A Wide-Input-/Output-Voltage-Range Buck Converter With Adaptive Light-Load Efficiency Improvement and Seamless Mode Transition

A wide-input/output-voltage-range buck converter with adaptive light-load efficiency improvement and seamless mode transition for high-voltage applications is presented in this article. The proposed design uses a load prediction structure to eliminate dc current sensor and to ensure high efficiency in the 0.02 $\sim$ 2-A load range. The pulsewidth modulation (PWM) mode has been used for near-full load. Since efficiency degradation at light loads occurs at different levels regarding the input and output voltage, a novel dynamic frequency pulsewidth modulation (DFPWM) with adaptive efficiency improvement mechanism is proposed, which activates efficiency improvement based on the input and output voltage at proper load current. Moreover, pulse frequency modulation (PFM) has been used to guarantee high efficiency in a wider load range. The proposed trimode buck converter has seamless mode change. Input and output voltage ranges are 5 $\sim$ 30 V and 3 $\sim$ 15 V, respectively, which are compatible with automotive and RF applications. Output voltage disturbance is less than 60 mV at 2-A load step with a 15- $\mu$ s settling time for 30 to 3 V conversion. Moreover, output voltage disturbance in PWM/DFPWM and DFPWM/PFM mode change is zero and 60 mV, respectively. The proposed design has been implemented on 180-nm BCD technology with a 1.65 mm ×1.80 mm die size.