Bridge Rectifier Using Diode

Definition: The bridge rectifier circuit is a rectifier circuit, which converts an ac voltage to dc voltage.

These circuit generates output of full cycle for input of full cycle. No input cycle is wasted.

Bridge rectifier (circuit 1)

Input and output waveform of full wave rectifier

Bridge rectifier (circuit 2)

Input and output waveform of half wave rectifier

Working principal: For both circuit Vin is input voltage. Output is Vout. T is step down transformer. n1 is the turn ratio of primary coil and n2 is the turn ratio of secondary coil of transformer. Four diodes (D1, D2, D3, D4) are placed to form bridge (Wheatstone bridge) between for both Vn2 and Vout. Voltage drops at diodes are Vd. R is load resistor. For this bridge structure this rectifier is known as bridge rectifier.

Input voltage is applied in primary coil of transformer. This voltage is step down and transferred to secondary coil. Based on the polarity of input voltage and the position of diode, the diodes are forward biased (diode on) or reverse biased (diode off) and generate the output.

For first circuit, when Vin positive, Vn2 positive, D1, D3 are forward biased, D2 , D4 are reverse biased i.e. D1, D3 on, D2, D4 off. Vout = Vn2. Vout is positive as Vn2 positive. when Vin negative, Vn2 negative, D1, D3 are reverse biased, D2 , D4 are forward biased i.e. D1, D3 off and D2, D4 on. Vout = -Vn2. As Vn2 is negative, so Vout is positive.

For second circuit, when Vin positive, Vn2 positive, D1, D3 are forward biased, D2 , D4 are reverse biased i.e. D1, D3 on, D2, D4 off. Vout = -Vn2. Vout is negative as Vn2 positive. when Vin negative, Vn2 negative, D1, D3 are reverse biased, D2 , D4 are forward biased i.e. D1, D3 off and D2, D4 on. Vout = Vn2. As Vn2 is negative, so Vout is negative.

Peak Inverse Voltage (PIV): It’s the maximum voltage that the rectifying diode has to withstand when it is reverse biased. The peak inverse voltage (PIV) rating of a diode is of the primary importance in the design of rectification systems. When diode is reverse biased no current flows through load resistance and so causes no voltage drop across the load resistance and consequently the whole of the input voltage of secondary coil appears across the diode, is equal to the peak value of the secondary voltage.

When D2, D4 are off and D3, D1 are on then

from circuit, Vn2 - Vd2 = 0; Vout = Vn2. In reversed biased, Vd2 = Vpiv; Vout = Vn2 = Vpiv. Now Vm is peak value of Vn2(Vout).

So, Vpiv = Vm.

Application: The primary application of rectifiers is to derive DC power from an AC supply (AC to DC converter). Virtually all electronic devices require DC, so rectifiers are used inside the power supplies of virtually all electronic equipment.

Advantages of Bridge rectifier over half wave rectifier:

a) Ripple factor is low.

b) Rectification efficiency is high.

c) Transformer utilization factor is high.

Advantages of Bridge rectifier over full wave rectifier:

a) PIV is one half of that center tapped rectifier. So, it is suitable for high voltage application.

b) No center tap transformer is needed.

Disadvantages:

a)Little bit complex circuit and high cost compare to half wave rectifier circuit.

b) Four diodes are used. So Voltage drop at diodes are twice of that center tapped rectifier.

For more details on bridge rectifier, please visit:
1. Bridge Rectifier using diode - theoretical and derivation discussion of it's characteristics
2. Bridge Rectifier – Derivation and Simulation Using LTspice

For more details on rectifier circuit, please visit: Rectifier Circuit Design - YouTube.

For more details on various electronics circuit, please visit: It’s All About Electronics.

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