| ??? 06/23/06 19:48 Read: times |
#118971 - Didn't work :(( Responding to: ???'s previous message |
I put the TC4468 in with a 8V supply. The gate signal had good rise to 6V with a little ringing on that corner then progressed to about 7V before being shut off. Didn't really make any difference as far as temperature goes. Soooo... it must be the internal diodes causing the excess heat. I had a suggestion in another forum:
Jon, I think you may have to take the cathodes of the diodes to a voltage that is twice the motor supply voltage. The easiest way to arrange this is to have a zenner diode between the commoned cathodes and the motor supply voltage. I think one zenner is all you need but I may be wrong and you might need two, one for each winding pair. I think the reason why current chopping fails is that mutual inductance ensures that the diode on the 'off' winding shorts out the 'on' winding. The zener ensures that the undriven winding can rise to 2x Vcc without shorting out. Regards, Tim. I'm getting ready to order some 51V zeners and give that a try. If that doesn't do it then I'll just have to go with it, we had minimal FET replacements before and it ran close to the same temperatures. Jon |
