Supplementary information: PWM frequency =3D 25kHz Motor Wattage 15W, 20V (I suppose low wattage could imply lowish inductance, I don't know the actual motor) Duty Cycle is always between 50% and 100%. -Jason White On Tue, Jul 3, 2018 at 4:17 PM, Bob Blick wrote: > Hi Jason, > > At high frequencies and <<50% duty cycle, yes, the ON/Hi-Z cycle will > average 0 volts. > > It depends on duty cycle, your PWM frequency and the motor inductance. > > The motor is an imperfect inductor. > > But generally what you say is entirely accurate. > > Friendly regards, Bob > > ________________________________________ > From: piclist-bounces@mit.edu on behalf of > Jason White > Sent: Tuesday, July 3, 2018 12:48 PM > To: Microcontroller discussion list - Public. > Subject: [EE] DC Motor PWM, Average Voltage? > > 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 > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 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 .