Each of the quasi resonant flyback operating modes discussed above has its strength and weaknesses. It is up to the designer to which mode to select. In my personal experience, I already used both the DCM and TM operating modes. Basically, a quasi resonant flyback will operate in DCM at light load and approaches to TM at very heavy load. During the design stage, the designer will set the operating point in first valley switching for heavier loads for optimum performance.
A quasi resonant flyback converter is a variant of flyback converter wherein it makes use of the parasitic elements to partially resemble a resonance action. According to dictionary, the word quasi could mean partly, partially, comparatively or relatively. So, a quasi-resonance means a partial resonance, not a total resonance. At light load, Quasi resonant flyback operation will be in DCM. However, it will come closer to the boundary or transition mode while in full load.
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A flyback converter is composed of a flyback transformer, switch, rectifier and filter and the control mechanism to drive the switch and provide regulation. It is a low part count switching converter and relatively easy to make or design. A flyback converter is an isolated switching converter that can be a step down or step up configuration. Most cell phone, tablets and laptop chargers are made from flyback converter. Following topics will discuss how flyback converter works.
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