regulated power supply for high powered amps.

[wg_ski]

Originally posted by analog_sa


Curious though: can it really output hundreds of volts if the differential limit is met?

Yes, but with caution. As long as Vin-Vout is within safe limits any regulator can regulate any voltage. The trouble is keeping it that way under all conditions - including start-up and current limit conditions, where you could try to force a larger volatge difference across it. The app notes usually show what extra circuitry needs to be added to keep this from happening.

[richie00boy]

Yes and so can the LM317. However, in practical reality you must limit the input voltage to the max specified because as soon as you put a cap on the output of the regulator, at startup it holds the output at close to zero volts for a short time which will cause differential limits to be exceeded if your input is too high.

It may survive for a while but soon it may well go pop.

[analog_sa]

Excellent point. I was also wondering about the output cap.

[h_a]

Well, simplest would be to use an appropriate Zener across the regulator to clamp the differential voltage (power-Zener!).

In that case I would definitely recommend to limit current inrush, maybe simplest by using thermistors or relay bypassed resistors. But that also depends on capacitance you put after the regulator. Maybe a suitable thermistor in series to the Zener is sufficient.

However to build such a thing reliably would need a little experience and some trial and error.

Have fun, Hannes

[JPV]

Originally posted by h_a
Well, simplest would be to use an appropriate Zener across the regulator to clamp the differential voltage (power-Zener!).

In that case I would definitely recommend to limit current inrush, maybe simplest by using thermistors or relay bypassed resistors. But that also depends on capacitance you put after the regulator. Maybe a suitable thermistor in series to the Zener is sufficient.

However to build such a thing reliably would need a little experience and some trial and error.

Have fun, Hannes

There is a device TSR made by a german engineer (http://www.emeko.de/index.php?id=29&L=1) that controls the inrush current in toroidal transformers by controlling the operating point of the transformer in sending current pulses at switch on. One model of this device can also take into account the control of inrush current added by a capacitor bank after the rectifier.
The capacitors of the regulators are in parallel with the bank. In this way, using a TSR and a regulator with zener clamp would perhaps be a reliable and easy approach to the problem.

JPV