Abstract: This invention discloses a system for initiating and enhancing combustion of fuel and fuel-air mixtures by discharging electrical energy in a spark gap. The energy to breakdown the spark gap is supplied by a high voltage direct current source which supplies a voltage high enough to cause initiation of the spark without the need for an intermediate transformer. Control of the high voltage is by way of a semiconductor switch, which is preferably a bulk photoconductive switch. Such a switch is capable of withstanding the high voltage applied across it when it is switched off. There may also be provided a further source of high voltage which supplies energy to the spark gap at a lower voltage then the first source after the spark has been initiated. Thus the length of time the spark lasts for may be controlled. This is particularly useful for use with lean fuel mixtures for fuel economy or with diluted fuel mixtures diluted through exhaust gas recirculation for reduced emissions.

Abstract: This invention provides an ignition system for a spark initiated internal combustion engine such as an Otto cycle engine. High voltage pulses are generated, for instance by way of an ignition coil, and these are passed to the respective spark gaps by way of semiconductor switches. These semiconductor switches are preferably bulk photoconductive switch devices which each comprise a light source and a photosensitive switch. These devices are under the control of control circuitry which activates and deactivates the light sources approximately to distribute the high voltage pulses to the spark plugs. These switches may be used to improve the rise time of the potential across the spark gap or to generate a plurality of sparks in one gap from a single pulse.