| 摘要 |
PURPOSE:To prevent back flow of current by comparing the level between an input DC voltage and a stabilized output voltage so as to turn off an MOS transistor (TR) subject to on/off control by the output when the input DC voltage is the stabilized output voltage or below. CONSTITUTION:A constant voltage circuit 11 outputs a DC output voltage Vout stabilized from an input voltage VIN. In case of VIN>Vout, a high level voltage is applied to a gate of the MOS TR15, which is turned on and a prescribed level of the stabilized voltage is outputted. On the other hand, in case of VIN>= Vout, the MOS TR is turned off so as to prevent the electric charge charged in a capacitor 7 from flowing to the input power supply thereby supplying a backup current by the capacitor 7 only to a load 6. |
