| 摘要 |
PURPOSE:To effectively protect a microcomputer, etc., by controlling the output voltage of a second power source circuit when an output voltage from the second power source rises over a set value as compared with the output voltage of a first power source circuit. CONSTITUTION:A second power source voltage VM is inputted to the non- inverting input terminal of an operational amplifier 221, a predetermined voltage VR is inputted to the non-inverting terminal of an operational amplifier 222, and the voltages VM, VR are differentially amplified. Accordingly, an output VO from the amplifier 221 becomes VO=2(VM-VR). Since a first power source voltage VS is inputted to the non-inverting input terminal of a comparator 223, the output of the comparator 223 is set to an L level in case of (VM-VR)> VS. An output signal from the comparator 223 controls the base of a transistor 144 of the second power source 14 to control to reduce the output voltage form the power source 14. |
