DESIGN OF A DUAL-INPUT SERIAL DC-DC CONVERTER REALIZING INDIVIDUAL SWITCHING MODES
To drive a white light-emitting diode (LED) in portable devices, a dual-input serial DC-DC converter realizing individual switching modes is proposed in this paper. Unlike conventional single-input converters, the proposed converter provides output voltage by converting not only battery energy but also solar energy. Therefore, the proposed converter can suppress energy consumption of a battery. Furthermore, in the proposed converter, the -1/mx stepped-down voltage (m = 1, 2, ... , N) is generated to drive LED's cathode only when the voltage of solar-cells is insufficient to drive 1x transfer mode. In other words, when the voltage of solar-cells is sufficient to drive LEDs, the proposed converter is in standby mode. For this reason, the proposed converter can realize high power efficiency, because energy loss caused by the power conversion is suppressed. The properties of the proposed converter are clarified by theoretical analyses. Furthermore, SPICE simulations and experiments show the validity of circuit design, where theoretical results correspond well with SPICE simulated results. For this reason, derived theoretical formulas can provide basic information to design negative switched capacitors (SC) DC-DC converters. The proposed converter will be useful as a driver circuit of white LEDs for display backlighting.
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