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Transistor regulators?

C

Cruiser

Jan 1, 1970
0
I would like to
know if transistors can be used as a voltage regulator, as with the
LM317T is for lower voltages. The reason for my question is that I
would like to build a higher voltage variable regulator .....up to 400
volts. The older Heathkit types IP-17, and IP-32 used tubes to vary
the output ( 6L6's ) Up to 150ma @ 400 volts.

Has this been done using transistors? If so by whom?, Company name?,
Model?, Schematic?.

Thanks for any information in advance.
 
J

John Popelish

Jan 1, 1970
0
Cruiser said:
I would like to
know if transistors can be used as a voltage regulator, as with the
LM317T is for lower voltages. The reason for my question is that I
would like to build a higher voltage variable regulator .....up to 400
volts. The older Heathkit types IP-17, and IP-32 used tubes to vary
the output ( 6L6's ) Up to 150ma @ 400 volts.

Has this been done using transistors? If so by whom?, Company name?,
Model?, Schematic?.

Thanks for any information in advance.

Field effect transistors are probably your best bet for this service.
They are commonly available with voltage ratings up to about 1000, and
power dissipation ratings high enough to survive a short circuit while
current limiting, if they are mounted on a large enough heat sink.
The circuit for them is very similar to that used for tubes, except
that they require a positive gate bias before they turn on whereas
tubes are on till you apply a negative bias to turn them off.

You might look at some of the available devices at:
http://ec.irf.com/v6/en/US/adirect/ir?cmd=catNavigateFrame
select Hexfet power MOSFET.
 
W

Winfield Hill

Jan 1, 1970
0
John Popelish wrote...
Field effect transistors are probably your best bet for this service.
They are commonly available with voltage ratings up to about 1000V and
power dissipation ratings high enough to survive a short circuit while
current limiting, if they are mounted on a large enough heat sink.

From a post of mine made a few years ago: ... a simple
high-voltage regulator that uses standard LM317 or LM317L
chips plus an easy-to-get reliable high-voltage MOSFET.

600V FET _____ LM317L 5 to 500V
IN o----+----, ,-+-----+--| |--+---+----+---o OUT
| | | | s | | | | | | 2 to 100mA
| _|_V_|_ | |_adj_| 1.2k | |
2.2M ----, | | | | | 0.47uF
1/2 W | '-||--+-----+ | ===
| | , 68pF | | | 630V
'--------+---|<|-----------|---' |
' 10V zener | 2.7 ohms
500k |
pot gnd
|
gnd

The FET needs a very serious heat sink, because 450V at
100mA is 45 watts, and under a short circuit condition the
LM317L may allow even more current to flow. You can add
a single-transistor foldback current limit if you want.

Add a 1n4002 diode backwards across the LM317 if you plan
on ever shorting out the input filter-storage capacitor.
(Always use drain resistors with high-voltage capacitors.
And always approach the open circuit with one hand behind
your back.)

The LM317L needs as much as 2.5mA to operate, and the 1.2k
resistor only takes 1mA, so this sets a 1.5mA minimum load
requirement. (Note, you could use 470-ohms instead of 1.2k,
but this would require a 200k pot with 1W of dissipation,
instead of the 0.4W maximum dissipated in the 500k pot when
it's set to about 400k for +400V out.)

---

Note: I haven't tried this circuit, since I prefer to use
HIP5600 and VB408, etc., high-voltage regulator ICs.

Thanks,
- Win

whill_at_picovolt-dot-com
 
J

John Popelish

Jan 1, 1970
0
Winfield said:
John Popelish wrote...

From a post of mine made a few years ago: ... a simple
high-voltage regulator that uses standard LM317 or LM317L
chips plus an easy-to-get reliable high-voltage MOSFET.

600V FET _____ LM317L 5 to 500V
IN o----+----, ,-+-----+--| |--+---+----+---o OUT
| | | | s | | | | | | 2 to 100mA
| _|_V_|_ | |_adj_| 1.2k | |
2.2M ----, | | | | | 0.47uF
1/2 W | '-||--+-----+ | ===
| | , 68pF | | | 630V
'--------+---|<|-----------|---' |
' 10V zener | 2.7 ohms
500k |
pot gnd
|
gnd

The FET needs a very serious heat sink, because 450V at
100mA is 45 watts, and under a short circuit condition the
LM317L may allow even more current to flow. You can add
a single-transistor foldback current limit if you want.

Add a 1n4002 diode backwards across the LM317 if you plan
on ever shorting out the input filter-storage capacitor.
(Always use drain resistors with high-voltage capacitors.
And always approach the open circuit with one hand behind
your back.)

The LM317L needs as much as 2.5mA to operate, and the 1.2k
resistor only takes 1mA, so this sets a 1.5mA minimum load
requirement. (Note, you could use 470-ohms instead of 1.2k,
but this would require a 200k pot with 1W of dissipation,
instead of the 0.4W maximum dissipated in the 500k pot when
it's set to about 400k for +400V out.)

Very nice circuit, but you may have to go higher than 1/2 watt for the
gate pull up resistor to find one rated for the full input supply
voltage.
 
W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
I would like to
know if transistors can be used as a voltage regulator, as with the
LM317T is for lower voltages. The reason for my question is that I
would like to build a higher voltage variable regulator .....up to 400
volts. The older Heathkit types IP-17, and IP-32 used tubes to vary
the output ( 6L6's ) Up to 150ma @ 400 volts.

Has this been done using transistors? If so by whom?, Company name?,
Model?, Schematic?.

Lambda made such PSes long ago. So did Dressen-Barnes, LH Research
and many other companies. I'd guess that most of them ended up on the
scrap heap. The tube PSes were monster heat generators, so they went
first. Probably the main reason why they became so unpopular was that
linear supplies, no matter what the voltage, waste a lot of power as
heat. Today a power supply with the same output will waste much less
power and stay cooler, and cost less, with better performance. That's
because it is a switching power supply, not a linear power supply.

Go to URL and do a control-F to search for 723, then check the data
sheet for this IC. You can use it or use several transistors or use
an opamp for any voltage power supply.
http://www.ee.latrobe.edu.au/internal/workshop/datasheet.html

And for god's sake don't get the toob nuts started, you'll never hear
the end of it! :O)
Thanks for any information in advance.


--
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W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
Field effect transistors are probably your best bet for this service.
They are commonly available with voltage ratings up to about 1000, and
power dissipation ratings high enough to survive a short circuit while
current limiting, if they are mounted on a large enough heat sink.
The circuit for them is very similar to that used for tubes, except
that they require a positive gate bias before they turn on whereas
tubes are on till you apply a negative bias to turn them off.

You might look at some of the available devices at:
http://ec.irf.com/v6/en/US/adirect/ir?cmd=catNavigateFrame
select Hexfet power MOSFET.

BJT transistors and IGBTs are just as capable as power FETs for this,
but BJTs are hampered by SOA limitations, so they have to be protected
against excessive power dissipation. The FETs parallel easily, so can
handle lotsa power. No matter what kind, your power supply should
have well designed protection againstg overvoltage and overcurrent.
If not, then it's not going to last very long. ;-)


--
@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@,@@[email protected]@[email protected],@@[email protected]@[email protected]@[email protected]@
###Got a Question about ELECTRONICS? Check HERE First:###
http://users.pandora.be/educypedia/electronics/databank.htm
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you add NOSPAM in the
Subject: line with other stuff. alondra101 <at> hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html
@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@[email protected]@[email protected]@@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@[email protected]@@
 
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