Method and apparatus to control an ignition system

A method of controlling a multi-charge ignition system, said system including a spark plug control unit adapted to control at least two coil stages so as to successively energise and de-energise said coil stage(s) to provide a current to a spark plug, said two stages comprising a first transformer (T1) including a first primary winding (L1) inductively coupled to a first secondary winding (L2);

• a second transformer (T2) including a second primary winding (L3) inductively coupled to a second secondary winding (L4);
• a first switch Q1 electrically connected between the low side of the first primary winding L1 and low side/earth, a second switch Q2 connected to the low side of the second primary winding L3;
• and including a first diode D1 located between the low side of said first secondary winding L2 and ground;
• and a second diode D2 connected to a point between the low side of said second secondary winding L4 and ground and, said method comprising:
• a) measuring the voltage at a first connection point (203a) between the first switch and the low side of L1 and/or the voltage at a second connection point (203b) between the second switch and the low side of L3, wherein step a) is implemented during CMC mode only after a pre-set blank time after toggling of the transformer occurs;
• and
• b) controlling the operation of the system dependent upon said measured voltages.

A method of controlling a multi-charge ignition system, said system including a spark plug control unit adapted to control at least two coil stages so as to successively energise and de-energise said coil stage(s) to provide a current to a spark plug, said two stages comprising a first transformer (T1) including a first primary winding (L1) inductively coupled to a first secondary winding (L2);

• a second transformer (T2) including a second primary winding (L3) inductively coupled to a second secondary winding (L4);
• a first switch Q1 electrically connected between the low side of the first primary winding L1 and low side/earth, a second switch Q2 connected to the low side of the second primary winding L3;
• and including a first diode D1 located between the low side of said first secondary winding L2 and ground;
• and a second diode D2 connected to a point between the low side of said second secondary winding L4 and ground, where said threshold value(s) are in the region of Udthmax/ue), where ue is ue winding ratio between secondary and primary windings of the corresponding transformer to which the corresponding diode is directly connected to, and Udthmax=high voltage diode switching threshold of that diode;
• and, said method comprising:
• a) measuring the voltage at a first connection point (203a) between the first switch and the low side of L1 and/or the voltage at a second connection point (203b) between the second switch and the low side of L3;
• and
• b) controlling the operation of the system dependent upon said measured voltages.