| 摘要 |
PROBLEM TO BE SOLVED: To provide a clock oscillating circuit which can maintain a duty ratio to be a prescribed value when transmission of negative feedback is performed by an electrically insulated device. SOLUTION: The clock oscillating circuit is provided with a photocoupler 11 for transmitting an input signal to the post-stage while insulating the signal, a first and a second current mirror circuits 12, 13 which are connected with a positive pole side output and a negative pole side output of the photocoupler, respectively; a first and a second switching elements 14, 15 connected with the respective output ends of the current mirror circuits 12, 13 wherein output ends and input ends of the switching elements are mutually connected, and a main oscillating circuit 16 which has an integrating circuit wherein an inverter 25 and a capacitor C1 are connected in parallel with an input side and produces a timing signal. The output ends and the input ends of the switching elements 14, 15 are connected with an input end of the main oscillating circuit 16, and driving ends of the switching elements 14, 15 are connected with an output end of the main oscillating circuit 16.
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