Most battery chargers for laptops, digital cameras and other consumer electronics are able to support Input Voltages of 110 ~ 240VAC. The size of these chargers are usually pretty small compared to voltage transformers from “Newstar” or “Super”.
How does those battery chargers detect what is the input voltage and then converts them to their suitable operating voltages in such a small size?
Best answer about How battery charger switch between 110 and 240 VAC?
Answer by Mark
Mark here. Small Power Adaptor Working..
240V ac in, Into transformer primary winding, voltage lowers and moves down into secondary transformer winding, is then rectified by four rectifiers making a (Bridge Rectifier.) Smoothed by capacitors, and then output to either 15V DC 12V DC . 9V DC, etc.
Chargers use a small but high spec mains transformer, 240V AC mains in. stepped down,the lower output voltage is rectified and it’s final output voltage is controlled by an electronic component called a Voltage Regulator. Regulating it’s desired output voltage.
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The smaller lighter chargers use switch mode power supplies (SMPS) which are smaller and lighter than their linear counterparts as they use either smaller transformers or no transformers at all. There are dedicated SMPS control chips that detect the input voltage from a bridge rectifier and regulate the rest of the circuit accordingly to output the correct voltage whatever the input within the specified 110V/220V range.
They don’t switch between 110/240V modes really.
A typical switch mode PSU circuit has a feedback loop between the voltage regulator (typically a TL431 or its ilk) on the low voltage side, and the oscillator on the mains side. The action of the TL431 through the feedback loop sets the width of the oscillator signal, which drives the drive transistor.
With that, a 240V source will create higher voltage pulses on the secondary, which the feed back will keep shorter, to make the designed output voltage.
A 120V source will create lower voltage pulses on the secondary, which the feedback look will allow to be longer, to get the same voltage as needed.