Another type of circuit that produces the same type of output waveform as the full wave rectifier circuit is that of the Full Wave Bridge Rectifier.
The Bridge Rectifier | Overview
This type of single phase rectifier uses four individual rectifying diodes that are connected in a closed loop bridge configuration to produce the desired output. A diode bridge is provides the same polarity of output for either polarity of input.
It does not require a special centre tapped transformer, this fact reducing size and cost of the bridge rectifier. The single secondary winding is connected to one side of the bridge diode network and on the other side the load is connected as shown below.
The Diode Bridge Rectifier
The four diodes that are label D1 to D4 are in series pairs. Through this arrangement only two diodes conducting current during each half cycle.
The Positive Half-cycle
During the positive half cycle of the supply, diodes D1 and D2 conduct in series will operate and diodes D3 and D4 are reverse biased and the current flows through the load as shown below:
The Negative Half-cycle
During the negative half cycle of the diodes D3 and D4 conduct in series, but diodes D1 and D2 switch OFF as they are now working on reverse biased. The direction of current flowing through the load is the same as before.
As the current flowing through the load in bridge rectifier is unidirectional, so the voltage that developed across the load is also unidirectional. Therefore the average direct current voltage across the load is 0.637Vmax.
Typical Bridge Rectifier
During each half cycle the current flows through two diodes instead of just one so the amplitude of the output voltage is two voltage drops this means that the voltage of 1.4V is dropped or less than the input VMAX amplitude.
The ripple frequency is now twice of the supply frequency. For example the frequency is 100Hz for a 50Hz supply or 120Hz for a 60Hz supply.
We can use four power diodes to make a full wave bridge rectifier. The components in it are available in a range of different voltage and current sizes that can be soldered directly into a PCB or be connected by spade connectors.
- In it the Step down Transformer is not required.
- Bridge rectifier has higher efficiency then half wave and full wave rectifier.
- Its output waveform is continuous.
- To use a bridge rectifier, a low level filter is required, so thus reducing the cost of it.
- In it the four diodes are used that increases the cost of making it.
- The value of the diodes used should be precise; otherwise there will be an error in rectification.
- The output is not a proper direct current quantity. It has ripples in its output waveform.