JP2010124586A - Dc-dc converter unit and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an increase in temperature of a switching element without suppressing passing power of a DC-DC converter. <P>SOLUTION: Driving is switched from driving (operation) only by a one-phase arm UA to a phase arm alternating driving (operation), depending on an increase in temperatures of switching elements 81u, 82u; 81v, 82v; and 81w, 82w. Thus, the increase in temperature of the switching elements 81u, 82u; 81v, 82v; and 81w, 82w can be suppressed without suppressing the passing power of the DC-DC converter 20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a DC / DC converter device in which a plurality of phase arms having a switching element and performing voltage conversion are connected in parallel between a primary side and a secondary side, and a control method thereof.

  In the DC / DC converter device that converts the DC voltage of the DC power source connected to the primary side to correspond to the rated voltage of the load connected to the secondary side, when the load becomes heavy, the DC power source on the primary side The current passing through the switching element to the secondary side increases.

  As the current increases, the switching element generates more heat. The switching element may be destroyed if it overheats.

  A technique for preventing destruction of the switching element due to heat has been proposed (Patent Document 1).

  The technique according to Patent Document 1 is configured to restrict (suppress) the current passing through the switching element constituting the DC / DC converter device when the temperature of the switching element rises to a predetermined temperature.

JP-A-5-284737

  However, if the passing current of the switching element is reduced, the power requirement of the load cannot be satisfied, and the work performed by the load may fall short of power.

  The present invention has been made in consideration of such problems, and a DC / DC converter device capable of suppressing a temperature rise of a switching element without suppressing power passing through the DC / DC converter device, and An object is to provide a control method thereof.

  A DC / DC converter device according to the present invention is a DC / DC converter device in which a plurality of phase arms having a switching element and performing voltage conversion are connected in parallel between a primary side and a secondary side. A temperature sensor that detects an element temperature of the switching element; and a control unit that switches control from driving of only one phase arm to alternating driving of a plurality of phase arms as the detected element temperature increases. It is characterized by.

  The DC / DC converter apparatus control method according to the present invention is a DC / DC in which a plurality of phase arms having a switching element and performing voltage conversion are connected in parallel between a primary side and a secondary side. A method for controlling a converter device, comprising: detecting an element temperature of the switching element; and switching the control from driving only one phase arm to alternating driving of a plurality of phase arms as the detected element temperature increases. Features.

  According to each invention described above, the passing power of the DC / DC converter is suppressed by switching from the driving (operation) of only the one-phase arm to the phase arm replacement driving (operation) according to the temperature rise of the switching element. Therefore, the temperature rise of the switching element can be suppressed.

  In this case, as the detected element temperature increases, the control unit changes from driving (operation) of only the one-phase arm to replacement driving (operation) of the two-phase arm, and further to replacement driving (operation) of the three-phase arm. By switching the control, the control switching order when the plurality of arms are three-phase arms is clarified.

  It should be noted that by providing hysteresis to the temperature threshold when switching control, switching chattering due to temperature fluctuation at the time of control switching can be prevented, and switching control can be stabilized.

  Further, the one-phase arm that is driven when the element temperature is not raised is a fixed phase arm, and the power rating of the switching element of the fixed phase arm is higher than the power rating of the switching element of the other phase arm. Is preferably set to a large value. Thus, by setting the power rating of the switching element of the fixed one-phase arm that is driven most frequently to be larger than the power rating of the switching element of the other phase arm, the life of the DC / DC converter device (average (Failure time) can be lengthened.

  Further, each time the main switch of the DC / DC converter device is turned on, the one-phase arm that is driven when the element temperature is not increased is switched to another one-phase arm for driving. Also good. In this way, by switching the phase arm that is driven by only one phase arm each time the main switch (power switch) is turned on, the life (average failure time) of the DC / DC converter device is increased. Can do.

  According to the present invention, it is possible to suppress the temperature rise of the switching elements constituting the DC / DC converter device without suppressing the passing power of the DC / DC converter device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a vehicle or the like to which a DC / DC converter device that implements a method for driving a DC / DC converter device according to the present invention is applied will be described with reference to the drawings.

A. Explanation of overall configuration [Overall configuration]
FIG. 1 shows a schematic overall configuration diagram of a fuel cell vehicle 10 according to this embodiment.

  The fuel cell vehicle 10 basically includes a battery 12 as a first DC power supply device that generates a primary voltage V1 on the primary side 1S and a second DC power supply that generates a secondary voltage V2 on the secondary side 2S. A hybrid DC power supply device including a fuel cell 14 as a device, and a traveling motor 16 that is a load supplied with power from the hybrid DC power supply device.

[Fuel cell and its system]
The fuel cell 14 has, for example, a stack structure in which cells formed by sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode from both sides are stacked. A reaction gas supply unit 18 is connected to the fuel cell 14 through a pipe. The reactive gas supply unit 18 includes a hydrogen tank that stores hydrogen (fuel gas) that is one reactive gas, and a compressor that compresses air (oxidant gas) that is the other reactive gas. A power generation current generated by an electrochemical reaction in the fuel cell 14 of hydrogen and air supplied from the reaction gas supply unit 18 to the fuel cell 14 is supplied to the motor 16 and the battery 12.

  The fuel cell system 11 includes a fuel cell 14 and a reaction gas supply unit 18 and a fuel cell control unit (FC control unit) 44 that controls them.

[DC / DC converter]
The DC / DC converter 20 is connected to a battery 12 having one side connected to the primary side 1S, and the other side is connected to a secondary side 2S, which is a connection point between the fuel cell 14 and the motor 16, and a chopper type voltage conversion. Device.

  The DC / DC converter 20 converts the primary voltage V1 into a secondary voltage V2 (V1 ≦ V2) (boost conversion), and also converts the secondary voltage V2 into a primary voltage V1 (step-down conversion). This is a voltage conversion device.

[Inverter, motor and drive system]
The inverter 22 has a three-phase full-bridge configuration, performs DC / AC conversion, converts DC to three-phase AC, and supplies it to the motor 16, while DC after AC / DC conversion accompanying the regenerative operation. Is supplied from the secondary side 2S to the primary side 1S through the DC / DC converter 20, and the battery 12 is charged.

  The motor 16 rotates the wheels 26 through the transmission 24. In practice, the inverter 22 and the motor 16 are collectively referred to as a load 23.

[High voltage battery]
A high voltage battery 12 connected to the primary side 1S is a power storage device (energy storage), and for example, a lithium ion secondary battery or a capacitor can be used. In this embodiment, a lithium ion secondary battery is used.

[Various sensors, main switches and communication lines]
A main switch (power switch) 34 and various sensors 36 are connected to a communication line 38. The main switch 34 has a function as an ignition switch that turns on (starts or starts) and turns off (stops) the fuel cell vehicle 10 and the fuel cell system 11. Various sensors 36 detect state information, such as a vehicle state and an environmental state. As the communication line 38, a CAN (Controller Area Network) that is an in-vehicle LAN is used.

[Control unit]
The integrated control unit 40, the FC control unit 44, the motor control unit 46, the converter control unit 48, and the battery control unit 52 are connected to the communication line 38. A DC / DC converter device 50 is formed by the DC / DC converter 20 and the converter control unit 48 that controls the DC / DC converter 20.

  Each control unit 40, 44, 46, 48, 52 includes a microcomputer, detects state information of various switches such as the main switch 34 and various sensors 36, and also controls each of the control units 40, 44, 46, 48, 52. Each CPU implements various functions by inputting status information from these switches and sensors and information (commands, etc.) from other controllers, and executing programs stored in memory (ROM). It operates as a function realization unit (function realization means). The control units 40, 44, 46, 48, and 52 have an input / output interface such as a timer, an A / D converter, and a D / A converter, as necessary, in addition to a CPU and a memory.

B. Detailed configuration description [DC / DC converter device]
FIG. 2 shows a detailed configuration of the DC / DC converter 20. The DC / DC converter 20 includes three-phase phase arms UA, VA, WA arranged between the primary side 1S and the secondary side 2S, and a reactor 90.

  The U-phase arm UA includes an upper arm element (upper arm switching element 81u and diode 83u) and a lower arm element (lower arm switching element 82u and diode 84u).

  V-phase arm VA includes an upper arm element (upper arm switching element 81v and diode 83v) and a lower arm element (lower arm switching element 82v and diode 84v).

  W-phase arm WA includes an upper arm element (upper arm switching element 81w and diode 83w) and a lower arm element (lower arm switching element 82w and diode 84w).

  As the upper arm switching elements 81u, 81v, 81w and the lower arm switching elements 82u, 82v, 82w, for example, MOSFETs or IGBTs are employed.

  Reactor 90 is inserted between the midpoint (common connection point) of each phase arm UA, VA, WA and the positive electrode of battery 12, and is connected between primary voltage V1 and secondary voltage V2 by DC / DC converter 20. When the voltage is converted at, energy is released and stored.

  The upper arm switching elements 81u, 81v, 81w are turned on by the high level of the gate drive signals (drive voltages) UH, VH, WH output from the converter control unit 48, and the lower arm switching elements 82u, 82v, 82w are The gate driving signals (driving voltages) are turned on by the high levels of UL, VL, WL. The converter control unit 48 detects the primary voltage V1 by the voltage sensor 91 provided in parallel with the primary side smoothing capacitor 94, detects the primary current I1 by the current sensor 101, and detects the secondary side smoothing capacitor 96. The secondary voltage V2 is detected by a voltage sensor 92 provided in parallel with the current sensor 102, and the secondary current I2 is detected by a current sensor 102.

  A temperature sensor 69 is attached to each of the upper arm switching elements 81u, 81v, 81w and the lower arm switching elements 82u, 82v, 82w, and the upper arm switching elements 81u, 81v, 81w and the lower arm switching elements 82u, 82v, 82w The detected temperatures Tuh (81u), Tvh (81v), Twh (81w), Tul (82u), Tvl (82v), and Twl (82w) are detected by the converter control unit 48.

[Operation of DC / DC converter device]
(3-phase arm replacement drive operation: also called 3-phase operation)
The time chart of FIG. 3 is an explanatory diagram of the three-phase arm replacement drive operation of the DC / DC converter device 50.

  In the step-down chopper control related to the step-down operation (regeneration operation), the secondary current I2 flowing out from the load 23 and the fuel cell 14 passes through the DC / DC converter 20 and charges the battery 12 as the primary current I1. In the step-up chopper control related to the step-up operation (power running operation), the primary current I1 flowing out from the battery 12 passes through the DC / DC converter 20 and the load 23 including the motor 16 is driven as the secondary current I2.

Assuming that the switching period is 2π = T and the period during which a high-level drive signal is transmitted to the upper and lower arm switching elements 81 and 82 is Ton, the driving duty (ON duty) in the step-down chopper control is ignored if the dead time dt is ignored. ) Is expressed by equation (1), and the drive duty in boost chopper control is expressed by equation (2).
Ton / T = V1 / V2 (1)
Ton / T = (1−V1 / V2) (2)

  Among the waveforms of the drive signals UH, UL, VH, VL, WH, WL, the hatched period is an arm switching element (for example, drive signal) to which the drive signals UH, UL, VH, VL, WH, WL are supplied. The arm switching element corresponding to UH indicates a period during which the upper arm switching element 81u) is flowing (current is flowing).

  In any operation of the step-down chopper control and step-up chopper control of the DC / DC converter 20, the upper arm switching element 81 (81u to 81w) and the lower arm switching element 82 (82u) of the same phase every switching cycle 2π. To 82w), high level drive signals UH, UL, VH, VL, WH, WL are output. In addition, the drive signals UH, UL, VH, VL, WH, and WL are output by changing (rotating) the UVW phase. In the step-down chopper control, the upper arm switching element 81 (81u to 81w) is allowed to flow, and in the step-up chopper control, the lower arm switching element 82 (82u to 82w) is allowed to flow.

  In this case, in order to prevent the secondary voltage V2 from being short-circuited simultaneously between the upper and lower arm switching elements 81 and 82, each of the drive signals UH, UL, VH, VL, WH, WL has a dead time dt. It is trying to make it high level across. That is, so-called synchronous switching is performed with the dead time dt interposed therebetween.

  In the step-down chopper control, first, the secondary current I2 flows as the primary current I1 to the reactor 90 through the upper arm switching element 81u during a period in which only the upper arm switching element 81u (U phase) is passed by the drive signal UH. The energy is accumulated in the reactor 90 and the battery 12 is charged.

  Next, during a period in which only the drive signal UL is at a high level, the lower arm switching element 82u does not flow, and the diodes 84u, 84v, 84w are turned on to release the energy accumulated in the reactor 90. The battery 12 is charged. Hereinafter, similarly, the V phase and the W phase are repeated.

  In the step-up chopper control, first, energy is accumulated in the reactor 90 by the primary current I1 from the battery 12 during a period in which only the drive signal UL (U phase) is at a high level (a period indicated by hatching). At this time, a current is supplied from the secondary side smoothing capacitor 96 to the load 23.

  Next, during a period in which only the drive signal VH (V phase) is at a high level, the upper arm switching element 81v does not flow, and the diodes 83u, 83v, 83w are conducted and accumulated in the reactor 90. The energy is released, the primary current I1 from the reactor 90 passes through the DC / DC converter 20, charges the secondary-side smoothing capacitor 96 as the secondary current I2, and is supplied to the load 23. Hereinafter, the V phase and the W phase are similarly repeated.

  That is, in the three-phase arm replacement drive operation, the U-phase arm UA, the V-phase arm VA, and the W-phase arm WA are switched and switched.

(Two-phase arm replacement drive operation: also called two-phase operation.)
The time chart of FIG. 4 is an explanatory diagram of the two-phase arm replacement drive operation of the DC / DC converter device 50.

  As can be seen from FIG. 4, in the two-phase arm replacement drive operation, the U-phase arm UA and the V-phase arm VA are switched and switched. W-phase arm WA is in an off state.

(One-phase arm drive operation: Also called normal operation.)
The time chart of FIG. 5 is an explanatory diagram of the one-phase arm driving operation of the DC / DC converter device 50.

  As can be seen from FIG. 5, in the one-phase arm driving operation, only the U-phase arm UA is switched. V-phase arm VA and W-phase arm WA are in an off state.

C. Description of Operation Next, a driving method by the converter control unit 48 of the DC / DC converter device 50 in accordance with the temperature of the switching element will be described with reference to the flowchart in FIG. The description will be given with reference. These flowcharts and characteristic diagrams are stored in advance in a memory in the converter control unit 48.

  The characteristic diagram of FIG. 7 shows, as an example, how to switch the control phase arm using only the normal U-phase arm UA. When the phase arms are switched, hysteresis is given at threshold temperatures Tth1 to Tth4 (Tth1 <Tth2 <Tth3 <Tth4). The horizontal axis represents the maximum of the detected temperatures Tuh (81u), Tvh (81v), Twh (81w), Tul (82u), Tvl (82v), and Twl (82w) detected by the other six temperature sensors 69 shown in FIG. Reference is made to the value of temperature Tmax.

  When the operation of the main switch 34 (see FIG. 1) from OFF to ON is detected by the converter control unit 48 through the communication line 38, the normal operation flag F1 and the two-phase operation are performed in the pre-operation confirmation process in step S1 of FIG. It is determined whether both the flag F2 and the three-phase operation flag F3 are off (F1 = OFF, F2 = OFF, F3 = OFF).

  When the determination in step S1 is negative, it is estimated that the one-phase operation is being performed. Further, in step S2, the normal operation flag F1 = ON, the two-phase operation flag F2 = OFF, and the three-phase operation flag F3. It is determined whether or not = OFF.

  When the determinations in step S1 and step S2 are affirmative, in step S3, the first maximum temperature Tmax1 is calculated. The first maximum temperature Tmax1 is the maximum temperature (large value temperature) of the detection temperature Tuh (81u) or the detection temperature Tul (82u) of the U-phase arm UA.

  Next, in step S4, it is determined whether or not the first maximum temperature Tmax1 is equal to or lower than the threshold temperature Tth2 shown in FIG. 7, and if it is equal to or lower, the one-phase operation is confirmed. In step S5, the flag combination is determined. The normal operation flag F1 = ON, the two-phase operation flag F2 = OFF, and the three-phase operation flag F3 = OFF are set.

  If the first maximum temperature Tmax1 exceeds the threshold temperature Tth2 in step S4, the two-phase operation is confirmed, and in step S6, the combination of flags is the normal operation flag F1 = OFF, the two-phase operation flag F2 = ON and the three-phase operation flag F3 = OFF is set.

  Next, in step S7, an output pattern of a drive signal output from the converter control unit 48 to the DC / DC converter 20 is determined based on the set combination of flags, and the output pattern of the DC / DC converter 20 is determined based on the output pattern. Operation is controlled. The control process in step S7 will be described later.

  When the determination in step S2 described above is negative, it is estimated that the two-phase operation is being performed. Further, in step S8, the normal operation flag F1 = OFF, the two-phase operation flag F2 = ON, and the three-phase operation. It is determined whether or not the flag F3 = OFF.

  When the determination in step S8 is affirmative, in step S9, the second maximum temperature Tmax2 is calculated. The second maximum temperature Tmax2 is the maximum of the detection temperature Tuh (81u), the detection temperature Tul (82u), the detection temperature Tvh (81v), and the detection temperature Tvl (82v) of the switching elements of the U-phase arm UA and the V-phase arm VA. Temperature.

  Next, in step S10, it is determined whether or not the second maximum temperature Tmax2 is equal to or lower than the threshold temperature Tth4 shown in FIG. 7. If it is equal to or lower, the second maximum temperature Tmax2 is further determined to be the threshold temperature in step S11. It is determined whether or not it is equal to or less than Tth1, and if so, in step S12, the one-phase operation is confirmed, and the flag combination is the normal operation flag F1 = ON, the two-phase operation flag F2 = OFF, and 3 The phase operation flag F3 = OFF is set.

  If the second maximum temperature Tmax2 is higher than the threshold temperature Th1 in step S11, the combination of flag settings during the two-phase operation in step S8, the normal operation flag F1 = OFF, the two-phase operation flag F2 = ON, and the three-phase The operation flag F3 = OFF is confirmed.

  If the second maximum temperature Tmax2 exceeds the threshold temperature Tth4 in step S10, the three-phase operation is confirmed in step S13, and the flag combination is the normal operation flag F1 = OFF and the two-phase operation flag. F2 = OFF and the three-phase operation flag F3 = ON are set.

  Next, in step S7, an output pattern of a drive signal output from the converter control unit 48 to the DC / DC converter 20 is determined based on the set combination of flags, and the output pattern of the DC / DC converter 20 is determined based on the output pattern. Operation is controlled. The control process in step S7 will be described later.

  When the determination in step S8 described above is negative, it is estimated that the three-phase operation is being performed. Further, in step S14, the normal operation flag F1 = OFF, the two-phase operation flag F2 = OFF, and the three-phase operation. It is determined whether or not the flag F3 = ON.

  When the determination in step S14 is affirmative, a third maximum temperature Tmax3 is calculated in step S15. The third maximum temperature Tmax2 is the detection temperature Tuh (81u), detection temperature Tul (82u), detection temperature Tvh (81v), and detection of all switching elements of the U-phase arm UA, V-phase arm VA, and W-phase arm WA. The maximum temperature among the temperature Tvl (82v), the detection temperature Twh (81w), and the detection temperature Twl (82w).

  Next, in step S15, it is determined whether or not the third maximum temperature Tmax3 is equal to or lower than the threshold temperature Tth3. If it is equal to or lower, the two-phase operation is confirmed in step S16, and the combination of the flags is the normal operation flag. A combination of F1 = OFF, two-phase operation flag F2 = ON, and three-phase operation flag F3 = OFF is set.

  If the third maximum temperature Tmax3 exceeds the threshold temperature Th3 in step S15, the normal operation flag F1 = OFF, the two-phase operation flag F2 = OFF, which is a combination of flag settings during the three-phase operation in step S14, and The combination of the three-phase operation flag F3 = ON is determined.

  If the determination in step S14 is negative, the control processing in step S7 is performed without knowing the combination of flag settings.

  Next, in step S7, an output pattern of the drive signal output from the converter control unit 48 to the DC / DC converter 20 is determined based on the combination of flags set as described above, and the DC / DC is determined based on the output pattern. When the operation of the DC converter 20 is a one-phase operation, the one-phase arm driving operation of FIG. 5 is performed. When the two-phase operation is performed, the two-phase arm replacement driving operation of FIG. It is controlled to one of the three-phase arm replacement drive operations.

  The flowchart of FIG. 8 shows a detailed flow of the output pattern determination / control processing in step S7.

  In step S7a, if the combination of flag settings is the normal operation flag F1 = OFF, the two-phase operation flag F2 = OFF, and the three-phase operation flag F3 = OFF, it is indefinite and the process returns to step S1 again.

  In step S7a, if the combination of flag settings is a normal operation flag F1 = OFF, a two-phase operation flag F2 = OFF, and a three-phase operation flag F3 = OFF, a combination of flag settings during a one-phase operation, a normal operation It is determined whether the flag F1 = ON, the two-phase operation flag F2 = OFF, and the three-phase operation flag F3 = OFF. If the combination is a combination of the one-phase operation flag settings, the output pattern is determined in step S7c. The control is determined as one-phase (U-phase) control, and the DC / DC converter 20 is controlled by the above-described one-phase arm drive operation, that is, normal operation (see FIG. 5).

  If it is determined in step S7b that the combination is not a one-phase operation flag setting combination, in step S7d, the flag setting combination is a normal operation flag F1 = OFF, a two-phase operation flag F2 = ON, and a three-phase operation flag F3 =. If it is determined whether or not it is a combination of two-phase operation flag settings, the output pattern is determined to be two-phase (U-phase and V-phase) alternating drive control in step S7e, and the two-phase described above The DC / DC converter 20 is controlled by the arm replacement drive operation (see FIG. 4).

  If it is determined in step S7d that the combination is not a two-phase operation flag setting combination, in step S7f, the flag setting combination is a normal operation flag F1 = OFF, a two-phase operation flag F2 = OFF, and a three-phase operation flag F3 =. If it is determined whether or not it is a combination of three-phase operation flag settings, in step S7g, the output pattern is determined as three-phase (U-phase, V-phase and W-phase) alternating drive control, and the above-mentioned The DC / DC converter 20 is controlled by the three-phase arm replacement driving operation (see FIG. 3).

  If the determination in step S7f is negative, the control is repeated again from step S1, assuming that the combination of flag settings is unknown.

D. Summary As described above, the DC / DC converter 20 includes the switching elements 81u, 82u, 81v, 82v, 81w, and 82w between the primary side 1S and the secondary side 2S, and performs phase conversion. This is a DC / DC converter 20 in which UA, VA, and WA are connected in parallel in three phases. Note that the present invention can also be applied to a DC / DC converter in which only two phases, for example, the phase arm UA and the phase arm VA are connected in parallel.

  Further, the DC / DC converter device 50 includes a temperature sensor 69 that detects element temperatures of the switching elements 81u, 82u, 81v, 82v, 81w, and 82w, and the detected element temperatures Tuh, Tul, Tvh, Tvl, Twh, and Twl. A converter control unit 48 that switches control from driving only the one-phase arm UA to alternate driving of a plurality of phase arms (in the case of two phases, the phase arm UA and the phase arm UV) as it rises.

  Thus, by switching from the driving (operation) of only the one-phase arm UA to the phase arm replacement driving (operation) in accordance with the temperature rise of the switching elements 81u, 82u, 81v, 82v, 81w, 82w, DC / DC Without suppressing the power passing through the converter 20, the temperature rise of the switching elements 81u, 82u, 81v, 82v, 81w, and 82w can be suppressed.

  In this case, the converter control unit 48 increases the detected element temperature Tuh, Tul, Tvh, Tvl, Twh, Twl from the driving (operation) of only the one-phase arm UA to the two-phase arm (UA / VA). By switching the control to the alternate drive (operation) and further to the alternate drive (operation) of the three-phase arm (UA / VA / WA), the switching order of the control in the case of the three-phase arm becomes clear.

  Since the temperature threshold values Tth1, Tth2, Tth3, and Tth4 when switching control are provided with hysteresis, switching chattering due to temperature fluctuation at the time of control switching is prevented, and switching control is stabilized. it can.

  Further, the one-phase arm UA that is driven when the element temperature Tuh, Tul, Tvh, Tvl, Twh, Twl is not increased (Tmax1 ≦ Tth1) is a fixed phase arm, and the fixed one-phase arm UA It is preferable to set the power rating of the switching elements 81u and 82u to be larger than the power rating of the switching elements 81v, 82v, 81w and 82w of the other phase arms VA and WA. In this way, the power rating of the switching element 81u, 82u of the fixed one-phase arm UA that is driven most frequently is larger than the power rating of the switching elements 81v, 82v, 81w, 82w of the other phase arms UV, UW. By setting, the life (average failure time) of the DC / DC converter 20 can be extended.

  Further, when switching elements having the same power rating are used, each time the main switch 34 of the DC / DC converter device 50 is turned on, the one-phase is driven when the element temperature is not increased. The arm may be switched to another one-phase arm and driven (if the previous phase arm UA was driven as a normal phase arm, the current phase arm UV is driven as a normal phase arm, etc.). In this way, the life (average failure time) of the DC / DC converter device 50 can be extended by switching the phase arm that is driven by only one phase arm each time the main switch 34 is turned on. .

  The present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification.

  For example, as shown in another embodiment of FIG. 9, a step-up three-phase synchronous switching DC / DC converter in which the upper arm switching elements 81u, 81v, 81w and the lower arm diodes 84u, 82v, 82w are omitted. The same applies to the device 50a. Needless to say, the present invention can be similarly applied to a step-up two-phase synchronous switching DC / DC converter device, and can also be applied to a step-down multi-phase synchronous switching DC / DC converter device.

1 is a schematic overall configuration diagram of a fuel cell vehicle according to an embodiment of the present invention. It is a circuit diagram which shows the detailed structure of the DC / DC converter which concerns on this embodiment. It is a time chart used for description of a three-phase arm replacement drive operation. It is a time chart used for description of a two-phase arm replacement drive operation. It is a time chart with which it uses for description of 1 phase arm drive operation | movement. It is a flowchart with which description of the drive method of the DC / DC converter apparatus according to the temperature of a switching element is provided. FIG. 6 is a characteristic diagram showing the relationship between the maximum value of element temperature and the number of drive phases. It is a detailed flowchart of an output pattern determination / control process. It is explanatory drawing of other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Fuel cell vehicle 11 ... Fuel cell system 12 ... Battery 14 ... Fuel cell 16 ... Motor 20 ... DC / DC converter 48 ... Converter control part 50 ... DC / DC converter apparatus

Claims (6)

A DC / DC converter device in which a plurality of phase arms having a switching element and performing voltage conversion are connected in parallel between a primary side and a secondary side,
A temperature sensor for detecting an element temperature of the switching element;
A control unit that switches control from driving of only one phase arm to alternating driving of a plurality of phase arms as the detected element temperature rises;
A DC / DC converter device comprising: The DC / DC converter device according to claim 1, wherein
The control unit switches the control from driving of only one phase arm to driving of two-phase arm, and further driving of three-phase arm as the detected element temperature rises. apparatus. The DC / DC converter device according to claim 1 or 2,
A DC / DC converter device characterized in that a hysteresis is given to a temperature threshold when switching control. In the DC / DC converter device according to any one of claims 1 to 3,
The one-phase arm driven when the element temperature is not raised is a fixed phase arm, and the power rating of the switching element of the fixed phase arm is larger than the power rating of the switching element of the other phase arm. A DC / DC converter device characterized by setting. The DC / DC converter device according to claim 1 or 2,
Each time the main switch of the DC / DC converter device is turned on, the one-phase arm that is driven when the element temperature has not risen is switched to another one-phase arm for driving. DC / DC converter device. A control method of a DC / DC converter device in which a plurality of phase arms having a switching element and performing voltage conversion are connected in parallel between a primary side and a secondary side,
Detecting the element temperature of the switching element;
A control method for a DC / DC converter device, wherein the control is switched from driving of only one phase arm to alternating driving of a plurality of phase arms as the detected element temperature rises.

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