| 摘要 |
PURPOSE:To allow prorection of a switching element against heating by allowing a comparator to be switched to a prohibition signal having such level as allowing chopping control of the switching element. CONSTITUTION:When high current drive operation is desired, switching is made to output a prohibition signal Vint using a current value setting means 30. Since the levels of coil current corresponding detection signals Vac, Vbd never exceed the level of the prohibition signal Vint, comparators 25ac, 25bd are not inverted thus outputting no trigger signal Tac, Tbd. Consequently, AND gates 23a to 23d can creat and output control signals CNTa to CNTd continuously throughout the interval when phase switching signals Pha-Pad are inputted. This constitution allows high current drive operation while prohibiting chopping control and protects switching elements 21a to 21d against overheat by eliminating accumulation of heat due to chopping control. |
