Power converter
The power conversion device addresses high heat flux and temperature fluctuations by integrating boiling cooling and capillary-driven circulation, enhancing semiconductor module lifespan and reducing energy consumption.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- KK TOSHIBA
- Filing Date
- 2024-10-25
- Publication Date
- 2026-05-13
AI Technical Summary
Existing power conversion devices face challenges in managing high heat flux and temperature fluctuations due to load changes, leading to reduced semiconductor element lifespan and increased pump power requirements, particularly in systems with miniaturized and weight-reduced designs.
A power conversion device utilizing a boiling cooling system combined with capillary-driven circulation, featuring a heat transfer block, porous body, and steam discharge sections to manage heat flux and temperature fluctuations, reducing the need for pumps and optimizing fluid flow.
The system effectively manages high heat flux and temperature fluctuations, extending semiconductor module lifespan and reducing energy consumption by leveraging capillary forces for efficient fluid circulation and heat dissipation.
Smart Images
Figure 2026077065000001_ABST
Abstract
Description
Technical Field
[0001] Embodiments of the present invention relate to a power conversion device.
Background Art
[0002] Techniques using a power conversion device for railway vehicles and the like are known. Such a power conversion device applies a circulation water cooling system, which is a circulation method, to the cooling method of a system including a semiconductor module.
[0003] The circulation water cooling system of this power conversion device has, for example, a circulation water cooling system including a heat receiving part, a heat exchange part, a reservoir tank, and a pump. The heat receiving part has a heat sink block on which a semiconductor module is mounted and cooled. The pump supplies internal fluid from the reservoir tank to the heat receiving part and the heat exchange part, and returns it from the heat exchange part to the reservoir tank.
[0004] Such a circulation water cooling system can maintain stable cooling performance because it circulates the working refrigerant with a constant flow rate. Although the generated loss is reduced by the evolution of the semiconductor device performance in the future, there is a concern about the influence on the life of the semiconductor chip due to the increase in the heat density caused by miniaturization and weight reduction.
[0005] Generally, among power electronics devices, in applications where the load fluctuation is large, if the flow rate is circulated constantly, the semiconductor element may be over-cooled, and the temperature change of the semiconductor element may increase. This will lead to promoting the deterioration of the element life.
[0006] In addition, with the increase in the capacity of future devices, the number of semiconductor elements in parallel is expected to increase in the circulation water cooling system, and the temperature fluctuation with respect to the load fluctuation of the power conversion device system will increase. Also, the circulation water cooling system is required to have a high heat flux. However, in order to increase the heat flux of the circulation water cooling system, it is necessary to increase the flow rate, and an increase in the pump power due to the pressure loss becomes an issue.
[0007] On the other hand, as a cooling system that can handle high heat flux, a boiling cooling method that utilizes the latent heat of vaporization due to the phase change of the working refrigerant is also known. However, while boiling cooling systems can be expected to suppress temperature fluctuations in response to load fluctuations, their ability to respond quickly to steep loads (stability) is a challenge. In particular, it is difficult to increase capacity by configuring multiple modules in parallel. [Prior art documents] [Patent Documents]
[0008] [Patent Document 1] Japanese Patent Publication No. 2024-036827 [Overview of the Initiative] [Problems that the invention aims to solve]
[0009] The problem that this invention aims to solve is to provide a power conversion device that has a cooling system that uses boiling cooling and circulation assistance in combination, and that can reduce the pump power of the cooling system and reduce costs by using the action of capillaries in a porous body as the driving source. [Means for solving the problem]
[0010] The power conversion device of the embodiment comprises a heat receiving section having a heat transfer block to which a semiconductor module is attached, a porous body joined to the heat transfer block, and a liquid channel through which a working fluid flows, a heat exchange section for dissipating heat from the transported working fluid, a reservoir tank provided above the heat receiving section for storing the working fluid, a steam flow pipe connecting the heat receiving section and the heat exchanger, a liquid return pipe connecting the heat exchange section and the reservoir tank, and a steam discharge section formed in the porous body so as to be in contact with the heat transfer block. [Brief explanation of the drawing]
[0011] [Figure 1] Figure 1 is a schematic diagram illustrating the configuration of a power conversion device according to an embodiment. [Figure 2]Figure 2 is a cross-sectional view showing the cross-sectional structure around the porous body of the heat receiving section. [Figure 3] Figure 3 is a schematic diagram showing an enlarged cross-section of the porous material around the heat receiving section. [Figure 4] Figure 4 shows the internal cross-sectional structure of the lower part of the heat receiving section. [Figure 5] Figure 5 shows the internal cross-sectional structure of the upper part of the heat receiving section. [Figure 6] Figure 6 is a cross-sectional view showing the cross-sectional structure around the porous body of the heat receiving section in the first modified example. [Figure 7] Figure 7 is an enlarged schematic diagram of the cross-section around the porous body of the heat receiving section in the first modified example. [Figure 8] Figure 8 is a cross-sectional view showing the cross-sectional structure around the porous body of the heat receiving section in the second modified example. [Figure 9] Figure 9 is an enlarged schematic diagram of the cross-section around the porous body of the heat receiving section in the second modified example. [Modes for carrying out the invention]
[0012] The power conversion device according to the embodiment will be described below with reference to Figures 1 to 5. For the sake of clarity, the scale of each component in each figure has been appropriately changed, and some parts have been omitted or simplified.
[0013] Figure 1 is a schematic diagram illustrating the configuration of a power conversion device according to an embodiment. Figures 2 and 3 schematically show the configuration of the heat receiving section of the power converter. Figure 2 is a cross-sectional view showing the cross-sectional structure around the porous body of the heat receiving section, and Figure 3 is an enlarged schematic view of the cross-section around the porous body of the heat receiving section. Figure 4 shows the internal cross-sectional structure of the lower part of the heat receiving section, and Figure 5 shows the internal cross-sectional structure of the upper part of the heat receiving section.
[0014] As shown in Figure 1, the power conversion device comprises a heat receiving unit 1, a semiconductor module 2, a heat exchange unit 3, a reservoir tank 4, a pump 5, a blower 6, a liquid return pipe 30, a liquid single-phase inlet pipe 31, a steam flow pipe 40, and a steam outlet pipe 41a.
[0015] The heating section 1 allows the working fluid in the liquid phase to pass through. The heating section 1 separates the working fluid in the liquid phase from the working fluid in the gas phase, where a part of the working fluid in the liquid phase has undergone a phase change to become the gas phase due to the heat of the attached semiconductor module 2. The heating section 12 sends the working fluid in the liquid phase to the reservoir tank 4 and sends the working fluid in the gas phase to the heat exchange section 3. For example, as shown in FIG. 1, a plurality of heating sections 1 are provided.
[0016] The semiconductor module 2 is, for example, attached singly or plurally to one heating section 1. The semiconductor module 2 may be, for example, a module in which a plurality of semiconductor elements are housed in one package, or a module including a control circuit, a drive circuit, a protection circuit, etc. in addition to the semiconductor elements.
[0017] Also, the semiconductor module 2 may be configured such that the semiconductor element is directly attached to the heating section 1, or may be configured such that the semiconductor element is attached to the heating section 1 via another member. That is, as long as the semiconductor module 2 can be cooled by the heating section 1 when it generates heat by being attached to the heating section 1, the arrangement and attachment method of the components can be set as appropriate.
[0018] The heat exchange section 3 allows the working fluid in the gas phase to pass through the inside, and condenses the working fluid in the gas phase by heat-exchanging the working fluid in the gas phase, causing a phase change to the working fluid in the liquid phase.
[0019] The reservoir tank 4 stores the working fluid in the liquid phase. The reservoir tank 4 sends the working fluid in the liquid phase to the heating section 1 and recovers the working fluid in the liquid phase that has passed through the heating section 1 and the working fluid in the liquid phase that has condensed in the heat exchange section 3.
[0020] The pump 5 sends the working fluid in the liquid phase that has condensed in the heat exchange section 3 to the reservoir tank 4. The pump 5 can adjust the flow rate (pressure) of the working fluid to be discharged. Also, the pump 5 assists in sending the working fluid in the reservoir tank 4 to the heating section 1.
[0021] The blower 6 blows outside air from the power converter to the heat exchange section 1. For example, the blower 6 takes in outside air from the wind tunnel duct 50. By blowing air to the heat exchange section 1, the blower 6 performs heat exchange between the outside air and the gaseous working fluid flowing through the heat exchange section 1.
[0022] The liquid reflux pipe 30 connects the heat exchange section 3 and the pump 5. The liquid single-phase inlet pipe 31 connects to the pump 5 and the reservoir tank 5. The liquid single-phase inlet pipe 31 also has liquid single-phase inlet pipes 31a that branch off to reservoir tanks provided for each heat receiving section.
[0023] The steam flow pipe 40 connects the heat receiving section 1 and the heat exchange section 3. The steam flow pipe 40 has steam outlet pipes 40a connected to the outlets of each heat receiving section, and connects to the heat exchange section 3 by converging the inlets of multiple heat receiving sections.
[0024] Next, the configuration of the heat receiving section will be explained using Figures 2 and 3. As shown in Figure 2, the heat receiving section 1 includes a heat transfer block 22 and a porous body 25.
[0025] The heat transfer block 22 has a semiconductor module 2 attached to one side and a porous body 25 bonded to the other side. The heat transfer block 22 is made of a material with high thermal conductivity, such as aluminum. A pair of heat transfer blocks 22 are arranged with the sides to which the porous body 25 is bonded facing each other, and a liquid channel 400 through which a liquid-phase working fluid 500 flows is formed between the porous bodies 25.
[0026] The porous body 25 has circular grooves 300 arranged at predetermined equal intervals so as to be in contact with the heat transfer block 22. The circular grooves 300 function as steam discharge sections, which will be described later. Note that the circular grooves 300 only need to function as steam discharge sections, and may be elliptical in shape, for example.
[0027] Furthermore, the porous body 25 allows a portion of the working fluid 500 in the liquid phase flowing through the liquid channel 400 to pass through, and multiple pores are formed on either side of the porous body 25 such that the differential pressure level between the liquid phase of the liquid channel 400 and the gas phase of the circular groove 300, which is the vapor discharge section, is below the maximum capillary force inside the porous body 25. The porous body 25 is, for example, a sintered body, foam body, or lotus-shaped body made of resin or metal fibers / particles, and has appropriate thermal conductivity and appropriate porosity.
[0028] As a result, the porous body 25 allows the liquid-phase working fluid 500 to pass through the liquid channel 400, and through multiple holes formed inside, allows some of the liquid-phase working fluid 500 to pass from the liquid channel 400 through its interior to the heat transfer block 22. Then, at the interface of the end of the porous body 25 that is in contact with the heat transfer block 22, the working fluid 500 evaporates (phase changes) as it exchanges heat with the heat transfer block 22 to which the semiconductor module 2 is attached, and the gaseous working refrigerant 101 passes through the circular hole groove 300, which is the vapor discharge section.
[0029] Here, we will explain the fabrication process for the heat receiving section, particularly the process of forming the steam outlet section in the porous body 25. When forming the circular groove 300 that will serve as the steam outlet section in the porous body 25, one method is to fabricate the steam groove shape in the porous body 25 and then join the heat transfer block 22 to it. Another method is to first join the porous body 25 and the heat transfer block 22 together, and then form the steam groove into a circular hole shape using water jet processing. In this case, the fabrication process can be reduced compared to the former method, thus reducing the fabrication cost.
[0030] Figure 4 shows the internal cross-sectional structure of the lower part of the heat receiving section. The internal structure of the lower part of the heat receiving section 1 is configured such that steam, which has undergone a gas-liquid phase change at the contact interface between the porous body 25 and the heat transfer block, flows through it.
[0031] The structure consists of a steam outlet 320a for each circular hole groove 300 that serves as a steam discharge section where the semiconductor module 2 is mounted, and a steam outlet flow path 360 where they converge. The porous body 25 is configured to cover the internal liquid flow path 400. The diameter of the steam outlet 320a here may be adjusted as appropriate according to the amount of heat removed by the semiconductor module in question.
[0032] Figure 5 shows the internal cross-sectional structure of the upper part of the heat receiving section 1. The upper structure of the heat receiving section 1 is configured such that a reservoir 4 for gas-liquid adjustment is connected via a connecting block 80, and the working fluid 500 can be stored inside.
[0033] Here, we will explain the processes necessary for the cooling system to function properly. As shown in Figures 2 and 3, the semiconductor module 2 mounted on the heat receiving section 1 generates heat due to the operation of the power converter. The working fluid 500 flows through the liquid channel 400 inside the heat receiving section 1. At this time, the working fluid 500 passes through the porous body 25 by capillary force and penetrates to the end that comes into contact with the heat transfer block 22.
[0034] The porous body 25, which is joined to the heat transfer block 22, exchanges heat with the heat transfer block 22, and the working fluid 500 preferentially evaporates (phase changes) at the three-phase contact interface 310a, and the generated steam is induced to the circular hole groove 300, which is the steam discharge section. In this case, the total pressure loss on the loop system is configured to be below the maximum capillary head inside the porous body 25, based on the following equation 1.
[0035] PCAP_lim ≧ ΔPpor+ΔPgr+ΔPv+ΔPL+ΔPcon±Phead...Equation 1 Here, Pcap_lim is the maximum capillary force (Pa), ΔPpor is the pressure loss in the porous body 25 (Pa), ΔPgr is the pressure loss in the steam discharge section (Pa), ΔPv is the pressure loss in the steam flow pipe 40 (Pa), ΔPL is the pressure loss in the liquid single-phase section of the liquid reflux pipe 30 and the liquid single-phase inlet pipe 31 (Pa), ΔPcon is the pressure loss in the heat exchange section 3 (Pa), and Phead is the system head (Pa).
[0036] By satisfying this formula, a balance is maintained between the steam generated from the three-phase contact interface 310a between the heat transfer block 22 and the porous body 25 and the supply of the working fluid 500 from within the porous body 25, thereby ensuring proper separation of gas and liquid across the porous body 25.
[0037] The generated steam is sent from the circular hole groove 300, which is the steam discharge section, through the steam outlet 320a and steam outlet flow path 360 shown in Figure 4 to the steam outlet pipe 40a. At the same time, the same action occurs in the heat receiving section 1 which is arranged in parallel, and the steam is sent to the heat exchange section 3 by joining the steam flow pipe 40. In the heat exchange section 3, outside air is blown in by a blower 6 installed nearby, and heat exchange is performed, causing the steam flowing inside the heat exchange section 3 to condense and release heat.
[0038] The condensed vapor liquefies and is sent to the reservoir tank 4 via the liquid reflux pipe 30 and pump 5, where it is returned again as the working fluid 500 to the liquid flow path 400 inside the heat receiving section 1. Within the limits of satisfying the aforementioned equation 1, the pump 5, which plays a role in assisting the heat receiving section with the working fluid, may be omitted.
[0039] As described above, by efficiently supplying the working fluid within the system to the porous body of the heat receiving section in accordance with the thermal load of the semiconductor module, separating it into a gas phase at the three-phase contact interface between the porous body and the heat transfer block, dissipating the generated steam in the heat exchange section, and then returning it to the heat receiving section for circulation, it becomes possible to operate the cooling system normally.
[0040] Furthermore, because the system utilizes the action of capillaries within the porous body as the driving force, it eliminates the need to transport heat to the heat exchange section via a pump, as is required in circulating water cooling systems. This reduces pump power, contributing to smaller and more energy-efficient pumps. Moreover, if pressure loss can be reduced and the desired capillary force can be secured, a configuration without pump drive becomes possible, resulting in a significant reduction in energy consumption.
[0041] Furthermore, since this cooling system utilizes latent heat rather than sensible heat transport like a circulating water cooling system, it can be constructed with the minimum necessary working fluid, thus reducing the weight by the amount of working fluid. Because liquefaction from a gaseous state reduces the temperature difference compared to heat dissipation in a single-phase liquid flow, the volume of the heat exchange section can be reduced when comparing under the same heat dissipation conditions, thus increasing installation flexibility and weight reduction.
[0042] Furthermore, under normal operation, the latent heat of vaporization due to boiling cooling is utilized, which allows for high heat flux. Even when boiling does not occur at low flow rates, heat transport and heat dissipation are possible with low pump power. This suppresses and equalizes temperature fluctuations in response to changes in thermal load, ultimately extending the lifespan of semiconductor modules.
[0043] Next, a first modified example of this embodiment will be described. Figure 6 is a cross-sectional view showing the cross-sectional structure around the porous body 25 of the heat receiving section 12 in the first modified example, and Figure 7 is an enlarged schematic diagram of the cross-section around the porous body 25 of the heat receiving section 12 in the first modified example. The same reference numerals are used for parts that are the same as those in the embodiments shown in Figures 2 and 3, and their detailed descriptions are omitted.
[0044] In Figures 6 and 7, the difference from the embodiment is that the elliptical groove 350, which serves as the steam discharge section, is formed as a groove portion in accordance with the elliptical shape not only in the porous body 25 but also in the heat transfer block 22 which is joined to the porous body 25.
[0045] As a result, the contact area between the porous body 25 and the heat transfer block 22 is reduced, which reduces pressure loss in that area and promotes steam discharge.
[0046] Next, a second modified example of this embodiment will be described. Figure 8 is a cross-sectional view showing the cross-sectional structure around the porous body 25 of the heat receiving section 12 in the second modified example, and Figure 9 is an enlarged schematic diagram of the cross-section around the porous body 25 of the heat receiving section 12 in the second modified example. The same reference numerals are used for parts that are the same as those in the first modified example shown in Figures 6 and 7, and their detailed explanations are omitted.
[0047] In Figures 8 and 9, the difference from the first modified example is that the porous body 25 consists of a first porous layer 25a and a second porous layer 25b. The first porous layer 25a is provided on the liquid channel 400 side, and the second porous layer 25b is provided on the heat transfer block 22 side.
[0048] Furthermore, the first porous layer 25a and the second porous layer 25b have different porosities, and it is preferable that the porosity of the second porous layer 25b is configured to be relatively harder. The thickness and porosity of the second porous layer 25b may be appropriately adjusted according to the heat load from the power semiconductor module 2 to be heat removed.
[0049] In this way, by creating a gradient of different porosities between the first porous layer 25a and the second porous layer 25b, and making the porosity of the second porous layer 25b relatively higher, the steam discharge can be made more efficient by maximizing capillary force and minimizing pressure loss. This suppresses the rapid deterioration of heat transfer due to dry-out near the three-phase contact interface and contributes to improving the critical heat flux.
[0050] Although embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]
[0051] 1...Heat receiving part 2. Semiconductor Modules 3...Heat exchange section 4. Reservoir Tank 5. Pump 6. Blower 25. Porous material 25a...First porous layer 25b...Second porous layer 300...Circular hole groove 350... Elliptical groove 400...liquid flow path
Claims
1. A heat receiving section having a heat transfer block to which a semiconductor module is attached, a porous body joined to the heat transfer block, and a liquid channel through which a working fluid flows, A heat exchange section that dissipates heat from the transported working fluid, A reservoir tank for storing working fluid is provided above the heat receiving section, A steam flow pipe connecting the heat receiving section and the heat exchanger, A liquid return pipe connecting the heat exchange section and the reservoir tank, A power conversion device comprising: a steam discharge section formed in the porous body so as to be in contact with the heat transfer block.
2. The power conversion device according to claim 1, wherein the steam discharge section is a circular hole groove provided in the porous body.
3. The power conversion device according to claim 1, wherein the steam discharge section is an elliptical groove provided across the porous body and the heat transfer block.
4. The power conversion device according to claim 1, wherein the porous body comprises a first porous layer in contact with the liquid channel and a second porous layer in contact with the heat transfer block, and the porosity of the second porous layer is relatively high.
5. The power conversion device according to claim 1, wherein a pump for supplying working fluid to the reservoir tank is provided between the heat exchange unit and the reservoir tank.
6. The power conversion device according to claim 1, wherein the heat receiving section is provided by having a plurality of semiconductor modules attached to both sides of the heat transfer block.
7. The power conversion device according to claim 1, wherein a plurality of the heat receiving units and the reservoir tanks are arranged in parallel.