1 Introduction

LED driver modules always contains batteries, LED drivers and LEDs. In auto market, most batteries are based on 12V systems and the voltage ranges from 9V to 16V. The output voltage ranges from 25V to 45V. Therefore, most LED drivers are using BOOST topology. Nowadays, more display modules are implemented in cars, such as cluster, center information display, rear seat display and head-up displays. The size of these displays becomes larger. This requires more LEDs integrated, which leads to higher output voltage. When the output voltage increases, it requires higher loop stability and system stability for the whole system.

Sometimes the customer can hear noise when the LED driver is running. The larger the output current, the louder the noise. The acoustic noise phenomenon observed in multi-layer ceramic capacitors (MLCCs) is primarily attributed to the piezoelectric effect inherent in ceramic materials. Owing to the distinctive multi-layer ceramic construction, MLCCs exhibit proportional mechanical stress variations when subjected to time-varying electric fields across the terminals. When the resultant vibration frequency falls within the human audible range (20Hz–20kHz), acoustic emissions manifest as acoustic noise.

The acoustic noise emitted by inductors primarily arises from magnetostriction: when subjected to high-frequency alternating currents, the core material undergoes periodic microscopic strain under the time-varying magnetic field, inducing mechanical vibration. This vibration couples with the surrounding structure and air, generating acoustic waves. This phenomenon, distinct from piezoelectricity, constitutes a parasitic magneto-mechanical energy conversion, commonly observed in circuits with pulsed currents such as an LED driver circuit.

Acoustic noise in LED drivers poses significant challenges in modern lighting systems. These issues arise from switching operations, magnetic components, and poor circuit design. Excessive noise not only compromises electromagnetic compatibility (EMC) but also degrades user experience and system reliability. To address these challenges, engineers must adopt a holistic approach combining schematic design and PCB layout optimization. This article explores strategies to mitigate noise at both stages, verifying compliance with industry standards and enhancing performance.

In summary, this application note is a design guide for users to decrease the noise on LED drivers.