Overvoltage protection system with AC/DC and DC/DC converters

摘要

An overvoltage-protective device is provided for protecting a power system (2) from overvoltage non-destructively without using a fuse. An alarm signal from an MOS transistor (Tr3), a structural element of a DC/DC converter (21), is inputted to a switching circuit (55), a structural element of an AC/DC converter (11). In case an alarm signal keeps high-level potential without indicating overvoltage-state, the switching circuit (55) connects an output current detecting circuit (53) having a gain G1 to an output voltage detecting circuit (50) as well as a feedback circuit (51A), thereby to set large output-power-supply capability. In case an alarm signal inverses to low-level potential indicating overvoltage-state, the switching circuit (55) connects an output current detecting circuit (54) having a gain G2, larger than the gain G1, to the output voltage detecting circuit (50) as well as the feedback circuit (51A), thereby to set small output-power-supply capability. Thus, overvoltage at the DC/DC converter (21) can be avoided. IMAGE