Patent ID: 7256570

Claim:
In a circuit comprising an inductor having first and second terminals, a first switch connected between the first inductor terminal and an input terminal, a second switch connected between the first inductor terminal and a common connection, a third switch connected between the second inductor terminal and the common connection, a fourth switch connected between the second inductor terminal and an output terminal, and a sensing element for sensing inductor current, the sensing element connected between the common connection and a node joining the second switch and the third switch, a method for regulating the voltage at the output terminal at a level less than the voltage at the input terminal, the method comprising the steps of: setting the second and third switches to an off state and the fourth switch to an on state; generating a clock signal, at each clock, setting the first switch to an off state and maintaining the second switch off for a fixed time period; sensing inductor current during the fixed time period; in response to the sensed inductor current exceeding a first predetermined threshold level, turning on the second switch after the fixed time period; turning off the second switch when current falls below a second predetermined threshold level; and maintaining the first switch off until occurrence of an output voltage condition.