Drive Circuit for a Transformer
This invention relates to a drive circuit and the method for driving a transformer. More particularly the invention relates to a drive circuit and method for driving a transformer which forms part of an ignition system for an internal combustion engine.
In order to improve emissions in petrol internal combustion engines, the engine needs to be operated with a high exhaust gas recycling (EGR) or with lean air-fuel mixtures. However, when using current spark ignition systems, the combustion stability becomes unacceptable under these conditions. The reason for this is the small volume of gas that is ignited across the small (typically 0.8 mm) spark gap. Several corona ignition systems have been developed and it has been shown that these corona ignition systems have a much better performance, due to a larger volume of gas that is ignited. However, the complexity and cost of the drive circuit used in current corona systems is a barrier for this technology to enter the market. The drive circuit has to drive a corona resonator at high frequency (larger than 1 MHz) and high power (larger than 1 kW) at the correct resonance frequency and be able to cope with arcing. The circuit must also be able to perform reliably in harsh under-hood environment, must be cost effective and not occupy much more volume than the known systems.
Accordingly, it is an object of the present invention to provide a drive circuit and method with which the aforementioned disadvantages may at least be alleviated or which may provide a useful alternative for the known circuits and methods.