H-bridge and DC motor driver
Work out a brushed DC motor's stall and running current, the PWM current ripple for sign-magnitude and locked-antiphase drive, the PWM frequency you need, the H-bridge's conduction, switching and dead-time losses, and what coasting, braking and plugging do.
Added
Works with
- Brushless motors — inside and how they are driven Electronicsthe three-phase bridge that drives a brushless motor, with six-step, FOC and the same switching losses
How to use it
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Currents — stall current V/R (every start draws it), and the running current from the back-EMF at a given speed.
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PWM ripple — sign-magnitude drive (one leg switching): ΔI = V·D(1 − D)/(L·f), worst at 50 % (V/4Lf); locked antiphase (both legs): ΔI = V(1 − m²)/(2Lf) with m = 2D − 1, worst at standstill (V/2Lf). The tool suggests the frequency that keeps the ripple under 20 % of the current.
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Losses — conduction 2·I²·Rds(on) (two transistors in the path), switching ½·V·I·(tr + tf)·f per switching leg, and body-diode conduction during dead time, with the hottest transistor’s temperature rise.
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Braking — coast, brake, plugging, and how the inductive energy is clamped.
Related: transistor & MOSFET switching (gate drive, junction temperature), current sensing, thermal.
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