A power supply converts AC (Alternating Current) from the mains into DC (Direct Current) that electronic circuits and industrial devices can use. Most electronic components — like sensors, controllers, and PLCs — require a steady DC voltage, typically 24V DC, while the power source from the wall is 230V AC. The conversion from AC to DC happens through several stages inside the power supply: rectification, filtering, and voltage regulation.
1. Rectification:
The first step uses diodes arranged in a bridge rectifier circuit to convert the alternating current into a pulsating DC. In AC, the voltage constantly changes direction, but diodes allow current to flow only in one direction, effectively removing the negative half of the waveform and creating a unidirectional output.
2. Filtering:
After rectification, the DC voltage still contains ripples or fluctuations. To smooth this out, the power supply uses capacitors (and sometimes inductors) as filters. These components store and release electrical energy, filling in the gaps in the waveform and providing a more stable DC output.
3. Regulation:
Finally, the voltage passes through a voltage regulator — either linear or switching — which ensures the output remains constant even if the input voltage or load changes. In modern systems, this is done by an SMPS (Switched-Mode Power Supply) circuit, which is compact, efficient, and reliable for industrial use.
In simple terms, a power supply converts AC to DC by first turning AC into pulsating DC (rectification), then smoothing it (filtering), and finally stabilizing it (regulation). This ensures a clean and reliable DC voltage output that powers controllers, PLCs, and sensors in automation systems safely and efficiently.