[Amps] Step-start; improved circuit.

[Mark K5AM]

Some step-start circuit troubles have been reported recently.

The step-start circuit usually seen can sometimes cause trouble; the
problem is that the relay coil is part of the RC timing circuit. This
means that as the capacitor charges it first reaches a point where the
relay armature just begins to move slowly, and then finally the relay
closes. Not a snap-action arrangement. This slow closing can cause
contact burning and eventual failure.

To avoid such troubles, I use a step-start circuit with an op amp
timer. After a one second delay, full voltage is instantly applied
to the relay.

The circuit is described in a web article
"Overload Protection for High Voltage Power Supplies"
posted for download at www.zianet.com/k5am. The article
also includes ideas for other aspects of high voltage power
supply design.

73,

Mark, K5AM