Imagine that an electronics engineer is required to design a piece of equipment that is able to powered from the mains supply in both the USA and Europe. The problem is that the standard mains supply in the USA is 110V, 60Hz and in Europe it is 220-240V, 50Hz. The circuit presented here can be used on either mains system as long as a switch is set in the correct position. It has been known to happen for someone to plug in the rectifier circuit into the wrong voltage for the setting of the switch. In one case the circuit will probably still work when the switch is set to the correct position, while in the other case the probably be an explosion. Determine which case occurs for each of the switch positions? 

This circuit is a combination of the bridge rectifier circuit and the half wave voltage doubler circuit. The voltage doubler circuit is used to “double” the voltage produce from the 110V system, while the bridge rectifier is used for the 220-240V systems. 

With the switch being open, the circuit is connected as a bridge rectifier and the two capacitors are in series (acting like a single capacitor). The maximum DC output voltage is the same as the peak value of the supply. The supply current flows through the two opposite diodes, when the supply voltage is higher than the capacitor voltage. For a full explanation use the Bridge Rectifier Applet. 

With the switch being closed, the source is now directly connected to the mid point of the two capacitors. Current now only flows through one diode in this case. The output voltage is now twice that of the peak of the supply voltage. For a full explanation use the Voltage Doubler Applet.

• In the circuit, the time position (red line) on the waveform can be moved to see how the current path changes for each circuit.
• The value of the load resistor can be adjusted by dragging the red bar. Notice how the current waveform shape and ripple voltage changes.