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Two switch flyback (DC input version)


Flyback topologies are the most common and widely used topologies in auxiliary power supply design. Fly-back converter could be single phase as well as three phase types.  Fly- back is most commonly used due to its simplicity in design and control, less components, low cost solution, and built-in galvanic isolation.  
Two Switch Flyback helps to overcome the limitations of conventional flyback converter by splitting overall voltage stress equally between the two transistors. Two Switch Flyback is typically used for the power supplies >250W.


An overview of relevant components, power class and topologies is shown in below table.



Key Products

Product Category Product family Product Number Remark
Controller Quasi-Resonant control BD768xFJ-LB series SOP-J8, Low current consumption (19µA), during standby, Gate-clamp circuit
Gate Driver Isolated Gate Driver BM6105AFW-LBZ 2500V
BM61S41RFV-C 3750V
Discrete MOSFET SiC 4G 1200V SCT4062KR TO-3PFM, Rds_on= 62mΩ
SiC 4G 1200V SCT4062KE TO-268-2L, Rds_on= 62mΩ
SiC 4G 1200V SCT4062KW7 TO-263-7L; Rds_on= 62mΩ
Diode (D3)
Secondary Rectifier
Schottky Barrier Diodes RBQ /RBxx8 series Ultra low IR SBD is suitable for rectification purpose, RBxx8 series has wide range of voltage choise
Diode (D1,D2)
Primary VH or GND Clump
1200V RFS series (2 Piece series use) -


C-010. DC-DC Flyback Converter Vin=800V, Vo=25V, Io=10A

Related Topologies

Interleaved Boost PFC

Totem-Pole Bridgeless PFC (Diode Rectification)

Totem-Pole Bridgeless PFC (Synchronous FETs)