DC-DC conversion from 1 Kilovolt DC down to 12VDC (isolated)

It's done that way but relies on the caps being relatively close to equal. That can become dicey, at least for hi-rel projects.

(600V each)

divide even.

application.

It can work. But the days where color TV sets had SCRs in the horizontal flyback stages were not very happy days for consumers who had bought one. For the radio & TV repair shops those were happy days though ...

The, one sunny day, there's a weird brown-out situation and the 1kV comes on really slow. Then, the phone rings ...

On a sunny day (Sat, 25 Jun 2011 07:36:39 -0700) it happened Joerg wrote in :

Yes that was Blaupunkt. There old tube color set was 100% standard to spec, used in the studio for station RF monitoring. Then they went solid state, and almost EVERYTHING about that set was wrong. Thyristors in the H out broke down, coil getting too hot, HV regulation bad, IF bandwidth curve terrible, never a sharp picture.

Yes that actually happened. It is no problem with professional equipment, just specify a maximum rise time. :-) Let them do the work.

(600V each)

even.

application.

If 1200V abs max input is acceptable, an off-the-shelf half-bridge driver (from IR) can be used to drive commonly available 1200V or

If there is a need to keep production going, I'd avoid high voltage bipolar transistors that were designed for CRT (HOT drive) use- for obvious reasons.

Best regards, Spehro Pefhany

You do not operate then at their rated value, you stupid f*ck.

Do you not even know what headroom is?

Manufacturers build headroom into the parts. There's no reason to add more of your own, unless you have known transients or something.

John

Well with 1200v devices a bridge is good upto about 800v.

I think you've missunderstood the circuit I'm describing, probably my fault, the 50/50 is for the gate drive voltage levels, nothing to do with the primary. should be good to 60/40.

. Just like we used hemp and pipe dope when mounting

Cant waste hemp on plumbing!!

The spec is 1.0kV input. A 1.2kV part may or may not be okay.

Is it the room where you smoke your dope?

Best regards, Spehro Pefhany

On Saturday, June 25, 2011 7:36:39 AM UTC-7, Joerg wrote: [ about HV commutation]

(600V each)

OK, then use 800V units, and three in series... the bill will still be less than $10 at Digikey (Sharp PC4SF11YTZBF optocouplers). You get one free shorted triac before function is lost.

Now i just KNOW someone will chime in about the extra cost...

(600V each)

even.

application.

Watch out using triac or thyristors in this circuit. The dv/dt of turning one on can cause the other to turn on. You must limit dv/dt to below the data sheet max.

Cheers, John

It was several brands. TV sets going bad after just a few soccer seasons, and per Murphy's law the SCRs died during the 2nd half of a Feyenoord or Borussia game.

You could also play some tricks with a neon lamp. Those are cheap and will guarantee a snappy risetime when the gas in there ignites. And they are cheap.

optocouplers (600V each)

The cost is extra-extra when all six in the stack turn on together.

John

You can get 1500V devices from the ST PowerMESH series. Not too cheap though, around $4:

With the gate drive you'll have to make sure it gets above 10V at all times but stays well below abs max. For HV devices abs max is often

Duty cycle is very critical if you drive a split primary sans cap. At those voltages core saturation can cause the unit to blow some of its guts out. I'd go for capacitive coupling and cross conduction avoidance.

:-)

You wouldn't want to smoke the stuff that's used for plumbing. It's bone dry and probably not from well controlled fields. Meaning it could contain pollutants in the smoke. But no idea, I don't smoke anything.

optocouplers (600V each)

Not sure I understand this right. The price is ok but at 0.1A they'd burn over 200mW, seems a bit much to me. The OP needs up to 100W out of this converter. Ok, sinec one is on only 50% of the time maybe you can squeak by. But how'd you get around the sluggish turn-on time? 100usec isn't exactly a rocket :-)

Digikey has a sale going on for these, about $0.76/each if you take 600:

That's like the incredible sales deals my wife always finds out about, like very tender pork filet for under $3/lbs.

So, the fountain is at it's new place. Whew.

optocouplers (600V each)

I was hoping you'd supply the sound effects.

Tell me about it. Now the girls want another deck (which will be #3) behind the cabin. And they want a firepit so they can warm their toes out there on cold nights. On cold nights, why don't they just stay inside?

It's interesting to drive around Truckee now. There are lots of decks that were crushed by snow this winter. What sort of idiot designs a house with a huge sloping metal roof that dumps directly onto a deck? Or dumps directly in front of the garage doors?

John

optocouplers (600V each)

IME, at that voltage level, there's only a sharp and brief *POP* and then stuff that was there is no longer there. Just gone. The 2nd tube amp I built had 5kV on the plates and any mishap was followed by prying the pieces out of the carpet, the ceiling plaster, and so on. Unless the lid was on, then you could just unscrew the bottom panel and clean out with a hand broom.

Because their toenails are painted and so they don't want to wear socks? I'll never understand why women have to paint their nails. Well, and in S.F. probably some men as well :-)

In Bavaria huses have little "mini fences" from steel on the roofs, parallel to the gutter and a few feet up. That prevents sudden roof avalanches.

On a sunny day (Sat, 25 Jun 2011 11:18:06 -0700) it happened Joerg wrote in :

As far as I know Blaupunkt was the only one that used SCRs. And for sure the only ones with defective SCR I got in for repair.

Maybe you were thinking Sony KV1810, those had a silicon controlled switch in the power supply that would stay on because of bad soldering (the off signal would sometimes not happen due to intermittent contact). Boom.

SCR-sets I remembered from the days I repaired this stuff were also the Grundig Super-Color series and a Telefunken 600-something. The others I forgot, no Japanese sets though.

SCRs in the horizontal stage became a fad, and that was kind of the last straw for me and I stopped repairing TV set. At first production quality went downhill and now the quality of the design itself was not good anymore. That did it for me.

Can't remember ever having to repair a Japanese TV. Those things lasted and lasted. The only thing I ever did was modify a Mitsubishi so it could display PAL and NTSC. Gave it to the recyclers recently because we have no use for it anymore. Fully functional, kind of sad.

No engineer worth his salt designs a circuit using a component right at its rated value.

I knew I could expect you to not understand, and make a little fool of yourself attacking me over it.

I sometimes use parts at 2 or 3x their rated voltage or 10x their rated power. Sometimes that's the only way to get performance.

I made a statement about parts. If you consider that an attack, then enjoy.

John