MINIATURE AC-DC MODULE With Selectable Voltage

The increasing use of IoT devices and smart appliances has driven demand for compact and efficient power solutions.

- ASHWINI KUMAR SINHA

Traditional AC-DC converters tend to be bulky, fixed-voltage, and often inefficient. This module offers a compact AC-DC solution with over 75% efficiency and selectable output, ideal for IoT systems and small appliances.

The circuit comprises an AC-DC conversion stage followed by voltage regulation and selection. The LD05-23B05SR2 (U1) buck converter converts 85-264V AC to 5V DC, which is filtered by capacitors C1 and C2 (10µF each) to suppress noise. The AMS117-3.3 (U4) then steps down the 5V to 3.3V, which is then stabilised by capacitors C3 and C4. For adjustable output, the PAM-2305DGFAJ (U5) buck converter uses inductor L1, resistors R1 (500kΩ) and R2 (120kΩ), along with capacitor C5, to provide a tunable voltage. The resistor network enables output customisation, making the module adaptable for various applications.

The AC input is connected through a 2-pin connector (U2), ensuring a secure link to the power source. DC output is routed via the WJ124-3.81-4P (J1) connector, with additional solder pads for flexible integration into IoT systems. The Bill of Materials is listed in Table 1.

Circuit design

This circuit converts an AC input into a stable DC output with selectable voltage options, making it well-suited for IoT devices and small appliances. It consists of three main stages: the AC-DC converter, a 3.3V regulator circuit, and a variable resistor network for adjustable output. These are all integrated with a unified output connector for streamlined distribution.