Full-Wave Bridge Rectifier
What is a full-wave bridge rectifier?
Power diodes can be connected together to form a full-wave rectifier that converts AC voltage into pulsating DC voltage for use in power supplies. While this method may be suitable for low power applications, it is not suitable for applications which need a “steady and smooth” dc supply voltage. One method to improve this is to use every half-cycle of the input voltage instead of every other half-cycle. The circuit which allows us to do this is called a Full Wave Rectifier.
Like the half-wave circuit, a full-wave rectifier circuit produces an output voltage or current which is purely DC or has some specified DC component. Full-wave rectifiers have some fundamental advantages over their half-wave rectifier counterparts. The average (DC) output voltage is higher for half-wave, the output of the full-wave rectifier has much less ripple than that of the half-wave rectifier producing a smoother output waveform.
The Diode Bridge rectifier
Network of Figure1 Full-wave Bridge rectifier Network of Figure 2 for the period 0-T/2 of the input voltage Vi
The four diodes labelled D1 to D4 are arranged in “series pairs” with only two diodes conducting current during each half cycle. During the positive half cycle of the supply, diodes D1 and D2 conduct in series while diodes D3 and D4 are reverse biased and the current flows through the load as shown below:
The dc level obtained from a sinusoidal input can be improved 100% using a process called full-wave rectification The most familiar network for performing such function appears in fig A with its four diodes in a bridge configuration. During the period t=0 to T/2 the polarity of the diode is as shown in fig 2.The resulting polarities across the ideal diodes are also shown in fig A to reveal that D2 and D3 are conducting, whereas D1 and D4 are in the “off” state. The net result is the configuration of fig A with its indicated current and polarity across R. Since the diodes are ideal, the load voltage is v₀ = vi as shown in figure:
Network of Figure 3 Conduction path for the positive region Vi
Positive Half cycle
Network of Figure 4 Conduction path for the negative region of Vi
Negative Half cycle
Input and output waveform for Bridge rectifier
Application of full wave Bridge rectifier
Full Wave Bridge Rectifier is used to detect the amplitude of the modulating radio signal. Bridge rectifier circuits are also used to supply steady and polarized dc voltage in electrical welding.
What are the advantages of bridge rectifiers over full wave rectifiers?
Higher output voltage, higher output power and higher transformer utilization factor in case of full-wave rectifier. No center tap is required in the transformer secondary, so in case of a bridge rectifier the transformer required is simpler.