Precharge controller

A precharge controller includes a main contactor, a capacitor, a precharge contactor, a current sensor, and a control unit. When starting a power supply from a battery to load, the control unit starts precharging by closing the precharge contactor when a detected current is equal to a preset value or lower, determines completion of precharging when the detected current once equal to or exceeded a first threshold value falls to a second threshold value or lower, and closes the main contactor.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims the benefit of priority of Japanese Patent Application No. 2018-235469, filed on Dec. 17, 2018, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure generally relates to a precharge controller configured to precharge a smoothing capacitor connected in parallel with a load before closing a main contactor that conducts a power supply path from a battery to the load.

BACKGROUND INFORMATION

In the related art, a precharge controller includes (i) a main contactor provided in a power supply path from a battery to a load and (ii) a precharge contactor connected in parallel with the main contactor, and forming another power supply path via a current limiting resistor.

Then, when a power supply from the battery to the load is started, the precharge contactor is closed to start precharging to the smoothing capacitor connected in parallel with the load. After the start of precharging, it is determined whether or not the precharging current after a predetermined time from the start of precharging is equal to or less than a reference value. If the precharging current is equal to or less than the reference value, it is determined that the precharging is complete. Then, the main contactor is closed and the drive of the load is allowed.

Thus, when starting the power supply from the battery to the load, the reason for performing the precharging to the capacitor is to protect the main contactor by suppressing an inrush current that flows when the main contactor is closed.

However, in the related art, completion of precharging is determined based on a current value after a predetermined time from the start of precharging. Therefore, a determination regarding whether the precharging is complete is not appropriately performable when a current sensor fails.

That is, since the electric current cannot be detected when the current sensor is broken, the main contactor is closed in a state where the precharging is not complete, and a large current flows in the main contactor in such a state, which may cause the main contactor to fail.

SUMMARY

It is an object of the present disclosure to provide a precharge controller which closes a precharge contactor and precharges a capacitor before closing a main contactor, capable of preventing a false determination of completion of precharge even when a current sensor fails.

DETAILED DESCRIPTION

Hereinafter, an embodiment of the present disclosure is described with reference to the drawings.

A power supply system of the present embodiment shown inFIG. 1is to draw a power supply from the battery2mounted on an electric vehicle or a hybrid vehicle to a motor8serving as a power source of the vehicle through a positive terminal side power supply path4and a negative terminal side power supply path6, for a supply of electric power to an inverter10and the like that control a supply of electric current.

In addition to the inverter10, the power supply paths4and6on the positive terminal and negative terminal sides have, as a load, a DC/DC converter12converting a high voltage, for example, 250 V, supplied from the battery2to a predetermined low voltage, for example, 12 V, and other high voltage system components14connected thereto.

On the positive terminal side power supply path4and the negative terminal side power supply path6, a smoothing capacitor16is provided to absorb voltage fluctuations between the power supply paths4and6, as well as a voltage sensor18to detect a voltage across two terminals of the capacitor, respectively in parallel connection with the loads10to14.

In addition, a positive side contactor22and a negative side contactor24for connecting and disconnecting the power supply paths4and6are provided respectively on the positive and negative side power supply paths4and6from the battery2to the respective loads10to14including the capacitor16.

Therefore, a high voltage is applied from the battery2to the respective loads10to14including the capacitor16by closing the two contactors22and24and making the power supply paths4and6conductive.

Further, from among the two contactors22and24, the negative side contactor24has a precharge contactor28connected in parallel via a resistor26for limiting the electric current. In the present embodiment, the negative side contactor24corresponds to a main contactor of the present disclosure. In the following description, the positive side contactor22is described as SMR-B, the negative side contactor24is described as SMR-G, and the precharge contactor28is described as SMR-P. SMR is an abbreviation of system main relay.

Therefore, when the SMR-P28and the SMR-B22are closed, a power supply path to each of the loads10to14including the capacitor16is formed via the resistor26.

The SMR-P28forms a power supply path via the resistor26when the power supply system is activated, thereby supplying a charging current to the capacitor16for precharging the capacitor16. The SMR-P28is switched between ON/OFF states by an ECU30serving as a control unit, together with the SMR-B22and the SMR-G24.

The ECU30is an electronic control unit, and is configured to have a microcomputer including a CPU, a ROM, and a RAM. When an ignition switch, hereinafter referred to as IG-SW32, of the vehicle is in an ON state, the ECU30operates by receiving power supply from a low voltage battery mounted on the vehicle.

Further, when a starter switch, hereinafter referred to as ST-SW34of the vehicle is operated when the IG-SW32is in the ON state, the ECU30assumes that a start instruction of the power supply system is input, thereby performing a precharge control process shown inFIG. 2.

In addition, since the low voltage battery used as the power supply of the ECU30is charged by a low voltage generated by the DC/DC converter12, the ECU30is prevented from becoming inoperable due to the discharge of the low voltage battery.

Next, in addition to the above-described voltage sensor18, the IG-SW32, and the ST-SW34, a current sensor20and a notification unit36are connected to the ECU30.

The current sensor20is configured to detect the electric current flowing in a portion of the negative terminal side power supply path6connecting the SMR-G24and SMR-P28serving as the main contactor and the negative terminal of the battery2, that is, in a battery side portion of the path6.

Further, the notification unit36is a device for notifying abnormality when an abnormality of the current sensor20or the like is detected in a precharge control process described later. Such a notification for a driver of the vehicle may be provided by a warning sound generator for audible warning and/or a display unit for a display of contents of abnormality.

Then, the ECU30functions as the precharge controller of the present disclosure by performing the precharge control process shown inFIG. 2based on the detected current obtained as a detection signal of the current sensor20.

That is, the ECU30, which is the control unit of the present disclosure, performs a failure determination of the current sensor20and a precharge completion determination of the precharging to the capacitor16based on the electric current detected by the current sensor20in the precharge control process.

Further, the ECU30starts precharging to the capacitor16by closing the SMR-P28and SMR-B22in the precharging control process, and closes the SMR-G24when it is determined that the precharging is complete, and allows each of the load10to14to be driven.

Next, the precharge control process performed by the ECU30is described.

As shown inFIG. 2, when the precharge control process is started, first, in S110, it is determined whether or not the current value of the detected current detected by the current sensor20is equal to or less than a predetermined abnormality determination value.

That is, if the current sensor20is normal when both of the SMR-P28and the SMR-G24are in the open state, that is, in an OFF state, the current value detected by the current sensor20is “0.” Thus, in S110, based on the current value, it is determined whether the current sensor20is broken. Therefore, a predetermined current value near “0” or “0” itself is set as the abnormality determination value used in S110.

If it is determined in S110that the current value detected by the current sensor20exceeds the abnormality determination value, the process proceeds to S120, and it is determined that the current sensor20is broken, and a current sensor failure determination process is performed to notify the sensor failure by using the notification unit36.

Then, subsequently in S130, since the current sensor20is broken, the precharging to the capacitor16is prohibited, and the precharging control process is ended.

Next, when it is determined that the current value of the detected current detected by the current sensor20is equal to or less than the abnormality determination value in S110, it means that the current sensor20is normal, and thus the process proceeds to S140, and precharging is started. The start of precharging is caused by closing the SMR-P28and the SMR-B22, that is, by the turning ON of them, as shown inFIG. 3.

AlthoughFIG. 3describes that the SMR-P28and SMR-B22are sequentially, one by one, switched to the ON state when precharging is started at time t1, the SMR-P28and the SMR-B22may simultaneously be switched to the ON state. Alternatively, the SMR-B22and the SMR-P28may be switched to the ON state in this written order.

As described above, when precharging to the capacitor16is started in S140, the process proceeds to S150, and it is determined whether the current value of the detected current detected by the current sensor20is equal to or greater than the first threshold value set in advance for the precharge performance determination.

That is, as shown inFIG. 3, when SMR-B22and SMR-P28are turned ON and precharging is started at time t1, an electric current flows in the capacitor16, thereby the detected current steeply rises from “0” in region A to a large current in region B.

Therefore, in S150, it is determined whether the precharging to the capacitor16has started normally by determining whether the current value of the detected current has become equal to or greater than the first threshold value. When it is determined in S150that the current value of the detected current has become equal to or greater than the first threshold value, the process proceeds to S160, and it is determined whether the current value of the detected current detected by the current sensor20becomes equal to or less than a predetermined second threshold value for a precharge completion determination.

The process of S160is a process of determining that (i) the charging current to the capacitor16is lowered to near “0” in region C shown inFIG. 3by the precharging, and (ii) the precharging to the capacitor16is complete. Therefore, a current value smaller than the first threshold value used in the determination process in S150is set in advance as the second threshold value used in the determination process in S160. However, the second threshold value may be the same as the first threshold value.

Subsequently, when the current value of the current detected by the current sensor20becomes equal to or less than the second threshold value, and it is determined in S160that the precharging is complete, the process proceeds to S170and the SMR-G24is switched to the ON state. As a result, an electric power can be supplied to each of the loads10to14and the capacitor16through the power supply paths4and6without limiting the electric current by the resistor26.

Note that in S170, as shown inFIG. 3, the SMR-G24as a main contactor is turned ON at time t2in accordance with the completion determination of precharging, and then the SMR-P28is turned OFF to allow drive of each of the load10to14.

Next, when it is determined in S150that the current value of the detected current is less than the first threshold value, the process proceeds to S180, and it is determined whether or not a first determination time of preset duration for a precharge performance determination has elapsed after precharging is started in S140.

When it is determined in S180that the first determination time has not elapsed, the process proceeds to S150, and when it is determined that the first determination time has elapsed, the process proceeds to S190. In S190, since the detected current does not become equal to or greater than the first threshold value even after the first determination time has elapsed after the start of precharging, it is determined that either the current sensor20or the power supply paths4and6has an abnormality, and an abnormality notification is performed via the notification unit36.

Then, subsequently in S200, since there is an abnormality in the current sensor20or the power supply paths4and6, all the SMR-B22, SMR-G24, and SMR-P28are turned OFF to stop the precharging, and the precharge control process is ended.

When it is determined in S160that the current value of the detected current exceeds the second threshold value, the process proceeds to S210, and it is determined whether a second determination time of preset duration for a precharge completion determination has elapsed after precharging is started in S140.

When it is determined in S210that the second determination time has not elapsed, the process proceeds to S160, and when it is determined that the second determination time has elapsed, the process proceeds to S220. Needless to say, a duration longer than the first determination time is set as the second determination time.

In S220, it is determined that a power consumption abnormality is caused due to the load of the high voltage system components14and the like connected to the power supply paths4and6, and the notification regarding the situation is provided via the notification unit36. Then, subsequently in S230, since the power consumption abnormality due to the load of the high voltage system components14and the like has occurred, all of the SMR-B22, SMR-G24and SMR-P28are turned OFF to stop the precharging, and the precharge control process is ended.

As described above, the ECU30performs the precharge control process immediately after the activation of the power supply system. Then, in the precharge control process, the capacitor16is precharged by closing the SMR-P28and the SMR-B22, and after the precharge is complete, the SMR-G24is closed to allow the drive of the load.

Therefore, according to the present embodiment, by precharging the capacitor16, a flow of a large current to the SMR-B22and the SMR-G24is prevented, thereby preventing the failure of the SMR-B22and the SMR-G24

Further, the ECU30determines, before starting the precharging, whether or not the current sensor20is abnormal by determining whether the current value detected by the current sensor20is equal to or less than the abnormality determination value. When it is determined that the current sensor20is abnormal in the above-described manner, notification regarding such determination is provided for the driver, for example, and precharging is prohibited.

Therefore, a problematic situation, in which precharging is started when not noticing that the current sensor20is broken and end of precharging is undeterminable based on the detected current detected by the current sensor is prevented.

That is, in the above-described related art device, precharging is started without determining the failure of the current sensor, and, if the current value detected after a predetermined time has elapsed is equal to or less than the predetermined threshold for precharge completion determination, it is assumed that precharging is complete, and the main contactor is made conductive.

Therefore, in the related art device, as shown inFIG. 4, the main contactor may be turned ON at time t2when a predetermined time has elapsed after the start of precharging, even though the capacitor has not yet sufficiently been precharged. When the main contactor is turned ON in such manner, a large current flows due to a voltage difference between the capacitor and the battery, and the main contactor may be broken.

On the other hand, in the present embodiment, the failure determination of the current sensor20is performed before starting the precharging, and the precharging is prohibited when the current sensor20is determined as failed, thereby the occurrence of an above-described problem is preventable. Further, the occupant of the vehicle can detect the failure of the current sensor20by the notification from the notification unit36, and is prompted to replace the broken component with a normal component.

Next, after the precharging is started, the ECU30determines that the precharging is complete when the current detected by the current sensor20once becomes the first threshold value or more and then becomes the second threshold value or less, thereby turns ON SMR-G24and allows the drive of the load.

Therefore, according to the present embodiment, the precharge completion determination after the start of precharging can be performed more accurately than the related art device described above, for the turning ON of the SMR-G24that serves as a main contactor.

Therefore, according to the present embodiment, by preventing a false determination of the completion of precharging, a problem accompanying the false determination of the completion of precharging, such as a large current flowing in the SMR-G24due to the turning ON of the SMR-G24at a wrong timing, is preventable, thereby preventing the failure of the SMR-G24.

Further, when the current value does not become equal to or greater than the first threshold value even after the lapse of the first determination time from the start of precharging, the ECU30determines that an abnormality has occurred in the current sensor20or in the power supply paths4and6, thereby cancelling the precharging and notifying such abnormality to the occupant of the vehicle.

Further, even after normally starting the precharging, if the current value does not fall below the second threshold value before the lapse of the second determination time from the start of precharging, it is determined by the ECU30that a power consumption abnormality by the load has been caused. Then, such an abnormality determined in the above is notified to the occupant of the vehicle, with the cancellation of the precharging.

Therefore, according to the present embodiment, when any of the current sensor20, the power supply paths4and6, and the load is abnormal, not only stopping the precharging and interrupting the power supply paths4and6, but also notification to the vehicle occupant of a suspected failed component is performed for prompting the repair of the vehicle.

While one embodiment of the present disclosure has been described above, the present disclosure is not limited to the embodiment described above and can be carried out with various modifications.

For example, in the above embodiment, when it is determined in S110that the current value exceeds the abnormality determination value in the precharge control process, the process proceeds to S120and the failure of the current sensor20is determined.

On the other hand, if it is determined in S110that the current value exceeds the abnormality determination value, it may be determined whether or not a predetermined time has elapsed after the start of the precharge control process, and, when the predetermined time has not yet elapsed, the determination process of S110may be performed again. In such manner, even when the output of the current sensor20temporarily becomes unstable immediately after the start of the power supply system, the erroneous determination of the failure of the current sensor20in S120is preventable.

Further, in the above embodiment, the main contactor with which the SMR-P28, i.e., a precharge contactor, is connected in parallel, is described as the SMR-G24provided in the power supply path6on the negative terminal side.

On the other hand, the main contactor with which the SMR-P28is connected in parallel may be the SMR-B22provided in the power supply path4on the positive terminal side. In this case, precharging to the capacitor16may be performed by the turning ON of both of the SMR-P28and the SMR-G24, and the SMR-B22may be turned ON after the precharge completion determination, for obtaining the same effects as the above embodiment.

Further, in the above embodiment, it is described that the ECU30as the control unit is configured as having a microcomputer, and the function as the control unit is realized by the precharge control process which is performed by the ECU30, such as by an execution of a computer program. On the other hand, the control unit of the present disclosure may be configured to realize part or all of the functions by using a plurality of hardware components.

Further, a plurality of functions of one component in the above embodiment may be realized by a plurality of components, or one function of one component may be realized by a plurality of components. Further, a plurality of functions of a plurality of elements may be implemented by one element, or one function implemented by a plurality of elements may be implemented by one element. A part of the configuration of the above embodiment may be omitted. At least a part of the configuration of the above embodiment may be added to or replaced with a different part of the configuration of the above embodiment.

Further, the present disclosure may be realized in various forms, other than a precharge controller used for a power supply system of a vehicle, such as a program for causing a computer to function as a control unit of the precharge controller, a non-transitory, substantial storage medium such as a semiconductor memory for storing such a program, a precharge control method and the like.