| 摘要 |
PROBLEM TO BE SOLVED: To provide power saving for a device and relax thermal design conditions by reducing the electric power loss of sub output easily and with a low-cost configuration. SOLUTION: This power supply unit is provided with a plurality of extension lines fitted on a transformer winding for sub output, a sub output switching part 1 formed with a switch on the extension line, an operating mode detection part 3, and a control part for controlling the sub output switching part 1, based on a signal from the operating mode detection part 3 and regulating the input voltage of a three-terminal regulator, thereby reducing the power loss of the sub output.
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