6v & 90v DC Power supply
in [Design]
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From: James F. Mayer on 26 Dec 2005 21:02 I need to generate 6v DC and 90v DC from a 12v DC automotive electrical system to power an RT-70A/GRC surplus military radio. I need about 250 mA at +6 volts and about 75 mA at +90 volts. I was thinking about using the guts from an old battery back up but it would be a bit of a kluge. Are there any 90 volt regulators in the 78xx series? How do I get the voltage up to where I can get something that I can get the 90 volts from. Getting the 6 volts doesn't seem to be a problem. A 7806 off the battery should work for that unless any of you can see a problem doing that. Maybe the common common would be a problem. Right now I'm running it off of an HP6299A and an HP6236B with commons jumpered. I'd like to be able to go portable with it.
From: Joerg on 26 Dec 2005 21:57 Hello James, > I need to generate 6v DC and 90v DC from a 12v DC automotive electrical > system to power an RT-70A/GRC surplus military radio. I need about 250 mA > at +6 volts and about 75 mA at +90 volts. I was thinking about using the > guts from an old battery back up but it would be a bit of a kluge. Are > there any 90 volt regulators in the 78xx series? How do I get the voltage > up to where I can get something that I can get the 90 volts from. ... You can build a step-up or flyback with the LM3478. Tough to solder though, it's a TSSOP package. Don't know what current you need but just pick a suitable FET. For 6V I'd use a buck regulator instead of wasting 50% of the energy in a series regulator. Regards, Joerg http://www.analogconsultants.com
From: Bill Turner on 26 Dec 2005 23:14 ORIGINAL MESSAGE: On Tue, 27 Dec 2005 02:02:15 GMT, "James F. Mayer" <jfma(a)ix.netcom.com> wrote: > I need to generate 6v DC and 90v DC from a 12v DC automotive electrical >system to power an RT-70A/GRC surplus military radio. I need about 250 mA >at +6 volts and about 75 mA at +90 volts. I was thinking about using the >guts from an old battery back up but it would be a bit of a kluge. Are >there any 90 volt regulators in the 78xx series? How do I get the voltage >up to where I can get something that I can get the 90 volts from. Getting >the 6 volts doesn't seem to be a problem. A 7806 off the battery should >work for that unless any of you can see a problem doing that. Maybe the >common common would be a problem. Right now I'm running it off of an HP6299A >and an HP6236B with commons jumpered. I'd like to be able to go portable >with it. > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I'd use one of those small inexpensive inverters which put out 120vac and then use a conventional transformer/rectifier system. You can pick up the inverter at any truck stop. 73, Bill W6WRT
From: Highland Ham on 27 Dec 2005 00:11 > I'd use one of those small inexpensive inverters which put out 120vac > and then use a conventional transformer/rectifier system. You can pick > up the inverter at any truck stop. ============================ Those 'inexpensive inverters' might need some attention in respect of the 'hash' they create , possibly causing interference in the receiver. Frank
From: Fred Bloggs on 27 Dec 2005 00:13
> I need to generate 6v DC and 90v DC from a 12v DC automotive electrical > system [to power an RT-70A/GRC surplus military radio]. I need about 250 mA > at +6 volts and about 75 mA at +90 volts. [ I was thinking about using the > guts from an old battery back up but it would be a bit of a kluge.] Are > there any 90 volt regulators in the 78xx series? How do I get the voltage > up to where I can get something that I can get the 90 volts from. Getting > the 6 volts doesn't seem to be a problem. A 7806 off the battery should > work for that unless any of you can see a problem doing that. [ Maybe the > common common would be a problem. Right now I'm running it off of an HP6299A > and an HP6236B with commons jumpered. I'd like to be able to go portable > with it. ] > > 90V @70ma is only 6.3W and a step-up of no more than 90/12=7.5. This would be something like a 24VAC center-tapped transformer turned backwards with a multivibrator drive of the secondary at 50-60Hz and the usual primary is rectified and capacitor filtered to produce the 90V. Since the reflected current is only about 1/2A, you can then feedback the rectified HV to drive an error amp that regulates the center tap down to 9V or so. |