H-Bridge is a method that allows us to control the DC motor rotation direction by changing the polarity of the input voltage so the current that flows through the motor will be reversed by using 4 switches. Dc Motor Speed Control Using PWM DC Motor Direction Control Using H Bridge In the picture down below we apply this method in different Duty Cycle so you can see the difference of average input voltage with each Duty Cycle percentage. So let’s just say you need to rotate the DC motor at the maximum speed so you need to apply 12V average input voltage to do that you need to set the Duty Cycle at 100% percentage. The Duty Cycle is a series of on-off pulses, so to increase the motor speed you need to apply a higher average input voltage as result higher duty cycle percentage, and to decrease the motor speed you need to apply a lower average input voltage as a result lower duty cycle percentage. PWM (Pulse Width Modulation) is a method that allows us to control the DC motor speed by changing the average input voltage value by adjusting the on-off pulses series of the Duty Cycle.

To control a DC motor you need to control the speed and rotation direction, so there are two methods to do that: