Most modern chargers can go into any output across the world. I believe this is because of low powered "Switch mode" technology it uses rather than transformers, like they used to.

To go from high AC to low DC is pretty easy now.

But my main question is about other products that may use a motor. Is it possible to design a circuit that regardless of the input (110v or 240v 50/60hz) it can function the same way without a toggle switch?

  • 1
    \$\begingroup\$ Switch mode power supplies still use transformers. \$\endgroup\$ – Andy aka Oct 7 '15 at 9:29
  • \$\begingroup\$ (+1) Ooops... I'm trying to figur eout why old chargers (10 years ago) would only work on certain input AC but now, almost any charger can be plugged into any (AC, being 110v or 240v) output. \$\endgroup\$ – BBking Oct 7 '15 at 22:18
  • \$\begingroup\$ Stick to the geetar dude LOL. \$\endgroup\$ – Andy aka Oct 7 '15 at 22:29
  • \$\begingroup\$ @Andy aka LOLZ!! I know it might sound strange, but I actually have a diploma in electronics. Things are made so easy these days I'm just trying to figure out what is the difference between a device being able to be plugged into any across the world and not getting blown up to something that will get blown up! I'm happy to reword my question. \$\endgroup\$ – BBking Oct 26 '15 at 6:05

Switch mode power supplied that you find with phones etc. do still use transformers.

An old fashion large wall wart that runs the transformer at 50Hz (or 60Hz) to drop the voltage, these are large and bulky, plus have no brains so the output voltage is dependent directly on the input voltage and the number of turns. 60Hz through a 50Hz transformer at high load can also cause heating problems due to reactive power.

Switch mode supplies rectify mains AC to DC, then turn that into a high frequency AC (10kHz-50kHz or so) which is then dropped down using a small transformer. The higher the frequency, the smaller the transformer can be made (though the power capacity is also limited). These also support multiple voltages by using a feedback network (usually optically isolated) which adjusts either the frequency or duty cycle of the high frequency AC to result in constant output voltage regardless (within reason) of the input. In fact this is why sometimes you can hear them humming at high frequency when not connected to anything.

With motors, it depends on the type of motor. If it is a DC motor that runs at less than the lower 110V mains, you can use a similar technique with SMPS to regulate the rectified mains down to the correct voltage (frequency and voltage then don't matter).

If it is an AC motor, then you may have issues - especially if it needs to run at a specific RPM which will be governed by the mains frequency, and voltage. Now there are solutions to this. One that springs to mind is to use an inverter - basically the mains is rectified to DC to remove the frequency issue, and then an inverter is used to convert that back to a sine (ish?) wave of the correct frequency. With motors the inverter can also regulate the voltage using PWM because the inductance of the motor will filter away the PWM signal leaving a fairly constant amplitude sine wave (though again that only works if the motor is rated for <=110V).

| improve this answer | |

Not the answer you're looking for? Browse other questions tagged or ask your own question.