MCUs for motor inverter drives cut code size, speed development

April 24, 2015 // By Graham Prophet
Renesas says its 32-bit RX23T microcontrollers can improve energy efficiency with precision motor control in home appliances, industrial and office equipment; the MCUs feature on-chip floating point unit, reducing code size and development time by up to 30%

Renesas designed the RX23T Group of microcontrollers to enable highly precise control of inverter circuits employed in energy-efficient electric home appliances, industrial machinery, and office equipment. Based on the fast RX core, the 32-bit MCUs are suitable for building high-performance inverter control systems for applications such as DC motor control in energy-efficient electric home appliances such as refrigerators, air conditioners, washing machines, vacuum cleaners, and fans; entry-level to mid-range industrial equipment such as general-purpose inverters, electrical tools, and drones; and office equipment. The functions are optimised for inverter drive control, including the inclusion of an on-chip floating point unit (FPU).

These MCUs provide an optimised subset of the functions of the RX62T Group, which has a track record in the inverter control field, designed specifically for use in three-phase inverter drive applications.

Precise inverter control and reduced development time for mid-range and entry-level devices; inverter control requires a large number of arithmetic operations involving decimal points, and it is useful to perform these using a floating-point arithmetic unit. However, cost constraints on mid-range and affordably priced power-efficient electric home appliances and industrial equipment have prevented the use of expensive microcontrollers with on-chip FPUs. Instead, the most common approach has been to develop software for a fixed-point arithmetic unit. The new RX23T Group MCUs incorporate an on-chip FPU without increased costs, eliminating the need to implement the decimal position shifting required when using a fixed-point arithmetic unit. This simplifies the software configuration. The on-chip peripheral functions are also optimised for single inverter drive, boosting the cost-to-performance ratio and making it possible to add high-precision inverter control to mid-range and entry-level products.

High power efficiency for even lower power consumption in inverter products; the RX23T MCUs feature the RXv2 core (4.55 CoreMark/MHz (target), among the best in the industry) and DSP functionality, allowing operation processing to be maintained with no loss of real-time responsiveness when performing inverter control (sensor-less vector control), even