LED Brake/Tail Light Controller Design

Upasana Dewan

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LEDs find state-of-the-art applications in automotive rear lighting such as brake lights (or stop lights) and tail lights. Apart from benefits such as very long life, extreme vibration resistance and shallower packaging compared to bulbs, LEDs also offer a safety benefit in stop lights by responding around 250 milliseconds faster than incandescent bulbs when power is applied.

Many times, same set of LEDs illuminate both tail lights and brake lights. This requires LEDs to operate at two different brightness levels, where brake lights operate at full brightness and tail lights are dimmed to 10% to 25% of that brightness. Pulse-width modulation (PWM) is the best method to achieve dimming. The PWM function can be integrated on a LED-driver IC to simplify the driver design by eliminating the need for an external PWM signal. Automotive applications take advantage of added features of LED driver ICs such as scalability, diagnostic functions of open and short LED, temperature monitoring, low cost, and other mandatory features for driving LEDs in harsh automotive conditions.

Some industry-grade reference designs of LED drivers for Rear lighting control in automobiles are given below with complete documentation. Take a look!

HB LED-Driver for Automotive Rear Lighting: 

maxim led driverThis LED-driver reference design from Maxim integrated for automotive rear lighting (STOP and TAIL) is implemented with a linear LED-driver IC MAX16804 requiring a minimum of external components. The brightness of LEDs is controlled by PWM, implemented within the IC. The IC delivers a 200 Hz drive signal to the LEDs to produce required tail-light brightness. More on this Reference Design

LED Brake/Turn Light Design: 

This reference design is a cost-effective solution for LED Brake/Turn Lights without utilizing a MCU or software. Instead, the design utilizes a TLC6C5912 shift register LED driver operated by two 555 timers integrated in the TLC556 device. The design integrates several features such as thermal Shutdown protection and flexibility in number of LEDs used. The design can also withstand automotive cold crank conditions. Provided along with the design are schematics, design files, BOM and applicable datasheets. More on this Reference Design

Vehicle Tail Lamp and Brake Lamp Controller: 

This design shows a way to use the same LED array for both taillights and brake lights. The brightness of the LED is controlled by a simple switch, allowing dim lighting while running and bright lighting while braking. The design includes an AD8240 LED Driver/Monitor, PNP pass transistor, and PWM generator. The AD8240 provides cost-effective LED lamp monitoring and short-circuit protection. The PWM generator, which consists of two 555 timers. The PWM signal controls the LED brightness. More on this Reference Design

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