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current required 50ma. powered from ac line.The most convenient device to dial from 0 to house voltage is a variac (variable transformer). I purchased a 1.75A unit on Ebay.
Add a full diode bridge and hefty electrolytic capacitor. Wherever you set the voltage, it varies just slightly.
If you provide more details you can expect more informative replies. Example, current requirements, initial power source?
powered from ac line.
Capacitive drop is popular because it's transformer-less. The capacitor introduces reactive impedance, thus it doesn't generate heat the way ohmic impedance does.current required 50ma. powered from ac line.
my line voltage is 120v. need 0-100vdc, either linear or smps. isolated. 30-50ma. i need this supply to test for leakage in electro caps.Capacitive drop is popular because it's transformer-less. The capacitor introduces reactive impedance, thus it doesn't generate heat the way ohmic impedance does.
However it's not isolated thus it has a high voltage hazard.
R1 is for the purpose of limiting inrush current on power-up.
Here's a simple 100V supply. Unregulated. It needs further effort to make output voltage variable and regulated.
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