Patent Description:
The present application originates from Japanese Patent Application <CIT>.

A ground fault detection device for detecting ground faults in a direct-current power source grid comprising a battery group is known in which a detection resistor and a coupling capacitor for direct-current cutoff are connected between a pulse signal generating means and a ground fault detection terminal connected to a direct-current negative electrode feed line, and a reduction in insulation resistance during a ground fault is sensed from the difference between a reference voltage and the detected voltage of a pulse signal occurring at a point of connection of the detection resistor and the coupling capacitor (Patent Document <NUM>).

Patent Document <NUM>: Japanese Laid-Open Patent Application <CIT>.

Document <CIT> discloses a ground fault detection circuit and device having a first switch circuit connecting a first path between a positive bus bar and a ground potential section. The positive bus bar is connected to positive electrodes of a secondary battery through a field-effect transistor including a parasitic diode. A second switch circuit is provided for connecting a second path between a negative bus bar and a ground potential section. The negative bus bar is connected to negative electrodes of the secondary battery. A ground fault detection unit is provided for detecting a ground fault of the positive bus bar or the negative bus bar based on an electric current flowing through the first path or through the second path.

Document <CIT> proposes an insulation resistance drop detector which comprises a pulse generator that applies a pulse signal to a series circuit in which a detecting resistor, a coupling capacitor, and an insulating resistance are serially connected. In a state where the pulse signal is applied to the series circuit, the control circuit detects a pulse-like divided voltage occurring at a node by a voltage detecting circuit via a band pass filter, to thereby sense a drop of an insulation resistance. Further, the control circuit senses a failure of the insulation resistance drop detector itself when the voltage detected by the voltage detecting circuit is maintained at least at a prescribed voltage exceeding a plurality of cycles of the pulse signal. Thus, the insulation resistance drop detector having a failure self-diagnosis function is realized by a simple configuration.

Document <CIT> suggests a controller for a vehicle which is equipped with two inverters determines whether a detector is conducting an insulation assessment. If the insulation assessment is not being conducted, then the controller provides random control to the two inverters to randomly vary carrier frequencies associated respectively therewith. On the other hand, if the insulation assessment is being conducted, the controller prohibits the random control to fix the carrier frequencies to respective reference frequencies. The reference frequencies are set in advance in a manner such that the difference between the reference frequencies is greater than a predetermined value.

However, in a power supply system in which the direct-current power source grid described above is connected to alternating-current grid electric power via an inverter, and a direct-current power source is charged by the alternating-current grid electric power, the alternating-current grid electric power is grounded. The conventional ground fault detection device described above therefore has the drawback of being incapable of sensing a reduction in insulation resistance during a ground fault.

An object of the present invention is to provide a power supply device provided with a grounded alternating-current power source and a secondary cell connected to the alternating-current power source, the power supply device being capable of detecting a ground fault in the secondary cell.

The object underlying the present invention is achieved by a power source device according to independent claim <NUM>. Preferred embodiments of the power source device are defined in the dependent claims.

In the present invention for achieving the abovementioned object, inter alia a first switch for selectively connecting or cutting off a secondary cell and an alternating-current power source is connected between the secondary cell and the alternating-current power source, a ground fault sensing means for sensing a ground fault in the secondary cell is connected closer to the secondary cell than the first switch, and a ground fault in the secondary cell is sensed by the ground fault sensing means in a state in which the first switch is off.

Through the present invention, a grounding portion of the alternating-current power source and a circuit portion for sensing of a ground fault in the secondary cell by the ground fault sensing means are cut off by the turning off of the first switch. A ground fault in the secondary cell can therefore be sensed without affecting the grounding of the alternating-current power source.

<FIG> is a circuit diagram illustrating the power supply system of the power supply device according to an embodiment of the present invention. The power supply device of the present example is applied to a household or commercial power supply system which uses an alternating-current power source as one current source.

The power supply system including the power supply device of the present example is provided with an alternating-current power source <NUM>, an inverter <NUM>, a battery (secondary cell) <NUM>, a smoothing capacitor <NUM>, a relay switch <NUM> (first switch), and a ground fault sensing circuit <NUM>. The alternating-current power source <NUM> is an electric power source for supplying electric power to a load not illustrated in the drawing, and is also an electric power source for supplying charging electric power to the battery <NUM> via the inverter <NUM>. The alternating-current power source <NUM> includes a transformer, and is grounded by connecting a neutral point of the secondary side of the transformer to ground. The transformer is a common transformer provided to a household or facility to transform alternating-current electric power supplied from a power company for output, for example.

The inverter <NUM> is an AC/DC conversion circuit in which a plurality of switching elements is connected in bridged fashion, and is a conversion circuit for converting alternating-current electric power supplied from the alternating-current power source <NUM> into direct-current electric power and supplying the direct-current electric power to the battery <NUM>. The inverter <NUM> converts direct-current electric power outputted from the battery <NUM> into alternating-current electric power and supplies electric power to a load <NUM>. The inverter <NUM> is connected to a pair of power supply lines connected to the alternating-current power source <NUM> and is connected between the alternating-current power source <NUM> and the battery <NUM>.

The battery <NUM> is a storage cell in which a plurality of lithium-ion cells or other secondary cells is connected. In the power supply system of the present example, the battery <NUM> is a cell for storing electric power to be supplied to a load not illustrated in the drawing. In the present example, electric power is controlled so that the battery <NUM> is charged by electric power from the alternating-current power source <NUM> during late-night hours in which electric utility rates are inexpensive, and the electric power saved in the battery <NUM> is supplied to a load during daytime hours, for example.

The smoothing capacitor <NUM> is a capacitor for rectifying the electric power supplied to the battery <NUM> from the inverter <NUM>, and is connected between the positive-electrode side and negative-electrode side of the pair of power supply lines, and connected between the inverter <NUM> and the relay switch <NUM>.

The relay switch <NUM> is a switch for providing conduction and cutoff between the battery <NUM> and the alternating-current power source <NUM>, and is connected between the inverter <NUM> and the battery <NUM>. When the relay switch <NUM> is off, electric power from the battery <NUM> is not supplied to the inverter <NUM>, and electric power from the inverter <NUM> is not supplied to the battery <NUM>.

The ground fault sensing circuit <NUM> is a circuit for sensing a ground fault in the battery <NUM>, and is connected on the battery <NUM> side of the relay switch <NUM>. In the example illustrated in <FIG>, the ground fault sensing circuit <NUM> is connected to an electric power line for connecting a negative electrode of the battery <NUM> and a junction on the negative-electrode side of the relay switch <NUM>. In other words, the ground fault sensing circuit <NUM> is connected between the battery <NUM> and the relay switch <NUM>, and when the relay switch <NUM> is off, the ground fault sensing circuit <NUM> therefore becomes able to sense a ground fault (i.e., a decrease in insulation resistance) by detecting the insulation resistance of the battery <NUM>. When the relay switch <NUM> is on, conduction occurs to the ground of the alternating-current power source <NUM> via the relay switch <NUM> and the inverter <NUM>, and it is therefore impossible to distinguish whether the smallness of the detected insulation resistance is due to a decrease in insulation resistance of the battery <NUM> or a decrease in insulation resistance due to grounding of the alternating-current power source <NUM>, and a ground fault in the battery <NUM> cannot be sensed.

The ground fault sensing circuit <NUM> has capacitors <NUM>, <NUM>, resistors <NUM>, <NUM>, a pulse transmitter <NUM>, and a comparator <NUM>. One end of the capacitor <NUM> is connected to the battery <NUM> (to an electric power line connected to an electrode terminal of the battery <NUM>), and the other end is connected to the pulse transmitter <NUM> via the resistor <NUM>. In other words, the pulse transmitter <NUM> is connected to the power supply line via a series circuit of the capacitor <NUM> and the resistor <NUM>. A low-pass filter comprising the series circuit of the resistor <NUM> and the capacitor <NUM> is connected to the connection point (measurement point) between the capacitor <NUM> and the resistor <NUM>. The input side of the comparator <NUM> is connected to a reference voltage <NUM> and the connection point between the resistor <NUM> and the capacitor <NUM>, and the output side of the comparator <NUM> is connected to a controller described hereinafter.

In the case of sensing a ground fault in the battery <NUM> through use of the ground fault sensing circuit <NUM>, a pulse which is a voltage signal having a predetermined amplitude is outputted from the pulse transmitter <NUM> and inputted to the battery <NUM> (to an electric power line connected to an electrode terminal of the battery <NUM>) via the capacitor <NUM>. A voltage variation at the other-end side of the capacitor <NUM>, i.e., on the side of the point of connection to the resistor <NUM> (at the measurement point), in accordance with the insulation resistance of the battery <NUM> is manifested as an amplitude variation in the input voltage inputted to a comparator <NUM>. Therefore, by comparing the amplitude voltage and the reference voltage, the ground fault sensing circuit <NUM> determines whether the insulation resistance of the battery <NUM> has decreased. The reference voltage is a voltage threshold value set in advance that corresponds to the insulation resistance for sensing a ground fault in the battery <NUM>. In other words, the amplitude (amplitude voltage) of the input voltage inputted to the comparator <NUM> corresponds to the insulation voltage, and a decrease in the insulation resistance of the battery <NUM> (a ground fault) is therefore detected by comparing the amplitude voltage with the reference voltage. In brief, the ground fault sensing circuit <NUM> can also be considered to detect the insulation resistance (i.e., the amplitude voltage) and compare the detected insulation resistance with an insulation resistance that serves as a reference for sensing a ground fault (i.e., a reference voltage) to sense the occurrence of a ground fault.

When a ground fault is not occurring in the battery <NUM>, the amplitude voltage (response voltage) inputted to the comparator <NUM> is higher than the reference voltage. When a ground fault is occurring in the battery <NUM>, the insulation resistance of the battery <NUM> decreases (e.g., substantially to zero), and the amplitude voltage inputted to the comparator <NUM> is therefore lower than the reference voltage. The ground fault sensing circuit <NUM> thereby senses a ground fault in the battery <NUM> by comparing the reference voltage and the amplitude voltage for the input pulse of the pulse transmitter <NUM>. The load <NUM> is an electrical equipment load provided to a household or facility that is driven by alternating-current electric power from the alternating-current power source <NUM> or alternating-current electric power outputted from the inverter <NUM>.

The electric power grid of the power supply system of the present example will next be described using <FIG> is a block diagram illustrating the electric power grid of the power supply system of <FIG>. In <FIG>, thick lines indicate electric power lines (power supply lines) and arrows indicate signal lines.

The alternating-current power source <NUM>, the inverter <NUM>, the relay switch <NUM>, the load <NUM>, and the battery <NUM> are connected by electric power lines. A controller <NUM> controls the alternating-current power source <NUM>, the inverter <NUM>, the battery <NUM>, the relay switch <NUM>, and the ground fault sensing circuit <NUM>, and is connected by signal lines.

Control of the power supply system of the present example will next be described. The controller <NUM> switches between a normal control mode and a ground fault sensing mode for sensing a ground fault in the battery <NUM>, and controls the relay switch <NUM> and other components. The normal control mode will first be described.

In the normal control mode, the controller <NUM> turns on the relay switch <NUM> and creates a state in which electric power from the battery <NUM> is supplied to the load <NUM> (via the inverter <NUM>), electric power from the alternating-current power source <NUM> is supplied to the battery <NUM> (via the inverter <NUM>), and it is possible to charge the battery <NUM>. The controller <NUM> controls the alternating-current power source <NUM>, the inverter <NUM>, and the battery <NUM> in accordance with the demand electric power, a time block, or another factor that corresponds to the usage status of the load. For example, in daytime or other time blocks in which electric utility rates are high, the controller <NUM> supplies electric power from the battery <NUM> to the load <NUM>. When the amount of electric power demanded by the load <NUM> is large and cannot be covered solely by the electric power of the battery <NUM>, the controller <NUM> supplies electric power from the alternating-current power source <NUM> to the load <NUM> in addition to the electric power of the battery <NUM>.

In time blocks in which electric utility rates are low, the controller <NUM> charges the battery <NUM> while supplying electric power from the alternating-current power source <NUM> to the load <NUM>. During charging of the battery <NUM>, the controller <NUM> manages the charging state of the battery <NUM> and controls the charging electric power supplied from the inverter <NUM> to the battery <NUM> so that the battery <NUM> is not overcharged. The controller <NUM> thereby manages electric power in the power supply system of the present example.

The ground fault sensing mode will next be described. In a state in which the relay switch <NUM> is on as described above, when a pulse is issued from the pulse transmitter <NUM>, voltages are compared by the comparator <NUM>, and the insulation resistance of the battery <NUM> is thereby detected in order for the ground fault sensing means <NUM> to sense a ground fault in the battery <NUM>, grounding of the alternating-current power source <NUM> causes the amplitude voltage inputted to the comparator <NUM> to fall below the voltage threshold value. The insulation resistance of the battery <NUM> therefore decreases even when there is no ground fault in the battery <NUM>, and it is possible for a ground fault in the battery <NUM> to be erroneously sensed. Control is therefore performed in the present example so that the relay switch <NUM> is placed in the off state prior to ground fault sensing by the ground fault sensing circuit <NUM>.

When the ground fault sensing mode is to be executed, the controller <NUM> first confirms the on or off state of the relay switch <NUM>. When the relay switch <NUM> is off, the controller <NUM> activates the ground fault sensing circuit <NUM> and senses a ground fault in the battery <NUM> by measuring the insulation resistance of the battery <NUM>.

During execution of the ground fault sensing mode, when the relay switch <NUM> is on, the controller <NUM> detects the electric current flowing through the relay switch <NUM> and determines whether the detected electric current is lower than a predetermined electric current threshold value. The electric current threshold value is set in advance and is an electric current having the threshold value necessary for turning off the relay switch <NUM>. The detected electric current may be detected by connecting an electric current sensor to the power supply line to which the relay switch <NUM> is connected. Alternatively, since the electric power of the alternating-current power source <NUM> and the charging/discharging electric power of the battery <NUM> are controlled in accordance with the demand electric power of the load, the controller <NUM> may detect the electric current flowing to the relay switch <NUM> from the charging/discharging electric power of the battery <NUM>.

When the detected electric current in the relay switch <NUM> is lower than the electric current threshold value (e.g., when the detected electric current is substantially zero), the relay switch <NUM> is turned off, and even when the supply of electric power from the battery <NUM> to the load <NUM> is cut off, because the decrease in electric power supplied to the load <NUM> due to the cutoff is small, the load <NUM> can be driven by the electric power from the alternating-current power source <NUM>. When the battery <NUM> is being charged, the battery <NUM> may be charged after ground fault sensing is completed. Consequently, when the detected electric current in the relay switch <NUM> is lower than the electric current threshold value, the controller <NUM> turns off the relay switch <NUM>, activates the ground fault sensing circuit <NUM>, and performs ground fault detection in the battery <NUM>.

When the detected electric current in the relay switch <NUM> is equal to or greater than the electric current threshold value, the controller <NUM> detects the electric current in the relay switch <NUM> while leaving the relay switch <NUM> in the on state. At the instant that the detected electric current in the relay switch <NUM> becomes lower than the electric current threshold value, the controller <NUM> turns off the relay switch and senses ground faults in the battery <NUM>.

When it is assessed that a ground fault is occurring in the battery <NUM>, the controller <NUM> restricts charging and discharging of the battery <NUM> by maintaining the relay switch <NUM> in the off state while notifying a user that a ground fault has occurred.

The procedure of control by the controller <NUM> in the ground fault sensing mode will next be described using <FIG> is a flowchart illustrating the procedure of control by the controller <NUM>.

The controller <NUM> performs the control process illustrated in <FIG> when executing the ground fault sensing mode. First, in step S1, the controller <NUM> confirms whether the relay switch <NUM> (first switch) is off. When the relay switch <NUM> is off, the process proceeds to step S5.

When the relay switch <NUM> is not off, the controller <NUM> detects the electric current in the relay switch <NUM> (step S2). In step S3, the controller <NUM> compares the detected electric current in the relay switch <NUM> and the electric current threshold value. When the detected electric current in the relay switch <NUM> is equal to or greater than the electric current threshold value, the process returns to step S2, and the electric current in the relay switch <NUM> is again detected.

When the detected electric current is lower than the electric current threshold value, the controller <NUM> turns off the relay switch <NUM> (step S4).

In step S5, the controller <NUM> activates the ground fault sensing circuit <NUM>. In step S6, the ground fault sensing circuit <NUM> measures the insulation resistance of the battery <NUM> by measuring the response voltage for the pulse of the pulse transmitter <NUM>.

In step S7, the ground fault sensing circuit <NUM> detects whether the insulation resistance is equal to or greater than a ground fault sensing threshold value by comparing the corresponding response voltage and the reference voltage through use of the comparator <NUM>. The ground fault sensing threshold value corresponds to the reference voltage <NUM>. When the insulation resistance is equal to or greater than the ground fault sensing threshold value, the controller <NUM> in step S8 assesses that there is no ground fault in the battery <NUM>, turns on the relay switch <NUM>, and ends the ground fault sensing mode.

When the insulation resistance is less than the ground fault sensing threshold value, the controller <NUM> in step S9 assesses from the result of comparison by the comparator <NUM> that a ground fault is occurring in the battery <NUM>, notifies the user that a ground fault has occurred, and ends the ground fault sensing mode.

As described above, in the present example, a ground fault in the battery <NUM> is sensed by the ground fault sensing circuit <NUM> when the relay switch <NUM> connected between the alternating-current power source <NUM> and the battery <NUM> is off. In the present example, a ground fault in the battery <NUM> can thereby be sensed in a power supply device for supplying electric power from the grounded alternating-current power source <NUM> to the battery <NUM> via the inverter.

In a possible method for sensing a ground fault in the battery <NUM>, a ground fault is sensed by an operator using a megohm tester after placing the battery <NUM> in an insulated state (a state in which the alternating-current power source <NUM> and the battery <NUM> are electrically isolated). However, because a ground fault can be sensed without use of a megohm tester in the present example, the number of man-hours involved in ground fault sensing can be reduced.

In another possible method, during ground fault sensing in the battery <NUM>, ground fault sensing in the battery <NUM> is performed after a transformer has been provided between the inverter <NUM> and the battery <NUM> in order to ensure an insulated state in the battery <NUM>. However, when a transformer is provided, the size of the system is increased, cost of the power supply device increases, and the operating noise of the power supply device become significant. However, an insulated state is ensured in the present example by turning of the relay switch <NUM>, and the abovementioned transformer can therefore be omitted.

In the present invention, the controller <NUM> turns off all of the plurality of switching elements included in the inverter <NUM>, and ground fault sensing in the battery <NUM> may therefore be performed by the ground fault sensing circuit <NUM> in a state in which the alternating-current power source <NUM> and the battery <NUM> are electrically isolated from each other. When the plurality of switching elements of the inverter <NUM> are turned off, the ground fault sensing circuit <NUM> is cut off from the alternating-current power source <NUM>, and it is therefore possible to prevent the ground fault sensing circuit <NUM> from erroneously sensing the grounding of the alternating-current power source <NUM> as a ground fault in the battery <NUM>.

In the present invention, the controller <NUM> may also be caused to turn off the relay switch <NUM> at a predetermined cycle, and control the ground fault sensing circuit <NUM> to sense ground faults in the battery <NUM>. The predetermined cycle is set in advance, and is set to one day (<NUM> hours), for example. It is thereby possible to periodically perform ground fault sensing in the battery <NUM> in the present example.

The timing at which the relay switch <NUM> is turned off at a predetermined cycle may be set to late-night hours, for example, in which charging/discharging control of the battery <NUM> is not being performed.

In the present invention, the controller <NUM> may measure the time elapsed from the last time ground fault sensing was performed, and when the measured elapsed time exceeds a limit time set in advance, the controller <NUM> may turn off the relay switch <NUM> and cause ground faults in the battery <NUM> to be sensed. Measurement of the elapsed time may be reset when the detected electric current in the relay switch <NUM> falls below the electric current threshold value and ground fault sensing is performed before the measured elapsed time has exceeded the limit time. It is thereby possible to periodically perform ground fault sensing in the battery <NUM> in the present example.

Specifically, the controller <NUM> turns off the relay switch <NUM> and causes ground faults in the battery <NUM> to be sensed at least once per a predetermined time. Through this configuration, even in a continued state in which the relay switch <NUM> is on, the relay switch <NUM> can be turned off and ground faults in the battery <NUM> can be sensed. As a result, a highly safe system can be provided.

In the present example, when the time block in which the alternating-current power source <NUM> is used is a nighttime electric power time block (an intra-day time block in which electric utility rates decrease), the controller <NUM> may turn off the relay switch <NUM>, and ground faults in the battery <NUM> may be sensed by the ground fault sensing circuit <NUM>. Through this configuration, since the relay switch <NUM> is turned off during the nighttime electric power time block for the battery <NUM>, ground faults in the battery <NUM> can be sensed while the effect of using the alternating-current power source <NUM> on the electric utility rate is minimized when the amount of electric power that cannot be supplied to the load <NUM> from the battery <NUM> is supplemented by electric power from the alternating-current power source <NUM>. As a result, a highly safe system can be provided without increasing the economic burden on the user.

The abovementioned relay switch <NUM> corresponds to the "first switch" of the present invention, the ground fault sensing circuit <NUM> corresponds to the "ground fault sensing means" of the present invention, and the controller <NUM> corresponds to the "control means" of the present invention.

<FIG> is a circuit diagram illustrating the power supply system of the power supply device according to another embodiment of the present invention. The present example differs from the first embodiment in that a relay switch <NUM>, an electricity leakage sensing circuit <NUM>, a DC/DC converter <NUM>, and a power generator <NUM> are provided. All other aspects of the configuration of the second embodiment are the same as in the first embodiment, and descriptions thereof will therefore be quoted as appropriate.

As illustrated in <FIG>, the power supply system including the power supply device of the present example is provided with an alternating-current power source <NUM>, an inverter <NUM>, a battery <NUM>, a smoothing capacitor <NUM>, a relay switch <NUM> (first switch), a ground fault sensing circuit <NUM>, a relay switch <NUM> (second switch), an electricity leakage sensing circuit <NUM>, a DC/DC converter <NUM>, a power generator <NUM>, and a load <NUM>. The configurations and connection relationships of the alternating-current power source <NUM>, the inverter <NUM>, the battery <NUM>, the smoothing capacitor <NUM>, the relay switch <NUM> (first relay), and the ground fault sensing circuit <NUM> are the same as in the power supply system according to the first embodiment, and therefore will not be described.

The relay switch <NUM> is provided in order to cut off the circuit on the reverse side of the inverter <NUM> from the alternating-current power source <NUM>, i.e., the circuit including the battery <NUM>, the relay switch <NUM>, the ground fault sensing circuit <NUM>, and the electricity leakage sensing circuit <NUM>, from the alternating-current power source <NUM>. The relay switch <NUM> is connected between the alternating-current power source <NUM> and the inverter <NUM>, and is provided to a power supply line. The load <NUM> is connected between the relay switch <NUM> and the inverter <NUM> on the power supply line.

The electricity leakage sensing circuit <NUM> is a circuit for sensing electricity leakage in the power generator <NUM>. The electricity leakage sensing circuit <NUM> is connected closer to the inverter <NUM> than the relay switch <NUM> via the DC/DC converter <NUM>, and is connected to each of a pair of power supply lines connected between the battery <NUM> and the inverter <NUM>.

the electricity leakage sensing circuit <NUM> has resistors <NUM>, <NUM> and an electric current sensor <NUM>. The resistor <NUM> is connected to the power supply line on the positive-electrode side, and the resistor <NUM> is connected to the power supply line on the negative-electrode side. The electric current sensor <NUM> is connected to each of the resistors <NUM>, <NUM> and is grounded. The electric current sensor <NUM> detects the electric current on the positive-electrode side from the electric current flowing to the resistor <NUM>, and detects the electric current on the negative-electrode side from the electric current flowing to the resistor <NUM>.

When electricity leakage occurs in the power generator <NUM>, the electric current difference between the electric current flowing to the resistor <NUM> and the electric current flowing to the resistor <NUM> is higher than a predetermined electric current threshold value. Therefore, in the present example, the electric current on the positive-electrode side of the power generator <NUM> and the electric current on the negative-electrode side of the power generator <NUM> are detected using the electricity leakage sensing circuit <NUM>, and the deviation of these electric currents is measured, and when the electric current deviation is higher than the electric current threshold value set in advance, it is assessed that electricity leakage is occurring in the power generator <NUM>.

The DC/DC converter <NUM> is connected between the power generator <NUM> and the inverter <NUM>, and is a conversion circuit for converting the electric power generated by the power generator <NUM> and supplying the electric power to the inverter <NUM> and the battery <NUM>.

The power generator <NUM> uses a self-generation function, and is configured from solar power generation or a fuel cell, for example. Specifically, the power supply system of the present example is provided with the alternating-current power source <NUM> and the battery <NUM>, and the power generator <NUM> as a third electric power source. The power generator <NUM> functions as an electric power source for supplying electric power to the load <NUM>, and functions also as an electric power source for charging the battery <NUM>. Through this configuration, a parallel circuit is formed from the battery <NUM> and the power generator <NUM>, and this parallel circuit is connected to the alternating-current power source <NUM> via the relay switch <NUM> in the present example.

The alternating-current power source <NUM>, the relay switch <NUM>, the inverter <NUM>, the relay switch <NUM>, the battery <NUM>, and the power generator <NUM> are connected by electric power lines. The controller <NUM> controls the alternating-current power source <NUM>, the inverter <NUM>, the battery <NUM>, the relay switch <NUM>, the ground fault sensing circuit <NUM>, the relay switch <NUM>, the electricity leakage sensing circuit <NUM>, and the power generator <NUM>, and is connected by signal lines.

Control of the power supply system of the present example will next be described. The controller <NUM> switches between a normal control mode, a ground fault sensing mode, and a disconnection sensing mode for sensing a disconnection in the electricity leakage sensing circuit <NUM>, and controls the relay switches <NUM>, <NUM>.

In the normal control mode, the controller <NUM> turns on the relay switch <NUM> and the relay switch <NUM> and controls the alternating-current power source <NUM> and other components.

In the ground fault sensing mode, the controller <NUM> turns off at least the relay switch <NUM>, and controls the ground fault sensing circuit <NUM> to sense a ground fault in the battery <NUM>.

In the disconnection sensing mode, the controller <NUM> confirms the state of the relay switch <NUM>, and when the relay switch <NUM> is off, the controller <NUM> controller performs the disconnection sensing control described below. When the relay switch <NUM> is on, the controller <NUM> compares the electric current in the relay switch <NUM> and the electric current threshold value set in advance. When the electric current in the relay switch <NUM> is lower than the electric current threshold value, the controller <NUM> turns off the relay switch <NUM>.

In the state in which the relay switch <NUM> is off, the controller <NUM> then turns on the relay switch <NUM>, a pulse signal is outputted from the pulse transmitter <NUM>, and a disconnection in the electricity leakage sensing circuit <NUM> is sensed from the output of the comparator <NUM>.

When the relay switch <NUM> is on, the ground fault sensing circuit <NUM> conducts through the resistors <NUM>, <NUM> to the grounding point of the electricity leakage sensing circuit <NUM> via the relay switch <NUM>. Therefore, when there is a disconnection in the electricity leakage sensing circuit <NUM>, the amplitude voltage (response voltage) inputted to the comparator <NUM> is higher than the reference voltage for the input pulse from the pulse transmitter <NUM>. When there is no disconnection in the electricity leakage sensing circuit <NUM>, the amplitude voltage (response voltage) inputted to the comparator <NUM> is lower than the reference voltage. The controller <NUM> can thereby sense that a disconnection has occurred in the electricity leakage sensing circuit <NUM> if a ground fault is not detected by the ground fault sensing circuit <NUM> when the relay switch <NUM> is on.

When it is assessed that a disconnection has occurred in the electricity leakage sensing circuit <NUM>, the controller <NUM> notifies the user that a disconnection has occurred.

The control performed by the controller <NUM> in the ground fault sensing mode and the disconnection sensing mode will next be described using <FIG> is a flowchart illustrating the procedure of control by the controller <NUM>.

In step S10, control is performed for placing the relay switch <NUM> and the relay switch <NUM> in the off state. The control procedure for the relay switch <NUM> in step S10 is the same as the control procedure of steps S1 through S4 in the first embodiment. The control procedure of steps S1 through S4 may be substituted as the control procedure for the relay switch <NUM> in step S10. Specifically, the relay switch <NUM> and the relay switch <NUM> may both be placed in the off state when it has been confirmed that the flowing electric current is smaller than a predetermined threshold electric current and the effect of placing the relay switch <NUM> and relay switch <NUM> in the off state is minimal.

After the control process of step S10, steps S15 through S <NUM> are the same as steps S5 through S8 of the first embodiment, and therefore will not be described.

When the determination of step S17 is that the insulation resistance is equal to or greater than the ground fault sensing threshold value, in step S20, the controller <NUM> assesses that there is no ground fault in the battery <NUM>, turns on only the relay switch <NUM> while the relay switch <NUM> is maintained in the off state, ends the ground fault sensing mode, and transitions to the disconnection sensing mode.

In step S21, the ground fault sensing circuit <NUM> measures the insulation resistance of the electricity leakage sensing circuit <NUM> by measuring the response voltage for the pulse of the pulse transmitter <NUM>. In step S22, the ground fault sensing circuit <NUM> detects whether the insulation resistance of the electricity leakage sensing circuit <NUM> is less than a disconnection sensing threshold value by comparing the corresponding response voltage and the reference voltage through use of the comparator <NUM>. The disconnection sensing threshold value is a threshold value for assessing whether there is a disconnection in the electricity leakage sensing circuit <NUM>, and is a value set in advance. Consequently, the disconnection sensing threshold value corresponds to the reference voltage and is set to a value higher than the response voltage for a case in which there is no disconnection in at least one of the resistors <NUM>, <NUM>. The disconnection sensing threshold value corresponds to the reference voltage <NUM>, but may be set to a value different from the ground fault sensing threshold value.

When the insulation resistance is less than the disconnection sensing threshold value, in step S23, the controller <NUM> assesses that there is no disconnection in the electricity leakage sensing circuit <NUM>, turns on the relay switch <NUM>, and ends the disconnection sensing mode.

When the insulation resistance is equal to or greater than the disconnection sensing threshold value, in step S24, it is assessed that a disconnection has occurred in the electricity leakage sensing circuit <NUM>, and the disconnection sensing mode is ended.

As described above, in the present example, the electricity leakage sensing circuit <NUM> is electrically connected, closer to the inverter <NUM> than the relay switch <NUM>, to a pair of power supply lines connected between the battery <NUM> and the inverter <NUM>, and when the relay switch <NUM> is on, disconnection in the electricity leakage sensing circuit <NUM> is sensed by the ground fault sensing circuit <NUM>. Disconnection can thereby be sensed without providing a separate dedicated mechanism for sensing disconnection in the electricity leakage sensing circuit <NUM>.

In the present example, when the relay switch <NUM> is off, disconnection in the electricity leakage sensing circuit <NUM> is sensed by the ground fault sensing circuit <NUM>. Disconnection in the electricity leakage sensing circuit <NUM> can thereby be sensed in a state in which the ground fault sensing circuit <NUM> is reliably cut off from the alternating-current power source <NUM>.

In the case of sensing disconnection in the electricity leakage sensing circuit <NUM> through use of the ground fault sensing circuit <NUM>, the relay switch <NUM> is off in the present example, but disconnection may also be sensed in a state in which the plurality of switching elements included in the inverter <NUM> is off.

The abovementioned relay switch <NUM> corresponds to the "second switch" of the present invention, the electricity leakage sensing circuit <NUM> corresponds to the "electricity leakage sensing means" of the present invention, and the power generator <NUM> corresponds to the "power generation means" of the present invention.

The power supply system of the power supply device according to another embodiment of the present invention will next be described. In the present example, a portion of the control of disconnection sensing in the electricity leakage sensing circuit <NUM> by the ground fault sensing circuit <NUM> differs from that of the second embodiment. All other aspects of the configuration of the third embodiment are the same as in the second embodiment, and descriptions thereof will therefore be quoted as appropriate.

When the relay switch <NUM> is off, the controller <NUM> specifies a disconnected portion of the electricity leakage sensing circuit <NUM> by alternately switching the on/off state of a positive-electrode switch <NUM>, which is the switch on the positive-electrode side of the relay switch <NUM>, with the on/off state of a negative-electrode switch <NUM>, which is the switch on the negative-electrode side, and measuring the insulation resistance of the electricity leakage sensing circuit <NUM>.

The controller <NUM> turns on the positive-electrode switch <NUM> of the relay switch <NUM> and turns off the negative-electrode switch <NUM> thereof, a pulse signal is outputted from the pulse transmitter <NUM>, and disconnection in the electricity leakage sensing circuit <NUM> is sensed from the output of the comparator <NUM>.

When positive-electrode switch <NUM> is on and the negative-electrode switch <NUM> is off, the ground fault sensing circuit <NUM> conducts through the resistor <NUM> on the positive-electrode side to the grounding point of the electricity leakage sensing circuit <NUM> via the positive-electrode switch <NUM>. On the negative-electrode side, since the negative-electrode switch <NUM> is off, the ground fault sensing circuit <NUM> does not conduct with the resistor <NUM> on the negative-electrode side.

In this state, when there is a disconnection in the resistor <NUM> portion, the amplitude voltage inputted to the comparator <NUM> is higher than the reference voltage for the input pulse from the pulse transmitter <NUM>. Similarly, the amplitude voltage inputted to the comparator <NUM> is higher than the reference voltage also when a disconnection has occurred in the grounding portion of the electricity leakage sensing circuit <NUM>. When there is no disconnection in the resistor <NUM> portion and the grounding portion of the electricity leakage sensing circuit <NUM>, the amplitude voltage inputted to the comparator <NUM> is lower than the reference voltage. It is thereby possible to sense an abnormality on the positive-electrode side of the electricity leakage sensing circuit <NUM> in the present example.

The controller <NUM> turns off the positive-electrode switch <NUM> of the relay switch <NUM> and turns on the negative-electrode switch <NUM> thereof, a pulse signal is outputted from the pulse transmitter <NUM>, and disconnection in the electricity leakage sensing circuit <NUM> is sensed from the output of the comparator <NUM>.

When positive-electrode switch <NUM> is off and the negative-electrode switch <NUM> is on, the ground fault sensing circuit <NUM> conducts through the resistor <NUM> on the negative-electrode side to the grounding point of the ground fault sensing circuit via the negative-electrode switch <NUM>. On the positive-electrode side, since the positive-electrode switch <NUM> is off, the ground fault sensing circuit <NUM> does not conduct with the resistor <NUM> on the positive-electrode side.

In this state, when there is a disconnection in the resistor <NUM> portion, the amplitude voltage inputted to the comparator <NUM> is higher than the reference voltage for the input pulse from the pulse transmitter <NUM>. Similarly, the amplitude voltage inputted to the comparator <NUM> is higher than the reference voltage also when a disconnection has occurred in the grounding portion of the electricity leakage sensing circuit <NUM>. When there is no disconnection in the resistor <NUM> portion and the grounding portion of the electricity leakage sensing circuit <NUM>, the amplitude voltage inputted to the comparator <NUM> is lower than the reference voltage. It is thereby possible to sense an abnormality on the negative-electrode side of the electricity leakage sensing circuit <NUM> in the present example.

The controller <NUM> can then distinguishably sense disconnection in the resistor <NUM>, disconnection in the resistor <NUM>, and disconnection and non-disconnection (normal state) in the grounding portion of the electricity leakage sensing circuit <NUM> by combining the disconnection sensing result when the positive-electrode switch <NUM> is on and the negative-electrode switch <NUM> is off and the disconnection sensing result when the positive-electrode switch <NUM> is off and the negative-electrode switch <NUM> is on.

Table <NUM> illustrates the results of disconnection sensing with respect to the state of the positive-electrode switch <NUM> and the state of the negative-electrode switch <NUM>, and to the result of measuring the insulation resistance.

In Table <NUM>, ON and OFF for the positive-electrode switch/negative-electrode switch indicate the on state and off state, respectively, of the switches <NUM>, <NUM>. For the positive-electrode switch and negative-electrode switch, ON/OFF indicates the on state for the positive-electrode switch <NUM> and the off state for the negative-electrode switch <NUM>. For the positive-electrode switch and negative-electrode switch, OFF/ON indicates the off state for the positive-electrode switch <NUM> and the on state for the negative-electrode switch <NUM>. A circle indicates a case in which the insulation resistance measured by the ground fault sensing circuit <NUM> is less than the disconnection sensing threshold value, and an x-mark indicates a case in which the insulation resistance measured by the ground fault sensing circuit <NUM> is equal to or greater than the disconnection sensing threshold value.

As illustrated in Table <NUM>, when the positive-electrode switch <NUM> is on and the negative-electrode switch <NUM> is off, and the amplitude voltage (corresponding to the voltage sensed by the ground fault sensing circuit <NUM>) inputted to the comparator <NUM> is less than the reference voltage for the input pulse from the pulse transmitter <NUM>, and when the positive-electrode switch <NUM> is off and the negative-electrode switch <NUM> is on, and the amplitude voltage inputted to the comparator <NUM> is less than the reference voltage, the resistance values of the resistors <NUM>, <NUM> and the grounding portion are not elevated, and the controller <NUM> therefore assesses that the electricity leakage sensing circuit <NUM> is normal.

When the positive-electrode switch <NUM> is on and the negative-electrode switch <NUM> is off, and the amplitude voltage inputted to the comparator <NUM> is equal to or greater than the reference voltage, and when the positive-electrode switch <NUM> is off and the negative-electrode switch <NUM> is on, and the amplitude voltage inputted to the comparator <NUM> is less than the reference voltage, the resistance values of the resistor <NUM> and the grounding portion are not elevated, but the resistance value of the resistor <NUM> is elevated. Therefore, the controller <NUM> assesses that a disconnection has occurred in the resistor <NUM>, and assesses that there is an abnormality on the positive-electrode side of the electricity leakage sensing circuit <NUM>.

When the positive-electrode switch <NUM> is on and the negative-electrode switch <NUM> is off, and the amplitude voltage inputted to the comparator <NUM> is less than the reference voltage, and when the positive-electrode switch <NUM> is off and the negative-electrode switch <NUM> is on, and the amplitude voltage inputted to the comparator <NUM> is equal to or greater than the reference voltage, the resistance values of the resistor <NUM> and the grounding portion are not elevated, but the resistance value of the resistor <NUM> is elevated. Therefore, the controller <NUM> assesses that a disconnection has occurred in the resistor <NUM>, and assesses that there is an abnormality on the negative-electrode side of the electricity leakage sensing circuit <NUM>.

When the positive-electrode switch <NUM> is on and the negative-electrode switch <NUM> is off, and the amplitude voltage inputted to the comparator <NUM> is equal to or greater than the reference voltage, and when the positive-electrode switch <NUM> is off and the negative-electrode switch <NUM> is on, and the amplitude voltage inputted to the comparator <NUM> is equal to or greater than the reference voltage, the resistance values of the resistors <NUM>, <NUM> are not elevated, but the resistance value of the grounding portion is elevated. Therefore, the controller <NUM> assesses that a disconnection has occurred in the grounding portion, and assesses that there is an abnormality in the grounding portion of the electricity leakage sensing circuit <NUM>.

Claim 1:
A power source device provided with an alternating-current power source (<NUM>) and a secondary cell (<NUM>) connected to the alternating-current power source (<NUM>), wherein the alternating-current power source (<NUM>) is grounded,
wherein:
- said power source device comprises:
- a first switch (<NUM>)
- configured to selectively connect or cut off said secondary cell (<NUM>) and said alternating-current power source (<NUM>),
- the first switch (<NUM>) being provided between said secondary cell (<NUM>) and said alternating-current power source (<NUM>); and
- a ground fault sensing means (<NUM>) connected to the secondary cell side from the first switch (<NUM>) to a ground power line that connects a negative pole side of the first switch (<NUM>) and a negative pole of the secondary cell (<NUM>); and
- said ground fault sensing means (<NUM>) is configured to sense a ground fault in said secondary cell (<NUM>) by sensing a reduction in insulation resistance of said secondary cell (<NUM>) when said first switch (<NUM>) is off,
- the ground fault is detected only in a state in which the alternating-current power source (<NUM>) is electrically insulated,
- an inverter (<NUM>) is comprised,
- said secondary cell (<NUM>) is connected to said alternating-current power source (<NUM>) via the inverter (<NUM>) configured to convert alternating-current electric power supplied from said alternating-current power source (<NUM>) into direct-current electric power and to output the direct-current electric power; and
- said first switch (<NUM>) is provided between said secondary cell (<NUM>) and said inverter (<NUM>),
characterized in that- the power source device comprises a DC/DC converter (<NUM>) and an electricity leakage sensing means (<NUM>),
- the electricity leakage sensing means (<NUM>) is electrically connected to each of a pair of power source lines between said first switch (<NUM>) and said inverter (<NUM>) via said a DC/DC converter (<NUM>),
- said electricity leakage sensing means (<NUM>) is configured to sense an electricity leakage by comparing an electric current to the ground on a positive pole side and an electric current to the ground on the negative pole side, and
- said ground fault sensing means (<NUM>) is configured to sense a disconnection in said electricity leakage sensing means (<NUM>) when said first switch (<NUM>) is on.