| 摘要 |
PROBLEM TO BE SOLVED: To cope with battery switching to a commercial power source voltage by the selection of parts alone. SOLUTION: A DC voltage formed by rectifying and smoothing a stepped down commercial AC voltage through a rectifier Recl and a smoothing capacitor C4 is divided through resistors R9, R10. The series body of a field effect transistor FET1 as second switch element and a resistor R3 is connected to the capacitor C4 via a resistor R2 and a reverse current prevention diode D1. The middle point of the FET1 and the R3 is connected to a transistor Tr2 as first switch element. Both ends voltage of a resistor R10 is input to the gate of the FET1. When the commercial AC voltage drops, the both ends voltage of the R10 lowers so that the FET1 is turned off, the Tr2 is turned on, and a fluorescent lamp FL is lighted on. When a drive voltage turning on-off the FET1 is selected by the R9 and the R10, the switching of a battery can be arbitrarily set. |
