A PWM/PFM Dual-Mode DC-DC Buck Converter with Load-Dependent Efficiency-Controllable Scheme for Multi-Purpose IoT Applications

This paper presents a dual-mode DC-DC buck converter including a load-dependent, efficiency-controllable scheme to support multi-purpose IoT applications. For light-load applications, a selectable adaptive on-time pulse frequency modulation (PFM) control is proposed to achieve optimum power efficiency by selecting the optimum switching frequency according to the load current, thereby reducing unnecessary switching losses. When the inductor peak current value or converter output voltage ripple are considered in some applications, its on-time can be adjusted further. In heavy-load applications, a conventional pulse width modulation (PWM) control scheme is adopted, and its gate driver is structured to reduce dynamic current, preventing the current from shooting through the power switch. A proposed dual-mode buck converter prototype is fabricated in a 180 nm CMOS process, achieving its measured maximum efficiency of 95.7% and power density of 0.83 W/mm(2).

Automated summary

This paper presents a dual-mode DC-DC buck converter for multi-purpose IoT applications, with a load-dependent, efficiency-controllable scheme that adjusts the switching frequency based on load current for optimum power efficiency and further adjusts the on-time for different applications. In heavy-load applications, a conventional PWM control scheme is adopted with a gate driver structured to reduce dynamic current. The fabricated prototype achieves a measured maximum efficiency of 95.7% and power density of 0.83 W/mm(2) in a 180 nm CMOS process.