To turn a power MOSFET on, the gate terminal must be set to a voltage at least 5 volts greater than the source terminal. One feature of power MOSFET is that they have a large stray capacitance between the gate and the other terminals. The effect of this is that when the pulse to the gate terminal arrives, it must first charge this capacitance up before the gate voltage can reach the 10 volts required. The gate terminal then effectively does take current. Therefore the circuit that drives the gate terminal should be capable of supplying a reasonable current so the stray capacitance can be charged up as quickly as possible. The best way to do this is to use a dedicated MOSFET driver chip. Since the operating voltage of the H-bridge is 230V when the high side MOSFETs are conducting the voltage at the source would be almost 230V. Two separate power supplies power driver circuit1 and driver circuit2, while driver circuit3 and driver circuit4 are powered by a common power supply. The Micro controller pulse is amplified by a buffer IC and the output from the buffer is fed to an opto isolator. The function of the opto isolator is to switch the external power supply given to the driver circuit appropriately in order to provide the required Gate to Source voltage of the MOSFET.