Ultra-Low Power Current-to-Digital Sensor for Switching DC-DC Converters

Inhalt:
Current sensing is a critical need for detecting system short circuit, thermal management, load balancing, and maximum power point tracking (MPPT) in DC-DC converters. An ultra low-power current sensing and digitization circuit based on a Current-to-Digital Conversion (IDC) technique is presented. The circuit is based digitizing the discharge period of a sampled capacitor without the need for an ADC. Relative to sensing methods based on series resistors and analog-to-digital converters to digitize the sampled current, the proposed circuit achieves higher accuracy with less complexity, and occupies a fraction of the area, and power consumption. The circuit is designed using a 100 V compliant 0.35 µm CMOS technology for a 60 V boost DC-DC converter. For load current ranging from around 0.1 to 1A, the proposed sensor total power consumption is less than 0.57 nano-W and less than 1% measurement error. Keywords - switching converters; capacitor; Current-to-Digital Conversion