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Registered Member #1327
Joined: Mon Feb 18 2008, 12:13AM
Location: North Ridgeville, Ohio.
Posts: 38
I never thought to use a battery. I have an extensive circuit using the the supply voltage, transforming it down, then converting it to 12vdc. It never occurred to me to simply use a battery. What the h3ll was I thinking...... D.L
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
buzzer wrote ...
I tried to buy an SCR gate drive from the largest manufacturer of gate drives in the US. The engineer for that company said they did not make a drive for my applicaion, "just anode fire it from the capcitor bank". I discharge the caps at 200V with a 470 ohm resistor in series to the gate. It works fine. The engineer said he did not think the 9V battery would properly fire the SCR.
Have you try Digikey? I got my 800V 50Amp rated one there, and I've used it with 6 of my 400V 470 uf capacitors and it works great. I also got my 1000V 6Amp diodes there xD
Registered Member #1451
Joined: Wed Apr 23 2008, 03:48AM
Location: Boulder, Co
Posts: 661
You can sample some MOSFET drivers from Texas Instrument that work very well to drive an scr... the UCC37322 can give 9 amp pulses and is plenty fast enough. TI is a great place, you can sample the parts and they will send then FEDEX for free. Just use discretion when sampling !
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
Commercial gate drives Use a different method. Rather than giving a direct pulse, they flat line, then ramp up at ~5v/us to ~10x the rated gate voltage, peak for a certain time, ramp back down, flat line, and finely go to zero. These methods maximize di/dt capability.
Registered Member #680
Joined: Fri May 04 2007, 03:20PM
Location:
Posts: 15
I trigger the gate from the capacitor bank charged to 200V with 470 ohm resistor in series. When the engineer told me to trigger the gate this way, I asked him if that was too many volts. He said no, "dont worry about the volts, the current is what tiggers the gate". Does this sound correct?
Registered Member #1062
Joined: Tue Oct 16 2007, 02:01AM
Location:
Posts: 1529
The SCR has a silicon layer that triggers it. The silicon is not a dielectric, so it shouldnt break down under around 20v. Current is what triggers it, but to much voltage, you will ruin the SCR, and just get a nice beefy wire :).
I think the 470ohm resistor will provide enough of a voltage drop, and the current draw will be ~.4 Amps. It will trigger, but not at the best efficiency. Look at the datasheet for the triggering waveform.
Registered Member #680
Joined: Fri May 04 2007, 03:20PM
Location:
Posts: 15
Without getting too complicated, what would be a more efficient setup. I looked at the data sheet but did not really understand it. Is a battery and resistor better? My electronics knowledge is very limited, any help is greatly appreciated.
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Silly SCR question
!