JP2011250511A - Load driving device and vehicle with the same, and method for control of load driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly protect a voltage boosting converter and an energy storage apparatus without unnecessarily limiting a running performance in a load driving device with the voltage boosting converter.SOLUTION: A controller determines a current threshold Ith1 for protecting the energy storage apparatus (S40). The controller determines a current threshold Ith2 for protecting a diode in the voltage boosting converter based on a detection value from a cooling water temperature sensor for detecting a cooling water temperature in the voltage boosting converter (S50). The controller sets a lower one of the current thresholds Ith1, Ith2 as an excess current threshold (S60-S80), and implements an excess current FB control based on the set excess current threshold (S100).

Description

  The present invention relates to a load drive device, a vehicle including the load drive device, and a control method for the load drive device, and more particularly, to an overcurrent prevention technique for the load drive device.

  Japanese Patent Laying-Open No. 2006-25493 (Patent Document 1) discloses a power conversion device that limits an output current at the time of overload to prevent overheat destruction of an element. In this power converter, when current value I indicated by the output current of the inverter exceeds threshold value Ith1, it is determined that the current is concentrated. The shortest time when the current value I exceeds Ith_max, the longer the current limit time is set as the current value I becomes smaller. Further, the current limit time is set longer as the cooling water temperature of the inverter is lower. For example, when the current value I exceeds Ith_max and the coolant temperature is Tw2 lower than Tw3, the current limit time is set to Δt1 (Tw2) longer than Δt1 (Tw3).

  According to this power conversion device, the device capability can be sufficiently exhibited while preventing overheating of the power element due to overload (see Patent Document 1).

JP 2006-25493 A

  The power converter disclosed in the above Japanese Patent Application Laid-Open No. 2006-25493 is useful in that it can prevent the elements of the inverter from being overheated at the time of overload.

  On the other hand, when a boost converter is provided between the DC power supply and the inverter, the elements of the boost converter (especially, the power element of the upper arm that flows current from the DC power supply to the inverter during the power running operation of the motor) are also protected from overheat destruction Must. At that time, in order not to unnecessarily deteriorate the running performance of the vehicle, it is necessary to consider not to limit the current unnecessarily. In addition, it is necessary to consider the DC power supply (power storage device such as a secondary battery) that supplies power to the boost converter so that no overcurrent occurs. In the above Japanese Patent Laid-Open No. 2006-25493, such a point is not studied.

  Therefore, an object of the present invention is to appropriately protect a boost converter and a power storage device without unnecessarily restricting running performance in a load drive device including the boost converter.

  According to the present invention, the load driving device includes a power storage device, a driving device, a boosting device, a current sensor, a refrigerant temperature sensor, and a control device. The drive device drives the load using electric power output from the power storage device. The booster device is provided between the power storage device and the drive device, and is configured to be able to boost the input voltage of the drive device to be higher than the voltage of the power storage device. The current sensor is for detecting a current supplied from the power storage device to the drive device. The refrigerant temperature sensor is for detecting the temperature of the refrigerant for cooling the booster. When the detected value of the current sensor exceeds the control threshold value, the control device executes excess current feedback control for controlling the current based on the detected value. The booster device includes a power semiconductor element that allows current to flow from the power storage device to the drive device. Then, the control device outputs a second current determined based on a first current threshold value set to protect the power storage device and a detection value of the refrigerant temperature sensor to protect the power semiconductor element. Excess current feedback control is executed using the smaller one of the threshold values as a control threshold value.

  Preferably, the second current threshold is set to be smaller as the detected value of the refrigerant temperature sensor is larger.

  Preferably, the load driving device further includes an annealing processing unit. The annealing processing unit performs an annealing process on the detection value of the current sensor. The control gain of the excess current feedback control is set to a value larger than the first reference value. The time constant of the annealing process is set to a value larger than the second reference value corresponding to the first reference value.

  Preferably, the boosting device further includes first and second power semiconductor switching elements and a reactor. The first and second power semiconductor switching elements are connected in series between a pair of power lines connected to the driving device. The reactor is connected between a connection node between the first and second power semiconductor switching elements and the positive electrode of the power storage device. The power semiconductor element is a diode. The diode is connected in antiparallel to the first power semiconductor switching element constituting the upper arm.

  According to the invention, the vehicle includes any one of the load driving devices described above, an electric motor driven by the load driving device, and driving wheels driven by the electric motor.

  According to the invention, the control method is a control method for the load driving device. The load driving device includes a booster. The booster is provided between the drive device that drives the load and the power storage device, and is configured to be able to boost the input voltage of the drive device to be higher than the voltage of the power storage device. The booster device includes a power semiconductor element that allows current to flow from the power storage device to the drive device. The control method includes a step of detecting a current supplied from the power storage device to the drive device, a step of detecting a temperature of a refrigerant for cooling the booster, and a detected value of the current exceeds a control threshold value. And performing overcurrent feedback control for controlling current based on the detected value. The step of executing the excess current feedback control includes a sub-step of determining a first current threshold value for protecting the power storage device, and a detected temperature value of the refrigerant for protecting the power semiconductor element. And a sub-step of executing excess current feedback control using the smaller one of the first and second current thresholds as a control threshold.

  Preferably, the second current threshold is set so as to decrease as the detected temperature value increases.

  Preferably, the method for controlling the load driving device further includes a step of executing an annealing process on the detected current value. The control gain of the excess current feedback control is set to a value larger than the first reference value. The time constant of the annealing process is set to a value larger than the second reference value corresponding to the first reference value.

  In the present invention, a booster device is provided between the power storage device and the drive device, and the booster device includes a power semiconductor element that allows current to flow from the power storage device to the drive device. Then, when the detected value of the current sensor exceeds the control threshold value, excess current feedback control is performed to control the current based on the detected value. Here, in the present invention, it is determined based on the first current threshold value defined for protecting the power storage device and the detected value of the refrigerant temperature sensor for protecting the power semiconductor element of the booster device. Since the excess current feedback control is executed using the smaller one of the second current threshold values as the control threshold value, current limitation is appropriately performed according to the situation.

  Therefore, according to the present invention, the boost converter and the power storage device can be appropriately protected without unnecessarily limiting the running performance.

1 is an overall configuration diagram of a vehicle including a load driving device according to Embodiment 1 of the present invention. It is the figure which showed the temperature change of the diode in the upper arm of a boost converter. It is the figure which showed the relationship between the cooling water temperature of a boost converter, and the electric current maximum value which can be sent through a diode. It is a functional block diagram of the part relevant to excess current FB control of the control apparatus shown in FIG. It is a flowchart for demonstrating the specific process sequence regarding the excess current FB control performed by the control apparatus. 10 is a flowchart for explaining a specific processing procedure related to excess current FB control executed by the control device in the second embodiment. It is the figure which showed the behavior of the electric current.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
1 is an overall configuration diagram of a vehicle provided with a load driving apparatus according to Embodiment 1 of the present invention. Referring to FIG. 1, vehicle 100 includes a power storage device B, a boost converter 10, an inverter 20, a motor generator 30, a drive wheel 35, positive lines PL 1 and PL 2, a negative line NL, and a current sensor 52. And a cooling water temperature sensor 58 and a control device 40.

  The power storage device B is a rechargeable DC power source, and is constituted by a secondary battery such as nickel hydride or lithium ion, for example. Power storage device B stores power for traveling and supplies power to boost converter 10. Further, when the vehicle 100 is braked, the electric power generated by the motor generator 30 is received and charged. Note that as the power storage device B, a large-capacity capacitor may be used instead of the secondary battery.

  Boost converter 10 includes a reactor L, power semiconductor switching elements (hereinafter simply referred to as “switching elements”) Q1 and Q2, and diodes D1 and D2. Switching elements Q1, Q2 are connected in series between positive electrode line PL2 and negative electrode line NL. The collector of switching element Q1 is connected to positive electrode line PL2, and the emitter of switching element Q2 is connected to negative electrode line NL. Diodes D1 and D2 are connected in antiparallel to switching elements Q1 and Q2, respectively. Reactor L is connected between a connection node of switching elements Q1, Q2 and positive electrode line PL1. In other words, boost converter 10 is composed of a current reversible chopper circuit.

  As the switching elements in the switching elements Q1 and Q2 and the inverter 20, for example, an IGBT (Insulated Gate Bipolar Transistor), a power MOS (Metal Oxide Semiconductor) transistor, or the like can be used.

  Boost converter 10 boosts the voltage between positive electrode line PL2 and negative electrode line NL (hereinafter also referred to as “system voltage”) to be higher than the output voltage of power storage device B based on signal PWC from control device 40. When the system voltage is lower than the target voltage, by increasing the on-duty of switching element Q2, a current can flow from positive line PL1 to positive line PL2, and the system voltage can be increased. On the other hand, when the system voltage is higher than the target voltage, by increasing the on-duty of switching element Q1, a current can flow from positive line PL2 to positive line PL1, and the system voltage can be lowered. Furthermore, boost converter 10 can be disabled by setting switching element Q1 to an always-on state (switching element Q2 is always to an off state).

  Inverter 20 converts DC power supplied from positive electrode line PL2 and negative electrode line NL into three-phase AC based on signal PWI from control device 40, and outputs it to motor generator 30 to drive motor generator 30. As a result, motor generator 30 is driven so as to generate torque specified by the torque command value. Inverter 20 also converts the three-phase AC power generated by motor generator 30 into DC based on signal PWI and outputs it to positive line PL2 and negative line NL during braking of the vehicle. For example, the inverter 20 is configured by a bridge circuit including switching elements for three phases.

  Boost converter 10 and inverter 20 are cooled by a water cooling type cooling device (not shown). Boost converter 10 and inverter 20 may be cooled by a common cooling device, or each of boost converter 10 and inverter 20 may be cooled by an individual cooling device.

  Motor generator 30 is an AC motor, for example, a three-phase AC motor including a rotor in which permanent magnets are embedded. The motor generator 30 is mechanically coupled to the drive wheels 35 and generates a driving force for traveling. Further, the motor generator 30 receives the kinetic energy of the vehicle from the drive wheels 35 and generates electric power when the vehicle is braked. If the vehicle 100 is a hybrid vehicle, the motor generator 30 is mechanically connected to an engine (not shown), generates power using the engine power, and also starts the engine, and is incorporated in the hybrid vehicle. May be.

  Current sensor 52 detects current Ib input to and output from power storage device B and outputs the detected value to control device 40. Cooling water temperature sensor 58 detects a cooling water temperature Tw of a cooling device that cools boost converter 10 (hereinafter, also simply referred to as “cooling water temperature Tw of boost converter 10”), and outputs the detected value to control device 40. To do.

  Control device 40 generates signals PWC and PWI for driving boost converter 10 and motor generator 30, respectively, and outputs the generated signals PWC and PWI to boost converter 10 and inverter 20, respectively.

  In addition, the control device 40 determines that the detected value of the current Ib received from the current sensor 52 (actually, a smoothing process is performed on the detected value as will be described later) has a control threshold value (described later). When it exceeds, feedback control (hereinafter also referred to as “excess current FB control”) is executed with a value obtained by subtracting the control threshold value from the detected value of the current Ib as a control input.

  More specifically, control device 40 compares the magnitude of current threshold value Ith1 determined for protecting power storage device B with current threshold value Ith2 for protecting diode D1 in the upper arm of boost converter 10. To do. Here, current threshold value Ith2 for protecting diode D1 is determined based on the detected value of cooling water temperature Tw of boost converter 10 received from cooling water temperature sensor 58. Then, control device 40 executes the excess current FB control using the smaller one of current threshold values Ith1 and Ith2 as the control threshold value.

  FIG. 2 is a diagram showing a temperature change of diode D1 in the upper arm of boost converter 10. Referring to FIG. 2, the vertical axis represents the temperature increase ΔTd of diode D1 when current Id flows through diode D1 from time t0 when temperature Td of diode D1 converges to cooling water temperature Tw of boost converter 10. Show.

  As shown in FIG. 2, when the current Id flows through the diode D1, the temperature Td rises. The temperature increase amount ΔTd increases as the current Id increases. That is, the temperature rise amount ΔTd of the diode D1 is proportional to the current Id flowing through the diode D1. On the other hand, in order to protect the diode D1 from overheating destruction, it is necessary to suppress the temperature Td of the diode D1 to a temperature lower than the upper limit value Tmax as shown in the following equation.

Td = Tw + ΔTd <Tmax (1)
From the above equation, it is necessary to suppress the temperature rise amount ΔTd of the diode D1 as the cooling water temperature Tw of the boost converter 10 is higher. As described above, the temperature rise amount ΔTd of the diode D1 is proportional to the current Id flowing through the diode D1. Therefore, as shown in FIG. 3, the maximum value Idmax of the current Id flowing through the diode D1 needs to be set lower as the cooling water temperature Tw of the boost converter 10 is higher.

  Therefore, in the first embodiment, based on the detected value of cooling water temperature Tw received from cooling water temperature sensor 58, maximum value Idmax of current Id flowing through diode D1 is determined. A value obtained by subtracting an appropriate margin from the determined maximum value Idmax is defined as a current threshold value Ith2 indicating a threshold value of the current Ib for protecting the diode D1. That is, current threshold value Ith2 is set so as to decrease as the detected value of cooling water temperature Tw of boost converter 10 increases.

  FIG. 4 is a functional block diagram of a portion related to excess current FB control of the control device 40 shown in FIG. Referring to FIG. 4, control device 40 includes annealing processing unit 72, excess current FB control unit 74, subtraction unit 76, motor power calculation unit 78, motor torque calculation unit 80, and inverter control unit 82. Including.

  The annealing processing unit 72 receives the detected value of the current Ib from the current sensor 52 (FIG. 1), and executes an annealing process (gradual change process) on the received detected value. In this annealing process, for example, the detection value of the current sensor 52 is subjected to an averaging process or a delay process of the time constant T1. In the first embodiment, this annealing processing unit 72 may be omitted. Then, the annealing processing unit 72 gives the current Ib * subjected to the annealing process to the excess current FB control unit 74.

  Excess current FB control unit 74 receives current Ib * from annealing processing unit 72 and receives a detected value of cooling water temperature Tw of boost converter 10 from cooling water temperature sensor 58 (FIG. 1). Then, the excess current FB control unit 74 uses the detected value of the received coolant temperature Tw to control the current Ib when the current threshold exceeds the control threshold value determined by the method described later. Excess current FB control for controlling the current so as to be lower than the value is executed.

  Subtraction unit 76 subtracts the control amount output from excess current FB control unit 74 from discharge allowable power Wout indicating the allowable value of power (W) that can be discharged from power storage device B, and calculates the calculation result as discharge allowable power. The correction value Wout * of Wout is output to the motor power calculation unit 78.

  The motor power calculation unit 78 receives an accelerator opening signal ACC indicating the accelerator opening and a vehicle speed signal VS indicating the vehicle speed. Each of the accelerator opening and the vehicle speed is detected by a sensor (not shown). The motor power calculation unit 78 calculates the motor power Pm required for the motor generator 30 (FIG. 1) based on the accelerator opening, the vehicle speed, and the like. Here, when the motor power Pm exceeds the correction value Wout *, the motor power Pm is limited to the correction value Wout *.

  Motor torque calculation unit 80 calculates torque command value TR indicating the torque required for motor generator 30 based on motor power Pm received from motor power calculation unit 78. Then, inverter control unit 82 generates and generates a PWM (Pulse Width Modulation) signal for driving inverter 20 (FIG. 1) so that motor generator 30 outputs the torque indicated by torque command value TR. The PWM signal is output to inverter 20 as signal PWI.

  FIG. 5 is a flowchart for explaining a specific processing procedure related to the excess current FB control executed by the control device 40. Referring to FIG. 5, control device 40 acquires a detected value of current Ib from current sensor 52 (FIG. 1) (step S10). And the control apparatus 40 performs the smoothing process of time constant T1 with respect to the detected value of the acquired electric current Ib (step S20).

  Next, control device 40 acquires a detected value of cooling water temperature Tw of boost converter 10 from cooling water temperature sensor 58 (FIG. 1) (step S30). Subsequently, control device 40 determines a current threshold value Ith1 determined for protecting power storage device B (step S40). This current threshold value Ith1 is determined based on, for example, the rated current of a fuse provided in power storage device B.

  Furthermore, as described with reference to FIGS. 2 and 3, the control device 40 determines a current threshold value that is set to protect the diode D1, based on the detected value of the coolant temperature Tw acquired in step S30. Ith2 is determined (step S50). That is, the control device 40 determines the maximum value Idmax of the current Id flowing through the diode D1 based on the detected value of the cooling water temperature Tw, and sets a current threshold value obtained by subtracting an appropriate margin from the determined maximum value Idmax. The value is Ith2. As can be easily estimated from FIG. 3, the current threshold value Ith2 is determined so as to decrease as the detected value of the coolant temperature Tw increases.

  Then, control device 40 determines whether or not current threshold value Ith1 is smaller than current threshold value Ith2 (step S60). When it is determined that current threshold value Ith1 is smaller than current threshold value Ith2 (YES in step S60), control device 40 sets current threshold value Ith1 to the excess current threshold value used for excess current FB control. Set (step S70). On the other hand, when it is determined that current threshold value Ith2 is smaller than current threshold value Ith1 (NO in step S60), control device 40 sets current threshold value to the excess current threshold value used for excess current FB control. Ith2 is set (step S80).

  Next, control device 40 sets a control gain for excess current FB control (step S90). For example, the control device 40 sets the control gain to a predetermined G1. Then, control device 40 performs excess current FB control using the set excess current threshold and control gain (step S100). Specifically, when the current Ib * subjected to the annealing process in step S20 exceeds the excess current threshold, the control device 40 uses a value obtained by subtracting the excess current threshold from the current Ib * as a control input, and Then, FB control (for example, PI (proportional integral) control) is executed with a control gain of G1.

  As described above, in the first embodiment, when the detected value of the current sensor 52 exceeds the control threshold value, the excess current FB control for controlling the current based on the detected value is executed. Current threshold Ith1 determined to protect power storage device B and current threshold Ith2 determined based on the detected value of cooling water temperature sensor 58 to protect diode D1 of boost converter 10 Since the excess current FB control is executed using the smaller one as the control threshold value, current limiting is appropriately performed according to the situation. Therefore, according to the first embodiment, boost converter 10 and power storage device B can be appropriately protected without unnecessarily restricting running performance.

[Embodiment 2]
By increasing the control gain of the excess current FB control, the amount of overshoot of the current Ib with respect to the excess current threshold can be reduced. However, if the control gain is set to a large value, the current Ib hunts around the excess current threshold.

  Therefore, in the second embodiment, in order to reduce the overshoot amount of the current Ib with respect to the excess current threshold, the control gain of the excess current FB control is set to a larger value than in the first embodiment. In order to prevent current hunting due to an increase in the control gain, the time constant of the annealing process for the detected value of the current Ib is set to a larger value than that in the first embodiment.

  The overall configuration diagram of the vehicle in the second embodiment is the same as that of the vehicle 100 in the first embodiment shown in FIG.

  FIG. 6 is a flowchart for explaining a specific processing procedure related to excess current FB control executed by control device 40 in the second embodiment. Referring to FIG. 6, this flowchart includes steps S25 and S95 in place of steps S20 and S90 in the flowchart shown in FIG.

  That is, when the detected value of current Ib is acquired from current sensor 52 (FIG. 1) in step S10, control device 40 executes an annealing process for time constant T2 on the acquired detected value of current Ib. (Step S25). Here, the time constant T2 is larger than the time constant T1 of the annealing process in the first embodiment.

  When the excess current threshold value is set in step S70 or S80, control device 40 sets the control gain of excess current FB control to a predetermined G2 (step S95). Here, the control gain G2 is larger than the control gain G1 in the first embodiment. Then, the process proceeds to step S100, and excess current FB control is executed.

  FIG. 7 is a diagram showing the behavior of the current Ib. Referring to FIG. 7, curves k1 and k2 are shown as comparative examples, and curve k1 is obtained when the control gain is set to G1 and the time constant of the current smoothing process is set to T1. The behavior of the current Ib is shown. Curve k2 shows the behavior of current Ib when only the control gain is increased to G2. Curve k3 shows the behavior of current Ib when the control gain is increased to G2 and the time constant of the current smoothing process is also increased to T2, that is, the behavior of current Ib in the second embodiment. Indicates.

  As shown by the curve k2, by increasing the control gain, the overshoot amount of the current Ib with respect to the excess current threshold can be suppressed, but the current Ib hunts. Therefore, in the second embodiment, by increasing the control gain and increasing the time constant of the current smoothing process, the current Ib hunting can be suppressed while suppressing the overshoot of the current Ib as shown by the curve k3. Can be suppressed.

  As described above, according to the second embodiment, since the control gain of the excess current FB control is increased and the time constant of the current smoothing process is also increased, the overshoot amount of the current Ib can be reduced. In addition, hunting of the current Ib can be prevented.

  In each of the above-described second embodiments, the detection value of current sensor 52 for detecting current Ib of power storage device B is used for excess current FB control, but current Id flowing through boost converter 10 is detected. In the case where a current sensor is provided, the detection value of the sensor may be used. When a current sensor that detects a current flowing through diode D1 of boost converter 10 is used, it is not necessary to subtract an appropriate margin from maximum value Idmax when calculating current threshold value Ith2.

  Further, in each of the above embodiments, vehicle 100 may be an electric vehicle using motor generator 30 as the only driving power source, or a hybrid vehicle further equipped with an engine as the driving power source. Further, it may be a fuel cell vehicle in which a fuel cell is further mounted in addition to the power storage device B.

  In the above, inverter 20 corresponds to an embodiment of “driving device” in the present invention, and boost converter 10 corresponds to an embodiment of “boost device” in the present invention. Cooling water temperature sensor 58 corresponds to an example of “refrigerant temperature sensor” in the present invention, and diode D1 corresponds to an example of “power semiconductor element” in the present invention. Further, switching elements Q1, Q2 respectively correspond to one embodiment of “first and second power semiconductor switching elements” in the present invention, and motor generator 30 corresponds to one embodiment of “electric motor” in the present invention. Correspond.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  DESCRIPTION OF SYMBOLS 10 Boost converter, 20 Inverter, 30 Motor generator, 35 Drive wheel, 40 Control apparatus, 52 Current sensor, 58 Cooling water temperature sensor, 72 Smoothing process part, 74 Excess current FB control part, 76 Subtraction part, 78 Motor power calculation part , 80 Motor torque calculation unit, 82 inverter control unit, B power storage device, PL1, PL2 positive line, NL negative line, L reactor, Q1, Q2 switching element, D1, D2 diode.

Claims (8)

A power storage device;
A driving device for driving a load using electric power output from the power storage device;
A booster device provided between the power storage device and the drive device, and configured to be capable of boosting an input voltage of the drive device to a voltage higher than the voltage of the power storage device;
A current sensor for detecting a current supplied from the power storage device to the driving device;
A refrigerant temperature sensor for detecting the temperature of the refrigerant for cooling the booster;
A controller that performs excess current feedback control for controlling the current based on the detected value when a detected value of the current sensor exceeds a control threshold;
The step-up device includes a power semiconductor element that allows a current to flow from the power storage device to the drive device,
The control device is determined based on a first current threshold value determined to protect the power storage device and a detection value of the refrigerant temperature sensor to protect the power semiconductor element. A load driving device that executes the excess current feedback control by using a smaller one of current threshold values as the control threshold value.   2. The load driving device according to claim 1, wherein the second current threshold value is set to be smaller as a detected value of the refrigerant temperature sensor is larger. Further comprising an annealing processing unit for performing an annealing process on the detection value of the current sensor;
The control gain of the excess current feedback control is set to a value larger than the first reference value,
The load driving device according to claim 1, wherein the time constant of the annealing process is set to a value larger than a second reference value corresponding to the first reference value. The booster is
First and second power semiconductor switching elements connected in series between a pair of power lines connected to the driving device;
A reactor connected between a connection node between the first and second power semiconductor switching elements and a positive electrode of the power storage device;
The power semiconductor element is a diode,
4. The load driving device according to claim 1, wherein the diode is connected in antiparallel to the first power semiconductor switching element forming the upper arm. 5. The load driving device according to any one of claims 1 to 4,
An electric motor driven by the load driving device;
A vehicle comprising drive wheels driven by the electric motor. A method for controlling a load driving device, comprising:
The load driving device includes:
A booster device provided between a drive device that drives a load and a power storage device, and configured to be capable of boosting an input voltage of the drive device to be equal to or higher than a voltage of the power storage device;
The step-up device includes a power semiconductor element that allows a current to flow from the power storage device to the drive device,
The control method is:
Detecting a current supplied from the power storage device to the driving device;
Detecting a temperature of a refrigerant for cooling the booster;
Performing an excess current feedback control for controlling the current based on the detected value when the detected value of the current exceeds a control threshold value,
The step of executing the overcurrent feedback control includes:
Determining a first current threshold for protecting the power storage device;
Determining a second current threshold based on a detected value of the temperature of the refrigerant to protect the power semiconductor element;
And a sub-step of executing the excess current feedback control using a smaller one of the first and second current threshold values as the control threshold value.   The method for controlling a load driving device according to claim 6, wherein the second current threshold value is set to be smaller as the detected value of the temperature is larger. Further comprising performing an annealing process on the detected current value;
The control gain of the excess current feedback control is set to a value larger than the first reference value,
The load driving device control method according to claim 6 or 7, wherein a time constant of the annealing process is set to a value larger than a second reference value corresponding to the first reference value.

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