Dc-Dc Converter Design for Battery-Operated Systems
DC-DC Converter Design for Battery-Operated Systems
Harry Arbetter. Robert Erickson. and Dragan Maksimovid
Power Electronics Group Department of Electrical and Computer Engineering University of Colorado, Boulder, CO 80309-0425 USA
Abstrurt - This paper describes performance, design and optimization of de-dc converters for energy limited, battery operated systems. Variable-frequency operation is used to achieve voltage regulation and high efficiency for an extremely wide range of load currents. An experimental 15W, 3.3V buck converter has been constructed to demonstrate design and optimization techniques. The converter employs synchronous rectification to reduce conduction losses, and discontinuous, variable-frequency, current-mode control with optimum peak current to maximize efficiency for a wide range o f loads. Applications include portable computers, hand-held instruments, and telecommunications.
1. INTRODUCTION
Energy limited, battery powered systems require the utmost in efficiency in order to provide full system capability and maximum battery life. The use of low voltage power supplies (3.3 volts or less) can reduce power consumption at the expense of lower noise margins and a requirement for better voltage regulation. Elements which require high instantaneous power. such as transmitters. microprocessors, backlit displays, and flash memory, can be switched to a low power standby mode when not needed. Applications include portable computers, hand-held instruments. and wireless telecommunications. To fully realize such systems, dc-dc converters are needed which can: (a) regulate the load voltage with (ideally) zero load current; (b) operate at high efficiency with many orders of magnitude variation in the load current; (c) operate efficiently at low output voltages (3.3 volts or less). Losses in a switch-mode converter can be classified as: loud dependent conduction losses (due to transistor onresistance, diode forward voltage drop, inductor
Harry Arbetter. Robert Erickson. and Dragan Maksimovid
Power Electronics Group Department of Electrical and Computer Engineering University of Colorado, Boulder, CO 80309-0425 USA
Abstrurt - This paper describes performance, design and optimization of de-dc converters for energy limited, battery operated systems. Variable-frequency operation is used to achieve voltage regulation and high efficiency for an extremely wide range of load currents. An experimental 15W, 3.3V buck converter has been constructed to demonstrate design and optimization techniques. The converter employs synchronous rectification to reduce conduction losses, and discontinuous, variable-frequency, current-mode control with optimum peak current to maximize efficiency for a wide range o f loads. Applications include portable computers, hand-held instruments, and telecommunications.
1. INTRODUCTION
Energy limited, battery powered systems require the utmost in efficiency in order to provide full system capability and maximum battery life. The use of low voltage power supplies (3.3 volts or less) can reduce power consumption at the expense of lower noise margins and a requirement for better voltage regulation. Elements which require high instantaneous power. such as transmitters. microprocessors, backlit displays, and flash memory, can be switched to a low power standby mode when not needed. Applications include portable computers, hand-held instruments. and wireless telecommunications. To fully realize such systems, dc-dc converters are needed which can: (a) regulate the load voltage with (ideally) zero load current; (b) operate at high efficiency with many orders of magnitude variation in the load current; (c) operate efficiently at low output voltages (3.3 volts or less). Losses in a switch-mode converter can be classified as: loud dependent conduction losses (due to transistor onresistance, diode forward voltage drop, inductor
References: B.Huffman, R. Flatness, " Power conversion from milliamps to amps at ultra-high effiency (up to 95%), "Linear Technology, Apllication Note 54. March 1993. 121 "Battery management and dc-dc converter circuit collection - a power supply application guide for portable equipment." MAXIM Integrated Products. 1994. 131 A.C Wang, S.R.Sanders. "Programmed pulsewidth modulator waveforms for electromagnetic interference mitigation in DC-DC converters." IEEE Trans. on Power Electronics, Vo1.8. No 4. Oct.93, pp.596605 [I] Fig. 13 Unmodulated switching frequency spectrum of the output voltage Fig. 14. Modulated switching frequency spectrum of the output voltage. 109