Half-wave rectifier

The circuit diagram of  a half-wave rectifier is shown in fig. 2.5 below along with the I/P and O/P waveforms.

• The transformer is employed in order to step-down the supply voltage and also to prevent from shocks.
• The diode is used to rectify the a.c. signal while , the pulsating d.c. is taken across the load resistor RL.
• During the +ve half cycle, the end X of the secondary is +ve and end Y is  -ve . Thus , forward biasing the diode. As the diode is forward biased, the current flows through the load RL and a voltage is developed across it.
• During the –ve half-cycle the end Y is +ve and end X is –ve  thus, reverse biasing the diode. As the diode is reverse biased there is no flow of current through RL thereby the output voltage is zero.

2.5.2 Efficiency of a rectifier
The ratio of d.c. power to the applied imp ac power is known as rectifier efficiency.

2.5.3Derivation of rectifier efficiency of Half wave rectifier

Let V = V_msinθ be the voltage across the secondary winding

        r_f = diode resistance

        R_L = load resistance

d.c. power

a.c. power input

The a.c. power input is given by P_ac = I²_rms ( r_f + R_L)

Squaring both sides we get

The efficiency is maximum if r_f is negligible as compared to R_L

Therefore maximum rectifier efficiency  = 40.6 %

2.5.4 Full-wave rectifier

Full-wave rectifier are of two types

1.      Centre tapped full-wave rectifier

2.      Bridge rectifier