Regarding following figure, the input has a time average of 0, and root mean square (RMS) value equal to Vpeak/?2, where Vpeak is the maximum value of Vac. The output has a nonzero average value given by: Vdc= Vpeak /? and an RMS value equal to Vpeak/2 which related to lamp output. Therefore the (RMS) value of incandescent lamp current will be 1/?2 times and power consumptions (Ri2) in circuit with diode will be 1/2 times. Also because stability of circuit frequency we don’t face to any flickers generally. However, subharmonic frequency components may be generated that are undesirable as they may set up subharmonic resonance in the power supply system, cause lamp flicker. 