LEDs are widely recognized as green and clean light sources. LED long life, energy saving, simple and convenient application, low cost of use, so handheld in mobile phones, MP3, MP4, PMP, DSC (digital camera), PDA, GPS, PND, game consoles, learning machines, laptops, etc. Product LCD backlight; LED flashlight, miner's lamp portable lighting; in architectural lighting, decorative lighting, signage lighting; in the car's dashboard backlight, front and rear fog lights, third brake lights, direction lights, tail lights; and will be in the home lighting Get a huge amount of applications.
LED driver IC current market demand
The current market demand for LED driver ICs is divided into three categories according to the application. One is for consumer electronic products. Its application characteristics are battery-based energy, generally 4.2-8.4V, so low-voltage, low-current LED drivers It is currently a large-volume product; the second is for automotive lighting products, because its power supply comes from the car battery, generally 48V, so it needs a higher voltage step-down LED driver IC; third is architectural decorative lighting and home lighting, then Need to convert the AC directly into a DC LED driver IC, the main function is to convert the AC voltage into a constant current power supply, and at the same time complete the matching with the voltage and current of the LED. Thus LED driver ICs for different applications are completely different.
Consumer electronics LED drivers have more mature technologies, products and relatively mature market. In 2007, the global mobile phone market used 600 billion LED driver ICs, which will continue to grow in 2008.
The number of LEDs used in automotive lighting products is large, mostly in series and parallel drives, requiring high voltages, which is very convenient for power supplies from 48V automotive batteries. At present, there are many new LED driver products that can withstand 60V high voltage. Therefore, the market for LED panel backlights, front and rear fog lamps, third brake lamps, directional lights, and taillights is very optimistic and optimistic in the automotive front-loading market.
Architectural decorative lighting and home lighting require an LED driver IC that converts AC directly into a DC constant current source. Currently, it is not possible to provide a single SOC integrated circuit product, most of which is a modular circuit. Architectural decorative lighting has been widely used in major cities in China, and the energy saving effect is remarkable. The need for social LED lighting for homes will be an astronomical number, but the current domestic LED lighting technology and production costs are still a certain distance from mass production, and efforts are still needed.
LED driver ICs for consumer electronics
The backlight of consumer electronics LCD screens is generally 2-8 LED lights, and most applications are connected in parallel or single power supply. Since 2000, LED driver ICs for consumer electronics have DC/DC switching regulators (Boost), charge pumps (Charge Pumps), constant current sources (Constant), and low dropout regulators (LDOs).
The DC/DC switching regulator uses an inductor to store electrical energy. The inductor easily emits a switching frequency and is susceptible to new interference with radio frequency (RF), so it is used less in mobile phones. The charge pump is also a kind of switching regulator, but it uses capacitors for energy storage, so it does not emit switching frequency, which accounts for the largest share of mobile phones. LED lighting requires IF constant current, constant current source is specially designed and produced for this market. The price of constant current source is 50% of charge pump, so it has a certain share in popular mobile phone products in recent years. The demand for cost reduction of popular mobile phone products, the backlighting drive unit of the mobile phone can still reduce the cost of the LED driver IC. The shutdown voltage of most mobile phones is designed when the battery voltage drops to 3.3V, so the constant current source is designed to be 4.2. The constant current output of V-3.3V is 20-30mA, and the output current of 3.3V or less drops sharply. The selling point of the charge pump is efficiency (η), but most of the charge pump's conversion efficiency is not high at 4.2V-3.3V. When the battery voltage drops to 3.0V-2.5V, its conversion efficiency can reach 85-90%. Unfortunately, most of the current mobile phone solutions do not play their advantages. LDO is a very good low-dropout regulator with stable output voltage. When the load is constant, the current flowing through the load is also constant. Based on this principle, LDO is also a good LED driver. For the current LED driver IC for mobile phones, a DC/DC (Boost) is priced at USD0.12-0.15, a charge pump is priced at USD0.20-0.25, and a constant current source is priced at 0.09- 0.12, an LDO is only a few dollars, there is a certain space for reducing the cost of the backlight unit of the mobile phone. Many popular mobile phones have been selected this year.
In addition to the color screen backlight, the mobile phone needs an LED driver IC, the keyboard backlight of the mobile phone, and the flash of the mobile phone camera also requires an LED driver IC. It is characterized by low voltage and low current because it is powered by batteries.
LCD screen backlight driver for consumer electronics without RF part can choose DC/DC switching regulator. LED is generally used in series + N in parallel. The working voltage is slightly higher, and the working current is better than the series and parallel connection of multiple LEDs. Large LCD screen backlight, as shown in Figure 3 LCD electronic light box. In addition, there are also LED flashlights.
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