1. Home
  2. Electronics Design
  3. TL783 - are there any newer high-voltage linear regulators?
  4. Page 2

TL783 - are there any newer high-voltage linear regulators?

Hmm, so, no specs on the coils. At least, I didn't see any more info on the main page (I'm not going to go digging).

So you want a high voltage slug of charge to overcome the inductance, then a minimum 12V when on? And the slug should be limited, so it stops charging the inductance beyond 60mA?

What's wrong with this? :)

formatting link

Q2 and D2 don't need to be 100V, but I presume you'll want similar turn-off speed.

Or if you don't want a hard 12V minimum, but always with current limiting (say for short circuit protection purposes), Q2 or preferably D1 can be enhanced with a CCS circuit.

DN3545 might not handle the energy needed (which is, hmm, 5H at 60mA is ~10mJ, that's not too bad), but there's TO-220 versions out there. I just threw down what was handy in my library...

You don't even need C1 if the DC-DC is designed properly. A good old fashioned UC3843 current mode controller will limit short circuit output current to a fixed value. You could make it boost on top of +12V, so D1 is actually the rectifier diode as well, C1 is really small (0.1uF or less?), and the switcher itself takes the place of Q1-R1. Q2-D2 would still be as shown.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Contract Design 
Website: http://seventransistorlabs.com
Reply to
Tim Williams
Loading thread data ...

The DMOS approach looks good. I tried the current limiter in LTSpice, and it works well:

formatting link

I'm not clear on why R3 works at 16 ohms. Vgs for that DMOS part is -1.5V, and that's what the SPICE model has. Supposedly, you should set R to Vgs/I, where I is the desired current limit. Or so says "Current sources and voltage references", by Harrison, fig 7.9. So R = 1.5V / 0.060A = 25 ohms. But in Spice, that's too big; 16 ohms works.

Here's the entire cap charger in LTSpice.

formatting link

This is a driver for 60mA current loop devices, powered from a USB port. There's a USB to serial controller, not shown. I've built and used this, but without the current limiter. Without it, it only works for 220 ohm 5.5H selector magnets. There are some other devices in the Teletype world that want 60mA but have different solenoids, so this thing needs current limiting to be more general.

John Nagle

formatting link

Reply to
John Nagle

The "Vgs" spec is the voltage at which there is *no* (or minimal) current.

Nothing is quite as abrupt as LTspice "idealisms" might imply >:-}

To see what I mean, "curve trace" the device: Sweep VDS with a small increment, say 10mV, while doing a STEP VGS in 100mV steps.

...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

             I'm looking for work... see my website. 

Thinking outside the box...producing elegant & economic solutions.
Reply to
Jim Thompson

Very long ago I found a AM radio by the side of the road in a pile of junk. It was a very cheap GE transformerless radio. From it I salvaged the audio output transistor, a TO-66 style case. This transistor was fed right from the 120 VAC rectified power line so it was capable of handling 160 volts. I used it to switch the selector magnets on my Model 15 TTY, I forget if I wired it up as 20 or 60 mA. Anyway, that transistor worked just fine for years. Oh and for current limiting I had a resistor capable of dropping about 120 volts from the 160 volt DC power supply, so it must have been around 2K or 6K or so. So anyway, you don't need a constant-current driver so much, a resistor should work just fine.

Reply to
George Gonzalez

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.