Average inductor current sensor for digitally-controlled switched-mode power supplies

Current-mode control in digitally-controlled switched-mode power supplies typically requires analog-to-digital (A/D) conversion of at least two signals, voltage and current. The complexity of voltage A/D converters can be reduced using window A/D techniques. In conventional current A/D conversion, however, relatively high resolution is required over a wide range of signals, which results in increased complexity, power consumption and cost of the controller. This paper proposes a very simple feedback sensor capable of high-resolution average inductor current sensing using two analog comparators and an analog low-pass filter. The approach requires very few external components and employs minimal digital hardware resources. A dynamic model and performance of the average inductor current sensor are experimentally verified on a 12 V input, 19 V output, 50 W boost converter prototype.