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NEWMAR 115 – 12 – 20AU Full-Wave Rectifier with Choke-Input Filter. Choke-Input Filter. DC Operation. +. +. V dc. V ’ dc. -. -. V’ dc = V dc (R inductor ) / (R inductor + R load ). AC Operation (approximate). Normally, make X capacitor << R load. Approximate the Circuit . +.
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NEWMAR 115 – 12 – 20AUFull-Wave Rectifier with Choke-Input Filter
DC Operation + + Vdc V’dc - - V’dc = Vdc(Rinductor) / (Rinductor + Rload)
AC Operation (approximate) Normally, make Xcapacitor << Rload
Approximate the Circuit + + Vr V’r - - Usually, Xinductor >> Xcapacitor V’[rms] = (Xcapacitor / Xinductor)(Vr[rms])
Full-Wave Rectifier OutputOutput frequency = twice the line frequency Second Harmonic (first ac component)
“Critical” Inductance, Lc Must keep the load current flowing for the complete cycle of the input voltage The dc load current must be > the peak value of the ac component of the load current
“Bleeder” Resistor • The bleeder resistor provides 2 functions • keeps a minimum current flowing through the inductor • discharges the filter capacitor after turn-off • Rbleeder = R1 = the largest value of Rload • sets the maximum value of inductor L
Range of values for the Filter Choke • NEWMAR 115 – 12 – 20AU Power Supply • Lmax > R1/1000 = 5/1000 = 5mH 50mH • Lc >= R1/1000 = (12 V/20 A)/1000 = 0.6mH