Question

What is rectification ? Explain the working of a bridge rectifier.

Answer 1

Rectification is the process that converts a bidirectional current flow into a unidirectional current flow, OR

Rectification is the conversion of alternating current to direct current. Rectification is performed. by a diode that allows current to flow in one direction but not in the opposite direction.

From the above figure,

consider the case wherein the positive pulse appears at the AC input i.e. the terminal A is positive while the terminal B is negative. This causes the diodes D1 and D3 to get forward biased and at the same time, the diodes D2 and D4 will be reverse biased.

As a result, the current flows along the short-circuited path created by the diodes D1 and D3 (considering the diodes to be ideal), as shown by Figure 2a. Thus the voltage developed across the load resistor RL will be positive towards the end connected to terminal D and negative at the end connected to the terminal C.

Next, if the negative pulse appears at the AC input, then the terminals A and B are negative and positive respectively. This forward biases the diodes D2 and D4, while reverse biasing D1 and D3 which causes the current to flow in the direction shown by Figure 2b. At this instant, one has to note that the polarity of the voltage developed across RL is identical to that produced when the incoming AC pulse was positive in nature. This means that for both positive and negative pulse, the output of the bridge rectifier will be identical in polarity.