JP5226501B2 - DC / DC converter device - Google Patents

Description

  The present invention relates to a DC / DC converter device including a step-up switching element and a step-down switching element. More specifically, the present invention relates to a DC / DC converter device that alternately outputs a drive signal to a step-down switching element and a step-up switching element with a dead time between switching periods.

  So-called synchronous switching control is known in which drive signals are alternately output to a step-down switching element and a step-up switching element for each switching period (for example, Patent Document 1). In the synchronous switching control of Patent Document 1, a dead time is sandwiched between drive signals in order to prevent the step-down switching element and the step-up switching element from flowing simultaneously and short-circuiting (for example, FIG. 9 of Patent Document 1). (See (a)).

International Publication No. 02/093730 Pamphlet

  In Patent Document 1, there is a description of a dead time generation method (for example, FIGS. 9 (a) and 9 (b) and page 11, line 5 to the last line of Patent Document 1). No consideration has been given to the controllability of the DC / DC converter device considered.

  The present invention has been made in consideration of such problems, and an object thereof is to provide a DC / DC converter device capable of improving the controllability of the DC / DC converter device in synchronous switching control.

The DC / DC converter device according to the present invention alternately includes a step-down switching element, a step-up switching element, a reactor, and the step-down switching element and the step-up switching element with a dead time between switching periods. And a control unit that outputs a drive signal to the chopper type DC / DC converter device, wherein the control unit calculates a drive duty of at least one of the step-down switching element and the step-up switching element. And a drive signal to the step-down switching element and the step-up switching element in a period obtained by subtracting the dead time from the drive period of the step-down switching element and the step-up switching element determined based on the drive duty, respectively. An output unit for outputting, The arithmetic unit is in any one of the case where the DC / DC converter device is in only the step-down state, only the step-up state, or both the step-down state and the step-up state appear in each switching cycle. When the step-down switching element is determined to be only in the step-down state, the dead-end switching element drive period determined based on the drive duty is actually set to the dead period during the period in which the step-down switching element is actually driven. When the drive duty is set so as to be a period to which a period for time is added and it is determined that only the step-up state is present, the drive period of the step-up switching element determined based on the drive duty is: It is a period in which the period corresponding to the dead time is added to the period in which the boosting switching element is actually driven. The set driving duty, the DC / DC converter apparatus, the entire each switching cycle, when the only step-down state, if the only step-up state, or both the step-down state and the boosting state appears In any case, the output unit is a period obtained by subtracting the dead time of the same length from the driving period of the step-down switching element and the step-up switching element determined based on the driving duty. A drive signal is output to the step-down switching element and the step-up switching element .

  According to the present invention, in the so-called synchronous switching control in which the drive signal is alternately output to the step-down switching element and the step-up switching element with a dead time in every switching cycle, the step-down operation that actually operates (flows). The switching element or the boosting switching element is not affected by the dead time, and the controllability when the polarity of the current passing through the DC / DC converter device is changed can be improved.

  The DC / DC converter device further includes a current sensor that measures a current on a primary side where the reactor is disposed, the calculation unit calculates a drive duty of the step-down switching element, and the output unit The drive signal is output to the step-down switching element in a period obtained by subtracting the dead time from the period corresponding to the drive duty, and the period corresponding to the drive duty and the dead time are subtracted from the switching period. The driving signal is output to the step-up switching element, and the calculation unit further outputs the primary side current from the secondary side opposite to the primary side in one switching cycle. When only negative flowing to the side, a correction amount corresponding to the dead time is added in advance to calculate the drive duty, When the primary side current is only positive flowing from the primary side to the secondary side in one switching cycle, the correction amount is subtracted in advance to calculate the drive duty, and the primary side current is calculated. When the current crosses zero amperes in one switching cycle, the driving duty may be calculated by reducing the correction amount.

  Alternatively, the calculation unit calculates a driving duty of the boosting switching element, and the output unit outputs the driving signal to the boosting switching element in a period obtained by subtracting the dead time from a period with respect to the driving duty. And outputting the drive signal to the step-down switching element in a period obtained by subtracting the period corresponding to the drive duty and the dead time from the switching period, and the arithmetic unit further includes the primary side in one switching period. When the current polarity is only positive, the driving duty is calculated by adding a correction amount corresponding to the dead time in advance, and when the polarity of the primary current is only negative in one switching cycle, The drive duty is calculated by subtracting the correction amount in advance, and the primary side current is one switching cycle. In, when crossing the zero amps, it may be calculated the driving duty reduces the correction amount.

  The calculation unit sets in advance a positive current threshold and a negative current threshold for determining whether or not the primary current exceeds zero ampere, and a peak value of the primary current And a bottom value is determined, and a value close to zero ampere among the peak value and the bottom value is between the positive current threshold value and the negative current threshold value, or between the peak value and the bottom value. When the value is between the positive current threshold and the negative current threshold, it may be determined that the primary current is over zero amperes.

  The calculation unit may decrease the correction amount as the value close to the zero ampere or the intermediate value moves from the positive current threshold or the negative current threshold toward zero ampere.

  The calculation unit may set the correction amount to zero when an intermediate value between the peak value and the bottom value is zero amperes.

  When it is determined that the current on the primary side crosses zero amperes, the arithmetic unit may perform a filtering process that restricts a change to a value close to the zero amperes or the intermediate value. Alternatively, when it is determined that the primary current is over zero amperes, the arithmetic unit may perform a filtering process for limiting the change in the correction amount.

  According to the present invention, in the so-called synchronous switching control in which the drive signal is alternately output to the step-down switching element and the step-up switching element with a dead time in every switching cycle, the step-down operation that actually operates (flows). The switching element or the boosting switching element is not affected by the dead time, and the controllability when the polarity of the current passing through the DC / DC converter device is changed can be improved.

1. Explanation of overall configuration [Overall configuration]
FIG. 1 shows a schematic overall configuration diagram of a fuel cell vehicle 10 equipped with a DC / DC converter device 50 according to an embodiment of the present invention.

  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. The generated current generated by the 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 via the diode 13.

  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 a chopper type voltage converter in which one side is connected to the battery 12 and the other side is connected to the secondary side 2S that is a connection point between the fuel cell 14 and the motor 16.

  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 the overall control unit 40. 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 overall 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.

2. 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 a phase arm UA disposed between the primary side 1S and the secondary side 2S, and a reactor 90.

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

  As the upper arm switching element 81 and the lower arm switching element 82, for example, a MOSFET or an IGBT is employed.

  Reactor 90 is inserted between the midpoint (common connection point) of phase arm UA and the positive electrode of battery 12, and converts voltage between primary voltage V1 and secondary voltage V2 by DC / DC converter 20. In particular, it has the function of releasing and storing energy.

  The upper arm switching element 81 is turned on by the high level of the gate drive signal (drive voltage) UH output from the converter control unit 48, and the lower arm switching element 82 is turned on by the high level of the gate drive signal (drive voltage) UL. Turned on by. The converter control unit 48 detects the primary voltage V1 by the voltage sensor 91 provided in parallel with the smoothing capacitor 94 on the primary side, detects the primary current I1 by the current sensor 101, and smoothes the secondary side. The secondary voltage V2 is detected by the voltage sensor 92 provided in parallel with the capacitor 96, and the secondary current I2 is detected by the current sensor 102.

  FIG. 3 is a functional block diagram illustrating a flow in which the converter control unit 48 generates the drive signals UH and UL in the present embodiment.

  Converter control unit 48 includes a calculation unit 120 and an output unit 122. The calculation unit 120 and the output unit 122 may be configured as either hardware or software.

  The converter control unit 48 uses so-called synchronous switching control. The synchronous switching control is a control for outputting drive signals UH and UL to the upper arm switching element 81 and the lower arm switching element 82 in each switching cycle Tsw [s] (see FIG. 4). A dead time dt [s] is set between the outputs of the drive signals UH and UL to prevent a short circuit.

  The calculation unit 120 calculates a target duty DUTtar (control drive duty) [%] that defines an output period [s] of the drive signals UH and UL in one switching cycle Tsw.

  The calculation unit 120 includes a subtractor 130, a feedback term calculation unit 132 (hereinafter also referred to as “FB term calculation unit 132”), and a feedforward term calculation unit 134 (hereinafter also referred to as “FF term calculation unit 134”). , A correction duty calculation unit 136, a first adder 138, and a second adder 140.

  The subtractor 130 is a difference ΔV2 (= V2com−V2) between the command value (secondary voltage command value V2com) [V] of the secondary voltage V2 from the overall control unit 40 and the secondary voltage V2 from the voltage sensor 92. [V] is calculated and output to the FB term calculation unit 132.

  The FB term computing unit 132 computes a feedback term (hereinafter also referred to as “FB term”) by PID control (proportional / integral / derivative control) using the difference ΔV <b> 2 from the subtractor 130.

  The FF term calculation unit 134 is a feedforward term (hereinafter also referred to as “FF term”) that is a quotient V1 / V2com of the primary voltage V1 from the voltage sensor 91 and the secondary voltage command value V2com from the overall control unit 40. ) Is calculated.

  The correction duty calculator 136 calculates a correction duty DUTcor [%] based on the primary current I1 from the current sensor 101. The correction duty DUTcor is a correction amount for reducing the difference between the target duty DUTtar and the output period of the drive signals UH and UL due to the influence of the dead time dt.

  The first adder 138 adds the FB term from the FB term computing unit 132 and the FF term from the FF term computing unit 134. The second adder 140 adds the sum of the FB term and the FF term from the first adder 138 and the correction duty DUTcor from the correction duty calculator 136 and outputs the result to the output unit 122 as the target duty DUTtar.

  The target duty DUTtar in the present embodiment is the drive duty of the upper arm switching element 81, that is, the ratio of the period during which the drive signal UH is output to the upper arm switching element 81 in one switching cycle Tsw [s] (drive signal UH The ratio of the period during which is at a high level) [%]. The ratio of the period during which the drive signal UL is output to the lower arm switching element 82 in one switching cycle Tsw (the ratio of the period during which the drive signal UL is at a high level) ranges from 100% to the ratio of the upper arm switching element 81. It is assumed that it was subtracted.

  The output unit 122 outputs the drive signals UH and UL based on the target duty DUTtar from the calculation unit 120. Specifically, in one switching period Tsw, a period corresponding to the target duty DUTtar (upper arm target driving period Tud_tar) [s] minus a dead time dt (upper arm driving period Tud) [s], upper arm switching A drive signal UH is output to the element 81. Further, the output unit 122 calculates a period (lower arm target drive period Tld_tar) [s] obtained by subtracting the upper arm target drive period Tud_tar from one switching cycle Tsw, and further calculates a dead time dt from the lower arm target drive period Tld_tar. During the subtracted period (lower arm driving period Tld) [s], the driving signal UL is output to the lower arm switching element 82.

[Operation of DC / DC converter device]
(Synchronous switching control)
The time chart of FIG. 4 is an explanatory diagram of the synchronous switching control 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.

  In the waveform of the drive signals UH and UL, during the hatched period, the arm switching element to which the drive signals UH and UL are supplied (for example, the upper arm switching element 81u is the arm switching element corresponding to the drive signal UH). The period during which current is flowing (current is flowing) is shown.

  In both the step-down chopper control and the step-up chopper control of the DC / DC converter 20, high level drive signals UH and UL are applied to the upper arm switching element 81 and the lower arm switching element 82 for each switching period Tsw. Output. In the step-down chopper control, the upper arm switching element 81 is allowed to flow, and in the step-up chopper control, the lower arm switching element 82 is allowed to flow.

  In this case, in order to prevent the secondary voltage V2 from being short-circuited through the upper and lower arm switching elements 81 and 82 at the same time, the drive signals UH and UL are set to the high level with the dead time dt interposed therebetween. I have to. That is, synchronous switching is performed with the dead time dt interposed therebetween.

  In the step-down chopper control, first, during the period in which only the upper arm switching element 81 is passed by the drive signal UH, the secondary current I2 flows as the primary current I1 to the reactor 90 through the upper arm switching element 81 and flows to the reactor 90. Energy is stored and the battery 12 is charged.

  Next, during the period when only the drive signal UL is at a high level, the lower arm switching element 82 does not flow, the diode 84 is turned on, and the energy stored in the reactor 90 is released, and the battery 12 is discharged. Charged.

  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 is at a high level (a period indicated by hatching). At this time, a current is supplied from the smoothing capacitor 96 on the secondary side to the load 23.

  Next, during the period when only the drive signal UH is at the high level, the upper arm switching element 81 does not flow, the diode 83 is turned on, and the energy accumulated in the reactor 90 is released, and the reactor 90 releases the energy. The primary current I1 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.

[Calculation of target duty DUTtar]
In this embodiment, in order to reduce the influence of the dead time dt, the target duty DUTtar is calculated with correction according to the polarity of the primary current I1 in each switching cycle Tsw.

  FIG. 5 is an explanatory diagram of the relationship among the target duty DUTtar, the drive signals UH and UL, and the primary current I1.

  As described above, in the present embodiment, the target duty DUTtar defines the drive period of the upper arm switching element 81 {for step-down (regeneration)}. That is, the calculation unit 120 calculates the target duty DUTtar, and the output unit 122 calculates the dead time dt from a period (upper arm target drive period Tud_tar) [s] corresponding to the target duty DUTtar [%] in one switching cycle Tsw. During the subtracted period (upper arm drive period Tud) [s], the drive signal UH is output to the upper arm switching element 81u (Tud = Tud_tar-dt).

  Further, in the calculation unit 120, a period obtained by subtracting the upper arm target drive period Tud_tar from one switching cycle Tsw is a period for driving the lower arm switching element 82 {for boosting (assist)} (lower arm target drive period Tld_tar). (Tld_tar = Tsw-Tud_tar). The output unit 122 outputs the drive signal UL to the lower arm switching element 82u during a period (lower arm drive period Tld) [s] obtained by subtracting the dead time dt from the lower arm target drive period Tld_tar (Tld = Tld_tar−dt). = Tsw-Tud_tar-dt).

  Thus, in order to insert the two dead times dt, the upper arm target drive period Tud_tar and the lower arm target drive period Tld_tar determined based on the target duty DUTtar, and actually the upper arm switching element 81 and the lower arm switching element A difference corresponding to the dead time dt is generated between the upper arm driving period Tud and the lower arm driving period Tld in which the drive signals UH and UL are output to 82. As a result, the controllability of the DC / DC converter 20 is affected.

  For example, when the polarity of the primary current I1 is positive in the entire switching period Tsw from the time point t1 to the time point t7 as in the case of the primary current I1a in FIG. 5, the upper arm drive determined based on the target duty DUTtar. The period Tud (the upper arm target drive period Tud_tar minus the dead time dt) is from time t2 to time t4. During this period, the drive signal UL is not supplied to the lower arm switching element 82 for boosting, and the current flows through the diode 83, so that the upper arm switching element 81 for stepping down does not operate (flow). Further, the lower arm drive period Tld (based on the lower arm target drive period Tld_tar minus the dead time dt) determined based on the target duty DUTtar is from time t5 to time t7. During this period, the lower arm switching element 82 for boosting operates (flows) and performs boosting operation. Note that neither the upper arm switching element 81 nor the lower arm switching element 82 operates at the dead time dt from the time point t1 to the time point t2 and the dead time dt from the time point t4 to the time point t5.

  As a result, when the polarity of the primary current I1 is positive in the entire switching cycle Tsw, the lower arm switching element 82 for boosting operates during the lower arm driving period Tld, which is determined based on the target duty DUTtar. Is not the lower arm target drive period Tld_tar. Therefore, the boosting operation for the dead time dt is not performed.

  Therefore, in the present embodiment, the target duty DUTtar is calculated so that a period corresponding to the dead time dt is added in advance to the lower arm target drive period Tld_tar. That is, the correction duty DUTcor output from the correction duty calculation unit 136 is “(−dt / Tsw) × 100”. Here, the reason why the correction duty DUTcor is a negative value is that the target duty DUTtar directly defines the upper arm target drive period Tud_tar, and the upper arm target drive period Tud_tar is decreased by decreasing the upper arm target drive period Tud_tar. This is because the arm target drive period Tld_tar increases.

  Next, for example, when the polarity of the primary current I1 is negative in the entire switching period Tsw from the time point t1 to the time point t7 as in the case of the primary current I1b in FIG. 5, it is determined based on the target duty DUTtar. The upper arm drive period Tud is from time t2 to time t4. During this period, the upper arm switching element 81 for step-down operates (flows) and performs step-down operation. On the other hand, the lower arm drive period Tld determined based on the target duty DUTtar is from time t5 to time t7. During this period, the drive signal UL is not supplied to the step-up upper arm switching element 81, and a current flows through the diode 84, so that the step-up lower arm switching element 82 does not operate (flow). Further, neither the upper arm switching element 81 nor the lower arm switching element 82 operates in the dead time dt from the time point t1 to the time point t2 and the dead time dt from the time point t4 to the time point t5.

  As a result, when the polarity of the primary current I1 is negative in the entire switching period Tsw, the step-down upper arm switching element 81 operates during the upper arm drive period Tud, which is determined based on the target duty DUTtar. This is not the upper arm target drive period Tud_tar. Therefore, the step-down operation for the dead time dt is not performed.

  Therefore, in the present embodiment, the target duty DUTtar is calculated so that a period corresponding to the dead time dt is added in advance to the upper arm target drive period Tud_tar. That is, the correction duty DUTcor output from the correction duty calculation unit 136 is “(dt / Tsw) × 100”. Here, the reason why the correction duty DUTcor is a positive value is that the target duty DUTtar directly defines the upper arm target drive period Tud_tar, and the upper arm target drive period is increased by increasing the correction duty DUTcor. This is because Tud_tar increases.

  Further, for example, when the polarity of the primary current I1 changes from negative to positive or from positive to negative in the entire switching period Tsw from the time point t1 to the time point t7 as in the primary current I1c of FIG. When the current I1 crosses zero ampere), the upper arm driving period Tud determined based on the target duty DUTtar is from time t2 to time t4. During this period, when the polarity of the primary current I1c is positive (time points t2 to t3), neither the upper arm switching element 81 nor the lower arm switching element 82 is activated (flowed). When the polarity of the primary current I1c is negative (time points t3 to t4), the upper arm switching element 81 is activated to perform a step-down operation.

  On the other hand, the lower arm drive period Tld determined based on the target duty DUTtar is from time t5 to time t7. During this period, when the polarity of the primary current I1c is negative (time points t5 to t6), neither the upper arm switching element 81 nor the lower arm switching element 82 operates (flows). Further, when the polarity of the primary current I1c is positive (time t6 to t7), the lower arm switching element 82 is activated to perform a boosting operation.

  As a result, each of the upper arm switching element 81 and the lower arm switching element 82 operates when the primary current I1 crosses zero amperes in the entire switching period Tsw as in the primary current I1c. That is, in the primary current I1c, the upper arm switching element 81 operates (flows) from time t3 to time t4, and the lower arm switching element 82 operates (flows) from time t6 to time t7, so that the upper arm Both the switching element 81 and the lower arm switching element 82 operate. If the drive period of one of the upper arm switching element 81 and the lower arm switching element 82 is increased by the dead time dt, the other driving period is decreased. Therefore, the dead time is simply set like the primary currents I1a and I1b. The drive period of dt cannot be compensated. Therefore, in the present embodiment, the correction duty DUTcor is set to zero when the primary current I1 crosses zero amperes over the entire switching period Tsw. As will be described later, the correction duty DUTcor can be gradually changed.

  FIG. 6 shows the relationship between the primary current I1 and the correction duty DUTcor. In the present embodiment, the correction duty DUTcor is changed according to the peak value I1p [A] and the bottom value I1btm [A] of the primary current I1 in each switching cycle Tsw.

  When the peak value I1peak and the bottom value I1btm are both less than zero ampere (I1b, I1p <0) as in the primary current I1d of FIG. 6, that is, the polarity of the primary current I1 is 1 switching cycle Tsw. When it is negative, the correction duty DUTcor is set to “(dt / Tsw) × 100”.

  When the peak value I1peak is equal to or higher than zero ampere (I1p ≧ 0) and the bottom value I1btm is equal to or lower than zero ampere (I1b <0) as in the primary current I1e of FIG. When the polarity of the current I1 changes from positive to negative or from negative to positive, the correction duty DUTcor is set to zero.

  When the peak value I1peak and the bottom value I1btm both exceed zero ampere (I1p, I1b> 0) as in the primary current I1f of FIG. 6, that is, the polarity of the primary current I1 is positive in the entire switching period Tsw. In this case, the correction duty DUTcor is set to “(−dt / Tsw) × 100”.

[Effect of this embodiment]
As described above, according to the present embodiment, in synchronous switching control, the upper arm switching element 81 or the lower arm switching element 82 that actually operates (flows) is not affected by the dead time dt, and the DC / DC Controllability when the polarity of the primary current I1 passing through the converter device 50 is changed can be improved.

  Further, the output unit 122 performs a process of equally allocating the dead time dt to the upper arm switching element 81 and the lower arm switching element 82 as the calculation of the dead time dt. In the calculation of the target duty DUTtar in the calculation unit 120, the primary time Feed forward correction in accordance with the state of the current I1 is performed. That is, an error corresponding to the dead time dt is not corrected in the feedback control, but a correction duty DUTcor considering the dead time dt is added in advance in the feedforward control. As a result, it is possible to simplify the calculation of the dead time dt. As a result, it is possible to achieve both the reliability of short circuit prevention and the improvement of controllability when the primary current I1 crosses zero amperes.

3. Modifications It should be noted that 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, the following configuration can be adopted.

[Target]
In the above embodiment, the DC / DC converter device 50 is mounted on the fuel cell vehicle 10, but is not limited thereto, and may be mounted on another target. For example, the DC / DC converter device 50 can be used for a moving body such as a ship or an aircraft. Alternatively, the DC / DC converter device 50 may be applied to a household power system.

[DC / DC converter]
In the above embodiment, the number of the upper arm switching elements 81 and the number of the lower arm switching elements 82 is one. However, the number is not limited to this, and may be two or more.

[Calculator]
In the above embodiment, the correction duty DUTcor is added by the second adder 140, but the present invention is not limited to this. For example, it is possible to add to the FF term calculated by the FF term calculation unit 132.

  FIG. 7 shows a configuration of a converter control unit 48a having a calculation unit 120a as a modification of the calculation unit 120. In the calculation unit 120a, the FF term calculated by the FF term calculation unit 134 and the correction duty DUTcor calculated by the correction duty calculation unit 136 are added by the first adder 142, and the sum (FF term + correction duty DUTcor) is added. ) And the FB term calculated by the FB term calculation unit 132 are added by the second adder 144 to calculate the target duty DUTtar.

[Correction duty]
In the above embodiment, as shown in FIG. 6, the relationship between the primary current I1 and the correction duty DUTcor has three types of correction duty DUTcor according to the primary current I1, but the present invention is not limited to this.

  FIG. 8 shows a first modification of the relationship between the primary current I1 and the correction duty DUTcor. In the first modification, the relationship between the peak value I1p [A] and the bottom value I1btm [A] of the primary current I1 and the positive current threshold THmax [A] and the negative current threshold THmin [A] in each switching period Tsw. The correction duty DUTcor is changed according to the above. The positive current threshold value THmax and the negative current threshold value THmin are set to values that can determine the operating state of the DC / DC converter 20 (step-down (regeneration), step-up (assist), or crossing zero amps).

  As in the case of the primary current I1g in FIG. 8, when both the peak value I1peak and the bottom value I1btm are less than the negative current threshold THmin (I1b, I1p <THmin), that is, the primary current I1 over the entire switching period Tsw. Is negative, the correction duty DUTcor is set to “(dt / Tsw) × 100”.

  When the peak value I1peak is between the positive current threshold THmax and the negative current threshold THmin (THmin <I1p <THmax) as in the primary current I1h in FIG. 8, as in the primary current I1i in FIG. When the peak value I1peak exceeds the positive current threshold THmax (I1p> THmax) and the bottom value I1btm is less than the negative current threshold THmin (I1b <THmin), or the primary current I1j in FIG. When the value I1btm is between the positive current threshold THmax and the negative current threshold THmin (THmin <I1b <THmax), the correction duty DUTcor is set as shown by the characteristic C1 in FIG.

  That is, the correction duty DUTcor is set in the range of “(dt / Tsw) × 100” to “(−dt / Tsw) × 100” by the value closer to zero ampere among the peak value I1peak and the bottom value I1btm.

  FIG. 9 shows an explanatory diagram when the correction duty DUTcor is set for the primary current I1l. In FIG. 8, the vertical axis represents the correction duty DUTcor and the horizontal axis represents the primary current I1, whereas in FIG. 9, the vertical axis represents the primary current I1 and the horizontal axis represents the correction duty DUTcor. Please keep in mind. In the primary current I1l, since the bottom value I1btm is closer to zero ampere than the peak value I1peak, the correction value DUTcor is determined using the bottom value I1btm. According to the first modification, the correction duty DUTcor can be changed smoothly.

  FIG. 10 is an explanatory diagram of a second modification of the relationship between the primary current I1 and the correction duty DUTcor. The second modified example is basically the same as the first modified example, except that a filter process for limiting a change in the value of the peak value I1peak and the bottom value I1btm that is closer to zero amperes is performed. This is different in that the correction duty DUTcor is determined. Examples of filter processing include first-order lag processing and averaging processing. According to the second modification, it is possible to limit the change in the correction duty DUTcor and suppress the primary current I1 from fluctuating excessively.

  FIG. 11 is an explanatory diagram of a third modification of the relationship between the primary current I1 and the correction duty DUTcor. The third modified example is basically the same as the first modified example, but changes in the value with respect to the correction duty DUTcor determined from the value closer to zero ampere among the peak value I1peak and the bottom value I1btm. Is different in that the post-filter processing correction duty DUTcor2 is determined. Examples of filter processing include first-order lag processing and averaging processing. According to the third modification, it is possible to limit the change in the correction duty DUTcor and suppress the primary current I1 from fluctuating excessively.

  In the above embodiment, the target duty DUTtar directly defines the upper arm target drive period Tud_tar (the target period for driving the upper arm switching element 81 in one switching cycle Tsw), but the lower arm target drive period A configuration in which Tld_tar (a target period for driving the lower arm switching element 82 in one switching period Tsw) is directly defined is also possible. In this case, for example, when the polarity of the primary current I1 is only positive in one switching cycle Tsw, the calculation unit 120 calculates the target duty DUTtar using “(dt / Tsw) × 100” as the correction duty DUTcor, When the polarity of the primary current I1 is only negative in the switching period Tsw, the target duty DUTtar is calculated with “(−dt / Tsw) × 100” as the correction duty DUTcor, and the primary current I1 is zero in the one switching period Tsw. When straddling amperes, the target duty DUTtar can be calculated by reducing the correction duty DUTcor.

  In the first to third modified examples of FIGS. 8 to 11, the correction duty DUTcor is determined using a value close to zero ampere among the peak value I1peak and the bottom value I1btm, but is not limited thereto. For example, the correction duty DUTcor may be determined using an intermediate value between the peak value I1peak and the bottom value I1btm.

1 is a schematic overall configuration diagram of a fuel cell vehicle equipped with a DC / DC converter device 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 the said embodiment. It is a circuit diagram which shows the detailed structure of the converter control part which concerns on the said embodiment. It is a time chart used for description of the synchronous switching control in the said embodiment. It is explanatory drawing which shows the relationship between a target duty, a drive signal, and a primary current. It is explanatory drawing which shows the relationship between a primary current and correction | amendment duty. It is a circuit diagram which shows the structure of the modification of a converter control part. It is explanatory drawing which shows the 1st modification of the relationship between the primary current I1 and correction | amendment duty. It is explanatory drawing in the case of setting correction | amendment duty using the relationship of FIG. It is explanatory drawing which shows the 2nd modification of the relationship between the primary current I1 and correction | amendment duty. It is explanatory drawing which shows the 3rd modification of the relationship between the primary current I1 and correction | amendment duty.

Explanation of symbols

48 ... Converter control unit (control unit) 50 ... DC / DC converter device 81 ... Upper arm switching element 82 ... Lower arm switching element 90 ... Reactor 101, 102 ... Current sensor 120, 120a ... Calculation unit 122 ... Output unit dt ... Dead Time DUTtar ... Target duty (drive duty)
I1 ... primary current I1btm ... bottom value of primary current I1peak ... peak value of primary current THmax ... positive current threshold THmin ... negative current threshold Tsw ... switching period UH, UL ... drive signal 1S ... primary side 2S ... Secondary side

Claims (8)

A step-down switching element;
A step-up switching element;
Reactor,
A chopper type DC / DC converter device comprising: a step-down switching element and a control unit that alternately outputs a drive signal to the step-up switching element across a dead time for each switching period,
The controller is
A calculation unit for calculating a drive duty of at least one of the step-down switching element and the step-up switching element;
A drive signal is output to the step-down switching element and the step-up switching element in a period obtained by subtracting the dead time from the drive period of the step-down switching element and the step-up switching element determined based on the drive duty. An output section, and
The computing unit is
Determining whether the DC / DC converter device is in a step-down state only, in a step-up state only, or in a case where both the step-down state and the step-up state appear in each switching period,
When it is determined that only the step-down state is present, the drive period of the step-down switching element determined based on the drive duty is a period corresponding to the dead time during the period in which the step-down switching element is actually driven. The drive duty is set so as to be a period to which
When it is determined that only the step-up state is present, the drive period of the step-up switching element determined based on the drive duty is a period corresponding to the dead time during the period during which the step-up switching element is actually driven. the set driving duty so that the additional time period,
Whether the DC / DC converter device is only in the step-down state, only the step-up state, or both the step-down state and the step-up state appear in each switching cycle, The output unit includes the step-down switching element and the step-up voltage in a period obtained by subtracting the dead time of the same length from the drive period of the step-down switching element and the step-up switching element determined based on the driving duty. DC / DC converter device characterized in that a drive signal is output to the switching element for use . The DC / DC converter device according to claim 1, wherein
The DC / DC converter device further includes a current sensor that measures a primary current at which the reactor is disposed,
The calculation unit calculates a drive duty of the step-down switching element,
The output unit outputs the drive signal to the step-down switching element in a period obtained by subtracting the dead time from a period corresponding to the drive duty, and a period corresponding to the drive duty and the dead time from the switching period. The drive signal is output to the boosting switching element in a period obtained by subtracting
Furthermore, the calculation unit includes:
When the primary current is only negative flowing from the secondary side opposite to the primary side to the primary side in one switching cycle, a correction amount corresponding to the dead time is added in advance. To calculate the driving duty,
When the primary side current is only positive flowing from the primary side to the secondary side in one switching cycle, the drive amount is calculated by subtracting the correction amount in advance,
The DC / DC converter device characterized in that, when the primary-side current crosses zero amperes in one switching cycle, the drive duty is calculated by reducing the correction amount. The DC / DC converter device according to claim 1, wherein
The DC / DC converter device further includes a current sensor that measures a primary current at which the reactor is disposed,
The calculation unit calculates a drive duty of the step-up switching element,
The output unit outputs the drive signal to the boosting switching element in a period obtained by subtracting the dead time from a period corresponding to the drive duty, and subtracts a period corresponding to the drive duty and the dead time from the switching period. Output the drive signal to the step-down switching element in a period of time,
Furthermore, the calculation unit includes:
When the primary side current is only positive flowing from the primary side to the secondary side opposite to the primary side in one switching cycle, a correction amount corresponding to the dead time is added in advance. To calculate the driving duty,
When the primary side current is only negative flowing from the secondary side to the primary side in one switching cycle, the drive duty is calculated by subtracting the correction amount in advance,
The DC / DC converter device characterized in that, when the primary-side current crosses zero amperes in one switching cycle, the drive duty is calculated by reducing the correction amount. In the DC / DC converter device according to any one of claims 1 to 3,
The computing unit is
A positive current threshold and a negative current threshold for determining whether or not the current on the primary side crosses zero amperes are set in advance,
Determining a peak value and a bottom value of the primary current;
A value close to zero ampere among the peak value and the bottom value is between the positive current threshold and the negative current threshold, or an intermediate value between the peak value and the bottom value is the positive current threshold. When the current is between the negative current threshold and the negative current threshold, it is determined that the current on the primary side crosses zero amperes. The DC / DC converter device according to claim 4,
The arithmetic unit decreases the correction amount as the value close to zero amperage or the intermediate value moves from the positive current threshold value or the negative current threshold value toward zero ampere. DC / DC Converter device. The DC / DC converter device according to claim 4 or 5,
The said calculating part makes the said correction amount zero when the intermediate value of the said peak value and the said bottom value is zero ampere. The DC / DC converter apparatus characterized by the above-mentioned. In the DC / DC converter device according to any one of claims 4 to 6,
The arithmetic unit, when it is determined that the current on the primary side crosses zero amperes, performs a filtering process to limit the change to a value close to the zero amperes or the intermediate value. DC / DC converter device. In the DC / DC converter device according to any one of claims 4 to 6,
The DC / DC converter device according to claim 1, wherein the arithmetic unit performs a filter process for limiting a change in the correction amount when it is determined that the primary current is over zero amperes.

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