EMI is Critical When Designing High-Brightness LEDs
Switching Frequency Programmable with Proprietary Current-Mode Control Method

Light-emitting diodes (LEDs) are used in various fields including industrial, commercial, and outdoor applications. Beyond the lighting market, LEDs are used in signage, automotive lighting, mobile devices, and monitors. Among these, the automotive LED market is drawing attention from the lighting industry as a B2B business.

As automotive front and rear lighting transitions from conventional halogen lighting to LED lighting, according to LED Insight, the global automotive LED market is projected to grow at over 8% annually, with a market size of $2.3 billion (approximately 2.5778 trillion won) in 2020.

As daytime running lights (DRL) installation becomes mandatory, the automotive LED lighting market is expected to expand. Daytime running lights are small lamps mounted around the headlights that emit light even during the day using high-brightness LEDs to prevent accidents. High-brightness LEDs are used because they consume less energy compared to the conventional halogen bulbs previously used.

The most challenging aspect of high-brightness LED design is resolving EMI. Undesired noise signals generated at the high switching frequency of the LED driver can degrade circuit performance and in severe cases cause it to shut down. To address this, Maxim provides automotive LED controllers that deliver low EMI.

The MAX20090 is an LED driver for automotive front-facing lighting applications including high beam, low beam, daytime running lights, and fog lights. It operates with input voltages from 5V to 65V. Since it senses output current at the high side, it can protect against short circuits to ground or battery input at the output. Spread-spectrum modulation is available to reduce EMI noise, and it provides flexibility for external automotive lighting designs by using single/multi-channel boards to optimize the design.

The MAX20078 is a high-voltage synchronous n-channel MOSFET controller for high-current buck LED drivers. This product uses a proprietary average current-mode control method to regulate inductor current. With this control method, compensation of the control loop is not necessary even at a fixed switching frequency. The input voltage range is broad, from 4.5V to 65V, and no current measurement is required at high voltages. Switching frequency programming is possible from 100kHz to a maximum of 1MHz.

Additionally, it includes a 5V VCC regulator capable of delivering up to 10mA to external electrical circuits and features a current monitor function to monitor the proportionality between analog voltage and inductor current. It has inductor current limit protection, overvoltage protection, and thermal shutdown function, and at 3mm x 3mm size, it is advantageous for space-constrained applications.

Yin Wu, Business Director of Maxim's Automotive Division, stated, "The MAX20078 automotive LED controller is the only solution that combines the low switching noise of a hysteretic buck controller with a fixed-frequency buck controller."