Power supply control device

Abstract

To determine a sign of welding of a relay.SOLUTION: A control device of a power supply device executes precharge of controlling a relay and a power supply circuit so that voltage of a second power line in a state where the relay is turned OFF may be voltage between terminals of a DC power supply when the relay is turned ON from OFF, and controls the relay to turn ON after the precharge is completed. Based on a histogram which makes a voltage difference a rank as a difference between the voltage of the second power line after the precharge is completed and before the relay is turned ON, and the voltage of the second power line after the relay is turned ON, a sign of welding of the relay is determined.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control device for a power supply device, and more particularly to a control device for a power supply device that is mounted on a power supply device that includes a DC power supply, an electric circuit, a relay, a power supply circuit, and a capacitor. [Background technology]

[0002] Conventionally, as a control device for this type of power supply device, a device mounted on a power supply device (power supply system) including a DC power supply (battery), an electric circuit (DC / DC converter), a relay (two contactors on the positive and negative sides), a power supply circuit (pre-charge contactor and resistor section), and a capacitor has been proposed (see, for example, Patent Document 1). The electric circuit receives power from the DC power supply. The relay connects and disconnects a first power line from the DC power supply and a second power line (positive and negative current supply paths) from the electric circuit. The power supply circuit is capable of supplying power to the second power line when the relay is off. The capacitor is connected to the positive line (positive current supply path) and negative line (negative current supply path) of the second power line. When the control device of this power supply device switches the relay from off to on, it executes a precharge that controls the relay and the power supply circuit so that the voltage of the second power line becomes the terminal voltage of the DC power supply while the relay is off, and switches the relay on after executing the precharge. In the precharge, it is determined that the precharge is completed when a set time has elapsed since the voltage difference between the terminal voltage of the DC power supply and the voltage of the second power line becomes equal to or less than a set voltage. The set voltage is set using a maximum error based on the maximum value of the detection error of the terminal voltage of the DC power supply and the voltage of the second power line. The set time is set based on the time constant for charging the capacitor by the power supply circuit, the maximum error of the voltage difference, and the withstand voltage of the relay. This makes it possible to perform the precharge so that the voltage difference does not exceed the withstand voltage of the relay. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-137334 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the above-mentioned power supply control device, even if it is determined that precharging is complete, due to detection errors of the terminal voltage of the DC power supply and the capacitor voltage, the voltage difference may not actually be 0, and a current may be generated when the relay is connected, causing stress that roughens the contacts. Such stress may cause the relay to weld in the future. Therefore, it is desirable to be able to determine the signs of relay welding.

[0005] The main object of the control device for a power supply device of the present invention is to determine a sign of relay welding. [Means for solving the problem]

[0006] The power supply control device of the present invention employs the following means to achieve the above-mentioned main object.

[0007] The control device for a power supply device of the present invention comprises: A DC power source; an electric circuit that receives power from the DC power source; a relay that connects and disconnects a first power line from the DC power source and a second power line from the electric circuit; a power supply circuit capable of supplying power to the second power line when the relay is in an off state; a capacitor attached to the positive line and the negative line of the second power line; The power supply device includes: a control device for a power supply device, which executes a precharge to control the relay and the power supply circuit when the relay is turned on from an off state so that a voltage of the second power line becomes a voltage between terminals of the DC power supply while the relay is in an off state, and controls the relay to be turned on after the precharge is completed, A sign of welding of the relay is determined based on a histogram in which a voltage difference, which is a difference between a voltage of the second power line after the precharge is completed and before the relay is turned on, and a voltage of the second power line after the relay is turned on, is classified. The gist of the present invention is as follows.

[0008] In the control device for the power supply device of the present invention, a sign of welding of the relay is judged based on a histogram in which a voltage difference is classified as a difference between the voltage of the second power line after completion of precharging and before turning on the relay, and the voltage of the second power line after turning on the relay. The inventors have found that the shape of the histogram in which the voltage difference is classified changes depending on the state of stress on the relay. Therefore, the state of stress on the relay can be judged based on the histogram in which the voltage difference is classified. As a result, a sign of welding of the relay can be judged.

[0009] In the control device for a power supply device of the present invention, it may be determined that there is a sign of welding of the relay when the kurtosis when the first histogram is regarded as a normal distribution is a negative value, or it may be determined that there is a sign of welding of the relay when the ratio of the number of occurrences in which the voltage difference is included in a class in which the voltage difference is less than a predetermined voltage to the number of occurrences in which the voltage difference is included in a class in which the voltage difference is equal to or greater than a predetermined voltage in the first histogram is equal to or greater than a predetermined value. In this way, it is possible to more appropriately determine the sign of welding of the relay.

[0010] Furthermore, in the control device for a power supply device of the present invention, the power supply circuit may have an auxiliary power source different from the DC power source, and a voltage conversion circuit that converts the voltage of power from the auxiliary power source and supplies the power to the second power line, and may be a circuit in which a charging relay is connected via a resistor between a negative line of the first power line and a negative line of the second power line, or between a positive line of the first power line and a positive line of the second power line. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram showing an outline of the configuration of an electric vehicle 20 equipped with a control device for a power supply device as one embodiment of the present invention. [Diagram 2] 4 is a flowchart showing an example of a determination routine executed by the ECU 70. [Diagram 3] FIG. 11 is an explanatory diagram showing an example of a frequency distribution of a voltage difference ΔVL. [Figure 4] FIG. 11 is an explanatory diagram showing an example of a second histogram. [Diagram 5] FIG. 13 is an explanatory diagram showing an example of a histogram (third histogram) in the case where there is a large deviation between voltage VL detected by voltage sensor 39a and the actual voltage of capacitor 39 (the voltage of low-voltage side power line 38b). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Next, a mode for carrying out the present invention will be described using examples. EXAMPLES

[0013] 1 is a schematic diagram showing the configuration of an electric vehicle 20 equipped with a power supply device control device as one embodiment of the present invention. As shown in the figure, the electric vehicle 20 equipped with the power supply device of the embodiment includes a motor 32, an inverter 34, a battery 36 as a DC power source, a system main relay SMR, an auxiliary battery 40 and a DC / DC converter 48 as a power supply circuit, a step-up / step-down converter 50, and an electronic control unit (hereinafter referred to as "ECU") 70. The ECU 70 mainly serves as the control device for the power supply device of the embodiment.

[0014] The motor 32 is configured as a synchronous generator motor, and includes a rotor in which a permanent magnet is embedded in a rotor core, and a stator in which a three-phase coil is wound around a stator core. The rotor of the motor 32 is connected to a drive shaft 26 that is connected to the drive wheels 22a, 22b via a differential gear 24. The inverter 34 is connected to the motor 32 and to a high-voltage power line 38a, and is configured as a well-known inverter circuit having six transistors and six diodes. The motor 32 is driven to rotate by switching control of a plurality of switching elements (not shown) of the inverter 34. The inverter 34 is connected to the ECU 70 via a communication line (for example, a communication line for CAN communication).

[0015] The step-up / step-down converter 50 is connected to the high-voltage power line 38a and the low-voltage power line (second power line) 38b, and is configured as a well-known step-up / step-down converter circuit having two transistors and two diodes constituting an upper arm and a lower arm, and a reactor. The step-up / step-down converter 50 boosts the power of the low-voltage power line 38b and supplies it to the high-voltage power line 38a, or reduces the voltage of the high-voltage power line 38a and supplies it to the low-voltage power line 38b, by adjusting the ratio of the on-time of the two transistors constituting the upper and lower arms by the ECU 70. Although not shown, smoothing capacitors are attached to the positive and negative lines of the high-voltage power line 38a. A smoothing capacitor 39 is attached to the positive and negative lines of the low-voltage power line 38b.

[0016] The battery 36 is configured as, for example, a lithium ion secondary battery or a nickel-hydrogen secondary battery with a rated voltage of about several hundred volts.

[0017] The system main relay (relay) SMR is connected to the battery side power line (first power line) 37 from the battery 36 and the low-voltage side power line 38b. The system main relay SMR has a positive side relay SMRB provided on the positive line of the battery side power line 37 and the positive line of the low-voltage side power line 38b, and a negative side relay SMRG provided on the negative line of the battery side power line 37 and the negative line of the low-voltage side power line 38b. The system main relay SMR connects and disconnects the battery side power line 37 and the low-voltage side power line 38b by turning on and off. The system main relay SMR is connected to the ECU 70 via a communication line (for example, a communication line for CAN communication).

[0018] The auxiliary battery 40 is configured as, for example, a lithium ion secondary battery, a nickel-hydrogen secondary battery, or a lead-acid battery with a rated voltage of about ten volts, and is connected to the auxiliary power line 42 together with the auxiliary equipment, DC / DC converter 48, and ECU 70 (not shown).

[0019] DC / DC converter 48 is connected to low-voltage side power line 38b and auxiliary side power line 42. DC / DC converter 48 steps down the power of low-voltage side power line 38b and supplies it to auxiliary side power line 42, and steps up the power of auxiliary side power line 42 and supplies it to low-voltage side power line 38b. DC / DC converter 48 is connected to ECU 70 and the like via a communication line (for example, a communication line for CAN communication).

[0020] Although not shown, the ECU 70 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a ROM for storing processing programs, a RAM for temporarily storing data, a flash memory for storing and holding data, an input / output port, and a communication port. The ECU 70 is connected to the inverter 34, the system main relay SMR, the DC / DC converter 48, and the step-up / step-down converter 50 via communication lines (for example, communication lines for CAN communication).

[0021] Signals from various sensors are input to the ECU 70 via input ports. Examples of signals input to the ECU 70 include a rotational position θm from a rotational position detection sensor (e.g., resolver) 32a that detects the rotational position of the rotor of the motor 32, a voltage (terminal voltage of the battery 36) Vb from a voltage sensor 36a attached between the terminals of the battery 36, and a current Ib from a current sensor 36b attached to the output terminal of the battery 36. Also included is a voltage VL of the capacitor 39 (low-voltage side power line 38b) from a voltage sensor 39a attached between the terminals of the capacitor 39. Other examples include an ignition signal from an ignition switch 80, a shift position SP from a shift position sensor 82 that detects the operation position of a shift lever 81, an accelerator opening Acc from an accelerator pedal position sensor 84 that detects the depression amount of an accelerator pedal 83, a brake pedal position BP from a brake pedal position sensor 86 that detects the depression amount of a brake pedal 85, and a vehicle speed V from a vehicle speed sensor 87. The operating positions of the shift lever 81 (shift position SP detected by the shift position sensor 82) include a parking position (P position), a reverse position (R position), a neutral position (N position), a forward position (D position), etc.

[0022] Various control signals are output via an output port from the ECU 70. Examples of the signals output from the ECU 70 include a control signal to a transistor of the inverter 34, a control signal to the system main relay SMR, a control signal to the DC / DC converter 48, and a control signal to the step-up / step-down converter 50.

[0023] In the electric vehicle 20 of the embodiment thus configured, when the system main relay SMR is turned on from off, for example, when the ignition signal from the ignition switch 80 is turned on from off, a precharge is executed to control the system main relay SMR and the DC / DC converter 48 so that the voltage VL of the capacitor 39 detected by the voltage sensor 39a becomes the voltage Vb of the battery 36 detected by the voltage sensor 36a while the system main relay SMR is in an off state. Then, when a predetermined time tref has elapsed after the voltage VL of the capacitor 39 detected by the voltage sensor 39a becomes the voltage Vb of the battery 36 detected by the voltage sensor 36a, that is, after the completion of the precharge, the system main relay SMR is turned on and the DC / DC converter 48 is controlled so that the auxiliary battery 40 is charged. Note that the time tref may be a value of 0, and in this case, the system main relay SMR is turned on immediately after the completion of the precharge.

[0024] Next, an operation of the electric vehicle 20 of the embodiment thus configured, in particular, an operation when determining whether there is a sign of welding of the system main relay SMR, will be described. Fig. 2 is a flowchart showing an example of a determination routine executed by the ECU 70. This routine is executed when the above-mentioned pre-charge is started.

[0025] When this routine is executed, the CPU of the ECU 70 determines whether or not the precharge is completed (step S100). If the precharge is not completed, the CPU waits until the precharge is completed.

[0026] When the pre-charging is completed in step S100, the voltage VL of the capacitor 39 is input (step S110), and the input voltage VL is set to the pre-on voltage Vbefore (step S120). The voltage VL is input as a value detected by the voltage sensor 39a.

[0027] Next, it is determined whether the system main relay SMR is on or not (step S130). When the system main relay SMR is off, the process returns to step S110, and steps S110 to S130 are repeated until the system main relay SMR is turned on. Therefore, the pre-on voltage Vbefore is set to the voltage VL after the precharge is completed and before the system main relay SMR is turned on.

[0028] When the system main relay SMR is turned on, the voltage VL of the capacitor 39 is input (step S140) in the same process as in step S110, and the input voltage VL is set as the after-on voltage Vafter (step S150). Then, a voltage difference ΔVL is calculated by subtracting the before-on voltage Vbefore set in step S110 from the set after-on voltage Vafter (step S160).

[0029] After the voltage difference ΔVL is calculated, the frequency distribution of the voltage difference ΔVL is then updated (a frequency distribution is created if one has not yet been created) (step S170). FIG. 3 is an explanatory diagram showing an example of the frequency distribution of the voltage difference ΔVL. As shown in the figure, the frequency distribution is updated (created) by dividing the voltage difference into multiple intervals for each predetermined voltage width (such as 10 V in this embodiment) and increasing the number of times for the class to which the calculated voltage difference ΔVL belongs by a value of 1. In the frequency distribution, the interval where the voltage difference ΔVL includes the value 0 (the interval where the voltage difference ΔVL is greater than -5 V and equal to or less than 5 V in this embodiment) is placed in the center.

[0030] After updating the frequency distribution in this way, it is determined whether the number of data N, which is the total number of data included in the frequency distribution, is equal to or greater than a predetermined number Nref (step S180). The predetermined number Nref is a threshold for determining whether the number of data N has reached a number sufficient to reduce statistical error, and is set to, for example, 100, 200, 300, etc. When the number of data N is less than the predetermined number Nref, this routine is terminated.

[0031] When the number of data N is equal to or greater than the predetermined number Nref, a first histogram is created from the frequency distribution (step S190), and a welding sign determination is performed to determine whether or not there is a sign of welding in the system main relay SMR based on the first histogram (step S200), and this routine ends. The welding sign determination is performed by examining the shape of the first histogram.

[0032] 4 is an explanatory diagram showing an example of the second histogram. The second histogram is a histogram determined in advance by experiment, analysis, etc., as a histogram in which the voltage difference between the voltage of the capacitor 39 before and after the system main relay SMR is turned on after the completion of precharging is classified when the detection error of the voltage sensor 36a or the voltage sensor 39a is small. When the detection error of the voltage sensor 36a or the voltage sensor 39a is small, the deviation between the voltage Vb of the battery 36 detected by the voltage sensor 36a and the actual voltage of the battery 36 and the deviation between the voltage VL detected by the voltage sensor 39a and the actual voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b) are small. Therefore, the difference between the voltage of the battery 36 and the voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b) before and after the system main relay SMR is turned on after the pre-charging is completed is small, and if the class of the voltage difference ΔVL including the value 0 is placed in the center of the second histogram as shown in the figure, the data will be concentrated near the center and the distribution will have a heavy tail. If the second histogram is considered to be a normal distribution, the kurtosis will be large and the value will be positive. In this case, it can be determined that the current generated when the system main relay SMR is connected is small, the stress on the system main relay SMR that roughens the contacts is small, and there is no sign of the system main relay SMR welding.

[0033] FIG. 5 is an explanatory diagram showing an example of the third histogram. The third histogram is a histogram determined in advance by experiments, analysis, etc. as a histogram in which the voltage difference between the voltage of the capacitor 39 before and after the system main relay SMR is turned on after the completion of precharging when the detection error of the voltage sensor 36a or the voltage sensor 39a is large is a class. When the detection error of the voltage sensor 36a or the voltage sensor 39a is large, the deviation between the voltage VL detected by the voltage sensor 39a and the actual voltage of the capacitor 39 (the voltage of the low-voltage side power line 38b) becomes large. Therefore, the number of times when the difference between the voltage of the battery 36 before and after the system main relay SMR is turned on after the completion of precharging becomes large increases, and in the third histogram, as shown in the figure, if the class including the voltage difference ΔVL value 0 is placed in the center, the data will be scattered as a whole and the distribution will have a shape with a light tail. If the third histogram is considered to be a normal distribution, the kurtosis will be small and negative. In this case, the current generated when the system main relay SMR is connected is large, and the stress on the system main relay SMR that causes the contacts to become rough is large, so it can be determined that there are signs that the system main relay SMR may weld.

[0034] In this way, by examining the shape of the histogram which is classified based on the voltage difference between the voltages of the capacitor 39 before and after the system main relay SMR is turned on after the precharging is completed, it is possible to determine whether or not the system main relay SMR is heavily stressed, i.e., whether or not there is a sign that the system main relay SMR will melt.For these reasons, in the embodiment, by examining the shape (kurtosis) of the first histogram, it is determined whether or not there is a sign that the system main relay SMR will melt.

[0035] In the welding sign determination in step S200, when the kurtosis K1 of the first histogram is equal to or greater than 0, it is determined that the shape of the first histogram is close to the shape of the second histogram, and it is determined that there is no sign of welding of the system main relay SMR. When the kurtosis K1 of the first histogram is less than 0, it is determined that the shape of the first histogram is close to the shape of the third histogram, and it is determined that there is a sign of welding of the system main relay SMR. In this way, by checking the shape (kurtosis Sp1) of the first histogram, it is possible to determine the presence of a sign of welding of the system main relay SMR.

[0036] According to the electric vehicle 20 equipped with the control device for the power supply device of the embodiment described above, it is possible to determine the sign of welding of the system main relay SMR by determining the sign of welding of the system main relay SMR based on the first histogram that classifies the voltage difference ΔVL as the difference between the pre-on voltage Vbefore and the post-on voltage Vafter.

[0037] In electric vehicle 20 equipped with the control device for the power supply device of the embodiment, in step S200, a sign of welding is determined by examining kurtosis Sp1 of the first histogram. However, instead of examining kurtosis Sp1 of the first histogram, a ratio of the number of times (frequency) of a section in which the voltage difference ΔVL of the first histogram includes a value of 0 (in the embodiment, a section in which the voltage difference ΔVL is greater than -5 V and equal to or less than 5 V) to the total number of times of other sections may be calculated, and if this ratio is large, it may be determined that there is a sign of welding of the system main relay SMR.

[0038] In the electric vehicle 20 equipped with the control device for the power supply device of the embodiment, in pre-charge, the system main relay SMR and the DC / DC converter 48 are controlled so that the voltage VL of the capacitor 39 becomes the voltage Vb of the battery 36 when the system main relay SMR is in an off state. However, a charging relay may be connected between the negative electrode line of the battery side power line 37 and the negative electrode line of the low-voltage side power line 38b or between the positive electrode line of the battery side power line 37 and the positive electrode line of the low-voltage side power line 38b via a resistor, and in pre-charge, one of the positive electrode side relay SMRB and the negative electrode side relay SMRG that is not connected to the charging relay may be turned on and the other relay that is connected to the charging relay may be turned off, and the charging relay may be turned on to supply power from the battery 36 to the capacitor 39, thereby making the voltage VL of the capacitor 39 the voltage Vb of the battery 36.

[0039] In the embodiment, a case is illustrated where the control device for a power supply device of the present invention is applied to an electric vehicle 20. However, the control device for a power supply device of the present invention may be applied to any vehicle equipped with a power supply device including: a DC power supply, an electric circuit receiving power from the DC power supply, a relay for connecting and disconnecting a first power line from the DC power supply and a second power line from the electric circuit, a power supply circuit capable of supplying power to the second power line when the relay is off, capacitors attached to the positive and negative lines of the second power line, and a voltage sensor for detecting the voltage of the second power line.

[0040] The correspondence between the main elements of the embodiment and the main elements of the invention described in the Summary of the Invention section will be described below. In the embodiment, the ECU 70 corresponds to the "control device for the power supply device."

[0041] The correspondence between the main elements of the Examples and the main elements of the invention described in the Summary of the Problem column does not limit the elements of the invention described in the Summary of the Problem column, since the Examples are examples for specifically explaining the mode for implementing the invention described in the Summary of the Problem column. In other words, the interpretation of the invention described in the Summary of the Problem column should be based on the description in that column, and the Examples are merely a specific example of the invention described in the Summary of the Problem column.

[0042] Although the form for carrying out the present invention has been described above using examples, the present invention is not limited to these examples in any way, and it goes without saying that the present invention can be carried out in various forms without departing from the scope of the gist of the present invention. [Industrial Applicability]

[0043] The present invention can be used in the manufacturing industry of control devices for power supplies. [Explanation of symbols]

[0044] 20 electric vehicle, 22a, 22b drive wheels, 24 differential gear, 26 drive shaft, 32 motor, 34 inverter, 36 battery, 36a voltage sensor, 36b current sensor, 37 battery side power line, 38a high voltage side power line, 38b low voltage side power line, 39 capacitor, 39a voltage sensor, 40 auxiliary battery, 42 auxiliary side power line, 48 DC / DC converter, 50 step-up / step-down converter, 70 ECU, 80 ignition switch, 81 shift lever, 82 shift position sensor, 83 accelerator pedal, 84 accelerator pedal position sensor, 85 brake pedal, 86 brake pedal position sensor, 87 vehicle speed sensor, SMR system main relay, SMRB positive side relay, SMRG negative side relay.

Claims

[Claim 1] A DC power source; an electric circuit that receives power from the DC power source; a relay for connecting and disconnecting a first power line from the DC power source and a second power line from the electric circuit; a power supply circuit capable of supplying power to the second power line when the relay is in an off state; a capacitor attached to a positive line and a negative line of the second power line; The power supply device includes: a control device for a power supply device, which executes a precharge to control the relay and the power supply circuit when the relay is switched from off to on so that a voltage of the second power line becomes a voltage between terminals of the DC power supply while the relay is in an off state, and controls the relay to be on after the precharge is completed, A sign of welding of the relay is determined based on a histogram in which a voltage difference, which is a difference between a voltage of the second power line after the precharge is completed and before the relay is turned on, and a voltage of the second power line after the relay is turned on, is classified. A control device for a power supply.

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