| 摘要 |
PURPOSE:To discriminate an input voltage surely, by connecting a charging circuit in parallel with a switching circuit included in a level discriminator, in a switching regulator changing the rectifying system automatically. CONSTITUTION:At the time immediately after an input voltage is applied to an input discriminating circuit 6, the charging of capacitors C3, C4 has not been finished, the phase of the input voltage is not clear, and the peak voltage can not be detected in advance. In connecting a capacitor C6 in parallel with a transistor TR2, when an AC input is applied to input terminals T1, T2, a charging current flows to the capacitor C6 via a resistor R5 and a TR3 of a switching circuit 5 is closed. Thus, the rectifying system is taken as the full-wave rectifier system until the charging of the capacitor C6 is finished. Thus, while a level discriminator 7 completes the discrimination of the input voltage, the full-wave rectifier system is used for the safety. |
