1. ECE 442 Power Electronics1 NEWMAR 115 – 12 – 20AU Full-Wave Rectifier with Choke-Input Filter

2. ECE 442 Power Electronics2 Choke-Input Filter

3. ECE 442 Power Electronics3 DC Operation V dc + - V ’ dc + - V’ dc = V dc (R inductor ) / (R inductor + R load )

4. ECE 442 Power Electronics4 AC Operation (approximate) Normally, make X capacitor << R load

5. ECE 442 Power Electronics5 Approximate the Circuit VrVr V’ r - + - + V’ [rms] = (X capacitor / X inductor )(V r[rms] ) Usually, X inductor >> X capacitor

6. ECE 442 Power Electronics6 Full-Wave Rectifier Output Output frequency = twice the line frequency Second Harmonic (first ac component)

7. ECE 442 Power Electronics7 2π(120)

8. ECE 442 Power Electronics8 “Critical” Inductance, L c 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

9. ECE 442 Power Electronics9 Minimum Inductance L c

10. ECE 442 Power Electronics10 “Bleeder” Resistor The bleeder resistor provides 2 functions –keeps a minimum current flowing through the inductor –discharges the filter capacitor after turn-off R bleeder = R 1 = the largest value of R load –sets the maximum value of inductor L

11. ECE 442 Power Electronics11 Range of values for the Filter Choke NEWMAR 115 – 12 – 20AU Power Supply L max > R 1 /1000 = 5/1000 = 5mH  50mH L c >= R 1 /1000 = (12 V/20 A)/1000 = 0.6mH