Bridge Rectifier Circuit Efficiency

The bridge rectifier circuit is a widely used circuit that converts AC voltage into DC voltage. The efficiency of a rectifier circuit is the ratio of DC output power to the AC input power. The theoretical maximum efficiency of a bridge rectifier circuit can be calculated by assuming ideal diodes and no voltage drops in the circuit.

Calculation of Maximum Efficiency

The bridge rectifier circuit consists of four diodes that are arranged in a bridge configuration. The AC voltage is applied to the input of the circuit and the output voltage is taken across the load resistor. The maximum efficiency of the circuit can be calculated as follows:

Efficiency, η = (DC output power / AC input power) x 100%

DC output power = (Vdc2 / (2R))
where Vdc = maximum DC voltage across the load resistor and R = load resistor

AC input power = (Vrms2 / R)
where Vrms = RMS voltage of the AC input voltage

Substituting the above equations in the efficiency equation, we get:

η = (Vdc2 / (2R)) / (Vrms2 / R) x 100%
η = (Vdc2 / (2Vrms2)) x 100%

In an ideal bridge rectifier circuit, the maximum DC voltage across the load resistor is equal to the peak voltage of the AC input, which is Vp = √2 x Vrms. Substituting this value in the above equation, we get:

η = (Vp / (2Vrms))2 x 100%
η = (0.5)2 x 100%
η = 25%

However, in a practical circuit, there are voltage drops across the diodes, which reduces the maximum DC voltage across the load resistor. This reduces the efficiency of the circuit. The practical maximum efficiency of a bridge rectifier circuit is around 81.06%.

Therefore, the correct option is (c) 81.06%.