A brief discussion on the selection criteria of LED lighting driver IC

　　In the field of LED lighting, in order to reflect the energy-saving and long life characteristics of LED lamps, it is crucial to correctly select LED driver ICs. Without a good driver IC match, the advantages of LED lighting cannot be reflected. So when selecting LED driver ICs, what performance indicators and usage methods should be paid attention to?

　　LED lighting has developed rapidly in recent years, and LED has been widely recognized as a green, environmentally friendly, clean light source. LED light sources have long service life, energy saving, simple and convenient application, and low cost, so they will be widely used in home lighting. According to statistics from OSRAM Optical Semiconductors, the global annual shipment of home lighting lamp holders is about 50 billion.

　　LED light source technology is becoming more mature, and the luminous lumens per watt are increasing rapidly, which has led to a gradual price reduction. For example, the price of a 1W LED light source in the spring of 2008 was already one-third of the price in the spring of 2006, and will drop to one-quarter of the price in the spring of 2009.

　　The massive market of LED green lamps and the steady growth in demand for several years will be the super tsunami of the integrated circuit industry in the consumer electronics market after VCD, DVD, mobile phones and MP3!

　　The superior performance of LED lamps, such as high energy saving, long life and environmental protection, has been widely recognized.

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

　　2. Long life of LED: LED light source is called long life lamp. It is a solid cold light source, epoxy resin encapsulated, and there is no loose part in the lamp body. It does not have the disadvantages of easy burning of filament light, heat deposition, and fast light decay. The service life can reach 50,000 to 100,000 hours, which is more than 10 times longer than the traditional light source.

　　3. LED is environmentally friendly: LED is a green light source with better environmental benefits. There is no ultraviolet and infrared in the spectrum, low heat, no flicker, no radiation, and the waste is recyclable. It is pollution-free and does not contain mercury. It is a cold light source and safe to touch. It is a typical green lighting source.

　　Working characteristics of LED light source

　　The VF voltage of LED light sources for lighting is very low, generally 2.75~3.8V, and IF is generally 15~1,400mA. Therefore, the output voltage of the LED driver IC is VFxN or VFx1, and IF maintains a constant current of 15~1,400mA. There are two types of LED light sources used in LED lamps: low power (IF is 15~20mA) and high power (IF is greater than 200mA). Low-power LEDs are mostly used to make LED fluorescent lamps, decorative lamps, and grille lamps. High-power LEDs are used to make home lighting, spotlights, underwater lamps, wall washers, street lamps, tunnel lamps, car work lamps, etc. High-power LED light sources are low-voltage, high-current driven devices, and their luminous intensity is determined by the current flowing through the LED. Excessive current will cause LED light attenuation, and too little current will affect the luminous intensity of the LED. Therefore, the LED driver needs to provide a constant current power supply to ensure the safety of high-power LED use and achieve the ideal luminous intensity. In the field of LED lighting, in order to reflect the energy-saving and long life characteristics of LED lamps, it is very important to correctly select LED driver ICs. Without a good driver IC match, the advantages of LED lighting cannot be reflected.

　　LED lamps' requirements for low voltage driver chips

　　1. The nominal input voltage range of the driver chip should meet the requirements of DC 8~40V to cover a wide range of applications. The withstand voltage should preferably be greater than 45V. When the input is AC 12V or 24V, the output voltage of a 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 break down when the grid voltage increases, thereby burning out the LED light source.

　　2. The nominal output current of the driver chip is required to be greater than 1.2~1.5A. As an LED light source for lighting, the nominal operating current of a 1W LED light source is 350mA, and the nominal operating current of a 3W LED light source is 700mA. High-power LED light sources require greater currents, so the driver IC used in LED lighting fixtures must have sufficient current output, and when designing products, the driver IC must also work in the optimal working area of ​​70~90% of the full-load output. Using a driver IC with full-load output current will not dissipate heat well in the narrow space of the lamp, which can easily cause 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 flickering. When the same batch of driver chips are used under the same conditions, their output current should be as consistent as possible, that is, the discreteness should be small, so that it can be produced effectively and orderly on a large-scale automated production line. For driver chips with a certain degree of discreteness in output current, they must be selected in different grades before leaving the factory or being put into production line, and the resistance value of the current setting resistor on the PCB board must be adjusted so that the constant current driver board of the LED lamps produced has the same brightness for the same LED light source, so as to maintain the consistency of the final product.

　　4. The package of the driver chip should be conducive to the rapid heat dissipation of the driver chip die, such as directly binding the bare chip to the copper plate, and having a pin directly extended outside the package, so as to facilitate direct soldering on the copper foil of the PCB board for rapid heat conduction (Figure). If a 300~1,000mA current is passed through a chip like 4X4mm for a long time, power consumption and heat will inevitably be generated. 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 whether the entire LED lighting product can successfully pass CE, UL and other certifications. Therefore, when designing the driver chip, advanced topology and high-voltage production process should be selected.

　　6. The power consumption of the driver chip itself is required to be less than 0.5W, and the switching operating frequency is required to be greater than 120Hz to avoid visible flickering caused by power frequency interference.

　　In short, LED green lighting promotes the development of driver chips towards innovative designs. LED lighting cannot be separated from driver chips, so multifunctional LED light source driver ICs are needed. If the LED lamp uses an AC power supply below 36V, non-isolated power supply can be considered; if 220V and 100V AC power supply are used, isolated power supply should be considered. Directly using AC 100~220V driver chips has higher technical requirements and greater difficulties due to the demanding requirements of the application on volume. At present, all countries are working hard to develop them. The massive demand market for LED lamps gives all integrated circuit design companies the opportunity to succeed again. If they can quickly transform and produce products early, they will have many chances to win.