The evaluation circuit EVAL-ADPL54203-AZ is a micropower no-opto isolated flyback converter featuring the ADPL54203. This demo circuit outputs 5V and maintains tight regulation with a load current from 10mA to 2.2A over an input voltage from 10V to 28V. The output current capability increases with the input voltage. The ADPL54203 typically needs less than 0.5% of its full output power as a minimum load to maintain good output voltage regulation. On the EVAL-ADPL54203-AZ, to avoid pre-loading, a 5.6V Zener diode is placed between its VOUT+ and VOUT– to serve as a minimum load. Transformer leakage inductance causes a voltage spike on the primary side after the power switch turns off. To limit this leakage inductance spike within MOSFET voltage rating of 60V, an RC snubber and a TVS clamp are installed to damp the ringing and clamp the MOSFET drain voltage to a safe level.
The Performance Summary table summarizes the performance of the demo board at room temperature. The demo circuit can be easily modified for different applications with some predesigned transformers.
The ADPL54203 is a simple to use monolithic micropower isolated flyback converter. By sampling the isolated output voltage directly from the primary-side flyback waveform, the part requires no third winding or opto-isolator for regulation. The output voltage is programmed with two external resistors and a third optional temperature compensation resistor. By integrating the loop compensation and soft-start inside, the part reduces the number of external components. Boundary mode operation provides a small magnetic solution with excellent load regulation. Low ripple Burst Mode® operation maintains high efficiency at light load while minimizing the output voltage ripple. A 3.4A, 60V DMOS power switch is integrated along with all the high voltage circuitry and control logic into a thermally enhanced 8-lead SO package.
The ADPL54203 data sheet gives a complete description of the part, operation and application information and must be consulted with this quick start guide for evaluation circuit EVAL-ADPL54203-AZ.
Design files for this circuit board are available at Product Evaluation Boards and Kits | Design Center | Analog Devices.
