在第二子模式（“低输出功率子模式”）中，使用脉冲宽度调制来调节VOUT，但转换器开关频率固定在第一频率。

In a second sub-mode ('low output power sub-mode'), VOUT is regulated using pulse width modulation, but the converter switching frequency is fixed at a first frequency.

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在某些实施例中，转换器具有第三子模式(“高输出功率子模式”)，其中使用脉冲宽度调制，但开关频率固定在第二频率。

In some embodiments, the converter has a third sub-mode (' high output power sub-mode '), in which pulse width modulation is used but the switching frequency is fixed at a second frequency.

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之后阐述了脉冲宽度调制和脉冲频率调制的工作原理。

Then the principle of Pulse Width Modulation and Pulse Frequency Modulation is analyzed in detail.

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