Ground-fault detecting device and insulation resistance measuring device

• US 6,984,988 B2
• Filed: 10/16/2003
• Issued: 01/10/2006
• Est. Priority Date: 10/16/2002
• Status: Active Grant

• Current Assignee: Yazaki Corporation
• Original Assignee: Yazaki Corporation
• Inventors: Yamamoto, Koichi
• Primary Examiner(s): Benson, Walter
• Application Number:
  US10/685,591
• Publication Number:
  US 20040130326A1
• Time in Patent Office: 817 Days
• Field of Search: 324/503, 324/509, 324/520, 324/522, 702/117
• US Class Current: 324/509
• CPC Class Codes: B60L 3/0023 Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
• CPC Class Codes: B60L 3/0069 relating to the isolation, e.g. ground fault or leak current
• CPC Class Codes: B60W 50/04 Monitoring the functioning of the control system
• CPC Class Codes: G01R 31/52 Testing for short-circuits, leakage current or ground faults

Abstract

A ground-fault detecting device includes a power source which is electrically insulated from a vehicle body, a pulse signal generator which generates a pulse signal having a high level and a low level which appear repeatedly in a prescribed cycle, a detection resistor which is connected to the pulse signal generator and the power source, a coupling capacitor which is connected to the detecting resistor in series, an integrator which integrates a difference between a first reference voltage and a detection voltage of the pulse signal at a connecting point of the detection resistor and the coupling capacitor over an integration interval, and a ground-fault determinant which judges whether a ground fault has occurred on the basis of an output of the integrator. The integration interval is at least part of a high-level interval and a low-level interval of the pulse signal.

Claims

1. A ground-fault detecting device, comprising:

a power source, electrically insulated from a vehicle body;

a pulse signal generator, generating a pulse signal having a high level and a low level which appear repeatedly in a prescribed cycle;

a detection resistor, connected to the pulse signal generator and the power source;

a coupling capacitor, connected to the detecting resistor in series;

an integrator, integrating a difference between a first reference voltage and a detection voltage of the pulse signal at a connecting point of the detection resistor and the coupling capacitor over an integration interval; and

a ground-fault determinant, judging whether a ground fault has occurred on the basis of an output of the integrator,

wherein the integration interval has at least part of a high-level interval or a low-level interval of the pulse signal.

2. The ground-fault detecting device as set forth in claim 1, wherein the integrator includes:

an integration circuit, integrating the difference between the detection voltage and the first reference voltage; and

an integration reset signal generation circuit, generating a reset signal for rendering the integration circuit in a reset state over intervals other than the integration interval on the basis of the pulse signal supplied from the pulse signal generator.

3. The ground-fault detecting device as set forth in claim 1, wherein the ground-fault determinant is a hysteresis comparator which compares the output of the integrator with a second reference voltage for obtaining a ground-fault detection output.

4. The ground-fault detecting device as set forth in claim 1, wherein the ground-fault determinant is a sample-and-hold circuit which sample-and-holds the output of the integrator as an integration value for obtaining a ground-fault detection output.

5. The ground-fault detecting device as set forth in claim 1, further comprising a compensation capacitor, having a capacitance corresponding to a vehicle-side capacitance, and provided between the vehicle body and the coupling capacitor.

6. The ground-fault detecting device as set forth in claim 1, wherein the integrator comprises an operational amplifier, a switch, and a reset signal generation circuit.

7. An insulation resistance measuring device, comprising:

a power source;

an insulation resistance, electrically insulating the power source from a vehicle body;

a pulse signal generator, generating a pulse signal having a high level and a low level which appear repeatedly in a prescribed cycle;

a detection resistor, connected to the pulse signal generator and the power source;

a coupling capacitor, connected to the detecting resistor in series;

an integrator, integrating a difference between a first reference voltage and a detection voltage of the pulse signal at a connecting point of the detection resistor and the coupling capacitor over an integration interval; and

an A/D converter, A/D converting an output of the integrator as an integration value so as to generate a digital value corresponding to a resistance value of the insulation resistance,

wherein the integration interval has at least part of a high-level interval or a low-level interval of the pulse signal.

8. The insulation resistance measuring device as set forth in claim 7, further comprising a ground-fault determinant, judging whether a ground fault has occurred on the basis of an output of the integrator.

9. The insulation resistance measuring device as set forth in claim 7, further comprising a compensation capacitor, having a capacitance corresponding to a vehicle-side capacitance, and provided between the vehicle body and the coupling capacitor.

10. The insulation resistance measuring device as set forth in claim 7, wherein the integrator comprises an operational amplifier, a switch, and a reset signal generation circuit.