Interactive simulation
H-bridge motor driver simulation
Forward, reverse, brake, coast — watch the current thread the bridge.
Forward and Reverse turn on one diagonal pair and PWM-chop the high-side one, so the motor sees 12 V times the duty. The other two modes are not diagonals at all: Brake closes both low-side switches to short the armature through them, and Coast opens all four. Neither chops anything, which is why the effective voltage reads 0 V in both. The travelling dots move at the armature current — fast while the rotor is still slow, easing off as the back-EMF catches up with the applied voltage, and turning round if you cut the duty on a motor that is already spinning. Never turn on both switches of the same leg (Q1+Q2 or Q3+Q4): that shorts +12 V straight to GND through two switches, which is the shoot-through a real driver spends its dead-time budget avoiding.
