kekon
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I have difficult problem with some device powered from offline SMPS flyback converter. The converter is based on Viper27H chip; 20W and has two outputs: 5V and 12V. It is powered from 230V AC with two wires (without earth wire).
The device contains 4 capacitive touch buttons (under 4mm glass plate). The power supply and device are placed on separate PCBs connected with 8-wire flat cable.
When i power my device from DC linear regulated power supply the touch panel works perfectly. But when it is connected to SMPS it becomes unresponsive. It is clear that there is some kind of EMI produced by SMPS that harms capacitive buttons. However, when the negative output terminal of SMPS is connected to earth, the problem disappears. Even when i connect the negative terminal to earth through 3.3nF capacitor it also helps. I added common mode choke to the converter, post filter but these solution simply don't work. It is really dufficult for me to solve the problem. I cannot use earh connection in my equipment as it is powered from two wire cable from 230V AC. Did anyone of you have similar problem ?
The device contains 4 capacitive touch buttons (under 4mm glass plate). The power supply and device are placed on separate PCBs connected with 8-wire flat cable.
When i power my device from DC linear regulated power supply the touch panel works perfectly. But when it is connected to SMPS it becomes unresponsive. It is clear that there is some kind of EMI produced by SMPS that harms capacitive buttons. However, when the negative output terminal of SMPS is connected to earth, the problem disappears. Even when i connect the negative terminal to earth through 3.3nF capacitor it also helps. I added common mode choke to the converter, post filter but these solution simply don't work. It is really dufficult for me to solve the problem. I cannot use earh connection in my equipment as it is powered from two wire cable from 230V AC. Did anyone of you have similar problem ?