| 摘要 |
PURPOSE: To turn off a semiconductor element before another semiconductor element on the same arm starts to operate so as to prevent the breakage of the former by always monitoring the control signal which conducts the former even when such a state that the latter is set to a short-circuiting mode occurs. CONSTITUTION: Transistor drivers 9U and 9X are alternately turned on/off by means of turning on/off commands U and X. When the drivers 9U and 9X are alternately turned on/off, a short-circuiting mode detecting circuit 33 does not actuate a breaking circuit 34, because signals '1' are not simultaneously outputted from control signal detecting circuits 31 and 32. When the turning on/off command X is erroneously outputted and the transistor driver 9X is turned on, the short-circuiting mode detecting circuit 33 actuates the breaking circuit 34 so as to output a breaking signal (g), because signals '1' are simultaneously outputted from the control signal detecting circuits 31 and 32. The signal (g) is outputted until a signal '1' is outputted from a dead time detecting circuit and breaks the outputs to the drivers 9U and 9X. Therefore, the breakage of semiconductor elements 4U and 4X can be prevented by turning off the elements 4U and 4X. |
