Transformerless power supply
ajkumar-1907·power-converter-lib·transformerless-power-supply/transformerless-power-supply.kicad_pcb
About the Transformerless power supply PCB
Transformerless power supply is an open source PCB design by ajkumar-1907, published on GitHub under the MIT license. It is a 2-layer board measuring 48.8 × 37.5 mm, with 18 components from 12 distinct parts.
Other key parts include the LM7805_TO220. By type, the board carries 7 diodes, 4 capacitors, 4 resistors, 2 connectors and 1 IC.
It belongs with the iot & wireless and power & battery designs in this gallery.
From the project
Open-source library of power electronics converter topologies — KiCad schematics, working principles, use cases, and design notes for DC-DC, AC-DC, DC-AC, and AC-AC converters. Free to use, modify, and build on.
An AC-DC power supply that produces a regulated 5 V DC output directly from 230 V AC mains without a transformer. A high-voltage X-rated capacitor drops the voltage, a bridge rectifier converts it to DC, and an LM7805 regulates the output.
Transformerless (capacitive dropper) supplies are used where cost and size matter more than isolation: smart plugs, LED bulbs, small appliance controllers and energy meters. Instead of stepping the voltage down with a transformer, a capacitor in series with the mains limits the current. Because a capacitor's reactance dissipates almost no real power, this…

Main components on the Transformerless power supply
Transformerless power supply bill of materials (BOM)
18 components, 12 distinct parts.
| Qty | Part | Footprint | Refs |
|---|---|---|---|
| 1 | LM7805_TO220 | TO-220-3_Vertical | U1 |
| 2 | Screw_Terminal_01x02 | TerminalBlock_bornier-2_P5.08mm | J1, J2 |
| 4 | 1N4007 | D_DO-41_SOD81_P10.16mm_Horizontal | D1, D2, D3, D4 |
| 2 | D_Zener | D_A-405_P7.62mm_Horizontal | D5, D6 |
| 1 | LED | LED_D5.0mm | D7 |
| 1 | 0.1uf | C_Disc_D4.7mm_W2.5mm_P5.00mm | C1 |
| 1 | 1000uf | CP_Radial_D10.0mm_P5.00mm | C2 |
| 1 | 470uf | CP_Radial_D10.0mm_P3.80mm | C3 |
| 1 | 225k/2.2uF | C_Rect_L18.0mm_W6.0mm_P15.00mm_FKS3_FKP3 | C4 |
| 2 | 20k | R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R1, R2 |
| 1 | 1M | R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R3 |
| 1 | 2.2k | R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R4 |
Transformerless power supply design files
The KiCad project lives in the ajkumar-1907/power-converter-lib repository on GitHub; these links point at the commit this page was built from.
Transformerless power supply: common questions
How big is the Transformerless power supply PCB?
The Transformerless power supply measures 48.8 × 37.5 mm, has 2 copper layers and is 1.6 mm thick.
How many components are on the Transformerless power supply?
18 components, from 12 distinct parts. The full bill of materials is listed on this page.
Where can I download the Transformerless power supply design files?
From the ajkumar-1907/power-converter-lib repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.
Can I use the Transformerless power supply design in my own project?
Yes, under the terms of its MIT license, which ajkumar-1907 chose for the repository.
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