LED lighting has been developed by leaps and bounds in the near future. As a green and clean light source, LED has been widely recognized. LED light source has the advantages of long service life, energy saving, simple and convenient application and low cost, so it will be widely used in home lighting. As early as 2008, the global annual shipment of household lighting lamp holders was about 50 billion.

The technology of LED light source is becoming more and more mature, and the luminous lumen per watt is growing rapidly, which promotes its decreasing price year by year. The massive market of LED green lamps and the continuous and stable growth demand for several years will be a super tsunami in the consumer electronics market after VCD, DVD, mobile phone and MP3 in the integrated circuit industry! LED lamps are widely recognized for their superior performance of high energy saving, long life and environmental protection.

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

2. Led long life: LED light source is called long life lamp. The solid cold light source is encapsulated with epoxy resin, and there is no loose part in the lamp body. There are no disadvantages such as easy burning, thermal deposition and fast light decay of the filament. The service life can reach 50000 to 100000 hours, which is more than 10 times longer than that of the traditional light source.

3. LED is beneficial to environmental protection: LED is a green light source with better environmental protection benefits. There are no ultraviolet and infrared rays in the spectrum, low heat, no stroboscopic, no radiation, and the waste can be recycled. There is no pollution, no mercury. It is a cold light source and can be safely touched. It is a typical green lighting source.

How to select the correct driving IC for LED lamps

Working characteristics of LED light source

The VF voltage of LED light source for lighting is very low, generally 2.75 ~ 3.8V, and if is generally 15 ~ 1400ma. Therefore, the output voltage of the LED drive IC is vfxn or vfx1, and the if maintains a constant current of 15 ~ 1400ma. LED light sources used in LED lamps include low power (if is 15 ~ 20mA) and high power (if is greater than 200mA). Low power LED is mostly used to make LED fluorescent lamp, decorative lamp and grid lamp. High power LED is used for home lighting, spotlight, underwater lamp, wall washing lamp, street lamp, tunnel lamp, automobile work lamp, etc. Power LED light source is a device driven by low voltage and high current. Its luminous intensity is determined by the current flowing through the LED. Excessive current will cause LED light attenuation, and too small current will affect the luminous intensity of LED. Therefore, the driving of LED needs to provide constant current power supply to ensure the safety of high-power LED and achieve the ideal luminous intensity. In the field of LED lighting, in order to reflect the characteristics of energy saving and long life of LED lamps, it is very important to correctly select LED Driver IC. Without good matching of driving IC, the advantages of LED lighting cannot be reflected.

Requirements of LED lamps for low voltage drive chip

1. The nominal input voltage range of the drive chip shall meet DC 8 ~ 40V to cover a wide range of application needs. The withstand voltage capacity should be greater 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 drive IC does not have a wide input voltage range, it will often be broken down when the grid voltage rises, thus burning the LED light source.

2. The nominal output current of the drive chip shall be greater than 1.2 ~ 1.5A. As an LED light source for lighting, the nominal working current of 1W LED light source is 350mA, and the nominal working current of 3W LED light source is 700mA. The high-power LED light source needs more current, so the driving IC selected for LED lighting lamps must have sufficient current output, and the driving IC must work in the best working area of 70 ~ 90% of the full load output when designing the product. The driving IC with full load output current does not dissipate heat smoothly in the narrow space of the lamp, which is easy to lead to fatigue and early failure of the lamp.

3. The output current of the driving chip must be kept constant so that the LED can emit light stably and will not flash. When the same batch of driver chips are used under the same conditions, the output current should be as consistent as possible, that is, the discreteness should be small, so as to ensure the effectiveness and order in the production of large-scale automatic production line. For the drive chip with a certain discreteness of output current, it must be selected by grades before leaving the factory or putting into the production line. Adjust the resistance value of the current setting resistance on the PCB board to make the constant current drive board of LED lamps consistent with the luminous brightness of similar LED light sources, so as to maintain the consistency of the final product.

Responsible editor; zl

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