Why is the 400VAC chosen for C1 in View attachment 68889?
Is it chosen to provide a conservative margin for voltage spikes above 230VAC in the absence of any other spike protection or is it something more specific?
Would an 275VAC X2 capacitor be sufficient in general usage up to 240VAC?
Theoretically the capacitor can charge to 1.4 times nominal ACV (with a light load).
So for 240 incoming AC, the capacitor charge can reach +335 or -335 V.
I understand that Vpeak = 1.4 x Vrms. By the same token, I thought a 400VAC capacitor is rated at 400VRMS, that is, 560Vpeak.
I would have thought that a 275VAC capacitor (which is 388Vpeak) would be sufficient for a 230VAC supply (which is 324Vpeak). In fact I thought that 275VAC X2 capacitors are specifically designed to be connected across up to 240VAC line to neutral.
Please help if I am misunderstanding something!
... at least reduce the voltage using half wave rectification..
For the topology shown in Microchip's App note is very simple and cost effective for low power transformerless power supply. One can ask - why I need such power supply? I can use SMPS or small iron core transformer instead.
But my point is if I need a power supply for a small MCU circuit required only about 50-100mA at 5v DC does SMPS or small iron core transformer really required or efficient?
What do you suggest for such small amount of power requirement (50-100mA current from 5v dc)?
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