A portable high-voltage source for supply of corona discharge circuits

摘要

1536157 D.C.-D.C. converters COULTER SYSTEMS CORP 12 Dec 1975 [13 Dec 1974 20 Oct 1975] 51018/75 Addition to 1477202 Heading H2F In a power supply, e.g. for producing corona in portable electro-photographic apparatus, an oscillator 24 is coupled to a pulse shaping circuit 48 which includes a switching device such as transistor 54 arranged to become conductive on one half cycle from the oscillator 24 and non- conductive on the other half cycle, device 54 switching current into the primary of a transformer 68 the secondary of which is coupled to a voltage multiplying rectifier 66 arranged to produce the corona. The pulse shaping circuit 48 is arranged to draw no current from the D.C. source 12 except during the half cycles of oscillator 24 with device 54 is conductive. The corona current is monitored at 132 so that the pulse shaping circuit 48 is inhibited when the corona current reaches a predetermined magnitude. As described, the circuit is generally similar to that described in Specification 1,477,202; transformer 68 being saturated by each conductive period of transistor 54 and providing an oscillation at the end of each saturating pulse which oscillation is applied to the voltage octupler 66 so as to provide 8 kV at 104 for the corona electrode 114 positioned adjacent the electrophotographic film. The corona current is passed via potentiometer 120 and monitored by a NAND gate 132 the output of which is arranged to inhibit the oscillation from the NAND gate 38 when the corona current exceeds predetermined limits. A feedback circuit 138 ... 144 tends to increase the response time of gate 132.