Accurate and Lossless Current-Sensing Techniques for Power Applications -- A Practical Myth?

Power Management DesignLine (03/16/2005 2:58 PM EST) The power supply is the backbone of any electronic device, and its performance is especially critical in the growing mobile consumer market, where not only accuracy but also power efficiency is crucial, which explains why switching supply circuits have enjoyed such popularity. For the safety, performance, and feedback control of these switching supplies, it is often necessary for the circuit to better understand its loading environment, especially load current. Protecting the supply circuits, for instance, against overloading and short-circuit conditions requires the system to self-monitor its current delivery. Additionally, in current-mode DC-DC converters, the inductor current is regulated and must therefore be sensed and processed. Monitoring current is perhaps even more critical in smart power supply circuits for portable applications, where several load-dependent regions of operation exist for the sole purpose of increasing power efficiency and therefore extending battery life, which is why lossless current-sensing techniques are so important.