Brushless DC appliance motor control package delivers safety and efficiency

September 25, 2014 // By Graham Prophet
Renesas has released the RL78/G1G group of microcontrollers optimised to cut system costs by a claimed 40%. With this group of MCUs Renesas says it has a complement to its current brushless DC motor control (BLDC) MCU offerings that delivers power-efficient performance with shorter development times, in a small but powerful single-chip solution for appliances such as advanced electric fans, electric tools, and food processors, and many other applications that require fine motor control.

Features of the RL78/G1G MCUs include;

(1) On-chip PGA with software gain setting for amplifying very small signals - the RL78/G1G Group integrates an amplifier that supports setting the amplification factor for very small signals by using software. This eliminates the need to add an external amplifier for inverter circuit fault detection during BLDC motor control.

(2) On-chip high-speed comparator with response time 1/8 that of earlier products for more accurate fault detection - the RL78/G1G Group's integrated high-speed two-channel comparator has a response time of 0.15 µsec (max.), 1/8 that of comparable earlier Renesas products. This eliminates the need for an external comparator. The PGA output signal can be selected by the comparator, making it possible to use it as an overvoltage protection device for the inverter circuit during brushless motor control. For example, in a food processor, a malfunction in the brushless DC motor control can be detected immediately so that the motor can stop safely.

(3) Backward compatibility with earlier products, allowing reuse of existing software and shorter turnaround time (TAT) - the RL78/G1G Group preserves compatibility with the motor control–related peripheral functions integrated into the earlier RL78/G14 Group and includes an on-chip timer RD optimised for brushless motor control. This allows for wide-ranging scalability in combination with the RL78/G14 Group.

Development based on a common platform supporting all product levels, from multifunction high-end to entry-level models, has become the mainstream for small electric appliances incorporating BLDC motors. By using Renesas’ existing RL78/G14 Group in their high-end products, customers can use the same software resources in products at all price points, from high-end to entry-level models. In addition, integrating the external components onto one chip and extending the built-in, low-capacity flash memory lineup enables designers to reduce system cost relative to previous devices for BLDC motor control in these small appliances and consumer products.

The MCU group comprises six product versions with package pin counts of 30,