| 摘要 |
A DC-to-DC converter generates a plurality of power outputs at different voltages using a single inductor 33 and an arrangement of switches A to F enabling the input voltage to be connected to the inductor 33 in both forward and reverse directions. Power is supplied to an output during an inductor charge phase in which current flows from the input supply through the inductor to the power output, followed by an inductor discharge phase in which current flows from ground through the inductor to the power output, the current in the inductor at the end of the inductor discharge phase is detected and stored, and, before the next inductor charge phase for the same output, a slew phase is provided in which the input supply is connected across the inductor in either the forward or reverse direction, to alter the inductor current at the beginning of the inductor charge phase to be equal to the inductor current at the end of the previous discharge phase for that respective output. The inductor current can be regulated rapidly, enabling the converter to supply current to an output whose voltage is close to the input voltage. This arrangement reduces crosstalk between power outputs, and enables the converter to supply outputs having different power requirements. Preferably, the total length of time (slew phase plus inductor charge phase plus inductor discharge phase) for each power output is the same, which reduces the variable frequency noise generated by the converter. The converter may be used in portable devices such as an MP3 audio device (fig 2) which can receive power from a battery or from a computer USB connection (fig 1). |
