Sundstrand Corporation

P R Chetty

Pierre S Thollot

John J Dhyanchand

Gary L Galloway

Donald G Fair

A soft-start circuit for an inverter having a switch which is operated in accordance with the output of an oscillator includes a ramp generator coupled to the oscillator for generating a cycle ramp signal synchronized to and having the same period as the oscillator output, the cycle ramp signal also having an amplitude which periodically increases between first and second levels. Means are included for generating a soft-start signal having an amplitude which increases between the first and second levels, the length of time required for the amplitude of the soft-start signal to increase from the first level to the second level being substantially longer than the period of the cycle ramp signal. Means are coupled to the ramp generator and to the soft-start signal generating means for comparing the two signals to develop a pulse width modulated enable signal having a series of pulses of gradually increasing pulse width. Means are coupled to the comparing means and to the oscillator for gating the oscillator output with the pulse width modulated enable signal to derive switch control signals for the switch in the inverter. The switch is thereby operated at gradually increasing duty cycles immediately following turn on of the inverter.

Soft-start circuit for a power converter

A system for transferring maximum power from a solar cell array by loading the array in a manner which forces it to operate at its maximum power point. The system samples the open circuit voltage of the solar cell array to provide a signal proportional to the voltage of the array at its maximum power point. The sampled open circuit voltage is compared to the operating voltage of the solar cell array to provide an error signal which is proportional to the difference between the maximum power point voltage and the operating voltage of the array. The amount of power transferred from the array to a load is altered in accordance with the error signal to operate the array at its maximum power point.

Maximum power transfer system for a solar cell array

A push-pull converter has transistor power switches which conduct alternately to connect a DC source with the primary windings of an output transformer. A turn-off snubber circuit is connected with each power switch. When a power switch is turned on, snubber current pulses flow in the circuits connected with both switches. A switch current sensor circuit has a current transformer with an output winding inductively coupled with each of the conductors connected between the power switches and the primary windings of the output transformer. The snubber current pulses through the conductors are 180.degree. out of phase and are suppressed in the current transformer output. The switch current signal from the secondary of the current transformer is free of snubber current pulses and is used in a flux balance circuit and in a pulse-by-pulse current limiter.

Switch current sensing with snubber current suppression in a push-pull

A direct current to alternating current inverter with an output transformer is regulated by a pulse width modulator which alternately closes one of two switches connected with the center tapped primary winding of the output transformer. A synchronizing circuit for the pulse width modulator has means for gating synchronizing pulses to the clock of the modulator, blocking synchronizing signals which would cause an unbalance in the duty cycles of the switches and saturation of the output transformer.

Growing community of inventors

Rockford, IL, United States of America

P R Chetty