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, comprising:
 applying, to at least a pair of electrodes of an igniter, a voltage of amplitude sufficient to cause breakdown to occur between the pair of electrodes, resulting in electrical discharge current in an initiation region sufficient to form a plasma kernel adjacent the initiation region; and   passing at least most of the electrical discharge current through a switching element capable of being switched off with at least 3 Amperes (A) of current therethrough.   
     
     
         8 . The method of  claim 7 , wherein the switching element is capable of being switched off with at least 3 to 450 A of current therethrough. 
     
     
         9 . The method of  claim 8 , wherein the switching element is capable of being switched off with at least 5 A of current therethrough. 
     
     
         10 . The method of  claim 9 , wherein the switching element is capable of being switched off with at least 5-200 A of current therethrough. 
     
     
         11 . The method of  claim 10 , wherein the switching element is capable of being switched off with at least 20 A of current therethrough. 
     
     
         12 . The method of  claim 11 , wherein the switching element is capable of being switched off with at least 40 A of current therethrough. 
     
     
         13 . The method of  claim 7 , further comprising drawing the at least most of the electrical discharge current to and/or from a capacitor. 
     
     
         14 . The method of  claim 13 , further comprising switching the switching element to draw the at least most of the electrical discharge current to and/or from the capacitor, passing the at least most of the electrical discharge current through the switching element. 
     
     
         15 . The method of  claim 7 , wherein the electrical discharge current flows between the pair of electrodes and through the switching element. 
     
     
         16 . The method of  claim 15 , further comprising stepping up a voltage stored in the capacitor to obtain the voltage of amplitude sufficient to cause breakdown to occur between the pair of electrodes. 
     
     
         17 . The method of  claim 7 , further comprising switching the switching element off while current therethrough is not zero. 
     
     
         18 . A method, comprising:
 applying, to at least two electrodes of an igniter, a voltage of amplitude sufficient to cause breakdown to occur between the at least two electrodes, resulting in electrical discharge current in an initiation region sufficient to form a plasma kernel adjacent the initiation region; and   passing at least most of the electrical discharge current through a thyristor or an IGBT.   
     
     
         19 . The method of  claim 18 , comprising passing at least most of the electrical discharge current through the thyristor, wherein the thyristor is a metal-oxide-semiconductor (MOS) controlled thyristor (MCT). 
     
     
         20 . The method of  claim 18 , comprising passing at least most of the electrical discharge current through the thyristor, wherein the thyristor is an MCT. 
     
     
         21 . The method of  claim 18 , further comprising drawing the at least most of the electrical discharge current to and/or from a capacitor. 
     
     
         22 . The method of  claim 21 , further comprising switching the switching element to draw the at least most of the electrical discharge current to and/or from the capacitor, passing the at least most of the electrical discharge current through the switching element. 
     
     
         23 . The method of  claim 18 , wherein the electrical discharge current flows between the pair of electrodes and through the switching element. 
     
     
         24 . The method of  claim 23 , further comprising stepping up a voltage stored in the capacitor to obtain the voltage of amplitude sufficient to cause breakdown to occur between the pair of electrodes. 
     
     
         25 . The method of  claim 18 , further comprising switching the switching element off while current therethrough is not zero. 
     
     
         26 . A circuit, comprising:
 a capacitor configured to store a first voltage;   voltage step-up circuitry configured to step up the first voltage to a second voltage of amplitude sufficient to cause breakdown to occur between at least two electrodes of an igniter, resulting in electrical discharge current in an initiation region sufficient to form a plasma kernel adjacent the initiation region; and   a thyristor or an IGBT configured for coupling to the igniter to pass at least most of the electrical discharge current therethrough.