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Old 22nd July 2008, 06:53 PM   #1
ECBLN is offline ECBLN  Germany
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Default 60 V regulated for preamp supply

HI @ all,

i need a regulated power supply for my
60V preamp.

actually there is a zener / bd 179 regulation,
but its very unstable and noisy.

the dc input is about 85 Volts. Because of this high
input voltage i can´t use the normal LM317HV type´s

or is there a simple modification. ?

the preamp / channel switch / dc protection
consumes only between 50 mA to 250 mA on the 60 V line...


Best regards

EC
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Old 22nd July 2008, 07:24 PM   #2
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Well for a real quickie look at the TL 783ckc you can use it just
like the LM317t but it is rated up to 125v and has a 700ma
limit. Or the vegulator in one of the ZEN preamps had a voltage
and current real close to what you are asking for.
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Old 23rd July 2008, 06:22 AM   #3
ECBLN is offline ECBLN  Germany
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thx...

no no the tl might be interesting...

i whant to change the zener regulation to a linear intgr.reg.

will read today the datasheet & order the part from farnell.
its not expensive - that´s fine !

has anyone experience with that part ?
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Old 23rd July 2008, 07:24 AM   #4
lineup is offline lineup  Sweden
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hi.

This is an circuit of mine from november 2006.

U2 is a VBE multiplier with a voltage at BASE of 30 Volt.
R3 adds the 90 Volt to 120 Volt output.

U2 Base voltage is set by TL431 ( max 36 volt adjustable zener, temp stable ),
via divider R2/R1.

U3 is a Constant Current Source, 1 mA,
through TL431 and the 2N5551 (U2) .. for constant performance.

R5 should be chosen to provide enough current:
- A couple of mA for U3
- 1 mA for TL431
- Base current for U4 = MJE340 .. THE OUTPUT TRANSISTOR.
I have used 4 mA

C1 is for stability. May be adjusted in value.
You might have to add some compensation cap somewhere for increased stability, even if my simulation did not show anything but good and precise operation into various constant DC current loads.

It is a bit different when you have an AC Current load.

A Common STAR Ground is used for best zero reference.

R3 should be used for adjusting output voltage.
It is approximately 1 kohm per Volt.

I have used 2N5551, MJE350 & MJE340
because they are High Voltage transistors from Motorola.

Lineup
---------------------------

This 120 Volt regulator was created for my exploration of very high voltage Class A preamplifiers.
With use of very low global feedback factors.
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File Type: png hi-volt-reg_120v_lineup2006.png (10.2 KB, 628 views)
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Old 24th July 2008, 08:49 AM   #5
lineup is offline lineup  Sweden
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Default 60 Volt with my precision regulator.

Of course for 60 Volt output
you should set R3 to ~30 kOhm.

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Old 24th July 2008, 10:40 AM   #6
h_a is offline h_a  Europe
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Hi EC,

you should read datasheets more carefully

First paragraph LM117/317 datasheet

Quote:
Since the regulator is “floating”
and sees only the input-to-output differential voltage,
supplies of several hundred volts can be regulated as long as the maximum input to output differential is not exceeded, i.e. avoid short-circuiting the output.
You can even regulate the heater of tubes at several hundred volts if you want - as long as the differential input-output is below 37V.

And that applies already to the 'low voltage' LM317 - you don't even need the high voltage variant you refered to.

Have fun, Hannes
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Old 24th July 2008, 11:12 AM   #7
AndrewT is offline AndrewT  Scotland
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but, you must limit the voltage drop across the 317 at start up.
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Old 24th July 2008, 11:57 AM   #8
h_a is offline h_a  Europe
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Interestingly I find no mentioning of this in the datasheet, I could imagine that this is not a real world problem as power dissipation is in this case also very low and startup time is probably in the ms range.

Have fun, Hannes
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Old 24th July 2008, 12:09 PM   #9
AndrewT is offline AndrewT  Scotland
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I don't agree about the low power dissipation at start up.
I think the 317 will go into current limit trying charge up the output capacitor with near full input voltage across the 317.
If the chip is cold and is trying to pass 1.5Apk AND has 60V across it then I can't see how this stays inside the operating spec. of the reg.
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Old 24th July 2008, 02:01 PM   #10
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Look up threads on the MAIDA regulator -- very simple to implement, quiet.

In addition to the TL783 you can use the LR8N3 -- the latter device was designed for supervisory voltages in switch mode regulators but can also be used for high voltages. It's about $0.68 at Mouser. For more current you can use it with an external pass transistor like the MJE3439...
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