| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply device that can maintain the high efficiency of a piezoelectric transformer and the induction heating (IH), even if an input voltage varies widely. <P>SOLUTION: An alternating voltage of a predetermined frequency converted from a DC power source voltage by a drive circuit 13 is supplied to an electric element. An input voltage monitoring circuit 16 generates an optimum control signal, based on the changed portion of a voltage input to the electric element and the frequency component of a feedback voltage with regard to a voltage raised and output at the electric element. Because this optimum control signal adjusts the DC power source voltage so that the ON/OFF of a step-down chopper circuit 15 becomes a predetermined duty ratio, the characteristics of the electric element is controlled so as to become an optimum value. Even if the input voltage varies widely, therefore, the high efficiency of the piezoelectric transformer 10 can be maintained and electric power can stably be supplied. <P>COPYRIGHT: (C)2007,JPO&INPIT |
