A Scalable <italic>N</italic>-Color LED Driver Using Single Inductor Multiple Current Output Topology

Abstract

Constant current sources are required to drive multiple color LED strings and the LED drivers that drive these LED lighting systems should provide multiple constant currents from a single DC source. In this work, a Single Inductor Multiple Current Output (SIMCO) converter that can provide Nindependently controllable constant current outputs is reported. The average current in each color LED string is controlled independently by using Hybrid Average Current Mode Control (HACMC). The HACMC combines the advantage of both average current mode control and charge control method. Traditional dimming approaches such as PWM and Analog dimming can be incorporated in the proposed topology for color tunability and Correlated Color Temperature (CCT) control. The proposed approach uses a simple control logic, which is modular and can be scalable to N color LED lighting systems. The operation of the SIMCO converter with the HACMC is explained in detail. Simulation and experimental results with 48V input and 12W for N=3 (RGB) color systems are presented.

Investigation Into the Use of Single Inductor for Driving Multiple Series-Connected LED Channels

“…Various techniques utilizing different kinds of sensors, including current sensors [10]- [14], thermal sensors [15]- [16], and optical sensors [17]- [20], have been proposed to regulate the light output. Reference [21] uses both thermal and optical sensors.…”

“…To reduce the form factor of the driver, some techniques utilize single inductor to manage currents of N parallel-connected LED channels [10]- [14]. They are typically extended from the concept of single-inductor-multiple-output (SIMO) power conversion methods [22]- [25], which are usually used to deliver multiple output voltages.…”

“…The first one has all LED channels activated sequentially in every switching cycle [10]. The second one has only one LED channel activated in each switching cycle [11]- [14]. The channels are activated sequentially over the switching cycles.…”

“…Multiple current sensors [11], [14], one for each LED channel, are required to regulate the average channel current. In [10], [12]- [13], only one sensing resistor is needed.…”

Precise Color Control of Red-Green-Blue Light-Emitting Diode Systems

“…This is redundancy in three independent converter control circuits in the power supplies [6]. To resolve the redundacy issue, a single-inductor multiple-outputs converter topology has been rcently proposed for driving single or multiple color LED strings in order to reduce the form factor and increase the power density [7] [8]. The performance of RGB LED systems, such as illumination intensity and color, is determined by the luminous ratio of RGB colors.…”