Contents
When to use a fly back diode in a circuit?
A flyback diode is commonly use to eliminate sudden voltage spike when current drop across an inductive load. These kind of diode can be found close to relay, motor or sometime MOSFET. Flyback diodes are mandatory to protect the circuit, especially parts that are weak to voltage drop. First question here :
Why are Schottky diodes used in flyback power converters?
Schottky diodes are preferred in flyback diode applications for switching power converters, because they have the lowest forward drop (~0.2 V rather than >0.7 V for low currents) and are able to quickly respond to reverse bias (when the inductor is being re-energized).
Is the Zener diode the same as the flyback diode?
A zener diode in series but with reverse polarity with regard to the flyback diode has the same properties, albeit with a fixed reverse voltage increase. Both the transistor voltages and the resistor or zener diode power ratings should be checked in this case.
What kind of diode do you need for a DC traction motor?
The type of diode you most probably need is a schottky diode. Those are the preferred diode type for flyback diodes. I work as a technician for the railways and for our DC traction motors we use flyback diodes that could barely handle the forward motor current but their forward surge current is very high and those diodes rarely break.
What happens when a diode is forward biased?
The resistance of the diode, when it is forward biased, is very less and hence the voltage drop across the diode will be significantly less for the current to flow. This prevents arc at the switching device and as a result protects the switching device from damage.
How is the resistance of a diode determined?
Hence, the diode will allow current to flow at a rate determined by the time constant of the inductor. The resistance of the diode, when it is forward biased, is very less and hence the voltage drop across the diode will be significantly less for the current to flow.
What happens to the diode when the switch is closed?
It is important to note that the diode is connected in reverse bias when the switch is closed. As a result, the diode doesn’t impact the operation of the rest of the circuit when the switch is closed and maximum current flows through the inductor.