Robust voltage regulator

LM78L05 with a diode in the input for reverse protection?

This is bulletproof. :-D

Olaf

I had a big SOT-227 MOSFET blow up in an induction heater that ran from rectified 415V 3 phase, and every part on its isolated gate driver board was destroyed (discrete N&P DPAK MOSFETs that drove the gate, TC4421 driver chip right back to and including the optoisolator), apart from the zener diode regulator (for the isolated supply) which survived.

I suggest a big fat zener diode (perhaps a TVS) fed from a resistor with a lot of thermal mass (e.g. wirewound, not thin film or laser trimmed).

Wouldn't an LM70L05 hit with a cute 8/20us pulse go ape? That's my concern. A Zener looks silly enough to survive that.

Best regards, Piotr

A TVS zener would clamp input spikes and reverse voltage.

Just remember to protect it.

I'd start with a series diode and maybe also 100 ohms or so of series resistance, followed by a capacitor to ground before whatever is doing the regulating. 78L05 may be suitable. Depending on the nature of the "spikes" you may want a suitable clamp device on the regulator input such as a 12V transzorb and make sure the series resistor is watty enough. I wouldn't assume the regulator can handle it, I'd protect the regulator.

Yeah I was going to suggest a series R and then diode for reverse and zener for overvoltage... but I guess the one zener could do both jobs. GH

I recall an Infineon automotive rated regulator that does that, out of the box.

...

Oddly enough, the On Semi version is the first one I find thumbing through past designs:

Anyway, being automotive, everyone ought to be making them, have fun.

Tim

-- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website:

TL750/1 will handle +60/-50 (transient) in TO-92 or SOIC-8

I recall another NS one that I used in a design just because it had a tight (1%) tolerance on the output voltage so it avoided a reference.

One of my engineers had a brief passion for the TI e-fuse parts. Leadless, power pad, a bear to probe or replace, and they die hard, like a classic fuse.

Our policy is to never connect an IC directly to the outside world.

If the reservoir capacitor is big enough to ride out the brief -40V input spikes then even the series diode is not needed. Since efficiency is not important then a single series resistor will do and it will be robust and cheap. The only other part then needed is a 4.7 or 5.1V zener diode. Or TL431 if OP is fussy about hittimng exactly 5V.

piglet

You really are a total wanker.

...... Phil

Simple is good. 10mA current max, makes it pretty easy. George H. (I'm going to have to order some TL431's)

In the post-Brexit UK, is the mains voltage again officially 240/415 V or is it still the EU 230/400 V with large tolerances ?

How about measuring units in general, are they all imperial again ?

When are they going to switch back to pound/shilling/pence ?

The 78 series regulators tend to oscillate, if fed by a large resistance, so put a big capacitor to ground after the series resistor,

On Tuesday, January 26, 2021 at 5:15:30 PM UTC+11, snipped-for-privacy@downunder.com w rote:

Seem unlikely.

Most likely never. An enthusiasm for decimal currency predates the European Union by about a century, and now that they've got it, the primary educati on system would hate to have to switch back. I was taught it as a kid, and it took quite a while - time that could have been better spent on more usef ul subjects.

Yes a few TL431 (or their "pnp" brethren LM4040) are good to have in the experimentors parts box. Jim Thompson used them as kindof op-amps with a bandgap defined input offset voltage ;)

piglet

Try LM2940CT-5.0

Designed for automotive transients. There is an ISO or IEC spec for these.

Piotr Wyderski wrote:

Probably an LP2951. I use those a lot.

Cheers

Phil Hobbs