고효율 및 소형 스위치모드 라인 트랜스포머

High Efficiency and Small Size Switch Mode Line Transformer(SMLT)

Abstract

A high-efficiency and small-sized switched-mode line transformer (SMLT) is proposed in this study. The conventional structure of an adapter is composed of line transformer and rectifiers. This structure has a limit in miniaturizing due to low-frequency line transformer. Another structure is composed of power factor correction (PFC) and DC/DC converter. This structure has a limit in reducing volume due to two-stage structure. As the proposed SMLT is composed of an LLC resonant converter, a high-frequency transformer can be adopted to achieve isolation standards and size reduction. This proposed structure has different operation modes in accordance with line input voltage to overcome poor line regulation. In addition, the proposed SMLT is applied to the front of a conventional PFC converter, because the SMLT output voltage is restored to rectified sinusoidal wave by using a full-bridge rectifier in the secondary side. The design of the PFC converter is easy, because the SMLT output voltage is controlled as rectified sinusoidal wave. The validity of the proposed converter is proven through a 350 W prototype.

Fig. 1. Conventional line transformer and adaptor.

Fig. 2. A proposed switch mode line transformer(SMLT).

Fig. 3. Frequency range for required output voltage according to input voltage.

Fig. 5. Input and output voltage detection of proposed SMLT.

Fig. 6. Design flow chart of resonant tank.

Fig. 7. Experimental wave form by input voltage.

Fig. 8. Comparison conventional PFC DC/DC converter and a proposed SMLT 350W prototype.

Fig. 4. Voltage gain according to input voltage.

Fig. 9. Experimental wave form of input voltage change.

Fig. 10. Efficiency of a proposed SMLT according to load condition.

TABLE I DIFFERENT TOPOLOGY OF PROPOSED SMLT ACCORDING TO INPUT VOLTAGE

TABLE Ⅱ CONTROL METHOD AND KEY WAVEFORM OF PROPOSED SMLT

TABLE Ⅲ SPECIFICATION AND COMPONENT OF A SMLT