Lossless Method Boosts Current-Sense Signal

by Patrice Lethellier, It Can Be Done, Salt Lake City, Utah, How2Power Today, Jun 15 2018

Focus:
Inductive sensing (inductor DCR) is sensing an inductor current in power converters without incurring the losses of a sense resistor. However, the sensed voltage signal has a small amplitude, making it susceptible to noise which can degrade its accuracy. This article describes a modification of inductor DCR current sensing which boosts the sensed signal, while adding very little cost to the circuit. In this method, known as Combi-Sense, a totem-pole of small-signal MOSFETs is added in the driver chip and the current signal at this switch node is added to the inductor DCR current signal. In the buck converter example cited, the current signal amplitude is increased by a factor of three.

What you’ll learn:

• How to boost the inductor DCR current sense signal in buck converter and other converter designs

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