Simple PSU for a few valves

[Mark Hennessy]

HT power supplies seem to be something of a recurring theme and to me there is an answer so obvious that there must be a good reason for not doing it of which I'm unaware, namely using a thyristor.

Hi Joe,

I've seen thyristors used in lots of bench powers supplies. But these examples have been as pre-regulators; in other words they were followed by a conventional linear regulator. The control circuit was arranged such that the thyristor provided, if you'll forgive the over-precise maths(!), Vout plus a bit, thus reducing the DC drop across the linear regulator, hence reducing the heat generated, hence reducing the size of the heatsink needed, hence reducing the overall cost. Yes, always follow the dollar

I've never delved into these in huge detail, but would imagine that the raw DC at the smoothing capacitor might be a little rough - perhaps contaminated with switching spikes?

These days, switched-mode supplies have replaced thyristors, but many still have a linear post-regulator to clean up the output.

(Power supplies are a special interest area for me. I don't get out much :s)

Mark