The DC1694A demonstration circuit is an isolated flyback converter featuring LT3748EMS device. The LT3748EMS is a switching regulator controller specifically designed for the isolated flyback topology and capable of high power. It drives a low side external N channel power MOSFET from an internally regulated 7V supply. The demo circuit is designed for a 12V output from a 22V to 75V DC input. The output current is up to 2.5A. The part senses the isolated output voltage directly from the primary side flyback waveform during the off time of the power switch. No third winding, optocoupler or signal transformer is required for regulation. A minimum load of approximately 2% of maximum load is required on the output to maintain regulation. The demo circuit can be easily modified for applications of different input and output voltage/current, with some pre designed transformers.
Switching frequency of 289KHz
86.5% efficiency
Boundary mode operation
Primary side winding feedback load regulation
VOUT set with two external resistors
INTVCC pin for control of gate driver voltage
Programmable soft start
Programmable undervoltage lockout
If higher operating voltage is required, power components with higher voltage ratings should be used.