Abstract: A digital, back EMF, single coil, sensorless up/down counter frequency adjustment system for a d.c. motor includes means for detecting the occurrence of a null voltage during the back EMF commutation state of a field coil; counter means for counting in one direction during the back EMF commutation state and for counting in the opposite direction when the null voltage is detected; means, responsive to the counter means, for ascertaining the final count of the counter means; and means, responsive to the means for ascertaining, for adjusting the frequency of initiation of the commutation states when a non-zero count is ascertained for synchronizing the field coil and the rotor.

Abstract: A pulse width modulated inductive load controller including a load switching circuit having a plurality of switches which are operative in pairs; each pair including first and second switch devices for controlling power to a load. Commutation logic enables various sequential combination of pairs of switch devices and a clock defines the operation period of each sequential combination of switch device pairs. Pulse width modulation circuitry controls the closed time interval of the switch devices during the operation period of each combination of switch device pairs. Transition control circuitry maintains closed at least one of the switch devices in each sequential combination of switch device pairs after the other switch device is opened, thereby assuring that any regenerated current from the previously energized load coils is provided a path to recirculate through the load.

Abstract: A circuit for monitoring the heat dissipation capacity of a cooling medium by defining the initial heat dissipation capacity of the medium at a predetermined temperature of a temperature-sensitive element immersed in the medium. The circuit senses a change in temperature of the element and restores the temperature of the element to the predetermined temperature. Based on the level of power required to restore the temperature of the element to the predetermined temperature, the circuit defines the adjustment in heat dissipation capacity of the medium required to return the medium to the initial capacity. Also disclosed is a system including such a circuit which modifies the heat dissipation capacity of the medium by the required adjustment to return the medium to the initial heat dissipation capacity.