Integrated design of efficient & reliable motor drive and PFC using low cost microcontroller with embedded PGAs and CLA

Abstract

Heating ventilation and air conditioning (HVAC) drives commonly utilize variable speed control to maximize efficiency and increasingly power factor correction (PFC) stage in the rectifier design to comply with regulations, such as IEC 61000-3-2, which limit the input current harmonics. Cycle by cycle control is desired for both the PFC stage and motor inverter. Closed loop control of these stages consumes the entire bandwidth available on a typical microcontroller leaving no bandwidth to implement fault diagnostics, housekeeping and host functions. This paper presents design of motor control and PFC using a single low cost microcontroller (MCU- TI TMS320F2805x) with embedded analog subsystem consisting of programmable gate arrays (PGA) to sense the shunt inverter currents, windowed comparators and DACs for programmable protection levels; and small footprint control law accelerator (CLA) to double the bandwidth. The integrated design reduces the number of components, reducing board size and build cost and enables on the fly changes which brings enhanced control possibilities for a cost sensitive market without compromising on cost.