Protection Diode Running Hot

Why is the protection diode running hot when connected across the load?

Posted by Paul (paul.larocque@mts.net) on 03/12/2004, at 11:40 GMT

Are you sure it is the correct way round?

The most likely explanation is that the diode is the wrong way round and therefore conducting when the load is switched on. A protection diode should be 'in reverse' so that it will not normally conduct. It should only conduct very briefly when an inductive load (such as a relay coil) is switched off and the inductance tries to keep the current flowing. Without the diode the inductance will produce a high voltage spike which can destroy a transistor or IC. For more details, including a circuit diagram, please see www.kpsec.freeuk.com/components/diode.htm#signal

Posted by John Hewes on 03/12/2004, at 13:52 GMT