free wheel diodes
Sathish,
Yes, the diode shown in your schematic is a freewheel diode. An inductive device generates a voltage according to the equation V = Ldi/dt. When the current suddenly drops to zero, di/dt is very large, resulting in an "inductive kick" voltage, that may result in damage to other components. The free wheel diode provides a path for the inductive current to flow. The result is that the current through the inductor/diode combination at the instant of turn-off is equal to the current that was flowing just before turn-off. The current then decays exponentially according to i = imax(1-exp(-Lt/R) where:
. imax is the initial current
. t is time since turn-off
. L is the inductance
. R is the equivalent series resistance of the circuit.
Of course, for more complicated circuits, the equation might not be a simple exponential as shown above.
Regards,
Kral