Which device is used to convert AC voltage to DC voltage?

The device that converts alternating current (AC) voltage to direct current (DC) voltage is a rectifier. Rectifiers achieve this by allowing current to flow in only one direction, effectively "clipping" the negative portion of the AC waveform. This process often involves the use of diodes, which serve as one-way valves for electricity. The output is then often smoothed using filters to produce a more stable DC voltage.

Transformers, on the other hand, are used to change the voltage level of AC electricity but do not convert AC to DC. Inverters serve the opposite function; they convert DC back to AC, making them essential in systems that require AC power from a DC source, such as solar panels. Capacitors store and release electrical energy but do not serve the function of converting AC to DC. Therefore, the rectifier is the correct choice for this question, as it directly fulfills the requirement of converting AC voltage to DC voltage.