Full Wave Rectifier

FULL-WAVE RECTIFIER

Full wave rectifier converts an ac voltage into pulsating dc voltage during both half cycles of the applied voltage.

Here, two diodes are used, one conducts during positive cycle and the other diode conducts during negative half cycle of the applied voltage.

A multiple winding transformer is used whose secondary winding is split equally into two halves with a common centre tapped connection (C).

This configuration results in each diode conducting in turn when its anode terminal is positive with respect to the transformer center point C. This produces output during both half cycles as shown in Fig.1.25.

The full wave rectifier circuit consists of two diodes connected to a single load resistance (R) with each diode supplying current to the load in turn. The output voltage across the resistor R is the phasor sum of the two waveforms.

Ripple Factor

The average voltage across the load resistance is

The rms value of voltage at load resistance

Efficiency

The maximum efficiency of a full wave rectifier is 81.2%

Transformer Utilization Factor (TUF)

The average TUF of full wave rectifier is 0.693.

Form Factor

Peak Factor

Peak Inverse Voltage (PIV)

The peak inverse voltage for full-wave rectifier is 2 Vm.

FULL WAVE BRIDGE RECTIFIER

The center tapping is eliminated in the bridge rectifier. In this rectifier, four diodes are connected to form a bridge. The ac input voltage is applied to the diagonally opposite ends of the bridge. The other two ends of the bridge are connected to the load resistance. Fig.1.26 shows the bridge rectifier using four diodes.

During positive half cycle of the input voltage, diodes D₁ and D₃ conduct and diodes D₂ and D₄ do not conduct. The current is produced due to diodes D₁ and D₃ and this current flows through the load resistance R_L.

During negative half cycle of the input ac voltage, diodes D₂ and D₄ conduct and diodes D₁, and D₃ do not conduct. The current flows in the load resistance due to diodes D₂ and D₄.

The current flows in the same direction in both positive and negative half cycles of the input voltage, thus an unidirectional output waveform is obtained.

The maximum efficiency of a bridge rectifier is 81.2% and the ripple factor is 0.48. The PIV is V_m. Fig. 1.27 shows the output waveform of bridge rectifier.

Table 1.3. Comparison of Rectifiers