Abstract: A bidirectional solid state power switch module includes two solid state switches, each having an antiparallel diode, connected in common electrode configuration by a juncture therebetween. A pair of unilaterally conductive paths, each poled to conduct in a direction to maintain current through the switch module which is cut off by turning off the adjacent switch, each connected to an extreme end of the switch module, the other end of said first unilaterally conductive paths being connected together to a first side of a capacitor, the opposite end of the capacitor being connected through a unilaterally conductive path to the juncture between the two switches, said second unilaterally conductive path being poled to conduct current that passes through either of said first paths and said capacitor.

Abstract: A fail safe gas furnace optical flame sensor uses a transconductance amplifier with low photodiode current to sense the presence or absence of a gas flame within the burner of a gas furnace. The photodiode signal appears as the only negative voltage signal in the circuit, and the equivalent resistance feedback network is redundantly designed, thus ensuring that no false flame-on conditions will be detected due to the failure of a single resistive component. Because it does not reside within the flame, the sensor is immune to false flame-off conditions caused by material deposition and corrosion of the sensor.

Abstract: A phase current reconstruction circuit for reconstructing a plurality of phase current waveforms for a brushless direct current motor having a plurality of phase windings, wherein the circuit operates equally well at all motor voltage ranges. The circuit is comprised of a plurality of differential amplifiers for detecting and amplifying voltage signal fluctuations of the detected signal voltage across a plurality of sense resistors exhibiting a low voltage drop regardless of a motor operating voltage employed; a plurality of analog switches for selectively gating the amplified signal voltages with proper phase timing to reconstruct the phase current waveforms; and a plurality of output amplifiers for amplifying the reconstructed phase current waveforms.

Abstract: Control circuitry for a brushless direct current motor is premised on constructing phase to phase back emf signals representing the differences between the back electromotive force efforts produced in each phase winding of the motor. The phase to phase back emf signals are used to produce logic level signals having logic level changes at the zero voltage crossover points of the phase to phase back emf signals. Detection of the zero voltage crossover points is dictated by selectively activated comparator circuits. A method is also disclosed as to how the values of certain circuit elements may be derived.

Abstract: A shift actuator for a vehicle transfer case includes a bidirectional electric motor for positioning gearing in the transfer case. An indicator mechanism associated with the drive train between the motor and the transfer case provides electrical signals indicative of the actual position in, and thus operating state, of the gearing in the transfer case. A selector switch provides electrical signals indicative of a desired operating state of the transfer case gearing. An electronic control is responsive to an input from the selector switch and to the indicator mechanism for effecting rotation of the motor in a predetermined one or other direction to attain the desired operating state. The indicator mechanism includes a contact plate, which rotates with the drive train, and a set of stationary contacts. A conductive pattern on the contact plate identifies the positioning of the operating states of the transfer case gearing.