METHOD AND APPARATUS FOR OPERATING TRAVELING SPARK IGNITER AT HIGH PRESSURE
An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low “simmer” current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.
1 . A method of plasma generation, comprising:
a. applying to an igniter having at least a pair of electrodes a voltage of amplitude sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter in an initiation region, and formation of a plasma kernel adjacent said initiation region; and
b. following breakdown, applying to said electrodes at least one follow-on pulse by discharging a plasma-sustaining capacitor via a current-controlling discharge path.
2 . The method of claim 1 , wherein the discharge path comprises a switching element of a type that can be switched while current therethrough is not zero.
3 . The method of claim 2 , wherein the switching of the switching element includes turning off the switching element while the current therethrough is not zero.
4 . The method of claim 2 , wherein one or more of the follow-on pulses are voltage pulses generated by the capacitor pulling its discharge current through an inductance.
5 . The method of claim 4 , wherein the inductance is in series with the capacitor and one of the electrodes.
6 . The method of claim 1 , wherein the discharge path modulates a discharge current of the capacitor.