Power converter
The power conversion device addresses eddy current induction and reduced magnetic coupling by connecting primary and secondary transformers to a common potential, enhancing efficiency and safety.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- HITACHI LTD
- Filing Date
- 2022-07-22
- Publication Date
- 2026-06-03
AI Technical Summary
High-frequency high-voltage transformers experience significant eddy current induction and reduced magnetic coupling due to the presence of a shield plate, leading to resistance loss and inefficiency.
A power conversion device with a primary transformer and secondary transformer connected to a common potential, eliminating the need for a shield plate and forming a closed circuit to prevent eddy currents and enhance magnetic coupling.
Prevents eddy current generation and improves magnetic coupling, reducing losses and simplifying the magnetic design while ensuring safety in case of short circuits.
Smart Images
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Abstract
Description
Technical Field
[0006] , ,
[0005] ,
[0001] The present disclosure relates to a power conversion device.
Background Art
[0002] Conventionally, high-frequency high-voltage transformers have been known (see, for example, Patent Document 1, paragraphs 0002-0003). In a high-frequency high-voltage transformer, generally, a shield plate, which is a thin conductor plate at ground potential called a creepage prevention plate, is provided between the primary winding and the secondary winding of the transformer for the purpose of preventing an abnormal voltage generated in one winding from transferring to the other winding.
[0003] In such a transformer, the primary winding, the shield plate, and the secondary winding are coupled by capacitance. In this state, when an abnormal voltage is generated in the primary winding or the secondary winding for some reason, the abnormal voltage is transmitted to the shield plate through the capacitance and grounded, and does not transfer to the other winding.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] In the transformer as described above, magnetic flux concentrates between the primary winding and the secondary winding. That is, since the leakage magnetic flux is large between the primary winding and the secondary winding, when a shield plate is disposed between the primary winding and the secondary winding, eddy currents are induced in the shield plate. Particularly, in a high-frequency transformer, the induction of eddy currents is remarkably manifested and resistance loss occurs. Further, due to the shielding effect of the shield plate, the magnetic coupling between the primary winding and the secondary winding is reduced.
[0006] The present disclosure provides a power conversion device capable of preventing the generation of eddy currents and improving magnetic coupling. [Means for solving the problem]
[0007] One aspect of the present disclosure is a power conversion device comprising: a primary transformer to which a primary AC voltage is input from a primary circuit; and a secondary transformer to which a secondary AC voltage lower than the primary AC voltage is output to a secondary circuit, wherein the primary transformer has a primary winding to which the primary AC voltage is input and a primary secondary winding to which power is transmitted from the primary winding; the secondary transformer has a secondary primary winding that forms a closed circuit together with the primary secondary winding and a secondary secondary winding to which power is transmitted from the secondary primary winding to output the secondary AC voltage, and the primary circuit and the closed circuit are connected to a common potential. [Effects of the Invention]
[0008] According to one aspect of the present disclosure, it is possible to provide a power conversion device that can prevent the generation of eddy currents and improve magnetic coupling. [Brief explanation of the drawing]
[0009] [Figure 1] A circuit diagram showing one embodiment of the power conversion device relating to this disclosure. [Figure 2] A circuit diagram showing a modified example 1 of the power converter in Figure 1. [Figure 3] A circuit diagram showing a modified example 2 of the power converter in Figure 1. [Figure 4] A circuit diagram showing a modified example 3 of the power converter shown in Figure 1. [Figure 5] A schematic cross-sectional view showing an example configuration of the power conversion device in Figure 1. [Modes for carrying out the invention]
[0010] Hereinafter, an embodiment of the power conversion device according to this disclosure will be described with reference to the drawings.
[0011] Figure 1 is a circuit diagram showing one embodiment of the power converter according to the present disclosure. The power converter 100 of this embodiment is a small solid-state transformer (SST) applicable to charging systems for mobile devices such as electric vehicles and drones. The power converter 100 of this embodiment enables, for example, switching between rapid charging and charging of multiple devices, as well as miniaturization, weight reduction, space saving, and improved reliability of the charging system.
[0012] The power converter 100 is a high-frequency transformer comprising, for example, a primary transformer 110 to which a primary AC voltage V1 is input from a primary circuit 10, and a secondary transformer 120 to which a secondary AC voltage V2 lower than the primary AC voltage V1 is output to a secondary circuit 20.
[0013] The primary transformer 110 of the power converter 100 has a primary winding 111 to which the primary AC voltage V1 from the primary circuit 10 is input, and a primary secondary winding 112 to which power is transmitted from the primary winding 111. In the primary transformer 110, the primary winding 111 is a high-voltage winding, and the primary secondary winding 112 is a low-voltage winding.
[0014] The secondary transformer 120 of the power converter 100 has a secondary primary winding 121 that forms a closed circuit 130 together with the primary secondary winding 112, and a secondary secondary winding 122 that receives power from the secondary primary winding 121 and outputs a secondary AC voltage V2. In the secondary transformer 120, both the secondary primary winding 121 and the secondary secondary winding 122 are low-voltage windings.
[0015] The input terminals of the primary circuit 10 are connected to, for example, a 6.6kV high-voltage AC power source (not shown). The primary circuit 10 includes, for example, a primary AC / DC converter 11 connected to the primary transformer 110 of the power converter 100. The AC power supplied from the AC power source (not shown) to the input terminals of the primary circuit 10 is converted to DC power by the AC / DC converter (not shown) and input to the primary AC / DC converter 11. The primary AC / DC converter 11 converts the input DC power back to AC power and supplies it to a pair of input terminals of the primary transformer 110 of the power converter 100.
[0016] More specifically, one end and the other end of the primary winding 111 that constitutes the primary transformer 110 of the power converter 100 are connected to one of the pair of output terminals of the primary AC / DC converter 11 that outputs a primary AC voltage V1. The primary AC / DC converter 11 has, for example, four switching elements connected in an H-bridge configuration and an FWD (Free Wheeling Diode) connected in antiparallel to these switching elements. The switching elements are, for example, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).
[0017] The pair of input terminals of the secondary circuit 20 are connected to one end and the other end of the secondary winding 122 that constitutes the secondary transformer 120 of the power converter 100. The secondary circuit 20 has, for example, a secondary AC / DC converter 21 connected to one end and the other end of the secondary winding 122 that outputs a secondary AC voltage V2 that is lower than the primary AC voltage V1.
[0018] The secondary AC / DC converter 21 of the secondary circuit 20 converts the AC power input from the secondary winding 122 of the power converter 100 into DC power and transmits it to the charging target, such as an electric vehicle, via switches and repeaters (not shown in the figure). The secondary AC / DC converter 21 has four switching elements connected in an H-bridge configuration, similar to the primary AC / DC converter 11, and FWDs connected in antiparallel to these switching elements.
[0019] The power conversion device 100 has a closed circuit 130 formed by a primary secondary winding 112 of a primary transformer 110 and a secondary primary winding 121 of a secondary transformer 120. More specifically, the closed circuit 130 is formed by connecting one end of the primary secondary winding 112 and one end of the secondary primary winding 121, and connecting the other end of the primary secondary winding 112 and the other end of the secondary primary winding 121. The power conversion device 100 of the present embodiment is characterized in that the primary circuit 10 and the closed circuit 130 are connected to a common potential. In the example shown in FIG. 1, the common potential to which the primary circuit 10 and the closed circuit 130 are connected is the ground potential.
[0020] Hereinafter, the operation of the power conversion device 100 of the present embodiment will be described.
[0021] As described in the above-mentioned Patent Document 1, in a conventional high-frequency transformer provided with a shield plate, which is a conductor thin plate at the ground potential called a mixing prevention plate, between the primary winding and the secondary winding, eddy currents are induced in the shield plate and losses occur. Furthermore, the magnetic coupling between the primary winding and the secondary winding is reduced due to the shielding effect of the shield plate.
[0022] On the other hand, as described above, the power conversion device 100 of the present embodiment includes a primary transformer 110 to which a primary AC voltage V1 is input from the primary circuit 10, and a secondary transformer 120 that outputs a secondary AC voltage V2 lower than the primary AC voltage V1 to the secondary circuit 20. The primary transformer 110 has a primary primary winding 111 to which the primary AC voltage V1 is input, and a primary secondary winding 112 through which power is transmitted from the primary primary winding 111. The secondary transformer 120 has a secondary primary winding 121 that forms a closed circuit 130 together with the primary secondary winding 112, and a secondary secondary winding 122 through which power is transmitted from the secondary primary winding 121 and outputs the secondary AC voltage V2. In the power conversion device 100 of the present embodiment, the primary circuit 10 and the closed circuit 130 are connected to a common potential.
[0023] With this configuration, even if a short circuit occurs between the primary winding 111 and the secondary winding 112 of the primary transformer 110 for some reason, the high-voltage current that flowed from the primary circuit 10 to the closed circuit 130 will flow from the closed circuit 130 to the common potential with the primary circuit 10. Therefore, even if a short circuit occurs between the primary winding 111 and the secondary winding 112 of the primary transformer 110, it is possible to prevent high-voltage current from flowing from the primary circuit 10 to the secondary circuit 20. Furthermore, the power converter 100 of this embodiment does not use a shielding plate as a short circuit prevention plate, and the closed circuit 130 is formed by the primary secondary winding 112 of the primary transformer 110 and the secondary primary winding 121 of the secondary transformer 120. This closed circuit 130 is not affected by high-frequency magnetic flux and does not generate eddy currents. Therefore, the power converter 100 of this embodiment can reduce losses compared to conventional transformers that use a shielding plate as a contact prevention plate. Furthermore, compared to conventional transformers that use a shielding plate, the power converter 100 of this embodiment has a higher coupling between the primary transformer 110 and the secondary transformer 120, which simplifies the magnetic design.
[0024] Furthermore, in the power converter 100 of this embodiment, the common potential to which the primary circuit 10 and the closed circuit 130 are connected is the ground potential. This configuration further improves safety in the event of a short circuit between the primary winding 111 and the secondary winding 112 of the primary transformer 110. It also makes it easier to connect the primary circuit 10 and the closed circuit 130 to a common potential. Note that the common potential to which the primary circuit 10 and the closed circuit 130 are connected is not limited to the ground potential.
[0025] Figure 2 is a circuit diagram showing a modified example 1 of the power converter 100 shown in Figure 1. In the modified example 1 shown in Figure 2, the primary circuit 10 includes, for example, an AC power supply 12, a power cable 14 that supplies AC power from the AC power supply 12 to the AC / DC converter 13, and a shield 15 that covers the power cable 14. The AC / DC converter 13 converts the AC power supplied from the AC power supply 12 via the power cable 14 into DC power and outputs it to the primary AC / DC converter 11.
[0026] In the modified example shown in Figure 2, the ground wire of the power cable 14 of the primary circuit 10 is connected to the shield 15 covering the power cable 14 via a capacitive component, and the shield 15 is connected to ground, which is the reference potential for the operation of the primary circuit 10. The closed circuit 130 is connected to the ground of the primary circuit 10, for example, via wiring. That is, the primary circuit 10 and the closed circuit 130 are connected to the ground of the primary circuit 10 as a common potential, for example. A power converter 100 with such a configuration can achieve the same effects as the power converter 100 according to the above embodiment shown in Figure 1.
[0027] Figure 3 is a circuit diagram showing a modified example 2 of the power converter 100 shown in Figure 1. The power converter 100 according to this modified example differs from the power converter 100 shown in Figure 1 in that the midpoint of the primary circuit 10 and the primary secondary winding 112 of the primary transformer 110 are connected to a common potential, which is the ground potential. Note that the midpoint of the primary circuit 10 and the primary secondary winding 112 may be connected to a common potential other than the ground potential, for example, as in the modified example 2 shown in Figure 2.
[0028] In the power converter 100 according to this modified example, the primary circuit 10 and the midpoint of the primary secondary winding 112 of the primary transformer 110 are connected to a common potential. This configuration makes it possible to more reliably prevent high-voltage current from flowing from the primary circuit 10 to the secondary primary winding 121 of the secondary transformer 120 in the event of a short circuit between the primary primary winding 111 and the primary secondary winding 112 of the primary transformer 110. Furthermore, it is possible to suppress an increase in the number of components in the closed circuit 130.
[0029] Figure 4 is a circuit diagram showing a third modified example of the power converter 100 shown in Figure 1. The power converter 100 according to this modified example differs from the power converter 100 shown in Figure 1 in that the closed circuit 130 has a capacitor 131 connected in series with the primary-side secondary winding 112 and the secondary-side primary winding 121.
[0030] More specifically, the closed circuit 130 includes, for example, a primary-side secondary winding 112 and a secondary-side primary winding 121, and first and second wirings connecting one end of these windings to each other and the other end to each other, respectively. A capacitor 131 is provided in the middle of the first wiring, and the middle of the second wiring is connected to a common potential with the primary-side circuit 10.
[0031] With this configuration, the power converter 100 of this modified example not only strengthens the prevention of contact between the high-voltage primary winding 111 and the low-voltage secondary winding 112 of the primary transformer 110, but also makes it possible to suppress magnetic bias.
[0032] Figure 5 is a schematic cross-sectional view showing an example configuration of the power converter 100 of Figure 1. In the example shown in Figure 5, the power converter 100 further comprises a core 140 that constitutes a primary transformer 110 and a secondary transformer 120. The core 140 has a primary core 141 that constitutes the primary transformer 110 and a secondary core 142 that constitutes the secondary transformer 120. The primary core 141 and the secondary core 142 are separated, and a predetermined air gap G is formed between the primary core 141 and the secondary core 142.
[0033] The primary secondary winding 112 of the low-voltage side of the primary transformer 110 is wound around the outer circumference of the primary core 141, and the primary primary winding 111 of the high-voltage side of the primary transformer 110 is wound around the outer circumference of the primary secondary winding 112. In addition, the secondary primary winding 121 of the secondary transformer 120, which together with the primary secondary winding 112 of the primary transformer 110 to form a closed circuit 130, is wound around the outer circumference of the secondary core 142. Furthermore, the secondary secondary winding 122 of the low-voltage side of the secondary transformer 120, which is connected to the secondary circuit 20, is wound around the outer circumference of the secondary primary winding 121.
[0034] The power converter 100, for example, by adopting the configuration shown in Figure 5, can enhance the prevention of contact between the high-voltage primary winding 111 of the primary circuit 10 and the low-voltage secondary primary winding 121 and secondary winding 122 of the secondary transformer 120, while simultaneously suppressing a decrease in magnetic coupling.
[0035] While embodiments of the power conversion device relating to this disclosure have been described in detail above using drawings, the specific configuration is not limited to these embodiments, and any design changes, etc., that do not depart from the gist of this disclosure are also included in this disclosure. [Explanation of Symbols]
[0036] 10 Primary circuit 20 Secondary circuit 100 Power converter 110 Primary transformer 111 Primary winding on the primary side 112 Primary side secondary winding 120 Secondary transformer 121 Secondary side primary winding 122 Secondary winding 130 Closed circuit 131 Capacitor V1 Primary AC voltage V2 Secondary AC voltage
Claims
1. A primary transformer that receives the primary AC voltage from the primary circuit, The system includes a secondary transformer that outputs a secondary AC voltage lower than the primary AC voltage to the secondary circuit, The primary transformer comprises a primary winding to which the primary AC voltage is input, a primary secondary winding to which power is transmitted from the primary winding, and a primary core. The secondary transformer comprises a secondary primary winding that forms a closed circuit together with the primary secondary winding, a secondary secondary winding that receives power from the secondary primary winding and outputs the secondary AC voltage, and a secondary core. The primary core has the primary secondary winding wound around its outer circumference, and the primary primary winding wound around the outer circumference of the primary secondary winding. The secondary core has the secondary primary winding wound around its outer circumference, and the secondary secondary winding wound around the outer circumference of the secondary primary winding. The closed circuit has a capacitor connected in series with the primary-side secondary winding and the secondary-side primary winding. A power conversion device characterized in that the primary circuit and the closed circuit are connected to ground potential.
2. The power conversion device according to claim 1, characterized in that the midpoint of the primary-side secondary winding is connected to the ground potential.