Low power integrated on-chip current to digital converter

Abstract

Integrated and efficient maximum power point tracking (MPPT) is a critical need in the photo-voltaic power generation system. One of the key components of the MPPT is current and power sensor. This paper presents a low-power integrated current sensor implemented in standard low-voltage CMOS technology. The proposed current sensor is a current-to-digital converter circuit, removing the need for an additional analog-to-digital converter for current digitization. The proposed PV MPPT circuit measures the current information from the DC-DC converter output ripple by charging and discharging a set of capacitive nodes, resulting in a digital current measurement for the MPPT circuit. The MPPT circuit along with the integrated circuit is presented. The current sensor is fabricated in a 0.7 micron CMOS technology and covers less than 4 mm2 of silicon area. The sensor power consumption is less than 27 mW, and provides an 8-bits digital representation of the converter load current with less than 0.4% error.