Guest blog from Tamer Kira
High-brightness (HB) light emitting diodes (LED) are making driving safer, reducing energy consumption and, as a side benefit, giving automotive designers more creative license in headlamp designs.
LEDs can save 50-70% of the energy use that traditional lighting technologies consume, reducing carbon emissions in the process. They also last longer, boasting lifetimes of 50,000 hours or more. And, because they turn on and off faster than incandescent lamps, they’re ideal for applications like brake lights.
From a design standpoint, though, working with HB LED technologies can be challenging, particularly when it comes to electromagnetic interference (EMI). These unwanted noise signals, which originate from the high switching frequency of the LED drivers, can degrade circuit performance or, if severe, inhibit circuit function. EMI can also have an adverse effect on other vehicle subsystems, such as the radio.
There are various techniques to control EMI, but many also come with tradeoffs. One idea is to reduce the switching frequency of the LED drivers. However, high frequency helps maintain the energy efficiency and long-lasting operation of the LEDs, so this approach really isn’t viable. Filtering the drivers can help, as can using LED driver ICs that are designed specifically to minimize EMI effects. For example, during PWM dimming, wave-shaping circuitry that smooths the switching edges can reduce radiated EMI. Maxim’s MAX16800 high-voltage, 350mA, adjustable linear HB LED driver offers wave-shaping circuitry.
Another method to control EMI is internal frequency dithering (or modulating). By modulating the switching frequency, you can lower the peak energy and redistribute it to other frequencies and their harmonics. Spread-spectrum techniques can even move the EMI frequency to bands where noise isn’t a problem, which is great when noise affects sensitive parts of the circuit. Spread-spectrum techniques can also help meet regulatory standards for EMI, since such standards typically specify maximum EMI energy at certain points in the spectrum.
Providing frequency dithering for spread-spectrum applications, Maxim’s MAX16833 family of HB LED drivers can help you improve EMI performance in LED headlamps. The product family can support multiple automotive lighting applications, including high-beam/low-beam/signal lights, daytime running lights, fog lights, and adaptive front-lighting assemblies. EMI noise reduction is one of the product family’s key benefits. The family also reduces harness wiring, supports high-power applications with robust fault protection, and reduces system bill of materials (BOM) costs with their support for input voltages up to 65V.
Tamer Kira is a business director in the Automotive Business Unit at Maxim Integrated, where he began his career as a test engineer. In his current role, he oversees the test engineering team for his business unit, focusing on improving quality and implementing best practices. He is a graduate of San Jose State University.