Longding Microelectronics' latest LED driver IC provides high-power drive capability

Because the brightness of the LED is determined by the current passed, in order to keep the brightness constant, all LEDs need to keep the current flowing, and most batteries or other power supplies are similar to the constant voltage source, and the output voltage is followed by Reduced by the use of time, directly using the battery to illuminate the parallel LED will not only cause the brightness is not constant, but also cause the current of each LED to be unbalanced and shorten the service life of some LEDs. Therefore, it is necessary to use a constant current source to drive the LED, and the LED driver IC actually converts the general constant voltage power source into a constant current source. This is why LED driver ICs are needed. China produced 30.7 billion LEDs last year, even if it Only one-tenth of them use LED driver ICs, and considering some driver ICs, one can illuminate multiple LEDs, then at least several hundred billion driver ICs are needed, so this is a very large market.

Longding Microelectronics Co., Ltd. has developed a series of LED driver ICs. Now the PAM2701 is in mass production. It is used to drive the backlight of the mobile phone or PMP LCD screen. This is a charge pump chip, only need to add 4 ordinary Cheap ceramic capacitors can work. It can drive up to 4 LEDs with a forward current of up to 30mA and ensure that the currents of each channel differ by less than 3%. The LEDs to be lit are selected by three control lines. It can work with a lithium battery voltage higher than the forward voltage of the LED, or it can work with a lithium battery voltage lower than the forward voltage of the LED and can automatically switch its mode. Its maximum efficiency is as high as 91%. The package is available in a very small 3x3mm QFN and 4x4mm QFN.

In order to ensure the same current flowing through all the LEDs, another most convenient way is to connect all the LEDs that need to be lit up, which requires a very high driving voltage. For example, if you want to drive 10 LEDs, you need a drive voltage of about 33V. This IC cannot be implemented in a normal 5V CMOS process and must use a 40V BCD process. The PAM2840 is such a chip.

High-power LEDs can achieve higher brightness. Ordinary 20mA LEDs are only 66 milliwatts, and 1W LEDs give higher brightness. In order to drive this 1W LED, Longding Company has developed a PAM2800. It can give 350mA to drive 1W LED when using 4 rechargeable batteries, or 3 ordinary dry batteries, or alkaline batteries, or lithium batteries. The current of the LED can be kept constant during most of the life of the battery. And its working efficiency is as high as 80%-95%.

In order to drive more powerful 3W LEDs, Longding has developed the booster PAM2801. This chip can be used to light a 1W or 3W LED when it is powered by a 1st or a 2nd, or a solar cell. The feedback voltage is only 95mV, and the maximum output current can reach 1A. Up to 90%.

Longding is developing a driver IC for multiple strings of multiple LEDs for backlighting larger screens.

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