Six technical details that have to be paid attention to in LED lighting design

The high performance, long life and environmentally friendly performance of LED lamps are widely recognized.

LED high energy saving: DC drive, ultra-low power consumption (single tube 0.03 watts - 1 watt) electro-optical power conversion is close to 100%, the same lighting effect is more than 80% energy saving than traditional light source. Led long life: led light source is called longevity lamp. Solid cold light source, epoxy resin package, there is no loose part in the lamp body, there are no shortcomings such as filament light-emitting, heat deposition, fast light decay and so on.

LED life: The service life can reach 50,000 to 100,000 hours, which is more than 10 times longer than the traditional light source.

LED environmental protection: led is a green light source, and environmental protection benefits are better. There is no ultraviolet and infrared rays in the spectrum, low heat and no stroboscopic, no radiation, and waste can be recycled, no pollution, no mercury, cold light source, safe touch, is a typical green lighting source.

LED light source working characteristics The VF voltage of the LED light source for illumination is very low, generally VF=2.75-3.8V, IF is 15-1400mA; therefore, the output voltage of the LED driver IC is VFXN or VFX1, and the IF constant current is 15-1400mA. The LED light source used in LED lamps has two types of low power (IF=15-20mA) and high power (IF) (200mA)). Low-power LEDs are mostly used for LED fluorescent lamps, decorative lamps and grille lamps; high-power LEDs are used for Home lighting, spotlights, underwater lights, wall washers, street lights, tunnel lights, car work lights, etc. The power LED light source is a low-voltage, high-current driving device. The intensity of the light is determined by the current flowing through the LED. If the current is too strong, the LED will be attenuated. If the current is too weak, the LED will be affected. Therefore, the LED is driven. Constant current power supply is required to ensure the safety of high-power LEDs and achieve the desired luminous intensity. In the field of LED lighting, to reflect the characteristics of energy saving and long life, it is very important to choose a good LED driver IC. Without the matching of good driver IC, the advantages of LED lighting cannot be reflected. Therefore, LED lighting design needs attention to the technical details of LED lamps for low-voltage driver chips:

1. The nominal input voltage range of the driver chip should meet DC8-40V to cover the application surface. The withstand voltage should be greater than 45V. The output voltage of the simple bridge rectifier will fluctuate with the grid voltage when AC12V or 24V input. Especially when the voltage is too high, the output DC voltage will be too high. If the driver IC cannot adapt to the wide voltage range, it will be broken down when the grid voltage rises, and the LED light source will be burnt.

2. The nominal output current requirement of the driver chip is greater than 1.2-1.5A. As the LED light source for illumination, the nominal working current of the 1W power LED light source is 350mA, and the nominal working current of the 3W power LED light source is 700mA. Larger ones require more current, so the driver ICs used in LED lighting must have sufficient current output. The design of the product must be such that the driver IC operates at 70-90% of the best working area of ​​the full negative output. Driver ICs that use full negative output currents have poor heat dissipation in the narrow space of the luminaire, which is prone to fatigue and early failure.

3. The output current of the driver chip must be constant for a long time, the LED light source can be stably illuminated, and the brightness will not flicker; the same batch of driver chips are used under the same conditions, and the output current should be as uniform as possible, that is, the dispersion is small, so High-volume automated production line production can be effective and orderly; for the output current has a certain discrete drive chip must be selected before the factory or put into the production line, adjust the resistance of the current setting resistor (Rs) on the PCB, so that The constant current driving board of the LED lamp produced by the same has the same brightness of the same kind of led light source, and maintains the consistency of the final product.

4. The package of the driver chip should be beneficial to drive the rapid dissipation of the chip die, such as bonding the die directly to the copper plate, and having a pin extending directly outside the package for direct soldering on the copper foil of the PCB. Rapid thermal conductivity (Figure 1). For example, on a silicon die similar to 4X4mm, it takes a long time to pass 300-1000mA current, which inevitably has power consumption, which will inevitably heat up. The physical heat dissipation structure of the chip itself is also crucial.

5. The ability of the driver chip itself to resist EMI, noise and high voltage is also related to whether the entire LED lamp product can pass CE, UL and other certifications. Therefore, the driver chip itself must use excellent topography and high voltage at the beginning of design. Production Process.

6. The power consumption requirement of the driver chip is less than 0.5W, and the switching operating frequency requirement is greater than 120Hz, so as to avoid visible flicker caused by power frequency interference. Led green lighting promotes the development of driving chips to innovative designs. LED lighting is inseparable from driving chips, so LED light source driving ICs with multiple functions are required. Led lamps use AC power below 36V to consider non-isolated power supply. For example, 220V and 100V AC power should be considered for isolated power supply. Directly using the AC100-220V driver chip, due to the application of the demanding requirements, there are higher technical requirements and greater difficulty, and countries are currently working hard to develop. The massive demand market for led luminaires gives all IC design companies the chance to succeed again, with rapid transformation and early product launch, and many opportunities to win.