## how to calculate / select flyback diode?

 I plan to use a flyback diode to absorb the current from a12V/38.8A/10mH DC motor when disconnecting the motor. The circuit can be similar circuit in below link: https://forum.arduino.cc/index.php?topic=52844.0 or figure 4 in below link: https://www.microtype.io/h-bridge-circuit-design/ How to calculate / select flyback diode? for example, how to decide IFSM(Non-Repetitive Peak Forward Surge Current 8.3ms, Single Half Sine-Wave Superimposed on Rated Load), IF(Maximum average forward rectified current), etc. You can recommend an article to help me. Thank you. by wangwg88 September 05, 2019 Add comment... Please sign in or create an account to comment.

 I was up against this problem many times when I worked for a living and the answer is really quite simple. Just understand that when the supply current is cut off the inductance of the motor (or other inductive device) becomes a current source generating the same current and current direction as existed immediately before the cutoff. When a flywheel (not flyback) diode is used this current flows through the diode and dies away on the L/R time constant of the inductive device. In the case of a dc motor this will probably be in the range of say 20 ms to 200 ms. You can shorten the time constant by adding a resistor in series with the flywheel diode but keep in mind that this will raise the voltage across the terminals of the inductive device. +1 vote by Foxx September 07, 2019 Add comment... Please sign in or create an account to comment.

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