1. Introduction
In recent years, due to the increasing requirements for miniaturization and lightweight industrial products, power arrays are developing in the high-density, high-power, and intelligent directions [
1]. Temperature rise is a critical factor affecting the reliability of power modules. With an increase in temperature, the failure efficiency of electronic components shows an exponential growth trend, which seriously affects the regular operation of supply load [
2]. With the increase in working hours, some cooling measures must be taken to limit the temperature rise in clustered power modules.
Frequently used thermal design methods include physical structure heat dissipation and modeling optimization heat dissipation. Physical structure heat dissipation can be divided into natural air cooling, conduction cooling, forced air cooling, circulating water cooling, and so on. Natural air cooling mainly transfers heat from the power module shell to the air through natural convection or conducts it to the PCB through pins. The conductive heat dissipation includes a layer of heat-conducting silicone sheet and resin between the shell and the module, so that the body and the module are closely combined. Forced air cooling provides for the use of fans to increase airflow to remove accumulated heat. Circulating water cooling involves placing water-filled conduits on top of the heat module to dissipate heat through flow liquor. Software modeling mainly uses computers to conduct thermal simulation calculations with environmental parameters, including structural heat dissipation characteristics and heat source layout. It guides the relevant thermal design after establishing thermal simulation models.
To solve the problem of heat dissipation of power arrays, various researchers adopt single or combined physical methods based on general thermal design measures and use software analysis. They fail to solve the problem of heat dissipation fundamentally, comprehensively, systematically, and entirely and may find new issues or risks when translated. The paper [
3] combines methods (natural air cooling, thermal conduction, forced air cooling) used for heat dissipation. The optimized structure can meet the heat dissipation requirements, but the selected test power supply has low power and still needs to meet the design requirements of high strength and high density. In addition, the numerical simulation method does not consider the influence of materials on conduction heat. The paper [
4] adopts a forced air cooling method and establishes a three-dimensional simulation model. The heat dissipation conditions are improved by optimizing the air intake channel. However, all the simulation data remain in the theoretical calculation stage, and the actual heat dissipation effect needs complete test verification. The paper [
5] designs an air–liquid water-cooling cabinet and optimizes the structural size design. The heat dissipation effect is improved due to the optimization of the structure layout, but the heat exchange improves the power consumption of the whole system. If the cold plate is subjected to severe impact, vibration, and extrusion, it may lead to leakage of coolant, threatening the safety of the whole system. It can be seen that the current thermal design scheme has more or less the following problems. Firstly, only from the perspective of the heat dissipation channel, heat dissipation layout, and software modeling, the heat dissipation environment is optimized to improve the heat dissipation effect, whereas the efficiency of the heat source, the use of conductive materials, and other factors are not considered. Secondly, the effectiveness of thermal design measures can only be verified with high load tests based on miniaturization, high power, and a high-density design. Thirdly, the software modeling environment is ideal, and the simulation parameters are straightforward. A lack of test data results in a specific deviation between the simulation environment and the natural environment with load, which is insufficient to guide the thermal design further. Fourthly, improving the heat dissipation performance results in reliability degradation of the system. Fifthly, the lack of logic for monitoring temperature, current, and voltage-related operation data of heat source devices and the formation of feedback regulation may lead to excessive thermal design. For example, forced air cooling can cause an improvement in static power consumption, resulting in unnecessary operation noise.
In this paper, a highly miniaturized high-power and high-density power array is designed. High-efficiency DC/DC modules are selected as the heating source. Magnesium and aluminum alloys are used as the primary structural materials in heat dissipation, and graphene is the conduction material between the heat source and the cold plate. They can ensure that the power array case has high thermal conductivity while considering high strength, lightweight, and anti-electromagnetic interference characteristics. Natural air cooling and conduction heat dissipation are combined, and forced air cooling is a supplement. In addition, the MCU chip, multi-point temperature, voltage, and current sensors, A/D acquisition chip, relay, and other automation modules can intelligently monitor the temperature rise of each point of the power module and then control the power array and forced air cooling starting time. Finally, the electronic case is placed for testing in a closed thermal environment for dynamic loading. The results show that the heat dissipation system can effectively improve the heat dissipation condition and reduce the working temperature of the whole system without sacrificing the performance and can meet the requirements of fast response and continuous and efficient output power of the power array. The output power of the entire system is not less than 10,000 W, and the lowest packing-level density is not less than 47 W/cm with high reliability, portability, and practicability. It also provides technical and prototype support for the standardized design of similar power arrays.
The paper is structured as follows.
Section 2 presents the thermal design methods of heat dissipation of physical form and heat dissipation optimization by modeling.
Section 3 offers the design of an automatic cooling case based on a high-power power supply array, including conduction cooling design, forced air cooling design, high power density power supply array design, and automatic control module design.
Section 4 analyzes and compares the test results with related performance parameters.
Section 5 discusses the experimental conclusions and future research.
2. Related Works
In recent years, various research teams have proposed solutions to the heat dissipation problem of closed power supply cases (modules) with high power density and small volumes from different perspectives, which can be roughly divided into two categories as in
Table 1: physical structure heat dissipation and modeling optimization heat dissipation.
The heat dissipation of physical structures is usually improved or optimized by combining natural air cooling, conduction cooling, forced air cooling, and circulating water cooling. Li [
3] analyzes the heat dissipation path of a high power density closed power supply and proposes a design method to strengthen heat dissipation by using the shell extension surface structure of a rectangular fin to increase the conduction refrigeration area. Yu [
6] adopts heat pipe cooling technology in cold plates to improve the heat transfer capacity of hard scale. Fu [
7] designs the structure and method of ventilation and heat dissipation of a new energy storage power supply, which realizes uniform heat dissipation inside the energy storage power supply through such structures and processes it through the air inlet and air guide plate at the bottom of the energy storage power supply, switchable cooling mode, and independent air duct outlet. Tan [
4], aiming at the heat dissipation problem of the power cabinet of airborne equipment, adopts the method of forced air cooling to reasonably improve the air intake pipe to reduce the pressure loss in the line and achieve better air cooling heat dissipation effects. Ben [
2] adopts the distributed forced air cooling for heat dissipation of the modular DC power cabinet in the substation, which effectively controls the temperature difference between the power module and the radiator. However, these solutions are based on the physical heat dissipation of the selected power module’s combination power density, which is low, and only use the heat dissipation structure to optimize adjustment. Without using a closed extreme environment for a long time with a load output test, the cooling effect is unknown, so there is no fundamental solution to the problem of heat dissipation. In addition, structural adjustment may bring low reliability of the whole system.
Thermodynamic analysis software is usually used to establish the simulation model of the power supply, which is used to verify the technical requirements and optimize the product structure and selection design to provide practical and rigorous design scheme guidance for the air-cooled or water-cooled cabinets used in the industrial field. Yang [
5] conducts a three-dimensional simulation analysis of the whole machine to understand the local cooling air path design, the gas–liquid heat exchange device, and the corresponding cold plate for the ship-borne, water-cooled cabinet, and also conducts a heat simulation to check the cooling effect and optimize the structural design. Zhang [
8] calculates the influence of the outlet pressure of the switching power supply on the wind speed of the fan inside the switching power supply and the impact of the inlet wind speed of the power supply on the temperature of the heat source inside the power supply by theoretical calculation and numerical simulation, verifies the rationality of the heat dissipation characteristics and structural design of the model, and provides valuable data for the configuration, simulation, optimization, and application of related equipment. Huang [
9] uses mathematical modeling and finite element analysis methods. ANSYS simulation analysis software is used to analyze the heat dissipation structure of a high-power microwave power supply and proposes structural optimization measures for cooling water flow, fan inlet flow, and fin thickness. Niu [
10] establishes the thermal resistance model of the power module. By analyzing the coupling relationship between the primary heat sources, the temperature rise was calculated, and the thermal simulation model was established by Flothem software to verify the correctness of the thermal resistance model. Given the thermal stress concentration point, the thermal performance optimization design scheme was proposed. However, these software-based modeling solutions only stay in the ideal simulation stage; the thermal conductivity of heat dissipation materials, power module characteristics, room temperature changes, and other factors are not included in the simulation model, resulting in a large gap between the model and the actual application scenario. The ultimate purpose of simulation is only to improve the heat dissipation structure, not to fundamentally solve the heat dissipation problem. Secondly, other thermal simulation models also verify the simulation model of thermal resistance. Therefore, there is no support for and verification of actual data for the model’s validity.
5. Conclusions and Future Work
The wide application of miniaturized multi-board cases with high-power and high-density thermal design has become essential. However, most existing solutions stay in the thermal simulation stage, optimizing heat dissipation structure. There are no actual high-density designs and load high-power tests. In addition, intelligent monitoring and temperature regulation measures are also not adopted. In this paper, a miniaturized and high-power density electronic case is designed. The power array is composed of DC/DC modules with high efficiency and the technology of parallel current equalization. Magnesium and aluminum alloy materials are used to consider the electronic case’s surface strength and electromagnetic compatibility to enhance thermal conductivity. Heat dissipation mode accelerates conduction heat dissipation based on optimizing heat dissipation holes, adding fan groups to enhance heat exchange on the surface and inside of the conduction case. Automatic control modules are designed to form monitoring and feedback control mechanisms. The heat dissipation design of the miniaturized electronic case is proven to guarantee its regular operation after high temperature and high load environment tests. Compared with the mature miniaturized electronic case, the load power test is 16 times the current load power. When the heat dissipation effect is the same, the power density is about 10 times higher, and the performance is better.
The electronic case designed in this article is installed in a fixed and closed environment on land for testing. These system architectures, including features with confined space limitation (less than 10,000 cm), high power output (more than 10,000 W), long working hours (more than 2 h), and variable output power (between 0–10,000 W), would benefit from this cooling configuration. For example, it could be used at high altitudes or in deep water high-speed moving environments. In that case, some DC/DC modules may fail to work due to changes caused by shock, vibration pressure, and temperature between internal and external heat dissipation channels, resulting in a decline in output power. The next step is to simulate a high altitude or deep water dynamic operating environment and test the electronic case with load to verify the effectiveness and reliability of the thermal design.