| 摘要 |
PROBLEM TO BE SOLVED: To provide a DC-DC converter that suppresses a frequency band of noise from expanding while sustaining a constant output voltage.SOLUTION: When boosting an input voltage, voltage boosting operation or first voltage boosting/dropping operation which boosts less input voltages than the voltage boosting operation is performed. When dropping the input voltage, voltage dropping operation or second voltage boosting/dropping operation which drops less input voltages than the voltage dropping operation is performed. When the voltage boosting operation is transferred to the first voltage boosting/dropping operation, on-time of a voltage boosting switch is temporarily increased, and when the second voltage boosting/dropping operation is transferred to the voltage dropping operation, off-time of a voltage dropping switch is temporarily reduced. This prevents undershoot from being generated in an output voltage. When the voltage dropping operation is transferred to the second voltage boosting/dropping operation, off-time of a voltage dropping switch is temporarily increased, and when the first voltage boosting/dropping operation is transferred to the voltage boosting operation, on-time of the voltage boosting switch is temporarily reduced. This prevents overshoot from being generated in the output voltage.SELECTED DRAWING: Figure 4 |
