Abstract A d.c. to d.c. converter which produces from a low voltage battery supply a high voltage d.c. output. The converter comprises a step up transformer the primary (Lp) of which receives current pulses under the control of an oscillator (5). For each current pulse, the current builds up steadily and is then abruptly cut off so as to induce a high voltage pulse in a secondary (L s ) of the transformer. The high voltage pulses pass along a voltage multiplier (6) to provide the high voltage d.c. output. Each high voltage pulse has associated with it a low voltage pulse in the primary (Lp) which is used to control the rate of the oscillator (5). The oscillator (5) is also controlled as a function of the peak current in the primary (Lp) by a transistor TR3, and the oscillator is further controlled to limit its maximum rate when the output current exceeds a given level, by means of a feedback loop (R3, C4, R4, IC4, TR3).
.1. A d.c. to d.c. converter for deriving from a relatively low.voltage battery supply a relatively high voltage d.c. output, comprising a step up transformer having primary and secondary windings; oscillator means arranged to cause cyclically battery current to build up in the primary winding and then abruptly change in such a manner as to induce in the secondary winding a relatively high voltage pulse and such that there is formed in the primary winding a relatively low voltage pulse of a magnitude which is a function of the high voltage pulse in the secondary winding; output means coupled to the secondary winding and arranged to derive said high voltage d.c. output from the high voltage pulses induced in the secondary winding; and control means responsive to the low voltage pulse in primary winding and arranged to control the rate of operation of the oscillator means so as to control the magnitude of said high voltage d.c. output.
Claim 2
Dependent Claim
35 words
2 . A converter according to claim 1 including sensing means to sense the magnitude of the current flowing in the primary winding and to switch off the current when it reaches a predetermined magnitude.
Claim 3
Dependent Claim
23 words
A converter according to claim 2 wherein said sensing means is arranged to control timing of oscillatory signals produced by the oscillator means.
Claim 4
Dependent Claim
32 words
A converter according to any preceding claim including means to sense the output current and to reduce the rate of operation of the oscillator if the output current exceeds a given level.
Claim 5
Dependent Claim
22 words
A converter according to any preceding claim wherein the oscillator means comprises a pair of CMOS inverters and a time constant circuit.
Claim 6
Dependent Claim
43 words
A converter according to any preceding claim wherein the control means is arranged to sample the peak value of said low voltage pulse and to feed said sampled value to the oscillator in such a manner as to control its rate of operation.
Claim 7
Dependent Claim
38 words
A converter according to any preceding claim including a semiconductor switch connected in series with said primary winding, and wherein said oscillator means is arranged to feed a rectangular waveform to cause cyclic switching of said semiconductor switch.
Claim 8
Dependent Claim
23 words
A converter according to claim 7 including a capacitor arranged to store electrical energy from said low voltage pulse in the primary winding.
Claim 9
Dependent Claim
15 words
A converter according to any preceding claim wherein said output means includes a voltage multiplier.
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