Low Input Current Ripple LLC Converter with Current Doubler Rectifier

• Main Authors: You-chen Kuo, 郭祐辰
• Other Authors: Ching-Shan Leu
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/32846773820794366626

碩士 === 國立臺灣科技大學 === 電機工程系 === 102 === The LLC converter has several advantages, such as zero-voltage switching on the MOSFETs and zero-current switching on the rectifier diodes from no load to full load conditions, high efficiency, high power density, low EMI. However, the LLC converter lacks an output inductor resulting in having large current ripple of the output capacitor. Thus, numerous capacitors have to be connected in parallel to reduce the output voltage ripple. It limits the power density performance. To reduce the output voltage ripple, current doubler rectifier technique has been proposed. It offers a current ripple cancellation mechanism and reduces the rectifier current ripple. To apply this technique, LLC converter can meet the output voltage ripple with a small number of the output capacitor. Therefore, the power density can be increased. The LLC converter with current double rectifier (LLC-CD) is thus proposed in Chapter 2. However, the input current of LLC-CD is pulsating and causes the EMI problems. In general, larger input filter is added to meet the EMI regulation. It limits the power density performance. To reduce the input current ripple, an input ripple cancellation mechanism can be applied to the LLC-CD and input current ripple reduction LLC-CD (RR-LLC-CD) is thus proposed in Chapter 3. To inherit the advantages of its predecessor, the RR-LLC-CD has an additional built-in input current ripple reduction function. As a result, the EMI regulation can be met by using smaller EMI filter components. Consequently, higher power density can be achieved. In addition to the descriptions of the operation principle, theoretical analysis, and design considerations, three hardware circuits, the LLC-CT, the LLC-CD, and the RR-LLC-CD, with 300-400-V input and 12-V/240-W output specification are built and tested to demonstrate their feasibility.