Abstract: The boost type power supplies are widely used in portable consumer electronics to step up the input voltage to adapt for the high voltage applications like light-emitting diode (LED) driving and liquid crystal display (LCD) biasing. In these applications, a regulator with small volume, fewer external components and high efficiency is highly desired. This paper proposes a projected off- and on-time boost control scheme, based on which a monolithic IC with an on-chip VDMOS with 0.2 Ω on-state resistance R_DS-ON was implemented in 1.5 μm bipolar-CMOS-DMOS (BCD) process. A 12 V, 0.3 A boost regulator prototype is presented as well. With projected off-time and modulated on-time in continuous conduction mode (CCM), a quasi fixed frequency, which is preferred for ripple control, is realized. With projected on-time and modulated off-time in discontinuous conduction mode (DCM), pulse frequency modulation (PFM) operation, which is beneficial to light load efficiency improvement, is achieved without extra control circuitry. Measurement results show that an efficiency of 3% higher than that of a conventional method under 0.5 W output is achieved while a step load transient response comparable to that of current mode control is maintained as well.

Key words: Boost regulator, Integrated circuits, Pulse frequency modulation, Projected off-time, Projected on-time

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