A Current Balancing Scheme With High Luminous Efficacy for High-Power LED Lighting

• Published in: IEEE transactions on power electronics Vol. 29; no. 6; pp. 2649 - 2654
• Main Authors: Xiaohui Qu, Siu-Chung Wong, Tse, Chi K.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-06-2014; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Buses; Capacitors; Current balancing; dimming; Electric currents; Electric potential; Electrical engineering. Electrical power engineering; Electrical machines; Electronics; Exact sciences and technology; Feedback control systems; Fundamental areas of phenomenology (including applications); high-power LEDs; Light emitting diodes; Lighting; Lighting systems; Luminosity; Luminous efficacy; Miscellaneous; Modulation; Optical sources and standards; Optics; Optimization; Optoelectronic devices; Physics; Pulse width modulation; Regulation and control; Regulators; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Strings; Switches; Unity; Various equipment and components; Voltage; Voltage control; high-power LEDs; LED lamps; Balancing; Superheating; Feedback system; Current balancing; Lighting fitting; Control system; luminous efficacy; Unbalanced conditions; Verification; Failures; Implementation; Light emitting diode; Bus system; Degradation; dimming; High power; Optimal control; Voltage; Optoelectronic device; Optimal planning; Pulse duration modulation; Damaging
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2013.2288632

The imbalance in the currents of strings of LEDs will cause fast degradation or even failure in some LEDs. Such current imbalance should be avoided. To balance the common average current, a small duty cycle may necessitate a large LED turn-on current amplitude, which may cause temporal overheat and low luminous efficacy of the LEDs. This paper presents a current balancing method based on pulse-width modulation of a common bus voltage to each LED string to achieve the intended average current. An optimal feedback control scheme is proposed to maximize the duty cycles and minimize the bus voltage. As a result, at least one of the LED strings is operating at unity duty cycle. The analysis, implementation, and verification are detailed in this paper.