US 7,072,164 B2Granted

Electric parts drive circuit

AssigneeNissin Kogyo Co., Ltd.

InventorsJunichi Amada, Tomoharu Tuchiya

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Abstract

An electric parts drive circuit has: a first field-effect transistor including in parallel a first parasitic diode and provided between the plus line and an electric part; a second field-effect transistor including in parallel a second parasitic diode, the first and second field-effect transistors being connected in series in order from the plus line to the electric part; a third field-effect transistor including in parallel a third parasitic diode and provided between a minus line and the electric part; a failure diagnosis switch unit; and a switch control unit, wherein the switch control unit diagnoses a failure of the second field-effect transistor based on the voltage between the first and second field-effect transistors responsive to switching between conduction and shutoff of the second field-effect transistor in a state that the first and third field-effect transistors are shut off and the failure diagnosis switch unit is brought into conduction.

Claims7

Dependent claims

An electric parts drive circuit comprising:

a first field-effect transistor including in parallel a first parasitic diode for allowing an electric current flow into a plus line and provided between the plus line to be connected to a plus terminal of a battery and an electric part;
a second field-effect transistor for reverse connection protection including in parallel a second parasitic diode for allowing an electric current flow from the first field-effect transistor into the electric part, the first field-effect transistor and the second field-effect transistor being connected in series in order from the plus line to the electric part;
a third field-effect transistor including in parallel a third parasitic diode for allowing an electric current flow into the electric part and provided between a minus line to be connected to a minus terminal of the battery and the electric part;
a failure diagnosis switch unit for switching between conduction and shutoff between a drain of the second field-effect transistor and the plus terminal of the battery;
and
a switch control unit for controlling switching between conduction and shutoff of the first to third field-effect transistors and the failure diagnosis switch unit,
wherein the switch control unit diagnoses a failure of the second field-effect transistor based on the voltage between the first and second field-effect transistors responsive to switching between conduction and shutoff of the second field-effect transistor in a state that the first and third field-effect transistors are shut off and the failure diagnosis switch unit is brought into conduction,
wherein the failure diagnosis switch unit includes:
a PNP transistor having a collector connected via a first resistor between the plus terminal of the battery and the drain of the second field-effect transistor;
second resistors and an NPN transistor connected in series between the plus terminal of the battery and ground;
and
third resistors connected in series between the switch control unit and ground,
wherein a connection point of the second resistors is connected to a base of the PNP transistor and a connection point of the third resistors is connected to a base of the NPN transistor.

10 more elements

An electric parts drive circuit, comprising:

a first field-effect transistor including in parallel a first parasitic diode;
a second field-effect transistor for reverse connection protection including in parallel a second parasitic diode;
a third field-effect transistor including in parallel a third parasitic diode;
wherein the first field-effect transistor, the second field-effect transistor, an electric part, and the third field effect-transistor are connected in series between a plus terminal and a minus terminal of a battery;
a failure diagnosis switch unit between a drain of the second field-effect transistor and the plus terminal of the battery;
and
a switch control unit for controlling switching between conduction and shutoff of the first field-effect transistor, the second field-effect transistor, the third field effect-transistor, and the failure diagnosis switch unit,
wherein the switch control unit diagnoses a failure of the second field-effect transistor.

5 more elements

Dependencies are inferred from the claim text.