mosfet h-bridge design

[visky]

I would like to built PWM servo motor amplifier for up to 5Amp continius current 19Amp peak current and up to 50Volts.

It should be designet to run on frequency from 15khz - 50khz ( typical 20-25khz) and three logic inputs : enable , PWM ,direction.

When PWM is low and direction is low motor is brakeing
if PWM is high and direction is high motor is brakeing.

Olso i would use LM338 for current limit.

Anyone make something like that or maybe has got circuit schematics?

I do not wish to use microcontrolers!
It should be made with logic gates (and,or,xor ) or high frequency drivers.

[visky]

I am thinking to use L6385 high voltage high and low side driver or IR2110.

I don't know how to wire it with h-bridge.

Can i use High input for PWM signal and Low input for direction ?

Look at this simple h-bridge and tell me how to wire high and low outputs.

[epineh]

The 2110 has an enable (or shutdown) pin so if you want a simple way to do that then pick that one.

The H bridge you posted is using P channel FET's for the high side, generally using a gate driver chip you will use N Channel FET's for high and low side, the bootstrap circuit will provide a min of 10V above motor supply to turn the high side to full enhancment. The datasheet you posted gives you the schematic required, as for using PWM and direction you have to ensure the micro or processor board will not put out 100% on or off for the PWM values as this will cause the bootstraps to lose their charge and the high side FET's will not turn on, or maybe partly so, and burn up.

I am not sure about your braking idea, this will mean it is always braking when the PWM goes high in one direction and when the PWM is off in the other direction, could cause problems.

You will generally have to make sure the PWM and /PWM are not on at the same time with the 2110 as this will cause both high and low side FET's to turn on in the same half bridge, this will cause smoke to come out

I happen to be starting a new design with the 2110 for a few reasons, I can give you the schematics once tested if you wish.

What is your processor stage ?

Russell.

[Herbertkabi]

http://www.robotpower.com/products/
http://tech.groups.yahoo.com/group/osmc/
Ask Chris Baron,
Regards,
Herbert

[visky]

What about using two IR2110 or other,four N-mosfets and this logic input.

If you pull 5V to enable you will allways have just 2 mosfets on.

[epineh]

I am doing something similiar, but I am putting my DIR signals on the low side, one DIR and one /DIR. One high side is getting PWM and DIR on one half bridge (the same half bridge that has the /DIR) and the other is getting PWM and /DIR. This way the low side is just switching according to the direction and the high side is switching according to the PWM and direction. The high side will have to be switched using PWM and DIR so the bootstraps have a charge time, remember the high side FET's are switched at a min of 10Volts above the motor supply voltage, which is the purpose of the bootstrap circuitry, but it needs to have a PWM to charge.

Russell.

[visky]

How to add current limit to this circuit?

For voltage up to 200Volts