| 摘要 |
PROBLEM TO BE SOLVED: To prevent over-voltage of output voltage by using a main switch transistor and a transistor for synchronous rectification as an over-voltage protective circuit for reduction in the number of constituent parts when output voltage is in an over-voltage condition. SOLUTION: When the output voltage of a DC-DC converter is in an over- voltage condition, a main switch transistor Tr1 is turned off forcibly, and the transistor Tr2 for synchronous rectification is turned on forcibly. As a result, a signal line 26, the transistor Tr2 for synchronous rectification, a signal line 2, a signal line 1 and a choke coil L1, a signal line 15, a resistor R1, and a signal line 16 are connected to clamp the output voltage of the DC-DC converter to the voltage(OV) of the ground connected with the signal line 26. It is thus possible to prevent over-voltage from being applied to the load of the DC-DC converter. It is further possible to provide reduction in the number of constituent parts because of the elimination of a fuse for preventing them from being burned. |
