| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that it is difficult to balance the controllability between at a high output voltage and at a low output voltage in the case of the control of an output voltage by using a piezoelectric transformer, due to the difference of the amount of change in the output voltage per change of a unit frequency depending on frequency domains. <P>SOLUTION: A power supply device comprises: a piezoelectric transformer 208 for changing an output voltage at a frequency of a driving signal; an output voltage conversion circuit 207 for outputting a feedback signal proportional to the output voltage; a pulse output generator 450 for outputting a driving pulse at an average period proportional to an N-bit division ratio; a comparator 406 for comparing a target data value with the feedback signal; a data memory 460 for holding preset add/subtract data; and a calculator 405 for successively updating the division ratio by adding/subtracting the add/subtract data to/from the division ratio in response to the output of the comparison for each step. The calculator reads out the add/subtract data with defining data having predetermined M-bit (M<N) width extracted on the basis of the division ratio as an address for reading out, and calculates it so that a feedback data value comes close to the target data value. <P>COPYRIGHT: (C)2013,JPO&INPIT |
