| 摘要 |
PURPOSE:To obtain voltages having both polarities simultaneously by the ON, OFF control of not set of switching element, by a method wherein respective voltage converting means for obtaining positive and negative DC voltage upon putting the switching element OFF, are separated from each other electrically. CONSTITUTION:A voltage converting circuit 23 for obtaining a positive DC voltage and another voltage converting circuit 25 for obtaining a negative DC voltage are connected to a transistor TR21, putting a DC input ON or OFF in accordance with a control signal from a control circuit 29, in parallel. A diode 27 is inserted in order to separate the circuit 23 electrically from the circuit 25 when the transistor TR21 is put OFF. According to this constitution, a positive DC voltage V1 may be obtained from the circuit 23 in accordance with the time ratio of ON, OFF of the transistor TR21, the current of the coil 251 of the circuit 25 may be prevented from being conducted through the diode 231 when the transistor TR21 is OFF and the energy of the coil 251 is discharged to a capacitor 255 whereby a negative DC voltage V2 may be obtained from the circuit 25.
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