New opportunities for LED driver modules in automotive lighting

The advantages of long life, small size, and low power consumption of LED perfectly fit the needs of today's environmentally friendly vehicles, which has also led to the popularity of LEDs in automotive lighting. From the atmosphere lights, signal lights, digital screen backlights inside the car, to the turn lights, brake lights, fog lights and daytime running lights outside the car, LED applications are everywhere. In the near future, LEDs are also expected to replace high-power headlights, mainly halogen or xenon lamps.

Today ’s automotive lighting engineers are designing LEDs to be smaller and more unique, while also facing a series of technical challenges such as improving reliability, resisting electromagnetic interference, and optimizing thermal performance.

High reliability plays an important role in automotive engineering. This is especially important in automotive exterior lighting. The state of the vehicle (turning, parking, alarm, etc.) depends on it. The general principle for maximizing reliability is to minimize the number of components on the board: the fewer components, the fewer potential failure points, and the less material required. The simpler the design, the easier it is to debug and get to market.

In addition, as LED systems shrink, the electronics that drive these systems must also shrink. A common way to achieve small board designs is to increase the switching frequency of the driver, thereby reducing the size of the associated inductance and capacitance. However, higher switching frequencies will cause a sharp increase in electromagnetic interference; electromagnetic interference has a square relationship with the switching frequency, which means that doubling the switching frequency will increase the electromagnetic interference by four times. In order to solve this problem, designers must optimize the circuit layout and select low-loss components while minimizing the sensitive loops with active transient currents. These sensitive paths usually include switches, storage inductors and decoupling capacitors. Another way to reduce electromagnetic interference is to add metal shielding, of course, the cost will also increase significantly, which is unacceptable for the price-sensitive lighting market.

What's more, although LEDs have less power than halogen or incandescent lamps, thermal management is still a big issue because it is directly related to the life expectancy of LEDs. LEDs are famous for their hundreds of thousands of hours of operating life, but the high junction temperature will cause their life to drop dramatically. The severe weather conditions that vehicles may work on, will also further reduce the life of LEDs.

MPS took these key issues into consideration when developing the industry's most advanced automotive LED driver module, the new MPM6010-AEC1. This 36V, 1.5A, LED module integrates a synchronous step-down LED driver with automotive-grade inductors and decoupling capacitors (Figure 1), which is suitable for automotive interior and exterior lighting applications up to 15W. MPM6010 compact 3mmx5mm package greatly simplifies and reduces the circuit board layout. As shown in Figure 2, only four external components are needed to fully implement the LED driver solution.

MPM6010-AEC1 uses MPS's low RDS (ON) process with independent intellectual property rights, which has been well received in DC / DC converters. MPM6010-AEC1 can provide more than 90% efficiency at 2.2MHz switching frequency, effectively preventing LED overheating. Figure 3 shows the measured efficiency of 1 and 2 series LEDs in a practical application at a 2.2MHz switching frequency.

MPM6010-AEC1 helps to improve the reliability of the system by reducing the number of required components. As shown in Figure 2, a module replaces 4-6 independent components of a discrete driver. It should be pointed out that the internal inductor meets the AEC-Q200 standard, and the entire module has passed AEC-Q100.

MPM6010 wraps the key circuit with transient current inside the module, so the anti-electromagnetic interference ability is greatly optimized, which helps customers to pass CISPR25 Class 5 (automotive electromagnetic compatibility standard) faster and easier.

Finally, the MPM6010-AEC1 thermal foldback technology implements LED thermal management through the PWM dimming input (EN / DIM) pin or LED current adjustment feedback pin (FB). Figure 5 shows the implementation principle of the latter. When the temperature of the external thermistor reaches a critical threshold, the LED current is throttled back. This thermal foldback circuit, coupled with built-in safety functions, over-temperature protection, and LED open-circuit and short-circuit detection modules, can keep the LED's service life better while keeping the LED in a safe working range.

MPM6010 meets AEC-Q100 first-class standard, adopts 3mmx5mmx1.6mm QFN package, Wettable Flank can be selected to assist automatic optical inspection.

Automakers have set strict performance and size targets for LED lighting systems, and market trends indicate that these standards will only become more stringent over time. Advanced integrated drive modules such as MPM6010 can help meet product requirements such as high reliability, anti-electromagnetic interference, optimized thermal performance, make it easier to achieve system design goals, and pave the way for a new generation of more complex lighting and signal systems.