| 摘要 |
PURPOSE:To certainly prevent the erroneous operation when the primary coil is in electric conduction by the condenser in a feedback circuit, by installing a precharge circuit for charging a feedback condenser only during the time when an output transistor does not conduct. CONSTITUTION:During the time when an output transistor 17 does not conduct because of the output of a wave-form shaping circuit 2 due to a precharge circuit 50, a transistor 55 is in OFF-state, and a condenser 15 is charged by the forward-direction voltage corresponding to two diodes which is the result of the subtraction of the forward-direction voltage drop portion of a diode 56 from the forward-direction voltage drop portion of the diodes 57-59 corresponding to VBE of the output transistor 17. At the moment when the output transistor 17 is put into electric conduction, charging electric current does not flow into the condenser 15 through a resistor 11, and the input for an electric-current detecting circuit 30 has the wave form as shown in the figure, and the erroneous operation due to the whisker-shaped voltage can be avoided.
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