Buck Converter With Merged Active Charge-Controlled Capacitive Attenuation

• Published in: IEEE transactions on power electronics Vol. 27; no. 3; pp. 1049 - 1054
• Main Authors: RADIC, Aleksandar, PRODIC, Aleksandar
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.03.2012; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; and small volume; Applied sciences; Attenuators; Capacitors; Circuit properties; Comparative analysis; Controllers; Convertors; Digital circuits; Digital control; Electric currents; Electric, optical and optoelectronic circuits; Electrical engineering. Electrical power engineering; Electrical machines; Electronic circuits; Electronics; Exact sciences and technology; Inductors; low-power switch-mode power supplies (SMPS); Power electronics, power supplies; Prototypes; Signal convertors; Steady-state; Switching loss; Transient analysis; Voltage control; Dynamic response; Input output; Power converter; Dynamic characteristic; Prototype; Control system; Power electronics; Topology; Experimental study; Algorithm; Inductor; Switching; Digital control; Step down convertor; low-power switch-mode power supplies (SMPS); Bypass; Output voltage; Attenuator; Slew rate; Electric loss; Capacitor; and small volume; Power semiconductor switches; Comparative study
• ISSN: 0885-8993; 1941-0107
• DOI: 10.1109/TPEL.2011.2171370

This letter introduces a converter and a complementary digital controller that, compared to conventional buck, have a smaller output filter volume, improved dynamic response, and lower switching losses. To reduce the volume and switching losses, the input-to-output voltage difference is decreased with a capacitive attenuator that replaces the input filter capacitor and has approximately the same volume. Both the attenuator and the downstream buck converter share the same set of switches, minimizing conduction losses. A single digital controller governs operation of the both stages. The controller utilizes the inductor current to regulate the center tap voltage, through a charge-control algorithm. During transients, the attenuator is bypassed, so the inductor current slew rate is improved. Experiments with a 5-1.5-V, 2.5-A, 1-MHz prototype show that, compared to the conventional buck, the merged topology has 43% smaller inductor, 36% smaller output capacitor, up to 30% lower power losses, and a 25% faster transient response.