• The resistance RB connected across the capacitor is called as bleeder resistance. It is used to maintain a continuous current through the filter inductance L.

• If the current through L is not continuous i.e. if it is interrupted then a large back emf (L di/dt) will be developed across the inductor.

• This voltage may exceed the PIV rating of the rectifier diodes and damage them. This voltage may exceed the maximum rated voltage of the capacitor as well.

• Hence the induced back emf is dangerous for diodes as well as the capacitor.

• The back emf will not appear if the current through L is continuous RB will maintain a continuous current through L.