Power conversion device

Abstract

To enable the reduction of common-mode noise.SOLUTION: A power conversion device includes a first converter and a second converter, which are bridge-type DC-DC converters. The first converter includes a first switching circuit and a first transformer. The second converter includes a second switching circuit and a second transformer. The first converter and the second converter are connected in parallel or in series. The first transformer and the second transformer are configured as an integrated transformer coupled with a single core, and the polarity of the first transformer is opposite to the polarity of the second transformer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power conversion device. [Background technology]

[0002] Power conversion devices are required to have various characteristics such as high efficiency, small size, low heat generation, and low noise.Patent Document 1 discloses a resonant DC-DC converter comprising: a switch circuit comprising a plurality of switching elements; a first resonant circuit comprising a series circuit of a first reactor, a second reactor, and a resonant capacitor; a second resonant circuit comprising the first reactor, the resonant capacitor, and a rectifying and smoothing circuit; the switch circuit is connected to a primary winding of a transformer; the first resonant circuit and the second resonant circuit are connected to a secondary winding of the transformer; an input first DC voltage is converted to AC by the switch circuit; and the voltage generated in the secondary winding of the transformer is rectified and smoothed to output a second DC voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-006847 Summary of the Invention [Problem to be solved by the invention]

[0004] The invention described in Patent Document 1 leaves room for further consideration regarding noise reduction. [Means for solving the problem]

[0005] A power conversion device according to a first aspect of the present invention is a power conversion device including a first converter and a second converter, each of which is a bridge-type DC-DC converter, wherein the first converter includes a first switching circuit and a first transformer, and the second converter includes a second switching circuit and a second transformer, the first converter and the second converter are connected in parallel or in series, the first transformer and the second transformer are configured as an integrated transformer coupled by a single core, and the polarity of the first transformer and the polarity of the second transformer are opposite to each other. [Effects of the Invention]

[0006] According to the present invention, common mode noise can be reduced. [Brief explanation of the drawings]

[0007] [Figure 1] Power conversion device circuit diagram [Figure 2] A diagram showing the time series changes in voltage and current in the first and second converters [Figure 3] Diagram showing the first example of an integrated transformer [Figure 4] Diagram showing a second example of an integrated transformer DETAILED DESCRIPTION OF THE INVENTION

[0008] -First embodiment- A first embodiment of a power conversion device will be described below with reference to FIGS.

[0009] FIG. 1 is a circuit diagram of a power conversion device 1. The power conversion device 1 is an integrated transformer type DC / DC converter consisting of two systems, a first converter 10 and a second converter 20, and is surrounded by a case 4. The power conversion device 1 converts power between a high-voltage battery VH on the left side of the figure and a low-voltage battery VL on the right side of the figure. The first converter 10 includes a primary-side first circuit 11 which is a primary-side DC / AC converter, a first transformer 13 which magnetically couples the primary side and secondary side, and a secondary-side first converter 12 which is a secondary-side AC / DC converter. The second converter 20 includes a primary-side second circuit 21 which is a primary-side DC / AC converter, a second transformer 23 which magnetically couples the primary side and secondary side, and a secondary-side second converter 22 which is a secondary-side AC / DC converter.

[0010] The primary-side first circuit 11 and the primary-side second circuit 21 are configured with a half-bridge circuit or a full-bridge circuit using semiconductor switches. The secondary-side first converter 12 and the secondary-side second converter 22 are configured with a half-bridge circuit or a full-bridge circuit using semiconductor switches, or a half-wave rectifier circuit or a full-wave rectifier circuit using diodes. The primary-side first circuit 11 shown in FIG. 1 is a full-bridge circuit including semiconductor switches 15 to 18. The primary-side second circuit 21 shown in FIG. 1 is a full-bridge circuit including semiconductor switches 25 to 28.

[0011] The first transformer 13 of the first converter 10 and the second transformer 23 of the second converter 20 are combined by a single core to form an integrated transformer 3 for compactness. The polarities of the transformers of the first and second systems are opposite to each other. This will be described in more detail later.

[0012] In the first converter 10, the intermediate voltage of the left leg circuit consisting of semiconductor switches 15 and 16 is called the 1A intermediate voltage V1A, and the intermediate voltage of the right leg circuit consisting of semiconductor switches 17 and 18 is called the 1B intermediate voltage V1B. In the second converter 20, the intermediate voltage of the left leg circuit consisting of semiconductor switches 25 and 26 is called the 2A intermediate voltage V2A, and the intermediate voltage of the right leg circuit consisting of semiconductor switches 27 and 28 is called the 2B intermediate voltage V2B.

[0013] The leakage currents in the first converter 10 are called the 1A leakage current iLeak1A and the 1B leakage current iLeak1B. The 1A leakage current iLeak1A is the current flowing through the parasitic capacitance existing between the 1A intermediate voltage V1A and Case 4. The 1B leakage current iLeak1B is the current flowing through the parasitic capacitance existing between the 1B intermediate voltage V1B and Case 4. The leakage currents in the second converter 20 are called the 2A leakage current iLeak2A and the 2B leakage current iLeak2B. The 2A leakage current iLeak2A is the current flowing through the parasitic capacitance existing between the 2A intermediate voltage V2A and Case 4. The 2B leakage current iLeak2B is the current flowing through the parasitic capacitance existing between the 2B intermediate voltage V2B and Case 4. The current flowing through the first transformer 13 is called the first transformer current i1L, and the current flowing through the second transformer 23 is called the second transformer current i2L.

[0014] All of the semiconductor switches in the primary-side first circuit 11 and the primary-side second circuit 21 operate in the same cycle T, and some of the semiconductor switches operate in conjunction with each other. Specifically, semiconductor switch 15, semiconductor switch 16, semiconductor switch 25, and semiconductor switch 26 operate at the same timing, and semiconductor switch 17, semiconductor switch 18, semiconductor switch 27, and semiconductor switch 28 operate at another timing. This will be explained in detail below.

[0015] The semiconductor switches 15 and 26 are referred to as a first group, the semiconductor switches 16 and 25 as a second group, the semiconductor switches 17 and 28 as a third group, and the semiconductor switches 18 and 27 as a fourth group.

[0016] The first and second groups operate at times t1 and t1+T / 2xN (N is an integer). The first group switches from ON to OFF at time t1, and the second group switches from OFF to ON at time t1. The first group switches from OFF to ON half a cycle after time t1, that is, at time t1+T / 2, and the second group switches from ON to OFF at time t1+T / 2.

[0017] The third and fourth groups operate at times t2 and t1+T / 2xN (N is an integer). The third group switches from ON to OFF at time t2, and the fourth group switches from OFF to ON at time t2. The third group switches from OFF to ON half a cycle after time t2, that is, at time t2+T / 2, and the fourth group switches from ON to OFF at time t2+T / 2.

[0018] The names of the terminals on the primary side of the integrated transformer 3 are listed at the bottom of FIG. 1. In each of the first transformer 13 and the second transformer 23, the end of the coil on the positive side of the Y axis is called the first terminal, and the end on the negative side of the Y axis is called the second terminal. A first-A intermediate voltage V1A between semiconductor switch 15 and semiconductor switch 16 is applied to the first transformer first terminal 13P1. A first-B intermediate voltage V1B between semiconductor switch 17 and semiconductor switch 18 is applied to the first transformer second terminal 13P2. A second-A intermediate voltage V2A between semiconductor switch 25 and semiconductor switch 26 is applied to the second transformer first terminal 23P1. A second-B intermediate voltage V2B between semiconductor switch 27 and semiconductor switch 28 is applied to the second transformer second terminal 23P2.

[0019] 2 is a diagram showing time-series changes in voltage and current in the first converter 10 and the second converter 20. However, FIG. 2 shows an example of a phase shift system in which a phase difference θ is provided in the ON / OFF operation of the left leg and the right leg. The left leg is made up of semiconductor switches 15 and 16, and semiconductor switches 25 and 26. The right leg is made up of semiconductor switches 17 and 18, and semiconductor switches 27 and 28.

[0020] For example, in the first converter 10, when the semiconductor switch 15 switches from OFF to ON and the semiconductor switch 16 switches from ON to OFF, the 1A intermediate voltage V1A changes from 0 V to VH. After that, when the phase difference θ has elapsed, when the semiconductor switch 17 switches from ON to OFF and the semiconductor switch 18 switches from OFF to ON, the 1B intermediate voltage V1B changes from VH to 0 V.

[0021] Just to be sure, the reverse change is described as follows: When semiconductor switch 15 switches from ON to OFF and semiconductor switch 16 switches from OFF to ON, the 1A intermediate voltage V1A changes from VH to 0 V. After that, when the phase difference θ has elapsed, when semiconductor switch 17 switches from OFF to ON and semiconductor switch 18 switches from ON to OFF, the 1B intermediate voltage V1B changes from 0 V to VH.

[0022] At each switching timing, a first A leakage current iLeak1A=C*dv / dt flows through the parasitic capacitance C present between the first A intermediate voltage V1A and the first B intermediate voltage V1B and the case due to the potential fluctuations described above. This leakage current flows to the outside through case 4 and becomes common-mode noise. The above description concerns the first converter 10, but the same applies to the second converter 20.

[0023] In this embodiment, the phase difference between the first and second systems is set to 180 degrees. In this case, the 1A intermediate voltage V1A and the 2A intermediate voltage V2A have voltage waveforms of opposite polarity. Similarly, the 1B intermediate voltage V1B and the 2B intermediate voltage V2B also have voltage waveforms of opposite polarity. Therefore, at time t1, the 1A leakage current iLeak1A due to potential fluctuations in the 1A intermediate voltage V1A and the 2A leakage current iLeak2A due to potential fluctuations in the 2A intermediate voltage V2A cancel each other out, thereby reducing common-mode noise. Furthermore, at time t2, the 1B leakage current iLeak1B due to potential fluctuations in the 1B intermediate voltage V1B and the 2B leakage current iLeak2B due to potential fluctuations in the 2B intermediate voltage V2B cancel each other out, thereby reducing common-mode noise.

[0024] However, if the primary-side first circuit 11 and the primary-side second circuit 21 are switched complementarily without any special ingenuity, the first converter 10's transformer applied voltage (1A intermediate voltage V1A-1B intermediate voltage V1B) and the second converter 20's transformer applied voltage (2A intermediate voltage V2A-2B intermediate voltage V2B) will have opposite polarities, and the first transformer current i1L and the second transformer current i2L will also have opposite polarities. In this case, the magnetic flux generated in the integrating transformer 3 cancels out, preventing the integrating transformer 3 from functioning properly. Therefore, in this embodiment, the polarities of the first transformer 13 and the second transformer 23 in the integrating transformer 3 are opposite to each other, thereby aligning the magnetic flux generated in the integrating transformer 3.

[0025] FIG. 3 is a diagram showing a first example of an integrated transformer 3. The X, Y, and Z axes shown in FIG. 3 are depicted for convenience of explanation. In the integrated transformer 3, a coil is wound around an iron core 3C extending in the Y-axis direction. Here, when moving from the negative side to the positive side of the Y-axis, the coil is wound clockwise around the iron core 3C, which is referred to as "forward winding," and the coil is wound counterclockwise around the iron core 3C, which is referred to as "reverse winding." The first transformer 13 is reverse wound, and the second transformer 23 is forward wound.

[0026] The current flow in the integrated transformer 3 shown in Figure 3 will be described with reference to the time chart shown in Figure 2. At time t1, the first transformer current i1L is negative and the second transformer current i2L is positive. Therefore, the first transformer current i1L flows in the opposite direction to the arrow marked with symbol i1L in Figure 3, generating a magnetic flux pointing toward the negative Y-axis. The second transformer current i2L flows in the direction of the arrow marked with symbol i2L in Figure 3, generating a magnetic flux pointing toward the negative Y-axis, similar to the first transformer 13.

[0027] FIG. 4 is a diagram showing a second example of the integrated transformer 3. The differences between FIG. 4 and FIG. 3 will be mainly described. The winding direction of the first transformer 13 in FIG. 4 is reverse winding, as in FIG. 3. The winding direction of the second transformer 23 in FIG. 4 is reverse winding, unlike FIG. 3. That is, the winding directions of the first transformer 13 and the second transformer 23 are the same in FIG. 4. The connections of each terminal of the first transformer 13 in FIG. 4 are the same as in FIG. 3, while the connections of each terminal of the second transformer 23 in FIG. 4 are opposite to those in FIG. 3. That is, in FIG. 4, the secondB intermediate voltage V2B between the semiconductor switch 27 and the semiconductor switch 28 is applied to the second transformer first terminal 23P1. The secondA intermediate voltage V2A between the semiconductor switch 25 and the semiconductor switch 26 is applied to the second transformer second terminal 23P2.

[0028] The current flow in the integrated transformer 3 shown in Figure 4 will be explained with reference to the timing chart shown in Figure 2. The first transformer 13 has the same winding direction and connection to the primary-side first circuit 11 as in Figure 3, so the current flow in the first transformer 13 is the same as in Figure 3. The second transformer 23 has the opposite winding direction and connection to the primary-side second circuit 21 to those in Figure 3. Therefore, the current flow in the second transformer 23 is the opposite of that in Figure 3.

[0029] According to the first embodiment described above, the following advantageous effects can be obtained. (1) The power conversion device 1 includes a first converter 10 and a second converter 20, which are bridge-type DC-DC converters. The first converter 10 includes a primary-side first circuit 11 and a first transformer 13. The second converter 20 includes a primary-side second circuit 21 and a second transformer 23. The first converter 10 and the second converter 20 are connected in parallel. The first transformer 13 and the second transformer 23 are combined into an integrated transformer 3 using a single core. The polarity of the first transformer 13 and the polarity of the second transformer 23 are opposite to each other. This allows common-mode noise to cancel each other out, thereby reducing the common-mode noise. For example, in the example shown in FIG. 2, the 1A leakage current iLeak1A and the 2A leakage current iLeak2A cancel each other out at time t1, and the 1B leakage current iLeak1B and the 2B leakage current iLeak2B cancel each other out at time t2.

[0030] (2) As shown in Fig. 3, the winding direction of the first converter 10 is opposite to that of the second converter 20. Therefore, by making the winding directions different, the polarities of the first transformer 13 and the second transformer 23 can be reversed.

[0031] (3) As shown in Fig. 4, the winding direction of the first transformer 13 relative to the integrated transformer 3 and the winding direction of the second transformer 23 relative to the single core are the same, and the connection of the primary-side first circuit 11 to both ends of the first transformer 13 and the connection of the primary-side second circuit 21 to both ends of the second transformer 23 are reversed. Therefore, even if the winding directions of the first transformer 13 and the second transformer 23 are the same, the polarities of the first transformer 13 and the second transformer 23 can be reversed by changing the connections between the transformers and the switching circuits.

[0032] (4) The primary-side first circuit 11, which is a switching circuit of the first converter 10, and the primary-side second circuit 21, which is a switching circuit of the second converter 20, perform complementary switching so that the on and off polarities are opposite to each other.

[0033] (Variation 1) In the above-described embodiment, the first converter 10 and the second converter 20 are connected in parallel, but the first converter 10 and the second converter 20 may be connected in series.

[0034] The above-described embodiments and modifications may be combined with each other. Although various embodiments and modifications have been described above, the present invention is not limited to these. Other embodiments conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention. [Explanation of symbols]

[0035] 1: Power conversion device 3: Integrated transformer 10: First converter 11: Primary side 1st circuit 12: Secondary side first converter 13: First transformer 20: Second converter 23: Second transformer i1L: 1st transformer current i2L: Second transformer current iLeak1A: 1A leakage current iLeak1B: 1B leakage current iLeak2A: 2nd A leakage current iLeak2B: 2nd B leakage current

Claims

1. A power conversion device including a first converter and a second converter, each of which is a bridge-type DC-DC converter, the first converter includes a first switching circuit and a first transformer; the second converter includes a second switching circuit and a second transformer; the first converter and the second converter are connected in parallel or in series; the first transformer and the second transformer are configured as an integrated transformer coupled by a single core, A power conversion device, wherein the polarity of the first transformer and the polarity of the second transformer are opposite to each other.

2. The power conversion device according to claim 1, A power conversion device, wherein the winding direction of the first converter and the winding direction of the second converter are opposite to each other.

3. The power conversion device according to claim 1, a winding direction of the first transformer around the single core and a winding direction of the second transformer around the single core are the same direction, A power conversion device, wherein the connection of the first switching circuit to both ends of the first transformer and the connection of the second switching circuit to both ends of the second transformer are reversed.

4. The power conversion device according to any one of claims 1 to 3, a power conversion device, wherein the switching circuit of the first converter and the switching circuit of the second converter perform switching in a complementary manner such that on and off polarities are opposite to each other;

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