Temperature increasing device, storage medium and temperature increasing method

Abstract

A temperature increasing device, a storage medium, and a temperature increasing method are provided. The temperature increasing device includes a switching element control unit that performs the following duty cycle control processing on an AC generating circuit including a first capacitor, a second capacitor, a first switching element, a second switching element, and a third switching element: from an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from 0 percent, and the duty cycle of the other of the first switching element, the second switching element, and the third switching element is decreased from 100 percent, the duty cycle of the other of the first switching element, the second switching element, and the third switching element being decreased by an amount corresponding to the amount by which the duty cycle of the first switching element, the second switching element, and the third switching element was increased from the initial state.

Description

Technical Field

[0001] The invention relates to a temperature rising device, a temperature rising program and a temperature rising method. Background Art

[0002] Conventionally, a technique has been used to raise the temperature of a secondary battery to an appropriate temperature at which degradation of the secondary battery is easily suppressed. An example of such a technique is a charge-discharge device disclosed in Japanese Patent No. 5225519.

[0003] This charging and discharging device controls the charging and discharging of a power storage device and includes a heating determination unit and a heating control unit. The heating determination unit obtains the temperature of the power storage device upon startup and determines whether to heat the power storage device based on the temperature. If the heating determination unit determines that the power storage device should be heated, the heating control unit determines the frequency characteristic of the internal resistance of the power storage device corresponding to the temperature and charge level of the power storage device, and controls the power storage device to alternately repeat charging and discharging at a charging and discharging cycle determined based on the frequency characteristic, thereby controlling the heating of the power storage device. Summary of the Invention

[0004] However, the above-mentioned charge and discharge device may cause a large loss in the circuit depending on the method of controlling the switching element.

[0005] One of the objectives of the present invention is to provide a temperature increasing device, a temperature increasing program, and a temperature increasing method that can reduce losses generated in a circuit.

[0006] A temperature raising device according to a first embodiment of the present invention comprises an AC generating circuit comprising: a first capacitor having one terminal connected to a terminal of an electric storage body; a first switching element connected to the other terminal of the first capacitor and a terminal of the electric storage body; a second capacitor having one terminal connected to a terminal of the electric storage body; a second switching element connected to a terminal of the electric storage body and a terminal of the second capacitor; and a third switching element connected to the other terminal of the first capacitor and the other terminal of the second capacitor. The temperature raising device comprises a switching element control unit that performs duty cycle control processing on the AC generating circuit: From an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from 0 percent, and the duty cycle of the other of the first switching element, the second switching element, and the third switching element is reduced from 100 percent, and the amount by which the duty cycle of the other is reduced from 100 percent is the amount by which the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from the initial state.

[0007] According to a second embodiment, based on the temperature increasing device of the first embodiment, the switching element control unit may perform the duty cycle control processing on the AC generating circuit having a parasitic diode in at least one of the first switching element, the second switching element, and the third switching element.

[0008] A third embodiment, based on the temperature increasing device of the second embodiment, may be such that the switching element control unit sets the length of the dead time provided between the following two states to be shorter than a predetermined value, to a length that can avoid the generation of a current exceeding a predetermined threshold value:

[0009] The two states are: a state in which the first and second switching elements are in a conducting state and the third switching element is in a non-conducting state; and a state in which the first and second switching elements are in a non-conducting state and the third switching element is in a conducting state.

[0010] A fourth option, based on the temperature increasing device of the first or second option, may also be that the switching element control unit performs the duty cycle control processing on the AC generating circuit in which at least one of the first switching element, the second switching element and the third switching element is connected to a freewheeling diode.

[0011] A fifth embodiment, based on the temperature increasing device of the fourth embodiment, may be such that the switching element control unit sets the length of the dead time provided between the following two states to be shorter than a predetermined value, to a length that can avoid the generation of a current exceeding a predetermined threshold value:

[0012] The two states are: a state in which the first and second switching elements are in a conducting state and the third switching element is in a non-conducting state; and a state in which the first and second switching elements are in a non-conducting state and the third switching element is in a conducting state.

[0013] The sixth option, based on the temperature rising device of any one of the above-mentioned first to fifth options, may also be that the switching element control unit performs the duty cycle control processing on the AC generating circuit in which at least one of the first switching element, the second switching element and the third switching element is an insulated gate bipolar transistor or a metal oxide film semiconductor power field effect transistor.

[0014] A seventh aspect of the present invention is a storage medium, wherein an AC generating circuit comprises: a first capacitor having one terminal connected to a terminal of an electric storage body; a first switching element connected to the other terminal of the first capacitor and a terminal of the electric storage body; a second capacitor having one terminal connected to a terminal of the electric storage body; a second switching element connected to a terminal of the electric storage body and the other terminal of the second capacitor; and a third switching element connected to the other terminal of the first capacitor and the other terminal of the second capacitor.

[0015] The storage medium stores a temperature raising program that enables a computer to implement a switching element control function, wherein the switching element control function performs a duty cycle control process on the AC generating circuit.

[0016] From an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of the first switching element, the duty cycle of the second switching element, and the duty cycle of the third switching element is increased from 0 percent, and the duty cycle of the other of the duty cycle of the first switching element, the duty cycle of the second switching element, and the duty cycle of the third switching element is reduced from 100 percent, and the amount by which the duty cycle of the other is reduced from 100 percent is the amount by which the duty cycle of one of the duty cycle of the first switching element, the duty cycle of the second switching element, and the duty cycle of the third switching element is increased from the initial state.

[0017] In an eighth aspect of the present invention, the temperature increasing method comprises an AC generating circuit comprising: a first capacitor having one terminal connected to a terminal of an electric storage body; a first switching element connected to the other terminal of the first capacitor and a terminal of the electric storage body; a second capacitor having one terminal connected to a terminal of the electric storage body; a second switching element connected to a terminal of the electric storage body and the other terminal of the second capacitor; and a third switching element connected to the other terminal of the first capacitor and the other terminal of the second capacitor.

[0018] The temperature raising method performs duty cycle control processing on the AC generating circuit:

[0019] From an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of the first switching element, the duty cycle of the second switching element, and the duty cycle of the third switching element is increased from 0 percent, and the duty cycle of the other of the duty cycle of the first switching element, the duty cycle of the second switching element, and the duty cycle of the third switching element is reduced from 100 percent, and the amount by which the duty cycle of the other is reduced from 100 percent is the amount by which the duty cycle of one of the duty cycle of the first switching element, the duty cycle of the second switching element, and the duty cycle of the third switching element is increased from the initial state.

[0020] According to the first to sixth aspects, the temperature increasing device controls the AC generating circuit so that no through-current flows through the third switching element during the reverse recovery time of the parasitic diode included in at least one of the first and second switching elements. Alternatively, according to the first to sixth aspects, the temperature increasing device controls the AC generating circuit so that no through-current flows through the third switching element during the reverse recovery time of the freewheeling diode connected to at least one of the first and second switching elements. Therefore, the temperature increasing device can reduce losses in the third switching element caused by such through-current. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a diagram showing an example of a driving mechanism according to the first embodiment and the second embodiment.

[0022] Figure 2 This is a diagram showing an example of an AC generating circuit controlled by the temperature increasing device according to the first and second embodiments.

[0023] Figure 3 This is a diagram showing an example of gate signals supplied to the first switching element, the second switching element, and the third switching element included in the AC generation circuit of the first and second embodiments, and AC current supplied from the AC generation circuit to the power storage body.

[0024] Figure 4 This is a diagram showing an example of a gate signal supplied to three switching elements by a temperature increasing device of a comparative example, the potential of two terminals of the third switching element when the gate signal is supplied, the current flowing through the third switching element and the current flowing through the first switching element when the gate signal is supplied, and the loss generated in the third switching element.

[0025] Figure 5 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the first period shown.

[0026] Figure 6 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the second period shown.

[0027] Figure 7 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the third period shown.

[0028] Figure 8 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fourth period shown.

[0029] Figure 9 This is a diagram showing an example of a comparative example of how the duty ratios of the first switching element, the second switching element, and the third switching element change over time, the voltage applied to the storage body, the first capacitor, and the second capacitor when a gate signal having the duty ratio is supplied to the AC generating circuit, the current supplied to the storage body, and the loss generated in the first switching element, the second switching element, and the third switching element.

[0030] Figure 10 This is a diagram showing an example of a gate signal supplied by the temperature increasing device of the first embodiment to three switching elements, the potential of two terminals of the third switching element when the gate signal is supplied, the current flowing through the third switching element and the current flowing through the first switching element when the gate signal is supplied, and the loss generated in the third switching element.

[0031] Figure 11 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the first period shown.

[0032] Figure 12 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the second period shown.

[0033] Figure 13It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the third period shown.

[0034] Figure 14 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fourth period shown.

[0035] Figure 15 This is a diagram showing an example of how the duty ratio of each of the first switching element, the second switching element, and the third switching element changes over time in a first embodiment, the voltage applied to the storage body, the first capacitor, and the second capacitor when a gate signal having the duty ratio is supplied to the AC generating circuit, the current supplied to the storage body, and the loss generated in each of the first switching element, the second switching element, and the third switching element.

[0036] Figure 16 This is a diagram showing an example of a gate signal supplied to three switching elements by a temperature increasing device of a second embodiment, the potential of two terminals of a third switching element when the gate signal is supplied, the current flowing through the third switching element and the current flowing through the first switching element when the gate signal is supplied, and the loss generated in the third switching element.

[0037] Figure 17 This is a diagram showing an example of a gate signal supplied to three switching elements by a temperature increasing device of a second embodiment, the potential of two terminals of a third switching element when the gate signal is supplied, a current flowing through the third switching element when the gate signal is supplied, a current flowing through the first switching element, and a loss generated in the third switching element.

[0038] Figure 18 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the first period shown.

[0039] Figure 19 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the second period shown.

[0040] Figure 20 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the third period shown.

[0041] Figure 21 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fourth period shown.

[0042] Figure 22 It is shown in Figure 17FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fifth period shown.

[0043] Figure 23 It is shown in Figure 17 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the sixth period shown.

[0044] Figure 24 It is shown in Figure 17 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the seventh period shown.

[0045] Figure 25 This is a diagram showing an example of the change over time of a second embodiment of the duty cycle of each of the first switching element, the second switching element, and the third switching element, the voltage applied to the storage body, the first capacitor, and the second capacitor when a gate signal having the duty cycle is supplied to the AC generating circuit, the current supplied to the storage body, and the loss generated in each of the first switching element, the second switching element, and the third switching element. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the temperature increasing device, temperature increasing program, and temperature increasing method according to the present invention will be described with reference to the accompanying drawings.

[0047] First, refer to Figures 1 to 3 , while explaining the driving mechanism of the embodiment. Figure 1 This is a diagram showing an example of a driving mechanism according to the first embodiment and the second embodiment. Figure 1 The driving mechanism 1 shown is a mechanism for driving a mobile body such as a two-wheeled, three-wheeled or four-wheeled vehicle. Figure 1 As shown, the drive mechanism 1 includes a power storage body 10 , a PDU (Power Drive Unit) 20 , a rotating electrical machine 30 , an engine 40 , drive wheels 50 , and a temperature increasing device 60 .

[0048] The power storage unit 10 is, for example, a secondary battery, and generates DC power and supplies it to the PDU 20. The PDU 20 includes a booster and an inverter. The PDU 20 uses the booster to boost the DC power supplied from the power storage unit 10. Furthermore, the PDU 20 uses the inverter to convert the boosted DC power into three-phase AC power and supplies it to the rotating electric machine 30.

[0049] The rotating electric machine 30 includes a rotor and a stator. It functions as an electric motor that supplies power to the drive wheels 50 of the mobile object. Furthermore, the rotating electric machine 30 can function as a generator that uses the kinetic energy of the mobile object to generate electricity during deceleration. The engine 40, such as a gasoline engine or a diesel engine, supplies power to the drive wheels 50 of the mobile object.

[0050] The temperature increasing device 60 increases the temperature of the power storage body 10 to a suitable operating temperature by passing an alternating current through the power storage body 10. Figure 1 As shown, the temperature increasing device 60 includes an AC generating circuit 61 and a switching element control unit 62 .

[0051] Figure 2 1 is a diagram showing an example of an AC generating circuit controlled by the temperature increasing device of the first embodiment and the second embodiment. Figure 2 As shown, the AC generating circuit 61 includes a first capacitor C1, a second capacitor C2, a first switching element S1, a second switching element S2, a third switching element S3, a first diode D1, a second diode D2, a third diode D3, a first gate signal transmitting unit G1, a second gate signal transmitting unit G2, and a third gate signal transmitting unit G3. The first switching element S1, the second switching element S2, and the third switching element S3 are, for example, N-type metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0052] One terminal of the first capacitor C1 is connected to the positive electrode of the power storage device 10, and the other terminal is connected to the drain terminal of the first switching element S1 and the source terminal of the third switching element S3. The drain terminal of the first switching element S1 is connected to the other terminal of the first capacitor C1, and the source terminal is connected to the negative electrode of the power storage device 10 and one terminal of the second capacitor C2. One terminal of the second capacitor C2 is connected to the negative electrode of the power storage device 10 and the source terminal of the first switching element S1, and the other terminal is connected to the source terminal of the second switching element and the drain terminal of the third switching element S3. The capacitance of the first capacitor C1 is equal to that of the second capacitor C2.

[0053] The second switching element S2 has a drain terminal connected to the positive electrode of the power storage body 10 and one terminal of the first capacitor C1, and a source terminal connected to the other terminal of the second capacitor C2 and the drain terminal of the third switching element S3. The third switching element S3 has a drain terminal connected to the source terminal of the second switching element S2 and the other terminal of the second capacitor C2, and a source terminal connected to the drain terminal of the first switching element S1 and the other terminal of the first capacitor C1.

[0054] The first diode D1 is a freewheeling diode connected to the first switching element S1, with its cathode terminal connected to the drain terminal of the first switching element S1 and its anode terminal connected to the source terminal of the first switching element S1. The second diode D2 is a freewheeling diode connected to the second switching element S2, with its cathode terminal connected to the drain terminal of the second switching element S2 and its anode terminal connected to the source terminal of the second switching element S2. The third diode D3 is a freewheeling diode connected to the second switching element S2, with its cathode terminal connected to the drain terminal of the third switching element S3 and its anode terminal connected to the source terminal of the third switching element S3.

[0055] The first gate signal sending unit G1 is connected to the gate terminal of the first switching element S1 and applies a high or low voltage to the gate terminal of the first switching element S1. The second gate signal sending unit G2 is connected to the gate terminal of the second switching element S2 and applies a high or low voltage to the gate terminal of the second switching element S2. The third gate signal sending unit G3 is connected to the gate terminal of the third switching element S3 and applies a high or low voltage to the gate terminal of the third switching element S3.

[0056] When a high voltage is applied to the gate terminals of the first switching element S1, the second switching element S2, and the third switching element S3, the conductance between the source terminal and the drain terminal is high, and the switching element enters a conductive state, allowing current to flow. On the other hand, when a low voltage is applied to the gate terminals of the first switching element S1, the second switching element S2, and the third switching element S3, the conductance between the source terminal and the drain terminal is low, and the switching element enters a non-conductive state, allowing little current to flow.

[0057] Therefore, when a high voltage is applied to the gate terminals of the first and second switching elements S1 and S2, and a low voltage is applied to the gate terminal of the third switching element S3, the first capacitor C1 and the second capacitor C2 are connected in parallel. On the other hand, when a low voltage is applied to the gate terminals of the first and second switching elements S1 and S2, and a high voltage is applied to the gate terminal of the third switching element S3, the first capacitor C1 and the second capacitor C2 are connected in series. Furthermore, between the periods when a high voltage is applied to the gate terminals of the first and second switching elements S1 and S2, and the period when a high voltage is applied to the gate terminal of the third switching element S3, a dead time is provided during which the first, second, and third switching elements S1, S2, and S3 are all de-energized.

[0058] Figure 3This is a diagram showing an example of gate signals supplied to the first switching element, the second switching element, and the third switching element included in the AC generation circuit of the first and second embodiments, and AC current supplied from the AC generation circuit to the power storage body.

[0059] Figure 3 In (a), the horizontal axis represents time, and the vertical axis represents the high or low voltage applied to the gate terminal of the third switching element S3. Figure 3 In (b), the horizontal axis represents time, and the vertical axis represents the high or low voltage applied to the gate terminals of the first switching element S1 and the second switching element S2. Figure 3 The period of the gate signal shown in (a) is Figure 3 The gate signals shown in (b) have equal periods. Figure 3 In (c), the horizontal axis represents time, and the vertical axis represents the current supplied from the AC generating circuit 61 to the power storage body 10 .

[0060] The resonance frequency of the AC generating circuit 61 when the first capacitor C1 and the second capacitor C2 are connected in series depends on the inductance component of the power storage body 10 and is approximately twice the resonance frequency of the AC generating circuit 61 when the two are connected in parallel. Figure 3 (a) and Figure 3 As shown in (b), the ratio of the time when a high voltage is applied to the gate terminal of the third switching element S3 to the time when a high voltage is applied to the gate terminal of the first switching element S1 and the gate terminal of the second switching element S2 becomes 1:2. Figure 3 (c) shows a relatively high accuracy resonant AC current supplied to the power storage body 10. Figure 3 (c) The current in the direction of charging the electricity storage body 10 is shown as a positive current.

[0061] The switching element control unit 62 performs duty cycle control processing, which will be described later. The switching element control unit 62 is implemented, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a control program implemented as software. At least a portion of the switching element control unit 62 can be implemented using hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or through a combination of software and hardware.

[0062] [Comparative Example]

[0063] Next, refer to Figures 4 to 9 , while describing a process in which the switching element control unit included in the temperature increasing device of the comparative example controls the AC generating circuit 61.

[0064] Figure 4 This is a diagram showing an example of gate signals supplied to three switching elements by a temperature increasing device of a comparative example, the potentials of the two terminals of the third switching element when the gate signals are supplied, the current flowing through the third switching element and the current flowing through the first switching element when the gate signals are supplied, and the loss generated in the third switching element. Figure 4 A first period T1 , a second period T2 , a third period T3 , and a fourth period T4 are shown.

[0065] Figure 4 (a) shows the change of the high or low voltage applied to the gate terminals of the first switching element S1, the second switching element S2 and the third switching element S3 over time. Figure 4 In (a), the upper part shows the change of the voltage applied to the gate terminal of the third switching element S3 with time by a solid line, and the lower part shows the change of the voltage applied to the gate terminal of the first switching element S1 and the gate terminal of the second switching element S2 with time by a solid line. Figure 4 The gate signal shown in (a) is supplied to the gate terminals of the first switching element S1 , the second switching element S2 , and the third switching element S3 .

[0066] In addition, if the first switching element S1, the second switching element S2 and the third switching element S3 are turned on at the same time, a short-circuit current will be generated. Therefore, the first switching element S1, the second switching element S2 and the third switching element S3 must be turned on exclusively. It is also necessary to consider the response delay of the switching elements and set the time width of the non-conducting state, that is, the dead time, for all the switching elements. Figure 4 In (a), the second period T2 and the third period T3 correspond to the dead time.

[0067] Figure 4 In (b), the solid lines show that the gate terminals of the three switching elements are each supplied with Figure 4 (a) shows the change in the potential of the drain terminal of the third switching element S3 with time when the voltage is shown. Figure 4 In (b), the dashed lines show that the gate terminals of the three switching elements are each supplied with Figure 4 (a) shows a temporal change in the potential of the source terminal of the third switching element S3 in the case of the voltage shown.

[0068] Figure 4 In (c), the solid lines show the voltage applied to the gate terminals of the three switching elements. Figure 4 (a) shows the change over time of the current flowing into the drain terminal of the third switching element S3 under the voltage shown. When the current flows into the drain terminal of the third switching element S3, it becomes a positive current, which is the sum of the current flowing through the third switching element S3 and the current flowing through the third diode D3. Figure 4 In (c), the dashed lines show the state of the circuit when the gate terminals of the three switching elements are each applied with Figure 4 (a) shows the temporal change in the current flowing into the source terminal of the first switching element S1 at the voltage shown. This current becomes positive when flowing into the source terminal of the first switching element S1 and is the sum of the current flowing through the first switching element S1 and the current flowing through the first diode D1.

[0069] Figure 4 In (d), the solid lines show the voltage applied to the gate terminals of the three switching elements. Figure 4 (a) shows the temporal change in the loss caused by the through current flowing through the third switching element S3 in the case of the voltage of FIG.

[0070] Figure 5 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through an AC generating circuit during the first period shown in FIG. Figure 4 In the first period T1 shown, the first switching element S1 and the second switching element S2 are energized, and the third switching element S3 is de-energized, so the first capacitor C1 and the second capacitor C2 are connected in parallel. Figure 5 The first capacitor C1 and the second capacitor C2 are charged by the current.

[0071] In addition, Figure 4 During the first period T1 shown in FIG. 1 , the first switching element S1 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 4 In (b), the dotted line indicates that the potential is equal to 0V (volt) at the negative electrode of the electricity storage body 10. Figure 4 During the first period T1 shown in FIG. 1 , the second capacitor C2 is continuously charged, and the voltage applied to the second capacitor C2 continuously increases. Therefore, the potential of the drain terminal of the third switching element S3 is as follows: Figure 4 In (b), it is shown by the solid line and continues to increase.

[0072] In addition, Figure 4During the first period T1 shown in FIG. 1 , the third switching element S3 is in a non-conductive state. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 4 In (c), the solid line shows that it is basically 0A (ampere). Figure 4 During the first period T1 shown in FIG. 1 , the first switching element S1 is in the energized state. Therefore, the current flowing into the source terminal of the first switching element S1 is as follows: Figure 4 As shown by the dotted line in (c), the current becomes substantially constant and negative.

[0073] In addition, Figure 4 During the first period T1 shown, the current flowing into the third switching element S3 is substantially 0A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 4 As shown by the solid line in (d), it is basically 0 W (watt).

[0074] Figure 6 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the second period shown in FIG. Figure 4 In the second period T2 shown in FIG. 1 , the first switching element S1, the second switching element S2, and the third switching element S3 are all in a non-conductive state. However, the third switching element S3 is connected to a third diode D3. Figure 6 As shown by arrow A60, current flows through the first capacitor C1, the third diode D3, and the second capacitor C2. This current charges the first capacitor C1 and the second capacitor C2. The second period T2 is the period from when the first switching element S1 and the second switching element S2 are de-energized until the second capacitor C2 is fully charged.

[0075] In addition, Figure 4 During the second period T2 shown in FIG. 1 , a current flows through the third diode D3, so the potential of the source terminal of the third switching element S3 is as follows: Figure 4 As shown by the dotted line in (b), it rises sharply to a potential equal to the potential of the drain terminal of the third switching element S3. Figure 4 During the second period T2 shown in FIG. 1 , the second capacitor C2 is also charged, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 4 As shown by the solid line in (b), the potential rises to the potential when the second capacitor C2 is fully charged.

[0076] In addition, Figure 4 During the second period T2 shown in FIG. 1 , a current flows out of the drain terminal of the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 4(c) shows a negative current as shown by the solid line. Figure 4 During the second period T2 shown in FIG. 1 , no current flows into the first switching element S1. Therefore, the current flowing into the source terminal of the first switching element S1 is as follows: Figure 4 As shown by the dotted line in (c), it is basically 0A.

[0077] In addition, Figure 4 During the second period T2 shown, the current flowing into the third switching element S3 is substantially 0A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 4 As shown by the solid line in (d), it is basically 0W.

[0078] Figure 7 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the third period shown in FIG. Figure 4 In the third period T3 shown, the first switching element S1, the second switching element S2 and the third switching element S3 are all in a non-energized state. However, the first switching element S1 is connected to the first diode D1, and the second switching element S2 is connected to the second diode D2. In addition, at the time point when the third period T3 starts, the third diode D3 has been flowing with current in the forward direction until just now, so it becomes a reverse recovery action. During the reverse recovery time, current flows in the order of the second capacitor C2, the third diode D3, and the first capacitor C1. After the reverse recovery time, the third diode D3 becomes a non-energized state. In addition, the first capacitor C1 and the second capacitor C2 become fully charged. Therefore, through the discharge of the first capacitor C1, as shown Figure 7 As shown by arrow A71, current flows through the first diode D1 and the first capacitor C1. In addition, similarly, the second capacitor C2 is discharged. Figure 7 As indicated by arrow A72 , current flows through the second capacitor C2 and the second diode D2 .

[0079] In addition, Figure 4 During the third period T3 shown in FIG. 1 , no current flows in the first switching element S1. Therefore, the potential of the source terminal of the third switching element S3 is as follows: Figure 4 As shown by the dotted line in (b), the potential of the negative electrode of the electricity storage body 10 drops sharply to 0V. Figure 4 During the third period T3 shown in FIG. 1 , the second capacitor C2 is discharging, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 4 In (b), it is shown by the solid line, which continuously decreases.

[0080] In addition, Figure 4During the third period T3 shown in FIG. 1 , no current flows through the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 4 (c) is shown by the solid line, which is basically 0A. Figure 4 During the third period T3 shown, no current flows in the first switching element S1 , and therefore, the current flowing into the source terminal of the first switching element S1 becomes substantially 0A.

[0081] In addition, Figure 4 During the third period T3 shown, the current flowing into the third switching element S3 is substantially 0 A. The loss caused by the through current flowing through the third switching element S3 is as follows: Figure 4 In (d), the solid line indicates 0W.

[0082] Figure 8 It is shown in Figure 4 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fourth period shown in FIG. Figure 4 In the fourth period T4 shown, the first switching element S1 and the second switching element S2 are in a non-conductive state, and the third switching element S3 is in a conductive state. At the start of the fourth period T4, a forward current has been flowing in the first diode D1 and the second diode D2 until now. The third switching element S3 changes from a non-conductive state to a conductive state, thereby applying a reverse voltage to the first diode D1 and the second diode D2, generating a reverse recovery current. That is, when a forward current is flowing, the first diode D1 and the second diode D2 are in a reverse recovery state. Figure 7 When the current indicated by the arrow A71 and the current indicated by the arrow A72 are flowing, the third switching element S3 becomes energized. Figure 8 As indicated by arrow A80 , current flows through the second diode D2 , the third switching element S3 , and the first diode D1 .

[0083] In addition, Figure 4 During the fourth period T4 shown in FIG. 1 , the potential of the source terminal of the third switching element S3 is as follows: Figure 4 As shown by the dotted line in (b), the potential of the drain terminal of the third switching element S3 decreases together with the potential of the drain terminal of the third switching element S3, and sometimes decreases sharply and returns to the potential equal to the potential of the drain terminal of the third switching element S3. Figure 4 During the fourth period T4 shown in FIG. 1 , the potential of the drain terminal of the third switching element S3 is as follows: Figure 4 As indicated by the solid line in (b), the voltage continues to decrease until it reaches a potential equal to 0 V at the negative electrode of the electricity storage body 10 .

[0084] In addition, Figure 4During the fourth period T4 shown in FIG. 1 , a current flows into the drain terminal of the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 4 (c) shows a positive current as shown by the solid line. Figure 4 During the fourth period T4 shown, no current flows in the first switching element S1 , so the current flowing into the source terminal of the first switching element S1 is substantially 0 A except when loss occurs in the third switching element S3 .

[0085] In addition, Figure 4 At the time point when the fourth period T4 starts, the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 4 As shown by the solid line in (d), the value exceeds 0W during the reverse recovery time of the first diode D1 and the second diode D2. Specifically, when the first and second switching elements S1 and S2 are energized and the third switching element S3 is de-energized, current flows in the direction of discharging the battery. During the dead time when the first and second switching elements S1 and S2 are de-energized and the third switching element S3 is also de-energized, current continues to flow in the direction of discharging the battery through the third diode D3. However, due to the resonance between the battery's inductance and the first and second capacitors C1 and C2, the current shifts to the direction of charging the battery. After forward current begins flowing through the first and second diodes D1 and D2 without passing through the third diode D3, when the third switching element S3 is energized, a through current flows through the second diode D2, the third switching element S3, and the first diode D1 during the reverse recovery time of the first and second diodes D1 and D2, resulting in significant losses. That is, if the length of the dead time is set to be shorter than a predetermined value, it is possible to prevent a large loss from occurring.

[0086] Figure 9 This is a diagram showing an example of how the duty cycle of each of the first switching element, the second switching element, and the third switching element changes over time, the voltage applied to the storage body, the first capacitor, and the second capacitor when a gate signal having the duty cycle is supplied to the AC generating circuit, the current supplied to the storage body, and the loss generated in each of the first switching element, the second switching element, and the third switching element.

[0087] Figure 9 (a) shows the change of the duty ratio of the first switching element S1, the second switching element S2 and the third switching element S3 over time. Specifically, Figure 9 In (a), the solid line shows the change of the duty ratio of the third switching element S3 over time. Figure 9In (a), the dotted lines show the temporal changes in the duty ratios of the first switching element S1 and the second switching element S2.

[0088] The switching element control unit of the comparative example is as follows Figure 9 As shown in (a), the duty ratio of the third switching element S3 is increased from 0% to 33% at a constant speed. Figure 9 As shown in (a), the duty ratios of the first switching element S1 and the second switching element S2 are increased from 0% to 66% at the same rate as the third switching element S3. Figure 9 As shown by the dashed line in (a), the dead time decreases from 100% to 1% as time passes.

[0089] Figure 9 (b) shows that the AC generating circuit is supplied with Figure 9 (a) shows the temporal change of the voltage applied to the power storage body 10, the first capacitor C1 or the second capacitor C2 in the case of a gate signal with a duty ratio shown in FIG. Figure 9 In (b), the solid line shows that the AC generating circuit 61 is supplied with Figure 9 (a) shows the temporal change of the voltage applied to the power storage body 10 in the case of a gate signal with a duty ratio shown in FIG. Figure 9 In (b), the dotted line shows that the AC generating circuit 61 is supplied with Figure 9 (a) shows a temporal change in the voltage applied to the first capacitor C1 or the second capacitor C2 in the case of a gate signal with a duty ratio shown in FIG.

[0090] The amplitude of the voltage applied to the electricity storage body 10 is as follows: Figure 9 As shown by the solid line in (b), the voltage amplitude increases with the increase of at least one of the duty ratios of the first switching element S1 and the second switching element S2 and the duty ratio of the third switching element S3. Figure 9 As shown by the dotted line in (b), the voltage amplitude increases with the increase of at least one of the duty ratios of the first switching element S1 and the second switching element S2, and the duty ratio of the third switching element S3. Figure 9 As indicated by the dotted line in (b), the duty cycle increases with an increase in at least one of the duty ratios of the first switching element S1 and the second switching element S2 and the duty ratio of the third switching element S3.

[0091] Figure 9 (c) shows that the AC generating circuit 61 is supplied with Figure 9 The current supplied to the power storage body 10 in the case of the gate signal with the duty ratio shown in (a). The current supplied to the power storage body 10 is as follows Figure 9 As shown in (c), the duty cycle increases with an increase in at least one of the duty cycles of the first switching element S1 and the second switching element S2 and the duty cycle of the third switching element S3.

[0092] Figure 9 (d) shows that the AC generating circuit 61 is supplied with Figure 9 In the case of a gate signal with a duty ratio shown in (a), a loss occurs in the first switching element S1, the second switching element S2, or the third switching element S3. Specifically, Figure 9 In (d), the loss generated in the first switching element S1 or the second switching element S2 is shown by a solid line. Figure 9 In (d), the loss generated in the third switching element S3 is shown by a dotted line.

[0093] like Figure 9 As shown in (d), the losses in the first switching element S1, the second switching element S2, and the third switching element S3 all reach their maximum values ​​before a predetermined time has passed since the amplitude of the current flowing through the power storage body 10 becomes substantially constant. Furthermore, in a region where the dead time is shorter than a predetermined value, the losses in the first switching element S1, the second switching element S2, and the third switching element S3 remain stable at low values.

[0094] [First embodiment]

[0095] Next, refer to Figures 10 to 15 , a process of controlling the AC generating circuit 61 by the switching element control unit 62 included in the temperature increasing device 60 of the first embodiment will be described.

[0096] Figure 10 This is a diagram showing an example of gate signals supplied to three switching elements by the temperature increasing device of the first embodiment, potentials at two terminals of the third switching element when the gate signals are supplied, current flowing through the third switching element and current flowing through the first switching element when the gate signals are supplied, and loss generated in the third switching element. Figure 10 A first period T11 , a second period T12 , a third period T13 , and a fourth period T14 are shown.

[0097] Figure 10 (a) shows the change of the high or low voltage applied to the gate terminals of the first switching element S1, the second switching element S2 and the third switching element S3 over time. Figure 10In (a), the upper section shows the change of the voltage applied to the gate terminal of the third switching element S3 with time by a solid line, and the lower section shows the change of the voltage applied to the gate terminal of the first switching element S1 and the gate terminal of the second switching element S2 with time by a solid line. Figure 10 The gate signal shown in (a) is supplied to the gate terminals of the first switching element S1 , the second switching element S2 , and the third switching element S3 .

[0098] Figure 10 In (b), the solid lines show that the gate terminals of the three switching elements are each supplied with Figure 10 (a) shows the change in the potential of the drain terminal of the third switching element S3 with time when the voltage is shown. Figure 10 In (b), the dashed lines show that the gate terminals of the three switching elements are each supplied with Figure 10 (a) shows a temporal change in the potential of the source terminal of the third switching element S3 in the case of the voltage shown.

[0099] Figure 10 In (c), the solid lines show the voltage applied to the gate terminals of the three switching elements. Figure 10 (a) shows the change over time of the current flowing into the drain terminal of the third switching element S3 under the voltage shown. When the current flows into the drain terminal of the third switching element S3, it becomes a positive current, which is the sum of the current flowing through the third switching element S3 and the current flowing through the third diode D3. Figure 10 In (c), the dashed lines show the state of the circuit when the gate terminals of the three switching elements are each applied with Figure 10 (a) shows the temporal change in the current flowing into the source terminal of the first switching element S1 at the voltage shown. This current becomes positive when flowing into the source terminal of the first switching element S1 and is the sum of the current flowing through the first switching element S1 and the current flowing through the first diode D1.

[0100] Figure 10 In (d), the solid lines show the voltage applied to the gate terminals of the three switching elements. Figure 10 (a) shows a temporal change in the loss caused by the through current flowing through the third switching element S3 in the case of the voltage shown.

[0101] Figure 11 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through an AC generating circuit during the first period shown in FIG. Figure 10In the first period T11 shown, the first switching element S1 and the second switching element S2 are in the energized state, and the third switching element S3 is in the non-energized state, so the first capacitor C1 and the second capacitor C2 are connected in parallel. Figure 11 The first capacitor C1 and the second capacitor C2 are charged by the current.

[0102] In addition, Figure 10 During the first period T11 shown in FIG. 1 , the first switching element S1 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 10 In (b), the dotted line indicates that the potential of the negative electrode of the electricity storage body 10 is equal to 0V. Figure 10 During the first period T11 shown in FIG. 1 , the second capacitor C2 is continuously charged, and the voltage applied to the second capacitor C2 continuously increases. Therefore, the potential of the drain terminal of the third switching element S3 is as follows: Figure 10 In (b), it is shown by the solid line and continues to increase.

[0103] In addition, Figure 10 During the first period T11 shown in FIG. 1 , the third switching element S3 is in a non-conductive state. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 10 (c) is shown by the solid line, which is basically 0A. Figure 10 During the first period T11 shown in FIG. 1 , the first switching element S1 is in the energized state. Therefore, the current flowing into the source terminal of the first switching element S1 is as follows: Figure 10 As shown by the dotted line in (c), the current becomes substantially constant and negative.

[0104] In addition, Figure 10 During the first period T11 shown, the current flowing into the third switching element S3 is substantially 0 A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as shown in FIG. Figure 10 In (d), the solid line indicates 0 W (watt).

[0105] Figure 12 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the second period shown in FIG. Figure 10 In the second period T12 shown in FIG. 1 , the first switching element S1, the second switching element S2, and the third switching element S3 are all in a non-conductive state. However, the third switching element S3 is connected to the third diode D3. Figure 12 As shown by arrow A120, a current flows through the first capacitor C1, the third diode D3, and the second capacitor C2. The first capacitor C1 and the second capacitor C2 are charged by this current.

[0106] in addition, Figure 10 The second period T12 shown is a dead time provided between the state where the first and second switching elements S1 and S2 are energized and the third switching element S3 is de-energized, and the state where the first and second switching elements S1 and S2 are de-energized and the third switching element S3 is energized. Furthermore, the switching element control unit 62 of the first embodiment sets the minimum dead time by taking into account the transition time from the energized state to the de-energized state of the first and second switching elements S1 and S2, and the transition time from the de-energized state to the energized state of the third switching element S3. The length of the second period T12 is adjusted to a length sufficient to prevent the generation of a current exceeding a predetermined threshold.

[0107] In addition, Figure 10 During the second period T12 shown in FIG. 1 , a current flows through the third diode D3, so the potential of the source terminal of the third switching element S3 is as follows: Figure 10 As shown by the dotted line in (b), it starts to rise sharply to a potential equal to the potential of the drain terminal of the third switching element S3. Figure 10 During the second period T12 shown in FIG. 1 , the second capacitor C2 is also charged, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 10 As shown by the solid line in (b), the potential rises to the potential when the second capacitor C2 is fully charged.

[0108] In addition, Figure 10 During the second period T12 shown in FIG. 1 , a current flows out of the drain terminal of the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 10 (c) is shown by the solid line, and starts to increase. On the other hand, Figure 10 During the second period T12 shown in FIG. 1 , the current flowing into the source terminal of the first switching element S1 is as follows: Figure 10 As shown by the dotted line in (c), it starts to decrease.

[0109] In addition, Figure 10 During the second period T12 shown, the current flowing into the third switching element S3 is substantially 0A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as shown in FIG. Figure 10 In (d), the solid line indicates 0W.

[0110] Figure 13 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the third period shown in FIG. Figure 10 In the third period T13 shown, the first switching element S1 and the second switching element S2 are continuously Figure 10 The second period T12 shown in FIG. 1 is in a non-conductive state, and the third switching element S3 is switched to a conductive state. Figure 13 As shown by arrow A130, Figure 10 In the second period T12 shown, the current flowing through the third diode D3 flows through the third switching element S3, and the first capacitor C1 and the second capacitor C2 are charged by this current.

[0111] In addition, Figure 10 During the third period T13 shown in FIG. 1 , the third switching element S3 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 10 As shown by the dotted line in (b), the potential of the other terminal of the second capacitor C2 rises sharply to the potential of the drain terminal of the third switching element S3. Figure 10 During the third period T13 shown in FIG. 1 , the second capacitor C2 is continuously charged, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 10 As shown by the solid line in (b), the voltage continues to increase until the first capacitor C1 and the second capacitor C2 are fully charged.

[0112] In addition, Figure 10 During the third period T13 shown in FIG. 1 , the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 10 (c) shows a positive current as shown by the solid line. Figure 10 During the third period T13 shown in FIG. 1 , the current flowing into the source terminal of the first switching element S1 is as follows: Figure 10 As shown by the dotted line in (c), the current becomes negative.

[0113] In addition, Figure 10 During the third period T13 shown in FIG. 1 , the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 10 In (d), the solid line indicates 0W.

[0114] Figure 14 It is shown in Figure 10 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fourth period shown in FIG. Figure 10 In the fourth period T14 shown, Figure 10 Similarly, in the third period T13 shown, the first switch element S1 and the second switch element S2 are in the non-conductive state, and the third switch element S3 is in the conductive state. Figure 10 The third period T13 shown ends at the time when the battery is fully charged. Figure 14As shown by arrow A140, a current flows through the second capacitor C2, the third switching element S3, and the first capacitor C1. In addition, this current flows by discharging the first capacitor C1 and the second capacitor C2.

[0115] In addition, Figure 10 During the fourth period T14 shown in FIG. 14 , the third switching element S3 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 10 As shown by the dotted line in (b), the potential of the other terminal of the second capacitor C2 rises sharply to the potential of the drain terminal of the third switching element S3. Figure 10 During the fourth period T14 shown in FIG. 1 , the second capacitor C2 is discharging, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 10 As indicated by the solid line in (b), the voltage continues to decrease until it reaches a potential equal to 0 V at the negative electrode of the electricity storage body 10 .

[0116] In addition, Figure 10 During the fourth period T14 shown in FIG. 14 , a current flows into the drain terminal of the third switching element S3 . Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 10 (c) shows a positive current as shown by the solid line. Figure 10 During the fourth period T14 shown, no current flows in the first switching element S1 , and therefore, the current flowing into the source terminal of the first switching element S1 becomes substantially 0A.

[0117] in addition, Figure 10 The fourth period T14 shown does not become the reverse recovery time of the first diode D1 and the second diode D2. Therefore, the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 10 In (d), the solid line indicates 0W.

[0118] Figure 15 This shows that the AC generating circuit is supplied with Figure 10 A diagram showing an example of the voltages applied to the power storage body, the first capacitor, and the second capacitor, the duty ratios of the first switching element, the second switching element, and the third switching element, the current supplied to the power storage body, and the losses generated in the first switching element, the second switching element, and the third switching element when the gate signal is shown.

[0119] Figure 15 (a) shows the change of the duty ratio of the first switching element S1, the second switching element S2 and the third switching element S3 over time. Specifically, Figure 15 In (a), the solid line shows the change of the duty ratio of the third switching element S3 over time. Figure 15 In (a), the dotted lines show the temporal changes in the duty ratios of the first switching element S1 and the second switching element S2.

[0120] The switching element control unit 62 of the first embodiment performs the following operations: Figure 15 The dotted lines in (a) show the process of increasing the duty ratio of the first switching element S1 and the second switching element S2 from 0% to 66%. This process is an example of increasing the duty ratio of the first switching element S1 and the second switching element S2 from 0% starting from the initial state where the first switching element S1, the second switching element S2, and the third switching element S3 are in a non-energized state.

[0121] In addition, the switching element control unit 62 of the first embodiment performs the following operations: Figure 15 The solid line in (a) shows a process of increasing the duty ratio of the third switching element S3 from 0% to 100% at a constant rate.

[0122] Furthermore, the switching element control unit 62 of the first embodiment performs the following operations: Figure 15 As shown by the solid line in (a), the duty ratio of the third switching element S3 is reduced from 100% to 33% at the same speed as the duty ratio of the first switching element S1 and the second switching element S2 is increased. Figure 15 As shown in (a), the process of increasing the duty ratios of the first switching element S1 and the second switching element S2 from 0% to 66% at the same rate as that of the third switching element S3 is started. Furthermore, this process is an example of a process in which, from an initial state in which the first switching element S1, the second switching element S2, and the third switching element S3 are in a non-energized state, the duty ratio of the first switching element S1 and the duty ratio of the second switching element S2 are increased, and then the duty ratio of the third switching element S3 is reduced from 100% by the amount by which the duty ratios of the first switching element S1 and the second switching element S2 are increased.

[0123] Figure 15 (b) shows that the AC generating circuit 61 is supplied with Figure 15 (a) shows the temporal change of the voltage applied to the power storage body 10, the first capacitor C1 or the second capacitor C2 in the case of a gate signal with a duty ratio shown in FIG. Figure 15 In (b), the solid line shows that the AC generating circuit 61 is supplied with Figure 15 (a) shows the temporal change of the voltage applied to the power storage body 10 in the case of a gate signal with a duty ratio shown in FIG. Figure 15 In (b), the dotted line shows that the AC generating circuit 61 is supplied with Figure 15(a) shows a temporal change in the voltage applied to the first capacitor C1 or the second capacitor C2 in the case of a gate signal with the duty ratio shown.

[0124] The amplitude of the voltage applied to the electricity storage body 10 is as follows: Figure 15 As shown by the solid line in (b), the duty cycle of the first switching element S1 and the second switching element S2 increases and the duty cycle of the third switching element S3 decreases. In addition, the amplitude of the voltage applied to the first capacitor C1 is as shown in FIG. Figure 15 As shown by the dotted line in (b), the duty cycle of the first switching element S1 and the second switching element S2 increases and the duty cycle of the third switching element S3 decreases. Similarly, the amplitude of the voltage applied to the second capacitor C2 is as follows: Figure 15 As shown by the dotted line in (b), the duty cycle increases with the increase of the duty cycle of the first switching element S1 and the second switching element S2 and the decrease of the duty cycle of the third switching element S3.

[0125] Figure 15 (c) shows that the AC generating circuit 61 is supplied with Figure 15 The current supplied to the power storage body 10 in the case of the gate signal with the duty ratio shown in (a). The current supplied to the power storage body 10 is as follows Figure 15 As shown in (c), the duty cycle of the first switching element S1 and the second switching element S2 increases and the duty cycle of the third switching element S3 decreases.

[0126] Figure 15 (d) shows that the AC generating circuit 61 is supplied with Figure 15 In the case of a gate signal with a duty ratio shown in (a), a loss occurs in the first switching element S1, the second switching element S2, or the third switching element S3. Specifically, Figure 15 In (d), the loss generated in the first switching element S1 or the second switching element S2 is shown by a solid line. Figure 15 In (d), the loss generated in the third switching element S3 is shown by a dotted line.

[0127] like Figure 15 As shown by the dotted line in (d), the loss generated in the third switching element S3 increases as the amplitude of the current flowing through the power storage body 10 tends to become substantially constant, and becomes substantially constant after a predetermined time has passed since the amplitude of the current became substantially constant. In addition, the loss generated in the third switching element S3 is different from the loss generated in the third switching element S3 in the case of the comparative example, and does not become maximum in the middle of the increase. Moreover, these Figure 15The same is true for the loss generated in the first switching element S1 and the loss generated in the second switching element S2 as shown by the solid line in (d).

[0128] [Second embodiment]

[0129] Next, refer to Figures 16 to 25 , a process of controlling the AC generating circuit 61 by the switching element control unit 62 included in the temperature increasing device 60 of the second embodiment will be described.

[0130] Figure 16 This is a diagram showing an example of gate signals supplied to three switching elements by the temperature increasing device of the second embodiment, potentials at two terminals of the third switching element when the gate signals are supplied, current flowing through the third switching element and current flowing through the first switching element when the gate signals are supplied, and loss generated in the third switching element. Figure 16 A first period T21 , a second period T22 , a third period T23 , and a fourth period T24 are shown.

[0131] Figure 17 This is a diagram showing an example of gate signals supplied to three switching elements by the temperature increasing device of the second embodiment, potentials at both terminals of the third switching element when the gate signals are supplied, current flowing through the third switching element when the gate signals are supplied, current flowing through the first switching element, and loss generated in the third switching element. Figure 17 A fourth period T24 , a fifth period T25 , a sixth period T26 , and a seventh period T27 are shown.

[0132] Figure 16 (a) and Figure 17 (a) shows the change of the high or low voltage applied to the gate terminals of the first switching element S1, the second switching element S2 and the third switching element S3 over time. Figure 16 (a) and Figure 17 In (a), the upper part shows the change of the voltage applied to the gate terminal of the third switching element S3 with time by a solid line, and the lower part shows the change of the voltage applied to the gate terminal of the first switching element S1 and the gate terminal of the second switching element S2 with time by a dotted line. Figure 16 (a) and Figure 17 The gate signal shown in (a) is supplied to the gate terminals of the first switching element S1 , the second switching element S2 , and the third switching element S3 .

[0133] Figure 16 (b) and Figure 17 In (b), the solid lines show that the gate terminals of the three switching elements are each supplied with Figure 16 (a) and Figure 17 (b) The potential of the drain terminal of the third switching element S3 changes with time when the voltage is shown. Figure 16 (b) and Figure 17 In (b), the dashed lines show that the gate terminals of the three switching elements are each supplied with Figure 16 (a) and Figure 17 (b) shows a temporal change in the potential of the source terminal of the third switching element S3 in the case of the voltage shown.

[0134] Figure 16 (c) and Figure 17 In (c), the solid lines show the voltage applied to the gate terminals of the three switching elements. Figure 16 (a) and Figure 17 (a) shows the change over time of the current flowing into the drain terminal of the third switching element S3 under the voltage shown. When the current flows into the drain terminal of the third switching element S3, it becomes a positive current, which is the sum of the current flowing through the third switching element S3 and the current flowing through the third diode D3. Figure 16 (c) and Figure 17 In (c), the dashed lines show the state of the circuit when the gate terminals of the three switching elements are each applied with Figure 16 (a) and Figure 17 (a) shows the temporal change of the current flowing into the source terminal of the first switching element S1 under the voltage shown. When the current flows into the source terminal of the first switching element S1, it becomes a positive current, which is the sum of the current flowing through the first switching element S1 and the current flowing through the first diode D1. Figure 17 In (c), the single-dot chain line shows that the gate terminals of the three switching elements are each supplied with Figure 17 (a) is a graph showing a temporal change in the forward current flowing through the first diode D1 at the voltage shown.

[0135] Figure 16 (d) and Figure 17 In (d), the solid lines show the voltage applied to the gate terminals of the three switching elements. Figure 16 (a) and Figure 17 (d) shows a temporal change in the loss caused by the through current flowing through the third switching element S3 in the case of the voltage shown.

[0136] Figure 18 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through an AC generating circuit during the first period shown in FIG. Figure 16In the first period T21 shown, the first switching element S1 and the second switching element S2 are in the energized state, and the third switching element S3 is in the non-energized state, so the first capacitor C1 and the second capacitor C2 are connected in parallel. Figure 18 The first capacitor C1 and the second capacitor C2 are charged by the current.

[0137] In addition, Figure 16 During the first period T21 shown in FIG. 1 , the first switching element S1 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 16 In (b), the dotted line indicates that the potential of the negative electrode of the electricity storage body 10 is equal to 0 V. Figure 16 During the first period T21 shown in FIG. 1 , the second capacitor C2 is continuously charged, and the voltage applied to the second capacitor C2 continuously increases. Therefore, the potential of the drain terminal of the third switching element S3 is as follows: Figure 16 In (b), it is shown by the solid line and continues to increase.

[0138] In addition, Figure 16 During the first period T21 shown in FIG. 1 , the third switching element S3 is in a non-conductive state. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 16 (c) is shown by the solid line, which is basically 0A. Figure 16 During the first period T21 shown, the first switching element S1 is in the energized state, and current flows out of the source terminal of the first switching element S1. Therefore, the current flowing into the source terminal of the first switching element S1 is as follows: Figure 16 As shown by the dotted line in (c), the current becomes substantially constant and negative.

[0139] In addition, Figure 16 During the first period T21 shown, the current flowing into the third switching element S3 is substantially 0 A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as shown in FIG. Figure 16 In (d), the solid line indicates 0 W (watt).

[0140] Figure 19 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the second period shown in FIG. Figure 16 In the second period T22 shown in FIG. 1 , the first switching element S1, the second switching element S2, and the third switching element S3 are all in a non-conductive state. However, the third switching element S3 is connected to the third diode D3. Figure 19As shown by arrow A190, a current flows through the first capacitor C1, the third diode D3, and the second capacitor C2. The first capacitor C1 and the second capacitor C2 are charged by this current.

[0141] In addition, the so-called Figure 16 The second period T22 shown is a dead time provided between the state where the first and second switching elements S1 and S2 are energized and the third switching element S3 is de-energized, and the state where the first and second switching elements S1 and S2 are de-energized and the third switching element S3 is energized. Furthermore, the switching element control unit 62 of the second embodiment sets the minimum dead time by taking into account the transition time from the energized state to the de-energized state of the first and second switching elements S1 and S2, and the transition time from the de-energized state to the energized state of the third switching element S3. The length of the second period T22 is adjusted to a length sufficient to prevent the generation of a current exceeding a predetermined threshold.

[0142] In addition, Figure 16 During the second period T22 shown in FIG. 1 , a current flows through the third diode D3, so the potential of the source terminal of the third switching element S3 is as follows: Figure 16 As shown by the dotted line in (b), it starts to rise sharply to a potential equal to the potential of the drain terminal of the third switching element S3. Figure 16 During the second period T22 shown in FIG. 1 , the second capacitor C2 is also charged, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 16 As shown by the solid line in (b), the potential rises toward the case where the second capacitor C2 is fully charged.

[0143] In addition, Figure 16 During the second period T22 shown in FIG. 1 , a current flows out from the drain terminal of the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 16 (c) is shown by the solid line, and begins to decrease. Figure 16 During the second period T22 shown in FIG. 1 , the current flowing into the source terminal of the first switching element S1 is as follows: Figure 16 As shown by the dotted line in (c), it starts to increase.

[0144] In addition, Figure 16 During the second period T22 shown, the current flowing into the third switching element S3 is substantially 0A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as shown in FIG. Figure 16 In (d), the solid line indicates 0W.

[0145] Figure 20 It is shown in Figure 16FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the third period shown in FIG. Figure 16 In the third period T23 shown, the first switch element S1 and the second switch element S2 are continuously Figure 16 The second period T22 shown in FIG. 1 is in a non-conductive state, and the third switching element S3 is switched to a conductive state. Figure 20 As shown by arrow A200, Figure 16 In the second period T22 shown, the current flowing through the third diode D3 flows through the third switching element S3, and the first capacitor C1 and the second capacitor C2 are charged by this current.

[0146] In addition, Figure 16 During the third period T23 shown in FIG. 1 , the third switching element S3 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 16 As shown by the dotted line in (b), the potential of the other terminal of the second capacitor C2 rises sharply to the potential of the drain terminal of the third switching element S3. Figure 16 During the third period T23 shown in FIG. 1 , the second capacitor C2 is continuously charged, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 16 As shown by the solid line in (b), the voltage continues to increase until the first capacitor C1 and the second capacitor C2 are fully charged.

[0147] In addition, Figure 16 During the third period T23 shown in FIG. 1 , the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 16 (c) shows a negative current as shown by the solid line. Figure 16 During the third period T23 shown in FIG. 1 , the current flowing into the source terminal of the first switching element S1 is as follows: Figure 16 In (c), the dotted line indicates a positive current.

[0148] In addition, Figure 16 During the third period T23 shown in FIG. 1 , the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 16 In (d), the solid line indicates 0W.

[0149] Figure 21 It is shown in Figure 16 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fourth period shown in FIG. Figure 16 and Figure 17 In the fourth period T24 shown, Figure 16 Similarly, in the third period T3 shown, the first switch element S1 and the second switch element S2 are in the non-conductive state, and the third switch element S3 is in the conductive state. Figure 16 The third period T23 shown ends at the time when the battery is fully charged. Figure 21 As shown by arrow A210, a current flows through the second capacitor C2, the third switching element S3, and the first capacitor C1. In addition, this current flows by discharging the first capacitor C1 and the second capacitor C2.

[0150] In addition, Figure 16 and Figure 17 During the fourth period T24 shown in FIG. 1 , the third switching element S3 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 16 (b) and Figure 17 In (b), the dotted line indicates that the potential of the other terminal of the second capacitor C2, that is, the potential of the drain terminal of the third switching element S3, is substantially the same. Figure 16 and Figure 17 During the fourth period T24 shown in FIG. 1 , the second capacitor C2 is discharging, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 16 (b) and Figure 17 In (b), it is shown by the solid line, which decreases.

[0151] In addition, Figure 16 and Figure 17 During the fourth period T24 shown in FIG. 1 , a current flows into the drain terminal of the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 16 (c) and Figure 17 (c) shows a positive current as shown by the solid line. Figure 16 and Figure 17 During the fourth period T24 shown, no current flows in the first switching element S1 , and therefore, the current flowing into the source terminal of the first switching element S1 becomes substantially 0A.

[0152] in addition, Figure 16 and Figure 17 The fourth period T24 shown does not become the reverse recovery time of the first diode D1 and the second diode D2. Therefore, the loss caused by the through current flowing through the third switching element S3 is as follows: Figure 16 (d) and Figure 17 In (d), the solid line indicates 0W.

[0153] Figure 22 It is shown in Figure 17 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the fifth period shown in FIG. Figure 17In the fifth period T25 shown, the first switch element S1 and the second switch element S2 are switched to the energized state, and the third switch element S3 is switched to the non-energized state following the fourth period T24. However, the first diode D1 is connected to the first switch element S1, and the second diode D2 is connected to the second switch element S2. In addition, at the start of the fifth period T25, the first capacitor C1 and the second capacitor C2 are continuously discharging. Therefore, the discharge of the first capacitor C1, as shown in FIG. Figure 22 As shown by arrow A221, current flows through the first diode D1 and the first capacitor C1. In addition, similarly, the second capacitor C2 is discharged. Figure 22 As indicated by arrow A222 , current flows through the second capacitor C2 and the second diode D2 .

[0154] In addition, Figure 17 During the fifth period T25 shown in FIG. 1 , no current flows in the first switching element S1, so the potential of the source terminal of the third switching element S3 is as follows: Figure 17 As shown by the dotted line in (b), the potential of the negative electrode of the electricity storage body 10 drops sharply to 0V. Figure 17 During the fifth period T25 shown in FIG. 1 , the second capacitor C2 is discharging, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 17 In (b), it is shown by the solid line, which continuously decreases.

[0155] In addition, Figure 17 During the fifth period T25 shown in FIG. 1 , no current flows through the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 17 (c) is shown by the solid line, which is basically 0A. Figure 17 During the fifth period T25 shown in FIG. 1 , no current flows into the first switching element S1. Therefore, the current flowing into the source terminal of the first switching element S1 is as follows: Figure 17 (c) is shown by the dotted line, which is basically 0A. It should be noted that the current flowing in the forward direction of the first diode D1 is as follows Figure 17 As indicated by the one-dot chain line in (c), the current becomes positive during the fifth period T25.

[0156] In addition, Figure 17 During the fifth period T25 shown, the current flowing into the third switching element S3 is substantially 0 A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as shown in FIG. Figure 17 In (d), the solid line indicates 0W.

[0157] Figure 23 It is shown in Figure 17FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the sixth period shown in FIG. Figure 17 In the sixth period T26 shown in FIG. 2 , following the fifth period T25 , the first switch element S1 and the second switch element S2 are in the energized state, and the third switch element S3 is in the non-energized state. Figure 22 As shown by arrow A221, the current flowing in the first diode D1 during the fifth period T25 becomes as follows: Figure 23 As shown by arrow A231, the current flows through the first switching element S1. Figure 22 As shown by arrow A222, the current flowing in the second diode D2 in the fifth period T25 becomes as follows: Figure 23 The current flows through the second switching element S2 as indicated by arrow A232.

[0158] In addition, Figure 17 During the sixth period T26 shown in FIG. 1 , current flows through the first switching element S1, so the potential of the source terminal of the third switching element S3 is as follows: Figure 17 (b) As shown by the dotted line, the potential of the negative electrode of the electricity storage body 10 becomes 0V. Figure 17 During the sixth period T26 shown in FIG. 1 , the second capacitor C2 is discharging, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 17 In (b), it is shown by the solid line, which continuously decreases.

[0159] In addition, Figure 17 During the sixth period T26 shown in FIG. 1 , no current flows through the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 17 (c) is shown by the solid line, which is basically 0A. Figure 17 During the sixth period T26 shown in FIG. 1 , a current flows through the first switching element S1. Therefore, the current flowing into the source terminal of the first switching element S1 is as follows: Figure 17 In (c), the dotted line indicates a positive current.

[0160] In addition, Figure 17 During the sixth period T26 shown, the current flowing into the third switching element S3 is substantially 0 A. Therefore, the loss caused by the through current flowing through the third switching element S3 is as shown in FIG. Figure 17 In (d), the solid line indicates 0W.

[0161] Figure 24 It is shown in Figure 17 FIG. 1 is a diagram showing an example of a current flowing through the AC generating circuit during the seventh period shown in FIG. Figure 17 In the seventh period T17 shown, Figure 17Similarly, in the third period T23 shown, the first switch element S1 and the second switch element S2 are in the non-conductive state, and the third switch element S3 is in the conductive state. Figure 17 At the end of the third period T23 shown in FIG. 1 , the charge is substantially not stored. Figure 24 As shown by arrow A241 in FIG. 1 , a current flows through the first capacitor C1 and the first switch element S1. The first capacitor C1 is charged by the current. Figure 24 As shown by arrow A242, a current flows through the second switching element S2 and the second capacitor C2, and the first capacitor C1 is charged by this current.

[0162] In addition, Figure 17 During the seventh period T17 shown in FIG. 1 , the first switching element S1 is in the energized state, so the potential of the source terminal of the third switching element S3 is as follows: Figure 17 As shown by the dotted line in (b), the potential continues to decrease until it reaches the potential equal to 0 V at the negative electrode of the electricity storage body 10. Figure 17 During the seventh period T17 shown in FIG. 1 , the second capacitor C2 is being charged, so the potential of the drain terminal of the third switching element S3 is as follows: Figure 17 In (b), it is shown by the solid line and continues to increase.

[0163] In addition, Figure 17 During the seventh period T17 shown in FIG. 1 , no current flows through the third switching element S3. Therefore, the current flowing into the drain terminal of the third switching element S3 is as follows: Figure 17 (c) is shown by the solid line, which is basically 0A. Figure 17 During the seventh period T17 shown, a current flows out from the source terminal of the first switching element S1 , and therefore a current flowing into the source terminal of the first switching element S1 becomes a negative current.

[0164] in addition, Figure 17 During the seventh period T17 shown in FIG. 1 , no current flows in the third switching element S3. Therefore, the loss caused by the through current flowing in the third switching element S3 is as follows: Figure 17 In (d), the solid line indicates 0W.

[0165] Figure 25 This shows that the AC generating circuit is supplied with Figure 16 and Figure 17 A diagram showing an example of the voltages applied to the power storage body, the first capacitor, and the second capacitor, the duty ratios of the first switching element, the second switching element, and the third switching element, the current supplied to the power storage body, and the losses generated in the first switching element, the second switching element, and the third switching element when the gate signal is shown.

[0166] Figure 25 (a) shows the change of the duty ratio of the first switching element S1, the second switching element S2 and the third switching element S3 over time. Specifically, Figure 25 In (a), the solid line shows the change of the duty ratio of the third switching element S3 over time. Figure 25 In (a), the dotted lines show the temporal changes in the duty ratios of the first switching element S1 and the second switching element S2.

[0167] The switching element control unit 62 of the second embodiment performs the following operations: Figure 25 The solid line in (a) shows a process in which the duty ratio of the third switching element S3 is increased from 0% to 33% at a constant rate. This process is an example of a process in which the duty ratio of the third switching element S3 is increased from 0% starting from an initial state in which the first switching element S1, the second switching element S2, and the third switching element S3 are in a non-energized state.

[0168] In addition, the switching element control unit 62 of the second embodiment performs the following operations: Figure 25 In (a), the dotted lines indicate a process of increasing the duty ratios of the first switching element S1 and the second switching element S2 from 0% to 100% at a constant rate.

[0169] Furthermore, the switching element control unit 62 of the second embodiment performs the following operations: Figure 25 In (a), the dotted lines indicate a process of reducing the duty ratios of the first and second switching elements S1 and S2 from 100% to 66% at the same rate as the rate at which the duty ratio of the third switching element S3 is reduced. Figure 25 As shown in (a), the process of decreasing the duty cycle of the third switching element S3 from 100% to 66% at a constant rate is started simultaneously. Furthermore, this process is an example of a process in which the duty cycles of the first switching element S1 and the second switching element S2 are decreased from 100% by the amount by which the duty cycle of the third switching element S3 is increased from an initial state in which the first switching element S1, the second switching element S2, and the third switching element S3 are in a non-energized state.

[0170] Figure 25 (b) shows that the AC generating circuit 61 is supplied with Figure 25 (a) shows the temporal change of the voltage applied to the power storage body 10, the first capacitor C1 or the second capacitor C2 in the case of a gate signal with a duty ratio shown in FIG. Figure 25 In (b), the solid line shows that the AC generating circuit 61 is supplied with Figure 25(a) shows the temporal change of the voltage applied to the power storage body 10 in the case of a gate signal with a duty ratio shown in FIG. Figure 25 In (b), the dotted line shows that the AC generating circuit 61 is supplied with Figure 25 (a) shows a temporal change in the voltage applied to the first capacitor C1 or the second capacitor C2 in the case of a gate signal with the duty ratio shown.

[0171] The amplitude of the voltage applied to the electricity storage body 10 is as follows: Figure 25 As shown by the solid line in (b), the duty cycle of the first switching element S1 and the second switching element S2 decreases and the duty cycle of the third switching element S3 increases. In addition, the amplitude of the voltage applied to the first capacitor C1 is as shown in FIG. Figure 25 As shown by the dotted line in (b), the duty cycle of the first switching element S1 and the second switching element S2 decreases and the duty cycle of the third switching element S3 increases. Similarly, the amplitude of the voltage applied to the second capacitor C2 is as follows: Figure 25 As shown by the dotted line in (b), the duty cycle of the first switching element S1 and the second switching element S2 decreases and the duty cycle of the third switching element S3 increases.

[0172] Figure 25 (c) shows that the AC generating circuit 61 is supplied with Figure 25 The current supplied to the power storage body 10 in the case of the gate signal with the duty ratio shown in (a). The current supplied to the power storage body 10 is as follows Figure 25 As shown in (c), the duty ratio of the first switching element S1 and the second switching element S2 decreases and the duty ratio of the third switching element S3 increases.

[0173] Figure 25 (d) shows that the AC generating circuit 61 is supplied with Figure 25 In the case of a gate signal with a duty ratio shown in (a), a loss occurs in the first switching element S1, the second switching element S2, or the third switching element S3. Specifically, Figure 25 In (d), the loss generated in the first switching element S1 or the second switching element S2 is shown by a solid line. Figure 25 In (d), the loss generated in the third switching element S3 is shown by a dotted line.

[0174] like Figure 25As shown by the dotted line in (d), the loss generated in the third switching element S3 increases as the amplitude of the current flowing through the power storage body 10 tends to become substantially constant, and becomes substantially constant after a predetermined time has passed since the amplitude of the current became substantially constant. In addition, the loss generated in the third switching element S3 is different from the loss generated in the third switching element S3 in the case of the comparative example, and does not become maximum in the middle of the increase. Moreover, these Figure 25 The same is true for the loss generated in the first switching element S1 and the loss generated in the second switching element S2 as shown by the solid line in (d).

[0175] The above describes the temperature increasing device 60 of the embodiment. From an initial state in which the first switching element S1, the second switching element S2, and the third switching element S3 are in a non-energized state, the temperature increasing device 60 increases the duty cycle of the first switching element S1, the second switching element S2, or the third switching element S3 from 0 percent. Furthermore, the temperature increasing device 60 decreases the duty cycle of the first switching element S1, the second switching element S2, or the third switching element S3 from 100 percent by the amount by which the duty cycle of the first switching element S1, the second switching element S2, or the third switching element S3 is increased from the initial state.

[0176] Thus, the temperature increasing device 60 controls the AC generating circuit 61 so that no through-current flows through the third switching element S3 during the reverse recovery time of the first diode D1 and the second diode D2. Therefore, the temperature increasing device 60 can reduce the loss in the third switching element S3 caused by such through-current.

[0177] In the above embodiment, the case where the power storage body 10 is a secondary battery is described as an example, but the present invention is not limited thereto. The power storage body 10 may be, for example, an electric double layer capacitor or an electrolytic capacitor.

[0178] Furthermore, in the above embodiment, the first switching element S1, the second switching element S2, and the third switching element S3 are described as metal oxide semiconductor power field effect transistors, but the present invention is not limited thereto. For example, at least one of the first switching element S1, the second switching element S2, and the third switching element S3 may be an insulated gate bipolar transistor (IGBT).

[0179] Furthermore, in the above-described embodiment, the case where the first diode D1 , the second diode D2 , and the third diode D3 are freewheeling diodes has been described as an example, but the present invention is not limited thereto.

[0180] For example, the first diode D1 may be a parasitic diode of the first switching element S1. In addition, for example, the second diode D2 may be a parasitic diode of the second switching element S2. Similarly, the third diode D3 may be a parasitic diode of the third switching element S3.

[0181] Moreover, when at least one of the first diode D1, the second diode D2 and the third diode D3 is a parasitic diode, the switching element control unit 62 of the first embodiment sets the length of the dead time to be shorter than a specified value, and adjusts it in a manner that can avoid generating a current exceeding a specified threshold.

[0182] While the embodiments of the present invention have been described above with reference to the accompanying drawings, the temperature increasing device, temperature increasing program, and temperature increasing method are not limited to the above-described embodiments, and various modifications, substitutions, combinations, and design changes may be added without departing from the spirit of the present invention.

[0183] The effects of the above-described embodiments of the present invention are merely examples of the effects described above. Therefore, the embodiments of the present invention can also achieve other effects that those skilled in the art can recognize from the description of the above-described embodiments in addition to the above-described effects.

Claims

1. A temperature increasing device, wherein: The AC generating circuit includes: a first capacitor having one terminal connected to a terminal of a power storage body; a first switching element connected to the other terminal of the first capacitor and a terminal of the power storage body; a second capacitor having one terminal connected to a terminal of the electricity storage body; a second switching element connected to a terminal of the power storage body and the other terminal of the second capacitor; and a third switching element connected to the other terminal of the first capacitor and the other terminal of the second capacitor, The temperature increasing device includes a switching element control unit that performs duty cycle control processing on the AC generating circuit. From an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from 0 percent, and the duty cycle of the other of the first switching element, the second switching element, and the third switching element is reduced from 100 percent, and the amount by which the duty cycle of the other is reduced from 100 percent is the amount by which the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from the initial state.

2. The temperature increasing device according to claim 1, wherein: The switching element control unit executes the duty ratio control process for the AC generating circuit in which at least one of the first switching element, the second switching element, and the third switching element has a parasitic diode.

3. The temperature increasing device according to claim 2, wherein: The switching element control unit sets the length of the dead time provided between the following two states to be shorter than a predetermined value, and to a length that can avoid the generation of a current exceeding a predetermined threshold value, The two states are: a state in which the first and second switching elements are in a conducting state and the third switching element is in a non-conducting state; and a state in which the first and second switching elements are in a non-conducting state and the third switching element is in a conducting state.

4. The temperature increasing device according to claim 1 or 2, wherein: The switching element control unit executes the duty ratio control process for the AC generating circuit in which a freewheeling diode is connected to at least one of the first switching element, the second switching element, and the third switching element.

5. The temperature increasing device according to claim 4, wherein: The switching element control unit sets the length of the dead time provided between the following two states to be shorter than a predetermined value, and to a length that can avoid the generation of a current exceeding a predetermined threshold value, The two states are: a state in which the first and second switching elements are in a conducting state and the third switching element is in a non-conducting state; and a state in which the first and second switching elements are in a non-conducting state and the third switching element is in a conducting state.

6. The temperature increasing device according to any one of claims 1 to 3, wherein: The switching element control unit executes the duty ratio control process for the AC generating circuit in which at least one of the first switching element, the second switching element, and the third switching element is an insulated gate bipolar transistor or a metal oxide film semiconductor power field effect transistor.

7. A storage medium, wherein: The AC generating circuit includes: a first capacitor having one terminal connected to a terminal of a power storage body; a first switching element connected to the other terminal of the first capacitor and a terminal of the power storage body; a second capacitor having one terminal connected to a terminal of the electricity storage body; a second switching element connected to a terminal of the power storage body and the other terminal of the second capacitor; and a third switching element connected to the other terminal of the first capacitor and the other terminal of the second capacitor, The storage medium stores a temperature raising program that enables a computer to implement a switching element control function, wherein the switching element control function performs a duty cycle control process on the AC generating circuit. From an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from 0 percent, and the duty cycle of the other of the first switching element, the second switching element, and the third switching element is reduced from 100 percent, and the amount by which the duty cycle of the other is reduced from 100 percent is the amount by which the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from the initial state.

8. A method for increasing temperature, wherein: The AC generating circuit includes: a first capacitor having one terminal connected to a terminal of a power storage body; a first switching element connected to the other terminal of the first capacitor and a terminal of the power storage body; a second capacitor having one terminal connected to a terminal of the electricity storage body; a second switching element connected to a terminal of the power storage body and the other terminal of the second capacitor; and a third switching element connected to the other terminal of the first capacitor and the other terminal of the second capacitor, The temperature raising method performs duty cycle control processing on the AC generating circuit: From an initial state in which the first switching element, the second switching element, and the third switching element are in a non-energized state, the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from 0 percent, and the duty cycle of the other of the first switching element, the second switching element, and the third switching element is reduced from 100 percent, and the amount by which the duty cycle of the other is reduced from 100 percent is the amount by which the duty cycle of one of the first switching element, the second switching element, and the third switching element is increased from the initial state.

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