Heating solution for H bridge transistor circuits

I want to talk about one of the major cause of heating in  H bridge and half bridge circuits which finally leads to failure. Though transistors in H bridge or half bridge may fail for many reasons, the most common cause of failure is "NO or SHORT DEAD TIME".

 DEAD TIME OF H BRIDGE CIRCUIT

From the theory behind H bridge mosfets or H bridge transistor circuits, power is delivered to the load when two diagonal transistors turns on. That is either (B and C ) or (A and D) from the image above.

The H bridge circuit is divided into two sides: Left side and right side. One of the principles guarding all H bridge circuits is that:
NO TRANSISTORS FROM THE SAME SIDE SHOULD TURN ON AT THE SAME TIME. Eg. A and C  or B and D.

When transistors from same side turns on, a phenomenon called shoot through will occur and that will produce a blasting sound, nice smell and  beautiful smoke.

In order to avoid shoot through, H bridge and half bridge circuit should be driven in such a way that, transistors from same side does not turn on and also transistors are only turn on diagonally.

In other to ensure that transistors are turned on only diagonally,  a small delay time known as dead time is introduced in the switching circuit. The delay circuit is ensures that one diagonal switch side is completely turned off before the next diagonal turns on.

Heating solution for H bridge transistor circuits

 Heating in H bridge transistor as a result no or short dead time can be solved by