I would definitely recommend considering PWM drive of motors in terms of the motor current as a function of motor speed, PWM duty, and supply voltage, rather than an effective voltage. This is because the transfer function from duty to effective voltage is moderately nonlinear overall and very nonlinear near zero duty. Taking this nonlinear voltage expression and using it in a simplified voltage-driven motor model will result in complex equations which are not very accurate in predicting motor behavior. Is this a brushed or brushless motor? A brushless motor driven by PWM is, as some have pointed out, effectively a buck converter because the inductance of the motor acts to create a voltage drop between the back EMF and the supply voltage. If you drive the motor with a sinusoidal current and vary the phase of this current relative to the back-EMF then you can also make it work like a boost converter (i.e., produce torque even when the back-EMF is higher than the supply voltage). This is often called either phase advance or field weakening (this latter term comes from the fact that the out-of-phase current in the coils produces a field which opposes or weakens the permanent magnet field as seen by the coils themselves). Brushed motors have the additional property that the commutation transients dump the stored magnetic energy in the motor coils (instead of 6-step commutated brushless motors where most of the stored energy is fed back into the supply via the body diodes of the driving MOSFETs or the protection diodes added to the switching elements if they are BJTs or IGBTs). This is slightly less efficient but it does reduce the effect which the motor inductance has on the electrical dynamics of the motor. If PWM is operated at a high enough frequency that the current flow is continuous through the motor coil from PWM cycle to PWM cycle (which is almost certainly what you want because it is more efficient and more linear in duty to torque relationship) then there really are only two kinds of PWM for a two-terminal (brushed) motor: on-reverse and on-shorted. on-reverse means that you alternate between applying positive and negative voltage to the motor during each portion of the PWM cycle (positive during the ON portion and negative during the OFF portion, assuming positive effective voltage is desired). on-shorted means that you short the motor during the off portion of each PWM cycle. There is no true OFF because even if you turn off all switching elements the protection diodes will cause current flow from the motor inductance back into the power supply, which is the same thing as on-reverse operation (but less efficient because of the diode voltage drop). On-shorted prevents this backflow into the power supply but it produces less maximum braking torque and prevents useful regenerative braking. Sean On Wed, Jul 4, 2018 at 10:01 PM, Jason White < whitewaterssoftwareinfo@gmail.com> wrote: > I need reversal, it is a solenoid/valve controller used for hydraulics in > aircraft. Size is rather constrained so PWM on the bridge is preferred. > > On Wednesday, July 4, 2018, Harold Hallikainen > > wrote: > > > What is the advantage of using the H-bridge in this application over ju= st > > using a buck regulator? The buck regulator would use just one switching > > transistor, a "catch diode," an inductor, and an output capacitor. This > is > > assuming the motor only needs to rotate in one direction (no voltage > > polarity reversal). > > > > Harold > > > > -- > > FCC Rules Updated Daily at http://www.hallikainen.com > > Not sent from an iPhone. > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > -- > 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 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .