Uploaded April 2023 | Updated September 2026, 3 weeks ago

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I'll try to explain how power supplies that can operated on worldwide voltage input 120V and 220V AC work.
- What does that Input Voltage Selector do?
- How does it work?
- How does automatic voltage selection work?

This only covers switch mode power supplies. For line frequency transformer based power supplies the voltage selector switch selected from different taps on the primary of the transformer.

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