT insulation capacity high-voltage withstand test.

4、 Specific test waveform

1.1.2/50 μ S waveform introduction

1) Circuit schematic diagram of combined wave generator

2) Specific waveform

2.10/70 μ S waveform introduction

1) Circuit schematic diagram of combined wave generator

2) Specific waveform

3. Applicable scope of two kinds of surge signals:

(1) 10/7000 communication network and long-distance signal circuit port are recommended μ S shock wave. Common electronic devices, such as RJ45, RS232, XDSL, RS485, security cameras, etc.

(2) It is recommended to use 1 AC/DC power port and short distance signal circuit port. 2/50 μ S shock wave. Common electronic equipment, such as common electronic equipment, such as LED lighting equipment, base station, etc.

5、 Wave resistance test of common equipment ports

1. Subdivision drawing of lightning protection area

2. Recommended protection grade of each interface

The above is my personal interpretation of the lightning surge immunity standard. I hope it can deepen your understanding of the standard and also help design and rectification.