Ballast circuit for gaseous discharge lamps

Claim 1

A gas discharge lamp starting and ballast circuit comprising, an input terminal pair for receiving a-c energy, first voltage doubler circuit means coupled to said input terminal pair for substantially doubling the peak voltage between said input terminal pair and comprising first and second unilaterally conductive devices connected in series and poled in the same sense shunted by first and second capacitors connected in series to form a bridge circuit having four junctions with the junction between said first and second unilaterally conductive devices coupled to one terminal of said input terminal pair and the junction between said first and second capacitors coupled to the other terminal of said input terminal pair, second voltage doubler circuit means for selectively substantially doubling the voltage provided by said first voltage doubler circuit means and comprising third and fourth unilaterally conducting devices separated by, connected in series with and poled in the same sense as said first and second unilaterally conducting devices and third and fourth capacitors connected in series across the series combination of said first, second, third and fourth unilaterally conducting devices with the junction of said third and fourth capacitors coupled to the junction between said first and second unilaterally conducting devices, the impedance of said first and second capacitors being much lower than the impedance of said third and fourth capacitors whereby the current flowing through said first and second capacitors when a gas discharge lamp is connected in series between the junction of said third capacitor with said third unilaterally conducting device and the junction between said fourth capacitor with said fourth unilaterally conducting device is so much greater than the current then flowing through said third and fourth capacitors that the voltage increasing effect of said third and fourth capacitors is then negligible, whereby said first voltage doubler circuit means, said second voltage doubler circuit means and said gas discharge lamp may comprise means for initially establishing both said voltage doubler circuit means operative for providing an output voltage more than twice the peak voltage between said first and second voltage doulber circuit means from said input terminal pair and thereafter rendering only said first voltage doubler circuit means operative for providing at the output of said first and second voltage doubler circuit means a voltage substantially twice that between said input terminal pair.