Patent ID: 8669747

Claim:
An on-time calculation circuit for a constant on-time switching regulator having a power stage circuit including at least one power switch operating according to a duty ratio D to convert an input voltage to an output voltage, wherein the on-time calculation circuit calculates a constant on-time of the power switch, the on-time calculation circuit comprising: a driver gate receiving a duty signal related to the duty ratio D of the power switch and generating a driver gate output signal, the driver gate operating between high and low levels of a first reference voltage and ground; a low pass filter receiving the driver gate output signal from the driver gate and generating a second reference voltage, a ratio between the second reference voltage and the first reference voltage being substantially the same as the duty ratio D of the power switch; and an on-time generator comparing the second reference voltage from the low pass filter with a ramp signal to determine an on-time of the power switch.