A very simple and useful switching power supply circuit can be constructed using the TOP204 switching controller integrated circuit manufactured by Power Integrations IN .
This TOP204 switching power supply circuit diagram can be very useful for applications that don’t need a huge power .
The design of the switching power supply using the TOP204 IC is not so complicate , an require few external components , making it ideally for compact power sources .
The TOP204 circuit is a part from the TOPSwitch family controllers that implements, with only three pins, all functions necessary for an off-line switched mode control system: high voltage N-channel power MOSFET with controlled turn-on gate driver, voltage mode PWM controller with integrated 100 kHz oscillator, high voltage start-up bias circuit, bandgap derived reference, bias shunt regulator/error amplifier for loop compensation and fault protection circuitry.
The switching power supply circuit shown in this figure is a highly accurate 15 V, 30 W secondary regulated flyback power supply that will operate from with a wide range of input voltage from 85 to 265 VAC . A TL431 shunt regulator directly senses and accurately regulates the output voltage. The output voltage of the circuit can be fine tuned by adjusting the resistor divider formed by R4 and R5. Also other output voltages are possible by adjusting the transformer turns ratios as well as the divider ratio.
More details about the T1 transformer construction can be found in TOPSwitch® Flyback Transformer Construction Guide from the Power Integrations .