Control circuit, system and method for switched-mode power supply

A control system for a switched-mode power supply, the control system comprising a switching element, a freewheeling element and an energy storage element, the control system configured to convert an input voltage into an output voltage,

• the control system further comprising an on-time control unit, the on-time control unit receiving a first signal and a second signal, the first signal characterizing a current limiting value and the second signal characterizing a current flowing through the first switch to select an operating mode of the switched-mode power supply based on the first signal and the second signal,
• wherein the on-time control unit compares the current flowing through the first switch with the first reference current value generated based on the current limiting value and the switched-mode power supply is configured to be in a first operating mode when a peak value of the current flowing through the first switch does not surpass the first reference current value, and
• wherein the on-time control unit determines the turn-off instant for the first switch based on the instant of that the current flowing through the first switch increases to the first reference current value in the first operating mode, thereby maintaining that the peak current flowing through the first switch is not lower than the first reference current value.

A control method for a switched-mode power supply for driving a first switch in the switched-mode power supply to alternately turn on and off, thereby converting an input voltage into an output voltage, the control method comprising:

• detecting a current flowing through the first switch;
• when a peak value of the current flowing through the first switch does not surpass the first reference current value, configuring the switched-mode power supply to be in a first operating mode, in which the on-time control unit determines the turn-off instant for the first switch based on the instant of that the current flowing through the first switch increases to the first reference current value, thereby maintaining that the peak current flowing through the first switch is not lower than the first reference current value.