The increasing use of IoT devices and smart appliances has driven demand for compact and efficient power solutions. 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.
POC Video Tutorial
Table of Contents
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 PAM2305DGFAJ (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. Fig. 1 shows the module images. The Bill of Materials is listed in Table 1.
| Table 1: Bill of Materials | ||||||
| Name | Designator | Footprint | Quantity | Manufacturer Part | Manufacturer | Supplier Part |
| 10µF | C1, C2, C3, C4 | C0402 | 4 | CL05A106MP5NUNC | Samsung | C315248 |
| 100pF | C5 | C0201 | 1 | GRM0335C1E101JA01D | Murata | C76917 |
| 4.7µH | L1 | L0603 | 1 | CMH160808B4R7MT | FH | C394952 |
| WJ124-3.81-4P | P1 | CONN-TH_4P-P3.81_KF124-3.81-4P | 1 | WJ124-3.81-4P | Kangnex | C69809 |
| 500kΩ | R1 | RES-ADJ-SMD_3P-L3.8-W3.7_VGF39NCHXT | 1 | VGF39NCHXT-B504 | HDK | C22461638 |
| 120kΩ | R2 | R0201 | 1 | 0201WMF1203TEE | UNI-ROYAL | C270362 |
| AC-DC converter | U1 | PWRM-TH_LD05-23BXXR2 | 1 | LD05-23B05R2 | LZTEC | C42432360 |
| 2-pin connector | U2 | 2-PIN CONNECTOR | 1 | — | — | — |
| Buck converter | U3 | DFN-6_L2.0-W2.0-P0.65-BL-EP | 1 | PAM2305DGFADJ | Diodes | C780869 |
| 3.3V regulator | U4 | SOT-223 | 1 | ME6217C33M5G | MICRONE | C427602 |
AC-DC Converter 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.
The LD05-23B05SR2 module transforms an input voltage (85V-305V AC) into a stable 5V DC output. Compact and efficient, it is designed for low-power applications. The AC input is supplied through a 2-pin screw terminal (U2), connecting the live (L) and neutral (N) lines to the converter module (U1).
EFY PRIME subscribers get access to our BEST content, in an AD-free environment for readers who value faster and clutter-free reading experience.
If you're already an EFY PRIME subscriber, please login below. Else, please make a small investment by
CLICKING HERE and upgrade your level to access this and many more of such content.
