Measurement of Optocoupler Parameters Current-mode Controlled Off-line Flyback Converter -Lee Seungjun-Kyungpook National University

Measurement of Optocoupler Parameters Current-mode Controlled Off-line Flyback Converter : 오프라인 플라이백 컨버터의 절연형 전류모드 제어를 위한 옵토커플러 파라미터 측정

 School of Electronics Engineering The Graduate School -Lee Seungjun-  December 2015 
The Graduate School Kyungpook National University Approved as a qualified thesis of Lee Seungjun for the degree of Master of Engineering by the Evaluation Committee December 2015 

 1. Introduction
Electronics manufacturers prefer power converters with low prices for price competitiveness. In addition, Switch Mode Power Supply (SMPS) in electronics should be isolated for safety reasons [1]. Flyback converters are widely used for off-line power supplies because they provide power stage isolation with minimal component counts. For this reason, flyback converters have long been widely used for SMPSs where the power-level is lower than 200 W. For isolation in feedback circuits, optocoupler isolation is commonly applied. Optocouplers deliver electrical signal between diode and phototransistor via infrared light. Optocouplers have many desirable features such as fast response and higher packing density. Most paper of current mode control have dealt with non-isolated feedback circuits. However, many designers require design information to implement isolated feedback circuits because electronic products that include DC-to-DC converters should be isolated perfectly. In this thesis, the peak current mode control is adopted to implement a feedback circuit, and it is isolated by an optocoupler. Compared with non-isolated feedback circuits, many things should be considered in order to design an isolated feedback circuit. In addition, because of the scarcity of research information, designing an isolated DC-to-DC converter is difficult. To resolve those problems, this thesis explains the optocoupler parameters applied to practical feedback circuits. 2 Chapter 2 introduces optocoupler for feedback isolation and their background for feedback design. In Chapter 3, the basic theory of flyback converter is provided in Continuous Conduction Mode(CCM). The purpose of this thesis is to provide fundamental and essential information that can be utilized to design an optocoupler isolated feedback circuit. The results of this thesis are demonstrated through PSIM / PSpice simulations and practical measurements.