An On-Time Generator with Zero Quiescent Power Consumption Suitable for AOT Buck Converters

A zero-quiescent-power-consumption on-time generator is proposed in this paper, which is suitable for adaptive on-time (AOT) controlled Buck converters aiming at constant switching frequency. Instead of adopting operational amplifiers for voltage-to-current conversion in conventional methods, an adaptive compensation mechanism is presented to realize a current linearly proportional to regulated output voltage, Vo, with no operational amplifier, which is used to obtain a voltage proportional to output voltage. Besides, a resistor-capacitor filter is utilized to achieve a ramp signal with slope proportional to supply voltage, VIN. By this method, an on time, TON, proportional to Vo/VIN is realized, which is the core control law of AOT Buck converters. The proposed circuit is validated in a 0.18μm BCD technology, which demonstrates the accuracy of the TON is higher than 86% with temperatures and process variations. In the case of VIN=5V and Vo=1.2V, the average dynamic current of the proposed on-time generator is only 1.465μA in one switching period Tsw, while consuming zero quiescent power.