Kerim
Member
I recall I was asked a few years ago to design a circuit which can protect ‘linearly’ a ready-made SMPS (an AC-DC Switching Mode Power Supply rated up to 240V input) from an AC overvoltage up to 400V. The SMPS had to keep working properly while being protected. To my big surprise, the added circuit in series with the SMPS input acted if it were a hi-voltage bipolar zener connected in parallel!
I attached the LTspice files (made in 2020) of the protecting circuit, as they are, ProtSMPS_01.zip.
On the LTspice schematic, the load is just a resistor instead of a SMPS model (which I don’t have). Therefore, the output, V(AC,NTR) on Rload, is not exactly the one seen on a scope when the protecting circuit is connected in series to a real SMPS. And on the SMPS, the voltage will look sinusoidal with a flat top (at the adjusted voltage limit) on both half cycles as if there were a high voltage bipolar zener connected to it in parallel.
I also attached its schematic made with Kicad, as PDF file.
Cheers,
Kerim
I attached the LTspice files (made in 2020) of the protecting circuit, as they are, ProtSMPS_01.zip.
On the LTspice schematic, the load is just a resistor instead of a SMPS model (which I don’t have). Therefore, the output, V(AC,NTR) on Rload, is not exactly the one seen on a scope when the protecting circuit is connected in series to a real SMPS. And on the SMPS, the voltage will look sinusoidal with a flat top (at the adjusted voltage limit) on both half cycles as if there were a high voltage bipolar zener connected to it in parallel.
I also attached its schematic made with Kicad, as PDF file.
Cheers,
Kerim