Load Drive Circuit

• US 20090079435A1
• Filed: 08/14/2008
• Published: 03/26/2009
• Est. Priority Date: 09/20/2007
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi, Ltd.
• Inventors: NAKATA, Hisayoshi, Sasaki, Masahiro, Oura, Ryoichi, Watanabe, Mitsuhiko, Mayuzumi, Takuya
• Granted Patent: US 8,548,641 B2
• Time in Patent Office: Days
• US Class Current: 324/500
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

According to the present invention, the operation of a diagnostic circuit within a load drive circuit, which has been built into an electronic control device, is checked without modifying the electronic control device or the like. The load drive circuit, which drives a load such as a solenoid using a DC power supply as a power supply, includes a drive circuit and a diagnostic circuit which is independently provided within the drive circuit. Upon input of a drive-stop signal from a control circuit that controls the drive circuit, the operation of at least the drive circuit stops, so that whether the diagnostic circuit, which diagnoses the condition of the load, is normally operating or not is checked in a condition in which the load drive circuit has been built into the electronic control device.

Claims

1. A load drive circuit built into an electronic control device, which drives a load such as a solenoid, relay, switch, heater, or motor using a DC power supply as a power supply, the load drive circuit comprising:

a drive circuit; and

a diagnostic circuit independently provided within the drive circuit,

wherein, upon input of a drive-stop signal from a control circuit that controls the drive circuit, the operation of at least the drive circuit stops, so that whether the diagnostic circuit, which diagnoses the condition of the load, is normally operating or not is checked in a condition in which the load drive circuit has been built into the electronic control device.

2. The load drive circuit according to claim 1, wherein a load drive signal is input to the load drive circuit, in which the operation of at least the drive circuit has stopped in response to the drive-stop signal from the control circuit, to detect an abnormality of the load, so that whether the diagnostic circuit is normally operating or not is checked.

3. The load drive circuit according to claim 1, wherein whether the diagnostic circuit is normally operating or not is checked during a system initialization process, the system initialization process being executed after the control circuit, which controls the electronic control device including the load drive circuit, has been switched on.

4. The load drive circuit according to claim 1, wherein whether the diagnostic circuit is normally operating or not is checked during a system stop process, the system stop process being executed during the period from the input of a power-off signal to the electronic control device including the load drive circuit until the power is actually switched off.

5. The load drive circuit according to claim 1, wherein:

the drive circuit is a low-side driver,

the drive circuit, in response to a drive-stop signal, enters a disable state in which the operation of at least the drive circuit stops, and

the drive circuit, in response to an input signal for driving, causes the diagnostic circuit to monitor the voltage at a terminal of the load or the current flowing through the drive circuit, so that the operation of the diagnostic circuit is checked.

6. The load drive circuit according to claim 1, wherein:

the drive circuit is a high-side driver,

the drive circuit, in response to a drive-stop signal, enters a disable state in which the operation of at least the drive circuit stops, and

the drive circuit, in response to an input signal for driving, causes the diagnostic circuit to monitor the voltage at a terminal of the load or the current flowing through the drive circuit, so that the operation of the diagnostic circuit is checked.

7. The load drive circuit according to claim 1, wherein:

the drive circuit is a motor drive circuit that drives a motor such as a brushed DC motor, three-phase motor, or stepping motor,

the drive circuit, in response to a drive-stop signal, enters a disable state in which the operation of at least the drive circuit stops, and

the drive circuit, in response to an input signal for driving, causes the diagnostic circuit to monitor the voltage at a terminal of the load or the current flowing through the drive circuit, so that the operation of the diagnostic circuit is checked.

8. The load drive circuit according to claim 3, wherein:

the load drive circuit is built into a vehicle'"'"'s load drive device, and

whether the diagnostic circuit is normally operating or not is checked during the system initialization process, the system initialization process being executed after an ignition key of a vehicle has been turned to an “

on”

position.

9. The load drive circuit according to claim 4, wherein:

the load drive circuit is built into a vehicle'"'"'s load drive device, and

whether the diagnostic circuit is normally operating or not is checked during the system stop process, the system stop process being executed after an ignition key of a vehicle has been turned to an “

off”

position.

10. The load drive circuit according to claim 1, wherein a switching element of the drive circuit is a bipolar transistor.

11. The load drive circuit according to claim 1, wherein a switching element of the drive circuit is an FET.

12. The load drive circuit according to claim 1, wherein a switching element of the drive circuit is an IGBT.