基于NCP1380驱动的准谐振适配器设计

Quasi.square wave resonant converters also known as Quasi.Resonant (QR) converter are widely used in the adaptor

market. They allow designing flyback Switched.Mode Power Supply (SMPS) with reduced Electro.MagneTIc 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.