Advanced LED driver solution for LED lighting applications

Sales manager of ADI company in Central China Zhang Jing said that in the world of health, environmental protection, the pressure of energy crisis greatly, the future development trend of the lighting industry will be energy-saving, health, environmental protection, green development. With the pace of urbanization, LED lighting market demand will be huge, and the acceleration of urbanization and the sustainable development of the city of LED lighting products of high efficiency and energy saving requirements higher and higher.

Zhang Jing believes that the LED driver is a challenge is no matter how much input, the output voltage, in a wide range of operating conditions how to limit the current flowing through the LED. At the same time, the current LED process caused by different batches and positive voltage, environment temperature and driving current of LED, the different ways of connection (parallel or series), will cause the change of LED brightness and color point. So in the design of LED driver power supply, the precise control of the current flowing through the LED is the key to the application of the high end design. In addition, in the case of high power output, especially for such a capacitive LED light source, the isolation of the driver and the high voltage AC-DC transform is also an important challenge. At the same time constant current drive (the brightness of the brightness of the light), brightness adjustment and PWM drive modulation technology is also the technical difficulties of today's LED driver IC. ADI can provide a variety of power control scheme to control the LED power supply. For example, through the high side current detection + temperature measurement feedback control, can accurately control the LED current.

In response to these challenges, ADI company has many corresponding solutions. Zhang Jing said, ADI for automotive and LCD backlight applications to provide light-emitting diode (LED) driver. For example, AD8240 is suitable for automotive applications to drive and monitor LED components. AD8240 reduces the system cost by reducing the complexity associated with the LED driver, which includes over current protection and the MSOP package. ADM8845 charge pump is suitable for driving up to 6 parallel white LED, while ensuring the backlight LCD brightness uniformity. It achieves excellent matching performance by monitoring the current of each LED individually. The ADM8845 can be automatically switched between the 3 charge pump operating modes according to the input voltage, so it is also used to maximize power efficiency. The ADP8866 programmable LED driver supports 9 LED current independent control with programmable LED flash sequence and low power consumption characteristics. Built in charge pump automatically adjusts its gain so as to provide high power supply for LED under all conditions. This low power consumption and simplified software interface makes it an excellent choice for a large number of portable systems that require a large number of independent LED controls, including keyboard lighting, LCD lighting and analytical lighting.

He said, ADI can provide high power density, with PFC (power factor correction) LED driver circuit ADP81XX. The power efficiency can reach more than 92%, the power input range is 3-36V, the volume is 4X4mm. At the same time, the ADI driver has an error detection alarm function (e.g. UVLO, Open/short Iset, TSD, Open EN protection).

Zhang Jing also introduced the LED driver for low voltage portable devices backlight or Flash applications. In low voltage portable devices such as mobile phones, tablet PCs and other common applications, a large number of system power consumption from the LED backlight. How to reduce the power consumption of LED backlight is essential to improve the use time of portable equipment. ADI's ADP8870 white LED charge pump backlight driver enables battery powered handheld devices to reduce power consumption by as much as 45%, and does not affect the display quality. The driver set programmable charge pump for LED backlight driver; phototransistor input automatic control LED brightness; and for the management of the output current ratio of PWM (pulse width modulation) input of these three key functions, according to the ambient lighting intensity and display white component image to automatically change the current intensity, thereby greatly reducing power consumption. Moreover, ADP8870 can automatically execute the function, without using the processor to monitor the phototransistor, which can further reduce power requirements and simplify the portable backlight design, so as to prolong the life time of the battery.

For many low voltage portable devices such as mobile phone, tablet computer and other needs in the light of the poor environment or call when shooting the image of this demand, the company launched a ADI programmable ADP1650 1500mA LED driver. ADP1650 in less than the area of the 17mm2 integrated programmable 1.5MHz or 3.0MHz synchronous inductive boost converter with low cost, high 1mm, small 1 H power inductors and 0603 dimensions of the input and output capacitors, realize the design of high power flash complete. The LED driver can work efficiently in the entire battery voltage range, can make the low light environment to achieve the maximum brightness of the flash, and make the flash during the battery current consumption. ADP1650 is easy to connect with the latest image sensors and processors to capture images with excellent image quality in low light conditions.