1. In positive half cycle (0 to Π): The end A of the secondary winding becomes positive and end B negative. This makes diode D1 and D4 forward biased while diode D2 and D3 are reverse biased. These two diodes will be in series through the load RL. The conventional current direction is as follows. A – D1 – RL – D4 – B This makes load voltage polarities as shown in the fig above.
2. In negative half cycle (Π to 2Π). The end B is positive and A is negative. This makes diode D2 and D3 forward biased and diode D1 and D4 is reverse biased. The conventional current through diode D2 and D3 when it is conducting is as follows.
B – D2 – RL – D3 – A