| 摘要 |
PURPOSE:To reduce voltage variation for a load to ensure semipermanent lifetime of the switching operation by turning on a second transistor when an output voltage of the power supply circuit has exceeded a constant voltage of a constant voltage element and then turning off a first transistor when the second transistor turns on. CONSTITUTION:When the commercial voltage VAC fails and thereby an output voltage of the power supply circuit falls below a constant voltage value of a constant voltage element ZD, a second transistor TR2 turns off. When the second transistor TR2-34 turns off a first transistor TR1 turns on, supplying the power to a load from the secondary battery E. Moreover, when the commercial voltage VAC recovers and an AC output voltage of the power supply circuit 1 exceeds a constant voltage of the constant voltage element ZD, the second transistor TR2 turns on. When the second transistor TR2 turns on, the first transistor TR1 turns off, suspending power supply to the load from the secondary battery E. Thereby, voltage variation for the load can be reduced and lifetime of the switching operation can be extended semipermanently. |
