Highly Efficient Tri-Mode Control of Buck Converters with Load Sensing Technique

A highly efficient tri-mode buck converter with a novel load sensor circuit is proposed in this paper. The combination of pulse-width modulation (PWM), pulse-frequency modulation (PFM) and pulse-skipping circuit makes it efficient to operate in wide loading region. By using the novel load sensor, the buck converter can achieve high efficiency for the load range from 3 mA to 400 mA. This load sensor can automatically switch the modes according to the different load conditions. It changes the modulation methods from PWM mode to pulse-skipping modulation mode or to PFM mode. This tri-mode buck converter is fabricated by TSMC 0.35 mum. The efficiency above 90% is achieved for the load range about 90-400 mA in PWM operation, and above 78% attained for the load range about 3-50 mA in PFM mode. The insertion of the pulse skipping mode operation extends the high efficiency 90% of PWM operation for the load range from 90 mA down to 50 mA