| 摘要 |
PROBLEM TO BE SOLVED: To provide an electric load drive apparatus which can detect accurately an overcurrent of an output transistor which supplies a drive current to the electric load, regardless of a voltage fluctuation even if the output pattern of the output transistor is set on a high side or a low side. SOLUTION: (1): If an output transistor (FET) 41 is made to function as a high side drive means, this apparatus supplies a step-up voltage VCP higher than a battery voltage (hereinafter referred to as VB) to the gate of the FET 41 in accordance with a drive signal Aa. (2): If the FET 41 is made to function as a low side drive means, this apparatus supplies the VB to the gate of the FET 41 in accordance with the drive signal Aa. In the case of (1), a detected voltage V1 which is lowered in proportion to the current of the FET 41 with the VB as a reference is compared with a decision voltage Vref1 with the VB as the reference to detect an overcurrent. In the case of (2), a detection voltage V2 which is elevated in proportion to the current of the FET 41 with an earth potential as a reference is compared with a decision voltage Vref2 with the earth potential as the reference to detect an overcurrent.
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