Transformerless power supply

[tcmtech]

Yes however as I mentioned earlier for a 2 amp power supply using direct line coupling I would not use a filter cap anywhere less than 4000 uf.
Personally given it's being fed by a half wave capacitive source I would be using closer to 10,000 uf myself.

 

[ronv]

That makes is worse. You think the 33 Ufd. cap has a 100 ohms or so at 50 Hz. so no biggie. But when the switch is thrown at the top of the sine wave from mains to the supply the rise time is very fast and the 33Ufd. impedance is virtually zero. Now the only thing limiting the current is the diodes, the ESR of the 33 Ufd., the filter caps and the line wiring. Same with the voltage. The only thing holding it down is the capacitance and ESR of the filter caps.

 

[MrAl]

Hi,

Just a real quick addition in case this hasnt been mentioned yet...

The current through a resistor in series with a capacitor excited by voltage source of amplitude E is exactly equal to:
I=E/sqrt(R^2+1/(w^2*C^2))

and you might recognize this as also:
I=E/sqrt(R^2+xC^2)

where xC is the reactance of the capacitor.

I in amps, E in volts, R in Ohms, C in Farads.

 

[tcmtech]

That makes is worse. You think the 33 Ufd. cap has a 100 ohms or so at 50 Hz. so no biggie. But when the switch is thrown at the top of the sine wave from mains to the supply the rise time is very fast and the 33Ufd. impedance is virtually zero. Now the only thing limiting the current is the diodes, the ESR of the 33 Ufd., the filter caps and the line wiring. Same with the voltage. The only thing holding it down is the capacitance and ESR of the filter caps.

I don't really have any issues with that. I work with large switching power supplies used in welders plasma cutters VFD units and other high powered solid state power supplies and I see many of them have primary capacitor banks that are in the hundreds to thousands of uf ranges getting charged up to 380 VDC without any current limiting between the AC side and the DC side.

The thought of connecting a 33 uf cap across a 220 VAC line really doesn't worry or concern me to any degree. At worse the OP can put a few ohm multi watt resistor in series with his AC side of the circuit.