Quasi-resonant switching converter

　　The hard switching method and the full resonant switching strategy have been studied. Both have advantages and disadvantages. The more important advantages and disadvantages will be summarized below.

　　The power adapter manufacturer (Jiuqi Industry) has studied the quasi-resonant switching method, which can eliminate some of the shortcomings of the above two methods and retain most of the advantages. Before starting, you should summarize the advantages and disadvantages of the above two methods.

　　Hard switching method

　　Disadvantage

　　(1) Inherent high switching loss.

　　(2) Too fast switching edges cause EMI noise in a wide frequency spectrum.

　　(3) Need to adopt load line shaping technology

　　(4) The transient power stress in the switching device is too high.

　　(5) The reverse recovery current in the switching diode is too large

　　(6) The range of operating frequency is limited (due to high switching loss)

　　Advantages of 5 volt power adapter

　　(1) Very mature technology and many proven topologies. Related books and application notes are abundant, and a complete range of control 1C is available for selection

　　(2) It can adapt to a wide range of input and load changes.

　　(3) Non-resonant circuit, so the current in the wire-wound components and switching devices is smaller, and the 1R loss is also small.

　　(4) Easy to understand and design.

　　(5) The layout and design of winding components are not particularly critical

　　Fully Resonant Method

　　Disadvantage

　　(1) Large reactive currents in wire-wound components, capacitors and semiconductors

　　(2) Design is more difficult

　　(3) More sensitive to changes in load and input.

　　advantage

　　(1) Due to zero voltage or zero current switching, the switching loss is smaller.

　　(2) Since there are few high-frequency harmonics, EM1 and RF1 are reduced.

　　The Brazilian certified power adapter manufacturer (Jiuqi Industry) will study how a quasi-resonant system overcomes the various shortcomings of hard switching and full-resonant switching, while retaining most of the advantages.

　　There are a variety of quasi-resonant systems that have been applied, but in essence they all maintain the efficiency of the switching device at a high level through zero-voltage or zero-current switching. In addition, the excessive copper loss caused by the excessive reactive current in the fully resonant system is much smaller in the quasi-resonant system. This is because the resonance process is limited to the turn-on or turn-off period of the power device, which only accounts for the entire switching waveform. a small part.

　　The 10kW converter introduced by the power adapter manufacturer (Jiuqi Industry) goes a step further, effectively using some parasitic components and some components that are generally considered undesirable (such as MOSFET substrate capacitance, transformer leakage inductance and distributed capacitance) . These components are utilized and become part of the quasi-resonant circuit. Therefore, parasitic elements are no longer a problem, in fact they help to achieve zero voltage switching.

　　Now let us study the primary side power part of a 10kW quasi-resonant power converter. This converter is designed and manufactured by my company, and its performance has been proven in industrial applications.

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