Hardware knowledge: lightning surge test of switching power supply adapter

The national standard for the lightning surge immunity test of switching power supply adapters is GB/T17626.5. There were two versions in China in 1999 and 2008, which are in line with the international standards IEC61000-4-5:1995 and IEC61000-4-5 respectively. :2001 is equivalent. Since most domestic product standards have not been revised, the two standards, GB/T17626.5-1999 and GB/T17626.5-2008, coexist in China.

Lightning strikes are an extremely common natural phenomenon. According to statistics, there are more than 40,000 thunderstorm centers in the world, and there are 8 million lightning strikes every day, which means that there are about 100 lightning strikes on the earth every second. Therefore, the anti-lightning surge test of the switching power supply adapter can establish a common basis for evaluating the switching power supply when it suffers from high-energy pulse interference.

The standard mainly simulates indirect lightning strikes (switching power supplies are usually unable to withstand direct lightning strikes), such as: ① lightning strikes an outdoor power grid line, a large amount of current flows into the external line or grounding resistance, thus generating interference voltage; ② indirect lightning strike (such as Lightning strikes between or within clouds) induce pulse voltages and currents on external power grid lines; ③Thunder and lightning strikes nearby objects on the line, and a strong electromagnetic field is established around them, which induces voltage on external lines; ④Lightning strikes nearby ground, The interference introduced when the ground current passes through the public grounding system. For details, please refer to the news of Guangzhou Tianjia Technology Co., Ltd.

In addition to simulating lightning strikes in the natural world, the surge immunity test standard of power adapters also mentions the interference introduced by switching actions in substations and other occasions, such as: ①interference when the main power system is switched; ②the same Power grid, interference formed when some small switches near the switching power adapter jump; ③switching of thyristor equipment with resonance circuit; ④various systemic faults, such as equipment grounding network or short circuit and arcing faults between grounding systems .

1. Lightning surge immunity test method:

⑴ Layout and configuration according to the actual use and installation conditions of the test product, including some standards that will change the additional resistance that reflects the internal resistance of the waveform generator signal source.

⑵According to product requirements to determine the test voltage level and test location.

(3) On each selected test site, the positive and negative polarity interference should be added at least 5 times each, and the maximum repetition rate of each surge is 1 time/min. Because most of the protection devices used in systems have a recovery period between two surges, there is a problem of maximum repetition rate when the equipment is subjected to a lightning surge test.

⑷Whether the injection of the surge wave should be synchronized with the input voltage of the switching power supply adapter. If there are no special regulations, it is usually required to superimpose the lightning surge signal on the zero-crossing point and the position of the positive and negative peaks of the voltage waveform of the switching power supply adapter.

⑸Considering the nonlinearity of the voltage-current conversion characteristics of the equipment under test, the test voltage should be gradually increased to the specified value of the product standard to avoid possible false appearances in the test (at high test voltage, because of the It is possible that a weak device has broken down, bypassing the test voltage and making the test pass. However, when the test voltage is low, since the weak device has not been broken down, the test voltage is applied to the test equipment at full voltage, which makes the test Unable to pass). For details, please refer to the news of Guangzhou Tianjia Technology Co., Ltd.

⑹The lightning surge signal should be added between line-line or line-ground. If the line-to-earth test is to be carried out, and there are no special regulations, the test voltage shall be applied between each line and the ground in turn. But pay attention: When doing a line-to-ground test, sometimes the standard requires that interference be superimposed on two or more lines to the ground at the same time. At this time, the pulse duration is allowed to be reduced.

⑺As the test may be destructive, never let the test voltage exceed the specified value.

2. Lightning surge immunity test level:

The severity level of the test is divided into 1, 2, 3, 4 and X levels. The level 1 parameters of the power cord differential mode test are not given, and the remaining levels are 0.5kV, 1kV, 2kV and to be determined. The various parameters of the power cord common mode test are 0.5kV, 1kV, 2kV, 4kV and to be determined.

The severity level of the test depends on the environment (environment that may suffer from surge) and installation conditions, and is roughly classified as follows.

Level 1: A well-protected environment, such as the control room of a factory or power station.

Level 2: A certain protected environment, such as a factory without strong interference.

Level 3: Ordinary electromagnetic disturbance environment, no special installation requirements are specified for equipment, such as ordinary installation of cable networks, industrial workplaces and substations.

Level 4: Environments subject to severe harassment, such as civil overhead lines and unprotected high-voltage substations.

X level: special level, determined by the user and the manufacturer after negotiation.

During the EMC test of the switching power supply adapter, the lightning surge test level is: level 2 between line and line, and level 3 between line and ground.