a voltage transforming circuit comprises a constant - voltage regulator circuit for receiving a first voltage from a first voltage source and outputting a second voltage having the same polarity as the first voltage and a predetermined absolute value lower than the same , a step - up circuit , having a plurality of output terminals , for receiving the second voltage and a first synchronization signal , the step - up circuit stepping up the absolute value of the second voltage and controlling the operation of charging capacitors , thereby outputting from the output terminals a plurality of stepped - up voltages of the same polarity having absolute values higher than the second voltage , a level shifter circuit for receiving a second synchronization signal which uses the first voltage as one of logic levels , and receiving that one of the stepped - up voltages which has a highest absolute value higher than that of the first voltage , the level shifter circuit shifting the voltage of the one of logic levels to the highest absolute value of the stepped - up voltages , thereby creating the first synchronization signal , and a one - way conductive element connected between the first voltage source and that one of the output terminals of the step - up circuit from which the stepped - up voltage of the highest absolute value is output .