# What happens if D2 and D4 is shorted in a full wave bridge rectifier?

Hello, What happens to the circuit if D2 and D4 diode is shorted?

If D2 is shorted you get a massive surge of current that will blow fuses and D3: -

Given that this is a catastrophic fail, I'll leave it to the OP to do the same thought experiment with D4 shorted.

• If the Vin have a Vpeak of 5v, i understand that in the positive cycle, the current will just flow pass 'D2', to 10kΩ, to 'D4' then back to Vin. but i dont know what will happen to the Vopeak in this positive cycle.
– kro
Commented Apr 25, 2020 at 12:53
• What you said appears to contradict itself - you talk about positive cycle and say the current will flow past D2 quite correctly, then you ask about the positive cycle again. Commented Apr 25, 2020 at 13:02

What could happen depends on the fuse, transformer and diode ratings.

1. A fuse of optimum rating could blow and protect the transformer and the okay diodes.

2. Should the fuse be overrated and the current rating of the diodes be much higher than that of the transformer, the transformer windings could overheat and burn out.

3. Should the fuse be overrated and the current rating of the transformer be much higher than that of the diodes, the diodes could open out or even explode.