| 摘要 |
PURPOSE:To reduce the output ripple voltage and to prevent the occurrence of abnormal voltage, by connecting capacitors in parallel to the second stage filter choke coils in a switching power device cascadely connected in two stages of filters. CONSTITUTION:The DC output is switched by a switching transistor Q, the voltage of which is transformed by a transformer T. The output on the secondary side is rectified by diodes D1 and D2 and is smoothed by the two stage filter coils composed of choke coils L1 and L2 at the back stage and capacitors C1 and C2. A capacitor C3 is connected to the choke coil L2 comprising the second stage filter circuit. With this composition, the ripple voltage across the capacitors C2 comprising the first stage filter circuit is divided by the added capacitor C3 and output impedance, which is added to the ripple voltage waveform of the capacitor C2 when there is no capacitor C3 and the output ripple voltage gets reduced eventually.
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