Electronics > Projects, Designs, and Technical Stuff

Driving lots of H-bridges thru isolated SPI, design ideas?

(1/2) > >>

hlavac:
Hi,

I need to find a way of driving lots ( 8 ) of reasonably powerful H-bridges (~48V,~5Aish) from an isolated SPI bus. I'd like the H-bridges to be all discrete N-MOSFETs.

I have looked at the various gate driving ICs but they seem too expensive to use for driving so many gates (4 per channel, *8 = 32 gates, 16 of them high side). This will get very expensive very fast :(

So, I'm thinking, I could create a shared gate driving power rails (Vmotor+10V, GND+10V) on the high power side, and switch the gates with some simple BJT stuff... can that fly? I'd also like some hardware shoot-through protection there to avoid the thing blowing up in my face when wrong data gets sent :)

Any ideas, component suggestions on how to do this, cheaply? Similar projects I could look at? Maybe protection circuitry suggestions? Is there a magic IC that will make this easy?

NiHaoMike:
Do the high sides need to be able to do 100% duty cycle or is less OK? Is each output being either high or low OK or does it have to be able to go open? What maximum switching frequency do you want?

hlavac:
These are for stepper motors, so I need 100% duty cycle I guess.
Going open is probably not required although would be nice for current control (slow decay). Or maybe it is to be able to let go of the motors.
I want quite fast PWM, above 25kHz, maybe up to 100kHz, and want it to be pretty high res as I want to play with sinusoidal driving of stepper motors  to reduce the motor noise.

Psi:
You can get optoisolators designed to drive mosfet gates. (2A peak output)

Maybe a multichannel one of those would be cost effective.

han:
I always use MC33151 for Mosfet Driver, you can get <$1 in large qty

Navigation

[0] Message Index

[#] Next page