Part # Application Notes General Purpose Products Lighting Control L6562 AN2435 datasheet

Part Manufacturer: ST Microelectronics

ST Microelectronics

Part Description: M sepic converter in PFC pre-regulator


Part Details:

AN2435 Application note TM sepic converter in PFC pre-regulator Introduction For the PFC (power factor correction) converter, sepic topology can be used when an output voltage lower than the maximum input voltage is required. This is instead of boost topology, which is unsuitable beacuse it must have an output voltage higher than the maximum input voltage. Sepic topology is advantageous because it allows the use of the ripple steering technique in order to reduce the switching frequency components of the input current without additional costs. This application note presents the basic equation of the sepic converter, in addition to design guidelines for a sepic PFC operating in transition mode and using the ripple steering technique. An application example with some tests results and waveforms is also provided in the document. Sepic converter March 2007 Rev 1 1/25 www.st.com Contents AN2435 Contents 1 Sepic topology for PFC converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Operation of the sepic converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.2 Sepic converter as a PFC circuit operating in transition mode [1.] . . . . . . . 6 1.3 Coupled inductor sepic converter and ripple steering . . . . . . . . . . . . . . . 10 1.4 Small signal model for a TM sepic converter . . . . . . . . . . . . . . . . . . . . . . 12 2 Practical design example of a sepic converter . . . . . . . . . . . . . . . . . . 13 2.1 Design specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.2 MOSFET (M1) selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.3 Diode D1 selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4 Capacitor C1 selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.5 Output capacitor C2 selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.6 Transformer design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.7 Selection of other components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3.1 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4 Board description and bench evaluation results . . . . . . . . . . . . . . . . . 18 4.1 Board description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2 Bench results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2/25


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Application Notes General Purpose Products Lighting Control L6562 AN2435.pdf Datasheet