| 摘要 |
The inventive bi-directional DC-DC converter addresses a problem of an insufficient step-up ratio during the step-up operation that is caused when a turns ratio of the transformer is determined to, for example, match the step-up operation and also address a contrary problem of an insufficient step-down ratio during the step-down operation that is caused when a turns ratio is determined to match the step-up operation. In the inventive bi-directional DC-DC converter that uses a transformer for both step-down and step-up operations, a switching frequency for operating a switching device is set separately for the step-down and step-up operations. For example, when the switching frequency during the step-up operation is lower than the switching frequency during the step-down operation, the range in which the duty ratio in PWM control can be controlled is widened, compensating for step-up ratio insufficiency. Conversely, step-down ratio insufficiency is compensated for by making the switching frequency during the step-down operation lower than the switching frequency during the step-up operation.
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