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 Ripple voltage is the magnitude of fluctuation in DC output voltage at a specific output current.  This assumes the AC input voltage and frequency are kept constant.  A close approximation for series half-wave multipliers can be expressed as follows:

 [ I * (N2+N/2)] Vrip = 8*f*c N = number of stages f = AC input frequency (Hz) c = capacitance per stage (farads) I= DC output current (amps)

 Calculate Ripple Voltage Example Calculate the ripple voltage of a 6 stage multiplier with 1000pF capacitors, 50kHz operating frequency (sine wave), 1mA DC output current, 20kV DC output voltage as follows: Vrip = [ 1*10-3 (62+6/2)) ] where N = 6, f = 50kHz, c = 1000pf, I = 1mA. 8 (50,000) (1*10-9) Vrip = 97.5V

 An equivalent parallel multiplier would require each capacitor stage to equal the total series capacitance of the AC capacitor bank.  In the above case, the 3 capacitors in the DC bank would equal 1000pF/3 or 333pF. The parallel equivalent would require 333pF capacitors in each stage. However, each successive stage would require a higher voltage capacitor.
 Last revised: 03 Aug 2012