| 摘要 |
PROBLEM TO BE SOLVED: To provide a current resonance circuit wherein a variable range of an oscillation frequency is not narrowed. SOLUTION: A current detection circuit 18 detects the magnitude of current which flows towards a connection between a first transistor 6 and a series circuit 26 via a second transistor 8, A comparator circuit 20 compares the magnitude of the current detected by the current detection circuit 18 with a reference value. When the current detected by the current detection circuit 18 is smaller than the reference value, an oscillation control circuit 16 controls the control current to be supplied to an oscillation circuit 4 to increase the oscillation frequency of the oscillation circuit 4 and prevent the oscillation frequency from becoming lower. Unlike the conventional design wherein the lowest oscillation frequency of the oscillation circuit is set, no margin is necessary in consideration of temperature characteristics and variations of components, and therefore a variable range of the oscillation frequency can be expanded.
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