A high-frequency digitally controlled LED driver for automotive applications with fast dimming capabilities

This paper presents a high-frequency, digitally controlled High-Brightness LED driver for automotive applications with fast dimming capabilities. The power converter is based on the magnetically coupled Ć uk topology employing a single off-the-shelf SMT mutual inductor. The proposed digital control technique exploits the inherent stabilizing effect of magnetic coupling, and combines it with a dedicated duty-cycle feedforward technique for step-reference response enhancement during dimming operation. No direct sensing of the LED string current is performed, bypassing the disadvantage of the Ć uk topology of having an inverted output polarity. Furthermore, the magnetically coupled Ć uk topology is a single-switch solution and it provides inherent filtering of the input and output currents without introducing additional magnetic elements, strongly reducing the total required capacitance and maintaining the small form-factor required in the automotive environment. The paper discusses the theoretical and practical development of the proposed controller. Experimental tests on a 40 W, 1 A, 500 kHz prototype indicate a 0 to 1 A current rise time in the tens of microseconds time frame with excellent damping characteristics and regulation accuracy.