How to survive a 4kV surge voltage
Hello everybody,
I submitted the power supply (TinySwitch III desing) to a surge test according to IEC 61000-4-5 and it failled when I applied a 4kV surge in differential mode. For 1kV and 2kV surge voltage, the power supply pass in the test.
The strike was applied with wait time of 1 minute and the power supply blows after 2 or 3 positive strikes.
The input circuit is similar to EP91 desing and the diodes 1N4007 were damaged (low resistence). The MOV is ok and I put next to the AC input.
Could you help me in order to increase the voltage surge up to 4kV?
Comments
Many thanks for your replay.
The test was realized at a lab test and there are several restrictions (the lab test is far from my office, the test is very expensive and etc) to do the test again and measure the waveform. Do you have another suggestion?
If I increase the MOV size (14 mm instead 7 mm), will help to pass surge test of 4 kV?
In some desing is recommended to add a fusible resistor in serie of ac input for protection. Can this help to pass the surge test?
The PCB layout could be improved in order to meet the surge immunity requirements?
Yes it may help to increase the MOV size but with each successive strike the MOV may be weakened and then fail before 10 strikes as specified to pass.
Placing a fusible resistor in series may help inrush current and damp any potential oscillations but it is not a guaranteed fix. It is very difficult to tell how to correct a surge failure without diagnostic information.
-Wesley
Could you please provide a current and voltage waveform of the strike. The voltage should be measured after the rectifier. This would help very much in identifying why the diodes are failing.
-Wesley