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Many micro USB phone chargers give 5V DC and 1500 mA output at input 100-240 V AC at 50-60 Hz (these values are from a Sony EP 880 charger). What happens to the output when voltage rises above 240 and when it falls below 100? What happens when the input is not 50-60 Hz? What happens to the battery and it's circuitry ?

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    \$\begingroup\$ What happens when you use anything outside of its design limits? \$\endgroup\$ – Roger Rowland Mar 12 '15 at 12:27
  • \$\begingroup\$ What happens when you eat too much red meat? You know the health suffers but don't you want to knowhow high the cholesterol gets? \$\endgroup\$ – Ranbir Mar 12 '15 at 12:53
  • \$\begingroup\$ I think the phrase "undefined behaviour" would be the most generic answer. As far as I'm concerned there's no such concept as "too much red meat" ;-) \$\endgroup\$ – Roger Rowland Mar 12 '15 at 12:54
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Usually those ranges are the optimum ranges, which also have an extra allowance or a safety factor(around 1.2-1.5x), say upto 300V. Beyond that exactly that will happen if you run it over the design limits like Roger said. It will probably burn the regulator or other internal components.

Most likely, it will burn the immediate component in contact with the input voltage, and sometimes careful design will have say a fuse/or some other safety design which will protect the rest of the circuit and components, and only burn the fuse.

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  • \$\begingroup\$ So for a good design the damage doesn't even reach the phone so the question about the battery doesn't even arise? \$\endgroup\$ – Ranbir Mar 12 '15 at 12:58
  • \$\begingroup\$ Yes, Overall a transformer is used at the input which steps down the voltage(by a factor of around 20). The voltage from that is regulated by a Regulator(7805's), and that has a wide range itself. For extra protection there is also something used to limit the output current to the battery, and this protects the battery. \$\endgroup\$ – Sherby Mar 12 '15 at 13:38

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