Patent ID: 8451038

Claim:
A digital control unit for controlling a duty cycle of a switched mode power supply, the digital control unit comprising: a feedback unit operable to calculate a digital control signal for controlling a duty cycle of the switched mode power supply; a voltage feed forward compensation signal generator operable to calculate a compensation signal for adjusting the digital control signal in dependence upon an input signal of the switched mode power supply; and a transient detector operable to detect a transient on the input signal of the switched mode power supply; wherein the digital control unit is responsive to the detection of a transient by the transient detector to adjust the digital control signal for controlling the duty cycle of the switched mode power supply in accordance with the compensation signal; and the transient detector comprises: an input arranged to receive a difference signal that represents a difference between consecutive values of the input signal to the switched mode power supply; a first comparator operable to detect that a positive transient on the input signal has occurred if the difference signal is greater than a positive threshold level; a second comparator operable to determine if the difference signal is within a predetermined range of positive values and output a result that indicates if the difference signal is within the predetermined range of positive values; a first calculator operable to detect that a positive transient on the input signal has occurred if, out of a first predetermined number of consecutive results of the output of the second comparator, there is at least a second predetermined number of results indicating that the difference signal is within the predetermined range of positive values; a third comparator operable to detect that a negative transient on the input signal has occurred if the difference signal is less than a negative threshold level; a fourth comparator operable to determine if the difference signal is within a predetermined range of negative values and output a result that indicates if the difference signal is within the predetermined range of negative values; and, a second calculator operable to detect that a negative transient on the input signal has occurred if, out of a third predetermined number of consecutive results of the output of the fourth comparator, there is at least a fourth predetermined number of results indicating that the difference signal is within the predetermined range of negative values.