Spark plug igniter comprising a dc-dc converter

Claim 1

A spark plug igniter circuit, comprising: an ignition coil having a primary winding and a secondary winding; a spark discharge device connected to said secondary winding of said ignition coil for developing a discharge current therethrough and developing an electrical spark in response to a high voltage induced across said secondary winding; a direct-current power source connected to said primary winding of said ignition coil for affecting current flow through said primary winding; a breaker point, connected in series with said primary winding and said direct-current power source, and operative in a closed position for allowing direct current to flow through said primary winding and operative in an open position for interrupting the current flow through said primary winding to thereby induce the high voltage across said secondary winding effective for developing an electrical spark with said spark discharge device; and Dc-dc converter means connected in series with said secondary winding for increasing the discharge current flowing through the spark discharge device and for extending the duration of the discharge current developed in response to the high voltage applied by said secondary winding to said spark discharge device; wherein said DC-DC converter means comprises an auxiliary DC power source, said DC-DC converter including an input connected to said auxiliary DC power source and an output connected in series with said secondary winding and having a transformer for effecting a change between the input and the output voltage of the DC-DC converter, a feedback winding coupled with the transformer of said DC-DC converter for developing a voltage in response to current flowing through said transformer, rectifying means for rectifying the voltage induced in said feedback winding, a reactor connected in series between said feedback winding and said rectifying means, and means for connecting the output of said rectifying means in series with said auxiliary DC power source and with the same polarity to thereby vary the input voltage to said DC-DC converter according to the current flowing through said transformer of said DC-DC converter.