AVR-Chat

At 10:21 PM 12/9/04 -0800, you wrote:
>hi robert:
>sorry, i skip some description.my motor is a linear synchronous motor(LSM)
>
>(1) first i do a single phase hbridge cct which use 2 pchannel(high side) 
>n 2 nchannel(low side) power mosfet.left high side mosfet(drain) is 
>connected to gate of right low side mosfet. right hide side mosfet (drain) 
>is connected to left low side(gate) mosfet. which means when left high 
>side mosfet is on, then right low side mosfet will also on. same with 
>right high side mosfet n left low side mosfet will on together in next 
>stage. i use 2 BJT to switching both high side pchannel mosfet.so i set 
>two output from 8535 chip to the BJT throug 2 optocoupler without using 
>IR2110. everything goes find except i cant get purely squarewave output. 
>so any suggestions on the commands which can generate the squarewave waveforms.

You do realize the P channel MOSFET requires a different drive than the N 
channel?  One of the big (very big) advantages of using something like the 
IR2110 is that you can use N channels on both the high and low sides taking 
advantage of the far better N channel devices.

Oops I think I misread the above.  I'd skip using the optos and PFets and 
go directly to using the 2110.  Or I'd not use the 2110.  You will probably 
have enough to do getting one drive circuit to work along with the rest of 
what you want to do.

What do you mean you can't get a square wave?  Are you referring to duty 
cycle or the rise and fall of the edges?  If it's duty cycle just adjust 
your timing.

I'm more concerned about your frequency.  If you are driving some sort of 
DC (brushless, Switched reluctance etc) motor 50Hz is likely to produce a 
significant amount of ripple.

>
>(2) after that i will try 3 phase by building 3 set of the hbridge cct 
>above so totally 12 mosfet.
>     my professor ask me to do this instead of just using 6 mosfet in a cct...

Just a note: IR does make 3 phase drivers.

You actually need 3 full H bridges, not 1/2H bridges?

>
>(3) later only i will try use IR2110 to directly switching the 4 mosfet in 
>single phase hbridge cct without using 2 BJT....and then later switching 
>12 mosfet from output of the chip....but i m new in IR2110 and dont know 
>how to use it correctly...i dont know how to connect the Vb,Vcc,Vs,Vdd,Vss 
>and what voltage to supply them?
>
>
>(4) yes i have to connect optocouple 4N26 between IR2110 and 8535chip to 
>protect the chip coz later the supply voltage to 3phase cct may goes up to 
>100V (10A)..no choice...

Umm, the 2110 does provide isolation for up to 600V.  That should be 
sufficient for 100V supply.  IR does have app notes showing hookups for the 
2110 and this is the usual configuration.

>
>(5) my motor power supply is separated from the control power supply...

The ground (return) for the motor supply is separate from that for the 
control circuit?  Then for a 3-phase system running with a 50Hz square wave 
you are probably going to need between 4 and 6 isolated 12 to 15V supplies 
to run the gates.  At that point I would think something like Agilents 
optoisolated gate drivers would make more sense.

Running a pwm would allow you to get rid of 3 of those supplies.

Robert


" 'Freedom' has no meaning of itself.  There are always restrictions,
be they legal, genetic, or physical.  If you don't believe me, try to
chew a radio signal. "

                         Kelvin Throop, III