Regulated +80V Supply ....

[NRWler04]

Gentlemen,

For my Project I Need a 80v regulated Supply. I have a double rail +80V/0V PSU.

I'm only a mechanical engineer and Need a prinicipal Sketch how it Looks like ...

See also here: DIY Project - Nytech CPA602 today ...

Thanks for your help ...

[Mooly]

Looking at your other thread I'm assuming the 80 volts regulated is at very low current ?

If so a simple zener regulator is ideal (3 series connected 27 volts zeners) fed via a resistor. A small cap is placed across the three zeners to maintain a low impedance clean supply. The resistor value is calculated by knowing the voltage feeding the chain (which has to be higher than 80 volts) and the max current the regulator has to supply.

[NRWler04]

Originally Posted by Mooly

Looking at your other thread I'm assuming the 80 volts regulated is at very low current ?

If so a simple zener regulator is ideal (3 series connected 27 volts zeners) fed via a resistor. A small cap is placed across the three zeners to maintain a low impedance clean supply. The resistor value is calculated by knowing the voltage feeding the chain (which has to be higher than 80 volts) and the max current the regulator has to supply.

Yes I think so, it's at ver low current as it is to supply the VAS. Can I found somewhere a principal schematic?

Or does it makes sense to use a regulater like the LM317 ...?

[Mooly]

I'll draw it... give me a few minutes.

[KatieandDad]

Originally Posted by NRWler04

Yes I think so, it's at ver low current as it is to supply the VAS. Can I found somewhere a principal schematic?

Or does it makes sense to use a regulater like the LM317 ...?

You can use an LM317 with GREAT CARE. The max In-Out voltage is only 40V.

The zener chain as suggested above will do the job in this case.

[Mooly]

Like this. Resistor is calculated with ohms law to allow a few millamps to flow in the zeners.

eg, 100 volt unregulated. R=V/I so R=(100-81)/0.01 which is 1900 ohms. Use 1800 ohms as preferred value.

So that allows 10ma to flow in the zeners. The load (the amp) draws from that 10ma. If the load were 5ma then the zener current would reduce to 5ma with the above values. Always allow at least around 5 ma to flow in the zeners at all times.

[NRWler04]

Wonderful :-) I'll setup a schematic for the modified PSU today evening and will post the schematics.

There are also regulators available with higher voltage .... e.g. TL783 from Texas Instruments ....

[Mooly]

The zener type shunt regulator takes some beating with its low output impedance. I think they will give the cleanest possible supply.

The TL783 is an interesting choice but not without precautions. This type of regulator needs a minimum load applied at all times in the region of 15 ma (absolute minimum) so that could make it more inefficient than the zeners.

[NRWler04]

I'll do it with the zener shunt regulator .... And again I learned something :-)

[Mooly]

I was just looking at the circuit for the Nytech.

There's nothing to stop you using a "double" zener regulator. Use an 80 volt one as mentioned and add a 50 volt one for the bias network fed from the 80 volt one.