Ground-fault detecting device and insulation resistance measuring device
View Patent ↗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.
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.