Single phase diode bridge rectifiers require either DC or AC inductance to adequately smooth the AC input current. The input waveform shape is dependent on the input voltage, dc output voltage and the amount of inductance on both the AC and DC sides of the rectifier. The input current starts increasing when the input AC voltage magnitude is greater than the DC output voltage, and then decreases when it is lower.

The two yellow shaded areas on the voltage plot indicate that the same values of positive and negative volt-seconds are applied to the inductor, which must be true for steady state to exist. On the current plot the two shaded areas show the regions in which the capacitor is being charged and then discharged. The yellow region that is above the load current value is for the case of the capacitor being charged. Under steady state conditions both the areas of the yellow regions are equal.

If a large capacitor is used to filter the output voltage and a small value of inductance is used then a very high but narrow current waveform is produced. If then the capacitor value is decreased this then results in oscillations of the input current. The value of load resistance (effectively damping) influences the number and magnitude of these oscillations.

• Shift the instantaneous time value using the red line (red timeline) on the time plots to see how the current flow changes in the rectifier circuit.
• Adjust the values of both the AC and DC inductors. Larger values increase the smoothing of the input current.
• Change the capacitor filter value. Note how small capacitor values result in more output voltage ripple.
• Adjust the load value and see the influence on the output DC voltage level and ripple.
• Change the input voltage level.