Development Trend of LED Driver IC Design

LED driver chips need to ensure the consistency and stability of LED current output as much as possible

In view of the poor consistency of LEDs, LED driver chips need to ensure the consistency and constancy of LED current output as much as possible. LED driver chips need to drive one or more LEDs. The brightness of LEDs is roughly linearly proportional to the amount of current passing through them. Therefore, in order to make the LEDs emit the same brightness, the current of the LEDs connected together must be kept as consistent as possible.

In terms of the precise current value control method, AT400, AT310, and AT380 use a boost topology, and the AT310 and 300 current sampling resistor feedback voltage is as low as about 19mV. AT8860 uses a built-in switch tube hysteresis buck topology, AT8001 uses a 1X, 1.5X charge pump topology, and AT8004 uses a negative voltage charge pump topology, which has higher conversion efficiency than AT8001. In order to ensure the safety and reliability of full temperature range applications, the AT8596LED driver chip linearly reduces the LED feedback threshold voltage in the chip circuit design when the temperature exceeds 42°C to reduce the LED drive current. When the AT8800LED driver chip detects the low-side current, the CS_ terminal is independent of the GND pin to minimize the impact of common-mode noise and improve the accuracy of the LED drive current.

Different application requirements correspond to different LED driver chips

The main challenge and problem currently faced is the cost of LED tube cores. To provide cost-effective LED driver chips, it is necessary to provide diversified driver chip products according to different customer needs. Different application requirements correspond to different LED driver chips. At the same time, the drive circuit should be simplified as much as possible, peripheral components should be reduced, and the efficiency of LED driver chips should be improved.

The market demand for LED driver ICs, if classified by application, can be divided into three categories, namely consumer electronics, automotive lighting, and architectural decoration and home lighting. The application characteristics of consumer electronics are that they use batteries as energy, generally 3.0~8.4V, so low-voltage, low-current LED driver ICs are the most suitable products with large quantities and wide applications. In terms of automotive lighting products, since their power supply | voltage regulator comes from the car battery, generally 24V, 36V, 48V power rails, they require higher voltage step-down LED driver ICs. As for architectural decorative lighting and home lighting, LED driver ICs that directly convert AC power into DC power are required, that is, converting AC power into DC power and matching the LED voltage and current at the same time. Therefore, LED driver ICs for different applications will also be completely different.

In terms of market demand, the number of LEDs used in automotive lighting is relatively large, and most of them are driven in series or parallel, requiring a higher voltage, which is very convenient for the power supply of 48V car batteries. At present, new LED driver ICs that can withstand 60V high voltage are relatively common. In the automotive front-end market, the market for directly using LED instrument | dashboard backlight, front and rear fog lights, third brake lights, turn signals, and tail lights is very promising.

For building decoration and household lighting, LED driver ICs that can directly convert AC power into DC power are needed. Currently, single SoC integrated circuit products are not available, and most of them are modules. Building decoration lighting has been widely used in many cities, and has good energy-saving effects. In the future, the demand for household LED lighting will be very large. However, the current technology and production costs of household LED lighting are still some distance away from mass production.

As for LED driver ICs for consumer electronic products, they have relatively mature technology, products and a relatively mature market.

LED lighting driver chip design direction

Regarding the design direction of LED lighting driver chips, in 2009, Core View Technology launched the boost LED driver chips AT310, AT300, AT400, and the linear high-voltage LED driver chip AT8800. In early 2010, it will launch the buck LED driver chips AT8860 and AT8802, and the built-in switch tube boost LED driver chip AT380. Core View Technology will continue to expand its cost-effective LED lighting driver chip products based on customer needs, including LED driver chips for buck-boost applications, high-current LED driver chips, and high-voltage and high-current LED driver chips.

Taking AT8800 as an example, the current regulator can operate in the input voltage range of 6.5V to 40V, providing a total current of up to 350mA to drive one or more columns of high-brightness LEDs. An external current-sense resistor in series with the LED is used to adjust the output current of the AT8800. The enable input can achieve a wide range of "pulse" brightness control. The waveform shaping circuit reduces EMI. The differential current detection input improves noise suppression. The AT8800 is very suitable for applications requiring high-voltage input and can withstand automotive load dumps up to 40V. The on-board adjustment components greatly reduce the number of external components and provide ±3.5% output current accuracy. The device also provides 5V regulated output as well as short-circuit protection and thermal protection.

LED backlight chip design direction

Core View Technology has launched the AT8001 LED charge pump driver chip that meets the needs of handheld device LCD backlight LED driver applications. In early 2010, it will launch the AT8006 1-wire interface LED charge pump driver chip and the AT8004 high-efficiency negative voltage LED charge pump driver chip. Core View Technology is also currently designing the AT8596 boost LED driver chip, which can drive 2 to 9 LEDs in series.

In addition to continuously striving for technological excellence, we also need to strengthen technical support for customers and respond quickly to customer needs in order to stand out in the fierce competition.