Federal Signal Corporation

Bruce E Heeb

Paul D Graham

Frederick W Eggers

A flash strobe power supply adapted for controlling alternately the energization of a pair of flash lamps includes a trigger timing device for generating a series of positive pulses and a series of negative pulses spaced in time from the positive pulses by a predetermined interval. First and second energy storage devices are provided for repeatedly charging incrementally during successive charging cycles and for storing a charge to be applied to respective first and second flash lamps. An inverter oscillator circuit includes a pulse width modulator and a transformer for generating a quasi-squarewave signal whose frequency is greater than the frequency of the positive and negative pulses to control the incremental charging of the energy storage devices. First and second switching devices deliver when conductive the charge stored in the first and second energy storage devices to their respective first and second flash lamps. A first switching means is responsive to the positive pulses of the timing device for rendering it conductive to permit the discharging of the charge stored in the first energy storage device through the first flash lamp. The second switching device is responsive to the negative pulses of the timing device for rendering it conductive to permit the discharging of the charge stored in the second energy storage device through the second flash lamp. Antisaturation circuit responsive to the quasi-squarewave signal prevents saturation of the primary winding of the transformer by disabling of the pulse width modulator which avoids further incremental charging of the first and second storage devices.

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Frankfort, IL, United States of America

Bruce E Heeb