Automotive LED Matrix System Using a Four-Mode Buck–Boost Converter

Abstract

Automotive LED Matrix System Using a Four-Mode Buck–Boost Converter Jiho Moon Department of Electrical and Electronic Engineering The Graduate School Hanyang University The market for high-voltage power converters is experiencing rapid growth due to increasing demand. One of the fastest-growing sectors is automotive electronics, where efficient power conversion plays a crucial role in supplying power to automotive batteries. Automotive batteries undergo significant voltage variations, attributed to their role in car starters and load dump conditions. The voltage can swiftly surpass 100 V within seconds, but a clamped load-dump ensures the peak voltage remains below 40 – 60 V. Consequently, power converters for automotive applications need to be adeptly designed to accommodate an input voltage range of at least 40 – 60 V. This paper introduces a non-inverting buck–boost converter that utilizes the au- tomotive battery as a power source. The designed converter proves versatile for a broad spectrum of unidirectional power conversion applications, including but not limited to light-emitting diode (LED) headlights, navigation systems, and displays. The first research outlines a non-inverting buck–boost converter tailored for high- voltage automotive applications. This converter incorporates a newly devised con- troller chip along with four off-chip NMOS power transistors and two bootstrap capacitors. Unlike traditional non-inverting buck–boost converters, which typically operate in two modes (buck and boost), the converter in this research is engineered to seamlessly transition through four operation modes. This approach ensures a smoother shift between modes. In converters featuring four operation modes, the non-switching high-side power transistors necessitate continuous high gate-driving voltages, eliminating the need for bootstrapping operations. The designed non-inverting buck–boost converter employs a novel bootstrap-sharing technique to drive non-switching high-side NMOS transistors. Additionally, a ground- breaking current sensing technique is introduced, designed to operate reliably un- der high-voltage conditions. This current sensing method facilitates the modulation scheme of the converter, enabling current-programmed control. The second research outlines an LED matrix system designed for precise current regulation. In the realm of automotive technology, LED matrix headlights demand both high-power efficiency and stable control of individual LEDs. To address this, the proposed system integrates a buck–boost converter and a simultaneous current and voltage regulation circuit, enhancing overall efficiency. Notably, the system dis- tinguishes itself by requiring only a single small inductor, as opposed to the two large inductors found in alternative designs. The reference voltage for the buck–boost converter is dynamically generated based on the number of activated LEDs. Consequently, to achieve optimal current regula- tion for the LED matrix headlight, the output voltage of the buck–boost converter closely tracks the reference voltage. The primary control circuitry was manufactured on a chip using a 0.18-µm bipolar- CMOS-DMOS (BCD) process for functional testing, with a total chip area of 5.0 × 2.5 mm2, inclusive of bonding pads. The proposed system exhibits an operational input voltage range spanning 7 to 60 V, and an output voltage range varying from 1.05 to 60 V, contingent upon the number of activated LEDs. The implemented power system successfully demonstrated the ability to individually control LEDs for matrix headlights. Furthermore, a dimming test was conducted, confirming the system’s capability to precisely control the brightness of each LED.