Multiple spark ignition system for an internal combustion engine

Claim 1

Multiple spark ignition system for an internal combustion engine system for combination with a battery (BAT) supplying electrical energy to the ignition system said system comprising an ignition power supply branch connected to the battery (BAT) including an ignition coil (18); at least one spark gap (19) connected to the secondary of the ignition coil; a controlled switch (17) connected to the primary of the ignition coil (18) and controlling current flow from the battery thereto, means (10, 11, 12) providing a control pulse (B) to determine initiation of an ignition event; a frequency generator (14, 140) controlled by the control pulse and providing an output pulse train to the controlled switch (17) for multiple closing operation of the switch as a function of the width of the pulses of the pulse train, and to cause multiple ignition pulses to be applied to the spark gap, said frequency generator (14, 140) being a pulse width controllable frequency generator providing output signals of varying pulse width and having a control input terminal (14', 140) controlling the width of the output pulses provided by said frequency generator; and a spark energy control branch connected to the battery (BAT) including means deriving a signal representative of battery voltage, said sensed battery voltage signal being connected to the control input terminal (14' 140') of the frequency generator (14, 140) to control the width of the output pulses thereof in a sense to increase the width of the output pulses therefrom upon drop of battery voltage so that the energy supplied to the coil (18) by the battery, upon closing of said controlled switch (17) during occurrence of any one of said pulses, and to cause a single ignition pulse, will be essentially unaffected by drop of battery voltage.