Switching power supply lightning surge immunity test - Database & Sql Blog Articles

Test - lowercase jpg

Kaixin micro test

Test probe P100-M3

1 Introduction

In the anti-electromagnetic interference assessment of switching power supplies, the ability to resist lightning surge is an indispensable indicator.
It is well known that the lightning surge immunity test is also called the pulse impact test, which is used to test the performance of the tested switching power supply when subjected to high amplitude interference voltage or current. The iec standard recommends the use of pulses with a rise time of 1.2 μs and a fall time of 50 μs. The detailed specifications are listed in Table 1.

The test pulse voltage should be injected from the appropriate location of the device under test, for example between terminals, between the terminals and the ground, or even between separate circuits on the same line. During the test, the test shall be carried out under all normal operating conditions.
After the test is completed, the equipment being tested should meet the standard requirements.
Of course, in the pulse shock test, a one-way discharge current pulse with a rise time of 8 μs and a fall time of 20 μs is often used. But such tests are usually for low-impedance devices.

2 test standards

Regarding the lightning surge immunity test standard, the most commonly used is the iec61000-4-5 standard, and various other emi standards are similar. In the examples given herein, the various test levels and corresponding test voltages used are shown in Table 2. The test pulse voltage is added between the two ends of the AC input and the ground, which is called "common mode", and the test pulse voltage is added between the two ends of the AC input, which is called "normal mode".

In the example of the lightning surge immunity test of the switching power supply cited in this paper, we have adopted these levels in the table after certification. That is, the "common mode" pulse voltage is up to 4kv, and the "normal mode" pulse voltage is up to 2kv.

3 test methods

(1) Test equipment and equipment under test In this example, the equipment is schgner's nsg651, which is one of the certified equipment. When using the "common mode" pulse voltage test, adjust the coupling resistance inside the device to 12, and the coupling capacitor to 9μf. When using the "normal mode" pulse voltage test, adjust the internal coupling resistance of the device to 2, The coupling capacitor is adjusted to 18μf. The device under test is an ac-dc switching power supply with an input voltage range of 85 to 265 VAC and an output voltage of 24 vdc. Because the power supply must be sold to Europe, the United States and other places, it needs to meet the iec safety specification standards, including lightning surge immunity test standards, so lightning surge immunity test must be carried out.
(2) Test conditions power input voltage: 100, 230vac;
Power output voltage: 24vdc;
Power output current: empty load, rated load;
Pulse voltage polarity: positive and negative;
Number of tests: 5 times each;
Test mode: "common mode", "normal mode";
Test phase: 0°, 90°;
Ambient temperature: 25 ° C.
(3) Test schematic diagram and test point "common mode" test point: between the power point n and the earth, between l point and the earth;
"Normal mode" test point: between power point n and point l.
The detailed test circuit schematic is shown in Figure 1.

Figure 1 Lightning surge anti-interference test details

Among them, "ac input" is the AC input, "surge generator" is the surge pulse voltage generator nsg651, "analog voltage meter" is the analog voltmeter, "aluminium plate" is the aluminum plate, and the wood made table is the wooden table. And dut is device under test (dut), is the device under test - the ac-dc switching power supply, load is the pure resistance rated load of the power supply.

4 test pass conditions

(1) During the test, the DC output voltage regulation rate does not exceed ±5% of the initial output voltage before the test;
(2) After the test, the DC output voltage regulation rate shall be within the range specified in the specification;
(3) While satisfying the last two conditions, there is no spark, smoke, and no output drop.

5 test results

The final test results are shown in Table 3. A test scheme with a "common mode" pulse voltage of up to 4kv and a "normal mode" pulse voltage of up to 2kv. Finally the power passed the test.

6 Conclusion

In this way, according to our passed the test pass conditions, we feel that the power supply passed the iec61000-4-5 regulations on lightning surge immunity.