Abstract: A driver circuit for high frequency transistor type switches, comprising two sections; a positive (+) drive and a negative (-) drive, both sections being supplied with a high frequency signal by a square wave oscillator source. The sections are connected in parallel to a control generated input drive signal. In the negative drive section, the input drive signal is first inverted before being processed. Each section contains precise circuits for routing a high frequency carrier signal, for increasing input drive signal power gain, for providing independent positive and negative slope control, for providing exceptionally high voltage and noise isolation to avoid transmission of harmful voltages or noise, and for delivering a positive or negative drive signal to the gate/emitter of an external transistor under drive. The invention is characterized by its high voltage and noise isolation, using few components and being small in size.

Abstract: A power-on control circuit which functions to inhibit and prevent turn-on of an external power supply to an aircraft, unless a continuity signal is received from the aircraft indicating proper mating of the external power plug in the aircraft socket, thus preventing the hazards of an improper connection. The invention power-on control circuit incorporates a subcircuit for generating an acquisition signal to confirm continuity of connection, and a sensing and detector sub-circuit to enable turn-on of an external power source supplying power to an aircraft. The control circuit contains high ohmic isolation between logic elements and the aircraft, and is not sensitive to coupling with extraneous signals.

Abstract: A device for detecting the occurrence of a dc current fault in the dc feed bus of a solid state power inverter bridge. The device uses a standard, available dc shunt which is connected in the dc feed bus and which produces an ac component in its output as well as dc as a result of the PWM action of the inverter bridge. An isolation transformer and an absolute value detector process the shunt output signal and present the resulting dc signal to a digital comparator after being summed with a voltage trip level. The comparator will output a low signal indicating a fault current if the instantaneous dc component connected from the isolation transformer is higher than the comparator input trip level. The fault detection action of the invention sensor is virtually instantaneous and can be used to shut down the solid state switches in the bridge and protect them from possible damage.

Abstract: A three-phase ac power inverter incorporating circuits which operate to correct input power factor to near unity when connected to an ac input rectifier, while also reducing input harmonic distortion. The inverter includes a dc capacitor connected between buses, and three, four-pole inverter H-configuration bridges which output ac phases A, B and C. The cross-bar of each H-bridge is made up of an L-C filter. The inverter bridge switches, switching in an output Pulse Width Modulation mode for generating three phase sine waves, also serve to pump resonant energy between the L-C filter in each bridge and the dc capacitor. Phase A, B and C inverter bridges are pumped at the same carrier frequency, providing a continuous feed to the dc capacitor and the input rectifier. In effect, this action extends the conduction angle of the input rectifier, resulting in the input power factor being corrected to near unity. The pumping action through the L-C filters also filters and reduces the input harmonic distortion.

Abstract: A missing phase detector circuit which monitors the ac three-phase output voltages of power equipment or sources and produces an output signal in the event a missing ac phase is detected. The circuit reduces the monitored phase voltages to low values and produces an ac ripple voltage waveform where each ripple represents a phase. An analyzer circuit examines the ac ripple voltage waveform for its zero crossings and produces a pulsed dc waveform where the width of the pulses is normally small. If any of the pulses is found to be wide, indicating a missing phase, a positive high signal is output by an AND gate. This output signal may be used to initiate illumination of a "Missing Phase" indicator or it may be used for equipment control purposes. Provision is made to prevent a false output signal when there is no input power. The circuit is not sensitive to frequency, power factor or unbalanced loads.

Abstract: A frequency monitor and error detector circuit that processes an input ac signal to be monitored, comparing the input ac signal with an internally generated reference center frequency, and outputting a "Go/No-Go" signal indicating whether the monitored ac signal frequency is within a pre-selected tolerance band or is out of tolerance. The reference frequency is provided by a highly accurate crystal oscillator. An adjustable delay circuit is provided, capable of being adjusted to produce a frequency tolerance band of from +/-0.05% to 0.1% of the center frequency. The device has three output signals which may be logic high or logic low, and are used for activating illuminated indicators or as frequency signal inputs to other equipment. The device is small in size, accurate and reliable over a wide range of frequencies.