| 摘要 |
PROBLEM TO BE SOLVED: To simplify filters that are provided at input and output sides of a DC-DC converter by removing poor reception of a car radio. SOLUTION: A DC-DC converter is mounted on a car and converts the voltage of a first DC power supply into the voltage of a second DC power supply. When the difference between AM broadcasting frequency receivable by the car radio mounted on the car and a neighboring broadcast frequency is 10 kHz, the switching frequency of the DC-DC converter is set to 135 kHz. Also, when the difference between the AM broadcast waves and the neighboring broadcast frequency is 9 kHz, the switching frequency of the DC-DC converter is set to 9 kHz×(n+0.5) (where n is a positive integer), 139.5 kHz, for example. These switching frequencies are created by reducing a quartz oscillating frequency gradually.
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