Microcontrollers provide ‘ultimate’ LED lighting functionality

The RL78/I1A range of mcus adopt Renesas' RL78 CPU, which is said to achieve high computational performance and ultra low power consumption. It includes from 32 to 64KB of flash memory in 20 to 38-pin package versions. According to Renesas, the devices achieve 20% reduced power consumption during normal operation over the company's existing 78K0/Ix2 products. The RL78I1A supports lighting communication standards for centralised control in buildings and offices. The new lighting mcus provide six high resolution PWM outputs that are capable of supporting an average resolution of 0.97ns. This allows dimming and colour temperature adjustments about 25 times more precise than RL78/Ix2 products. The devices also include a new PWM output on/off control timer that allows them to support either current or PWM based dimming adjustment. A programmable gain amplifier is also included that can amplify the a/d converter input level by up to a factor of 32 to support high precision LED current measurement. This enables fine grained brightness adjustment and allows a smaller current measurement resistor to be used. The microcontrollers feature a newly included PFC control function that supports interleaved operation for high power equipment requiring improved power factors. Since the internal comparators and an interrupt pin are internally interlocked with the PWM timers, this enables efficient PFC control without cpu involvement and eliminates the need for an external PFC control IC. The devices provide an overcurrent detection function that uses comparators (including window comparators that allow both upper and lower limits to be set) for overvoltage and overcurrent detection and stops PWM timer output automatically. This function can prevent breakdowns in lighting fixtures. In addition to CSI, the devices also support the I^²C bus and UART (DMX512) standards and also the DALI (Digital Addressable Lighting Interface) open standard for lighting communication which also supports extended DALI frames. Samples of the RL78/I1A mcus are available now, while mass production is scheduled to begin in January 2012.