A method for defining a pulse firing pattern for a transformer of an electrostatic precipitator comprising - first elements ("1") indicative of a half wave of an input voltage or current of a power input to be fired, - second elements ("0") indicative of a half wave of an input voltage or current of a power input not to be fired, - the pulse firing pattern defining the power that is transferred from the power input to the transformer, wherein the pulse firing pattern comprising couples of adjacent second elements ("0"), and at least two first elements ("1") characterized in that the transformer is not supplied with successive half waves of the same sign and the pulse firing pattern is defined by the following steps: a) defining a target power ratio indicative of the power ratio to be supplied to the collecting electrodes and discharge electrodes of the electrostatic precipitator; b) calculating a first power ratio indicative of the power ratio supplied to the collecting electrodes and discharge electrodes using an initial pulse firing pattern having a length to which one first element is added, c) calculating a second power ratio indicative of the power ratio supplied to the collecting electrodes and discharge electrodes using the initial pulse firing pattern having the length to which one couple of second elements is added, d) selecting the pulse firing pattern used in step b) if the first power ratio is closer to the target power ratio and selecting the pulse firing pattern used in step c) if the second power ratio is closer to the target power ratio, e) repeating steps b), c), d). - first elements ("1") indicative of a half wave of an input voltage or current of a power input to be fired, - second elements ("0") indicative of a half wave of an input voltage or current of a power input not to be fired, - the pulse firing pattern defining the power that is transferred from the power input to the transformer, wherein the pulse firing pattern comprising couples of adjacent second elements ("0"), and at least two first elements ("1") characterized in that the transformer is not supplied with successive half waves of the same sign and the pulse firing pattern is defined by the following steps: a) defining a target power ratio indicative of the power ratio to be supplied to the collecting electrodes and discharge electrodes of the electrostatic precipitator; b) calculating a first power ratio indicative of the power ratio supplied to the collecting electrodes and discharge electrodes using an initial pulse firing pattern having a length to which one first element is added, c) calculating a second power ratio indicative of the power ratio supplied to the collecting electrodes and discharge electrodes using the initial pulse firing pattern having the length to which one couple of second elements is added, d) selecting the pulse firing pattern used in step b) if the first power ratio is closer to the target power ratio and selecting the pulse firing pattern used in step c) if the second power ratio is closer to the target power ratio, e) repeating steps b), c), d). a) defining a target power ratio indicative of the power ratio to be supplied to the collecting electrodes and discharge electrodes of the electrostatic precipitator; b) calculating a first power ratio indicative of the power ratio supplied to the collecting electrodes and discharge electrodes using an initial pulse firing pattern having a length to which one first element is added, c) calculating a second power ratio indicative of the power ratio supplied to the collecting electrodes and discharge electrodes using the initial pulse firing pattern having the length to which one couple of second elements is added, d) selecting the pulse firing pattern used in step b) if the first power ratio is closer to the target power ratio and selecting the pulse firing pattern used in step c) if the second power ratio is closer to the target power ratio, e) repeating steps b), c), d).