| 摘要 |
PURPOSE: To protect the abnormal operations of switching devices, more particularly, the abnormal operations of switching devices in an upper side arm securely and quickly. CONSTITUTION: Overvoltage detection/protection circuits (12a)-(12c) and (14a)-(14c) detect the voltages of the controlled electrodes of switching devices Qa1-Qc1 and Qa2-Qc2 and control the inputs to the controlled electrodes. The switching devices Qa2-Qc2 in an lower side arm are simultaneously protected by the overvoltage detection/protection circuits (14a)-(14c) added to them. The detection signals of the overvoltage detection/protection circuits (14a)-(14c) and an overcurrent protection circuit (16) are inputted to a control circuit (24) through a driver (18), a photocoupler PC0 and a buffer (22) and discontinue the pulse inputs to the controlled electrodes of the switching devices Qa1-Qc1 and Qa2-Qc2. As the abnormalities are judged by the voltage abnormalities of the controlled electrodes of the switching devices Qa1-Qc1 and Qa2-Qc2, the secure and quick protection can be realized. |
