Doble Engineering Company

Other

Lars P Allfather

John E Levreault

Impedance of a power system adapted for operation at a predetermined line frequency is measured by providing a test signal of frequency different from the predetermined line frequency by an increment significantly less than the predetermined line frequency to provide an impedance measurement signal representative of the impedance of the power system at the test frequency. The impedance measurement signal is processed to provide a line impedance signal representative of the power system impedance at the predetermined line frequency.

Impedance measuring

A switching amplifier circuit includes a tri-state switching circuit receiving a DC voltage signal and having first electrical switches responsive to first control signals and providing a differential AC voltage waveform at a predetermined frequency alternating between a positive DC voltage, negative DC voltage and a zero voltage. The switching amplifier further includes a rectifier circuit having second electrical switches responsive to second control signals for receiving the differential AC voltage output waveform from the tri-state switching circuit and providing a desired output signal. The second control signals are applied to switch the second electrical switches only when the first electrical switches of the tri-state switching circuit are in the zero voltage state.

Reducing switching losses in a phase-modulated switch-mode amplifier

Automatic bridge balancing apparatus includes a reference impedance and a measuring terminal pair for receiving an unknown impedance. A source of a test signal is coupled to the reference impedance and the measuring terminal pair. A measuring detector is connected in series with the unknown impedance when connected to the measuring terminal pair to provide a measured signal. A reference detector is coupled to the reference impedance to provide a reference signal. A combiner combines the measured signal with the reference signal to provide an error signal. The reference detector includes an up/down counter coupled to a digital attenuator that provides the reference signal. A controller responds to the error signal to control the count in the up/down counter so that the associated digital attenuator provides a signal to the combiner that reduces the error signal so that the count in the up/down counter is characteristic of the unknown impedance.

Automatic bridge balancing using controllable impedance in

A signal is amplified with a plurality of amplifiers, each amplifier having a reference port, a reference node coupled to the reference port, and a signal port, and each amplifier being supplied by a power source with operating potential with respect to the reference node that is coupled to the reference port of that amplifier. The amplifiers are cascaded in a manner selected so that the output of a first amplifier (which receives the signal to be amplified at its input port) drives the reference node of a second amplifier, and the reference node of the first amplifier provides an input at the signal port of the second amplifier, whereby the first and second amplifiers are directly coupled together to amplify the applied signal.

Amplifying with directly coupled, cascaded amplifiers

Power conversion system includes power amplifiers that receive D.C. potentials from rectifying and filtering circuitry that direct couple the power amplifiers to the conventional A.C. power lines. An output transformer couples the power amplified signal to an output terminal. A feedback network couples the output terminal to one input of a signal combiner that has a reference input terminal for receiving a reference signal. An isolation amplifier couples the output of the signal combiner to the input of the power amplifiers. The isolation amplifier has a combining network that receives on one input a signal from the input terminal coupled through a high pass filter cascaded with a transformer coupled amplifying stage and on the other input from the input terminal through an optocoupler amplifying stage cascaded with a low pass filter. The power amplifiers comprise like class B amplifiers having substantially the same gain driving the primary of the output transformer. An attenuator imparts an attenuation to the output of the first amplifier that is the reciprocal of the amplifier gain and delivers the attenuated signal to the input of the second amplifier. Current shunts in series with a lead from the rectifiers and filters provide a signal representative of the current drawn by each of the class B amplifiers. For D.C. output, there is a precision diode and 600 Hz signal inverter that couples the output of the signal combining network with the isolation amplifier and a 600 Hz output transformer cascaded with a rectifier and filter that couples the output of the power amplifiers to the output terminal.

Power converting

Six high-current conducting receptacles are seated in a panel suitably insulated therefrom about an opening embracing an axis of a shaft protruding therethrough of a six-position detented rotary switch. Three equiangularly spaced studs support a tap select dial formed with an opening that selectively exposes one of the receptacles at a time and a central opening accommodating the shaft of a switch adapter below connected to the rotary switch shaft and maintained in fixed relationship with the rotary switch shaft and the tap select dial. The shaft of the switch adapter extending through the central opening in the tap select dial carries a knob. A connector plug may pass through the opening in the tap select dial for engagement with the exposed receptacle.

Current tap selecting switch

An electronic Class B master power amplifier is cascaded with a like slave Class B electronic power amplifier between ground and an output terminal to which the output of the slave amplifier is connected. A first pair of D.C. sources deliver potentials of magnitude V.sub.ss but opposite polarity to the master power amplifier and each have a reference terminal connected to ground. A second pair of D.C. sources deliver potentials of magnitude V.sub.ss but opposite polarity to the slave power amplifier, and each have a reference terminal connected to the outupt of the master amplifier. A common input signal to be amplified is delivered to the inputs of the master and slave amplifiers.

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Boston, MA, United States of America

Lars P Allfather