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How do I convert AC to DC? Answered

I'm running a circuit using 24 volts DC and the power outlet in my country supplies 220 volts AC. What circuit does it?

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7 Replies

seandogue (author)2011-11-01

AC is converted to DC using a rectifier. However, usually, a transformer is used to both isolate the AC power source from the intended load and to reduce the line voltage to a more reasonable level for subsequent circuitry, prior to rectifying the AC. I would strongly recommend using a transformer. It can save your life.

Once that's done, it's fed through the rectifier (either a bridge of diodes or a single-piece semiconductor rectifier) to convert the lower voltage AC to a rough DC value (has a lot of ripple (fluctuating voltage) though, so it's then followed by smoothing circuitry like a capacitor and or inductor and or a resistor, then fed into a regulator for finer regulation of the desired output voltage.

yonch (author)2011-11-03

Thanks. Does it matter what diodes and transformer are used?

seandogue (author)2011-11-04

Well, of course it does. The diodes are selected for the expected load current, (and sometimes for the forward voltage drop) and the transformer for the input and output voltages, as well as the expected load current.

seandogue (author)2011-11-04

You'll want a 220VAC >> 30VDC transformer (the output needs to be a bit higher than the target voltage - 24V from your question, right? - to account for filtering), then size the transformer based on the expected current you want to pull (1A? 2A? 30A?)

A full wave rectifier will drop about 1.4 V from the output voltage of the transformer.

For load currents of 0- to about 0.75 A, 1N4001 diodes are fine for the purpose

if your current is larger than that, you'll need to check a catalogue for appropriate parts. (yes folks, I realize the 1N4001 is rated for 1A. Fully aware)

the rest is all based on what you're doing and how clean you need the power

Don't forget to apply a fuse or circuit breaker between power cord and the transformer

A Transformer ( Wire & Iron Magnetic Device ) lowers the AC Voltage then,
the Rectifier ( Four Diodes ) DC Bridge makes DC and
a Filter Capacitor Smooths out the ripples.
The first picture is called a ( TR Unit ).

yonch (author)2011-11-03

Thanks! Can you tell me the values of the components (capacitor and transformer)?

iceng (author)2011-11-03
• The transformer is a 220VAC to 16VAC
• Or a transformer is a 220VAC to 20VAC
• Four 1N4002 diodes
• An electrolytic capacitor 470 uF 50VDC