Voltage conversion device and electric vehicle

Abstract

To provide a technique that can prevent the occurrence of out-of-resonance.SOLUTION: A primary-side circuit may comprise a primary-side coil forming part of a transformer, an exciting inductance connected in parallel with the primary-side coil, a first resonance tank circuit connected in series with the primary-side coil, a second resonance tank circuit connected in series with the primary-side coil and in parallel with the first resonance tank circuit, and a switch for changing between the first resonance tank circuit and the second resonance tank circuit. The first resonance tank circuit may comprise a first leakage inductance connected in series with the primary-side coil, and a first capacitor connected in series with the first leakage inductance. The second resonance tank circuit may comprise a second leakage inductance connected in series with the primary-side coil, and a second capacitor connected in series with the second leakage inductance.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The technology disclosed in this specification relates to a voltage conversion device and an electric vehicle. [Background technology]

[0002] Patent Document 1 discloses a voltage conversion device that converts an input voltage into an output voltage and applies it to a load. The voltage conversion device of Patent Document 1 includes a primary circuit to which an input voltage is input, a secondary circuit that outputs an output voltage to be applied to the load, and a transformer that transmits power from the primary circuit to the secondary circuit. The primary circuit includes a primary coil that constitutes a part of the transformer, an excitation inductance connected in parallel with the primary coil, a leakage inductance connected in series with the primary coil, and a capacitor connected in series with the leakage inductance. The secondary circuit includes a secondary coil that constitutes a part of the transformer, and a rectifying element arranged between the secondary coil and the load. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2023-79300 Summary of the Invention [Problem to be solved by the invention]

[0004] In the voltage conversion device of Patent Document 1, off-resonance may occur when the resistance of the load to which the output voltage is applied is small relative to the capacity of the resonance capacitor in the primary circuit. This specification provides a technology that can suppress the occurrence of off-resonance. [Means for solving the problem]

[0005] In a first aspect of the present technology, a voltage conversion device that converts an input voltage into an output voltage and applies the output voltage to a load may include a primary circuit to which the input voltage is input, a secondary circuit that outputs an output voltage to be applied to the load, and a transformer that transmits power from the primary circuit to the secondary circuit. The primary circuit may include a primary coil constituting a part of the transformer, an excitation inductance connected in parallel with the primary coil, a first resonant tank circuit connected in series with the primary coil, a second resonant tank circuit connected in series with the primary coil and in parallel with the first resonant tank circuit, and a switch that switches between the first resonant tank circuit and the second resonant tank circuit. The secondary circuit may include a secondary coil constituting a part of the transformer, and a rectifying element arranged between the secondary coil and the load. The first resonant tank circuit may include a first leakage inductance connected in series with the primary coil, and a first capacitor connected in series with the first leakage inductance. The second resonant tank circuit may include a second leakage inductance connected in series with the primary coil, and a second capacitor connected in series with the second leakage inductance. A resonant frequency (f1) of the following formula (1) based on an inductance (Lr1) of the first leakage inductance and a capacitance (Cr1) of the first capacitor may be equal to a resonant frequency (f2) of the following formula (2) based on an inductance (Lr2) of the second leakage inductance and a capacitance (Cr2) of the second capacitor.

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[0006] With this configuration, by providing the first and second resonant tank circuits, it is possible to switch to a capacitor with an appropriate capacitance for the magnitude of the resistance of the load to which the output voltage is applied without varying the resonant frequency determined by the leakage inductance and capacitor for resonance in the primary circuit, thereby making it possible to suppress the occurrence of resonance loss.

[0007] In a second aspect, in the first aspect described above, the Q value (Q1) of the following equation (3) based on the inductance (Lr1) of the first leakage inductance, the capacitance (Cr1) of the first capacitor, and the resistance (R) of the load may be different from the Q value (Q2) of the following equation (4) based on the inductance (Lr2) of the second leakage inductance, the capacitance (Cr2) of the second capacitor, and the resistance (R) of the load.

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[0008] According to this configuration, it is possible to suppress the occurrence of off-resonance.

[0009] In a third aspect, in the first or second aspect above, the voltage conversion device may further include a first voltage sensor that detects a voltage applied to the first capacitor, and a second voltage sensor that detects a voltage applied to the second capacitor.

[0010] According to this configuration, for example, the circuit to be used can be switched from the first resonant tank circuit to the second resonant tank circuit based on the detection value of the first voltage sensor. Also, the circuit to be used can be switched from the second resonant tank circuit to the first resonant tank circuit based on the detection value of the second voltage sensor. Therefore, by switching between the first resonant tank circuit and the second resonant tank circuit based on the detection values ​​of the first voltage sensor and the second voltage sensor, it is possible to prevent the occurrence of out-of-resonance.

[0011] In a fourth aspect of the present technology, an electric vehicle may include the voltage conversion device according to any one of the first to third aspects. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a circuit diagram of a voltage conversion device according to an embodiment. [Diagram 2] FIG. 11 is a circuit diagram of a voltage conversion device according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] A voltage conversion device of an embodiment will be described with reference to the drawings. As shown in Fig. 1, a voltage conversion device 2 of the embodiment is connected to a power source 4 and a load 6. The voltage conversion device 2 is a device that converts an input voltage input from the power source 4 into an output voltage (e.g., stepping down or stepping up) and applies it to the load 6. The voltage conversion device 2 is mounted on, for example, an electric vehicle (e.g., an electric car or a hybrid car).

[0014] The voltage conversion device 2 may be called, for example, a resonant converter or an LLC converter. The voltage conversion device 2 in the embodiment is a half-bridge converter, but may be a full-bridge converter in a modified example. The type of the voltage conversion device 2 is not particularly limited.

[0015] The power source 4 connected to the input side of the voltage conversion device 2 is, for example, a DC power source such as a lithium ion battery or a nickel-metal hydride battery. In a modified example, the power source 4 may be configured to convert the voltage of an AC commercial power source into a DC voltage and input it to the voltage conversion device 2. The load 6 connected to the output side of the voltage conversion device 2 is, for example, a resistance component such as a motor. The types of the power source 4 and the load 6 are not particularly limited.

[0016] The voltage conversion device 2 of the embodiment includes a primary side circuit 10, a secondary side circuit 40, a transformer 50 configured between the primary side circuit 10 and the secondary side circuit 40, and a control unit 100. The voltage conversion device 2 of the embodiment is an isolated converter in which the primary side circuit 10 and the secondary side circuit 40 are insulated from each other.

[0017] A primary side circuit 10 of the voltage conversion device 2 is connected to a power source 4. The primary side circuit 10 includes a first switching element 12, a second switching element 14, a smoothing capacitor 52, a primary side coil 16, an exciting inductance 18, a first resonant tank circuit 20, and a second resonant tank circuit 30.

[0018] The first switching element 12 and the second switching element 14 are transistors such as, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The voltage conversion device 2 converts an input voltage from a power source 4 into an output voltage to a load 6 by periodically switching the first switching element 12 and the second switching element 14 on and off alternately.

[0019] In a modified example, the voltage conversion device 2 may include a diode connected in anti-parallel to the first switching element 12 and a capacitor connected in parallel to the first switching element 12. The voltage conversion device 2 may also include a diode connected in anti-parallel to the second switching element 14 and a capacitor connected in parallel to the second switching element 14.

[0020] The smoothing capacitor 52 of the primary side circuit 10 is connected in parallel to the first switching element 12 and the second switching element 14. The primary side coil 16 of the primary side circuit 10 constitutes a transformer 50 together with the secondary side coil 42 of the secondary side circuit 40. The voltage conversion device 2 transmits power of the primary side circuit 10 to the secondary side circuit 40 via the transformer 50. The exciting inductance 18 of the primary side circuit 10 is connected in parallel to the primary side coil 16.

[0021] The first resonant tank circuit 20 is connected in series with the primary coil 16. The first resonant tank circuit 20 is also connected in series with the magnetizing inductance 18. The first resonant tank circuit 20 includes a first leakage inductance 22, a first capacitor 24, and a first circuit switch 26.

[0022] The primary coil 16, the first leakage inductance 22, the first capacitor 24, and the first circuit switch 26 are connected in series. Also, the excitation inductance 18, the first leakage inductance 22, the first capacitor 24, and the first circuit switch 26 are connected in series.

[0023] The second resonant tank circuit 30 is connected in parallel with the first resonant tank circuit 20. The second resonant tank circuit 30 is connected in series with the primary coil 16. The second resonant tank circuit 30 is also connected in series with the magnetizing inductance 18. The second resonant tank circuit 30 includes a second leakage inductance 32, a second capacitor 34, and a second circuit switch 36.

[0024] The primary coil 16, the second leakage inductance 32, the second capacitor 34, and the second circuit switch 36 are connected in series. The excitation inductance 18, the second leakage inductance 32, the second capacitor 34, and the second circuit switch 36 are connected in series.

[0025] For the first resonant tank circuit 20 and the second resonant tank circuit 30 connected in parallel, the inductance (Lr1) of the first leakage inductance 22 and the inductance (Lr2) of the second leakage inductance 32 have different values. For example, the inductance (Lr1) of the first leakage inductance 22 is larger than the inductance (Lr2) of the second leakage inductance 32. In addition, the capacitance (Cr1) of the first capacitor 24 and the capacitance (Cr2) of the second capacitor 34 have different values. For example, the capacitance (Cr1) of the first capacitor 24 is smaller than the capacitance (Cr2) of the second capacitor 34.

[0026] The product (Lr1×Cr1) of the inductance (Lr1) of the first leakage inductance 22 and the capacitance (Cr1) of the first capacitor 24 is equal to the product (Lr2×Cr2) of the inductance (Lr2) of the second leakage inductance 32 and the capacitance (Cr2) of the second capacitor 34.

[0027] A first resonant frequency (f1) due to the inductance (Lr1) of the first leakage inductance 22 and the capacitance (Cr1) of the first capacitor 24 is expressed by the following formula (1). A second resonant frequency (f2) due to the inductance (Lr2) of the second leakage inductance 32 and the capacitance (Cr2) of the second capacitor 34 is expressed by the following formula (2). The first resonant frequency (f1) and the second resonant frequency (f2) are equal in value.

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[0028] The Q value (Q1) of the inductance (Lr1) of the first leakage inductance 22, the capacitance (Cr1) of the first capacitor 24, and the resistance (R) of the load 6 is expressed by the following formula (3). The Q value (Q2) of the inductance (Lr2) of the second leakage inductance 32, the capacitance (Cr2) of the second capacitor 34, and the resistance (R) of the load 6 is expressed by the following formula (4). Q1 and Q2 are different values.

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[0029] 1, the secondary circuit 40 of the voltage conversion device 2 is connected to a load 6. The secondary circuit 40 includes a secondary coil 42, a plurality of rectifier diodes 44a-44d (examples of rectifier elements), and a smoothing capacitor 54.

[0030] The secondary coil 42 of the secondary circuit 40 constitutes a transformer 50 together with the primary coil 16. A current is generated in the secondary circuit 40 by power transmitted to the secondary circuit 40 via the transformer 50. A plurality of rectifier diodes 44a-44d rectify the current in the secondary circuit 40. In a modified example, a transistor may be used instead of a diode as a rectifier element for rectifying the current in the secondary circuit 40. A smoothing capacitor 54 of the secondary circuit 40 is connected in parallel with the load 6.

[0031] The control unit 100 includes, for example, a CPU, a ROM, and a RAM, and executes a predetermined control or process related to the voltage conversion device 2 according to a predetermined program. The control unit 100 can switch between the first resonant tank circuit 20 and the second resonant tank circuit 30. The control unit 100 turns on / off the first circuit switch 26 and the second circuit switch 36 according to a predetermined program. The control unit 100 can control the first circuit switch 26 and the second circuit switch 36 to switch between a first state in which the first resonant tank circuit 20 is conductive and the second resonant tank circuit 30 is not conductive, and a second state in which the second resonant tank circuit 30 is conductive and the first resonant tank circuit 20 is not conductive. When the first circuit switch 26 is on, the control unit 100 does not turn on the second circuit switch 36. On the other hand, when the second circuit switch 36 is on, the control unit 100 does not turn on the first circuit switch 26.

[0032] (effect) The voltage converter 2 of the embodiment has been described above. As described above, the primary circuit 10 of the voltage converter 2 includes the primary coil 16 constituting a part of the transformer 50, the excitation inductance 18 connected in parallel with the primary coil 16, the first resonant tank circuit 20 connected in series with the primary coil 16, the second resonant tank circuit 30 connected in series with the primary coil 16 and in parallel with the first resonant tank circuit 20, and switches (first circuit switch 26 and second circuit switch 36) for switching between the first resonant tank circuit 20 and the second resonant tank circuit 30. The first resonant tank circuit 20 includes a first leakage inductance 22 connected in series with the primary coil 16, and a first capacitor 24 connected in series with the first leakage inductance 22. The second resonant tank circuit 30 includes a second leakage inductance 32 connected in series with the primary coil 16, and a second capacitor 34 connected in series with the second leakage inductance 32. The resonant frequency (f1) formed by the inductance (Lr1) of the first leakage inductance and the capacitance (Cr1) of the first capacitor 24 and the resonant frequency (f2) formed by the inductance (Lr2) of the second leakage inductance and the capacitance (Cr2) of the second capacitor 34 are equal in value.

[0033] According to this configuration, by providing the first resonant tank circuit 20 and the second resonant tank circuit 30, it is possible to switch to capacitors 24, 34 with appropriate capacitances for the magnitude of the resistance of the load 6 to which the output voltage is applied, without varying the resonant frequency (f1, f2) defined by the leakage inductances 22, 32 for resonance and the capacitors 24, 34 of the primary side circuit 10. This makes it possible to suppress the occurrence of out-of-resonance.

[0034] In addition, the Q value (Q1) formed by the inductance (Lr1) of the first leakage inductance, the capacitance (Cr1) of the first capacitor 24, and the resistance (R) of the load 6 is different from the Q value (Q2) formed by the inductance (Lr2) of the second leakage inductance, the capacitance (Cr2) of the second capacitor 34, and the resistance (R) of the load 6.

[0035] (Modification) As shown in FIG. 2, the modified voltage conversion device 2 includes a first voltage sensor 60 that detects the voltage applied to the first capacitor 24 of the first resonant tank circuit 20, and a second voltage sensor 70 that detects the voltage applied to the second capacitor 34 of the second resonant tank circuit 30.

[0036] The first voltage sensor 60 includes a first comparator 62 that determines whether or not the voltage applied to the first capacitor 24 is equal to or greater than a predetermined first reference voltage. The first comparator 62 is turned on when the voltage applied to the first capacitor 24 is equal to or greater than the first reference voltage, and is turned off when the voltage applied to the first capacitor 24 is less than the first reference voltage. Information on the detection value by the first voltage sensor 60 is transmitted to the control unit 100. In another modified example, the first voltage sensor 60 may be configured to directly detect the voltage applied to the first capacitor 24 without passing through the first comparator 62.

[0037] The second voltage sensor 70 includes a second comparator 72 that determines whether the voltage applied to the second capacitor 34 is equal to or greater than a predetermined second reference voltage. The second comparator 72 is turned on when the voltage applied to the second capacitor 34 is equal to or greater than the second reference voltage, and is turned off when the voltage applied to the second capacitor 34 is less than the second reference voltage. Information on the detection value by the second voltage sensor 70 is transmitted to the control unit 100. In another modified example, the second voltage sensor 70 may be configured to directly detect the voltage applied to the second capacitor 34 without passing through the second comparator 72.

[0038] In the voltage conversion device 2, resonance loss may occur when the relationship between the voltage (Vcr) applied to the capacitors 24, 34 of the primary circuit 10, the input voltage (Vin), the inductance (Lm) of the excitation inductance 18, the inductance (Lr) of the leakage inductances 22, 32, and the output voltage (Vout) of the secondary circuit 40 does not satisfy the following equation (5).

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[0039] The control unit 100 controls the first circuit switch 26 and the second circuit switch 36 so that equation (5) is satisfied. For example, when the first comparator 62 is turned on, the control unit 100 turns off the first circuit switch 26 and turns on the second circuit switch 36. Also, when the second comparator 72 is turned on, the control unit 100 turns off the second circuit switch 36 and turns on the first circuit switch 26.

[0040] The above describes the modified voltage conversion device 2. As described above, the modified voltage conversion device 2 includes the first voltage sensor 60 that detects the voltage applied to the first capacitor 24 and the second voltage sensor 70 that detects the voltage applied to the second capacitor 34.

[0041] According to this configuration, for example, the circuit to be used can be switched from the first resonant tank circuit 20 to the second resonant tank circuit 30 based on the detection value of the first voltage sensor 60. Also, the circuit to be used can be switched from the second resonant tank circuit 30 to the first resonant tank circuit 20 based on the detection value of the second voltage sensor 70. Therefore, by switching between the first resonant tank circuit 20 and the second resonant tank circuit 30 based on the detection values ​​of the first voltage sensor 60 and the second voltage sensor 70, it is possible to prevent the occurrence of out-of-resonance.

[0042] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of these objectives is itself technically useful. [Explanation of symbols]

[0043] 2: voltage conversion device, 4: power supply, 6: load, 10: primary side circuit, 12: first switching element, 14: second switching element, 16: primary side coil, 18: excitation inductance, 20: first resonant tank circuit, 22: first leakage inductance, 24: first capacitor, 26: first circuit switch, 30: second resonant tank circuit, 32: second leakage inductance, 34: second capacitor, 36: second circuit switch, 40: secondary side circuit, 42: secondary side coil, 44a-44d: rectifier diodes, 50: transformer, 60: first voltage sensor, 62: first comparator, 70: second voltage sensor, 72: second comparator, 100: control unit

Claims

1. A voltage conversion device that converts an input voltage into an output voltage and applies the output voltage to a load, a primary side circuit to which the input voltage is input; a secondary side circuit that outputs the output voltage to be applied to the load; a transformer that transmits power from the primary side circuit to the secondary side circuit, the primary side circuit includes a primary side coil constituting a part of the transformer, an excitation inductance connected in parallel with the primary side coil, a first resonant tank circuit connected in series with the primary side coil, a second resonant tank circuit connected in series with the primary side coil and in parallel with the first resonant tank circuit, and a switch for switching between the first resonant tank circuit and the second resonant tank circuit; the secondary circuit includes a secondary coil constituting a part of the transformer, and a rectifying element disposed between the secondary coil and the load; the first resonant tank circuit comprises a first leakage inductance connected in series with the primary coil and a first capacitor connected in series with the first leakage inductance; the second resonant tank circuit comprises a second leakage inductance connected in series with the primary coil and a second capacitor connected in series with the second leakage inductance; A voltage conversion device, wherein a resonant frequency (f1) of the following equation (1) based on the inductance (Lr1) of the first leakage inductance and the capacitance (Cr1) of the first capacitor and a resonant frequency (f2) of the following equation (2) based on the inductance (Lr2) of the second leakage inductance and the capacitance (Cr2) of the second capacitor are equal in value.

2. 2. The voltage conversion device according to claim 1, A Q value (Q1) of the following equation (3) based on the inductance (Lr1) of the first leakage inductance, the capacitance (Cr1) of the first capacitor, and the resistance (R) of the load: A voltage conversion device, wherein a Q value (Q2) of the following equation (4) based on the inductance (Lr2) of the second leakage inductance, the capacitance (Cr2) of the second capacitor, and the resistance (R) of the load is different from one another.

3. 3. The voltage conversion device according to claim 1, a first voltage sensor that detects a voltage applied to the first capacitor; a second voltage sensor configured to detect a voltage applied to the second capacitor.

4. An electric vehicle comprising the voltage conversion device (2) according to claim 1 or 2.

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