Demonstration circuit 2793A is a high VIN no-opto synchronous flyback converter featuring the LT8316. The demo board outputs 5V and maintains tight regulation with a load current from 70mA to 7A. It is optimized to operate over a wide 140V to 450V DC input voltage range. Output voltage accuracy stays within ±5% over the entire input voltage and load range.
On the secondary side, the LT8309 synchronous rectifier driver senses the synchronous MOSFET drain-to-source voltage to determine its turn-on period. By replacing the diode rectifier with an N-Channel MOSFET, the efficiency and thermal performance is greatly improved.
The LT8316 is a 600V flyback controller. No opto-isolator is needed for regulation. The part samples the output voltage from the isolated flyback waveform appearing across a third winding on the transformer. Quasi-resonant boundary mode operation improves load regulation. At start-up, the INTVCC capacitor is charged via a high voltage current source; during normal operation, the current source turns off to save power consumption.
DC2793A features an option to turn on standby mode by simply changing the position of a jumper from “DIS” to “EN”. Standby mode reduces the minimum switching frequency to 220Hz for ultralow quiescent power consumption.
The LT8316 and LT8309 data sheets give a complete description of the parts, and operation and application information. The data sheets must be read in conjunction with this quick start guide for demo circuit 2793A.
