Hi Maulik,
In a H-bridge configuration as an example in Bipolar mode, the diagonal switches are turn on and off alternately. Ideally when one pair are turned off, then the other pair can switched on immediately, however as the switches have a finite switch off time and may still be conducting, turning on can cause a dead short through one leg of the H-Bridge.
Dead-time is the period added after turn-off to allow for certain that the devices have turned off completely before the alternate diagonal pair is turned on. This time is device and load specific, but not having dead-time is a common cause of H-bridge failure, often the circuit may appear to work at low voltages and currents and be tolerant without dead-time, but testing closer to design limits will see the need to correctly switch the devices. Integrated gate drive IC's from major manufacturers often incorporate this protection.
Kind regards,
Les
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