[ARC5] Power Supplies for Your ARC-5

[J. Forster]

> I'm wondering if power supply design and manufacturer varies enough so that
> one PS at 9amps might work fine, whereas another "crowbars" to zero volts?
> The lambda designs that I'm familiar with just don't do this.

A 'crowbar' is an over voltage protector. On the Lambda's it is designated by
'OVP' or somesuch in the model number, or by a small module screwed to the unit
near the output terminals. The module has a zener, SCR and a resistor or two. It
shorts the output to prevent external equipment (like ICs) damage from
overvoltages.

There are two basic types of current limiting: constant current and fold-back
current limiting.

The constant current just means the supply operates constant voltage until the
current limit is reached, and then goes constant current.

The fold-back supplies dorp to a low current if overloaded. They usually have to
be switched off the reset. The foldback is to limit the dissipation in the pass
transistors.

-John