LED lamps' requirements for low voltage driver chips

LED lighting has developed rapidly in recent years. As a green and clean light source, LED has been widely recognized. 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 survey statistics, the annual global shipment of home lighting lamp holders is about 50 billion.

1. The nominal input voltage range of the driver chip should meet DC8-40V to cover the needs of the application. It is better if the withstand voltage can be greater than 45V . When AC 12V or 24V is input, 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 cannot adapt to the wide voltage range, it will often be broken down when the grid voltage increases, and the LED light source will be burned out.

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 . Larger currents are required for larger power sources. Therefore, the driver IC selected for LED lighting fixtures must have sufficient current output. When designing products, the driver IC must 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, and it is easy to fatigue and fail early.

3. The output current of the driver chip must be constant for a long time so that the LED light source can emit light stably and the brightness will not flicker. 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 production on large-scale automated production lines can be effective and orderly. Driver chips with a certain discreteness in output current must be graded before leaving the factory or being put into production lines, and the resistance value of the current setting resistor (Rs) on the PCB board must be adjusted so that the constant current driver board of the LED lamps produced has consistent brightness for similar LED light sources, thereby maintaining 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 tube core, such as directly binding the tube core (Die) on the copper plate, and extending a pin directly outside the package, so that it can be directly soldered on the copper foil of the PCB board for rapid heat conduction ( Figure 1) . For example, if a 300-1000mA current is passed through a silicon chip tube core of similar size 4X4mm for a long time , there will inevitably be power consumption and heat, so the physical heat dissipation structure of the chip itself is also crucial.

5. The driver chip's ability to resist EMI , noise, and high voltage also affects whether the entire LED lighting product can pass the test.