Thermal cooling design for power supply devices

     We all know that thermal management is an important aspect of power management. It needs to keep components and systems within temperature limits. Passive solutions start with heatsinks and heat pipes, and can use fans for active cooling to enhance the cooling effect.   

     Component level and finished product level system modeling allows designers to make a first-order approximate analysis of the refrigeration strategy. Using computational fluid dynamics for further analysis can fully understand the overall heat situation and the impact of changes in refrigeration strategy. All thermal management solutions involve trade-offs in size, power, efficiency, weight, reliability and cost, and must evaluate the priorities and constraints of the project.

     All thermal management solutions follow the basic principles of physics. In the cooling mode, there are three ways of heat conduction: radiation, conduction and convection

      For most electronic systems, the cooling required to achieve is to let the heat leave the direct heat source by conduction, and then transfer it to other places by convection. The design challenge is to combine various thermal management hardware to effectively achieve the required conduction and convection. There are three most commonly used cooling elements: radiator, heat pipe and fan. Radiators and heat pipes are passive cooling systems without power supply, which also includes naturally induced conduction and convection methods. In contrast, the fan is an active forced air cooling system.

Heatsink Cooling:

     The heatsink is an aluminum or copper structure, which can obtain heat from the heat source through conduction and transfer the heat to the air flow (in some cases, to water or other liquids) to realize convection. Radiators come in thousands of sizes and shapes, from small stamped metal fins connecting a single transistor to large extrusions with many fins that can intercept and transfer heat to the convective air flow.

      One of the advantages of the heatsink is that there are no moving parts, no operating costs, and no failure modes. Once a properly sized heatsik is connected to the heat source, as the warm air rises, convection will naturally occur, starting and continuing to form air flow. Therefore, these advantages are very important when using a heatsink to provide smooth air flow between the inlet and outlet of the heat source. Moreover, the inlet must be below the radiator and the outlet must be above; Otherwise, the hot air will stagnate on the heat source, which will further worsen the situation.

Adding Heatpipes:

      The function of heat pipe is to absorb heat from the heat source and transfer it to the colder area, but it itself does not act as a radiator. When there is not enough space near the heat source to place the radiator or the air flow is insufficient, the heat pipe can be used. The heat pipe has high efficiency and can transfer heat from the source to a place more convenient for management.

Adding cooling Fan:

      Obviously, fans will increase  costs, require space, and increase system noise. As an electromechanical device, the fan is also prone to failure, which consumes energy and affects the efficiency of the whole system. However, in many cases, especially when the air flow path is curved, vertical or blocked, they are usually the only way to obtain sufficient air flow. Many applications use thermally controlled fans that operate only when needed to reduce speed, thereby reducing power consumption, and use blades that minimize noise at the optimal operating speed.

Modeling and thermal simulation:

     Modeling and simulation are essential for an efficient thermal management strategy to determine how much cooling air is required and how cooling is achieved. The airflow through various heat sources can be sized to keep its temperature below the allowable limit. Using air temperature, available flow of non forced air flow, fan air flow and other factors for basic calculation, we can roughly understand the temperature condition.

       By making some adjustments, designers can see whether larger air ports require more air, determine whether other air flow paths are more effective, identify differences in the use of larger or different radiators, investigate the use of heat pipes to move hot spots, etc. These CFD modeling software packages can generate tabular data and color images of heat dissipation. Changes in fan size, airflow and position are also easy to model.

      Power management also thermal management, especially how the cooling of power related functions will affect the thermal design and heat accumulation. In addition, even if the components and systems continue to work within the specification range, the increase of temperature will cause performance changes with the change of component parameters. Overheat can also shorten the life of components and thus shorten the mean time between failures, which is also a factor to be considered to ensure long-term reliability.