September 11, 2019
| By: Yin Wu
Blogger, Maxim Integrated
Walking through New York City’s Times Square is an illuminating experience, to say the least. Adorning buildings on every block are walls of LED displays promoting products, entertainment options, financial services, and more. Compared to conventional lighting, LED lighting is much more energy efficient, robust, and longer lasting, and it enables the bright, vivid colors that make commercial and industrial applications shine.
With all of these advantages, it’s no wonder that automotive designers, too, have embraced LED lighting technology. The 1984 Corvette, which had an LED center high mount stop lamp, marks the first use of LED lighting in an automotive application. LEDs illuminate 0.2 seconds faster than incandescent bulbs, so they were a natural fit in brake lights.1 Today, automotive LED lighting is providing benefits in safety as well as style. An LED driver is required to regulate constant current and also to protect the LEDs from transient conditions, such as overvoltage and overcurrent. To achieve the best performance, designers should select LED drivers that address challenges related to electromagnetic interference (EMI), dimming capabilities, efficiency and size, and design flexibility. Let’s take a closer look at each of these challenges and discuss how LED driver technology with the right features can help.
Automotive LED headlights benefit from LED drivers that deliver high efficiency, small size, and design flexibility.
Switch-mode LED drivers used in exterior lighting (headlamps and tail lamps) will create efficient designs, but also adds EMI challenges. To minimize EMI, many automakers are forced to spend time and resources experimenting with different layouts and filtering methods. Some opt to implement multiple components in their system to pass EMI specifications. Designers need a less taxing way to lower EMI.
For LED headlights, dimming is an important capability, especially for matrix and pixel lighting. However, inadequate dimming performance can create issues. Dimming via pulse-width modulation provides a good approach for maintaining chromaticity and uniform brightness and also to prevent noticeable flickering. An alternative method utilizes amplitude modulation. While amplitude modulation can be simple and cost effective for a single LED device, it may not yield the best overall performance when it comes to the arrays of LEDs typically found in automotive lighting applications.
LED lighting applications need a robust and constant current source, especially when they run at higher current levels. However, LED lighting applications come in multiple topologies, creating power, thermal, and design complexities. So the LED drivers must have the flexibility to accommodate these different topologies. In some cases, a single driver with a single topology may not be as well suited to the application at hand as a single buck LED driver.
Efficiency and size are important concerns to address as well. For example, managing the higher currents of pixel lighting through a large number of LEDs calls for high efficiency in the LED drivers in order to reduce power dissipation and manage the thermal requirements. Small solution size is important, too, given the space constraints inside vehicles.
Maxim’s new MAX25610A and MAX25610B synchronous buck, buck-boost LED drivers/DC-DC converters bring together industry-leading EMI performance and high efficiency in a 5mm x 5mm TQFN package. The devices drive up to eight HBLEDs from the car battery, while integrating components such as low RDS_ON high- and low-side switching MOSFETs and an internal current sense option to reduce bill of materials (BOM) costs. They provide a wide input voltage range from 5V to 36V with up to 90% efficiency in buck-boost mode. Programmable on-chip PWM dimming allows for fine dimming control without the use of a separate microcontroller. With configuration in buck, buck-boost, and boost modes, you can support an array of LEDs and topologies in high-performance exterior and front lighting applications. The ICs pass CISPR 25 EMI specifications.
These characteristics and functions make the MAX25610A and MAX25610B ideal to support industrial and commercial lighting applications as well as automotive. Industrial and commercial lighting face the same types of challenges around EMI, efficiency, solution size, and flexibility. And they can reap the same benefits of LED lighting. The LED lighting market is anticipated to reach US$56.6 billion by 2023. Various application areas are now replacing traditional lighting sources with LEDs. For example:
To assess the MAX25610A/B for your next automotive, industrial, or commercial lighting application, check out the MAX25610 evaluation kit. The kit is set up for buck-boost configurations and operates from a 5V to 18V DC supply voltage. It delivers up to 1.1A to one string of LEDs.