THESIS
2004
xii, 76 leaves : ill. ; 30 cm
Abstract
High-efficiency voltage-mode DC-DC power converters are currently in great demand for portable electronic devices. Converter stability can be easily achieved by dominant-pole frequency compensation with a single large compensation capacitor at error-amplifier output. This significantly simplifies design effort and reduces cost of off-chip passive components. However, dynamic response of these converters is limited and is not sufficiently fast for digital systems which need converters with fast tracking speed for adaptive power-supply applications. As a result, voltage-mode converters which require complex compensation RC networks or current-mode converters that require advanced inductor-current sensing circuits are usually needed. Nevertheless, both approaches are not perfect solutions...[
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High-efficiency voltage-mode DC-DC power converters are currently in great demand for portable electronic devices. Converter stability can be easily achieved by dominant-pole frequency compensation with a single large compensation capacitor at error-amplifier output. This significantly simplifies design effort and reduces cost of off-chip passive components. However, dynamic response of these converters is limited and is not sufficiently fast for digital systems which need converters with fast tracking speed for adaptive power-supply applications. As a result, voltage-mode converters which require complex compensation RC networks or current-mode converters that require advanced inductor-current sensing circuits are usually needed. Nevertheless, both approaches are not perfect solutions as extra design effort has to be made for different LC combinations.
In this thesis, a simple but efficient voltage-mode control scheme, End-Point Prediction (EPP), is proposed. The internal nodal voltages of the controller are predicted and set automatically by the proposed algorithms and circuitries. Therefore, the settling time of the converter can be significantly reduced for fast dynamic responses, even a large compensation capacitor is used.
The proposed scheme has been applied to a voltage-mode buck converter, which has been implemented in AMS 0.35-μm CMOS technology. The chip area is 1100um x 2000um. The designed buck converter is able to operate at switching frequency of 500kHz to 1MHz, and the supply voltage is from 1.8V to 3.3V. From the measurement results, the tracking speed of the buck converter using EPP is faster than the conventional one by 6 times. The power-conversion efficiency is 86% at 180mA.
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