無光反激拓撲簡化了隔離DC/DC變換器的設計

　　除了被用在電信和數(shù)據(jù)通信系統(tǒng)中，直流輸出也在許多其他噪聲敏感的應用如汽車蓄電池的充電要求，中間總線電壓為各種電子負載，和工業(yè)品。雖然反激拓撲是流行的隔離DC / DC轉換器應用，由于它相對簡單和成本較低的替代孤立的拓撲結構，設計傳統(tǒng)的反激式是不容易的，因為變壓器需要精心設計，環(huán)補償可以是復雜的。此外，它需要一個光耦或額外的變壓器繞組反饋輸出電壓從二次側，以維持輸出精度。

　　光耦合器的傳輸延遲、老化和增益變化使復環(huán)補償和反激變換器的穩(wěn)定性復雜化，同時限制了變換器的瞬態(tài)響應。此外，光耦合器消耗功率，增加電源的成本和物理尺寸。設計一個高性能變壓器與額外的繞組可以采取大量的時間，因為有一個有限的選擇現(xiàn)成的變壓器。最后，使用一個額外的繞組增加了變壓器的物理尺寸和成本。

　　Fortunately， recent advances in power conversion technology have made low-power isolated converters much easier to design. By incorporating a primary-side sensing scheme and running the converter in boundary mode， Linear Technology’s no-opto flyback converters， such as the LT3574 and LT8300， simplify the design of flyback converters by eliminating the need for an opto-coupler， external MOSFET， secondary-side reference voltage， and extra transformer winding. Its boundary mode， which is a variable-frequency， current-mode， control switching scheme （more on this shortly）， also results in improved regulation over the full line， load， and temperature ranges. According to Linear， boundary mode also permits the use of a smaller transformer compared to equivalent continuous conduction mode （CCM） designs. These flyback solutions are popular in isolated power supplies ranging from less than a watt to tens of watts.