Question

Draw the circuit diagram and describe the working principle of full wave bridge rectifier. Draw its waveforms. 

Answer 1

During the first half cycle : During the first half cycle of the input voltage, the upper end of the transformer secondary winding is positive with respect to the lower end. Thus during the first half cycle diodes D1 and D3 are forward biased and current flows through arm AB, enters the load resistance RL, and returns back flowing through arm DC. During this half of each input cycle, the diodes D2 and D4 are reverse biased and current is not allowed to flow in arms AD and BC. The flow of current is indicated by solid arrows in the figure above. We have developed another diagram below to help you understand the current flow quickly. See the diagram below – the green arrows indicate the beginning of current flow from the source (transformer secondary) to the load resistance. The red arrows indicate the return path of current from load resistance to the source, thus completing the circuit. 

During the second half cycle : During the second half cycle of the input voltage, the lower end of the transformer secondary winding is positive with respect to the upper end. Thus diodes D2 andD4 become forward biased and current flows through arm CB, enters the load resistance RL, and returns back to the source flowing through arm DA. The flow of current has been shown by dotted arrows in the figure. Thus the direction of flow of current through the load resistance RL remains the same during both half cycles of the input supply voltage. See the diagram below – the green arrows indicate the beginning of current flow from the source (transformer secondary) to the load resistance. The red arrows indicate the return path of current from load resistance to the source, thus completing the circuit.

OR

Description in simple : At positive half cycle the Diode D1 and D3 will be forward biased and current path will be Terminal A, Diode D1,Terminal B, Resistor RL, terminal D, diode D3, and terminal C back to transformer and output will positive half cycle. At the negative half cycle diode D2 and D4 will be forward biased current path will be Terminal C, Diode D2,Terminal B, Resistor RL, terminal D, diode D4, and terminal A back to transformer and output will positive half cycle.