A method of controlling an ignition system, said ignition system including: a spark plug control unit adapted to control a first coil stage and a second coil stage, said first coil stage and second coil stage adapted to successively energise and de-energise to provide a current to a spark plug, each of said first coil stage and second coil stage including a primary winding (L1, L3) inductively coupled to a secondary winding (L2, L4); a first switch connected to the primary winding of the first coil stage and the spark plug control unit; a second switch connected to the primary winding of the second coil stage and the spark plug control unit; a first resistor connected between the first switch and ground, the first resistor to measure a primary current (Ip); a first diode between the low-side end of the secondary winding of the first coil stage and one end of a second resistor, wherein the further one end of the second resistor is connected to the ground; a second diode between the low-side end of the secondary winding of the second coil stage and the one end of the second resistor; a step-down converter stage located between said spark plug control unit and the first coil stage, said step-down converter including a further switch (Ml) connected to a battery and a diode which is connected between the high-side ends of the primary windings (L1, L3) and the ground, said control unit being enabled to switch on/off said further switch (Ml), the first switch, and the second switch, characterised in that the method comprises: measuring a first voltage at the low-side end of the secondary winding of the first coil stage, a second voltage at the low-side end of the secondary winding of the second coil stage and the battery voltage, and based on the measured first and second voltages and the battery voltage, controlling a duty cycle m of a PWM-signal of the step-down converter to control current and voltage parameters of the primary windings and the secondary windings of the first coil stage and the second coil stage, wherein the duty cycle m is defined as m=Ton/(Ton-Toff), whereas Ton is the on-time of said further switch (Ml) and Toff is the off-time of said further switch (Ml), Ton+Toff=const. a spark plug control unit adapted to control a first coil stage and a second coil stage, said first coil stage and second coil stage adapted to successively energise and de-energise to provide a current to a spark plug, each of said first coil stage and second coil stage including a primary winding (L1, L3) inductively coupled to a secondary winding (L2, L4); a first switch connected to the primary winding of the first coil stage and the spark plug control unit; a second switch connected to the primary winding of the second coil stage and the spark plug control unit; a first resistor connected between the first switch and ground, the first resistor to measure a primary current (Ip); a first diode between the low-side end of the secondary winding of the first coil stage and one end of a second resistor, wherein the further one end of the second resistor is connected to the ground; a second diode between the low-side end of the secondary winding of the second coil stage and the one end of the second resistor; a step-down converter stage located between said spark plug control unit and the first coil stage, said step-down converter including a further switch (Ml) connected to a battery and a diode which is connected between the high-side ends of the primary windings (L1, L3) and the ground, said control unit being enabled to switch on/off said further switch (Ml), the first switch, and the second switch, characterised in that the method comprises: measuring a first voltage at the low-side end of the secondary winding of the first coil stage, a second voltage at the low-side end of the secondary winding of the second coil stage and the battery voltage, and based on the measured first and second voltages and the battery voltage, controlling a duty cycle m of a PWM-signal of the step-down converter to control current and voltage parameters of the primary windings and the secondary windings of the first coil stage and the second coil stage, wherein the duty cycle m is defined as m=Ton/(Ton-Toff), whereas Ton is the on-time of said further switch (Ml) and Toff is the off-time of said further switch (Ml), Ton+Toff=const. measuring a first voltage at the low-side end of the secondary winding of the first coil stage, a second voltage at the low-side end of the secondary winding of the second coil stage and the battery voltage, and based on the measured first and second voltages and the battery voltage, controlling a duty cycle m of a PWM-signal of the step-down converter to control current and voltage parameters of the primary windings and the secondary windings of the first coil stage and the second coil stage, wherein the duty cycle m is defined as m=Ton/(Ton-Toff), whereas Ton is the on-time of said further switch (Ml) and Toff is the off-time of said further switch (Ml), Ton+Toff=const.