Method and apparatus for operating traveling spark igniter at high pressure

Abstract

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.

What is claimed is: 
     
         1 - 6 . (canceled) 
     
     
         7 . 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, wherein the discharge path includes a switching element between the plasma-sustaining capacitor and the electrodes.   
     
     
         8 . The method of  claim 7 , wherein the switching element is of a type that can be switched while current therethrough is not zero. 
     
     
         9 . The method of  claim 8 , wherein the switching of the switching element includes turning off the switching element while the current therethrough is not zero. 
     
     
         10 . The method of  claim 8 , wherein-the at least one follow-on pulse are voltage pulses generated by the capacitor pulling its discharge current through an inductance. 
     
     
         11 . The method of  claim 10 , wherein the inductance is in series with the capacitor and one of the electrodes. 
     
     
         12 . The method of  claim 7 , wherein the discharge path modulates a discharge current of the capacitor. 
     
     
         13 . The method of  claim 7 , wherein the discharge path comprises a path of discharge of energy that formed the plasma kernel. 
     
     
         14 . The method of  claim 7 , further comprising providing at least one limit of current drain off of the plasma-sustaining capacitor.