What are the ways to do a good job of cooling the power supply?

       When electrical engineers mention the term "power management", most people think of MOS tubes, converters, transformers, etc.  

       In fact, power management is much more than that.  

       The power supply will generate heat when it is working, and continuous temperature rise will cause performance changes, which may eventually lead to system failures. In addition, heat will shorten the life of components and affect long-term reliability.  

       Therefore, power management also involves thermal management. Regarding thermal management, there are two points of view that need to be understood:  

       "Micro" issues

       A single component has overheated due to excessive heat generation, but the temperature of the rest of the system and the case is within the limit. 

       "Macro" issues  The temperature of the entire system is too high due to the accumulation of heat from multiple heat sources. 

       The engineer needs to determine how many of the thermal management issues are micro and macro, and the degree of correlation between the two.  

       The simple understanding is that even if the temperature rise of a heat-generating component exceeds its allowable limit and causes the entire system to heat up, it does not necessarily mean that the entire system is overheated, but the excess heat generated by the component must be dissipated.  

       So where does the heat go? 

       Scattered to a colder place, it can be the adjacent part of the system and the chassis, or it can be outside the chassis (only possible when the outside temperature is lower than the internal temperature).  

       Modeling and comprehensive simulation  Separate passive systems are larger in size, but more reliable and efficient, and fans can play a role in situations where passive cooling cannot be used alone.  

       Which system to choose for cooling is often a difficult decision.  

       At this time, it is necessary to determine how much cooling air is needed and how to achieve cooling through modeling and simulation, which is essential for efficient thermal management strategies.  

       For the miniature model, the heat source and its heat flow path are characterized by their thermal resistance, and the thermal resistance is determined by the material, quality and size used.  

       Modeling shows how heat flows from the heat source and is also the first step in evaluating components that cause thermal accidents due to their own heat dissipation.

       For example, device suppliers such as high heat dissipation ICs, MOSFETs, and IGBTs usually provide thermal models that can provide details of the thermal path from the heat source to the surface of the device.  

      Once the thermal load of each component is known, the next step is to model at a macro level, which is both simple and complex:  Adjust the size of the air flow through various heat sources to keep its temperature below the allowable limit; use air temperature, unforced air flow available flow, fan air flow and other factors to perform basic calculations to roughly understand the temperature situation.  

       The next step is to use the model and location of each heat source, PC board, shell surface and other factors to perform more complex modeling of the entire product and its packaging.  

       Finally, modeling has to solve two problems:  The problem of peak and average dissipation. For example, a steady-state component with a continuous thermal dissipation of 1W and a device with a thermal dissipation of 10W but with a 10% intermittent duty cycle have different thermal effects.  

       That is to say, the average heat dissipation is the same, and the related heat mass and heat flow will produce different heat distributions. Most CFD applications can combine static and dynamic analysis.

       The imperfection of the physical connection between the surface of the component and the miniature model, such as the physical connection between the top of the IC package and the heat sink. 

       If the connection has a small distance, the thermal resistance of this path will increase, and it is necessary to fill the contact surface with a thermal pad to enhance the thermal conductivity of the path.

      Thermal management can reduce the temperature of the components in the power supply and the internal environment, which can prolong product life and improve reliability.  

      But thermal management is an integrated concept, if broken down to the minutiae, it is a huge subject.  

      It involves the trade-offs of size, power, efficiency, weight, reliability, and cost. The priority and constraints of the project must be evaluated.