DC Motor Control Circuit for Back-EMF Blocking and Braking

The patent converts the harmful back electromotive force into a beneficial braking mechanism. When the motor is switched from high speed to low speed or stopped, the back electromotive force is utilized to drive current through the braking switch unit, creating electromagnetic braking that rapidly stops the motor. This transforms energy that would otherwise be wasted into a useful function for speed control and stopping.

The patent introduces protective circuit components as intermediaries between the motor and the power supply/battery. The free-wheeling diode, discharge diode, and braking switch unit act as mediators that intercept and safely dissipate inductive voltage spikes generated during motor operation and commutation, preventing these spikes from damaging the battery or control electronics while allowing the motor to operate at high speeds.

The patent merges multiple protective functions into a single integrated second speed switch unit that combines both speed control and back electromotive force blocking capabilities. By integrating these functions and utilizing the body diodes of the semiconductor switches, the design achieves reliable protection against back electromotive force while minimizing the number of additional components required, thus reducing overall circuit complexity.

The patent converts the energy that would be wasted during braking into a useful function. When the braking switch unit connects the motor to ground, the resulting current flow through the motor windings creates electromagnetic braking that rapidly stops the motor. The energy dissipation during braking is transformed into a controlled deceleration mechanism, improving stopping speed while the protective diodes ensure this energy dissipation does not damage other circuit components.