T&L Publications

I am working on a power supply for an antique radio and need to design a regulator for the 135Vdc section of the power supply. Besides using a series of Zeners to create the voltage, is there a good regulator like the LM317 that will work for voltages that high? <p>Thanks,
Nevin

You can use a '317 as long as the difference between input and output is no more than 37 volts (I have a few that are good to 57V). The programming resistor (or programming Zener) will keep the adjustment pin at 133.75V. If the input is going to between 172 and 206 volts, use two; the first to drop it to 172V or less and the second to regulate at 135V. There are three pin regulators that are designed for up to 125V difference, but they require at least 10mA load at all times (among other things).

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by L. Daniel Rosa:
You can use a '317 as long as the difference between input and output is no more than 37 volts (I have a few that are good to 57V). The programming resistor (or programming Zener) will keep the adjustment pin at 133.75V. If the input is going to between 172 and 206 volts, use two; the first to drop it to 172V or less and the second to regulate at 135V. There are three pin regulators that are designed for up to 125V difference, but they require at least 10mA load at all times (among other things).<hr></blockquote><p>This is a good suggestion. Just keep in mind that your 317s will not be protected from an output short to ground. Also, I'm not sure what will happen at turn-on in the case where your unregulated input rises faster than the output can follow, as would be the case if you had a really high-value filter cap on the output (not too likely at 135 volts). This situation would be exacerbated if you had a hot disconnect (switch?) between your input and your 317, causing the input to rise very rapidly.
I would probably prefer using a high-voltage NPN as a bootstrapped emitter follower interposed between the unregulated supply and the 317, but unfortunately It ain't easy to post schematics here. If I find time, I'll draw up something that might work and post it on my (crappy) web page.<p>Ron

Oh yeah, Nevin- how much current do you need outta this regulator?<p>Ron

If it seems kind of awkward to work with the LM317(s), take a look at the TL783 from TI. It is good for 125 V from input to output. Figure 18 in the datasheet (linked to at the web page shown below) shows how to short circuit protect it when the input-to-output voltage is potentially greater than 125 V. As Mr. Rosa says, however, it does require a high minimum output current (15 mA). That can be oppressive if you don't need that much current to your load. If you wanted to bleed it off to a dummy load, for example, it would be almost 2 W.<p>TL783 page at TI

I have several of the LM317H laying around, I am just not sure how to make sure that the input tracks the output fast enough. <p>The amount of current I need is only 20 - 50 mA. very small.

Regular line voltage is 170vac P-P, with RMS of
approx. 120VAC. A power supply with no X-FMR, but an inductor & cap. before the bridge, & a small cap & hi-volt zener after the bridge may sustain the 135V, as long as the load current
doesn't draw down the voltage. The conduction
angle of the bridge will be the key.

Thanks for the help. If anyone is interested this is going into a power supply for an antique radio. (Battery Eliminator). Here are the specs<p>3V @ 3.5A
4.5V @ 40mA
9V @ 40mA
135V @ 30mA<p>When I am finished this should be a nice box just to have on the workbench. I am making all 4 supplies variable and short circuit protected. Plus the box will have a built in voltmeter.<p>That brings me to my next question. I would like to be able to set the overcurrent limit and display the results. I have solutions for currents less than 2A (maxim App Note 298), but I need something for at least 4A for the 3V supply. Does anyone now of a way to digitally set the max current limit for a source of greater than 2A?

The design for the 3.4 V merges a 4 amp 6 volt standard transformer with core modification.
The design of the transformer core plate is extended to allow additional windings that each produce 150 and 18 Volt at 200 mA.<p>Current adjustment by TRIAC pulse width, takes place on the 6 VAC secondary before the rectifier and filter capacitors.<p>The insertion point of the ammeter is between the 3.4V regulator and the load.<p>I most likely do not have all the criteria for a reverse compatability power adaptation for early era radios.<p>[ February 11, 2003: Message edited by: dim bulb ]</p>

Nevin:<p>A couple of thoughts on your antique Radiator PS unit. Initially seemed as though U was wanting a fixed 135V B+ section but U probably want as low as 45-90, etc.if used on other receivers.
Initially why not give a good look thru All of this site:
http://www.epanorama.net/links/psu.html
If you go the ‘317 route on lower voltage supplies the current max spec can be circumvented via the utilization of a ‘338 unit, as it’s a 5 Amp unit. Or my favorite method is to use a power PNP shunting/bootstrapping the top of the regulator circuit and the biasing/shunt/curr lim resistors scaling the division of the load, such that the reg circuit is producing its current specified portion of the current thru it and the ancillary power device(s) take the balance (brunt) of the load. I’ve gone this route up to 10 amps. For circuit info see:
http://ourworld.compuserve.com/homepage ... page12.htm
If you’re set on your Maxim circuit , it might also work to load share , so that 2 amps is thru its circuitry and 2 amps is thru the bootstrapped power xstr then you would know the current was twice what the metering specified.
Also U might check this unit:
http://www.geocities.com/tjacodesign/30 ... 0vsup.html
And finally, would definitely go the route of the x-former isolation, no raw AC hot line style of unit.<p>73's de Edd
[email protected] .......(Interstellar~~~Warp~~~~Speed)
[email protected]...(Firewalled-Spam*Cookies*Crumbs)

how bout a tv voltage regulator ?
str30135 ? it provides 1 amp current..?<p>just a thought,,,<p>BTW...Need any isolation transformers?

120v - 120v . 1.5 - 2 amps