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HF gate drive experiments

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LAN_403

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Fri Oct 13 2006, 05:55AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

GO PB

You never cease to amaze me... I couldn't even get decent gate drive at 700khz, you have perfect drive at 12mhz!

And my old standby, I want plasma!

Avalanche

Fri Oct 13 2006, 07:57AM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Nice one, looks like you're getting that gate drive perfected! What are the heatsinked devices on the pcb, are they normal transistors or mosfets? Just trying to figure out what you're using now schematic wise

I'm off to Maplin in a few minutes when the traffic has died down, couldn't sleep properly thinking about class-e

Steve Conner

Fri Oct 13 2006, 10:30AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Wow, neat! Are you using any sort of matching network between the gate driver chips and the MOSFET gate, or just hard driving it? Also, is that an IRFP450LC or just a plain IRFP450?

ragnar

Fri Oct 13 2006, 11:10AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

Hi Steve, Avalanche,
The heatsinked IXDD414s on the PCB are top secret, and I can't tell you what they are. =-P

Ah, does a resistor count as a matching network? I'd also like to proudly note this is a plain boring cheap IRFP450, as opposed to the LC version which costs 5x as much. ^^

No series L or series C, I'm just 'hard driving',yes (although not hard enough...).

WaveRider

Fri Oct 13 2006, 01:07PM

Registered Member #29 Joined: Fri Feb 03 2006, 09:00AM
Location: Hasselt, Belgium
Posts: 500

Goodo BP! It's always best to go for brute force first..

Make it look pretty later..........

teravolt

Sat Oct 14 2006, 05:08AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

Hello all, I have also made a version of driver that uses the IXDD414CI. This is my second version of this circuit and I have been able to get 0 to 5Mhz out of it. The smallest pulse width is about 80ns. It has on board current protection and sends out a fault pulse. this driver is isolated to about 1200v by opto's and uses a raw dc foating supply to power the high side. I'm not able to give formal shematic or o-scope print at this time but will in a thread later. Thease drivers are pritty robust and I have goten them down to 20ns on a proto board. Presantly I am driving a standard igbt IXGH32N60C with about 1.3 ohms for a time of 100ns with about 16ns rise and fall times. This pcb will accomidate a F/O link or directly with optos.

Marko

Sat Oct 14 2006, 12:48PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

These boards look absolutely awesome teravolt.

Have any higher resolution pics or schematics?

(I'm wondering what all those IC's and strange looking components are for

)

Avalanche

Sat Oct 14 2006, 02:40PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Nice boards there!

Anyway along the same lines as BP's gate driver torture, I tried the MC34151P driver at 12Mhz yesterday. It claims to be a high-speed driver, and it has a schmitt triggered input. Just not high enough though

With 12Mhz matched into its input, initial power-on looked promising with a fairly good sine-looking output, which didn't last long before it died away to nothing

This was with no load. The chip didn't even get hot though, it just seems to shut down! Switching off for a few seconds and back on does the same, and I just cannot kill the chip.

So anyway I now have a nice 0.3 watt 4-24Mhz transmitter using various crystals and harmonics of, lets see if I can do anything constructive

teravolt

Sat Oct 14 2006, 06:45PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hears a larger picture, my next version of this will use 2 IXDD414CI in parallel for driving brick gates at 30A peak. it will have no current feadback and be just a raw driver but will be fully isolated. I am hoping to get 100ns rise and fall times for large bricks but I don't know if is pausible. The trick is to reduce resistance and inductance as much as pausible between the driver and gate. The only problem with thease drivers is that they need a seperate power supply or DC to DC converter if you want to float them wich leeds to complexity of the bridge. N.B.

Avalanche

Tue Oct 31 2006, 06:19PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Anyone had any further luck with gate torture?

After quietly building several prototypes and blowing them up over the last few days, I've managed to get a fairly nice gate drive into an IRFP460 at 12Mhz, using a crystal oscillator and a class A-B RF amplifier matched into the gate. The A-B output stage is driven by the 74HCT logic chip, via a mini impedence matching transformer into the bases.

I am now absolutely gutted though, because 5 minutes ago I was running the thing without any heatsinks on my transistors (couldn't wait to check it out

) Nice 12Mhz across the gate went down to nothing as I turned up the bias too much, and the board hissed at me

As soon as I manage to find some replacement transistors (I think I have some lying around) I'll replace them, fit a heatsink, and post some scope shots, but for now you'll have to imagine the scope shots and just make do with a picture of my HF driver board

(I think I need to cut down on capacitors next time

)

Failed prototypes:

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