Page 19 - PEN eBook October 2022

DESIGN Design

This article will present the challenges faced by electronic engineers when designing these new
illumination products, focus on selecting the correct LED driver for a multi-beam headlamp, and review
how adaptive feedback control (AFC) improves thermal management. These topics will be explained

through the design of a multi-beam headlight, from a high-level system overview to LED driver selection.

MATRIX HEADLAMP

Multi-beam headlights contain three
main components: LEDs, an LED
driver, and a pre-regulator (buck
converter) (see Figure 1).

First, a matrix of LEDs illuminates

the road layout. Due to PCB
size specifications and thermal
Designing constraints, the system in this

article has 84 LEDs that are
Cooler-Running, distributed in three rows and
30 columns. Second, to adapt the
light in the environment, the LEDs
Multichannel Dynamic in the system must be controlled

by LED drivers. For this example, we
Automotive Lights Figure 1: Matrix headlamp used six MPQ7225-AEC1 devices.

Finally, because all of the headlight
components are powered by the car
By Oster Hsu, applications engineer; Xavier Ribas, applications engineer; and battery, the system incorporates a pre-regulator to step down the voltage from the car battery so
Junjian Zhao, manager of technical marketing and applications engineer, all that the voltage matches the LED and LED driver specifications.
at Monolithic Power Systems
SELECTING AN LED DRIVER

Across the automotive landscape, the push for electrification has yielded the incredible proliferation of During headlight design, there are two main constraints that designers face: PCB size and thermals.
exotic vehicles. Yesterday’s bulky, single-function lights are being replaced with newer, slender designs The PCB must be as small as possible to fit into the headlamp case, which means it is vital to
that wrap around a car’s front, back, or sides. The drive to go beyond traditional illumination or signaling minimize the number of components. In addition, lighting designs must carefully consider the
means that tomorrow’s automotive lights will be challenged to display sophisticated patterns and application thermals to avoid overheating and damaging the components. With these constraints
algorithms while facing unprecedented constraints in thermal management, form factor, and cost. in mind, the LED driver must be carefully selected for the system specifications.

An example of these new products are adaptive headlights, also known as matrix headlights. These Because the system used as an example in this article demands excellent scalability and a high

headlamps substitute old light bulbs using a matrix of numerous LEDs, which improves thermals and number of channels per part, the MPQ7225-AEC1 was selected. This LED driver reduces the
increases light beam control. Each LED of this matrix is controlled independently to create innovative number of components, as well as the PCB space, without losing LED controllability. Specifically,
and fascinating light designs that improve the driver’s visibility and adjust the light beam to the the design uses six MPQ7225-AEC1 devices, for a total of 14 channels per part (see Figure 2).
environment. By switching off the unnecessary light elements and keeping the rest of the area fully lit, The MPQ7225-AEC1 is a 16-channel LED driver, so it can control up to 96 LEDs individually, though
headlamps can illuminate what drivers need to see without distracting other road users. this amount is not required for this design.

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