Power supply sequencing circuit for flash fuser

Claim 1

A circuit for controlling the operation of a plurality of flash lamps used to fuse toner particles to paper sheets in a xerographic printing system wherein the number of lamps energized is dependent upon the side of said paper sheets, comprising: (a) a plurality of flash lamps positioned orthogonally to the direction of flow of said paper sheets through said xerographic printing system; (b) at least one energy storage capacitor operatively and individually coupled to each of said flash lamps; (c) capacitor charging circuit means, each including electronic switch means disposed in series between said energy storage capacitors for each of said flash lamps and a source of alternating current voltage; (d) sequencing means for producing control signals for turning on said electronic switch means in said capacitor charging circuit means at predetermined discrete sequential time intervals whereby said energy storage capacitors are connected said charging circuits means in a timed sequence, said sequencing means including (i) a zero-crossing detector circuit coupled to said source of alternating current voltage for producing clocking pulses at each zero-crossing of said alternating current voltage; (ii) frequency dividing means coupled to the output of said zero-crossing detector circuit; and (iii) shift register means coupled to the output of said frequency divider means for generating said control signals in a predetermined time serial order (e) gating means coupled to receive said control signals and capacitor circuit identification signals for selectively applying said control signals to said electronic switch means only in particular identified ones of said capacitor charging circuit means; and (f) trigger means for simultaneously applying a flash lamp triggering signal simultaneously to all of said flash lamps whereby only whose flash lamps identified by said charging circuit identification signal will be flashed.