Abstract: An improved series-pass over-voltage protection circuit for a motor vehicle electrical system includes first and second parallel connected power paths that respectively provide low current capability with low quiescent current drain, and high current capability with low on-resistance. The first power path, embodied by a P-channel MOSFET, supplies pass-through battery current to quiescent loads such as an engine control module during periods of vehicle inactivity. The second power path, embodied by at least one N-channel MOSFET, is activated by a gate voltage power supply during periods of vehicle activity. The second power path is configured to limit the circuit output voltage to a higher value than the first power path, so that the over-voltage protection during periods of vehicle activity is accomplished by the second power path.

Abstract: A governor circuit for limiting the maximum speed of an internal combustion engine is effective to minimize overshoot at all ranges of engine acceleration. The system includes a circuit responsive to the engine speed which provides control signals to a solenoid valve which, in turn, controls a vacuum actuator which can override a manual throttle control to move the throttle toward closed position when a governed engine speed is approached. A control circuit provides a signal having a lead component and an integrated signal which comprises a stabilizing component and an integrated speed component. The integrated signal is provided by an integrator having a low sensitivity and high gain at low engine accelerations and a high sensitivity and low gain at engine accelerations above a predetermined switch point. The resulting control signal controls a duty cycle oscillator which actuates the solenoid valve.