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| Title: | An auto-selectable-frequency pulse-width modulator for buck converters with improved light-load efficiency |
| Authors: | Man, Tsz Yin
Mok, Philip
Chan, Mansun |
| Keywords: | Switching convertors
Auto-selectable-frequency pulse-width modulation
Light-load efficiency |
| Issue Date: | 2008 |
| Citation: | Proceedings IEEE International Solid-State Circuits Conference, 2008. ISSCC 2008. Digest of Technical Papers. San Francisco, USA, p. 440-441, 626 |
| Abstract: | In order to be useful for mobile systems, the switching frequencies of modern buck converters (BCs) are in the MHz- or even GHzrange to enable the use of compact off-chip inductors and capacitors [1], or even on-chip Ls and Cs [2]. However, such high switching frequencies increase both the switching loss and the gate-drive loss, and degrade BC light-load efficiency since these losses are independent of load current. Pulse-frequency modulation (PFM) is known to improve light-load efficiency by scaling the switching frequency with the load current so that the switching loss and the gate-drive loss are reduced with decreased load current. However, PFM makes the BC output spectrum change with the load current. This unpredictable spectrum causes supplyintegrity to be an issue in mobile systems where different spectrum-sensitive circuits, such as communication ICs, are often used. Recently, the light-load efficiency of BCs operating at a constant switching frequency in MHz range have been improved [3, 4]. However, the methods used only reduce the gate-drive loss, which is the power required to switch the power PMOS and NMOS transistors (MP and MN in Fig. 24.4.1), but not the switching loss, which is the power needed to switch the switching node (VX in Fig. 24.4.1). BC light-load efficiency can only be greatly improved when these two losses are simultaneously reduced. |
| Rights: | © 2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. |
| URI: | http://hdl.handle.net/1783.1/3268 |
| Appears in Collections: | ECE Conference Papers
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