How to choose the right LED lighting driver IC

LED lighting has been making rapid progress in the near future, and LED has been widely recognized as a clean and green light source. LED light source has long service life, energy saving and power saving, simple and convenient application, low cost of use, and therefore will be applied in a large amount in home lighting. According to 2008 survey by OSRAM Optics Semiconductor, the number of home lighting units in the world is about 500. Billion.

The technology of LED light sources has matured, and the luminous lumens per watt have grown rapidly, prompting them to reduce their prices year by year. Taking 1W LED as an example, the price in the spring of 2008 is already one-third of the price in the spring of 2006. In the spring of 2009, it will fall to a quarter in 2006.

The massive market of LED green lamps and the continuous and stable growth for several years will be the super tsunami of the IC market following the VCD, DVD, mobile phone and MP3 consumer electronics market!

LED lamps are widely recognized for their high energy-saving, long-life, and environmental-friendly advantages.

1.LED high energy-saving: DC drive, ultra-low power (single tube 0.03~1W) electro-optical power conversion is close to 100%, the same lighting effect is more than 80% energy saving than traditional light sources.

2. LED long life: LED light source is called longevity lamp. Solid cold light source, epoxy resin encapsulation, there is no loose part of the lamp body, there is no weakness in the filament light-emitting, heat deposition, light decay, etc., the service life can reach 50,000 to 100,000 hours, and the service life is longer than the traditional light source. More than times.

3. LED environmental protection: LED is a green light source, environmental protection and better efficiency. No ultraviolet and infrared rays in the spectrum, low heat and no flicker, no radiation, and the waste can be recycled, no pollution, no mercury element, cold light source, can be safely touched, belonging to a typical green lighting source.

Operating characteristics of LED light source The VF voltage of the LED light source for illumination is very low, typically 2.75 to 3.8V, IF is generally 15 to 1,400mA. Therefore, the output voltage of the LED driver IC is VFxN or VFx1, and the IF is maintained at a constant current of 15 to 1,400 mA. The LED light source used in LED lamps has two types of low power (IF 15-20mA) and high power (IF greater than 200mA). Low-power LEDs are mostly used to make LED fluorescent lamps, decorative lights, and grille lights. High-power LEDs are used for home lighting, spotlights, underwater lights, wall washers, street lights, tunnel lights, and automotive work lights. The power LED light source is a low voltage, high current driven device whose luminous intensity is determined by the amount of current flowing through the LED. If the current is too large, the LED light will be attenuated. If the current is too small, the LED's luminous intensity will be affected. Therefore, the LED driver needs to provide a constant current source to ensure the safety of the high-power LED while achieving the desired luminous intensity. In the field of LED lighting, the correct selection of LED driver ICs is critical in order to demonstrate the energy saving and long life characteristics of LED lamps. Without the matching of a good driver IC, the advantages of LED lighting cannot be reflected.

1. The nominal input voltage range of the driver chip should meet DC 8~40V to cover a wide range of application needs. The pressure resistance is better than 45V. When the input is AC 12V or 24V, the output voltage of the simple bridge rectifier will fluctuate with the grid voltage, especially when the voltage is high, the output DC voltage will also be high. If the driver IC does not have a wide input voltage range, it will often be broken when the grid voltage rises, thereby burning the LED light source.

2. The nominal output current requirement of the driver chip is greater than 1.2~1.5A. As a lighting LED light source, the nominal operating current of a 1W power LED light source is 350mA, and the nominal operating current of a 3W power LED light source is 700mA. Power LED light sources require more current. Therefore, the driver ICs used in LED lighting fixtures must have sufficient current output. When designing products, the driver ICs must also be operated in the optimal working area of ​​70 to 90% of the full-load output. The use of a driver IC with a full-load output current results in poor heat dissipation in a narrow space of the lamp, which easily leads to fatigue and early failure of the lamp.

3. The output current of the driver chip must be kept constant so that the LED can emit light stably without flicker. When the same batch of driver chips are used under the same conditions, the output current should be as uniform as possible, that is, the dispersion should be small, so that it can be guaranteed to be effective and orderly when produced in high-volume automated production lines. For a drive chip with a certain discrete output current, it must be selected before shipment or into the production line, adjust the resistance value of the current setting resistor on the PCB board, so that the LED lamp constant current driver board for the same type of LED The brightness of the light source is consistent to maintain the consistency of the final product.

4. The driver chip package should be conducive to the rapid heat dissipation of the driver chip die, such as the direct bonding of the die on the copper board, and a pin directly extends to the outside of the package, so as to be directly welded on the PCB board copper foil Rapid heat conduction (Figure). If you want to pass a current of 300~1,000mA for a long time on a 4X4mm chip, it will inevitably generate power and generate heat. Therefore, the physical heat dissipation structure of the chip itself is also very important.

5. The ability of the driver chip to resist EMI, noise, and high voltage is also related to the ability of the entire LED lamp product to successfully pass CE, UL, and other certifications. Therefore, in the design of the driver chip, advanced topological structures and high pressure production processes must be selected.

6. The self-power consumption requirement of the driver chip is less than 0.5W, and the operating frequency of the switch is required to be greater than 120Hz, so as to prevent the occurrence of visible flicker due to the power frequency interference.

In short, LED green lighting has driven the development of driver chips to innovative designs. LED lighting cannot be separated from the driver chip, so a multifunctional LED light source driver IC is needed. If LED lamps use AC power below 36V, non-isolated power supply can be considered; if 220V and 100V AC power supply are used, isolated power supply should be considered. The direct use of the AC 100 ~ 220V driver chip, due to the application of the volume of the demanding requirements, there are still higher technical requirements, greater difficulty, the current countries are working hard to develop. The massive demand market for LED lamps has given all IC design companies another chance to succeed. If they can quickly transform and produce products early, there are many opportunities to win.