Industry Focus: Automotive
Delivering enhanced automotive user experience and safety through innovative lighting
By Vincent Wang, VP of sales and marketing, Asia, indie Semiconductor F
, with the strongest growth coming from interior and side lighting. There are many reasons behind the adoption and rapid growth of LED lighting in automobiles. Compact size allows deployment in small spaces (such as inside the cabin) and reduces vehicle weight which improves economy / range. At the same time, the higher brightness and flexibility offered by multi-LED lighting supports innovative designs for comfort, experience and road safety. Externally, applications that previously relied on traditional bulbs have moved to LED, including headlights, tail / brake lights and direction indicators. Inside the vehicle, LED lighting is used for basic utility lighting, but the fastest growing sector is the use of LEDs and devices such as lossy light guides to enhance both the UX and the automaker’s branding.
rom adaptive vehicle headlamps to customizable interior lighting, availability of compact, low-energy, high-brightness LEDs provides automakers with innovative new ways to improve road safety and enhance user experience (UX) for drivers and passengers. As a result, the market for automotive LEDs is expected to double from $16 billion in 2021 to over $32 billion by 20311
LEDs: Drive and control Irrespective of whether they are used externally or internally, all LEDs need to take a drive current from a voltage source that is higher than the device operating voltage. Furthermore, in the case of matrix-based arrays for headlamps there is the need for circuitry to provide pixel-level control. This drive and control circuitry must take up minimum space, use the minimum number of components and operate with high efficiency
16 November 2023
levels over the vehicle’s lifetime without interfering with or being susceptible to interference from other vehicle electronics. Primary options for driving LEDs are either a linear (non-switching) driver or a switching DC-DC power supply that is, in almost every case, a step-down buck converter. Conversion efficiency is a primary consideration for a number of reasons. Inefficiency implies generation of heat due to losses and, even if there is space to include cooling mechanisms, these will add to the weight and cost of the vehicle. If the power conversion is inefficient current to the LED can be reduced, but this means lower brightness.
Components in Electronics
Electromagnetic Interference (EMI) is a common concern in automotive applications and lighting systems must not be susceptible otherwise erratic behavior is a likely outcome. Similarly, they should not generate EMI, otherwise nearby circuits (which may include safety critical circuits) could be adversely affected.
Linear versus switch mode Linear conversion for LEDs in automotive applications can often dissipate more energy as heat than is used by the LED. For example, if a 12 V rail is converted to drive a 3 V LED drawing 20mA, then the heat
dissipated will be 180mW ((12 V – 3 V) * 20mA). While this may be acceptable for a single LED, the losses will soon mount up in a multi-LED application.
The alternate approach uses switch-mode power supplies (SMPS) that are commonly based upon ‘buck’ DC-DC converters that step the voltage down efficiently. This is a simple, non-isolated, topology built around an efficient solid-state switch (typically a MOSFET) and a few additional components. The output voltage is close to that needed by the LED and driver (c.4.5 V) and, with a conversion efficiency that typically exceeds 85 per cent, losses are far lower.
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