Control scheme for power tool having a brushless motor

A power tool comprising:

• a housing;
• an electric motor disposed within the housing;
• a power switch circuit disposed between a power supply and the electric motor;
• a main controller arranged to control a switching operation of the power switch circuit to regulate a speed of the motor, and is configured to monitor at least one of a speed or a rotational direction of the electric motor and deactivate the power switch circuit upon detection of fault condition associated the speed or the rotational direction of the electric motor;
• a redundant controller configured to monitor at least one of the speed or the rotational direction of the electric motor independently from the main controller and deactivate the power switch circuit upon detection of fault condition associated the speed or the rotational direction of the electric motor;
• a main solid-state switch arranged to activate a supply of power to the electric motor;
• a secondary solid-state switch activated via the main controller and coupled to a gate of the main solid-state switch;
• and
• a third solid-state switch activated via the redundant controller and coupled to the gate of the main solid-state switch in series with the secondary solid-state switch.