Start at a low safe voltage with maybe a lighter load and check for the magnitude of the voltage spike each time the device switch off.
(Please note that Test Switch Port goes to ground, SMPS port is not used)Īny assistance you could give on what could be causing this problem or what things I should be checking would be greatly appreciated.ġ) Run the unit off a variac with a isolation transformer while monitoring the voltage between Drain and Source of the chip with a good scope. When the circuit is functioning regulation is very good with around 1% Voltage ripple on the DC output.Īttached is our circuit diagram for the power supply. The circuit load on the secondary is quite small (around 7W) and the circuit does not seem to be running excessively hot. I was thinking that perhaps this problem is caused by the RC snubber circuit in the design (there is no diode used in the snubber circuit). When it fails it is quite spectacular with a flash, then the circuit fuse blows. The current design is very close to AN1735.įrom what I can see the SMPS IC is failing at the Source Pins (burn marks can be seen on these pins after a failure). I have been having some problems with the circuit blowing up after a few minutes of operation. I have been developing an emergency light which uses a Viper22A SMPS for its power supply.
