Control device of a DC-DC converter

Abstract

A control device (310, 315, 319) of a DC-DC converter (400, 405) for charging a high-voltage-side battery (10), comprising a primary-side circuit (40) electrically connected between an input side and a transformer (50) and a secondary-side circuit (60, 70) electrically connected between an output side and the transformer, comprising: a command generation unit (325, 327, 329) that sets an output current limit value of the secondary-side circuit to a predetermined value based on a detected input voltage of the primary-side circuit; a workload generation unit (330, 332, 334) that calculates a workload configured to turn ON / OFF a switching element constituting the primary-side circuit based on the output current limit value set by the command generation unit and a detected output current of the secondary-side circuit; and a switching signal generating unit (335) that generates a switching signal of the primary-side circuit based on the workload calculated by the workload generating unit, wherein the workload generating unit generates the workload such that the output current of the secondary-side circuit is limited to the output current limit value or below, wherein the command generation unit (325, 327, 329) sets an output voltage command of the secondary-side circuit to a value determined in advance based on the detected input voltage, the workload generation unit (330, 332, 334) sets the output current limit value set by the command generation unit, and compares the detected output current, if the output current limit value set by the command generation unit is equal to or less than the detected output current, the workload generation unit calculates a workload for regulating the output current so that an output current of the secondary-side circuit is adjusted to the output current limit value set by the command generation unit, is adjusted if the output current limit value set by the command generation unit is greater than the detected output current, the workload generation unit calculates a workload to regulate the output voltage, so that an output voltage of the secondary-side circuit is adjusted to the output voltage command set by the command generation unit, the switching signal generation unit generates the switching signal based on one of the workloads: workload for regulating the output current and workload for regulating the output voltage, which are calculated by the workload generation unit, wherein the command generation unit, if the detected input voltage is greater than a first predetermined voltage, sets the output voltage command so that the output voltage command increases with respect to an increase in the detected input voltage, and sets the output current limiting value so that the output current limiting value decreases with respect to the increase in the detected input voltage.

Description

Technical field

[0001] The present invention relates to a control device of a power converter, and more particularly to a control device of a DC-DC converter capable of suppressing the degradation of a high-voltage side battery used. State of the art

[0002] JP-A-62-173901 (PTL 1) serves as an example of the prior art in this field. PTL 1 describes that an output voltage of a DC-DC converter is linearly reduced according to a voltage decrease of a high-voltage-side battery to suppress overdischarge of the high-voltage-side battery, thus suppressing degradation of the high-voltage-side battery. List of referencesPatent literature PTL 1: JP S62-173 901 A PTL 2: US 2011 / 0 261 589 A1 PTL 3: US 2002 / 0 027 786 A1

[0003] PTL 2 describes a power converter arranged in a vehicle and comprising a switch that switches in dependence on a pulse width modulation rate of a signal supplied to the power converter.

[0004] PTL 3 describes a power supply for supplying a consumer with electrical current, which power supply comprises a switch which switches in dependence on a pulse width modulation rate of a signal supplied to the power supply. Summary of the inventionTechnical problem

[0005] However, PTL 1 concerns a technology that only regulates the output voltage of the DC / DC converter, and therefore, it is difficult to regulate the input / output current of the DC / DC converter to a predetermined value. In a control method of the DC / DC converter, the magnitude of the input / output current of the DC / DC converter changes depending on the magnitude of a current (hereinafter referred to as load current) required for an auxiliary system load connected to a low-voltage-side battery. That is, in PTL 1, when the load current increases, a current supplied to the load from the high-voltage-side battery via the DC / DC converter increases, and thus, overdischarge of the high-voltage-side battery cannot be suppressed in some cases.The invention has been made in consideration of the problem, and an object thereof is to provide a control device of a DC-DC converter capable of suppressing the degeneration of a high-voltage side battery regardless of the magnitude of a load current. Problem solving

[0006] In the invention, the above-mentioned problem is solved according to the subject matter of the appended claims. According to one aspect of the invention, a control device of a DC-DC converter consisting of a primary-side circuit electrically connected between an input side and a transformer and a secondary-side circuit electrically connected between an output side and the transformer includes a command generation unit that sets an output current limit value of the secondary-side circuit to a predetermined value based on a detected input voltage of the primary-side circuit;a workload generation unit that calculates a workload configured to turn on / off a switching element constituting the primary-side circuit based on the output current limit value set by the command generation unit and a detected output current of the secondary-side circuit; and a switching signal generation unit that generates a switching signal of the primary-side circuit based on the workload calculated by the workload generation unit, wherein the workload generation unit generates the workload such that the output current of the secondary-side circuit is limited to the output current limit value or below. Advantageous Effects of the Invention:

[0007] The invention has the configuration described above, and therefore it is possible to suppress the degeneration of a high-voltage side battery regardless of the size of a load current. Short description of the drawings [ Fig. 1] Fig. 1 is a view illustrating a hybrid vehicle system including a DC-DC converter 400 according to a first embodiment. [ Fig. 2] Fig. 2 is a view illustrating a control device 310 according to a first embodiment. [ Fig. 3] Fig. 3 is a view illustrating a command generation unit 325 according to the first embodiment. [ Fig. 4] Fig. 4 is a view illustrating a workload generation unit 330 according to the first embodiment. [ Fig. 5] Fig. 5 is a view illustrating a proportional-integral controller unit 600 according to the first embodiment. [ Fig. 6] Fig. 6 is a view illustrating a switching signal generating unit 335 according to the first embodiment. [ Fig. 7] Fig. 7 is a view illustrating a relationship between an input voltage V5 and an output voltage V10 and an output current I10 according to the first embodiment. [ Fig. 8] Fig. 8 is a view illustrating a relationship between the input voltage V5, the output voltage V10, and the output current I10 according to the first embodiment. [ Fig. 9] Fig. 9 is a view illustrating a hybrid vehicle system including a DC-DC converter 405 according to a second embodiment. [ Fig. 10] Fig. 10 is a view illustrating a control device 315 according to the second embodiment. [ Fig. 11] Fig. 11 is a view illustrating a command generation unit 327 according to the second embodiment. [ Fig. 12] Fig. 12 is a view illustrating a workload generation unit 332 according to the second embodiment. [ Fig. 13] Fig. 13 is a view illustrating a relationship between an input voltage V5 and an output voltage V10 and an input current I15 according to the second embodiment. [ Fig. 14] Fig. 14 is a view illustrating a relationship between the input voltage V5, the output voltage V10, and the input current I15 according to the second embodiment. [ Fig. 15] Fig. 15 is a view illustrating a control device 319 according to a third embodiment. [ Fig. 16] Fig. 16 is a view illustrating a workload generation unit 334 according to the third embodiment. [ Fig. 17] Fig. 17 is a view illustrating a voltage / current control unit 606 according to the third embodiment. Description of the embodiments

[0008] Embodiments of the invention will be described below with reference to the accompanying drawings. First Embodiment (Hybrid vehicle system including a DC-DC converter)

[0009] Fig. 1 is a view illustrating a hybrid vehicle system including a DC-DC converter 400 according to a first embodiment of the invention. A primary-side circuit of the DC-DC converter 400 and a DC side of an inverter 500 are connected to a high-voltage-side battery 10. A nickel-hydrogen storage battery, a lithium-ion battery, or the like can be used as the high-voltage-side battery 10. A secondary-side circuit of the DC-DC converter 400 is magnetically connected to the primary-side circuit via a transformer 50 and is connected in parallel to a low-voltage-side battery 100 and an auxiliary system load 110 (hereinafter referred to as load 110). A lead-acid storage battery or the like is used as the low-voltage-side battery 100.

[0010] A three-phase AC side of the inverter 500 is connected to a three-phase winding wound around a stator of a motor generator 510. The inverter 500 converts a DC voltage of the high-voltage-side battery 10 into a three-phase AC current of variable voltage and variable frequency in response to a torque command of the motor generator 510 received from a vehicle control device (not shown). The inverter 500 applies a converted three-phase AC voltage to the three-phase winding of the motor generator 510 to regulate a three-phase AC current flowing through the three-phase winding of the motor generator 510.

[0011] The motor generator 510 generates a rotating magnetic field using the three-phase alternating current flowing through the three-phase winding wound around the stator, and generates the torque of the motor generator 510 by accelerating or decelerating the rotational motion of a rotator through the generated rotating magnetic field. The torque generated by the motor generator 510 is transmitted to a gearbox 365 via a motor generator shaft 360. Preferably, the vehicle-mounted motor generator 510 uses a powerful, small-sized, high-efficiency permanent magnet electric motor, but an induction motor or the like may be readily used.

[0012] A motor 375 controls the intake, compression, ignition, and exhaust of a fuel in response to a motor 375 torque command received from a vehicle control device (not shown), thereby generating the torque of the motor 375. The generated torque of the motor 375 is transmitted to a transmission 365 via a motor-generator shaft 370.

[0013] The transmission 365 transmits all of the torque of the motor generator 510 and the torque of the engine 375 transmitted via a propeller shaft 380 to a differential gear 520. The differential gear 520 converts the torque transmitted from the transmission 365 into drive shaft torque and transmits the torque to a drive shaft 530. The drive shaft 530 accelerates or decelerates the rotational movement of the drive wheels 540 of a vehicle via the transmitted drive shaft torque, thereby accelerating or decelerating the vehicle (not shown).

[0014] In addition, the motor generator 510 converts the torque of the motor 375, which is transmitted to the motor generator shaft 360 via the gear box 365, into electric power, and the converted electric power can be charged into the high-voltage-side battery 10 via the inverter 500. In addition, the motor generator 510 converts rotational energy of the drive wheel 540, which is sequentially transmitted to the motor generator shaft 360 via the drive shaft 530, the differential gear 520, the propeller shaft 380, and the gear box 365, into electric power, and the converted electric power can also be charged into the high-voltage-side battery 10 via the inverter 500.

[0015] Here, an operation of supplying electric power from the high-voltage-side battery 10 to the motor generator 510 via the inverter 500 is defined as a power running operation, and an operation of charging the electric power generated in the motor generator 510 into the high-voltage-side battery 10 is defined as a regeneration operation. In the power running operation, electric power is supplied from the high-voltage-side battery 10 to the motor generator 510 (electric power is taken out from the high-voltage-side battery 10), and thus the voltage in the high-voltage-side battery 10 is reduced.

[0016] On the other hand, during the regeneration operation, the electric power generated in the motor generator 510 is charged into the high-voltage-side battery 10, and thus the voltage of the high-voltage-side battery 10 is increased. To suppress the degradation of the high-voltage-side battery 10, it is necessary to prevent over-discharge or overcharge of the high-voltage-side battery 10 by controlling the power driving operation and the regeneration operation in a well-balanced manner. However, in a hybrid vehicle, to achieve low fuel consumption, it is preferable to maximize the use of power driving operation during vehicle start-up and acceleration, and to maximize the use of regenerative braking during vehicle deceleration, and therefore, there is a possibility that the high-voltage-side battery 10 may be brought into an over-discharged or over-charged state.Accordingly, the invention provides the DC-DC converter 400 which can suppress over-discharging and overcharging of the high-voltage side battery 10.

[0017] The DC-DC converter 400 according to this embodiment includes a filter capacitor 20, a voltage sensor 192, MOSFETs 210, 220, 230, and 240, and a resonant reactor 30 in a primary-side circuit. In the filter capacitor 20, one end of the filter capacitor 20 is connected to a high-potential side of the high-voltage battery 10, and the other end of the filter capacitor 20 is connected to a low-potential side of the high-voltage battery 10. In the voltage sensor 192, one end of the voltage sensor 192 is connected to a high-potential side of the high-voltage battery 10, and the other end of the voltage sensor 192 is connected to a low-potential side of the high-voltage battery 10.

[0018] The high-potential side of the high-voltage battery 10 is connected to a drain of the MOSFET 210 and a drain of the MOSFET 230. The low-potential side of the high-voltage battery 10 is connected to a source of the MOSFET 220 and a source of the MOSFET 240. A source of the MOSFET 210 is connected to a drain of the MOSFET 220 and one end of the resonant choke 30. The other end of the resonant choke 30 is connected to one end of a primary-side winding 40 of the transformer 50. The other end of the primary-side winding 40 of the transformer 50 is connected to a source of the MOSFET 230 and a drain of the MOSFET 240. Here, the resonant choke 30 can be replaced by junction inductance or leakage inductance of the transformer 50.

[0019] The DC-DC converter 400 includes a smoothing capacitor 90, a smoothing choke 80, a snubber capacitor 25, a voltage sensor 190, a current sensor 200, and MOSFETs 250, 260, 270, and 280 in a secondary side circuit.

[0020] One end of a secondary-side winding 60 of transformer 50 is connected to a source of MOSFET 260 and a drain of MOSFET 280. The other end of the secondary-side winding 60 of transformer 50 is connected to one end of a secondary-side winding 70 of transformer 50 and one end of smoothing reactor 80. The other end of the secondary-side winding 70 of transformer 50 is connected to a source of MOSFET 250 and a drain of MOSFET 270.

[0021] A drain of MOSFET 250 and a drain of MOSFET 260 are connected to one end of snubber capacitor 25. The other end of snubber capacitor 25 is connected to a source of MOSFET 270, a source of MOSFET 280, and one end of current sensor 200.

[0022] The other end of the smoothing reactor 80 is connected to one end of the smoothing capacitor 90 and one end of the voltage sensor 190. The other end of the smoothing capacitor 90 and the other end of the voltage sensor 190 are connected to the other end of the current sensor 200.

[0023] A high-potential side of the low-voltage battery 100 is connected to one end of the smoothing capacitor 90, one end of the voltage sensor 190, and the other end of the smoothing reactor 80. A low-potential side of the low-voltage battery 100 is connected to the other end of the smoothing capacitor 90, the other end of the voltage sensor 190, the other end of the current sensor 200, and a ground of a vehicle. Furthermore, one end of the load 110 is connected to the high-potential side of the low-voltage battery 100, and the other end of the load 110 is connected to a low-potential side of the low-voltage battery 100.

[0024] The DC-DC converter 400 includes the voltage sensor 192 connected in parallel with the high-voltage-side battery 10, the voltage sensor 190 connected in parallel with the low-voltage-side battery 100, and the current sensor 200 connected in series with the low-voltage-side battery 100. The voltage sensor 192 detects an input voltage V5 of the DC-DC converter 400. The voltage sensor 190 detects an output voltage V10 of the DC-DC converter 400. The current sensor 200 detects an output current I10 of the DC-DC converter 400.

[0025] Voltage sensors consist of non-inverting amplifiers that use a voltage divider resistor and an operational amplifier, a differential amplifier, and the like. Current sensors consist of a shunt resistor, a Hall element, and the like.

[0026] A control device 310 of the DC-DC converter 400 generates a gate voltage V30 configured to control ON / OFF of MOSFET 210, which is a switching element of the DC-DC converter 400, based on the input voltage V5, the output voltage V10, and the output current I10, and inputs the generated gate voltage V30 to a gate of the MOSFET 210. As described below, the controller 310 of the DC-DC converter 400 inputs a gate voltage V40 to a gate of the MOSFET 220, inputs a gate voltage V50 to a gate of the MOSFET 230, inputs a gate voltage V60 to a gate of the MOSFET 240, inputs a gate voltage V70 to a gate of the MOSFET 250, inputs a gate voltage V80 to a gate of the MOSFET 260, inputs a gate voltage V90 to a gate of the MOSFET 270, and inputs a gate voltage V100 to a gate of the MOSFET 280. (DC-DC converter control device 310)

[0027] Fig. 2 is a view illustrating a control device 310 of the DC-DC converter 400 according to the first embodiment of the invention. The control device 310 of the DC-DC converter 400 includes an A / D converter 320 that converts an analog value into a digital value, a command generation unit 325, a workload generation unit 330, a switching signal generation unit 335, and a gate drive circuit 340.

[0028] The A / D converter 320 converts an analog value of the input voltage V5 of the DC-DC converter 400, which is detected by the voltage sensor 192, into a digital value VD5. Furthermore, the A / D converter 320 converts an analog value of the output voltage V10 of the DC-DC converter 400, which is detected by the voltage sensor 190, into a digital value VD10. Furthermore, the A / D converter 320 converts an analog value of the output current I10 of the DC-DC converter 400, which is detected by the current sensor 200, into a digital value ID10.

[0029] The command generation unit 325 generates an output voltage command VD10ref and an output current limit value ID10Lim of the DC-DC converter 400 based on the digital value VD5 (hereinafter referred to as input voltage VD5 of the DC-DC converter 400) representing the input voltage V5 of the DC-DC converter 400 detected by the voltage sensor 192 and the digital value VD10 (hereinafter referred to as output voltage VD10 of the DC-DC converter 400) representing the output voltage V10 of the DC-DC converter 400 detected by the voltage sensor 190.

[0030] The duty generation unit 330 generates a duty “Duty” of each of the MOSFETs 210, 220, 230, and 240 based on the output voltage command VD10ref and the output current limit value ID10Lim of the DC-DC converter 400 generated by the command generation unit 325, the output voltage VD10 of the DC-DC converter 400 output from the A / D converter 320, and the digital value ID10 (hereinafter referred to as output current ID10 of the DC-DC converter 400) representing the output current I10.

[0031] The switching signal generation unit 335 generates the ON / OFF signals S30, S40, S50, S60, S70, S80, S90 and S100 of the MOSFETs 210, 220, 230, 240, 250, 260, 270 and 280 of the DC-DC converter 400 based on the duty of the MOSFETs 210, 220, 230 and 240 of the DC-DC converter 400 generated by the duty generation unit 330.

[0032] The gate driver circuit 340 generates the gate voltages V30, V40, V50, V60, V70, V80, V90, and V100 configured to turn on and off the MOSFETs 210, 220, 230, 240, 250, 260, 270, and 280 of the DC-DC converter 400 based on the ON / OFF signals S30, S40, S50, S60, S70, S80, S90, and S100 of the MOSFETs 210, 220, 230, 240, 250, 260, 270, and 280 of the DC-DC converter 400 generated by the switching signal generating unit 335. (Command generation unit 325))

[0033] Fig. 3 is a view illustrating the command generation unit 325 provided to the control device 310 of the DC-DC converter 400 according to the first embodiment of the invention. However, with respect to the input voltage VD5 of the DC-DC converter 400, the command generation unit 325 determines four ranges similar to Expression (1) in advance. First area>second area>third area>fourth area≥0 (zero) ⋯

[0034] This means, with respect to the input voltage VD5, that a voltage value of 0 or greater is divided into four ranges and set as a first range, a second range, a third range, and a fourth range in this order from the high value.

[0035] First, in step a1, which is Fig. 3, the command generation unit 325 acquires the input voltage VD5 of the DC-DC converter 400 output from the A / D converter 320 (hereinafter simply referred to as input voltage VD5) and detects the output voltage VD10 of the DC-DC converter 400 (hereinafter simply referred to as output voltage VD10) in step a2. Then, the command generation unit 325 determines whether the input voltage VD5 acquired in step a1 belongs to the first range or not in step a3. (If the input voltage belongs to the first range)

[0036] If it is determined in step a3 that the input voltage VD5 belongs to the first range, the command generation unit 325 determines in step a4 whether or not the input voltage VD5 is equal to or greater than the upper limit VD5HLim determined in advance with respect to the input voltage VD5.

[0037] If it is determined in step a4 that the input voltage VD5 is equal to or greater than the upper limit VD5HLim, the command generation unit 325 sets the output voltage command VD10ref of the DC-DC converter 400 to the upper limit VD10HLim determined in advance with respect to the output voltage VD10 in step a5. Furthermore, the command generation unit 325 sets the output current limit value ID10Lim to 0 (zero) in step a6.

[0038] In addition, the command generation unit 325 inputs the output voltage command VD10ref set in step a5 and the output current limit value ID10Lim set in step a6 to the workload command generation unit 330.

[0039] When the output current limit value ID10Lim of the DC-DC converter 400 is set as described above, it is possible to turn off all MOSFETs 210 to 240 of the primary-side circuit of the DC-DC converter 400 before the total voltage V5 consisting of the input voltage V5 and a surge voltage occurring due to the switching of the MOSFETs 210 to 240 exceeds a test voltage of the MOSFETs 210 to 240. Furthermore, it is possible to turn off all MOSFETs 250 to 280 before the total voltage consisting of a voltage supplied to the secondary-side circuit via the transformer 50 and a surge voltage occurring due to the switching of the MOSFETs 250 to 280 exceeds a test voltage of the MOSFETs 250 to 280. Therefore, it is possible to prevent an overvoltage fault of the MOSFETs 210 to 280.

[0040] On the other hand, if it is determined in step a4 that the input voltage VD5 is less than the upper limit VD5HLim, the command generation unit 325 sets the output voltage command VD10ref of the DC-DC converter 400 to a predetermined output voltage value corresponding to the input voltage VD5 detected in step a1 in step a7. Furthermore, the command generation unit 325 sets the output current limit value ID10Lim to a predetermined output current corresponding to the input voltage VD5 detected in step a1 in step a8.

[0041] Furthermore, the command generation unit 325 inputs the output voltage command VD10ref set in step a7 and the output current limit value ID10Lim set in step a8 to the workload command generation unit 330. However, the predetermined output voltage value set as the output voltage command VD10ref of the DC-DC converter 400 is linearly increased with respect to the increase of the input voltage VD5 and linearly decreased with respect to the decrease of the input voltage VD5. In addition, the predetermined output voltage value is set in advance so that an input voltage VD5 being detected becomes a value that does not change rapidly during the transition from a value smaller than the upper limit value VD5HLim to a value equal to or greater than the upper limit value VD5HLim, or during the transition from the first range to the second range shown in Expression (1).

[0042] When the output voltage command VD10ref of the DC-DC converter 400 is set as described above, even in a case where the input voltage V5 of the DC-DC converter 400 changes, it is possible to suppress a rapid change in the output voltage V10 of the DC-DC converter 400.

[0043] Furthermore, the predetermined output current value set as the output current limit value ID10Lim of the DC-DC converter 400 is linearly decreased with respect to the increase in the detected input voltage VD5 of the DC-DC converter 400 and linearly increased with respect to the decrease in the detected input voltage VD5 of the DC-DC converter 400. Furthermore, the predetermined output current value is linearly changed from 0 (zero) to the upper limit ID10HLim, which is previously determined with respect to the output current ID10 of the DC-DC converter 400 (hereinafter simply referred to as the output voltage ID10), in accordance with a change in the detected input voltage VD5 of the DC-DC converter 400.

[0044] By setting the output current limit value ID10Lim of the DC-DC converter 400 as described above, even in a case where the input voltage V5 changes, it is possible to suppress a rapid change in the output current I10. Accordingly, underload operation of the output current limit I10 can be stabilized, thus improving the reliability of the DC-DC converter 400. (If the input voltage belongs to the second range)

[0045] On the other hand, if it is determined in step a3 that the input voltage VD5 does not belong to the first range, the command generation unit 325 determines in step a9 whether the input voltage VD5 belongs to the second range or not.

[0046] If it is determined in step a9 that the input voltage VD5 belongs to the second range, that is, if the high-voltage-side battery 10 is likely to reach an overcharged state, the command generation unit 325 sets the output voltage command VD10ref of the DC-DC converter 400 to a predetermined output voltage value corresponding to the input voltage VD5 in step a10. Furthermore, the command generation unit 325 sets the output current limit value ID10Lim to the upper limit ID10HLim in step a11.

[0047] Furthermore, the command generation unit 325 inputs the output voltage command VD10ref set in step a10 and the output current limit value ID10Lim set in step a11 to the workload command generation unit 330. However, the output voltage value set as the output voltage command VD10ref of the DC-DC converter 400 is linearly increased with respect to the increase of the input voltage VD5 and linearly decreased with respect to the decrease of the input voltage VD5. In addition, the predetermined output voltage value is set in advance so that an input voltage VD5 that is detected becomes a value that does not change rapidly during the transition from the second range to the first range or during the transition from the second range to the third range shown in Expression (1).

[0048] When the output voltage command VD10ref of the DC-DC converter 400 is set as described above, even in a case where the input voltage V5 of the DC-DC converter 400 changes, it is possible to suppress a rapid change in the output voltage V10 of the DC-DC converter 400. Furthermore, the output current limit value ID10Lim is set to the upper limit ID10HLim, and thus it is possible to increase the output current I10 of the DC-DC converter 400 in combination with the increase in the input voltage V5 of the DC-DC converter 400. That is, it is possible to increase the electric power drawn from the high-voltage-side battery 10 in combination with the increase in the input voltage V5 of the DC-DC converter 400, and thus it is possible to suppress the increase in the voltage of the high-voltage-side battery 10.Accordingly, it is possible to suppress overcharging of the high-voltage side battery 10. (If the input voltage belongs to the third range)

[0049] On the other hand, if it is determined in step a9 that the input voltage VD5 does not belong to the second range, the command generation unit 325 determines in step a12 whether the input voltage VD5 belongs to the third range or not.

[0050] If it is determined in step a12 that the input voltage VD5 belongs to the third range, that is, if the high-voltage-side battery 10 is less likely to reach an over-discharged or over-charged state, the command generation unit 325 sets the output voltage command VD10ref of the DC-DC converter 400 to a reference voltage value VD10st determined in advance with respect to the output voltage VD10 in step a13. Furthermore, the command generation unit 325 sets the output current limit value ID10Lim to the upper limit ID10HLim in step a11.

[0051] Furthermore, in step a13, the command generation unit 325 inputs the output voltage command VD10ref set in step a13 and the output current limit value ID10Lim set in step a11 to the workload command generation unit 330. However, it is preferable that the reference voltage VD10st set as the output voltage command VD10ref of the DC-DC converter 400 be set to a constant value such as 12V or the like.

[0052] When the output voltage command VD10ref and the output current limit value ID10Lim of the DC-DC converter 400 are set as described above, even in a case where the input voltage VD5 transitions from the third range to the second range or transitions from the third range to the fourth range shown in Expression (1), it is possible to suppress a rapid change in the output voltage V10. Furthermore, it is possible to prevent the high-voltage-side battery 10 and the low-voltage-side battery 100 from being over-discharged or over-charged. (If the input voltage belongs to the fourth range)

[0053] On the other hand, if it is determined in step a12 that the input voltage VD5 does not belong to the third range, the command generation unit 325 determines in step a14 that the input voltage VD5 belongs to the fourth range. That is, the command generation unit 325 determines that the high-voltage-side battery 10 is very likely to reach an over-discharge state.

[0054] Then, in step a15, the command generation unit 325 determines whether or not the output voltage VD10 is equal to or less than the lower limit VD10LLim determined in advance with respect to the output voltage VD10.

[0055] If it is determined in step a15 that the output voltage VD10 is equal to or less than the lower limit VD10LLim, the command generation unit 325 sets the output voltage command VD10ref of the DC-DC converter 400 to the lower limit VD10LLim in step a16. Furthermore, the command generation unit 325 sets the output current limit value ID10Lim to the upper limit ID10HLim in step a11.

[0056] In addition, the command generation unit 325 inputs the output voltage command VD10ref set in step a16 and the output current limit value ID10Lim set in step a11 to the workload command generation unit 330.

[0057] When the output voltage command VD10ref and the output current limit value ID10Lim of the DC-DC converter 400 are set as described above, it is possible to prevent overdischarge of the low-voltage-side battery 100. In a state of the input voltage V5 and the output voltage V10, the DC-DC converter 400 is preferably controlled as described above to give priority to preventing overdischarge of the low-voltage-side battery 100, thereby avoiding overdischarge of the high-voltage-side battery 10 through the regeneration operation.

[0058] On the other hand, if it is determined in step a15 that the output voltage VD10 is greater than the lower limit VD10LLim, the command generation unit 325 sets the output voltage command VD10ref of the DC-DC converter 400 to a predetermined output voltage value corresponding to the input voltage VD5 in step a17. Furthermore, the command generation unit 325 sets the output current limit value ID10Lim to a predetermined output current value corresponding to the input voltage VD5 in step a18.

[0059] Furthermore, the command generation unit 325 inputs the output voltage command VD10ref set in step a17 and the output current limit value ID10Lim set in step a18 to the workload command generation unit 330. However, the predetermined output voltage value set as the output voltage command VD10ref of the DC-DC converter 400 is linearly increased with respect to the increase of the input voltage VD5 and linearly decreased with respect to the decrease of the input voltage VD5. Furthermore, the predetermined output voltage value is set in advance so that an input voltage VD5 that is detected becomes a value that does not change rapidly during the transition from the fourth range to the third range.

[0060] When the output voltage command VD10ref of the DC-DC converter 400 is set as described above, even in a case where the input voltage V5 changes rapidly, it is possible to suppress a rapid change in the output voltage V10.

[0061] In addition, the predetermined output current value set as the output current limit value ID10Lim of the DC-DC converter 400 is linearly increased with respect to the increase in the detected input voltage VD5 and linearly decreased with respect to the decrease in the input voltage VD5. Furthermore, the predetermined output current value is linearly changed from 0 (zero) to the upper limit ID10HLim in accordance with a change in the input voltage VD5.

[0062] When the output current limit value ID10Lim of the DC-DC converter 400 is set as described above, it is possible to suppress a rapid change in the output current I10 even when the input voltage V5 changes. Furthermore, it is possible to limit the output current I10 regardless of a change in the load current, and thus it is possible to reduce the output current I10 in combination with the decrease in the input voltage V5. That is, it is possible to reduce the electric power drawn from the high-voltage-side battery 10 in combination with the decrease in the input voltage V5 regardless of the magnitude of the load current, and thus it is possible to suppress over-discharge of the high-voltage-side battery 10. (Workload generation unit 330)

[0063] Fig. 4 is a view illustrating the workload generation unit 330 provided to the control device 310 of the DC-DC converter 400 according to the first embodiment of the invention. As shown in Fig. 2, the workload generation unit 330 acquires the output voltage command VD10ref and the output current limit value ID10Lim of the DC-DC converter 400 output from the command generation unit 325, and the output voltage VD10 and the output current ID10 of the DC-DC converter 400 output from the A / D converter 320. A description follows with reference to Fig. 4. The workload generation unit 330 acquires the output voltage command VD10ref in step b1, acquires the output current limit value ID10Lim in step b2, acquires the output voltage VD10 in step b3, and acquires the output current ID10 in step b4.

[0064] Then, in step b5, the workload generation unit 330 determines whether the output current limit value ID10Lim of the DC-DC converter 400 detected in step b2 is 0 (zero).

[0065] If it is determined in step b5 that the output current limit value ID10Lim of the DC-DC converter 400 being detected is 0 (zero), the duty generation unit 330 sets a duty "Duty" to 0 (zero) in step b6. Furthermore, the duty generation unit 330 inputs the set duty "Duty" to the switching signal generation unit 335.

[0066] If the duty is calculated as described above, it is possible to turn off all MOSFETs 210 to 290, which are switching elements of the DC-DC converter 400.

[0067] On the other hand, if it is determined in step b5 that the output current limit value ID10Lim of the DC-DC converter 400 being detected is not 0 (zero), the workload generation unit 330 determines in step b7 whether the output current limit value ID10Lim of the DC-DC converter 400 being detected is larger than the output current ID10 being detected.

[0068] If it is determined in step b7 that the output current limit value ID10Lim of the detected DC-DC converter 400 is greater than the output current ID10, the workload generation unit 330 calculates a deviation Dev in step b8 by subtracting the output voltage VD10 from the output voltage command VD10ref of the detected DC-DC converter 400. Furthermore, in step 9, the workload generation unit 330 sets a proportional gain Kpv for controlling the output voltage to a proportional gain Kp, which is input to the subsequent proportional-integral control unit 600. Furthermore, in step b10, the workload generation unit 330 sets an integral gain Kiv for controlling the output voltage to an integral gain Ki.

[0069] Furthermore, in step b11, the duty generation unit 330 inputs the calculated deviation Dev and the adjusted proportional gain Kp and integral gain Ki to the proportional-integral controller unit 600, and calculates a duty "Duty" configured to set the deviation Dev to 0 (zero) based on the proportional-integral controller unit 600. Furthermore, the duty generation unit 330 inputs the calculated duty "Duty" to the switching signal generation unit 335.

[0070] If the duty is calculated as described above, it is possible to adjust the output voltage VD10 of the DC-DC converter 400 to the output voltage command VD10ref.

[0071] On the other hand, if it is determined in step b7 that the output current limit value ID10Lim of the detected DC-DC converter 400 is equal to or less than the output current ID10, the workload generation unit 330 calculates the deviation Dev in step b12 by subtracting the output voltage ID10 from the output current limit value ID10Lim of the detected DC-DC converter 400. Furthermore, in step b13, the workload generation unit 330 sets a proportional gain Kpco for controlling the output current to the proportional gain Kp, which is input to the proportional-integral control unit 600. Furthermore, in step b14, the workload generation unit 330 sets an integral gain Kico for controlling the output current to the integral gain Ki.

[0072] Furthermore, in step b11, the duty generation unit 330 inputs the calculated deviation Dev and the adjusted proportional gain Kp and integral gain Ki to the proportional-integral controller unit 600, and calculates a duty "Duty" configured to set the deviation Dev to 0 (zero) based on the proportional-integral controller unit 600. Furthermore, the duty generation unit 330 inputs the calculated duty "Duty" to the switching signal generation unit 335.

[0073] If the duty cycle is calculated as described above, it is possible to adjust the output current ID10 of the DC-DC converter 400 to the output current limit value ID10Lim. (Proportional-Integral Controller Unit 600)

[0074] Fig. 5 is a view illustrating the proportional-integral controller unit 600 provided to the workload generation unit 330 of the control device 310 of the DC-DC converter 400 according to the first embodiment of the invention. The proportional-integral controller unit 600 includes a multiplier 610, a multiplier 615, an integrator 620, and an adder 630.

[0075] First, the proportional-integral controller unit 600 detects the deviation Dev, the proportional gain Kp, and the integral gain Ki. Furthermore, the proportional-integral controller unit 600 inputs the detected deviation Dev and the proportional gain Kp to the multiplier 610. Furthermore, the proportional-integral controller unit 600 inputs the detected deviation Dev and the integral gain Ki to the multiplier 615.

[0076] The multiplier 610 multiplies the input deviation Dev by the proportional gain Kp. Furthermore, the multiplier 610 inputs a multiplication value to the adder 630. The multiplier 615 multiplies the input deviation Dev and the integral gain Ki. Furthermore, the multiplier 615 inputs a multiplication value to the integrator 620. The integrator 620 integrates the multiplied value input from the multiplier 615 and inputs an integration value to the adder 630. The adder 630 adds the multiplied value input from the multiplier 610 and the integrated value input from the integrator 620 to calculate the duty "Duty." The calculated duty "Duty" is input to the switching signal generation unit 335.

[0077] When the duty load "Duty" is generated as described above, in a case where the output current limit value ID10Lim of the DC-DC converter 400 is greater than the output current ID10, it is possible to adjust the output voltage VD10 to the output voltage command VD10ref. Furthermore, in a case where the output current limit value ID10Lim of the DC-DC converter 400 is equal to or less than the output current ID10, it is possible to adjust the output voltage ID10 to the output current limit value ID10Lim.

[0078] Next, an advantage of the invention compared to a typical method for controlling both the output voltage and the output current of the DC-DC converter will be described. First, a typical method for controlling both the output voltage and the output current of the DC-DC converter will be described. Examples of the typical method for controlling both the output voltage and the output current include a method in which a proportional-integral control unit for controlling the output voltage and a proportional-integral control unit for controlling the output current are independently prepared, and the proportional-integral control unit for controlling the output current is incorporated into an inner loop of the proportional-integral control unit of the output voltage regulator.

[0079] However, in the typical scheme, the output voltage regulator and the output current regulator interfere with each other. Therefore, it is necessary to set the response of the output voltage regulator slower than that of the output current regulator to stabilize the output voltage regulator incorporated in the inner loop. This means that in the scheme described above, the response of the output voltage regulator is slower, and therefore the output voltage changes rapidly when disturbances such as a rapid change in the load current occur.

[0080] On the other hand, in the invention described above, the output voltage regulator and the output current regulator do not interfere with each other because the proportional-integral regulator unit common to the output voltage regulator and the output current regulator is prepared, and because the deviation, proportional gain, and integral gain for controlling the output voltage and controlling the output current are converted according to a comparison result between the output current limiting value and the output current of the DC-DC converter 400. That is, in the invention, the responsiveness of the output voltage regulator can be set to high speed, and therefore, even in a case where disturbances such as a rapid change in the load current occur, it is possible to achieve a stable output voltage without rapid change in the output voltage. (Switching signal generating unit 335)

[0081] Next, the switching signal generation unit 335 provided to the control device 310 of the DC-DC converter 400 according to the first embodiment of the invention will be described. As shown in Fig. As described in Figure 2, the switching signal generation unit 335 generates ON / OFF signals S30 to S100 of the MOSFETs 210 to 280 of the DC-DC converter 400 based on the duty "Duty" input from the duty generation unit 330. Examples of a method for generating the ON / OFF signals S30 to S60 include a phase shift PWM.

[0082] Fig. 6 is a view illustrating the switching signal generation unit 335 provided to the control device 310 of the DC-DC converter 400 according to the first embodiment of the invention, to which the phase shift PWM is applied. The switching signal generation unit 335 sets a ratio between the ON time and the OFF time of the ON / OFF signals S30 to S60 to 50% and changes a phase difference of the ON / OFF signals S30 to S60. In addition, the switching signal generation unit 335 adjusts a period in which the ON of the ON / OFF signal S30 of the MOSFET 210 and the ON of the ON / OFF signal S60 of the MOSFET 240 overlap, and a period in which the ON of the ON / OFF signal S40 of the MOSFET 220 and the ON of the ON-OFF signal S50 of the MOSFET 230 overlap, to be equal to the workload “Duty” generated by the workload generation unit 330.Accordingly, the DC-DC converter 400 can adjust the output voltage or output current to any command value.

[0083] Here, as an example, a method for generating the ON / OFF signal S30 to S100 of the MOSFETs 210 to 280 of the DC-DC converter 400 in a state where the ON / OFF signal S30 of the MOSFET 210 of the primary side circuit of the DC-DC converter 400 is set as a reference will be described.

[0084] First, the switching signal generation unit 335 generates the ON / OFF signal S30 of the MOSFET 210 of the primary-side switching circuit of the DC-DC converter 400. The ON / OFF signal S30 is generated as a pulse signal in which the ratio of ON time to OFF time is set to 50%. For example, if a switching frequency is set to Fsw [Hz], the ON time and OFF time of the ON / OFF signal S30 can be represented by Expression (2). That is, the ON time and OFF time of the ON / OFF signal S30 become 50% of a switching period. (Expression 2) Time ON of S30 = Time OFF of S30 = 0.5 / Fsw⋯

[0085] Then, the switching signal generation unit 335 generates the ON / OFF signal S40 of the MOSFET 220. The ON / OFF signal S40 is generated such that the ON / OFF signal S40 is OFF in a period in which the ON / OFF signal S30 is ON and is ON in a period in which the ON / OFF signal S30 is OFF.

[0086] Then, the switching signal generation unit 335 generates the ON / OFF signal S50 of the MOSFET 230. The ON / OFF signal S50 is generated such that the ON / OFF signal S50 is turned ON with a delay by a work load “Duty” generated by the work load generation unit 330 after the ON / OFF signal S30 is turned ON, and is turned OFF after a lapse of time corresponding to 50% of one switching period.

[0087] Then, the switching signal generation unit 335 generates the ON / OFF signal S60 of the MOSFET 240. The ON / OFF signal S60 is generated such that the ON / OFF signal S60 is turned ON with a delay by the workload “Duty” generated by the workload generation unit 330 after the ON / OFF signal S40 is turned ON, and is turned OFF after a lapse of time corresponding to 50% of one switching period.

[0088] When the ON / OFF signals S30 to S50 are generated as described, it is possible to adjust a period in which ON of the ON / OFF signal S30 and ON of the ON / OFF signal S60 overlap, and a period in which ON of the ON / OFF signal S40 and ON of the ON / OFF signal S50 overlap to be equal to the workload “Duty” generated by the workload generation unit 330.

[0089] Next, the switching signal generation unit 335 generates the ON / OFF signal S70 of the MOSFET 250 of the secondary-side switching circuit of the DC-DC converter 400. The ON / OFF signal S70 is turned ON with a delay of a predetermined standby time α1 after the ON / OFF signal S30 is turned OFF. Furthermore, the ON / OFF signal S70 is generated so that the ON / OFF signal S70 is turned OFF after a lapse of time achieved by adding the duty "Duty" generated by the duty generation unit 330 and a predetermined duration β after the ON / OFF signal S30 is turned OFF.

[0090] Then, the switching signal generation unit 335 generates the ON / OFF signal S80 of the MOSFET 260. The ON / OFF signal S80 is turned ON with a delay of a predetermined standby time α1 after the ON / OFF signal S40 is turned OFF. Furthermore, the ON / OFF signal S80 is generated so that the ON / OFF signal S80 is turned OFF after the time obtained by adding the duty "Duty" and the predetermined duration β has elapsed after the ON / OFF signal S40 is turned OFF.

[0091] When the ON / OFF signal S70 and the ON / OFF signal S80 are generated as described above, it is possible to reduce a circulating current that occurs during a period in which the ON of the ON / OFF signal S30 and the ON of the ON / OFF signal S50 overlap, and during a period in which the ON of the ON / OFF signal S40 and the ON of the ON / OFF signal S60 overlap. Furthermore, it is possible to supply the load 110 with surge energy accumulated in the snubber capacitor 25 of the secondary side circuit of the DC-DC converter 400. Accordingly, it is possible to achieve high efficiency of the DC-DC converter 400.

[0092] Then, the switching signal generation unit 335 generates the ON / OFF signal S90 of the MOSFET 270. The ON / OFF signal S90 is turned ON with a delay of a predetermined standby time α2 after the ON / OFF signal S70 is turned OFF. Furthermore, the ON / OFF signal S90 is generated to be turned OFF simultaneously with the OFF of the ON / OFF signal S30.

[0093] Then, the switching signal generation unit 335 generates the ON / OFF signal S100 of the MOSFET 280. The ON / OFF signal S100 is turned ON with a delay of the predetermined standby time α2 after the ON / OFF signal S80 is turned OFF. Furthermore, the ON / OFF signal S100 is generated so that it is turned OFF simultaneously with the OFF of the ON / OFF signal S40.

[0094] When the ON / OFF signal S90 and the ON / OFF signal S100 are generated as described above, it is possible to reduce a current flowing through a parasitic diode of the MOSFET 270 and the MOSFET 280. This means that synchronous rectification is possible, and thus high efficiency of the DC-DC converter 400 can be achieved.

[0095] However, in order to achieve zero-voltage switching in addition to preventing short-circuiting of the upper and lower arms of the MOSFETs in the respective phases of the DC-DC converter 400, it is preferable to provide a dead time to the ON / OFF signals S30 to S60 of the MOSFETs 210 to 240 of the DC-DC converter 400. Furthermore, if the duty input "Duty" to the switching signal generation unit 335 is 0 (zero), the switching signal generation unit 335 generates the ON / OFF signals S30 to S100 of the MOSFETs 210 to 280 of the DC-DC converter 400 so that all the ON / OFF signals are turned OFF. (Gate driver circuit 340)

[0096] The gate drive circuit 340, provided to the controller 310 of the DC-DC converter 400, converts the ON / OFF signals S30 to S100 input from the switching signal generation unit 335 into gate voltages V30 to V100. Furthermore, the gate drive circuit 340 inputs the converted gate voltages V30 to V100 to the gates of the MOSFETs 210 to 280 of the DC-DC converter 400. Accordingly, the MOSFETs 210 to 240 of the DC-DC converter 400 are turned ON / OFF according to the gate voltages V30 to V100. (Relationship between input voltage, output voltage and output current)

[0097] Next, with reference to Fig. 7 and Fig. 8 describes a relationship between the input voltage V5, the output voltage V10 and the output current I10 of the DC-DC converter 400, which is achieved by using the first embodiment of the invention. (For input voltage transitions from the second range to the first range)

[0098] Fig. 7 is a view illustrating a relationship between the input voltage V5, the output voltage V10, and the output current I10 when the input voltage V5 transitions from the second region to the first region under conditions where the output voltage V10 of the DC-DC converter 400 according to the first embodiment of the invention is greater than the lower limit V10LLim and the load current is constant.

[0099] In Fig. 7, however, an upper limit V5HLim is a value that expresses a digital value of the upper limit VD5HLim as an analog value. An upper limit V10HLim is a value that expresses a digital value of the upper limit VD10HLim as an analog value. The lower limit V10LLim is a value that expresses a digital value of the lower limit VD10LLim as an analog value. An output current limit value I10Lim is a value that expresses a digital value of the output current limit value ID10Lim as an analog value.

[0100] In Fig. 7, the input voltage V5 first belongs to the second range. At this time, the command generation unit 325 sets the input voltage V5 in step a10 of Fig. 3, the output voltage command VD10ref is set to a predetermined output voltage value corresponding to the input voltage VD5. As described above, the output voltage command VD10ref increases linearly with respect to the increase in the input voltage VD5. Furthermore, in step a11, the command generation unit 325 sets the output current limit value ID10Lim to the upper limit ID10HLim.

[0101] In addition, the output current limit value I10Lim is greater than the output current I10. At this time, the workload generation unit 330 calculates in step b8 of Fig. 4, a deviation Dev, which is a difference between an output voltage command value VD10 and the output voltage VD10. Furthermore, in step b11, the duty generation unit 330 calculates the duty "Duty" to set the deviation Dev to 0 (zero). In a region (a), the output current limit value I10Lim is greater than the output current I10, and it enters a mode in which it regulates the output voltage V10.

[0102] The switching signal generation unit 335 generates an ON / OFF signal of a MOSFET based on the duty cycle, so that an output voltage command and an output voltage are matched. Therefore, the output voltage VD10 increases in combination with the increase in the input voltage V5.

[0103] In addition, when the input voltage V5 increases and reaches the first range, the command generation unit 325 in step a8 of Fig. 3 sets the output current limit value I10Lim to a predetermined output current value that decreases linearly with respect to the increase in the input voltage VD5. That is, the output current limit value I10Lim decreases in combination with the increase in the input voltage V5. Furthermore, during a period in which the output current limit value I10Lim is greater than the output current I10, as described above, it enters the mode in which it regulates the output voltage V10 of the DC-DC converter 400, and thus the output voltage V10 continuously decreases in combination with the increase in the input voltage V5.

[0104] In addition, when the output current limit value I10Lim decreases and becomes equal to or smaller than the output current I10, the workload generation unit 330 is switched to a mode in which it regulates the output current I10, as in steps b12 to b14 of Fig. 4. When the workload generation unit 330 is switched from the output voltage V10 regulation mode to the output current I10 regulation mode, a MOSFET is regulated so that the output current I10 is equal to the output current limit value I10Lim. The output current limit value I10Lim decreases in combination with the increase in the input voltage VD5, and as a result, the output current I10 decreases.

[0105] In addition, when the output current I10 becomes smaller than the load current, a current is supplied from the low-voltage-side battery 100 to the load 110. Accordingly, the output voltage V10 decreases in combination with the decrease in the output current I10.

[0106] In addition, the command generation unit 325 provides in step a6 of Fig. 3 sets the output current limit value I10Lim to 0 (zero) when the input voltage V5 reaches an upper limit V5lim. The workload generation unit 330 detects the output current limit value I10Lim and sets it in step b6 of Fig. 4 sets the duty cycle to 0 (zero). Accordingly, all MOSFETs 210 to 280 of the DC-DC converter 400 are turned off, and as a result, the output current I10 becomes 0 (zero). (For input voltage transitions from the third range to the fourth range)

[0107] Fig. 8 is a view illustrating a relationship between the input voltage V5, the output voltage V10, and the output current I10 when the input voltage V5 transitions from the third region to the fourth region under conditions where the output voltage V10 of the DC-DC converter 400 according to the first embodiment of the invention is larger than the lower limit V10LLim and the load current increases.

[0108] In Fig. 8, the input voltage V5 first belongs to the third range. At this time, the command generation unit 325 sets the input voltage V5 in step a13 of Fig. 3, the output voltage command VD10ref is set to a reference voltage value VD10st. As described above, the output voltage command VD10ref is set to a constant value. Furthermore, in step a11, the command generation unit 325 sets the output current limit value ID10Lim to the upper limit ID10HLim.

[0109] At this time, the workload generation unit 330 enters the mode of regulating the output voltage V10 because the output current limit value I10Lim is greater than the output current I10. The output voltage command VD10ref is set to the reference voltage value VD10st, and thus the output voltage V10 is regulated to a constant value. Furthermore, the load current is constant, and thus the output current I10 is also regulated to a constant value.

[0110] In addition, when the input voltage V5 decreases and reaches the fourth range, the command generation unit 325 in step a17 of Fig. 3, the command generation unit 325 sets the output voltage command VD10ref to a predetermined output voltage value that decreases linearly with respect to the decrease in the input voltage VD5. Furthermore, in step a18, the command generation unit 325 sets the output current limit value ID10Lim to a predetermined current value that decreases linearly with respect to the decrease in the input voltage VD5.

[0111] Since the output current limit value I10Lim is greater than the output current I10, the workload generation unit 330 enters the mode of regulating the output voltage V10. Accordingly, the output voltage V10 decreases based on the output voltage command VD10ref.

[0112] On the other hand, if the output current limit value I10Lim is equal to or smaller than the output current I10 as described above, even in a case where the load current increases, it is possible to decrease the output current I10 in combination with the increase in the input voltage V5 because the work load generation unit 330 enters the mode of regulating the output current I10.

[0113] In the related art, only the output voltage is regulated, and therefore the output current increases in conjunction with the increase in the load current. Since the output current is limited according to the magnitude of the input voltage of the DC-DC converter, the invention makes it possible to reduce the output current in conjunction with the decrease in the input voltage, regardless of a change in the load current.

[0114] In addition, when the output current I10 becomes smaller than the load current, a current is supplied from the low-voltage-side battery 100 to the load 110. Accordingly, the output voltage V10 decreases in combination with the decrease in the output current I10.

[0115] In addition, the method for limiting the output current of the DC-DC converter is not dependent on the circuit configuration of the Fig. 1, and other circuit configurations may be applied. Second embodiment (hybrid vehicle system including a DC-DC converter)

[0116] Fig. 9 is a view illustrating a hybrid vehicle system including a DC-DC converter 405 according to a second embodiment of the invention. In the DC-DC converter 400 according to the first embodiment of the invention, the input voltage V5, the output voltage V10, and the output current I10 of the DC-DC converter 400 are detected, and the output voltage V10 and the output current I10 of the DC-DC converter 400 are controlled to a predetermined value according to the magnitude of the input voltage V5 that is detected. In this embodiment, an input voltage V5, an output voltage V10, and an input current I15 of a DC-DC converter 405 are detected, and the output voltage V10 and the input current I15 of the DC-DC converter 405 are controlled to a predetermined value according to the magnitude of the input voltage V5 that is detected.The configuration of the hybrid vehicle system is the same as that in the first embodiment of the invention except for the DC-DC converter 405, and therefore, a description thereof is omitted.

[0117] The DC-DC converter 405 according to the second embodiment of the invention includes a filter capacitor 20, a voltage sensor 192, a current sensor 205, MOSFETs 210, 220, 230, and 240, and a resonant reactor 30 in a primary-side circuit. In the filter capacitor 20, one end of the filter capacitor 20 is connected to a high-potential side of the high-voltage battery 10, and the other end of the filter capacitor 20 is connected to one end of the current sensor 205. The other end of the current sensor 205 is connected to a low-potential side of the high-voltage battery 10. In the voltage sensor 192, one end of the voltage sensor 192 is connected to the high-potential side of the high-voltage battery 10, and the other end of the voltage sensor 192 is connected to one end of the current sensor 205.

[0118] The high-potential side of the high-voltage battery 10 is connected to a drain of the MOSFET 210 and a drain of the MOSFET 230. The other end of the current sensor 205 is connected to a source of the MOSFET 220 and a source of the MOSFET 240. A source of the MOSFET 210 is connected to a drain of the MOSFET 220 and one end of the resonant choke 30. The other end of the resonant choke 30 is connected to one end of a primary-side winding 40 of a transformer 50. The other end of the primary-side winding 40 of the transformer 50 is connected to a source of the MOSFET 230 and a drain of the MOSFET 240.

[0119] The DC-DC converter 405 includes a smoothing capacitor 90, a smoothing choke 80, a snubber capacitor 25, a voltage sensor 190, and MOSFETs 250, 260, 270, and 280 in a secondary side circuit.

[0120] One end of a secondary-side winding 60 of transformer 50 is connected to a source of MOSFET 260 and a drain of MOSFET 280. The other end of the secondary-side winding 60 of transformer 50 is connected to one end of a secondary-side winding 70 of transformer 50 and one end of smoothing reactor 80. The other end of the secondary-side winding 70 of transformer 50 is connected to a source of MOSFET 250 and a drain of MOSFET 270.

[0121] A drain of MOSFET 250 and a drain of MOSFET 260 are connected to snubber capacitor 25. The other end of snubber capacitor 25 is connected to a source of MOSFET 270 and a source of MOSFET 280.

[0122] The other end of the smoothing choke 80 is connected to one end of the smoothing capacitor 90 and one end of the voltage sensor 190. The other end of the smoothing capacitor 90 and the other end of the voltage sensor 190 are connected to the other end of the snubber capacitor 25.

[0123] A high-potential side of the low-voltage battery 100 is connected to one end of the smoothing capacitor 90, one end of the voltage sensor 190, and the other end of the smoothing reactor 80. A low-potential side of the low-voltage battery 100 is connected to the other end of the smoothing capacitor 90, the other end of the voltage sensor 190, and a ground of a vehicle. Furthermore, one end of the load 110 is connected to the high-potential side of the low-voltage battery 100, and the other end of the load 110 is connected to a low-potential side of the low-voltage battery 100.

[0124] The DC-DC converter 405 includes the voltage sensor 192 connected in parallel with the high-voltage-side battery 10, the voltage sensor 190 connected in parallel with the low-voltage-side battery 100, and the current sensor 205 connected in series with the high-voltage-side battery 10. The voltage sensor 192 detects an input voltage V5 of the DC-DC converter 400. The voltage sensor 190 detects an output voltage V10 of the DC-DC converter 400. The current sensor 205 detects an input current I15 of the DC-DC converter 400.

[0125] A controller 315 of the DC-DC converter 405 generates a gate voltage V30 configured to control ON / OFF of MOSFET 210, which is a switching element of the DC-DC converter 405, based on the input voltage V5, the output voltage V10, and the input current I15, and inputs the generated gate voltage V30 to a gate of the MOSFET 210. As described below, the controller 310 of the DC-DC converter 400 inputs a gate voltage V40 to a gate of the MOSFET 220, inputs a gate voltage V50 to a gate of the MOSFET 230, inputs a gate voltage V60 to a gate of the MOSFET 240, inputs a gate voltage V70 to a gate of the MOSFET 250, inputs a gate voltage V80 to a gate of the MOSFET 260, inputs a gate voltage V90 to a gate of the MOSFET 270, and inputs a gate voltage V100 to a gate of the MOSFET 280. (DC-DC converter control device 315)

[0126] Fig. 10 is a view illustrating a control device 315 of the DC-DC converter 405 according to the second embodiment of the invention. The control device 315 of the DC-DC converter 405 includes an A / D converter 320 that converts an analog value into a digital value, a command generation unit 327, a workload generation unit 332, a switching signal generation unit 335, and a gate drive circuit 340.

[0127] The A / D converter 320 converts an analog value of the input voltage V5 of the DC-DC converter 405, which is detected by the voltage sensor 192, into a digital value VD5. Furthermore, the A / D converter 320 converts an analog value of the output voltage V10 of the DC-DC converter 405, which is detected by the voltage sensor 190, into a digital value VD10. Furthermore, the A / D converter 320 converts an analog value of the input current I15 of the DC-DC converter 405, which is detected by the current sensor 205, into a digital value ID15.

[0128] The command generation unit 327 generates an output voltage command VD10ref and an input current limit value ID15Lim of the DC-DC converter 405 based on the digital value VD5 (hereinafter referred to as input voltage VD5 of the DC-DC converter 405) representing the input voltage V5 of the DC-DC converter 405 detected by the voltage sensor 192 and the digital value VD10 (hereinafter referred to as output voltage VD10 of the DC-DC converter 405) representing the output voltage V10 of the DC-DC converter 405 detected by the voltage sensor 190.

[0129] The duty generation unit 332 generates a duty “Duty” of each of the MOSFETs 210, 220, 230, and 240 based on the output voltage command VD10ref and the input current limit value ID10Lim of the DC-DC converter 405 generated by the command generation unit 327, the output voltage VD10 of the DC-DC converter 405 output from the A / D converter 320, and the digital value ID15 (hereinafter referred to as input current ID15 of the DC-DC converter 405) representing the input current I15.

[0130] The switching signal generation unit 335 generates the ON / OFF signals S30, S40, S50, S60, S70, S80, S90 and S100 of the MOSFETs 210, 220, 230, 240, 250, 260, 270 and 280 of the DC-DC converter 405 based on the duty of the MOSFETs 210, 220, 230 and 240 of the DC-DC converter 405 generated by the duty generation unit 332.

[0131] The gate driver circuit 340 generates the gate voltages V30 to V100 configured to turn on and off the MOSFETs 210 to 280 of the DC-DC converter 405 based on the ON / OFF signals S30 to S100 of the MOSFETs 210 to 280 of the DC-DC converter 405 generated by the switching signal generating unit 335. (Command generation unit 327)

[0132] Fig. 11 is a view illustrating the command generation unit 327 provided to the control device 315 of the DC-DC converter 405 according to the second embodiment of the invention. A method for generating the output voltage command VD10ref using the command generation unit 327 provided to the control device 315 of the DC-DC converter 405 according to the second embodiment of the invention is the same as in the first embodiment, and therefore, the description thereof will not be repeated. As in the first embodiment of the invention, the command generation unit 327 determines four ranges similar to Expression (1) in advance with respect to the input voltage VD5 of the DC-DC converter 405.

[0133] First, in step c1, which is Fig. As shown in Fig. 11, the command generation unit 327 detects the input voltage VD5 of the DC-DC converter 405 output from the A / D converter 320 (hereinafter simply referred to as input voltage VD5) and acquires the output voltage VD10 of the DC-DC converter 405 (hereinafter simply referred to as output voltage VD10) in step c2. Then, the command generation unit 327 determines whether the input voltage VD5 acquired in step c1 belongs to the first range or not in step c3. (If the input voltage belongs to the first range)

[0134] If it is determined in step c3 that the input voltage VD5 belongs to the first range, the command generation unit 327 determines in step c4 whether or not the input voltage VD5 is equal to or greater than the upper limit VD5HLim.

[0135] If it is determined in step c4 that the input voltage VD5 is equal to or greater than the upper limit VD5HLim, the command generation unit 327 sets the output voltage command VD10ref of the DC-DC converter 405 in step c5 using the same method used in the first embodiment of the invention. Furthermore, the command generation unit 327 sets the input current limit value ID15Lim to 0 (zero) in step c6.

[0136] In addition, the command generation unit 327 inputs the output voltage command VD10ref set in step c5 and the input current limit value ID15Lim set in step c6 to the workload command generation unit 332.

[0137] When the input current limit value ID15Lim of the DC-DC converter 405 is set as described above, it is possible to turn off all MOSFETs 210 to 240 of the primary-side circuit of the DC-DC converter 405 before the total voltage V5 consisting of the input voltage V5 and a surge voltage occurring due to the switching of the MOSFETs 210 to 240 exceeds a test voltage of the MOSFETs 210 to 240. Furthermore, it is possible to turn off all MOSFETs 250 to 280 before the total voltage consisting of a voltage supplied to the secondary-side circuit via the transformer 50 and a surge voltage occurring due to the switching of the MOSFETs 250 to 280 exceeds a test voltage of the MOSFETs 250 to 280. Therefore, it is possible to prevent an overvoltage fault of the MOSFETs 210 to 280.

[0138] On the other hand, if it is determined in step c4 that the input voltage VD5 is less than the upper limit VD5HLim, the command generation unit 327 sets the output voltage command VD10ref of the DC-DC converter 405 in step c7 using the same method used in the first embodiment of the invention. Furthermore, in step c8, the command generation unit 327 sets the input current limit value ID15Lim to a predetermined input current value corresponding to the input voltage VD5 detected in step c1.

[0139] In addition, the command generation unit 327 inputs the output voltage command VD10ref set in step c7 and the input current limit value ID15Lim set in step c8 to the workload command generation unit 332.

[0140] When the output voltage command VD10ref of the DC-DC converter 405 is set in the same manner as in the first embodiment, even in a case where the input voltage V5 of the DC-DC converter 405 changes, it is possible to suppress a rapid change in the output voltage V10 of the DC-DC converter 405.

[0141] In addition, the predetermined input current value set as the input current limit value ID15Lim of the DC-DC converter 405 is linearly increased with respect to an increase in the detected input voltage VD5 of the DC-DC converter 405 and linearly increased with respect to a decrease in the detected input voltage VD5 of the DC-DC converter 405. In addition, the predetermined input current value is linearly changed from 0 (zero) to the upper limit ID15HLim determined in advance with respect to the input current ID15 of the DC-DC converter 405 (hereinafter simply referred to as the input voltage ID15) in accordance with a change in the detected input voltage VD5 of the DC-DC converter 405.

[0142] By setting the input current limit value ID15Lim of the DC-DC converter 405 as described above, even in a case where the input voltage V5 changes, it is possible to suppress a rapid change in the input current I15. Accordingly, underload operation of the input current limit I15 can be stabilized, thus improving the reliability of the DC-DC converter 405. (If the input voltage belongs to the second range)

[0143] On the other hand, if it is determined in step c3 that the input voltage VD5 does not belong to the first range, the command generation unit 327 determines in step c9 whether the input voltage VD5 belongs to the second range or not.

[0144] If it is determined in step c9 that the input voltage VD5 belongs to the second range, that is, if the high-voltage-side battery 10 is likely to reach an overcharged state, the command generation unit 327 sets the output voltage command VD10ref of the DC-DC converter 405 in step c10 using the same method used in the first embodiment of the invention. Furthermore, in step c11, the command generation unit 327 sets the input current limit value ID15Lim to the upper limit ID15HLim.

[0145] In addition, the command generation unit 327 inputs the output voltage command VD10ref set in step c10 and the input current limit value ID15Lim set in step c11 to the workload command generation unit 332.

[0146] When the output voltage command VD10ref of the DC-DC converter 405 is set in the same manner as in the first embodiment, even in a case where the input voltage V5 of the DC-DC converter 405 changes, it is possible to suppress a rapid change in the output voltage V10 of the DC-DC converter 405. In addition, the input current limit value ID15Lim is set to the upper limit ID15HLim, and thus it is possible to increase the input current I15 of the DC-DC converter 405 in combination with the increase in the input voltage V5 of the DC-DC converter 405. That is, it is possible to increase the electric power drawn from the high-voltage-side battery 10 in combination with the increase in the input voltage V5 of the DC-DC converter 405, and thus it is possible to suppress the increase in the voltage of the high-voltage-side battery 10.Accordingly, it is possible to suppress overcharging of the high-voltage side battery 10. (If the input voltage belongs to the third range)

[0147] On the other hand, if it is determined in step c9 that the input voltage VD5 does not belong to the second range, the command generation unit 327 determines in step c12 whether the input voltage VD5 belongs to the third range or not.

[0148] If it is determined in step c12 that the input voltage VD5 belongs to the third range, that is, if the high-voltage-side battery 10 is less likely to reach an over-discharged state or an over-charged state, the command generation unit 327 sets the output voltage command VD10ref of the DC-DC converter 405 in step c13 using the same method used in the first embodiment of the invention. Furthermore, the command generation unit 327 sets the input current limit value ID15Lim to the upper limit ID15HLim in step c11.

[0149] In addition, in step c13, the command generation unit 327 inputs the output voltage command VD10ref set in step c13 and the input current limit value ID15Lim set in step c11 to the workload command generation unit 332.

[0150] When the output voltage command VD10ref and the input current limit value ID15Lim of the DC-DC converter 405 are set as described above, even in a case where the input voltage VD5 transitions from the third range to the second range, or even in a case where the input voltage VD5 transitions from the third range to the fourth range, it is possible to suppress a rapid change in the output voltage V10. Furthermore, it is possible to prevent the high-voltage-side battery 10 and the low-voltage-side battery 100 from being over-discharged or over-charged. (If the input voltage belongs to the fourth range)

[0151] On the other hand, if it is determined in step c12 that the input voltage VD5 does not belong to the third range, the command generation unit 327 determines in step c14 that the input voltage VD5 belongs to the fourth range. That is, the command generation unit 327 determines that the high-voltage-side battery 10 is very likely to reach an over-discharge state.

[0152] Then, in step c15, the command generation unit 327 determines whether or not the output voltage VD10 is equal to or less than the lower limit VD10LLim.

[0153] If it is determined in step c15 that the output voltage VD10 is equal to or less than the lower limit VD10LLim, the command generation unit 327 sets the output voltage command VD10ref of the DC-DC converter 405 in step c16 using the same method used in the first embodiment of the invention. Furthermore, the command generation unit 327 sets the input current limit value ID15Lim to the upper limit ID15HLim in step c11.

[0154] In addition, the command generation unit 327 inputs the output voltage command VD10ref set in step c16 and the input current limit value ID15Lim set in step c11 to the workload command generation unit 332.

[0155] When the output voltage command VD10ref and the input current limit value ID15Lim of the DC-DC converter 405 are set as described above, it is possible to prevent overdischarge of the low-voltage-side battery 100. In a state of the input voltage V5 and the output voltage V10, the DC-DC converter 405 is preferably controlled as described above to give priority to preventing overdischarge of the low-voltage-side battery 100, thereby avoiding overdischarge of the high-voltage-side battery 10 due to the regeneration operation.

[0156] On the other hand, if it is determined in step c15 that the output voltage VD10 is greater than the lower limit VD10LLim, the command generation unit 327 sets the output voltage command VD10ref of the DC-DC converter 405 in step c17 using the same method used in the first embodiment of the invention. Furthermore, in step c18, the command generation unit 327 sets the input current limit value ID15Lim to a predetermined input current value corresponding to the input voltage VD5 of the DC-DC converter 405.

[0157] In addition, the command generation unit 327 inputs the output voltage command VD10ref set in step c17 and the input current limit value ID15Lim set in step c18 to the workload command generation unit 332.

[0158] When the output voltage command VD10ref of the DC-DC converter 405 is set exactly as in the first embodiment of the invention, even in a case where the input voltage V5 changes, it is possible to suppress a rapid change in the output voltage V10.

[0159] In addition, the preset input current value, which is set as the input current limit value ID15Lim of the DC-DC converter 405, is linearly increased with the increase in the detected input voltage VD5 and linearly decreased with the decrease in the input voltage VD5. Furthermore, the preset input current value is linearly changed from 0 (zero) to the upper limit ID15HLim according to the change in the input voltage VD5.

[0160] When the input current limit value ID15Lim of the DC-DC converter 405 is set as described above, it is possible to suppress a rapid change in the input current I15 even when the input voltage V5 changes. Furthermore, it is possible to limit the input current I15 regardless of a change in the load current, and thus it is possible to reduce the input current I15 in combination with the decrease in the input voltage V5. That is, it is possible to reduce the electric power drawn from the high-voltage-side battery 10 in combination with the decrease in the input voltage V5 regardless of the magnitude of the load current, and thus it is possible to suppress over-discharge of the high-voltage-side battery 10. (Workload generation unit 332)

[0161] Fig. 12 is a view illustrating the workload generation unit 332 provided to the control device 315 of the DC-DC converter 405 according to the second embodiment of the invention. The configuration of the proportional-integral controller unit 600 provided to the command generation unit 327 of the control device 315 of the DC-DC converter 405 according to the second embodiment of the invention is the same as that in the first embodiment, and therefore, the description thereof will not be repeated. As shown in Fig. As shown in Figure 10, the workload generation unit 332 acquires the output voltage command VD10ref and the input current limit value ID15Lim of the DC-DC converter 405 output from the command generation unit 327, and the output voltage VD10 and the input current ID15 of the DC-DC converter 405 output from the A / D converter 320. A description follows with reference to Fig. 12. In step d1, the workload generation unit 332 acquires the output voltage command VD10ref, acquires the input current limit value ID15Lim in step d2, acquires the output voltage VD10 in step d3, and acquires the input current ID15 in step d4.

[0162] Then, in step d5, the workload generation unit 332 determines whether the input current limit value ID15Lim of the DC-DC converter 405 detected in step d2 is 0 (zero).

[0163] If it is determined in step d5 that the input current limit value ID15Lim of the DC-DC converter 405 being detected is 0 (zero), the duty generation unit 332 sets a duty "Duty" to 0 (zero) in step d6. Furthermore, the duty generation unit 332 inputs the set duty "Duty" to the switching signal generation unit 335.

[0164] If the duty is calculated as described above, it is possible to turn off all MOSFETs 210 to 280, which are switching elements of the DC-DC converter 405.

[0165] On the other hand, if it is determined in step d5 that the input current limit value ID15Lim of the DC-DC converter 405 being detected is not 0 (zero), the workload generation unit 332 determines in step d7 whether the input current limit value ID15Lim of the DC-DC converter 405 being detected is greater than the input current ID15.

[0166] If it is determined in step d7 that the input current limit value ID15Lim of the detected DC-DC converter 405 is greater than the input current ID15, the workload generation unit 332 calculates a deviation Dev in step d8 by subtracting the output voltage VD10 from the output voltage command VD10ref of the detected DC-DC converter 405. Further, in step d9, the workload generation unit 332 sets a proportional gain Kpv for controlling the output voltage to a proportional gain Kp, which is input to the proportional-integral control unit 600 in the same manner as in the first embodiment of the invention. Further, in step d10, the workload generation unit 332 sets an integral gain Kiv for controlling the output voltage to an integral gain Ki.

[0167] Furthermore, in step d11, the workload generation unit 332 inputs the deviation Dev calculated in step d11 and the adjusted proportional gain Kp and integral gain Ki to the proportional-integral controller unit 600, and calculates a workload Duty configured to set the deviation Dev to 0 (zero) based on the proportional-integral controller unit 600. Furthermore, the workload generation unit 332 inputs the calculated workload "Duty" to the switching signal generation unit 335.

[0168] If the duty is calculated as described above, it is possible to adjust the output voltage VD10 of the DC-DC converter 405 to the output voltage command VD10ref.

[0169] On the other hand, if it is determined in step d7 that the input current limit value ID15Lim of the DC-DC converter 405 being detected is equal to or less than the input current ID15, the workload generation unit 332 calculates the deviation Dev in step d12 by subtracting the input voltage ID15 from the input current limit value ID15Lim of the DC-DC converter 405 being detected. Furthermore, in step d13, the workload generation unit 332 sets a proportional gain Kpci for controlling the input current to the proportional gain Kp, which is input to the proportional-integral control unit 600. Furthermore, in step d14, the workload generation unit 332 sets an integral gain Kici for controlling the input current to the integral gain Ki.

[0170] Furthermore, in step d11, the workload generation unit 332 inputs the deviation Dev calculated in step d11 and the proportional gain Kp and the integral gain Ki that are adjusted to the proportional-integral control unit 600, and calculates a workload Duty configured to set the deviation Dev to 0 (zero) based on the proportional-integral control unit 600. Furthermore, the workload generation unit 332 inputs the calculated workload "Duty" to the switching signal generation unit 335.

[0171] If the duty cycle is calculated as described above, it is possible to adjust the input current ID15 of the DC-DC converter 405 to the input current limit value ID15Lim.

[0172] The configuration of the switching signal generating unit 335 and the gate driving circuit 340 provided to the control device 315 of the DC-DC converter 405 according to the second embodiment of the invention is the same as that in the first embodiment, and therefore, the description thereof will not be repeated. (Relationship between input voltage, output voltage and input current)

[0173] Next, with reference to Fig. 13 and Fig. 14 describes a relationship between the input voltage V5, the output voltage V10 and the input current I15 of the DC-DC converter 405, which is achieved by using the second embodiment of the invention. (For input voltage transitions from the second range to the first range)

[0174] Fig. 13 is a view illustrating a relationship between the input voltage V5, the output voltage V10, and the input current I15 when the input voltage V5 transitions from the second region to the first region under conditions where the output voltage V10 of the DC-DC converter 405 according to the second embodiment of the invention is greater than the lower limit V10LLim and the load current is constant.

[0175] In Fig. 13 However, an upper limit V5HLim is a value that expresses a digital value of the upper limit VD5HLim as an analog value. An upper limit V10HLim is a value that expresses a digital value of the upper limit VD10HLim as an analog value. The lower limit V10LLim is a value that expresses a digital value of the lower limit VD10LLim as an analog value. An input current limit value I15Lim is a value that expresses a digital value of the input current limit value ID15Lim as an analog value.

[0176] In Fig. 13, the input voltage V5 initially belongs to the second range. If the input current limit value I15Lim is greater than the input current I15, it enters a mode in which it regulates the output voltage V10. Accordingly, the output voltage V10 increases in conjunction with the increase in the input voltage V5.

[0177] In addition, the input current limit value I15Lim decreases in combination with the increase in the input voltage V5 as the input voltage V5 increases and reaches the first range. Here, if the input current limit value I15Lim is greater than the input current I15, it enters the mode where it regulates the output voltage V10 of the DC-DC converter 405, and thus the output voltage V10 continuously increases in combination with the increase in the input voltage V5.

[0178] On the other hand, if the input current limit value I15Lim is equal to or less than the input current I15, it enters a mode in which it regulates the input current I15 of the DC-DC converter 405, and thus the input current I15 decreases in combination with the increase of the input voltage V5.

[0179] In addition, a current is supplied from the low-voltage side battery 100 to the load 110 when a value obtained by converting the input current I15 into an output current is smaller than the load current, and thus the output voltage V10 decreases in combination with the decrease of the input current I15.

[0180] In addition, all MOSFETs 210 to 280 of the DC-DC converter 405 are turned off when the input voltage V5 reaches an upper limit V5Lim, and thus the input current I15 becomes 0 (zero). (For input voltage transitions from the third range to the fourth range)

[0181] Fig. 14 is a view illustrating a relationship between the input voltage V5, the output voltage V10, and the input current I15 when the input voltage V5 transitions from the third region to the fourth region under conditions where the output voltage V10 of the DC-DC converter 405 according to the second embodiment of the invention is larger than the lower limit V10LLim and the load current increases.

[0182] In Fig. 14, the input voltage V5 initially belongs to the third range. If the input current limit value I15Lim is greater than the input current I15 and the load current is constant, the output voltage V10 and the input current I15 are regulated to a constant value regardless of any change in the input voltage V5.

[0183] In addition, when the input voltage V5 reaches the fourth range, the input current limit value I15Lim decreases in conjunction with the decrease in the input voltage V5. Here, if the input current limit value I15Lim is greater than the input current I15, the DC-DC converter 405 enters the mode where it regulates the output voltage V10, and thus the output voltage V10 decreases in conjunction with the decrease in the input voltage V5.

[0184] On the other hand, if the input current limit value I15Lim is equal to or smaller than the input current I15, it enters the mode in which it regulates the input current I15 of the DC-DC converter 405, and thus, even in a case where the load current increases, it is possible to reduce the input current I15 in combination with the increase of the input voltage V5.

[0185] In the related art, only the output voltage is regulated, and therefore the input current decreases in conjunction with the increase in the load current. However, since the input current is limited according to the magnitude of the input voltage of the DC-DC converter, the invention makes it possible to reduce the input current in conjunction with the decrease in the input voltage, regardless of the change in the load current.

[0186] In addition, a current is supplied from the low-voltage side battery 100 to the load 110 when the value obtained by converting the input current I15 into the output current becomes smaller than the load current, and thus the output voltage V10 decreases in combination with the decrease of the input current I15.

[0187] In addition, a method for limiting the input current of the DC-DC converter described above is not limited to the circuit configuration of the Fig. 9, and other circuit configurations may be applied. Furthermore, when this embodiment and the first embodiment of the invention are combined, it is also possible to regulate each input current and output current of the DC-DC converter to a predetermined value according to the magnitude of the input voltage of the DC-DC converter. Third embodiment

[0188] In the workload generation unit 330 provided to the control device 310 of the DC-DC converter 400 according to the first embodiment of the invention, the output voltage and the output current of the DC-DC converter 400 are controlled based on a comparison result of the output current limit value ID10Lim and the output current ID10.

[0189] Furthermore, in the workload generation unit 332 provided to the control device 315 of the DC-DC converter 405 according to the second embodiment of the invention, the output voltage and the input current of the DC-DC converter 405 are controlled based on a comparison result of the input current limit value ID15Lim and the input current ID15.

[0190] In this embodiment, an output voltage and an input current or an output current of a DC-DC converter are controlled based on a comparison result of an input current limit value or output current limit value IDXLim and an input current or an output current IDX. However, in the following description, the input current limit value or output current limit value IDXLim of the DC-DC converter output from a command generation unit is referred to as current limit value IDXLim for convenience. Furthermore, the input current or output current IDX of the DC-DC converter that is detected is simply referred to as current IDX. (DC-DC converter control device 319)

[0191] Fig. 15 is a view illustrating a control device 319 of the DC-DC converter according to a third embodiment of the invention. The control device 319 includes an A / D converter 320, a command generation unit 329, a workload generation unit 334, a switching signal generation unit 335, and a gate drive circuit 340.

[0192] The command generation unit 329 according to this embodiment generates an output voltage command VD10ref of a DC-DC converter and an input current limit value or an output current limit value IDXLim (current limit value IDXLim) of the DC-DC converter based on a digital value VD5 (hereinafter referred to as an input voltage VD5) representing an input voltage V5 of the DC-DC converter detected by the voltage sensor 192 and a digital value VD10 (hereinafter referred to as an output voltage VD10) representing an output voltage V10 of the DC-DC converter detected by the voltage sensor 190. The configuration of the command generation unit 329 according to this embodiment is the same as that in the first embodiment or the second embodiment, and therefore, its description will not be repeated.

[0193] In addition, the configuration of the DC-DC converter except for the command generation unit 329 and the workload generation unit 334 according to this embodiment is the same as that in the first embodiment or the second embodiment of the invention, and therefore, the description thereof will not be repeated. (Workload generation unit 334)

[0194] Fig. 16 is a view illustrating the workload generation unit 334 provided to the control device of the DC-DC converter according to the third embodiment of the invention. As shown in Fig. 15, the workload generation unit 334 acquires the output voltage command VD10ref and the current limit value IDXLim of the DC-DC converter output from the command generation unit 329, and the output voltage VD10 and an input current IDX of the DC-DC converter output from the A / D converter 320. A description will be given below with reference to Fig. 16. The workload generation unit 334 acquires an output current command VD10ref in step e1, acquires the current limit value IDXLim in step e2, acquires the output voltage VD10 in step e3, and acquires the current IDX in step e4.

[0195] Then, in step e5, the workload generation unit 334 determines whether the current limit value IDXLim of the DC-DC converter detected in step e2 is 0 (zero).

[0196] If it is determined in step e5 that the current limit value IDXLim being acquired is 0 (zero), the duty generation unit 334 sets a duty "Duty" to 0 (zero) in step e6. Furthermore, the duty generation unit 334 inputs the set duty "Duty" to the switching signal generation unit 335.

[0197] If the duty is calculated as described above, it is possible to turn off all MOSFETs, which are switching elements of the DC-DC converter.

[0198] On the other hand, if it is determined in step e5 that the current limit value IDXLim being detected is not 0 (zero), the workload generation unit 334 determines in step e7 whether the current limit value IDXLim is greater than the current IDX.

[0199] If it is determined in step e7 that the current limit value IDXLim is greater than the current IDX, the workload generation unit 334 calculates a voltage deviation DevV in step e8 by subtracting the output voltage VD10 from the output voltage command VD10ref of the DC-DC converter that is detected. Furthermore, the workload generation unit 334 sets a current deviation DevC to 0 (zero) in step e9.

[0200] Then, in step e10, the workload generation unit 334 determines whether a state in which the current limit value IDXLim is greater than the current IDX continues.

[0201] If it is determined in step e10 that the state in which the current limit value IDXLim is greater than the current IDX continues, that is, if the current limit value IDXLim detected before one duty cycle is greater than the current IDX detected before one duty cycle, the workload generation unit 334 sets a voltage regulation switching flag FlagV to OFF in step e11. Further, in step e12, the workload generation unit 334 inputs the voltage deviation DevV calculated in step e8, the current deviation DevC set in step e9, and the voltage regulation switching flag FlagV set in step e11 to a voltage and current regulation unit 606, and calculates a workload "Duty" configured to set the voltage deviation DevV to 0 (zero) based on the voltage and current regulation unit 606.In addition, the workload generation unit 334 inputs the calculated workload “Duty” to the switching signal generation unit 335.

[0202] On the other hand, if it is determined in step e10 that the state where the current limiting value IDXLim is greater than the current IDX does not continue, that is, if the current limiting value IDXLim detected before one duty cycle is equal to or less than the current IDX detected before one duty cycle, the workload generation unit 334 sets the voltage regulation switching flag FlagV to ON in step e13. Further, in step e12, the workload generation unit 334 inputs the voltage deviation DevV calculated in step e8, the current deviation DevC set in step e9, and the voltage regulation switching flag FlagV set in step e13 to the voltage and current regulation unit 606, and calculates a workload "Duty" configured to set the voltage deviation DevV to 0 (zero) based on the voltage and current regulation unit 606.In addition, the workload generation unit 334 inputs the calculated workload “Duty” to the switching signal generation unit 335.

[0203] If the duty is calculated as described above, it is possible to adjust the output voltage VD10 of the DC-DC converter to the output voltage command VD10ref.

[0204] On the other hand, if it is determined in step e7 that the current limit value IDXLim is equal to or less than the current IDX, the workload generation unit 334 sets the voltage deviation DevV to 0 (zero) in step e14. Furthermore, in step e15, the workload generation unit 334 calculates the current deviation DevC by subtracting the current IDX from the current limit value IDXLim.

[0205] Then, in step e16, the workload generation unit 334 determines whether the state in which the current limit value IDXLim is equal to or less than the current IDX continues.

[0206] If it is determined in step e16 that the state in which the current limit value IDXLim is equal to or less than the current IDX continues, that is, if the current limit value IDXLim detected before one duty cycle is equal to or less than the current IDX detected before one duty cycle, the workload generation unit 334 sets a current control switching flag FlagC to OFF in step e17. Further, in step e12, the workload generation unit 334 inputs the current deviation DevC calculated in step e15, the voltage deviation DevV set in step e14, and the current control switching flag FlagC set in step e17 to the voltage and current control unit 606, and calculates a workload "Duty" configured to set the current deviation DevC to 0 (zero) based on the voltage and current control unit 606.In addition, the workload generation unit 334 inputs the calculated workload “Duty” to the switching signal generation unit 335.

[0207] On the other hand, if it is determined in step e16 that the state where the current limiting value IDXLim is equal to or less than the current IDX does not continue, that is, if the current limiting value IDXLim detected before one duty cycle is greater than the current IDX detected before one duty cycle, the workload generation unit 334 sets the current control switching flag FlagC to ON in step e18. Further, in step e12, the workload generation unit 334 inputs the current deviation DevC calculated in step e15, the voltage deviation DevV set in step e14, and the current control switching flag FlagC set in step e18 to the voltage and current control unit 606, and calculates the workload "Duty" configured to set the current deviation DevC to 0 (zero) based on the voltage and current control unit 606.In addition, the workload generation unit 334 inputs the calculated workload “Duty” to the switching signal generation unit 335.

[0208] When the duty cycle is calculated as described above, it is possible to adjust the input current or output current IDX of the DC-DC converter to the input current limit value or output current limit value IDXLim. (Voltage and current control unit 606)

[0209] Fig.17 is a view illustrating the voltage and current control unit 606 provided to the workload generation unit of the control unit of the DC-DC converter according to the third embodiment of the invention. The voltage and current control unit 606 includes a proportional-integral control unit 602 for controlling the output voltage, a proportional-integral control unit 604 (hereinafter referred to as a proportional-integral control unit 604 for current control) for controlling the input current or output current, an integrated value processing unit 685, and an adder 680.

[0210] The proportional-integral control unit 602 for controlling the output voltage includes a multiplier 640, a multiplier 645, an integrator 660, and an adder 670. The proportional-integral control unit 604 for current control includes a multiplier 650, a multiplier 655, an integrator 665, and an adder 675.

[0211] First, the voltage and current control unit 606 detects the voltage deviation DevV, the current deviation DevC, the voltage control switching flag FlagV, and the current control switching flag FlagC. Furthermore, the voltage and current control unit 606 inputs the detected voltage deviation DevV to the proportional-integral control unit 602 for controlling the output voltage. Furthermore, the voltage and current control unit 606 inputs the detected current deviation DevC to the proportional-integral control unit 604 for current control. Furthermore, the voltage and current control unit 606 inputs the detected voltage control switching flag FlagV and the current control switching flag FlagC to the integrated value processing unit 685.

[0212] If the voltage control switching flag FlagV that is input is ON, the integrated value processing unit 685 sets an integrated value of the integrator 665 provided to the proportional-integral control unit 604 for current control to an integrated value of the integrator 660 provided to the proportional-integral control unit 602 for controlling the output voltage. Furthermore, after the above-described setting is completed, the integrated value processing unit 685 sets an integrated value of the integrator 665 provided to the proportional-integral control unit 604 for current control to 0 (zero).

[0213] Furthermore, if the current control switching flag FlagC that is input is ON, the integrated value processing unit 685 sets an integrated value of an integrator 660 provided to the proportional-integral controller unit 602 for controlling the output voltage to an integrated value of the integrator 665 provided to the proportional-integral controller unit 604 for current control. Furthermore, after the above-described setting is completed, the integrated value processing unit 685 sets the integrated value of the integrator 660 provided to the proportional-integral controller unit 602 for controlling the output voltage to 0 (zero).

[0214] Then, the proportional-integral control unit 602 inputs the input voltage deviation DevV to the multiplier 640 and the multiplier 645 to control the output voltage. The multiplier 640 multiplies the input voltage deviation DevV by the proportional gain Kp to control the output voltage. A value obtained by multiplication by the multiplier 640 is input to the adder 670. The multiplier 645 multiplies the input voltage deviation DevV by the integral gain Kiv to control the output voltage. A value obtained by multiplication by the multiplier 645 is input to the integrator 660.

[0215] The integrator 660 integrates multiplied values ​​input from the multiplier 645. A value obtained by integration using the integrator 645 is input to the adder 670. The adder 670 adds the multiplied value input from the multiplier 640 and the integrated value input from the integrator 660 to calculate a duty factor DutyV for regulating the output voltage. The calculated duty factor DutyV for regulating the output voltage is input to the adder 680, which is provided to the voltage and current control unit 606.

[0216] In addition, the proportional-integral control unit 604 inputs the input current deviation DevC to the multiplier 650 and the multiplier 655. The multiplier 650 multiplies the input current deviation DevC by the integral gain Kic for current control. A value obtained by multiplication by the multiplier 650 is input to the integrator 665. The multiplier 655 multiplies the input current deviation DevC by the proportional gain Kpc for current control. A value obtained by multiplication by the multiplier 655 is input to the adder 675.

[0217] The integrator 665 integrates multiplied values ​​input from the multiplier 650. A value obtained by integration using the integrator 665 is input to the adder 675. The adder 675 adds the integrated value input from the integrator 665 and the multiplied value input from the multiplier 655 to calculate the current control duty DutyC. The calculated current control duty DutyC is input to the adder 680, which is provided to the voltage and current control unit 606.

[0218] In addition, the adder 680, provided to the voltage and current control unit 606, adds the duty DutyV for regulating the output voltage input from the adder 670 and the duty DutyC for current control input from the adder 675. The duty "Duty" added in the adder 675 is input to the switching signal generation unit 335.

[0219] When the duty "Duty" is calculated as described above, if the current limiting value IDXLim of the DC-DC converter is greater than the current IDX, the duty DutyC for current regulation becomes 0 (zero), and thus the duty "Duty" for regulating the output voltage is input to the switching signal generation unit 335. Furthermore, if the current limiting value IDXLim is equal to or greater than the current IDX, the duty DutyV for regulating the output voltage becomes 0 (zero), and thus the duty DutyC for current regulation is input to the switching signal generation unit 335.

[0220] Accordingly, when the input current limit value or the output current limit value IDXLim of the DC-DC converter is greater than the input current or the output current IDX of the DC-DC converter, it is possible to adjust the output voltage VD10 of the DC-DC converter to the output voltage command VD10ref. Furthermore, when the input current limit value or the output current limit value IDXLim of the DC-DC converter is equal to or less than the input current or the output current IDX of the DC-DC converter, it is possible to adjust the input current or the output current IDX of the DC-DC converter to the input current limit value or the output current limit value IDXLim.

[0221] Furthermore, in the above-described embodiments, the output voltage regulator and the current regulator do not interfere with each other, and thus, it is possible to set the response of the output voltage regulator to a high speed. Accordingly, in this embodiment, it is possible to achieve a stable output voltage without rapid changes in the output voltage even in a case where disturbances such as rapid changes in the load current occur. List of reference symbols 10 High-voltage side battery 20 filter capacitor 25 Snubber capacitor 30 Resonance inductor 40 Primary side transformer winding 50 transformer 60 Secondary transformer winding 70 Secondary transformer winding 80 smoothing choke 90 smoothing capacitor 100 Low-voltage side battery 110 load 190 voltage sensor 192 Voltage sensor 200 current sensor 205 Current sensor 210 MOSFET 220 MOSFET 230 MOSFET 240 MOSFET 250 MOSFET 260 MOSFET 270 MOSFET 280 MOSFET 310 DC-DC converter control device 315 DC-DC converter control device 319 DC-DC converter control device 320 A / D converters 325 Command generation unit 327 Command generation unit 329 Command generation unit 330 Workload Generation Unit 332 Workload generation unit 334 Workload generation unit 335 Switching signal generation unit 340 Gate driver circuit 360 motor generator shaft 365 Gearbox 370 crankshaft 375 engine 380 propeller shaft 400 DC-DC converters 405 DC-DC converter 500 inverters 510 Motor Generator 520 differential gear 530 drive shaft 540 drive wheel 600 Proportional-Integral Controller Unit 602 Proportional-Integral Controller Unit 604 Proportional-Integral Controller Unit 606 Voltage and current control unit 610 multipliers 615 multipliers 640 multipliers 645 multipliers 650 multipliers 655 multipliers 620 integrators 660 integrators 665 integrators 630 adders 670 adders 675 adders 680 adders 685 Integrated value processing unit S30 ON / OFF signal S40 ON / OFF signal S50 ON / OFF signal S60 ON / OFF signal S70 ON / OFF signal S80 ON / OFF signal S90 ON / OFF signal S100 ON / OFF signal V30 Gate voltage V40 gate voltage V50 gate voltage V60 gate voltage V70 gate voltage V80 gate voltage V90 gate voltage V100 Gate voltage Duty workload DutyC workload to regulate the input current or regulate the output current DutyV workload to regulate the output voltage Dev Deviation DevC current deviation DevV voltage deviation Fsw switching frequency FlagC Current control switching flag FlagV Voltage control switching flag I10 Output current I10Lim output current limit value ID10 Digital value of the output current ID10Lim Digital value of the output current limit value ID10HLim Digital value of the upper limit of the output current I15 Input current I15Lim input current limit value ID15 Digital value of the input current ID15Lim Digital value of the input current limit value ID15HLim Digital value of the upper limit of the input current IX Input current or output current IDX Digital value of the input current or output current IDXLim Digital value of the input current limit value or output current limit value V5 input voltage V5HLim upper limit of the input voltage VD5 Digital value of the input voltage VD5HLim Digital value of the upper limit of the input voltage V10 output voltage V10HLim upper limit of the output voltage V10LLim Lower limit of the output voltage VD10 Digital value of the output voltage VD10HLim Digital value of the upper limit of the output voltage VD10LLim Digital value of the lower limit of the output voltage VD10ref output voltage command VD10St Reference voltage value with respect to the output voltage

Claims

[1] A control device (310, 315, 319) of a DC-DC converter (400, 405) for charging a high-voltage-side battery (10), comprising a primary-side circuit (40) electrically connected between an input side and a transformer (50) and a secondary-side circuit (60, 70) electrically connected between an output side and the transformer, comprising: a command generation unit (325, 327, 329) that sets an output current limit value of the secondary-side circuit to a predetermined value based on a detected input voltage of the primary-side circuit; a workload generation unit (330, 332, 334) that calculates a workload configured to turn ON / OFF a switching element constituting the primary-side circuit based on the output current limit value set by the command generation unit and a detected output current of the secondary-side circuit; and a switching signal generating unit (335) that generates a switching signal of the primary-side circuit based on the workload calculated by the workload generating unit, wherein the workload generating unit generates the workload such that the output current of the secondary-side circuit is limited to the output current limit value or below, wherein the command generation unit (325, 327, 329) sets an output voltage command of the secondary-side circuit to a value determined in advance based on the detected input voltage, the workload generation unit (330, 332, 334) sets the output current limit value set by the command generation unit, and compares the detected output current, if the output current limit value set by the command generation unit is equal to or less than the detected output current, the workload generation unit calculates a workload for regulating the output current so that an output current of the secondary-side circuit is adjusted to the output current limit value set by the command generation unit, is adjusted if the output current limit value set by the command generation unit is greater than the detected output current, the workload generation unit calculates a workload to regulate the output voltage, so that an output voltage of the secondary-side circuit is adjusted to the output voltage command set by the command generation unit, the switching signal generation unit generates the switching signal based on one of the workloads: workload for regulating the output current and workload for regulating the output voltage, which are calculated by the workload generation unit, wherein the command generation unit, if the detected input voltage is greater than a first predetermined voltage, sets the output voltage command so that the output voltage command increases with respect to an increase in the detected input voltage, and sets the output current limiting value so that the output current limiting value decreases with respect to the increase in the detected input voltage. [2] The control device (310, 315, 319) of a DC-DC converter according to claim 1, wherein the workload generation unit (330, 332, 334) includes a proportional-integral controller unit (600, 602, 604) that calculates the workload based on a deviation and a gain calculated by the workload generation unit; if the output current limiting value set by the command generation unit is equal to or less than the detected output current, the workload generation unit inputs a difference between the output current limiting value and the detected output current to the proportional-integral controller unit as the deviation, and inputs a predetermined gain for controlling the output current as the gain to the proportional-integral controller unit; and if the output current limiting value set by the command generation unit is greater than the detected output current,the workload generation unit inputs a difference between the output voltage command and the detected output voltage to the proportional-integral control unit as the deviation, and inputs a predetermined gain for controlling the output voltage as the gain to the proportional-integral control unit. [3] The control device (310, 315, 319) of a DC-DC converter according to claim 2, wherein the command generation unit (325, 327, 329), if the detected input voltage is equal to or less than the first predetermined voltage and is greater than a second predetermined voltage that is less than the first predetermined voltage, sets the output current limit value to an upper limit that is equal to or greater than the output current limit value in a case where the detected input voltage is greater than the first predetermined voltage. [4] The control device (310, 315, 319) of a DC-DC converter according to claim 3, wherein the command generation unit (325, 327, 329), if the detected input voltage is equal to or less than the second predetermined voltage and greater than a third predetermined voltage which is less than the second predetermined voltage, sets the output voltage command to a predetermined reference voltage value. [5] The control device (310, 315, 319) of a DC-DC converter according to claim 4, wherein the command generation unit (325, 327, 329), if the detected input voltage is equal to or less than the third predetermined voltage, sets the output voltage command so that the output voltage command increases with respect to the increase of the detected input voltage, and sets the output current limiting value so that the output current limiting value increases with respect to the increase of the detected input voltage. [6] A control device (310, 315, 319) of a DC-DC converter for charging a high-voltage-side battery (10), comprising a primary-side circuit (40) electrically connected between an input side and a transformer (50), and a secondary-side circuit (60, 70) electrically connected between an output side and the transformer, comprising: a command generation unit (325, 327, 329) that sets an input current limit value of the primary-side circuit to a predetermined value based on a detected input voltage of the primary-side circuit; a workload generation unit (330, 332, 334) that generates a workload configured to turn on / off a switching element constituting the primary-side circuit based on the input current limit value set by the command generation unit;and the detected input current of the primary-side circuit; and a switching signal generation unit (335) that generates a switching signal of the primary-side circuit based on the workload calculated by the workload generation unit, wherein the workload generation unit generates the workload such that the input current of the primary-side circuit is limited to the input current limiting value or below, wherein the command generation unit (325, 327, 329) sets an output voltage command of the secondary-side circuit to a value determined in advance based on the detected input voltage, the workload generation unit (330, 332, 334) compares the input current limiting value set by the command generation unit and the detected input current, if the input current limiting value set by the command generation unit,is equal to or less than the detected input current, the workload generation unit calculates a workload for regulating the input current so that an input current of the primary-side circuit is adjusted to the input current limit value set by the command generation unit; if the input current limit value set by the command generation unit is greater than the detected input current, the workload generation unit calculates a workload for regulating the output voltage so that an output voltage of the secondary-side circuit is adjusted to the output voltage command set by the command generation unit; and the switching signal generation unit generates the switching signal based on one of the workloads, workload for regulating the input current and workload for regulating the output voltage, calculated by the workload generation unit.wherein the command generation unit, if the detected input voltage is greater than a first predetermined voltage, sets the output voltage command so that the output voltage command increases with respect to an increase in the detected input voltage, and sets the input current limit value so that the input current limit value decreases with respect to the increase in the detected input voltage. [7] The control device (310, 315, 319) of a DC-DC converter according to claim 6, wherein the workload generation unit (330, 332, 334) includes a proportional-integral controller unit (600, 602, 604) that calculates the workload based on a deviation and a gain calculated by the workload generation unit; if the input current limit value set by the command generation unit is equal to or less than the detected input current, the workload generation unit inputs a difference between the input current limit value and the detected input current to the proportional-integral controller unit as a deviation, and inputs a predetermined gain for controlling the input current as the gain to the proportional-integral controller unit; and if the input current limit value set by the command generation unit is greater than the detected input current,the workload generation unit inputs a difference between the output voltage command and the detected output voltage to the proportional-integral control unit as the deviation, and inputs a predetermined gain for controlling the output voltage as the gain to the proportional-integral control unit. [8] The control device (310, 315, 319) of a DC-DC converter according to claim 7, wherein the command generation unit (325, 327, 329), if the detected input voltage is equal to or less than the first predetermined voltage and is greater than a second predetermined voltage which is less than the first predetermined voltage, sets the input current limit value to an upper limit which is equal to or greater than the input current limit value in a case where the detected input voltage is greater than the first predetermined voltage. [9] The control device (310, 315, 319) of a DC-DC converter according to claim 8, wherein the command generation unit (325, 327, 329), if the detected input voltage is equal to or less than the second predetermined voltage and greater than a third predetermined voltage which is less than the second predetermined voltage, sets the output voltage command to a predetermined reference voltage value. [10] The control device (310, 315, 319) of a DC-DC converter according to claim 9, wherein the command generation unit (325, 327, 329), if the detected input voltage is equal to or less than the third predetermined voltage, sets the output voltage command so that the output voltage command increases with respect to an increase in the detected input voltage, and sets the input current limiting value so that the input current limiting value increases with respect to the increase in the detected input voltage.

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