Trends in lighting demand intelligence in LED driver technology in order to achieve system longevity, improve user experience and comply with regulations for LED lighting.
To realise the required features such as dedicated networked lighting communication protocols, intelligent sensor incorporation and automatic high resolution dimming, as well as high switching frequency and low power consumption, Renesas Electronics has developed microcontroller solutions for the LED driver market, also allowing system flexibility and programmability.
Constant-current drive is a critical part of an LED driver design, since a poorly developed driver can significantly affect the lifetime and colour shifting of LED components. Systems that cannot provide a sufficient amount of current will not produce the maximum lighting output; in the same way, driving LEDs with too much current will significantly reduce their duration of service.
To use LEDs efficiently, the power source must be able to provide constant current to best match the LED characteristics, where the guidance for optimum currents is provided by LED manufacturers.
The 78K0/Ix2 8-bit MCU family from Renesas consists of 14 devices with a unique internal architecture and low cost. This application specific microcontroller can drive a number of high-power LED channels allowing colour mixing and flashing sequences as well as controlling power factor correction at the same time, while still processing DALI or DMX512 lighting communications and sensor reading.
In addition to supporting a wide input voltage range and providing guaranteed operation at high temperatures of up to 105°C, this single-chip solution allows eliminating a number of external components, thus saving system cost as well as reducing CPU load by only using its intelligent hardware architecture and integrated peripheral set.
Using the 78K0/Ix2 lighting ASSP to drive HB-LEDs directly provides a low-cost LED driver solution. To demonstrate this low-cost approach, as well as DALI and DMX512 communications, Renesas has released the 78K0IX2-LED and a master lighting communication demonstration kit.
The 78K0Ix2-LED kit includes a 78K0/Ix2 based demonstration board and the application code generator Applilet EZ. This GUI software tool is used to graphically make all the configurations for the board, automatically generate pre-compiled code and program the target device using a USB cable. The board supports three types of lighting control interfaces including DALI, DMX512 and analog dimming, as well as many other features.
To further support the rapidly growing LED lighting market, Renesas has also introduced a highly integrated solution for efficiently driving high-power LEDs.
The uPD78F802x family of microcontrollers features a 4-channel LED driver on chip. Each channel has a built-in current sense circuit and is capable of driving up to 1,5 A, which covers the majority of high-power LEDs in the market.
Additionally, each channel is capable of delivering up to 1 MHz switching frequency using an additional internal oscillator, allowing the use of small external inductors for each LED channel, thus saving PCB space and system cost.
To dynamically adjust the light output to save energy or provide mood lighting, the four ADC channels of the microcontroller, as well as the available on-chip lighting communications and other serial interfaces, can be employed to interface ambient lighting sensors and provide automatic dimming for each channel independently. The device is well suited to lighting applications requiring a high level of colour mixing and flashing sequences.
Both buck and boost modes are supported, together with a temperature sensor and a number of different protection circuits, all in a single package. To support the microcontrollers, Renesas has also released the Shine It! demonstration kit. The kit has been developed with the end user in mind and contains everything required to configure an LED system within minutes.
For more information contact Marinus Rudman, Hi-Q Electronics, +27 (0)21 595 1307, [email protected], www.hi-q.co.za
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