Switched mode power supply with improved light load efficiency

A control circuit operable to control switching elements in a switched mode power supply, comprising:

• a switching control signal generator operable to generate control signals for switching the switching elements such that the switched mode power supply converts an input voltage to an output voltage;
• and an operation mode setting module operable to receive a signal indicative of a current flowing to a load that is connected to an output of the switched mode power supply, and operable to cause the switching control signal generator to generate the control signals so as to operate the switched mode power supply in a continuous conduction mode or a pulse skipping mode in dependence upon the current, wherein in the pulse skipping mode the switching elements are turned OFF for at least one switching period of the switched mode power supply but the switched mode power supply continues to supply power to the load;
• wherein the operation mode setting module is operable to monitor the signal indicative of the current to determine whether the current exceeds a threshold, and is operable to control the switching control signal generator to generate the control signals such that, when the current exceeds the threshold, the switched mode power supply operates in the continuous conduction mode and, upon determining that the current has fallen to or below the threshold, operation of the switched mode power supply is changed from the continuous conduction mode to the pulse skipping mode so that the pulse skipping mode is entered from the continuous conduction mode;
• and wherein the operation mode setting module is further operable to:
• receive a second signal, which is indicative of the output voltage of the switched mode power supply;
• process the second signal to determine whether the output voltage is within a first predetermined range;
• upon determining both that the current has fallen to or below the threshold and that the output voltage is within the first predetermined range, control the switching control signal generator to generate the control signals such that operation of the switched mode power supply is changed from the continuous conduction mode to the pulse skipping mode;
• and upon determining that the current has dropped to or below the threshold but that the output voltage is outside the first predetermined range, control the switching control signal generator to maintain operation of the switched mode power supply in the continuous conduction mode.