| 摘要 |
PROBLEM TO BE SOLVED: To reliably detect overcurrent and operate an overcurrent protection function in a load driver. SOLUTION: If overcurrent is produced in normal rotation driving, FET placed in the energization path produces heat and the resistance value of the FET is increased with temperature rise. In conjunction with increase in this resistance value, the value of the overcurrent is reduced. An overcurrent determination time T1 is set with this taken into account. That is, the overcurrent determination time T1 is set at a time shorter than a time it takes for the value of overcurrent to reach a reference current value i0. If the overcurrent occurs, therefore, a current the value of which exceeds a threshold value (reference current value i0), is detected over the overcurrent determination time T1. As a result, the overcurrent is detected without an influence of variation in resistance value arising from heating from the FET, and thus the breakage of a load driver including the FET, due to overcurrent, is prevented. COPYRIGHT: (C)2010,JPO&INPIT
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