Failsafe hardware brake mechanism for outdoor power equipment

1. An apparatus comprising:

a working assembly configured to perform a work function responsive to operation of the working assembly;

an electric motor that powers the working assembly;

a power source configured to selectively power the electric motor;

control circuitry for controlling operation of the electric motor; and

a brake function configured to selectively apply braking to the electric motor responsive to a brake initiation event, the brake function comprising a brake gate drive circuit that controls short-circuiting of a motor phase winding of the electric motor to perform the braking,

wherein the brake function is configured to apply the braking by short-circuiting motor phase windings of the electric motor without requiring an external power supply during application of the braking;

wherein the brake function is configured to open an isolation switch connected to a gate terminal of a MOSFET in response to the brake initiation event to disable a drive control signal for normal motor operation from the motor during braking, wherein the brake gate drive circuit is electrically connected between the isolation switch and a gate terminal of the MOSFET and the brake gate drive circuit is configured to activate the MOSFET and connect the motor phase winding to ground for breaking without interference from the drive control signal when the isolation switch is open;

wherein the control circuitry is configured to, in response to a release of a throttle control operator by a user, cause the brake initiation event after a preconfigured delay time period of a timer; and

wherein the control circuitry is further configured to, in response to a selected one of a loss of the power source to the apparatus including the electric motor and the control circuitry or a power turn off to the apparatus, cause the break initiation event instantaneously.

2. The apparatus of claim 1 , wherein the brake function comprises a first phase, a second phase, and a third phase, each of which includes independent circuitry for connecting a corresponding phase of the electric motor to a common point in response to the brake initiation event, effectively short-circuiting the electric motor.

3. The apparatus of claim 2 , wherein the brake function is configured to apply the braking in response to any two of the first phase, the second phase and the third phase receiving the brake initiation event.

4. The apparatus of claim 1 , wherein the preconfigured time delay is adjustable by an operator or a factory setting determined based on a device type of the apparatus.

5. The apparatus of claim 1 , wherein the brake function is configured to consume less than 50 μA at 15 V.

6. The apparatus of claim 1 , wherein disconnection of a trigger switch cable of the throttle control operator causes a brake initiation event.

7. The apparatus of claim 1 , wherein application of the brake dissipates about 70% to about 95% of motor rotational energy in motor phase windings.

8. The apparatus of claim 1 , wherein the apparatus is outdoor power equipment.

9. The apparatus of claim 1 , wherein the electric motor comprises a BLDC (brushless direct current) motor.

10. The apparatus of claim 1 , wherein the brake function is further configured to cause the brake initiation event in response to disconnection of any one of three phases of the electric motor.

11. The apparatus of claim 1 , wherein the brake function configured to open in the isolation switch is also configured to open the isolation switch to disable a low side output of a MOSFET driver, the isolation switch being connected between the MOSFET driver and the gate terminal of the MOSFET.

12. The apparatus of claim 11 further comprising a high side MOSFET, a gate terminal of the high side MOSFET being connected to the MOSFET driver.

13. Control circuitry for controlling operation of an electric motor that powers a working assembly of outdoor power equipment powered by a power source, the control circuitry comprising:

brake initiation event generation circuitry configured to generate at least one signal associated with a brake initiation event; and

a brake function configured to selectively apply braking to the electric motor responsive to the brake initiation event, the brake function comprising a brake gate drive circuit that controls short-circuiting of a motor phase winding of the electric motor to perform the braking,

wherein the brake function is configured to apply the braking by short-circuiting motor phase windings of the electric motor without requiring an external power supply during application of the braking;

wherein the brake function is configured to open an isolation switch connected to the gate terminal of a MOSFET in response to the brake initiation event to disable a drive control signal for normal motor operation from the motor during braking, wherein the brake gate drive circuit is electrically connected between the isolation switch and a gate terminal of the MOSFET and the brake gate drive circuit is configured to activate the MOSFET and connect the motor phase winding to ground for breaking without interference from the drive control signal when the isolation switch is open;

wherein the brake initiation event generation circuitry is configured to, in response to a release of a throttle control operator by a user, cause the brake initiation event after a preconfigured delay time period of a timer; and

wherein the brake initiation event generation circuitry is configured to, in response to a selected one of a loss of the power source to the outdoor power equipment including the electric motor and the control circuitry or a power turn off to the outdoor power equipment, cause the break initiation event instantaneously.

14. The control circuitry of claim 13 , wherein the brake function comprises a first phase, a second phase, and a third phase, each of which includes independent circuitry for connecting a corresponding phase of the electric motor to a common point in response to the brake initiation event, effectively short-circuiting the electric motor.

15. The control circuitry of claim 14 , wherein the brake function is configured to apply the braking in response to any two of the first phase, the second phase, and the third phase receiving the brake initiation event.

16. The control circuitry of claim 13 , wherein the preconfigured time delay is adjustable by an operator or a factory setting determined based on a device type of the apparatus.

17. The control circuitry of claim 13 , wherein in response to disconnection of any one of three phases of the electric motor, the brake function is configured to apply braking to the electric motor responsive to the brake initiation event.

18. The control circuitry of claim 13 , wherein the brake initiation event generation circuitry is configured to cooperate with a microprocessor to generate the at least one signal associated with the brake initiation event.