June 2006

Rev 1

1/19

AN2267

Application note

Implementation of current regulator for BLDC

motor control with ST7FMC

Introduction

A conventional method of controlling BLDC motors is to implement an inner current loop for

torque / current control. Reference to this inner loop is provided either by an outer speed

loop or by some other means based on application requirement. The linearity of inner

current / torque loop is greatly affected by the faithfulness of current feedback. In the first

section, an outline to various approaches for obtaining current feedback is presented and

analyzed with the limitations of each. In the subsequent sections, a presentation is given of

a simple, linear and cost effective approach of implementing the inner current loop by

sampling the DC link current at the mid-point of PWM “on time” with ST7FMC. Experimental

results are also discussed.

An accompanying software file is available with this application note and can be downloaded

www.st.com