Design of a High Efficiency DC–DC Buck Converter With Two-Step Digital PWM and Low Power Self-Tracking Zero Current Detector for IoT Applications

In this paper, a high efficiency dc–dc buck converter with two-step digital pulse width modulation (DPWM) and low power self-tracking zero current detector (ST-ZCD) is proposed for Internet of Things (IoT) and ultralow power applications. The hybrid DPWM core with high linearity and low power consumption is proposed to implement the high efficiency DPWM dc–dc converter. It is composed of a two-step delay control using the counter and delay line. An adaptive window analog to digital converter is proposed to reduce the output voltage ripple within 20 mV. A dead time generator is implemented with the proposed ST-ZCD to minimize the reverse current. The ST-ZCD can improve efficiency by reducing the control loss that accounts for a large proportion of the dc–dc converter. Also, all digital type-III compensator is implemented for the low power and small die area. This chip is fabricated with a 55 nm CMOS process, which uses the standard supply voltage of 1.5–3 V to generate the output voltage of 1.2 V. The total active area is 500 μm × 300 μm. The measured peak efficiency of the DPWM dc–dc buck converter is 91.5% with a quiescent current consuming only 130 μA.