Reference design for a 350 W power supply with monitoring capability
This reference described the unique synchronous bridge rectifier, the interleaved PFC stage, the high-speed phase-shifted full-bridge converter and the monitoring capability enabled by a MSP430 microcontroller for a 350-W, state-ofthe-art power supply. Each building block can be used separately and is easy scalable to higher power levels. You can easily synchronize several converters to the same switching frequency using digital isolators.
This project is a complete 350W, high performance, high speed offline power supply solution. It contains a novel, microcontroller-driven synchronous bridge rectifier, a 2-phase interleaved PFC stage and a phase-shifted fullbridge as down converter. It has an universal input (85 .. 265V AC) and the output voltage is adjustable between 12 and 14V. The continuous output current is 25A, the peak current is 27A. A second microcontroller monitors several values (input voltage, PFC voltage, output voltage, output current, temperatures), is the interface to the user (LCD, push-buttons), adjusts the output voltage and synchronizes the switching frequency of all converters.
Using synchronous rectification on the full bridge and placing the controller on the secondary side enable a bandwidth and load response far better than the potential of a standard converter that uses an optocoupler for the feedback path, even with much more output capacitance.
Features
- Fanless & ultraslim, heigth 45mm
- Efficiency +93% at high line (plug-to-plug)
2-Phase interleaved PFC with UCC28070:
- Continuous conduction mode for low noise operation (PFC scalable to bigger power levels)
- MSP430 controlled PFC bridge rectifier (Value Line MSP430F2012)
Synchronous Phase Shifted Fullbridge with UCC28950:
- Controller on secondary side to avoid low pass behavior of optocoupler
Total System Monitoring & Control by MSP430F2252:
- AC input voltage & intermediate PFC voltage via isolated I2C-interface
- Output voltage & current
- Temperature of left/right heat sink and case temperature
- Output voltage is adjustable between 12 and 14V with a resolution of 100mV
- All controllers are synchronized by µC; switching frequency could be adjusted for “out of RF band operation”
µC is able to vary the switching frequency, too (“Dithering”)
This reference design has been tested by Texas Instruments. It comes with required design resources such as Gerber files, schematics, BoM, etc. You can find additional data about the reference design on the company’s website. To read more about this reference design click here.
