Diode Rectifiers


Diode Ratings

Current Handling Capacity.
Peak Inverse Voltage (PIV ): It is the largest reverse voltage that is expected to appear across the diode. Usually, diodes are selected which have VZ at least 50 % greater than PIV.

Filter Circuits

The output of a rectifier is not purely dc. It also has some ac components, called ripples.
The ripples are maximum in half-wave rectifier, and are less in full-wave rectifier
Filter circuit converts pulsating output of a rectifier into a steady dc level.
Filters simply smoothen out the ripples.
There are two ways to do it :
Ripples are bypassed around a the load by using a shunt capacitor.
Ripples can be limited to a low value by a series inductor.
A filter circuit is generally a combination of capacitors and inductors.
Filtering action depends upon the fact that:
Capacitor allows ac only to pass.
Inductor allow dc only to pass.

Shunt Capacitor Filter

Operation of Capacitor Filter

During the conduction period, the capacitor gets charged and stores energy.
During the non-conduction period, the capacitor discharges through the load resistance delivering energy to it.
Capacitor gets charged to the peak value quickly because charging time constant is almost zero.
Discharging time constant is quite large, because it discharges through the load resistance.
As XC << RL, the ripples are bypassed through the capacitor and only dc component flows through the load resistance.