Brick driver

I proudly present an add-on unit for my PLL driver that allows it to drive IGBT bricks!

The power to harness lightning! Oh yes

This is a quick lash-up of the prototype.

Prototype gate driver and DC-DC isolated power supply

Here you can see it in action. The upper trace is the drive signal going into the circuit, the lower trace is the IGBT gate voltage, going from -12V to +24V. It seems to be pretty fast I guess it will slow down some more once the IGBT gets some collector voltage on it and the Miller effect kicks in, but it should still be more than fast enough for the size of coil I have in mind.

Gate voltage of a CM600HA-24H brick

circuit description

schematic click to enlarge

I used a ZVS-type oscillator to generate a sine wave at 60kHz. I chose a sine wave because I felt a square wave might crosstalk onto the gate drive signals (which I wanted to put down the same multicore cable as I am connecting the drivers to the mainboard with USB leads)

The ZVS puts out about 40V RMS at 60kHz, which feeds each gate driver through its own isolating transformer. I chose to do it this way because it just seemed better than trying to make multiple isolated windings on the oscillator transformer. Finally, a choke input filter completes the job, giving 36V DC from the 40V input. The choke input filter gives good regulation so no other regulator is needed. The zeners divide the 36V into 24V and 12V, and also keep the filter choke above its critical current for continuous conduction.

One reason why I like this system is that it has free protection built in! Every fault condition I can think of that would damage the main IGBTs, also causes the gate driver to draw excessive current through the ZVS. Since the ZVS is powered off the PLL driver board's +15V rail, that will trigger the existing undervoltage trip on the PLL driver.

I tested it by shorting across each gate drive MOSFET and by shorting the IGBT gate terminals. Sparks flew and the ZVS current consumption leapt well over 1 amp (it's normally 150mA)

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