Control method for DC / DC converter and control device for DC / DC converter

Abstract

To provide a control method and a control device for a DC / DC converter capable of suppressing output voltage fluctuations that occur when a magnetization direction of a magnet forming a gap is reversed in a DC / DC converter that uses a variable magnetic reactor.SOLUTION: When a reactor 13 controls a DC / DC converter 100 composed of a core 21 forming a gap 23 with a magnet 24, whose magnetization direction is reversible, and a coil 22 wound around the core 21, it is determined whether or not a polarity of a load current IR, which is a current outputting to a load 11 is changed. Then, when the magnetization of the load current IR changes, a voltage (VC) of an output side capacitor 15 rises, and a magnetization inversion current IL-rev that reverses the magnetization direction of the magnet 24 flows to the coil 22 in a state where the voltage (VC) of the output side capacitor 15 rises.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control method and a control device for a DC / DC converter. [Background technology]

[0002] Patent Document 1 discloses a technique for suppressing fluctuations in the output voltage of a DC / DC converter by quickly correcting the duty ratio of a semiconductor switching element when the input voltage or load current fluctuates suddenly. Specifically, it discloses that the duty ratio is determined by feedback of the output voltage, and when the input voltage or the like fluctuates suddenly, the gain (sensitivity) of the feedback control is increased. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7120164 Summary of the Invention [Problem to be solved by the invention]

[0004] DC / DC converters are configured using reactors. When the input voltage or load current suddenly changes, the core can reach magnetic saturation, causing a sudden drop in the reactor's inductance. For this reason, a gap is usually provided in the reactor core. Typically, this is an air gap, but in recent years, the gap may be formed by a magnet whose magnetization direction can be reversed, in order to make it even easier to suppress magnetic saturation.

[0005] In this way, when using a reactor having a gap formed by a magnet whose magnetization direction can be reversed in the core (hereinafter referred to as a variable magnet reactor), a new problem arises in that the output voltage of the DC / DC converter fluctuates when the magnetization direction of the magnet is reversed.

[0006] An object of the present invention is to provide a control method and control device for a DC / DC converter that uses a variable magnetic reactor and that can suppress fluctuations in output voltage that occur when reversing the magnetization of a magnet that forms a gap. [Means for solving the problem]

[0007] One aspect of the present invention is a control method for a DC / DC converter that includes a reactor, a switch that controls the storage and release of energy in the reactor, and an output-side capacitor provided at an output end connected to a load, the reactor being configured with a core having a gap formed by a magnet whose magnetization direction can be reversed, and a coil wound around the core. This DC / DC converter control method determines whether the polarity of a load current that is a current output to the load will change, and when the polarity of the load current changes, increases the voltage of the output-side capacitor, and, with the voltage of the output-side capacitor increased, flows a magnetization reversal current through the coil that reverses the magnetization direction of the magnet. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a control method and a control device for a DC / DC converter that can suppress fluctuations in output voltage that occur when reversing the magnetization direction of a magnet that forms a gap in a DC / DC converter that uses a variable magnetic reactor. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a DC / DC converter. [Figure 2] FIG. 2 is a block diagram showing the configuration of the controller in the first embodiment. [Figure 3] FIG. 3 is a flowchart relating to the magnetization reversal control. [Figure 4] FIG. 4 is a graph schematically showing the transition of the output-side capacitor voltage and the like in the magnetization reversal control of the comparative example and the first embodiment. [Figure 5]FIG. 5 is a graph schematically showing the transition of the output-side capacitor voltage and the like in the magnetization reversal control of the second embodiment. [Figure 6] FIG. 6 is a block diagram showing the configuration of a controller in the third embodiment. [Figure 7] FIG. 7 is a graph schematically showing the transition of the output capacitor voltage and the like in the magnetization reversal control of the third embodiment. [Figure 8] FIG. 8 is a graph schematically showing the transition of the output-side capacitor voltage and the like in the magnetization reversal control of the comparative example and the fourth embodiment. [Figure 9] FIG. 9 is a block diagram showing the configuration of a controller in the fifth embodiment. [Figure 10] FIG. 10 is a graph schematically showing the transition of the output capacitor voltage and the like in the magnetization reversal control of the fifth embodiment. [Figure 11] FIG. 11 is a graph schematically showing the relationship between the initial voltage of the output capacitor and the amount of decrease in the output capacitor voltage during magnetization reversal control. [Figure 12] FIG. 12 is an explanatory diagram showing a method for determining the initial voltage. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0011] [First embodiment] Fig. 1 is an explanatory diagram showing the configuration of a DC / DC converter 100. As shown in Fig. 1, the DC / DC converter 100 is a converter that steps up or steps down a DC voltage input / output between a DC power supply 10 and a load 11. In this embodiment, the DC / DC converter 100 is provided in an electrically powered vehicle such as an electric vehicle or a hybrid vehicle.

[0012] The DC power supply 10 is a power supply that supplies DC power to the load 11 via the DC / DC converter 100. In this embodiment, the DC power supply 10 is a battery that stores power for driving an electric vehicle, and is configured by, for example, a lithium-ion battery. When power is supplied from the DC power supply 10 to the load 11, the DC / DC converter 100 functions as a boost converter. Hereinafter, the operation of the DC / DC converter 100 when power is supplied from the DC power supply 10 to the load 11 is referred to as power running (or power running operation).

[0013] The DC power supply 10 is rechargeable. Therefore, when the load 11 inputs DC power to the DC / DC converter 100, the DC power supply 10 is charged by that power. When the DC power supply 10 is charged by the power input from the load 11, the DC / DC converter 100 functions as a step-down converter. Hereinafter, the operation of the DC / DC converter 100 when supplying power from the load 11 to the DC power supply 10 is referred to as regeneration (or regenerative operation).

[0014] In this embodiment, for the sake of convenience, the connection terminal between the DC / DC converter 100 and the DC power source 10 is referred to as the input terminal, and the connection terminal between the DC / DC converter 100 and the load 11 is referred to as the output terminal, based on the power running operation. In addition, the voltage at the input terminal of the DC / DC converter 100 is referred to as the input voltage V IN The voltage at the output terminal of the DC / DC converter 100 is called the output voltage V OUT In this embodiment, the output voltage V OUT is applied.

[0015] The load 11 is an object to which the DC power supply 10 supplies power, and is, for example, a power train of an electric vehicle. In this embodiment, the load 11 is specifically configured by an inverter and an electric motor. The inverter converts DC power supplied from the DC power supply 10 via the DC / DC converter 100 into AC power. The electric motor is a drive source for the electric vehicle, and is driven by AC power supplied from the inverter. Furthermore, when the electric motor is driven by being rotated by the electric vehicle, the electric motor converts the kinetic energy of the electric vehicle into AC power (regenerative power) and inputs it to the inverter. At this time, the inverter converts the AC power input from the electric motor into DC power and inputs it to the DC / DC converter 100.

[0016] Hereinafter, the current output from the DC / DC converter 100 to the load 11, that is, the current flowing through the load 11, will be referred to as the load current I R The load current I R is an example of a parameter that represents the instantaneous output load. The load current I R The positive direction of the load current I R The negative direction of the load current I is the direction in which the DC current flows from the load 11 to the DC power supply 10 (DC / DC converter 100). In this embodiment, the DC current at the connection end of the DC / DC converter 100 and the inverter is R is.

[0017] Specifically, the DC / DC converter 100 includes an input-side capacitor 12, a reactor 13, a switch 14, and an output-side capacitor 15. In this embodiment, the DC / DC converter 100 is a so-called two-quadrant chopper circuit.

[0018] The input-side capacitor 12 is a capacitor provided at the input terminal and smoothes the power input and output between the DC power supply 10 and the DC / DC converter 100.

[0019] The reactor 13 is composed of an annular core 21 (magnetic core) and a coil 22 wound around the core 21.

[0020] The core 21 increases the inductance of the reactor 13. In this embodiment, the core 21 is made of a soft magnetic material. Therefore, the core 21 is magnetized when a current flows through the coil 22, and loses its magnetic force when the current stops flowing through the coil 22.

[0021] Furthermore, the core 21 has a gap 23. The gap 23 suppresses magnetic saturation of the core 21. In this embodiment, the gap 23 is formed by a magnet 24. That is, the reactor 13 is a so-called variable magnet reactor.

[0022] Magnet 24 is a permanent magnet that maintains magnetic force even when no current flows through coil 22. However, the magnetization direction of magnet 24 is reversible. In reactor 13, magnet 24 is magnetized in a direction that cancels out the magnetic field generated in core 21 when current flows through coil 22. In other words, the magnetization direction of magnet 24 is adjusted to be opposite to the magnetization direction of core 21. In this way, magnet 24 suppresses magnetic saturation of core 21.

[0023] The magnetization direction of the magnet 24 is reversed by a magnetization reversal current I L-rev It is controlled by passing the magnetization reversal current I L-rev is a current that is temporarily passed through the coil 22 to demagnetize and magnetize the magnet 24 and reverse the magnetization direction of the magnet 24. That is, when the magnetization direction of the magnet 24 is reversed, the reactor current I L is temporarily magnetization reversal current I L-rev The magnetization reversal current I L-rev The magnitude of is determined in advance based on the coercive force of the magnet 24 and the like.

[0024] Although there is one gap 23 in this embodiment, multiple gaps 23 can be provided in the core 21.

[0025] Hereinafter, the current flowing through the reactor 13 (coil 22) will be referred to as reactor current I LThe voltage at the reactor 13 is called the reactor voltage V L The reactor current I that flows during power running L is in the positive direction (forward direction), and the reactor current I that flows during regeneration L The direction of is negative (reverse).

[0026] The switch 14 controls the storage and release of energy in the reactor 13. In this embodiment, the switch 14 is configured by a first switch S1 (low-side switch) and a second switch S2 (high-side switch), which are so-called power semiconductor switching elements. The first switch S1 and the second switch S2 each include a channel 27 that is switched on (conducting) / off (non-conducting) depending on a voltage (hereinafter referred to as a gate voltage) applied to a gate electrode 26, and a freewheeling diode 28. The first switch S1 and the second switch S2 are configured by, for example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor).

[0027] The first switch S1 controls the storage and release of energy in the reactor 13 during powering operation. That is, the first switch S1 is controlled to be turned on / off when power is supplied from the DC power supply 10 to the load 11. During powering operation, the first switch S1 is turned on, causing energy to be stored in the reactor 13. Then, the first switch S1 is turned off, causing the energy stored in the reactor 13 to be released. The step-up ratio is determined by the duty ratio, which is the proportion of the time that the first switch S1 is on.

[0028] The second switch S2 controls the storage and release of energy in the reactor 13 during regenerative operation. That is, the second switch S2 is controlled to be turned on / off when power is supplied from the load 11 to the DC power supply 10. During regenerative operation, the second switch S2 is turned on, causing energy to be stored in the reactor 13. Then, the second switch S2 is turned off, causing the energy stored in the reactor 13 to be released. The step-down ratio is determined by the proportion of time that the second switch S2 is on (duty ratio).

[0029] In this embodiment, the first switch S1 and the second switch S2 are controlled to be turned on / off in an opposite (or complementary) manner. That is, when the first switch S1 is off, the second switch S2 is on, and when the first switch S1 is on, the second switch S2 is off. However, during powering operation, the second switch S2 can be kept off at all times. Also, during regenerative operation, the first switch S1 can be kept off at all times.

[0030] The output-side capacitor 15 is a capacitor provided at the output end. The output-side capacitor 15 smoothes the power input / output between the DC / DC converter 100 and the load. Hereinafter, the current in the output-side capacitor 15 will be referred to as the output-side capacitor current I C The voltage of the output capacitor 15 is called the output capacitor voltage V C Here, the direction of the output side capacitor current I C The direction in which the output capacitor 15 is charged is the output capacitor current I C is the positive direction.

[0031] The controller 16 is a control device that performs overall control of the system including the DC / DC converter 100, and is configured by, for example, one or more computers.

[0032] In this embodiment, the controller 16 controls the operation of the DC / DC converter 100 by switching the switch 14. That is, the controller 16 functions as a control device for the DC / DC converter 100. Specifically, the controller 16 sets duty command values Duty1 and Duty2 that control the duty ratios of the first switch S1 and the second switch S2, and controls the on / off of the first switch S1 and the second switch S2 based on these duty command values. In this way, the controller 16 operates the DC / DC converter 100 as a step-up converter or a step-down converter, and reverses the magnetization direction of the magnet 24 as necessary.

[0033] The controller 16 also functions as a control device that controls the operation of the load 11. That is, in this embodiment, the controller 16 controls the drive of the electric vehicle by controlling the power train, which is the load 11. More specifically, the controller 16 controls the electric motor by switching the inverter. In particular, the controller 16 controls the target load current I R The load current command value I R * Set the load current I R is the load current command value I R * The load 11 (inverter) is controlled to follow the load current command value I R * is set, for example, in accordance with the rotation speed of the electric motor, the depression amount of the accelerator pedal, etc.

[0034] The controller 16 can appropriately acquire currents, voltages, etc. at the respective parts of the DC / DC converter 100 and the load 11, which are the objects of control, using sensors (not shown). In this embodiment, the controller 16 controls the input voltage V IN , reactor current I L , reactor voltage V L , output capacitor current I C , output capacitor voltage V C , output voltage V OUT , and the load current I Rare detected as appropriate, and the DC / DC converter 100 and the load 11 can be controlled based on these detected values.

[0035] 2 is a block diagram showing the configuration of the controller 16 in the first embodiment. Here, the configuration related to control for determining the magnetization direction of the magnet 24 (hereinafter referred to as magnetization reversal control) is shown. As shown in FIG. 2, the controller 16 includes a reactor current command value calculation unit 31, a load current change determination unit 32, and a current feedback control unit 33.

[0036] The reactor current command value calculation unit 31 calculates a predetermined constant output voltage V OUT The output capacitor voltage V C Based on this, the target reactor current I L The basic reactor current command value I L * Set.

[0037] The load current change determination unit 32 determines the load current I R That is, the load current change determination unit 32 determines whether the polarity of the load current I R and the load current I R In this embodiment, the load current change determination unit 32 detects a change from negative to positive of the load current command value I R * Based on the load current I R For example, the load current change determination unit 32 determines whether the polarity of the load current command value I R * is compared with a predetermined threshold value, the load current I R Specifically, the polarity change of the load current command value I R * The absolute value of is greater than the threshold ε (|I R * |>ε) also changes from a large state to below the threshold ε (|I R * |≦ε), load current I R It can be determined that the polarity of

[0038] The load current command value I R * is the load current I R The actual load current I R Therefore, the load current change determination unit 32 of this embodiment determines the load current command value I R * Based on this, the resulting load current I R It predicts (estimates) polarity changes.

[0039] In principle, the current feedback control unit 33 controls the reactor current I L The detected value (hereinafter referred to as the reactor current detected value) is the basic reactor current command value I L * In this way, the duty command values Duty1 and Duty2 of the first switch S1 and the second switch S2 are set so as to follow the reactor current detection value (I L ) is the basic reactor current command value I L * The reactor current I L By controlling the output capacitor voltage V C is a predetermined target value (hereinafter referred to as the target output capacitor voltage V C * As a result, the output voltage V OUT will stabilize.

[0040] The load current change determination unit 32 detects the load current I R When it is determined that the polarity of the basic reactor current command value I L * Specifically, the duty command values Duty1 and Duty2 are set regardless of the load current I R When the polarity of the reactor current detection value (I L ) is the advance preparation current command value IL-cg * and magnetization reversal current command value I L-rev * The duty command values Duty1 and Duty2 are set so as to follow the above.

[0041] Preparatory current command value I L-cg * Before reversing the magnetization direction of the magnet 24, the output capacitor voltage V C The current that flows to raise the voltage in advance (hereinafter referred to as the preparatory current I L-cg ) is the reactor current I L The command value is set in the preparation current I L-cg (Preparation current command value I L-cg * ) is based on experiments or simulations, for example, the magnitude of the output capacitor voltage V C The reactor 13 is supplied with a pre-preparation current I L-cg When the DC power supply 10 supplies power, the output capacitor 15 is charged. L-cg Compared to before the flow, the output capacitor voltage V C As a result, the output voltage V OUT also rises.

[0042] Magnetization reversal current command value I L-rev * is a magnetization reversal current I that reverses the magnetization direction of the magnet 24 in the reactor 13. L-rev The magnetization reversal current command value I L-rev * (Magnetization reversal current I L-rev The magnitude of the magnetization reversal current I ) is determined in advance based on the coercive force of the magnet 24, etc. L-rev When the magnetization reversal current I flows in the reactor 13, the magnetization direction of the magnet 24 is reversed. L-rev When a current flows, the output capacitor voltage V C More specifically, the magnetization reversal current I L-rev When this is applied, the output capacitor voltage V CTherefore, in this embodiment, the output side capacitor voltage V C By increasing the voltage V in advance, the output capacitor voltage V generated when the magnetization of the magnet 24 is reversed can be reduced. C Suppress the decline in

[0043] That is, the current feedback control section 33 controls the load current I R In normal operation, the polarity of the reactor current detection value (I L ) is the basic reactor current command value I L * By making it follow the output capacitor voltage V C The target output capacitor voltage V C * And the load current I R When the polarity of the reactor current I changes, the current feedback control unit 33 L As a result, the current feedback control unit 33 temporarily changes the command value for the preparation current I L-cg The output capacitor voltage V C is first increased, and then the magnetization reversal current I L-rev The magnetization direction of the magnet 24 is reversed by

[0044] Below, before the magnetization reversal, the output capacitor voltage V C In order to increase the current in advance, a preparatory current I L-cg The period during which the cg In order to reverse the magnetization direction of the magnet 24, a magnetization reversal current I L-rev The period during which the current flows is called the magnetization reversal execution period P rev That's what they say.

[0045] 3 is a flowchart relating to the magnetization reversal control. As shown in FIG. 3, in step S10, the controller 16 controls the output capacitor voltage V C is the target output capacitor voltage V C *Specifically, the controller 16 controls the switch 14 so that the reactor current detection value (I L ) is the basic reactor current command value I L * By controlling the switch 14 so that it follows the output capacitor voltage V C is the target output capacitor voltage V C * Maintain it.

[0046] In step S11, the controller 16 controls the load current I R In this embodiment, the controller 16 determines whether the polarity of the load current command value I R * Based on the load current I R In step S11, the polarity change of the load current I R If it is determined that no polarity change occurs, the process returns to step S10, and the controller 16 C is the target output capacitor voltage V C * The reactor current I L Continue control of the

[0047] In step S11, the load current I R When a polarity change is detected, the process proceeds to step S12. In step S12, the controller 16 supplies the reactor 13 with the preparation current I L-cg By controlling the switch 14 so that C Increases.

[0048] Then, in step S13, the controller 16 controls the magnetization reversal current I L-rev In step S14, the controller 16 controls the switch 14 to start the current supply to the reactor. L ) is the magnetization reversal current I L-rev (Magnetization reversal current command value I L-rev * Check whether the reactor current detection value (IL ) is the magnetization reversal current I L-rev If it is equal to or less than the reactor current detection value (I L ) is the magnetization reversal current I L-rev The magnetization reversal current I L-rev continues to control the switch 14 that flows.

[0049] In step S14, the reactor current detection value (I L ) is the magnetization reversal current I L-rev When it is confirmed that the magnetization direction of the magnet 24 has been reversed and the current exceeds the limit, the process proceeds to step S15, and the controller 16 controls the reactor current I L That is, the controller 16 changes the polarity of the load current I R The basic reactor current command value I L * Change the polarity of the reactor current detection value (I L ) follows this. L The direction of the current switches from positive to negative or from negative to positive. This switching corresponds to switching between power running and regenerative operation.

[0050] FIG. 4 shows the output capacitor voltage V C 10 is a graph showing a typical change in load current I R When the polarity of the output capacitor voltage V C This is an example in which the magnetization direction of the magnet 24 is reversed without increasing the current.

[0051] 4A to 4D show comparative examples. Specifically, FIG. 4A shows the load current command value I R * 4(B) shows the transition of the reactor current I L 4(C) shows the transition of the reactor voltage V L 4(D) shows the transition of the output capacitor voltage V C The trend is shown below.

[0052] 4(E) to 4(H) show the first embodiment. Specifically, FIG. 4(E) shows the load current command value I R * 4(F) shows the transition of the reactor current I L 4(G) shows the transition of the reactor voltage V L 4(H) shows the transition of the output capacitor voltage V C The trend is shown below.

[0053] In Figure 4, as an example, the load current I R is positive, the load current I R 4 shows a scene in which the magnetization direction of the magnet 24 is reversed when the load current command value I R * At time t1, the magnetization reversal current I L-rev At time t2, the reversal of the magnetization direction of the magnet 24 is completed and the reactor current I L That is, the period from time t1 to time t2 is the magnetization reversal execution period P rev At time t3, the reactor current I L After changing the polarity of the reactor current I L This is the time when it stabilizes.

[0054] As shown in Fig. 4(A), the load current command value I R * changes from positive to negative. At this time, in the comparative example, as shown in FIG. 4(B), cg Without providing a magnetization reversal execution period P rev Therefore, as shown in Figure 4(C), the reactor voltage V L is the magnetization reversal execution period P rev After temporarily increasing at , it converges to zero, and then the reactor current I LThe polarity change causes a temporary drop before converging to zero.

[0055] As shown in FIG. 4(D), in the comparative example, the output capacitor voltage V C is the target output capacitor voltage V C * Then, from time t1, the magnetization reversal current I L-rev When the current flows, the output capacitor voltage V C However, the target output capacitor voltage V C * After that, the output capacitor voltage V C rises towards time t3 and again reaches the target output capacitor voltage V C * At this time, the output capacitor voltage V C is a lower limit value V that is predetermined to stably drive the load 11. C-LL Therefore, in the comparative example, the magnetization reversal current I L-rev At the timing when the magnetization direction of the magnet 24 is reversed, the output voltage V of the DC / DC converter 100 OUT may fluctuate beyond an allowable limit, resulting in the operation of the load 11 becoming unstable or the load 11 becoming unable to be driven.

[0056] As shown in FIG. 4(E), in the first embodiment, as in the comparative example, the load current command value I R * At this time, in the first embodiment, as shown in FIG. 4(F), the magnetization reversal execution period P rev Before that, there is a preparatory period P cg That is, in the first embodiment, at time t0, the load current I R When a polarity change is detected, the preparatory period P cg In the preliminary current I L-cg is controlled to flow in the reactor 13, and then, during the magnetization reversal execution period P rev In the magnetization reversal current I L-revis controlled to flow through the reactor 13. Therefore, as shown in FIG. 4(G), the reactor voltage V L is the advance preparation period P cg After temporarily rising, it converges to zero, and further, during the magnetization reversal execution period P rev After that, the reactor current I L The polarity change causes a temporary drop before converging to zero.

[0057] As shown in FIG. 4(H), in the first embodiment, the output capacitor voltage V C is the target output capacitor voltage V C * Then, from time t0, the preparatory current I L-cg When the current flows, the output capacitor voltage V C is the target output capacitor voltage V C * rises above, for example, V C * +δ[V]. Then, from time t1, the magnetization reversal current I L-rev When the current flows, the output capacitor voltage V C Then, at time t2, the magnetization reversal of the magnet 24 is completed, and the reactor current I L When the polarity of is changed, the output capacitor voltage V C decreases, and the target output capacitor voltage V C * converges to.

[0058] In this way, in the first embodiment, the advance preparation period P cg At the output capacitor voltage V C Therefore, the output capacitor voltage V C is the target output capacitor voltage V C * The output capacitor voltage V C is temporarily set to the target output capacitor voltage V C *Even if the target output capacitor voltage V C * Therefore, in the first embodiment, when the magnetization direction of the magnet 24 is reversed, the amount of decrease in the output capacitor voltage V C is the lower limit V C-LL The output voltage V of the DC / DC converter 100 never falls below OUT As a result, the load 11 can continue to operate stably.

[0059] [Second embodiment] In the first embodiment, the load current change determination unit 32 determines the load current command value I R * Based on the load current I R The load current change determination unit 32 predicts a polarity change of the load current command value I R * Instead of the load current I R (hereinafter referred to as the load current detection value) is used to calculate the load current I R In the second embodiment, the load current change determination unit 32 can directly determine (detect) the polarity change of the load current detection value (I R ) based on the load current I R The circuit configuration of the DC / DC converter 100 is the same as that of the first embodiment. In this embodiment, the load current change determination unit 32 determines, for example, the load current detection value (I R ) with a predetermined threshold value, the load current I R In this way, the polarity change of the load current detection value (I R ) to calculate the load current I R When detecting a polarity change of the output capacitor voltage V C The timing at which these changes occur varies.

[0060] FIG. 5 shows the output capacitor voltage V C5(A) to 5(D) are graphs showing the transition of the load current command value I R * , reactor current I L , reactor voltage V L , and the output capacitor voltage V C The trend is shown below.

[0061] In addition, in Figure 5, as an example, the load current I R is positive, the load current I R 5 shows a scene in which the magnetization direction of the magnet 24 is reversed when the load current I R begins to decrease, and the load current change determination unit 32 detects this, and the advance preparation current I L-cg At time t2, charging of the output side capacitor 15 for preparation is completed, and the magnetization reversal current I L-rev At time t3, the reversal of the magnetization direction of the magnet 24 is completed and the reactor current I L At time t4, the polarity of the reactor current I L After changing the polarity of the reactor current I L Therefore, in FIG. 5, the period from time t1 to time t2 is the advance preparation period P cg The period from time t2 to time t3 is the magnetization reversal execution period P rev is.

[0062] As shown in FIG. 5A, in the second embodiment, at time t1, the load current I R When the load current actually changes to a positive or negative value, the load current change determination unit 32 detects this. Therefore, as shown in FIG. 5B, during the advance preparation period P cg In the preliminary current I L-cg is controlled to flow in the reactor 13, and then, during the magnetization reversal execution period P rev In the magnetization reversal current I L-revis controlled to flow through the reactor 13. At this time, as shown in FIG. 5(C), the reactor voltage V L is the advance preparation period P cg After temporarily rising, it converges to zero, and further, during the magnetization reversal execution period P rev After that, the reactor voltage V L is the reactor current I at time t3 L The polarity change causes a temporary drop, and then converges to zero around time t4.

[0063] As shown in FIG. 5(D), in the second embodiment, the output capacitor voltage V C is the target output capacitor voltage V C * Then, from time t1, the preparatory current I L-cg When the current flows, the output capacitor voltage V C is the target output capacitor voltage V C * rises above, for example, V C * +δ. Then, from time t2, the magnetization reversal current I L-rev When the current flows, the output capacitor voltage V C Then, at time t3, the magnetization reversal of the magnet 24 is completed, and the reactor current I L When the polarity of is changed, the output capacitor voltage V C decreases, and the target output capacitor voltage V C * converges to.

[0064] In this way, in the second embodiment, the advance preparation period P cg At the output capacitor voltage V C Therefore, the output capacitor voltage V C is the target output capacitor voltage V C * The output capacitor voltage V Cis temporarily set to the target output capacitor voltage V C * Even if the target output capacitor voltage V C * Therefore, in the second embodiment, as in the first embodiment, when the magnetization direction of the magnet 24 is reversed, the output side capacitor voltage V C is the lower limit V C-LL The output voltage V of the DC / DC converter 100 never falls below OUT As a result, the load 11 can continue to operate stably.

[0065] [Variations] In the first and second embodiments, the load current change determination unit 32 determines the load current command value I R * or load current detection value (I R ) based on the load current I R The polarity change of the polarity change may be predicted or measured, but is not limited to this.

[0066] The load current change determination unit 32 determines the output side capacitor voltage V C , and the output capacitor current I C Based on these, the load current I R In this case, the load current change determination unit 32 can calculate (estimate) the calculated load current I R Based on this, the actual load current I R The polarity change can be determined.

[0067] Furthermore, the load current change determination unit 32 determines, for example, the input voltage V IN , reactor current I L , and the output voltage V OUT The output voltage V OUT and the output voltage V OUT The difference between the detected value of and ΔV OUT is the load current I RTherefore, the load current change determination unit 32 determines whether the output voltage V OUT and outputs the output voltage V OUT Calculates the output voltage V OUT The difference between the detected value and the calculated value ΔV OUT Based on the load current I R The polarity change can be determined.

[0068] [Third embodiment] In the first and second embodiments, the load current I R When it is determined that the polarity of the reactor current is changed, the current feedback control unit 33 outputs the reactor current detection value (I L ) is the command value to be followed by the basic reactor current command value I L * From the above, the advance preparation current command value I L-cg * and magnetization reversal current command value I L-rev * , and the controller 16 supplies the reactor 13 with a preparatory current I L-cg and magnetization reversal current I L-rev However, in this way, the reactor current I L By a method other than adjusting the command value in the feedback control of L-cg and magnetization reversal current I L-rev In the third embodiment, as an example, a preparatory current I L-cg and magnetization reversal current I L-rev A method for more directly setting the duty command values Duty1 and Duty2 when flowing will be described.

[0069] Fig. 6 is a block diagram showing the configuration of the controller 16 in the third embodiment. As shown in Fig. 6, the controller 16 in the third embodiment includes a reactor current command value calculation unit 31, a load current change determination unit 32, and a current feedback control unit 33, as well as a selection unit 34.

[0070] The reactor current command value calculation unit 31, the load current change determination unit 32, and the current feedback control unit 33 are configured in the same manner as in the first embodiment, the second embodiment, or their modified examples. Here, as an example, they are configured in the same manner as in the first embodiment. However, the load current change determination unit 32 is configured in the same manner as in the first embodiment. R The result of the determination regarding the polarity change of the load current I is input to the selection unit 34, and the current feedback control unit 33 R Regardless of the polarity change of the basic reactor current command value I L * A duty command value corresponding to the above is calculated and output.

[0071] The selection unit 34 selects the load current I R Depending on whether the polarity of the load current I R In normal operation, the polarity of the current feedback control unit 33 does not change. L * The duty command values set based on the above are output to the switch 14 as the final duty command values Duty1 and Duty2.

[0072] On the other hand, the load current I R When a polarity change is detected, the selector 34 selects the reactor voltage V to be applied to the reactor 13 (coil 22). L and time (hereinafter referred to as voltage-time product), are output to the switch 14 as the final duty command values Duty1 and Duty2. R When a polarity change is detected, the selector 34 outputs duty command values Duty1 and Duty2 that realize the voltage-time product for advance preparation, and then outputs duty command values Duty1 and Duty2 that realize the voltage-time product for magnetization reversal.

[0073] The voltage-time product for preparation is the preparation current I L-cg The output capacitor voltage V CThe constant reactor voltage V required to raise L and time, and based on experiments or simulations, for example, the output capacitor voltage V C The voltage-time product for magnetization reversal is determined in advance according to the magnetization reversal current I L-rev The reactor voltage V that should be applied when reversing the magnetization of the magnet 24 is the same as when L and time, and is determined in advance based on the coercive force of the magnet 24, etc.

[0074] As shown above, the reactor current I L The preparatory current I L-cg and magnetization reversal current I L-rev Even when duty command values Duty1 and Duty2 determined by the voltage-time product are used instead of flowing the reactor current I, the same effects as those of the first and second embodiments can be obtained. L and reactor voltage V L changes as follows:

[0075] FIG. 7 shows the output capacitor voltage V C 7(A) to 7(D) are graphs showing the transition of the load current command value I R * , reactor current I L , reactor voltage V L , and the output capacitor voltage V C The trend is shown below.

[0076] In addition, in FIG. 7, as an example, the load current I R is positive, the load current I R 2 shows a scene in which the magnetization direction of the magnet 24 is reversed in response to switching to a regenerative operation in which the load current command value I R * Based on the load current I R Therefore, in FIG. 4, at time t0, the load current command value IR * At time t1, the magnetization reversal current I L-rev At time t2, the reversal of the magnetization direction of the magnet 24 is completed and the reactor current I L That is, the period from time t1 to time t2 is the magnetization reversal execution period P rev At time t3, the reactor current I L After changing the polarity of the reactor current I L This is the time when it stabilizes.

[0077] As shown in FIG. 7A, in the third embodiment, the load current command value I R * When the load current change determination unit 32 detects that the load current change has started to decrease, the load current change determination unit 32 detects that the load current change has started to decrease. cg In the preliminary current I L-cg is controlled to flow in the reactor 13, and then, during the magnetization reversal execution period P rev In the magnetization reversal current I L-rev is controlled to flow through the reactor 13. However, in the third embodiment, the advance preparation current I L-cg and magnetization reversal current I L-rev is determined by the voltage-time product. Therefore, as shown in FIG. 7(C), the reactor voltage VL is cg and magnetization reversal execution period P rev As a result, the pre-conditioning current I L-cg and magnetization reversal current I L-rev As shown in FIG. 7(B), the current has a constant slope (constant increase) over time.

[0078] As shown in Figure 7(D), until time t0, the output capacitor voltage V C is the target output capacitor voltage V C * Then, from time t0, the preparatory current IL-cg When the current flows, the output capacitor voltage V C is the target output capacitor voltage V C * rises above, for example, V C * +δ. Then, from time t1, the magnetization reversal current I L-rev When the current flows, the output capacitor voltage V C Then, at time t2, the magnetization reversal of the magnet 24 is completed, and the reactor current I L When the polarity of is changed, the output capacitor voltage V C decreases, and the target output capacitor voltage V C * converges to.

[0079] That is, in the third embodiment, the advance preparation period P cg At the output capacitor voltage V C Therefore, the output capacitor voltage V C is the target output capacitor voltage V C * The output capacitor voltage V C is temporarily set to the target output capacitor voltage V C * Even if the target output capacitor voltage V C * Therefore, in the first embodiment, when the magnetization direction of the magnet 24 is reversed, the amount of decrease in the output capacitor voltage V C is the lower limit V C-LL The output voltage V of the DC / DC converter 100 never falls below OUT As a result, the load 11 can continue to operate stably.

[0080] [Fourth embodiment] In the first to third embodiments and the modified examples, the output voltage V OUTIn the above example, the output voltage V is stabilized, but the present invention is not limited to this. In the case where the magnetization direction of the magnet 24 is reversed when switching from regenerative operation to power running operation, the output voltage V can be stabilized by the methods of the first to third embodiments and the modified examples. OUT In the fourth embodiment, a scene in which the magnetization direction of the magnet 24 is reversed when switching from regenerative operation to power running operation will be described below. Here, it is assumed that the configuration of the controller 16 is the same as that in the first embodiment.

[0081] 8 is a graph showing the transition of the output capacitor voltage and the like in the magnetization reversal control of the comparative example and the fourth embodiment. R When the polarity of the output capacitor voltage V C This is an example in which the magnetization direction of the magnet 24 is reversed without increasing the current.

[0082] 8(A) to 8(D) show the load current command value I R * , reactor current I L , output capacitor voltage V C , and the output capacitor current I C 8(E) to 8(H) show the transition of the load current command value I in this embodiment when switching from regenerative operation to powering operation. R * , reactor current I L , output capacitor voltage V C , and the output capacitor current I C In FIG. 8, at time t0, the load current command value I R * At time t1, the magnetization reversal current I L-rev At time t2, the reversal of the magnetization direction of the magnet 24 is completed and the reactor current I L That is, the period from time t1 to time t2 is the magnetization reversal execution period P revAt time t3, the reactor current I L After changing the polarity of the reactor current I L This is the time when it stabilizes.

[0083] As shown in Fig. 8(A), the load current command value I R * changes from negative to positive. At this time, in the comparative example, as shown in FIG. 8(B), cg Without providing a magnetization reversal execution period P rev At this time, as shown in FIG. 8(D), the magnetization reversal execution period P rev The negative magnetization reversal current I flows through the reactor 13 at L-rev is the output capacitor current I from the output capacitor 15 C Therefore, as shown in Figure 8(C), the output capacitor voltage V C is the magnetization reversal execution period P rev , and then recovers due to the power supplied from the load 11. Therefore, in the comparative example, the magnetization reversal current I L-rev flows, and at the timing when the magnetization direction of the magnet 24 is reversed, the output side capacitor voltage V C is the lower limit V C-LL and the output voltage V OUT As a result, in the comparative example, the operation of the load 11 may become unstable or the load 11 may become unable to be driven, similarly to when the operation is shifted from the powering operation to the regenerative operation, when the operation is shifted from the regenerative operation to the powering operation.

[0084] As shown in FIG. 8(E), in this embodiment, as in the comparative example, the load current command value I R * However, in this embodiment, as shown in FIG. 8(F), during the magnetization reversal execution period P rev Before that, there is a preparatory period P cg In this case, the scene is shifting from regenerative operation to power running, so a preparatory period P cgIn this state, both the first switch S1 and the second switch S2 are temporarily turned off. As a result, as shown in FIG. 8(F), the reactor current I L On the other hand, as shown in FIG. 8(H), the power supplied from the load 11 causes the advance preparation period P cg The output capacitor current I C becomes positive, and the output capacitor 15 is charged. As a result, the output capacitor voltage V C is the target output capacitor voltage V C * rises above, for example, V C * It becomes +δ.

[0085] Then, during the magnetization reversal execution period P rev As shown in Figure 8(F), a negative magnetization reversal current I L-rev is controlled to flow through the reactor 13. This negative magnetization reversal current I L-rev is supplied from the output side capacitor 15, so as shown in FIG. 8(H), the output side capacitor current I C becomes negative, and the output capacitor voltage V C However, in this embodiment, the advance preparation period P cg The output capacitor 15 is charged at the output side, and the output capacitor voltage V C Since is rising, the magnetization reversal execution period P rev At the output capacitor voltage V C Even if the output capacitor voltage V C is the target output capacitor voltage V C * The output capacitor voltage V C * Even if the target output capacitor voltage V C * Therefore, in this embodiment, when the magnetization direction of the magnet 24 is reversed, the amount of reduction in the output capacitor voltage V C is the lower limit VC-LL The output voltage V of the DC / DC converter 100 never falls below OUT As a result, the load 11 can continue to operate stably.

[0086] Here, a scene in which the regenerative operation is shifted to the power running operation in a configuration similar to that of the first embodiment has been described, but the same applies to a configuration similar to that of the second embodiment or the modified example.

[0087] [Fifth embodiment] In the first to fourth embodiments and the modified examples, the load current I R In the fifth embodiment, the controller 16 controls the DC / DC converter 100 in accordance with the change in polarity of the magnet 24, but the controller 16 also controls the load 11 in addition to the DC / DC converter 100. Therefore, when the magnetization direction of the magnet 24 in the DC / DC converter 100 is reversed, the controller 16 can adjust the operation of the load 11 accordingly. In the fifth embodiment, as in the first embodiment, the load current command value I R * Based on the load current I R When the magnetization direction of the magnet 24 is reversed, the actual load current I R The control for delaying the polarity change will be described.

[0088] Fig. 9 is a block diagram showing the configuration of the controller 16 in the fifth embodiment. As shown in Fig. 9, the controller 16 in the fifth embodiment includes a reactor current command value calculation unit 31, a load current change determination unit 32, and a current feedback control unit 33, as well as a delay control unit 35. Here, the reactor current command value calculation unit 31, the load current change determination unit 32, and the current feedback control unit 33 are configured in the same manner as in the fourth embodiment (first embodiment).

[0089] The delay control unit 35 determines whether the load current change determination unit 32 determines the load current command value I R * Based on the load current I RWhen a polarity change of the load current command value I is detected predictively, the delay control unit 35 adjusts the control of the load 11 (for example, an inverter). R * The actual load current I R Specifically, the delay control unit 35 delays the change of the cg For a period of time equivalent to the load current I R In this embodiment, the delay control unit 35 adjusts the control of the load 11 so that the actual change in the load 11 is delayed during the advance preparation period P cg and magnetization reversal execution period P rev The load current I R The control of the load 11 is adjusted so that the actual change in

[0090] FIG. 10 shows the output capacitor voltage V C 10A to 10D are graphs showing the load current command value I R * , reactor current I L , output capacitor voltage V C , and the output capacitor current I C In FIG. 10, the load current command value I R * At time t1, the magnetization reversal current I L-rev At time t2, the reversal of the magnetization direction of the magnet 24 is completed and the reactor current I L That is, the period from time t1 to time t2 is the magnetization reversal execution period P rev At time t3, the reactor current I L After changing the polarity of the reactor current I L In FIG. 10(A), the load current command value I R* is shown by a solid line, and the actual load current I R is shown by a dashed dotted line.

[0091] As shown in FIG. 10(A), the load current command value I R * changes from negative to positive. At this time, as shown in FIG. 10(B) to FIG. 10(D), during the advance preparation period P cg and magnetization reversal execution period P rev Reactor current I L , output capacitor voltage V C , and the output capacitor current I C The transition is the same as in the fourth embodiment (FIGS. 8(F) to 8(H)).

[0092] However, in this embodiment, the load current command value I R * When the load current change determination unit 32 detects this, the delay control unit 35 adjusts the control of the load 11 (inverter) to decrease the actual load current I as shown by the dashed line. R Therefore, the advance preparation period P cg Charging of the output side capacitor 15 and magnetization reversal execution period P rev The magnetization reversal current I using the power of the output capacitor 15 L-rev The current flow is the actual load current I R is negative, and during steady regenerative operation, the actual load current I R Therefore, as shown above, the load current I R By delaying the output voltage V OUT This makes it particularly easy to suppress changes in

[0093] Note that, here, a scene in which the vehicle shifts from regenerative operation to power running operation has been described, as in the fourth embodiment, but the same applies to a scene in which the vehicle shifts from power running operation to regenerative operation, as in the first or third embodiment.

[0094] [Sixth embodiment] In the first to fifth embodiments and the modified examples, the advance preparation period P cg The output capacitor voltage V C The amount of rise (δ) of the preparatory current I L-cg Alternatively, it is determined by the corresponding voltage-time product. However, the magnetization reversal execution period P rev The output capacitor voltage V C The decrease in the magnetization reversal current (δ) is L-rev The output capacitor voltage V before the current flows C (Hereinafter, the initial voltage V C-ini That is, the output voltage V OUT In order to suppress the downward fluctuation (drop) of cg The initial voltage V of the output capacitor 15 C-ini (=V C * +δ) can be determined by calculation as follows:

[0095] FIG. 11 shows the initial voltage V of the output capacitor 15. C-ini and the output capacitor voltage V C 11 is a graph showing a relationship between the initial voltage V C-ini The higher the magnetization reversal current I L-rev When current flows, the output capacitor voltage V C The decrease in the initial voltage V C-ini The smaller is the magnetization reversal current I L-rev When current flows, the output capacitor voltage V C The decrease in (δ) becomes larger.

[0096] More specifically, the output voltage V OUT In order to suppress the downward fluctuation (drop) of cg The initial voltage V of the output capacitor 15 C-ini (=V C *+δ) is expressed by the following equation (1): The controller 16 controls the preparatory current I L-cg Alternatively, the corresponding voltage-time product can be determined. OUT * ” is the output voltage V that the DC / DC converter 100 should maintain. OUT (output voltage target value). "E" is the energy required to demagnetize or magnetize magnet 24, and "2E" is the energy required to reverse the magnetization direction of magnet 24. Also, "C" is the capacitance of output capacitor 15.

[0097]

number

[0098] According to equation (1), the magnetization reversal execution period P rev The output capacitor voltage V C Therefore, the controller 16 can calculate the amount of decrease (δ) in the magnetization reversal execution period P rev The output capacitor voltage V C Depending on the amount of decrease (δ), the advance preparation period P cg The output capacitor voltage V C The amount of increase (δ) can be determined.

[0099] The controller 16 also controls the magnetization reversal execution period P rev The output capacitor voltage V C The decrease in the amount of (δ) and the lower limit V C-LL By comparing with the above, when the magnetization direction of the magnet 24 is reversed, the preparatory period P cg Set the output capacitor voltage V C It can be determined whether or not the value should be increased.

[0100] For example, the magnetization reversal execution period P rev The output capacitor voltage V C (=V C * -δ) is the lower limit VC-LL When it is below (V C =V C * -δ <V C-LL ), the controller 16 performs the advance preparation period P cg Set the initial voltage V C-ini It can be determined that the magnetization reversal execution period P rev The output capacitor voltage V C (=V C * -δ) is the lower limit V C-LL When it is equal to or greater than (V C =V C * -δ ≥ V C-LL ), the controller 16 performs the advance preparation period P cg Set the initial voltage V C-ini It can be determined that the magnetization direction of the magnet 24 can be reversed without increasing the

[0101] Figure 12 shows the initial voltage V C-ini As shown by the dashed line in FIG. rev Before that, the output capacitor voltage V C is the target output capacitor voltage V C * However, the target output capacitor voltage V C * can change due to, for example, a decrease in the remaining capacity of the DC power supply 10 due to power consumption in the load 11. Therefore, when the magnetization direction of the magnet 24 is reversed, the output side capacitor voltage V C (=V C * -δ) is the lower limit V C-LL There are also scenes where the lower limit V C-LL There are also scenes where the value is maintained above this.

[0102] Therefore, the controller 16 can be configured as follows: That is, the controller 16 calculates the output capacitor voltage V when the magnetization direction of the magnet 24 is reversed based on the equation (1). C (=VC * -δ) is calculated, and the value is the lower limit V C-LL Then, it is determined whether the output capacitor voltage V C (=V C * -δ) is the lower limit V C-LL When it is determined that the time is less than the predetermined time, the controller 16 starts the advance preparation period P cg As shown by the solid line in FIG. 12, the initial voltage V of the output capacitor 15 C-ini V C * It can be increased to a value of +δ or higher.

[0103] In this way, the voltage fluctuation of the output side capacitor 15 when the magnetization direction of the magnet 24 is reversed is estimated, and the output side capacitor voltage V C is the lower limit V C-LL When the temperature falls below 100°C, the preparation period P cg By setting the output capacitor voltage V C If the output voltage V OUT In addition, it is particularly easy to effectively suppress fluctuations in the preparation period P cg The output capacitor voltage V after the rise C (Initial voltage V C-ini ) according to equation (1), the output capacitor voltage V C increases, and the output voltage V OUT Fluctuations in the temperature can be suppressed.

[0104] As described above, the control method for the DC / DC converter according to the first to sixth embodiments and modifications (hereinafter referred to as the above embodiments, etc.) is a control method for the DC / DC converter 100 having the reactor 13, the switch 14 that controls the storage and release of energy in the reactor 13, and the output-side capacitor 15 provided at the output end connected to the load 11, the reactor 13 being configured by the core 21 in which the gap 23 is formed by the magnet 24 whose magnetization direction can be reversed, and the coil 22 wound around the core 21. In this control method, the load current I R Then, determine whether the polarity of the load current I R When the polarity of the output capacitor 15 changes, the voltage (V C ) and the voltage (V C ) is increased, a magnetization reversal current I is supplied to the coil 22 to reverse the magnetization direction of the magnet 24. L-rev Flush.

[0105] Thus, the load current I R When the magnetization direction of the magnet 24 is reversed in response to the polarity change of the output capacitor voltage V C The target output capacitor voltage V C * The output capacitor voltage V C When the magnetization reversal current I L-rev When the magnetization reversal current I L-rev The output voltage V OUT That is, in the DC / DC converter 100 using the variable magnetic reactor (13), the fluctuation (downward fluctuation) of the output voltage V that occurs when the magnetization direction of the magnet 24 is reversed can be suppressed. OUT Fluctuations in the

[0106] In the control method of the DC / DC converter according to the above-described embodiments, the load current I R The load current command value I R * and obtain the load current command value I R *Based on the load current I R Determine the change in polarity of

[0107] In this way, the load current command value I R * Based on the load current I R By predicting the polarity change of the load current I R Before the change occurs, the output capacitor voltage V C Increasing the load current command value I R * Based on the load current I R By predicting the polarity change of the output capacitor voltage V C When increasing the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature are particularly likely to be suppressed.

[0108] In the control method for the DC / DC converter according to the above-described embodiments (particularly the second embodiment), the load current I R The load current detection value (I R ) and calculates the load current I R Determine the change in polarity of

[0109] In this way, the load current detection value (I R ) polarity change is detected and the output capacitor voltage V C Even if the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT The fluctuation of the load current detection value (I R ) changes polarity at the same time as the output capacitor voltage V C By increasing the magnetic flux density, the time during which the direction of the magnetic flux generated by the coil 22 coincides with the direction of the magnetic flux generated by the magnet 24 is reduced. This makes it easier to suppress magnetic saturation of the core 21.

[0110] In the control method of the DC / DC converter according to the above-described embodiments (especially the modified examples), the voltage (V C ) and current (I C ), and detects the voltage of the output capacitor 15 (V C ) and current (I C ) based on the load current I R Then, the calculated load current I R Determine the change in polarity of

[0111] In this way, the output capacitor voltage V C and the output capacitor current I C According to the load current I R (instantaneous output load) can be accurately calculated. L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the σ are particularly likely to be suppressed accurately.

[0112] In the control method of the DC / DC converter according to the above-described embodiments (especially the modified examples), the input voltage V IN , the reactor current I which is the current flowing through the coil 22 L , and the duty ratio of the switch 14, the output voltage V OUT Calculates the output voltage V OUT The difference between the detected value and the calculated value ΔV OUT Based on the load current I R Determine the change in polarity of

[0113] Thus, the output voltage V OUT The difference between the detected value and the calculated value ΔV OUT Based on the load current I R By determining the change in polarity of the load current I, the load current I can be measured without adding any special current or voltage sensors other than those normally used in the DC / DC converter 100. RTherefore, the present invention can be implemented while keeping costs down.

[0114] In the control method of the DC / DC converter according to the above-described embodiments, the reactor current I L The output capacitor voltage V C Detects the output capacitor voltage V C Based on this, the reactor current I L The reactor current command value (I L * ) is calculated. Then, during normal operation when the magnetization direction of the magnet 24 is maintained, the reactor current I L This reactor current command value (I L * On the other hand, when the magnetization direction of the magnet 24 is to be reversed, the reactor current command value (I L * ), the voltage (V C ) rises, the magnetization reversal current I flows through the coil 22. L-rev The switch 14 is opened and closed to allow the flow of

[0115] In this way, when reversing the magnetization direction of the magnet 24, the required reactor current I is generated by current feedback without going through a voltage feedback loop. L (Preparation current I L-cg and magnetization reversal current I L-rev ) is commanded, the reactor current I L quickly to the target value (I L-cg and I L-rev ) can be made to follow the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature are particularly likely to be suppressed.

[0116] In the control method of the DC / DC converter according to the above-described embodiments (particularly the third embodiment), the reactor current I L The output capacitor voltage (V C ) and detects the output capacitor voltage V C Based on this, the reactor current I L The reactor current command value (I L * ) is calculated. Then, during normal operation when the magnetization direction of the magnet 24 is maintained, the reactor current I L This reactor current command value (I L * On the other hand, when the magnetization direction of the magnet 24 is to be reversed, the switch 14 is opened and closed in accordance with a predetermined voltage-time product.

[0117] In this way, when reversing the magnetization direction of the magnet 24, if the duty ratio is directly commanded by the voltage-time product without using the current feedback loop, the reactor current I L quickly to the target value (I L-cg and I L-rev ) can be made to follow the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature are particularly likely to be suppressed.

[0118] In the control method of the DC / DC converter according to the above-described embodiments, the load current I R When the polarity of the input terminal of the DC power supply 10 changes from positive to negative, the voltage (V C ) to increase.

[0119] Thus, the load current I R When the polarity of changes from positive (power running) to negative (regenerative operation), the magnetization reversal current I L-rev Before the power is supplied, the output capacitor voltage V CIt is preferable to increase the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature are particularly likely to be suppressed.

[0120] In the control method of the DC / DC converter according to the above-described embodiments, the load current I R When the polarity of changes from negative to positive, the voltage (V C ) to increase.

[0121] Thus, the load current I R When the polarity of changes from negative (regenerative operation) to positive (power operation), the magnetization reversal current I L-rev Before the power is supplied, the output capacitor voltage V C It is preferable to increase the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature are particularly likely to be suppressed.

[0122] In the control method for the DC / DC converter according to the above-described embodiments (especially the fifth embodiment), the load current command value I R * Based on the load current I R If it is determined that the polarity of the load current I R delays the change in the load current I R Before the polarity of the output capacitor 15 changes, the voltage (V C ) to increase.

[0123] In this way, the load current command value I R * Based on the load current I R When predicting the polarity change of the load current I RThe change in the load current command value I R * By delaying the load current I R Before the polarity of V actually changes, the output capacitor voltage V C Therefore, the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature are particularly likely to be suppressed.

[0124] In the control method of the DC / DC converter according to the above-described embodiments (especially the sixth embodiment), the voltage (V C ) based on the magnetization reversal current I L-rev The voltage fluctuation (δ) of the output capacitor 15 that occurs when current flows is estimated, and the voltage (V C ) is the predetermined lower limit V C-LL Then, it is determined whether the load current I R The polarity of the voltage of the output capacitor 15 (V C ) is the lower limit V C-LL When the voltage of the output capacitor 15 (V C ) to increase.

[0125] Thus, the magnetization reversal current I L-rev When current flows, the output capacitor voltage V C is the lower limit V C-LL It is determined whether the output capacitor voltage V C When the output capacitor voltage V C If we keep increasing the output voltage V OUT In situations where fluctuations in the output voltage V OUT fluctuations can be suppressed.

[0126] In the control method for the DC / DC converter according to the above-described embodiments (especially the sixth embodiment), the output voltage V OUT The target value of (V OUT* ), the energy required for magnetization reversal (2E), and the capacitance (C) of the output capacitor 15, the voltage (V C-ini =V C * +δ).

[0127] Thus, based on the above equation (1), the initial voltage V C-ini If we define cg In this case, the output capacitor voltage V C Therefore, the magnetization reversal current I L-rev The output capacitor voltage V C and the resulting fluctuations in the output voltage V OUT Fluctuations in the temperature range are particularly likely to be suppressed reliably.

[0128] The control device for a DC / DC converter according to the above-described embodiments is a control device (controller 16) for a DC / DC converter that controls, by opening and closing the switch 14, a DC / DC converter 100 that includes a reactor 13, a switch 14 that controls the storage and release of energy in the reactor 13, and an output-side capacitor 15 that is provided at the output end that is connected to a load 11, and in which the reactor 13 is configured with a core 21 in which a gap 23 is formed by a magnet 24 whose magnetization direction can be reversed, and a coil 22 that is wound around the core 21. This control device (controller 16) controls a load current I R The load current change determination unit 32 determines whether the polarity of the load current I R When it is determined that the polarity of the output capacitor 15 changes, C ) rises, and the voltage (V C ) is increased, a magnetization reversal current I is supplied to the coil 22 to reverse the magnetization direction of the magnet 24. L-rev The switch 14 is opened and closed so that the current flows.

[0129] Thus, the load current I RWhen the magnetization direction of the magnet 24 is reversed in response to the polarity change of the output capacitor voltage V C The target output capacitor voltage V C * The output capacitor voltage V C When the magnetization reversal current I L-rev When the magnetization reversal current I L-rev The output voltage V OUT That is, in the DC / DC converter 100 using the variable magnetic reactor (13), the fluctuation (downward fluctuation) of the output voltage V that occurs when the magnetization direction of the magnet 24 is reversed can be suppressed. OUT Fluctuations in the

[0130] Although the embodiments of the present invention have been described above, the configurations described in the above embodiments merely illustrate some of the application examples of the present invention and are not intended to limit the technical scope of the present invention. For example, in the above embodiments, the DC / DC converter 100 is configured as a two-quadrant chopper circuit, but this is not limiting. The present invention is also suitable when the DC / DC converter 100 is configured as a so-called four-quadrant chopper circuit. [Explanation of symbols]

[0131] 10: DC power supply, 11: load, 12: input side capacitor, 13: reactor, 14: switch, 15: output side capacitor, 16: controller, 21: core, 22: coil, 23: gap, 24: magnet, 26: gate electrode, 27: channel, 28: freewheel diode, 31: reactor current command value calculation unit, 32: load current change determination unit, 33: current feedback control unit, 34: selection unit, 35: delay control unit, 100: DC / DC converter

Claims

1. A control method for a DC / DC converter having a reactor, a switch that controls storage and release of energy in the reactor, and an output-side capacitor provided at an output end that connects to a load, wherein the reactor is configured by a core in which a gap is formed by a magnet whose magnetization direction is reversible, and a coil wound around the core, determining whether or not the polarity of a load current, which is a current output to the load, changes; When the polarity of the load current changes, increasing the voltage of the output capacitor; With the voltage of the output capacitor increased, a magnetization reversal current that reverses the magnetization direction of the magnet is passed through the coil. A method for controlling a DC / DC converter.

2. 2. A method for controlling a DC / DC converter according to claim 1, comprising: A load current command value that is a control target of the load current is obtained; determining a change in polarity of the load current based on the load current command value; A method for controlling a DC / DC converter.

3. 2. A method for controlling a DC / DC converter according to claim 1, comprising: A load current detection value is acquired, which is a detection value of the load current. determining a change in polarity of the load current based on the detected load current value; A method for controlling a DC / DC converter.

4. 2. A method for controlling a DC / DC converter according to claim 1, comprising: Detecting the voltage and current of the output capacitor; calculating the load current based on the voltage and current of the output-side capacitor; determining a change in polarity of the calculated load current; A method for controlling a DC / DC converter.

5. 2. A method for controlling a DC / DC converter according to claim 1, comprising: An output voltage is calculated based on an input voltage, which is a voltage at an input terminal connected to a DC power supply, a reactor current, which is a current flowing through the coil, and a duty ratio of the switch; determining a change in polarity of the load current based on a difference between the detected value and the calculated value of the output voltage; A method for controlling a DC / DC converter.

6. A control method for a DC / DC converter according to any one of claims 1 to 5, Detecting a reactor current that is a current flowing through the coil; Detecting an output capacitor voltage, which is the voltage of the output capacitor; calculating a reactor current command value that is a command value for the reactor current based on the output-side capacitor voltage; During normal operation in which the magnetization direction of the magnet is maintained, the switch is opened and closed so that the reactor current follows the reactor current command value; When reversing the magnetization direction of the magnet, the reactor current command value is changed, and the switch is opened and closed so that the magnetization reversal current flows through the coil in a state where the voltage of the output-side capacitor is increased. A method for controlling a DC / DC converter.

7. A method for controlling a DC / DC converter according to any one of claims 1 to 5, comprising: Detecting a reactor current that is a current flowing through the coil; Detecting an output capacitor voltage, which is the voltage of the output capacitor; calculating a reactor current command value that is a command value for the reactor current based on the output-side capacitor voltage; During normal operation in which the magnetization direction of the magnet is maintained, the switch is opened and closed so that the reactor current follows the reactor current command value; When reversing the magnetization direction of the magnet, the switch is opened and closed in accordance with a predetermined voltage-time product. A method for controlling a DC / DC converter.

8. A method for controlling a DC / DC converter according to any one of claims 1 to 5, comprising: When the polarity of the load current changes from positive to negative, the voltage of the output-side capacitor is increased by power supplied from a DC power supply connected to the input terminal. A method for controlling a DC / DC converter.

9. A method for controlling a DC / DC converter according to any one of claims 1 to 5, comprising: When the polarity of the load current changes from negative to positive, the voltage of the output-side capacitor is increased by the power supplied from the load. A method for controlling a DC / DC converter.

10. 3. A method for controlling a DC / DC converter according to claim 2, comprising: When it is determined that the polarity of the load current will change based on the load current command value, the change in the load current is delayed; The voltage of the output capacitor is increased before the polarity of the load current actually changes. A method for controlling a DC / DC converter.

11. A method for controlling a DC / DC converter according to any one of claims 1 to 5, comprising: estimating a voltage fluctuation of the output-side capacitor that occurs when the magnetization reversal current flows based on the voltage of the output-side capacitor; determining whether or not the voltage fluctuation causes the voltage of the output-side capacitor to fall below a predetermined lower limit value; When the polarity of the load current changes and the voltage of the output-side capacitor falls below the lower limit value due to the voltage fluctuation, the voltage of the output-side capacitor is increased. A method for controlling a DC / DC converter.

12. 12. A method for controlling a DC / DC converter according to claim 11, comprising: determining the voltage of the output capacitor after the increase based on the target value of the output voltage, the energy required for magnetization reversal, and the capacitance of the output capacitor; A method for controlling a DC / DC converter.

13. A DC / DC converter control device that controls a DC / DC converter by opening and closing the switch, the DC / DC converter comprising a reactor, a switch that controls the accumulation and release of energy in the reactor, and an output-side capacitor provided at an output end that is connected to a load, the reactor being configured by a core in which a gap is formed by a magnet whose magnetization direction is reversible, and a coil wound around the core, a load current change determination unit that determines whether or not a polarity of a load current that is a current output to the load changes; When the load current change determination unit determines that the polarity of the load current changes, opening and closing the switch so that the voltage of the output-side capacitor increases; With the voltage of the output capacitor increased, the switch is opened and closed so that a magnetization reversal current that reverses the magnetization direction of the magnet flows through the coil. A control device for a DC / DC converter.

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