The non-synchronous flyback topology is widely used in isolated power supplies ranging from sub watt power levels to tens of watts. With more green-mode standards emerging around the world, improving light load efficiency and reducing no-load input standby current are more demanding than ever. Unfortunately, the traditional isolated power supplies using optocouplers can no longer achieve the performance requested.
The new LT®8300 builds a 5V/300mA low IQ isolated power supply from a 36V to 72V input with only five external components (input capacitor, output capacitor, transformer, feedback resistor and output diode). Without skimping any performance, the simple LT8300 solution achieves 85% peak efficiency, less than 250µA no-load input standby current, ±1% output load and line regulation, less than 50mV peak-to-peak output voltage ripple and well-behaved transient and startup performance.