Hello PICList!

I am currently design my first piece of avionics hardware. For my
application I am driving a DC motor with an H-Bridge. I aim to (very
loosely) regulate the average voltage supplied to the motor to 20V over a
supply voltage of 20V to 40V using open-loop PWM.

I would like to know if my thinking is correct.

The H-Bridge contains two "Off" states: High impedance and braking.

With a 40V supply: If I PWM the H-Bridge between "on" and high impedance at
a 50% duty cycle the average voltage will not be 20V because of the back
emf of the DC motor.

Instead to achieve an average of 20V with a 50% duty cycle the H-Bridge
must be toggled between "on" and braking. This will eliminate the effect of
back-EMF on the average applied motor voltage.

Correct thinking?

Thanks,
Jason White
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.