Renesas Electronics has developed an IC "μPD168891" that controls the lighting and extinguishing of automotive LED headlamps, and sample shipments began on August 30, 2010 (Figure 1). The sample price is 500 yen / piece. It is scheduled to be transferred to mass production on a monthly basis of 50,000 units from the beginning of 2012, and will continue to expand production after the following year. The company has been manufacturing LED control ICs for consumer devices since 2009. Considering that in order to save energy, the use of LEDs for headlamp light sources will increase in the future, and the company has launched LED control IC business for automotive applications. The LED control IC business for headlamps is scheduled to be launched globally. Renesas Electronics expects the popularity of LED headlamps in the Japanese market to be earlier than in the European and American markets, so it is estimated that Japanese manufacturers will have more contacts.
Figure 1: IC "μPD168891" that controls the LED headlights to turn on and off
The μPD168891 is designed to drive up to 12 high output power white LEDs in series with rated current (Figure 2). The output is a single channel. The driving current range of the LED is 0.35 to 1A. The power supply voltage ranges from 6 to 18V and is supplied to the LED after boosting. Renesas Electronics expects to actually connect eight high-output white LEDs in series, using more than 700mA. The switching frequency of the boost control is up to 500 kHz. Although the higher the switching frequency, the smaller the external inductor and capacitor can use the smaller product, thus reducing the circuit area, but this will interfere with the AM band, so the maximum switching frequency is reduced to a slightly lower frequency than the AM band. s level.
Figure 2: Example of a headlamp unit with an LED control IC
Built-in multiple protection features
In order to reduce the size of the LED control circuit, peripheral components are integrated. First, a pre-driver circuit for boosting the driver and two power MOSFETs that block the current path when an abnormality occurs is built in the IC. Then, various protection circuits required for LED control are integrated. Protection features include over-current protection and over-voltage protection of LEDs and power MOSFETs, short-circuit of power supply to LEDs (short circuit with battery system), ground fault (short circuit to ground) protection, overheat protection, supply voltage reduction and rising protection ( Low Vcc protection / high Vcc protection) and LED short circuit detection. When a general-purpose LED control IC is used, if the external components form these circuits, there is a problem that the area of ​​the printed circuit board of the LED control circuit increases. With this LED control IC, depending on the situation, the area of ​​the printed substrate may be reduced to about half of the original.
Jiangmen Hongli Energy Co.ltd , https://www.honglienergy.com