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ROHM’s flicker-free LED driver for in-vehicle LCDs supports 10-inch and larger screens

ROHM is a news release announcing the new driver IC “BD82A26MUF-M” ( Fig. 1 ) that  drives LED backlights for in-vehicle liquid crystal displays (LCDs) . It is a 6-channel product and can be used with a large in-vehicle LCD of 10 inches or more. Positioned as an enhanced version of the BD81A76EFV-M (hereafter, the existing product) * , an LED driver for in-vehicle LCDs with a 6-channel configuration announced by the company in August 2019, it has increased output and increased the number of dimming methods that can be handled. . 

According to the company, in-vehicle displays are becoming larger due to the sophistication of ADAS (advanced driver assistance systems) and infotainment systems. In line with this trend, ROHM has introduced a new product that drives LED backlights for large LCDs, such as 10 inches or more, for automobiles. The new product has a higher output than the existing product. For example, the maximum output current per channel has increased from 120mA to 150mA. This will increase the brightness of the driven LED. Also, the maximum output voltage has increased from 40V to 50V. This increases the number of LEDs that can be driven.

 In addition, the number of dimming methods that can be used with new products has increased. In addition to PWM (Pulse Width Modulation) dimming that can be handled by existing products, the new product is capable of DC dimming. PWM dimming is a common technique in LED backlights, turning the LEDs on and off very quickly. Depending on the length of the lighting time (pulse width) of the LED, the brightness of the LED is changed. Color changes are unlikely to occur, but flickering may occur when brightness is changed. On the other hand, in DC dimming, the amount of current flowing through the LED changes the brightness of the LED. Unlike PWM dimming, LEDs do not blink, so the risk of flickering is low. On the other hand, at low current values, chromaticity transitions occur in the LED itself, so care must be taken in specifications where color is a concern.

 The dimming ratio of the new product’s PWM dimming is 1:20,000, and the company’s original “seamless PWM” technology, which was first used in existing products, was adopted ( Fig. 2 ). With this technology, switching of the current feedback mode from low brightness to high brightness, which causes flickering in general PWM dimming, does not occur. Therefore, the risk of flickering is low and application reliability is improved. The operating temperature range of the new product is -40 to +125°C. The package is 5.0mm x 5.0mm x 1.0mm VQFN32FBV05. Conforms to the quality standard “AEC-Q100 Grade 1” for in-vehicle semiconductor ICs.

Fig. 2 Seamless PWM (bottom) is less likely to flicker than general PWM dimming (top)
Fig. 2 Seamless PWM (bottom) is less likely to flicker than general PWM dimming (top)
(Image: ROHM)
[Click image to enlarge]

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