4 connected in series for dividing the voltage from the smoother 40 and a microcomputer 61 for comparing the divided voltage from the third and fourth resistors r 3 and r 4 to a reference voltage to determine whether the utility power 10 is equal to 110v or 220v to fix operation of the smoothing operation selector 70 according to a result of the determination the smoothing operation selector 70 which is preferably a switching device connected between a common contact point of the first and second capacitors c 1 and c 2 in the smoother 40 and an output terminal on the rectifier 30 has a relay 71 for operating as a voltage doubler to provide 311v when an 110v is suppled to the utility power source 10 the operation of the automatic voltage conversion module in accordance with a preferred embodiment of the present invention will be explained fig3 illustrates waveforms for explaining operation of an automatic voltage conversion module in accordance with a preferred embodiment of the present invention when the user turns on the power switch 20 to put the washing machine into operation as shown in fig3 a the utility power source 10 provides a sinusoidal ac power to the rectifier 30 the rectifier 30 rectifies the ac power and the smoother 40 smooths the rectified ac power and provides to the motor driver 50 at a moment the above operation is made the voltage sensor 60 divides a voltage of the power through the third and fourth resistors r 3 and.