| 摘要 |
PURPOSE:To improve the follow-up adaptability to the voltage fluctuation as well as to reduce the calorific value of a transistor, by providing the first and second resistance in a snubber circuit and by suppressing the spike voltage and ringing voltage by means of these resistance. CONSTITUTION:A switching power circuit comprises a switching transistor Tr, a snubber circuit S and a transformer with the primary and secondare coils L1 and L2. As the snubber circuit a diode D1, the first resistance R1 and a capacitor C1 are connected in series, while the second resistance R2 is connected in parallel to the serial circuit of the first resistance R1 and a diode D1. The spike voltage, set up when the switching transistor Tr is turned OFF, is effectively damped by the first resistance R1 and the diode d1. The ringing voltage is sufficiently suppressed by the second resistance R2.
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