ROHM Develops "BD92□□ Series" of LED Driver ICs for LCD TV Panels
ROHM Co., Ltd. (Kyoto-based) has developed the "BD92□□ Series" of LED backlight driver ICs, which are enjoying a growing market for LCD TV panels. With the "BD92□□ Series" newly developed using the ROHM's unique power supply circuit technology, the company successfully combined high efficiency, high accuracy, and low noise driving features and, at the same time, provided a lineup of 14 products that covered almost all of major market needs so as to flexibly respond to changes in screen sizes and lighting systems as well as requirements for specifications that are increasingly diversified in response to the rapid expansion of the market. ROHM additionally set up a customer support organization that can flexibly respond to diversifying needs of customers. The samples of these new products have already been unveiled (at a sample price of 500 yen per unit) and mass-production is scheduled to be launched in November 2010 at an immediate monthly production scale of 5 million units. As for production, ROHM will use ROHM Hamamatsu Co., Ltd. (Shizuoka-based) for the front-end process, and ROHM Electronics Philippines, Inc. (Philippines-based) and ROHM Integrated Systems (Thailand) Co., Ltd. (Thailand-based) for the rear-end process.
Nowadays, the light sources of backlights for LCD panels are rapidly changing from the conventional mainstay "CCFL" (Cold Cathode Fluorescent Lamp) light source to LED lights because of their advantages including low power consumption, long service-life, and nonuse of hazardous substances. To use an LED light source for LCD backlights, a backlight driver IC is required. However, due to the rapid expansion of the market and changes in applications, product lineups are far from enough to cover diverse applications. ROHM has offered extensive lineups of backlight drivers for small and medium LCD panels used in cell phones and various mobile devices and LED drivers for illumination used in electronic devices, and further strengthened the lineup of backlight LED driver ICs for LCD TV panels, using its circuit technology and system know-how that it has been accumulating, while providing a wide rage of solutions in response to needs for high-efficiency driving and low power consumption. LED backlights for TV panels are currently available in two types: a direct light type that places LEDs on the substrate located under the LCD panel and an edge light type that arranges LEDs on the panel edge (frame edge). This LED driver IC series responds to these two types by covering from simple to high-functional applications supporting local dimming with an industry-leading lineup of 14 products selectable according to the number of LED channels, the number of LED steps, with or without constant current circuit, dimming systems, and differences in interfaces with timing controller. This lineup helps panel manufacturers to select LED drivers that meet design specifications and flexibly respond to sudden specification changes in the course of designing their panels.
In addition, ROHM has obtained basic patents in Japan, China, the U.S. and Europe for technology that achieves low power consumption while reducing power dissipation caused by LED drivers with the edge light type, which is greatly advantageous towards achieving low power consumption and slim panels, and is becoming the mainstay of LED backlight systems. The patented products were designed to automatically discriminate anode voltage (high-side voltage) between LED channels caused by fluctuations in LED voltage, and determine DC/DC converter output according to the highest voltage, and consequently reduce power dissipation to the limits compared to conventional systems, thus enabling voltage setting by resistance value, and providing the industry's highest characteristics in terms of efficiency and heat generation. In addition, ROHM is in the process of applying for patents on smoothing current waveforms and preventing coils from generating sounds during PWM dimming, controlling the accuracy of LED current to 1.5% in the full current control range by canceling the offset of constant current circuits, etc. Going forward, ROHM will incorporate its patented technologies, circuit technology established with small and medium LCD panels, and system know-how established with the CCFL backlight control in backlight LED drivers for LCD TV panels to develop low-power-consumption and higher value-added LED drivers.
■Major Features of "BD92□□ Series" of LED Backlight Driver ICs for LCD Panels
- High efficiency and low heat generation achieved with patented technologies
- Supporting a wide current range of 0 to 350 mA
- Available for highly accurate current setting across the full current range
- PWM dimming with low-noise coil and transformer
- Wide dimming range (0.1% to 100%)
|LED Connection Channel||1ch||2ch||3ch||4ch||6ch||8ch||16ch||24ch|
|DC/DC type||1 product||1 product|
DC/DC • Multi-channel
to 350 mA/ch)
to 350 mA/ch)
to 350 mA/ch)
|Multi-channel driver type||1 product||
■System Block Diagram
CCFL(Cold Cathode Fluorescent Lamp)
Compact fluorescent tubes having a diameter smaller than that of ordinary fluorescent lamps, which are mainly used as light sources of backlights for LCD panels.
The light sources of backlights for LCD panels are rapidly changing from CCFL to LED.