Abstract: A method and device to protect a drive circuit of a power assist motor from an over-current condition. A sensor takes instantaneous measurements of the current provided to the motor. A charge accumulation determining function determines charge accumulation from the instantaneous current samples. When the current provided to the motor exceeds a threshold value and the determined charge accumulation exceeds a threshold charge accumulation, the current provided to the motor is decreased. When the current provided to the motor is less than the threshold current value for more than a predetermined period, the determined charge accumulation is reduced by a predetermined factor. After the charge accumulation has been reduced below a predetermined threshold, the current provided to the motor is increased.

Abstract: A method and device to protect a drive circuit (32) of a power assist motor (22) from an over-current condition. A sensor (24) takes instantaneous measurements of the current provided to the motor (22). A charge accumulation determining function (28) determines charge accumulation from the instantaneous current samples. When the current provided to the motor (22) exceeds a threshold value (40) and the determined charge accumulation exceeds a threshold charge accumulation (50), the current provided to the motor (22) is decreased. When the current provided to the motor (22) is less than the threshold current value (40) for more than a predetermined period, the determined charge accumulation is reduced by a predetermined factor. After the charge accumulation has been reduced below a predetermined threshold (92), the current provided to the motor (22) is increased.

Abstract: Current flow between a battery (14) and electrical ground (18) and through a load (16) is controlled by an apparatus (10). Preferably, the load (16) is a seat heat element. A current direction sensitive MOSFET (34) acts as a switch to control the current flow. The MOSFET (34) has a source (40) connected to the load (16), a drain (42) intended for connection to a positive terminal (26) of the battery (14), and a gate (46) for receiving a control voltage. Transistors (56, 66) control the voltage at the gate (46) of the MOSFET (34). The apparatus (10) is self-protecting against damage upon reverse polarity connection of the battery (14). A switch-protecting resistor (36) is intended for connection to electrical ground (18). The switch-protecting resistor (36) provides a path for electrical energy from the battery (14) to the gate (46) of the MOSFET (34) when the battery (14) is reverse polarity connected.