DC bus, ADC offset compensation for IRMCF/K300 motor control IC

The IRMCF/K300 series motor controllers utilize an internal ADC for numerous important system parameters. This ADC, like all others, experiences offset in its measurements. These offsets can be amplified in measurement situations such as the DC Bus Voltage. With a small input range of 0-1.2V being potentially amplified into the 300-400V range, a small 10mV offset could result in DC Bus measurement errors of 10V. Having such an offset may not only affect ADC performance, but rotor angle estimation, PFC and field-weakening capability as well. These effects can be minimized through the use of an external reference for offset compensation.

This application note describes how to properly and safely use the IRMCF/K300 series to measure and regulate the DC Bus voltage. Two compensation methods are outlined to improve measurement accuracy involving the ADC. By following these methods the ADC will allow DC Bus measurements to be accurate within a few volts, rather than tens of volts. These same techniques can also be applied to non-DC Bus voltage measurements for more accurate results across all of the ADC inputs.

Please view the PDF document for more information.