Renesas Electronics Introduces LED Driver IC for LED Backlit LCD Televisions

Renesas Electronics announced the availability of its new LED driver IC, the R2A50106FT, for LED backlights in LCD TVs with 20 percent reduced power consumption.

The new R2A50106FT device is a driver IC that powers the white LEDs used in the backlight systems. The driver IC makes use of voltage step-up circuit technology, refined over many years for the company’s power supply IC products, in an exclusive dc-dc converter control circuit that is incorporated into the driver IC and provides backlight systems with improved power efficiency. Eight constant-current driver channels capable of driving high-luminosity LEDs are integrated in a single device, reducing the need for external components and making it easier to design a high-luminosity LED backlight system.

Compared with TVs employing conventional cold cathode fluorescent lamp (CCFL) backlights, LCD TVs equipped with LED backlights (1) have lower power consumption, (2) enable thinner enclosure dimensions, and (3) are more eco-friendly (mercury-free), leading to their rapid adoption in recent years. Nevertheless, there is still demand for further reductions in power consumption due to environmental considerations.

Against this background, Renesas Electronics developed an LED driver IC that allows adjustment of the voltage to the level required by the LED, thereby boosting the power efficiency of the backlight system. To address demands for stable backlight system operation, the R2A50106FT device incorporates protection functions to deal with conditions such as a short circuit in an LED row.

While an LED driver boosts the input voltage to drive the LEDs, Renesas Electronics’ R2A50106FT LED driver IC incorporates a newly developed step-up control circuit to control the dc-dc converter and ensures that the optimal voltage is supplied according to factors such as the LED voltage (forward voltage) and the output volume (number of elements connected in series). This yields a reduction in power consumption of about 20 percent compared with a conventional fixed-voltage system.

The on-chip protection functions include the ability to detect open or shorted LEDs row by row, and when a fault occurs, to stop operation of the affected row only. Additional functions, such as thermal shut down, step-up circuit (dc-dc converter) output overvoltage detection, and overload detection, stop driver IC operation when a malfunction occurs to protect the system as a whole.

The constant-current driver block incorporates eight NMOS (negative channel metal-oxide semiconductor) transistors with high-voltage tolerance and low on resistance (resistance during operation), so a single R2A50106FT device can produce an LED drive current up to 160mA without the need for external power MOSFETs. This reduces the number of components required to build a high-luminosity LED backlight system and simplifies the design process.

In addition to the above, two brightness adjustment functions are provided to enable fine-grained light-level adjustment: PWM brightness adjustment (12-bit PWM duty control enabling 4,096 gradations) and analog brightness adjustment (8-bit constant-current value setting with 256 gradations).

Samples of Renesas Electronics’ new R2A50106FT LED driver IC are available now, priced at US$2.00 per unit. Mass production has started and is scheduled to reach a scale of 2,000,000 units per month by May 2012.