LNNK302 with Vin fluctuating up and down from zero Volts
Hello,
Sorry about so many LNK302 questions.
I would like to do a 12V+/-10%, 12mA, non-isolated SMPS with LNK302 in buck configuration with Vin = 85-265VAC.
There will be no capacitance after the half wave mains rectifier……..so the V(in) will be zero for half the time….I will use a series diode to protect for those intervals when V(out)>V(in).
Obviously the LNK302 will be starting up and shutting down every 10ms…..
Will this damage the LNK302?, and does such on/off behaviour result in increased power draw from the mains due perhaps to any increased bias current flow into the LNK302 when it starts up?
Comments
thankyou, but would it not be OK if i include a schottky diode in series with the source of the LNK302's FET?
Consider adding a little bit of input capacitance so that the input will be greater than the output near AC zero crossing. Also, you may want to try increasing the BP pin capacitance so that the device can ride-through the interval near the zero crossing.
A Schottky diode in the S pin is a bad idea as all the external control circuit parts are referenced to this pin. You may want to consider a high voltage diode in series with the D instead.
Operation of the device with Vo > Vin is not recommended. Even if the part is not damaged, the output may have increased ripple.
Regards
PI-Sarek