LED lamps on the low-voltage driver chip

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1) the drive nominal input voltage range should meet DC8-40V, to cover the needs of the application surface, the pressure, such as greater than 45V better; AC 12V or 24V input bridge rectifier output voltage with the grid voltage of the chip fluctuations, especially the output DC voltage will be high when the hig h voltage driver IC can not adapt to such a wide voltage range, often in the grid voltage is increased, the breakdown of the LED light source also burned.

2) driver chip s nominal output current requirements is greater than 1.2-1.5A, as the lighting of the LED light source, 1W power LED light source with a nominal operating current of 350mA, 3W power LED light source with a nominal operating current of 700mA. power requires more current, so the choice of LED lighting driver IC must have enough current output, the design of products necessary to make 70-90% of the driver IC to operate at full negative output of the best work area. Full load output current drive IC for led high bay lighting small spaces, poor heat dissipation, fatigue and early failure.

3) the output current of the driver chips necessary for a long time constant, LED light source to stabilize the light, the brightness do es not blink; with the number of driver chips are used under the same conditions, the size of the output current to be as consistent as possible, which is discrete, so high-volume automated production line to be effective and orderly; certain discrete driver chips will be selected in the factory or put into the production line before the sub-file for the output current, adjust the PCB current setting resistor (Rs) of resistance size, so that constant current driver board of the production of LED lamps of similar LED light source luminance, to maintain the consistency of the final product.

4) driver chip package should be conducive to the rapid cooling of the driver IC chip, such as the die (Die) binds directly to the copper, and a Pin is a direct extension of the package, easy to be soldered directly on the PCB copper foil rapid thermal conductivity (Figure 3). 4X4mm a similar silicon die long by 300-1000mA current, there must be power, is bound to heat the chip i tself, the physical thermal structure is also crucial.

5) driver chip s own resistance to EMI, noise, high voltage capacity is also related to the LED lighting products certified by CE, UL and other successful, so the driver chip itself should be used and the beginning of the design good topology and high-pressure production process.

6) driver chip power requirements of less than 0.5W, the requirements of the switching frequency greater than 120Hz in order to avoid frequency interference and produce visible flicker.

Simple application program PT4115PT4115 with a highly integrated DC / DC-Buck → Constant, Current features, it will be DC voltage directly into a stable constant current output. Simple applications of the PT4115 practical circuit is shown in Figure 4.

PT4115 switching frequency using the shaking frequency technology to effectively reduce the EMI frequency jitter technology (Frequency Jitter) is the high bay lighting from scattered harmonic energy to begin to address EMI issues. Frequency Jitter refers to the operating frequency of the switching power supply is not fixed, but periodically from narrowband into broadband way to reduce EMI, and to reduce electromagnetic interference. Frequency jitter, harmonic narrow and discrete, amplitude in the higher harmonic frequencies, EMI concentrated in the Feng Jian. Frequency jitter, the harmonic amplitude is reduced and becomes smooth, high harmonics of nearly continuous response. Reduce the effect of EMI is very significant.