NCP1380EVB/D Performances of a Quasi-Resonant Adapter Driven by the NCP1380
●Interference (EMI) signature and improved efficiency. However, as the switching frequency of QR converter increases as the load decreases, the frequency must be limited.In traditional QR converter, the frequency is limited by a frequency clamp. But, when the switching frequency of the system reaches the frequency clamp limit, valley jumping occurs: the controller hesitates between two valleys resulting in an unstable operation and noise in the transformer at medium and light output loads.
●In order to overcome this problem, the NCP1380 features a “valley lockout” circuit: the switching frequency is decreased step by step by changing valley as the load decreases. Once the controller selects a valley, it stays locked in this valley until the output power changes significantly. This technique extends the QR operation of the system towards lighter loads without degrading the efficiency.
●This application note focuses on the experimental results of an adapter driven by the NCP1380.
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a Quasi-Resonant Adapter 、 Quasi−square wave resonant converters |
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Datasheet |
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Please see the document for details |
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English Chinese Chinese and English Japanese |
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December, 2009 |
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Rev. 1 |
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595 KB |
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