300W Phase Shift Full Bridge DC-DC with Synchronous Rectification – Reference Design
The RD024-RGUIDE-03 reference design from Toshiba Electronic Devices and Storage Corp. describes the specifications, operating procedure, and efficiency characteristics of a 300W isolated dc-dc converter. This converter operates over an input voltage range of 36- to 75-Vdc and provides 300W power at 12Vdc output.
This design is suitable for various applications, including telecommunication equipment with 48VDC lines and industrial systems powered by 48V batteries. This reference design provides various design information, which help to reduce the time and effort to design a dc-dc converter according to actual required specifications.
This converter uses Toshiba's latest small surface-mount power MOSFETs as switching devices and small surface-mount components for other types of devices on both the primary and secondary sides. Consequently, despite the use of a general-purpose winding transformer, small PCB size (82mm x 82mm) and high efficiency (94%) are achieved.
Simplified block diagram. (click on image to enlarge)
The winding transformer simplifies design as a basis for actual applications and helps to constitute a power supply circuit on PCB instead of using an external power supply module.
Efficiency curves (click on image to enlarge)
100V MOSFET Power Switches
The TPN1200APL low voltage N-channel power MOSFET products (U-MOSⅨ-H series) used in this reference design are 100V products suitable for power supplies for industrial equipment.
Fabricated with the companyʼs latest low voltage U-MOSⅨ-H trench process, which optimizes the device structure, the TPN1200APL has an on-resistance of 11.5 mΩ. In addition, the input capacitance (Ciss, typical) is 1425pF and the total gate charge (Qg, typical with VGS = 10V) is 24nC.
Synchronous Rectifier Switches
This reference design employs the TPH3R70APL low-voltage N-channel 100V power MOSFETs (U-MOSⅨ-H series) as the synchronous rectification switches. The TPH3R70APL RDS(ON) = 3.7mΩ (max) @ VGS = 10V. In addition, the input capacitance (Ciss, typical) is 4850pF and the total gate charge (Qg, typical with VGS = 10V) is 67nC.
