Re: TIP50 for HT regulator
- From: Patrick Turner <info@xxxxxxxxxxxxxxxxxx>
- Date: Thu, 24 Jul 2008 13:27:45 GMT
Ian Thompson-Bell wrote:
flipper wrote:
On Wed, 23 Jul 2008 10:00:28 -0500, John Byrns <byrnsj@xxxxxxxxxxxxx>
wrote:
In article <4prc84lsgbk0dvoorirkcnrk888gemis2v@xxxxxxx>,
flipper <flipper@xxxxxxxx> wrote:
On Tue, 22 Jul 2008 23:34:17 +0100, Ian Thompson-BellI'm looking for a capacitance multiplier design to replace the inductors
<ruffrecords@xxxxxxxxxxx> wrote:
At a local ham fest I picked up 100 of 150V zeners so I thought I wouldWatch out for SOA and turn on surge into downstream caps. They're good
build myself a stabilised 300V HT supply - not big current, just enough
for my mic pre projects. So, I have been looking at high voltage
transistors and came across the TIP50 which are rated 400/500V. I picked
this oas it the only one whose number I vaguely recognise.
for about 45mA DC at 300V.
Has anyone used these for HT supplies or what else do you use?STP2NK60Z is my sort of 'all purpose' N-MOSFET. 600V with built in
gate zener protection and relatively inexpensive. A few pennies less
than a TIP50 but more current and no base drive.
For power supplies I tend to use them as cap multipliers (note that a
cap multiplier is not a reservoir) and screen regulators. I've also
used them as source (cathode) followers when short a triode.
in the power supply for a Single Ended amplifier, are you willing to
share your capacitance multiplier design?
Sure. I used it on the headphone amp breadboard and, as fortune has
it, it's posted on the website.
http://flipperhome.dyndns.org/headphone%20amp.htm
Two ways to do the resistor divider. One is from input V to ground but
with large voltages you can end up with difficult values so I run it
from input to output.
If you combine it with a regulator, using zeners in the grounded leg of
the pot divider, you avoid difficult resistor values and get a fixed
output voltage too.
You want enough drop to cover MOSFET gate threshold, input ripple, and
supply droop. If I remember correctly that one has about 10V across
it.
Regards,
John Byrns
Cheers
Ian
Hi all,
Instead of 6CY7 I would have thought a pair of 6SN7, 6CG7, 12BH7, 12AU7
would be a lot "stronger" than 6CY7, which is Ra = 52k, µ = 68,
so rather like 6SL7.
The "capacitance multiplier" is fine, but usually the R divider
is between the input Vdc and 0V.
Or as JB says, have a zener diode string, or a voltage reg tube to
fix the gate voltage. BUT, zeners are noisy, so you should have a
series R from top of the zeners to the gate, say 10k, then 10uF to 0V to
filter the noise at the gate.
And then you need a seroes R of say 100 ohms between C7 reservoir cap
33uF and the mosfet drain.
If you short the source output to 0V, the mosfet is turned on fully and
tries to discharge
C7 too fast, so POOF goes it, and you cannot get the smoke back in.
So you also need another series R from the gate filter to the gate, say
1k, and a transorb
or string of diodes or zener to pull the gate voltage down with the
source voltage without relying
on the little internal zener inside the mosfet.
If the input C37 is shorted to 0V, current tries to flow backwards to
the short and
the mosfet is also allergic to this, so a 3A diode needs to be placed to
allow the flow,
but not through the mosfet.
After blowing a few fragile mosfets, I learnt all about protection
measures everywhere.
Patrick Turner.
.
- References:
- TIP50 for HT regulator
- From: Ian Thompson-Bell
- Re: TIP50 for HT regulator
- From: John Byrns
- Re: TIP50 for HT regulator
- From: Ian Thompson-Bell
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