JP2010104139A - Voltage converter and vehicle mounting it - Google Patents

Abstract

A voltage converter that realizes high efficiency while avoiding an increase in size of a component, and a vehicle on which the voltage converter is mounted.
A voltage converter is connected between a battery BAT and an inverter unit 23, and is operable by switching between a resonance mode and a hard switching mode. Converter 12 includes an IGBT element Q2A connected to reactor L1A. Control device 30 selects either the resonance mode or the hard switching mode according to the current value passing through voltage converter 12 or the target value of the current value, and sets IGBT element Q2A to realize the selected mode. Control.
[Selection] Figure 1

Description

  The present invention relates to a voltage converter and a vehicle equipped with the voltage converter, and more particularly to a voltage converter capable of operating in a resonance mode and a vehicle equipped with the voltage converter.

2. Description of the Related Art A DC-DC converter that generates a predetermined voltage DC power supply output by turning a DC power supply input on and off by a switching element is known. As a method for improving the efficiency of the DC-DC converter, a resonance type DC-DC converter is known in which a resonance capacitor is connected in parallel to a switching element for turning on / off a power input. Japanese Patent Laying-Open No. 2007-82377 (Patent Document 1) discloses such a resonance type DC-DC converter.
JP 2007-82377 A JP 2008-131760 A

  In a resonance type DC-DC converter in which a resonance capacitor is connected in parallel to a switching element, zero voltage switching is performed in a state in which a rise in voltage is suppressed by the influence of the resonance capacitor at the off timing of the driving switching element. Is realized. The resonant converter is also referred to as a soft switching converter. Further, even when the driving switching element is turned on thereafter, the reactor current is made to flow backward to create a timing at which the voltage difference between both ends of the switching element becomes zero, thereby realizing zero voltage switching. Zero voltage switching is achieved by a so-called natural commutation method to suppress loss during switching.

  However, in a resonance type DC-DC converter, it is necessary to continue flowing an internal reflux current for maintaining a resonance state. Therefore, even when the current passing through the converter is a low current, a conduction loss occurs when the circulating current is passed through the switching element, resulting in a non-resonant type (also referred to as hard switching type) DC-DC converter. Tends to be inefficient.

  FIG. 13 is a diagram comparing the current flowing through the reactors of the resonant converter and the non-resonant converter.

  Referring to FIG. 13, in order to realize an average current Im determined based on current consumption in a load connected to the converter, a current Ib flows through a reactor in a non-resonant type converter. Ia flows.

  The resonant converter must continue to pass a current for maintaining the resonance state even when the average current Im is small.

  Further, in the resonant converter, as shown by the current Ia, in order to reduce the switching loss, it is necessary to switch on the switching element after the direction of the reactor current is always reversed. In FIG. 13, moments when the current Ia becomes smaller than 0 A periodically occur.

  Therefore, in the case where the average current Im is large, the current amplitude increases because a moment when a current that is slightly below 0 A is required to invert the current. Therefore, since the peak value of the current also increases, it is necessary to select a component (reactor or switching element) having a large maximum current that can be passed. For this reason, parts become large.

  In the example of FIG. 13, the peak current value of the current Ia of the resonant converter is about twice that of the current Ib for causing the same average current Im to flow in a general hard switching (non-resonant) converter.

  In other words, the resonance type DC-DC converter has good performance in a specific current range, but if it is used in a wide current range, there is a problem that there is a region where loss is large and efficiency is low, or parts are enlarged. is there.

  An object of the present invention is to provide a voltage converter with improved efficiency and a vehicle equipped with the same.

  Another object of the present invention is to provide a voltage converter that realizes high efficiency while avoiding an increase in size of parts and a vehicle equipped with the voltage converter.

  In summary, the present invention is a voltage converter that is connected between a DC power source and a load and that can operate by switching between a resonance mode and a hard switching mode, and includes a first converter. The first converter includes a reactor and a first switching element connected to the reactor. The voltage converter further includes a control unit that performs on / off control of the first switching element. The control unit selects either the resonance mode or the hard switching mode according to the current value passing through the voltage converter or the target value of the current value, and sets the first switching element to realize the selected mode. Control.

  Preferably, the first converter further includes a capacitor connected in parallel with the first switching element at least in a resonance mode.

  More preferably, the first converter further includes a switch provided on a path connecting the capacitor in parallel with the first switching element. The control unit controls the switch to a conductive state in the resonance mode, and controls the switch to a non-conductive state in the hard switching mode.

  Preferably, one end of the reactor is connected to the positive electrode of the DC power supply. The first switching element is connected between the other end of the reactor and the negative electrode of the DC power supply. The first converter further includes a second switching element connected between the other end of the reactor and the load.

  Preferably, when the control unit is operated in the hard switching mode, the current value or the target value is set with a first threshold value defined as a boundary value that is smaller than the upper limit value of the current value that periodically causes a period in which no current flows in the reactor. When the value is smaller than the first threshold value, the hard switching mode is selected, and when the current value or the target value is larger than the first threshold value, the operation mode is switched.

  More preferably, the control unit uses the second threshold value that is larger than the first threshold value as a boundary value, and selects the resonance mode when the current value or the target value is smaller than the second threshold value. When the current value or the target value is larger than the second threshold value, the operation mode is switched so that the hard switching mode is selected.

  Preferably, the control unit selects a resonance mode when the current value or the target value is smaller than the predetermined threshold with the predetermined threshold as a boundary value, and the current value or the target value is equal to the predetermined threshold. If larger, the operation mode is switched so that the hard switching mode is selected.

  Preferably, the voltage converter further includes a second converter provided between the DC power supply and the load in parallel with the first converter. In accordance with the current value or the target value, the controller is configured to operate either one of the first and second converters and stop the other, and either the single mode or the multi-mode that operates both the first and second converters. And the first and second converters are controlled based on a combination of either the selected single mode or multimode and the selected resonance mode or hard switching mode.

  Preferably, the control unit selects one of a resonance mode and a hard switching mode according to a current value passing through the voltage converter or a target value of the current value, and realizes the selected mode, and the first mode The first switching element is controlled such that the switching frequency of the switching element is higher than a predetermined frequency.

  According to another aspect, the present invention is a vehicle on which the voltage converter according to any one of the above is mounted.

  According to the present invention, in a voltage converter, high efficiency can be achieved while avoiding an increase in the size of components. For example, when used in a vehicle, energy consumption can be reduced (fuel efficiency can be improved) while suppressing vehicle cost. it can.

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

[Embodiment 1]
FIG. 1 is a diagram illustrating a main configuration of a vehicle 100 on which the voltage converter according to the first embodiment of the present invention is mounted.

  Referring to FIG. 1, vehicle 100 includes a battery BAT, a voltage converter 12, a smoothing capacitor C2, a voltage sensor 13, an inverter unit 23, an engine 4, motor generators MG1 and MG2, and a power split mechanism. 3, wheel 2, and control device 30.

  Vehicle 100 further includes a positive electrode bus PL1 connected to the positive electrode of battery BAT, a negative electrode bus SL connected to the negative electrode of battery BAT, voltage sensor 10 for detecting voltage VL between the terminals of battery BAT, and battery BAT. Current sensor 11 for detecting current IB flowing through voltage converter 12 via positive electrode bus PL1 and positive electrode bus PL2.

  As the battery BAT, for example, a secondary battery such as a lead storage battery, a nickel metal hydride battery, or a lithium ion battery, an electric double layer capacitor, or the like can be used.

  The voltage converter 12 controls the voltage VH to about 200 to 650V. Voltage converter 12 includes a voltage converter 12A. Capacitor C2 smoothes the voltage boosted by voltage converter 12A. The voltage sensor 13 detects the inter-terminal voltage VH of the smoothing capacitor C <b> 2 and outputs it to the control device 30.

  Inverter unit 23 includes inverters 14 and 22. Inverter 14 converts the DC voltage applied from voltage converter 12 into a three-phase AC and outputs the same to motor generator MG1. Inverter 22 converts the DC voltage applied from voltage converter 12 into a three-phase AC and outputs the same to motor generator MG2.

  Power split device 3 is a mechanism that is coupled to engine 4 and motor generators MG1 and MG2 and distributes power between them. For example, as the power split mechanism, a planetary gear mechanism having three rotating shafts of a sun gear, a planetary carrier, and a ring gear can be used. These three rotation shafts are connected to the rotation shafts of engine 4 and motor generators MG1, MG2, respectively.

  The rotating shaft of motor generator MG2 is coupled to wheel 2 by a reduction gear and a differential gear (not shown). Further, a reduction gear for the rotation shaft of motor generator MG2 may be further incorporated in power split mechanism 3. Moreover, you may comprise so that the reduction ratio of this reduction gear can be switched.

  Voltage converter 12A is parallel to reactor L1A having one end connected to positive electrode bus PL1, IGBT elements Q1A and Q2A connected in series between positive electrode bus PL2 and negative electrode bus SL, and IGBT elements Q1A and Q2A, respectively. And diodes D1A and D2A connected to each other.

  Reactor L1A has the other end connected to the emitter of IGBT element Q1A and the collector of IGBT element Q2A. The cathode of diode D1A is connected to the collector of IGBT element Q1A, and the anode of diode D1A is connected to the emitter of IGBT element Q1A. The cathode of diode D2A is connected to the collector of IGBT element Q2A, and the anode of diode D2A is connected to the emitter of IGBT element Q2A.

  Inverter 14 receives voltage VH and drives motor generator MG1 to start engine 4, for example. Inverter 14 returns the electric power generated by motor generator MG 1 by the power transmitted from engine 4 to voltage converter 12. At this time, the voltage converter 12 is controlled by the control device 30 so as to operate as a step-down circuit that steps down the voltage VH to the voltage VB.

  Inverter 14 includes a U-phase arm 15, a V-phase arm 16, and a W-phase arm 17. U-phase arm 15, V-phase arm 16, and W-phase arm 17 are connected in parallel between positive electrode bus PL2 and negative electrode bus SL.

  U-phase arm 15 includes IGBT elements Q3 and Q4 connected in series between positive electrode bus PL2 and negative electrode bus SL, and diodes D3 and D4 connected in parallel with IGBT elements Q3 and Q4, respectively. The cathode of diode D3 is connected to the collector of IGBT element Q3, and the anode of diode D3 is connected to the emitter of IGBT element Q3. The cathode of diode D4 is connected to the collector of IGBT element Q4, and the anode of diode D4 is connected to the emitter of IGBT element Q4.

  V-phase arm 16 includes IGBT elements Q5 and Q6 connected in series between positive electrode bus PL2 and negative electrode bus SL, and diodes D5 and D6 connected in parallel with IGBT elements Q5 and Q6, respectively. The cathode of diode D5 is connected to the collector of IGBT element Q5, and the anode of diode D5 is connected to the emitter of IGBT element Q5. The cathode of diode D6 is connected to the collector of IGBT element Q6, and the anode of diode D6 is connected to the emitter of IGBT element Q6.

  W-phase arm 17 includes IGBT elements Q7 and Q8 connected in series between positive electrode bus PL2 and negative electrode bus SL, and diodes D7 and D8 connected in parallel with IGBT elements Q7 and Q8, respectively. The cathode of diode D7 is connected to the collector of IGBT element Q7, and the anode of diode D7 is connected to the emitter of IGBT element Q7. The cathode of diode D8 is connected to the collector of IGBT element Q8, and the anode of diode D8 is connected to the emitter of IGBT element Q8.

  Motor generator MG1 is a three-phase permanent magnet synchronous motor, and one end of each of three coils of U, V, and W phases is connected to a neutral point. The other end of the U-phase coil is connected to the connection node of IGBT elements Q3 and Q4. The other end of the V-phase coil is connected to a connection node of IGBT elements Q5 and Q6. The other end of the W-phase coil is connected to a connection node of IGBT elements Q7 and Q8.

  Other power switching elements such as power MOSFETs may be used in place of the IGBT elements Q1A, Q2A, Q3 to Q8.

  Current sensor 24 detects the current flowing through motor generator MG1 as motor current value MCRT1, and outputs motor current value MCRT1 to control device 30. Current sensor 25 detects the current flowing through motor generator MG2 as motor current value MCRT2, and outputs motor current value MCRT2 to control device 30.

  Inverter 22 is connected to positive electrode bus PL2 and negative electrode bus SL. Inverter 22 converts DC voltage VH output from voltage converter 12 </ b> A into three-phase AC and outputs the same to motor generator MG <b> 2 driving wheel 2. Inverter 22 returns the electric power generated in motor generator MG2 to voltage converter 12A along with regenerative braking. At this time, the voltage converter 12A is controlled by the control device 30 so as to operate as a step-down circuit. Although the internal configuration of inverter 22 is not shown, it is similar to inverter 14, and detailed description will not be repeated.

  Control device 30 receives torque command values TR1, TR2, motor rotational speeds MRN1, MRN2, voltages VL, VLB, VLC, VH, currents ILA, ILB, ILC, motor current values MCRT1, MCRT2, and start instruction IGON. . Control device 30 then outputs drive signal PWCA to voltage converter 12A.

  Further, control device 30 outputs drive instruction PWMI1 and regeneration instruction PWMC1 to inverter 14. Drive instruction PWMI1 is an instruction for converting a DC voltage, which is an output of voltage converter 12, into an AC voltage for driving motor generator MG1. Regenerative instruction PWMC1 is an instruction for converting the AC voltage generated by motor generator MG1 into a DC voltage and returning it to the voltage converter 12 side.

  Similarly, control device 30 outputs drive instruction PWMI2 and regeneration instruction PWMC2 to inverter 22. Drive instruction PWMI2 is an instruction to convert a DC voltage into an AC voltage for driving motor generator MG2. Regenerative instruction PWMC2 is an instruction for converting the AC voltage generated by motor generator MG2 into a DC voltage and returning it to the voltage converter 12 side.

  In FIG. 1, the vehicle may be configured such that the battery BAT can be charged from the outside of the vehicle. For example, a charger that converts the voltage of a commercial power supply of AC 100V into a DC voltage suitable for charging the battery can be mounted on the vehicle, or AC 100V can be input from the neutral point of the stator coils of motor generators MG1 and MG2. By configuring the vehicle as possible, the battery can be charged from the outside.

FIG. 2 is a diagram showing the voltage converter 12A extracted from FIG.
Referring to FIG. 2, in vehicle 100, positive electrode bus PL <b> 1 providing voltage VL is connected to battery BAT of about 200 V, and positive electrode bus PL <b> 2 applying voltage VH is connected to inverter 22 and inverter 14. 2 corresponds to the negative electrode bus SL in FIG.

  Voltage converter 12A functions as a bidirectional converter. That is, it functions as a step-up converter that steps up the voltage VL of the battery BAT to the voltage VH and also functions as a step-down converter that steps down the voltage VH to the voltage VL.

  In the voltage converter 12A of FIG. 2, the switch SW1 is set to an on state. The IGBT element Q2A is turned off in a state where a rightward current i directed to the capacitor C1A flows through the reactor L1A. However, since the capacitor C1A is connected, the collector-emitter voltage Vce of the IGBT element Q2A (voltage VM in FIG. 2) The rise of is delayed. In the meantime, by controlling the IGBT element Q2A to be turned off, the switching loss in the IGBT element Q2A is eliminated.

  Thereafter, the collector-emitter voltage Vce (voltage VM in FIG. 2) of IGBT element Q2A rises and becomes equal to voltage VH by the current of reactor L1A. At that time, the switching loss of the IGBT element Q1A is eliminated by turning on the IGBT element Q1A. Thereafter, IGBT element Q1A is turned off with current i of reactor L1A leftward. By performing such an operation, the switching loss in the resonant voltage converter is eliminated, and a highly efficient DC-DC converter can be realized.

  Voltage converter 12A performs a boost operation from voltage VL to voltage VH when power is supplied from battery BAT to motor generator MG2 such as during acceleration. On the other hand, voltage converter 12A performs a step-down operation from voltage VH to voltage VL during regeneration of a brake or the like.

  In the hybrid vehicle, traveling is performed on the basis of the torque of engine 4 and the torque by which motor generator MG2 is driven by the electric power generated by motor generator MG1 using the torque of engine 4 during steady traveling. Not much power is supplied to motor generator MG2. Further, during the steady running, the regenerative operation is not performed so much, so that power transfer between the battery BAT and the voltage converter 12 is almost zero.

  The proportion of steady running is large in the usage situation of the vehicle, and an increase in power consumption at this time leads to a deterioration in fuel consumption. In the present embodiment, it is possible to reduce the loss in the voltage converter when such a passing current is a small current.

FIG. 3 is a waveform diagram showing a comparison between the reactor current in the resonance operation and the current discontinuous operation.
2 and 3, the current waveform i (2) of reactor L1A in the case where a conventionally known resonance operation is performed in a state in which switch SW1 is short-circuited, and current non- The reactor current i (1) when the continuous operation is performed is shown. The direction of the reactor current i is positive in the direction of the arrow in FIG.

  First, the operation in the resonance mode in which current continuously flows will be described. The boosting operation will be described with reference to FIGS. As shown in the waveform of current i (2) and continuous current mode, IGBT element Q2A is turned on at times t1 to t4, and the current of reactor L1A increases. When current i (2) increases to set value IH in FIG. 3, IGBT element Q2A is turned off at time t4. Potential VM rises from approximately 0 V to voltage VH by current IH flowing through reactor L1A. At that time, the change rate of the voltage VM is slowed by the capacitor C1A. By turning off the IGBT element Q2A before the voltage VM rises, zero volt switching (ZVS) is realized, and switching loss can be reduced.

  When voltage VM rises to voltage VH, diode D1A is turned on and starts to pass current through positive electrode bus PL2. In FIG. 3, IGBT element Q1A is turned on at time t4. Actually, IGBT element Q1A is turned on after a dead time for preventing IGBT element Q2A and IGBT element Q1A from being turned on simultaneously. Until then, the voltage VM needs to be kept equal to the voltage VH, and it is necessary to set the current IH sufficiently large so that the current of the reactor L1A does not become zero during the dead time. At that time, the IGBT element Q1A is turned on in a state where no voltage is applied, so that zero volt switching (ZVS) is realized, and no switching element is generated in the IGBT element Q1A.

  Thereafter, reactor current i (2) decreases from time t4 to time t5, and IGBT element Q1A is turned off when it falls to negative set value IL at time t5. Thereafter, the IGBT element Q1A can be switched without causing a switching loss, similarly to the case where the IGBT element Q2A is turned off. In order to maintain the voltage VM during the dead time, the set value IL needs to be set to a sufficiently large negative current value.

  In resonance mode, average current Im of reactor L1A is substantially equal to the average value of set value IH and set value IL (strictly speaking, set values IH and IL are detected to turn off IGBT elements Q1A and Q2A. Even if controlled, the current of reactor L1A swings slightly larger due to resonance).

  In order to maintain the resonance in order to perform such an operation, even if the average current Im of the reactor L1A is 0, that is, even if the power transfer with the battery is 0, a current flows inside the voltage converter, and an IGBT element, a reactor, etc. Conduction loss occurs.

  Next, the operation when the current is discontinuous will be described. The boosting operation will be described with reference to the current i (1) and the waveform of the current discontinuous mode in FIGS. In this case, the switch SW1 is set to an off state.

  First, IGBT element Q2A is turned on at time t1, and current i (1) of reactor L1A increases. IGBT element Q2A is turned off at time t2 when reactor current i (1) increases to set value IP. Voltage VM rises to voltage VH due to current i (1) flowing through reactor L1A. In the operation when the current is discontinuous, since the switch SW1 is turned off, hard switching is performed unlike soft switching during resonance. Therefore, the switching loss occurs in the IGBT element Q2A because the element is turned off in a state where a voltage is applied to the element. When voltage VM reaches voltage VH, diode D1A is turned on, and starts to flow current through positive electrode bus PL2.

  Thereafter, current i (1) flowing through reactor L1A decreases at times t2 to t3. When the current i (1) becomes 0 at time t3, the voltage VM naturally decreases and substantially coincides with the voltage VL.

  IGBT element Q2A is periodically turned on in a period from time t1 to time t5. When IGBT element Q2A is turned on at times t1, t5, and t9, current i (1) of reactor L1A is 0, so that no switching loss occurs. Zero current switching (ZCS) has been realized. In FIG. 3, the IGBT element Q1A is turned on and off also during the current discontinuous operation. However, since a current flows through the diode D1A, it is not necessary in operation. When MOS is used for the switching element, loss is reduced due to synchronous rectification.

  The relationship between the average current Im of the reactor L1A and the set value IP is expressed by the following equations (1) and (2). As the set value IP is increased, there is no period in which the current of the reactor L1A becomes 0 as shown at times t3 to t5, and the current discontinuous operation cannot be maintained, so this operation passes through the converter. It is limited to the operation where the current is a small current.

  In equations (1) and (2), Im represents the average current of reactor L1A, f represents the frequency at which IGBT element Q1A or Q2A is turned on, and L represents the inductance of reactor L1A. Im takes a positive value during a boost operation and takes a negative value during a step-down operation.

  Further, the average current Im can be controlled not by the set value IP but also by the ON time Ton of the IGBT element Q1A or Q2A, and the following relational expressions (3) and (4) are shown.

  Since the operation as described above is performed, when the average current Im of the reactor is substantially 0, that is, when the power exchange with the battery is substantially 0, almost no current flows through the reactor L1A, and thus the conduction loss is reduced. When IGBT element Q2A is turned off at time t2, since hard switching is performed when current flows, switching loss occurs in IGBT element Q2A, but the total loss is greatly reduced in a region where the reactor current is small.

  FIG. 4 is a diagram showing converter loss when hard switching is performed and the converter is controlled in the current discontinuous mode and when the converter is controlled in the resonance mode.

  As shown in FIG. 4, when the current is smaller than the threshold value Ith1, the converter loss W (2) in the resonance mode is the converter loss W (when the hard switching operation is performed in the current discontinuous mode. Loss is larger than 1). For example, when the current is close to 0, the converter loss W (2) is 76 W. By operating this in the hard switching mode, the converter loss W (1) = 19 W, and the loss is reduced by 57 W.

  In FIG. 2, the switch SW1 is provided. However, the switch SW1 may be eliminated, and the capacitor C1A may always be used in parallel with the IGBT element Q2A. This is equivalent to controlling the switch SW1 to be on. In this case, the capacitor C1A is always connected, and the power for charging / discharging the capacitor C1A is added to the converter loss. For example, when the boosting operation is performed at VL = 200V and VH = 650V, when the IGBT element Q2A becomes conductive, the charge accumulated in the capacitor C1A for the voltage VL is discharged.

  This loss P is expressed by the following equation (5) assuming that the drive frequency F = 10 kHz and the capacitor capacitance C1A = 22 nF.

  Further, under the same conditions, the loss can be calculated as shown in the following equation (6) during the step-down operation.

  That is, the fuel consumption cannot be improved by 4.4 W during the boost operation and 22.3 W during the step-down operation. However, compared with the loss reduction 57W that is improved by providing the switch SW1 and disconnecting the capacitor C1A and performing hard switching operation, the loss increase of 22.3W by not separating the capacitor C1A calculated above is If the increase in cost and space is negligible, the switch SW1 may be omitted and only the conduction timing of the IGBT elements Q1A and Q2A shown in FIG. 3 may be changed.

  In the current discontinuous operation, when the set value IP increases, the period in which the current of the reactor L1A is 0 disappears and the current becomes continuous, and thus there is an upper limit expressed by the following formula (7). Actually, the operation mode should be switched with a smaller current value in consideration of the error.

  As described above, the current discontinuous operation is performed at a small current, and the resonance operation is performed at other times, thereby improving the efficiency at a low current and improving the fuel consumption (this is This corresponds to the determination item in step S1 of FIG. 6 described later).

Subsequently, a problem when the current passing through the converter is a large current will be described.
As a problem peculiar to the hybrid vehicle, there is a problem that the voltage VH should be stabilized even when the vehicle behaves abnormally and the elements of the inverter and the converter should not be destroyed. For example, when the tire is repeatedly locked and rotated (when slipping and gripping are repeated) depending on the road surface condition during braking with the brake, the inverter suddenly releases and consumes electric power. In such a case, an abnormally large current (about twice the rating) flows through the converter for a short time. In the voltage converter shown in FIG. 2, when the resonance operation is performed, in order to completely pass this current, it is necessary to further flow the double peak current to the IGBT element and the reactor (see FIG. 13). For this reason, an IGBT element and a reactor become enormous and a voltage converter and a vehicle will increase in cost.

  From the viewpoint of vehicle mounting space and cost, it is desirable that the IGBT element, the diode element, and the reactor are small.

  FIG. 5 is a diagram comparing the current i (3) when the resonance operation is performed and the current i (4) when the hard switching operation is performed when a large current flows.

  As shown in FIG. 5, when the average current Im flows in the resonance operation and the hard switching operation on average, the peak currents of the reactor L1A are compared with each other, and the current i (3) when operated as a resonance converter is compared. The peak of the reactor current i (4) when the hard switching operation is performed compared to the peak is about one half. However, if a hard switching operation is performed, the switching loss increases significantly, heat is generated in the IGBT element, and the power loss increases.

  However, in the case of a hybrid vehicle, as described above, a large current flows for a short time (about 10 ms) at the time of abnormality, and the influence is small in terms of heat and fuel consumption. Therefore, the peak current of the current i flowing through the reactor L1A can be reduced to about one-half by switching to the hard switching operation at a high current by increasing the switching frequency, and the IGBT element and the reactor can be downsized. It becomes. This miniaturization is about a quarter in volume.

In the control flow of FIG. 6 shown later, the determination in step S2 is this determination item.
When hard switching is performed at a large current, the loss can be reduced by controlling the switch SW1 to the off state and disconnecting the capacitor C1A. However, since it is a short time, only the switching cycle of the switching element may be changed while the switch SW1 is kept on to change from the resonance operation to the hard switching operation.

  As another effect, the voltage converter 12 can consume such abnormal excess power and prevent the voltage VH and the voltage VL from rising. The surplus power is regenerated in the battery BAT, but the receiving capacity Win has a limit (for example, 20 kW). In such a case, if the voltage converter 12 is operated by hard switching and a part of the surplus power is lost, surplus power on the inverter side can be received on the converter side by about 5 kW.

  FIG. 6 is a flowchart for illustrating control of the voltage converter in the first embodiment. The processing of this flowchart is called from a predetermined main routine and executed every predetermined time or every time a predetermined condition is satisfied.

  Referring to FIG. 6, first, in step S1, it is determined whether or not the current target value calculated from the measured value of the average current of reactor L1A or the torque command for the motor is a small current. This determination is made based on the threshold value Ith1, which is a boundary where the converter loss shown in FIG. Note that this threshold may be set slightly smaller or larger in consideration of errors.

  When it is determined in step S1 that the average value or the target value of the reactor current is a small current, the process proceeds to step S10, and the voltage converter is operated in the hard switching operation mode. At this time, the reactor current becomes a discontinuous current as shown by current i (1) in FIG. Preferably, the switch SW1 is controlled to be in an off state.

  On the other hand, if it is determined in step S1 that the current is not a small current, the process proceeds to step S2.

  In step S2, it is determined whether or not the average value or the target value of the reactor current is a large current. The threshold value IthX for determination in step S2 is larger than the threshold value Ith1 in step S1, and is a value determined by the rated current determined by the size of the component.

  If it is determined in step S2 that the current is not a large current, the process proceeds to step S3. If it is determined that the current is a large current, the process proceeds to step S4.

  In step S3, the set values IH and IL described in FIG. 3 are calculated by the first method. On the other hand, in step S4, set values IH and IL are calculated by the second method. The calculation method will be described in detail in the multiphase converter introduced in the second embodiment. If the number of phases n of the multiphase converter is set to 1, the set values IH and IL in the first embodiment can be obtained.

  Subsequently, in step S5, it is determined whether or not the frequency f becomes 10 kHz or less when the voltage converter 12 is operated with the set values IH and IL in step S3. This 10 kHz may not be exactly 10 kHz as long as it is higher than the upper limit of the human audible frequency range.

  A similar determination is also made in step S6. In step S6, it is determined whether or not the frequency f when the voltage converter 12 is operated is 10 kHz or less based on the set values IH and IL calculated in step S4.

  If it is determined in step S5 or step S6 that the operating frequency f is 10 kHz or less, there is a concern that noise may be generated during the operation of the converter. Therefore, the process proceeds to step S9 and the voltage converter is operated in the hard switching mode. The operating frequency is set to a frequency (for example, f = 10 kHz) higher than the upper limit of the human audible area. Preferably, at this time, the switch SW1 is controlled to be turned off.

  In order to prevent electromagnetic noise such as a reactor, it is effective to keep the switching frequency higher than the audible frequency (about 20 Hz to 10 kHz).

  When the frequency f calculated by the following equation (8) in step S5 and step S6 in FIG. 6 is equal to or lower than a determination value (here, 10 kHz which is the upper limit value of the audible frequency), a frequency fixed hardware is given priority to noise prevention. Perform switching operation.

  If the frequency f obtained by the equation (8) is equal to or less than the determination value, the set values IH and IL are obtained by the following equations (9), (10), and (11), and reset to approximately 10 kHz. Can be operated at frequency.

Here, Ihys indicates a hysteresis width related to the amplitude of the current of the reactor.
If it is determined in step S5 that the frequency f is not less than 10 kHz, no noise problem occurs, and the process proceeds to step S7. In step S7, the switch SW1 is controlled to be in the on state, and the voltage converter 12 is operated in the resonance mode in which the amplitude of the reactor current is increased until the current is generated in the current inversion region, thereby reducing the switching loss.

  If it is determined in step S6 that the frequency f is not less than 10 kHz, the process proceeds to step S8. When the process proceeds to step S8, the abnormal large current described with reference to FIG. 5 is generated for a very short time. In this case, the switching frequency is changed to operate the voltage converter in the hard switching mode, and the reactor current is allowed to flow as indicated by i (4) in FIG. 5 to reduce the current peak value. The switch SW1 is preferably turned off, but may be left on for a short time.

  If the operation mode of voltage converter 12 is determined in any of steps S7 to S10, the process proceeds to step S11, and control is transferred to the main routine.

[Embodiment 2]
In order to reduce the ripple currents of the voltages VL and VH, a multi-phase converter is known in which a plurality of voltage converters are operated in parallel by shifting the phase.

FIG. 7 is a diagram showing a configuration of a vehicle 200 equipped with a multiphase converter.
Referring to FIG. 7, vehicle 200 includes a voltage converter 212 instead of voltage converter 12 in the configuration of vehicle 100 described in FIG. 1. Voltage converter 212 includes voltage converters 12A and 12B connected in parallel between battery BAT and inverter unit 23 that is a load.

  Since the configuration of voltage converter 12A is similar to that of FIG. 1, description thereof will not be repeated. Voltage converter 12B is parallel to reactor L1B having one end connected to positive electrode bus PL1, IGBT elements Q1B and Q2B connected in series between positive electrode bus PL2 and negative electrode bus SL, and IGBT elements Q1B and Q2B, respectively. And diodes D1B and D2B connected to, and a capacitor C1B connected between a connection node of IGBT elements Q1B and Q2B and negative electrode bus SL.

  Reactor L1B has the other end connected to the emitter of IGBT element Q1B and the collector of IGBT element Q2B. The cathode of diode D1B is connected to the collector of IGBT element Q1B, and the anode of diode D1B is connected to the emitter of IGBT element Q1B. The cathode of diode D2B is connected to the collector of IGBT element Q2B, and the anode of diode D2B is connected to the emitter of IGBT element Q2B.

  Current ILA flowing through reactor L1A is detected by current sensor 11A, and current ILB flowing through reactor L1B is detected by current sensor 11B.

  Control device 230 receives torque command values TR1 and TR2, motor rotation speeds MRN1 and MRN2, voltages VL and VH, currents ILA and ILB, motor current values MCRT1 and MCRT2, and a start instruction IGON. Then, control device 230 outputs drive signal PWCA to voltage converter 12A, and outputs drive signal PWCB to voltage converter 12B.

FIG. 8 is a circuit diagram showing the voltage converter 212 extracted from FIG.
Referring to FIG. 8, in voltage converter 212, voltage converters 12A and 12B are connected in parallel between positive electrode bus PL1 and positive electrode bus PL2.

  Voltage converter 12A includes a reactor L1A having one end connected to positive electrode bus PL1, IGBT element Q2A and diode D2A connected in parallel between the other end of reactor L1A and the ground node, and the other end of reactor L1A and the ground A capacitor C1A and a switch SW1 connected in series with the node are included.

  Voltage converter 12A further includes an IGBT element Q1A connected in parallel between the other end of reactor L1A and positive electrode bus PL2, and a diode D1A.

  Voltage converter 12B includes a reactor L1B having one end connected to positive electrode bus PL1, IGBT element Q2B and diode D2B connected in parallel between the other end of reactor L1B and a ground node, and the other end of reactor L1B and a ground node And a capacitor C1B connected between the two. Since voltage converter 12B is not operated when the current is small, switch SW1 is not provided like voltage converter 12A. Voltage converter 12B further includes an IGBT element Q1B and a diode D1B connected in parallel between the other end of reactor L1B and positive electrode bus PL2.

  FIG. 9 is a diagram showing a change in converter loss when the operation mode of multiphase voltage converter 212 shown in FIG. 8 is changed.

  Referring to FIGS. 8 and 9, waveform W (1) indicates that voltage converter 12B is stopped in voltage converter 212, and voltage converter 12A turns off switch SW1 to perform a hard switching operation and operate in a current discontinuous mode. Shows the converter loss. Waveform W (2) represents converter loss when voltage converter 12B is stopped in voltage converter 212 and voltage converter 12A controls switch SW1 to the on state to perform a resonance operation.

  Waveform W (3) represents converter loss when voltage converters 12A and 12B are operated in multiphase in voltage converter 212, and switch SW1 is controlled to be in an on state to perform a resonant operation.

  In the region where the current is larger than the current value Ith3, the loss is smaller in the multiphase operation of the waveform W (3).

  On the other hand, in the region where the current is smaller than the current value Ith1, the waveform W (1) of the current discontinuous operation in the single phase operation has the least converter loss. In the region of current values Ith1 to Ith3, the converter loss of waveform W (2) is the smallest.

  Therefore, the multi-phase converter is preferably operated in the current discontinuous mode by switching to the single phase operation when the current is small. Most preferably, when the current value is smaller than Ith1, single phase operation of hard switching is executed, and when the current value is Ith1 to Ith3, single phase and resonance mode operation is performed, and the current value is larger than Ith3. In this case, the resonance loss of the multi-phase operation is performed, and the converter loss may be the lowest. Since the control becomes complicated, for example, hard switching and single phase operation may be performed when the current value is Ith2 or less, and multiphase and resonance mode operation may be performed when the current value is Ith2 or more.

  Further, if the converter to be stopped when the current is small is determined to be the voltage converter 12B, the voltage converter 12B operates only in the resonance mode, so that a switch inserted in series with the capacitor C1B is unnecessary.

  FIG. 10 is a flowchart for illustrating control executed by control device 230 in the multiphase converter. The processing of this flowchart is called from a predetermined main routine and executed every predetermined time or every time a predetermined condition is satisfied.

  Referring to FIG. 10, first in step S21, it is determined whether or not the current target value calculated from the measured value of the average current of converter 12 or the torque command for the motor is a small current. This determination is made based on the threshold value Ith2, which is a boundary where the converter loss shown in FIG. 9 is a hard switching operation and a discontinuous current flows and the current loss is lower than that in the multiphase resonance operation. Note that this threshold may be set slightly smaller or larger in consideration of errors.

  If it is determined in step S21 that the average value or the target value of the reactor current is a small current, the process proceeds to step S30, and the voltage converter 212 is operated in the single phase and hard switching operation mode. At this time, the reactor current becomes a discontinuous current as shown by current i (1) in FIG. Preferably, the switch SW1 is controlled to be in an off state.

  In the current discontinuous operation executed in step S30, a multiple of the number of multiphases of the determination value of the operating frequency f (10 kHz in this case) (twice 20 kHz for 2-layer multiphase and 3 times for 3-layer multiphase). 30 kHz). This is to make the minimum frequency of ripples equal to that in multiphase.

Note that the following effects can be obtained by determining the lower limit value of the operating frequency.
In general, a smoothing capacitor is provided before and after the converter. The inductance of the capacitor and the wire harness has a resonance point. When a ripple current close to the resonance frequency flows, a large current and voltage oscillation occur, and the voltage converter generates heat and breaks down. By keeping the operating frequency of the voltage converter above the minimum frequency, the ripple frequency can always be higher than the resonance point to prevent the converter from being destroyed.

  On the other hand, if it is determined in step S21 that the current is not a small current, the process proceeds to step S22.

  In step S22, it is determined whether or not the average value or the target value of the reactor current is a large current. The threshold value IthX for determination in step S22 is larger than the threshold value Ith2 in step S21 and is a value determined by the rated current determined by the size of the component.

  If it is determined in step S22 that the current is not a large current, the process proceeds to step S23, and if it is determined that the current is a large current, the process proceeds to step S24.

  In step S23, the set values IH and IL described in FIG. 3 are calculated by the first method. On the other hand, in step S24, set values IH and IL are calculated by the second method.

  FIG. 11 is a diagram showing how the calculated values of the set values IH and IL calculated in step S23 of FIG. 10 change as the average current Im / n changes.

  Referring to FIGS. 10 and 11, in step S23, Ip and In are obtained according to the following equations.

Ip = (2 × Im) / n−Irn
In = (2 * Im) / n-Irp
Note that n indicates the number of multiphases, and Irn and Irp indicate reverse currents for resonance. Irn and Irp are determined by the voltage VH, the voltage VL, and the dead time. In order to hold the voltage during the dead time, Irn is proportional to VH, and Irp is proportional to (VH−VL). Irn and Irp are not necessarily the same value. The set value IH is set to the larger of Irp and Ip. The set value IL is set to the smaller of Irn and In.

  FIG. 12 is a diagram showing how the calculated values of the set values IH and IL calculated in step S24 of FIG. 10 change as the average current Im / n changes.

  Referring to FIGS. 10 and 12, in step S24, set values IH and IL are calculated by the following equations.

IH = (Im + Iex) / n-Is
IL = (Im-Iex) / n + Is
Note that Iex indicates a determination value of a large current in step S22, and Is indicates a guard value that prevents the reactor current from being reversed.

  Subsequently, in step S25, it is determined whether or not the frequency f becomes 10 kHz or less when the voltage converter 212 is operated with the set values IH and IL in step S23. This 10 kHz may not be exactly 10 kHz as long as it is higher than the upper limit of the human audible frequency range.

  A similar determination is also made in step S26. In step S26, it is determined whether or not the frequency f when the voltage converter 212 is operated is 10 kHz or less based on the set values IH and IL calculated in step S24.

  If it is determined in step S25 or step S26 that the operating frequency f is 10 kHz or less, there is a concern that noise may occur during the operation of the converter 212. Therefore, the process proceeds to step S28 and the voltage converter is set to the multi-phase hard switching mode. And the operating frequency is set to a frequency (for example, f = 10 kHz) higher than the lower limit of the human audible range. Preferably, at this time, the switch SW1 is controlled to be turned off.

  In order to prevent electromagnetic noise such as a reactor, it is effective to keep the switching frequency higher than the audible frequency (about 20 Hz to 10 kHz).

  When the frequency f calculated by the above-described equation (8) in step S25 and step S26 in FIG. 10 is equal to or lower than the determination value (here, 10 kHz which is the upper limit value of the audible frequency), the frequency-fixed hardware is given priority to noise prevention Perform switching operation.

  If the frequency f obtained by the equation (8) is equal to or less than the determination value, the setting values IH and IL are obtained by the following equations (12) and (13) and reset to operate at a frequency of approximately 10 kHz. be able to.

  Here, Ihys indicates a hysteresis width related to the amplitude of the current of the reactor, and is obtained by the above-described equation (9).

  If it is determined in step S25 that the frequency f is not less than 10 kHz, no noise problem occurs, and the process proceeds to step S27. In step S27, the switch SW1 is controlled to be in an ON state, and the switching loss is reduced by operating the voltage converter 212 in the resonance mode and the multiphase in which the amplitude of the reactor current is increased until the current inversion region is generated.

  If it is determined in step S26 that the frequency f is not less than 10 kHz, the process proceeds to step S29. When the process proceeds to step S29, the abnormal large current described with reference to FIG. 5 is generated for a very short time. In this case, the voltage converter is operated in the hard switching mode by changing the multiphase and switching frequency, and the reactor current is caused to flow as shown in i (4) of FIG. 5 to reduce the peak value of the current. The switch SW1 is preferably turned off, but may be left on for a short time.

  If the operation mode of voltage converter 212 is determined in any of steps S27 to S30, the process proceeds to step S31 and the control is moved to the main routine.

  Thus, according to the embodiment of the present invention, it is possible to configure a hybrid vehicle converter that is small in size and efficient in a small current region.

  Finally, this embodiment will be summarized with reference to FIG. 1 again. The voltage converter of the present embodiment is a voltage converter 12 that is connected between a DC power supply (battery BAT) and a load (inverter unit 23) and that can operate by switching between a resonance mode and a hard switching mode. 1 converter 12A is provided. First converter 12A includes a reactor L1A and a first switching element (IGBT element Q2A) connected to the reactor L1A. Voltage converter 12 further includes a control unit (control device 30) that performs on / off control of the first switching element (IGBT element Q2A). The control unit (the control device 30) selects either the resonance mode or the hard switching mode according to the current value passing through the voltage converter 12 or the target value of the current value so as to realize the selected mode. The first switching element (IGBT element Q2A) is controlled.

  Preferably, first converter 12A further includes a capacitor C1A connected in parallel with the first switching element (IGBT element Q2A) at least in the resonance mode.

  More preferably, the first converter 12A further includes a switch SW1 provided on a path connecting the capacitor C1A in parallel with the first switching element (IGBT element Q2A). The control unit (control device 30) controls the switch SW1 to be conductive in the resonance mode, and controls the switch SW1 to be non-conductive in the hard switching mode.

  Preferably, one end of reactor L1A is connected to the positive electrode of a DC power supply (battery BAT). The first switching element (IGBT element Q2A) is connected between the other end of the reactor and the negative electrode of the DC power supply (battery BAT). First converter 12A further includes a second switching element (IGBT element Q1A) connected between the other end of reactor L1A and the load (inverter unit 23).

  Preferably, as shown in FIG. 6, when the control unit (control device 30) is operated in the hard switching mode, the period during which no current flows through reactor L1A is determined to be smaller than the upper limit value of the current value that periodically occurs. When the current value or target value is smaller than the first threshold value Ith1 (YES in step S1), the hard switching mode is selected (step S10), and the current value or target value is set. Is greater than the first threshold value Ith1 (NO in step S1), the operation mode is switched so as to select the resonance mode (step S7). In this case, the determinations in steps S2, S5, and S6 in FIG. 6 are not necessarily performed. If there is a small current in step S1, the resonance mode in step S7 may be selected immediately.

  More preferably, as shown in FIG. 6, the control unit (control device 30) sets the current value or the target value to the second value with the second threshold value IthX larger than the first threshold value Ith1 as the boundary value. If it is smaller than the threshold value IthX (NO in step S2), the resonance mode is selected (step S7). If the current value or the target value is larger than the second threshold value IthX (YES in step S2). The operation mode is switched so as to select the hard switching mode (step S8). In this case, the determinations in steps S5 and S6 in FIG. 6 are not necessarily performed. If there is a large current in step S2, the hard switching mode in step S8 is immediately selected, and the large current is not detected in step S2. May immediately select the resonance mode of step S7.

  Preferably, only the determination of step S2 may be performed without the determination of steps S1, S5, and S6 in FIG. 6, and in this case, the control unit (control device 30) sets a predetermined threshold value IthX as a boundary. If the current value or the target value is smaller than the predetermined threshold value IthX, the resonance mode is selected in step S7. If the current value or the target value is larger than the predetermined threshold value IthX, the hardware is selected in step S8. The operation mode is switched so as to select the switching mode.

  Preferably, as shown in FIG. 7, voltage converter 212 further includes a second converter 12B provided between DC power supply (battery BAT) and a load (inverter unit 23) in parallel with first converter 12A. As shown in FIG. 10, the control unit (control device 30) operates in a single mode and a first mode in which one of the first and second converters 12A and 12B is operated and the other is stopped according to the current value or the target value. One of the multimodes in which both the first and second converters 12A and 12B are operated is selected. Then, for example, as shown in steps S27 to S30 in FIG. 10, the control unit (control device 30) is based on a combination of either the selected single mode or multimode and the selected resonance mode or hard switching mode. To control the first and second converters 12A and 12B.

  Preferably, the control unit (control device 30) selects one of the resonance mode and the hard switching mode according to the current value passing through the voltage converter 12 or the target value of the current value, and realizes the selected mode. (Steps S1, S2; S21, S22) and the first switching element so that the switching frequency of the first switching element becomes higher than a predetermined frequency (for example, an audible frequency upper limit) (steps S5, S6; S25, S26). The element (IGBT element Q2A) is controlled.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows the main structures of the vehicle 100 carrying the voltage converter of Embodiment 1 of this invention. It is the figure which extracted and showed the voltage converter 12A in FIG. It is the wave form diagram which compared and showed the reactor current of a resonance operation and a current discontinuous operation. It is the figure which showed the converter loss at the time of performing hard switching and controlling the converter in the current discontinuous mode and controlling in the resonance mode. It is the figure which compared and showed the electric current i (4) at the time of making a hard switching operation | movement and the electric current i (3) at the time of performing a resonant operation when a large current flows. 3 is a flowchart for illustrating control of the voltage converter in the first embodiment. It is the figure which showed the structure of the vehicle 200 carrying a multiphase converter. It is the circuit diagram which extracted and showed the voltage converter 212 in FIG. It is a figure which shows the change of converter loss at the time of changing the operation mode of the voltage converter 212 of the multi phase shown in FIG. It is a flowchart for demonstrating the control performed by the control apparatus 230 in a multiphase converter. FIG. 11 is a diagram showing how calculated values of set values IH and IL calculated in step S <b> 23 in FIG. 10 change according to a change in average current Im / n. It is the figure which showed how the calculated value of setting value IH and IL calculated in step S24 of FIG. 10 changes according to the average current Im / n changing. It is the figure which compared and showed the electric current which flows into the reactor of a resonance type converter and a non-resonance type converter.

Explanation of symbols

  2 wheel, 3 power split mechanism, 4 engine, 10, 13 voltage sensor, 11, 24, 25 current sensor, 12, 12A, 12B, 212 converter, 14, 22 inverter, 15 U phase arm, 16 V phase arm, 17 W-phase arm, 23 inverter unit, 30, 230 control device, 100, 200 vehicle, BAT battery, C1A, C1B capacitor, C2 smoothing capacitor, D1A, D1B, D2A, D2B, D3-D8 diode, L1A, L1B reactor, MG1, MG2 motor generator, PL1, PL2 positive bus, Q1A, Q1B, Q2A, Q2B, Q3-Q8 IGBT element, SL negative bus, SW1 switch.

Claims (10)

A voltage converter that is connected between a DC power source and a load and that can operate by switching between a resonance mode and a hard switching mode,
A first converter, the first converter comprising:
Reactor,
A first switching element connected to the reactor,
The voltage converter is
A control unit that performs on / off control of the first switching element;
The control unit selects either the resonance mode or the hard switching mode according to a current value passing through the voltage converter or a target value of the current value so as to realize the selected mode. A voltage converter for controlling the first switching element. The first converter includes:
The voltage converter according to claim 1, further comprising a capacitor connected in parallel with the first switching element in at least the resonance mode. The first converter includes:
A switch provided on a path connecting the capacitor in parallel with the first switching element;
The voltage converter according to claim 2, wherein the control unit controls the switch to a conductive state in the resonance mode, and controls the switch to a non-conductive state in the hard switching mode. One end of the reactor is connected to the positive electrode of the DC power source,
The first switching element is connected between the other end of the reactor and a negative electrode of the DC power source,
The first converter includes:
The voltage converter according to claim 1, further comprising a second switching element connected between the other end of the reactor and the load.   When the control unit is operated in the hard switching mode, the current value is set with a first threshold value that is set to be smaller than the upper limit value of the current value that periodically causes a period in which no current flows in the reactor. Alternatively, the hard switching mode is selected when the target value is smaller than the first threshold value, and the resonance mode is selected when the current value or the target value is larger than the first threshold value. The voltage converter according to any one of claims 1 to 4, wherein the operation mode is switched as described above.   The control unit uses the second threshold value that is larger than the first threshold value as a boundary value, and sets the resonance mode when the current value or the target value is smaller than the second threshold value. The voltage converter according to claim 5, wherein the operation mode is switched so that the hard switching mode is selected when the current value or the target value is greater than the second threshold value.   The control unit selects a resonance mode when the current value or the target value is smaller than the predetermined threshold with a predetermined threshold as a boundary value, and the current value or the target value is The voltage converter according to any one of claims 1 to 4, wherein the operation mode is switched so that the hard switching mode is selected when the threshold value is larger than a predetermined threshold value. The voltage converter is
A second converter provided between the DC power source and the load in parallel with the first converter;
The control unit operates both the single mode and the first and second converters that operate one of the first and second converters and pause the other according to the current value or the target value. Selecting one of the multimodes to be controlled, and controlling the first and second converters based on a combination of the selected single mode, the multimode, and any of the selected resonance mode and hard switching mode. Item 8. The voltage converter according to any one of Items 1 to 7.   The control unit selects one of the resonance mode and the hard switching mode according to a current value passing through the voltage converter or a target value of the current value, and realizes the selected mode, and The voltage converter according to claim 1, wherein the first switching element is controlled so that a switching frequency of the first switching element is higher than a predetermined frequency.   A vehicle equipped with the voltage converter according to claim 1.

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