Re: Need design for 120VDC 60mA constant current supply
- From: linnix <me@xxxxxxxxxxxxxxxxxx>
- Date: Sun, 8 Mar 2009 10:23:09 -0700 (PDT)
On Mar 8, 9:25 am, John Nagle <na...@xxxxxxxxxxx> wrote:
I'm looking for a design for a 120VDC 60mA constant current
supply. This is what's needed to drive old 60mA Teletype machines.
The classic solution is to run a constant voltage supply through a
2K 10W resistor, but that approach dissipates 8W when idle, which
requires a big resistor for a board-mount design. I'm currently
using a big 10W thick-film resistor, and it works fine, but adds
1.5" to the board height and needs ventilation.
So I'm looking for a switch-mode constant current supply.
This design from EDN looks promising:
http://www.edn.com/article/CA217668.html
But the components are only rated to 40VDC, and even the "HV" version
only goes to 60V. Also, it's a design from 2002; there are probably
better switching regulator components available now.
The On Technologies NCP3065 part (a constant current driver
for LED strings) looks promising, but won't go to a high enough voltage.
Any suggestions?
John Nagle
When all else fails, relay works. You can also try with some high
voltage (600V) MOSFET. You will need fractional voltage sensing and
switching, possibly with a microcontroller.
.
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