Heat dissipation measures for module power supply

            Regarding the module power supply, its ultra-high power density has been praised by designers. 

            However, while achieving ultra-high power, the shortcomings of poor heat dissipation performance are also exposed. Although designers can improve some specific designs, not every design is suitable. This article will use examples as a benchmark to analyze the heat dissipation problem of the module power supply in a design scheme. The module in this article uses 100W, Vin24VVout5V, uses a single-tube forward circuit, uses UC3843B chip control, does not use active clamping and synchronous rectification, and the operating frequency is 300KHZ. 

            After running, it is found that it cannot actually work at 100W for a long time. Long-term work will cause the MOSFET or the secondary diode to be thermally broken down. 

            So what method should be used to make it work below 100W for a long time? 

            The following two methods have been tested:  

            1. Increase MOSFET: Use multiple MOSFETs in parallel and change the drive. 3843B can not drive multiple MOSFETs, but the effect is not good, not only increases the cost, but also does not solve the problem. And multiple MOSFETs cannot be turned on at the same time, there will always be first, so there will always be a MOSFET breakdown.

            2. Add secondary diodes and use multiple parallel connections. The effect is similar to that of Option 1, but it is not ideal. 

            Let's talk about the solution below. Generally speaking, the heat dissipation performance of the device is related to the thermal conductivity of the insulating material, the pressing force, the thermal conductivity of the shell, the area, and the airflow conditions outside the shell, which can be improved from these points. 

            Perhaps some people have thought of synchronous rectification technology, but even if synchronous rectification technology is used, the efficiency cannot be improved much. The design has reached 90% efficiency, and most of them have reached 89%. 

           The efficiency of synchronous rectification will not be much higher, so there is still a lot of loss, and heat dissipation is still a problem. Or from the perspective of driving waveforms, if the driving capability is not enough, consider adding a push-pull driving circuit. Or you can reduce the frequency of the power supply to reduce switching losses. Another point is the leakage inductance of the transformer. If the leakage inductance is large, a lot of power will be lost and the heat will not be small. 

            The power supply is overheated, and it is easy to cause thermal breakdown (unrecoverable). If a radiator is not added for 100W, heat dissipation is definitely a big problem. 

            This article has carried out a comprehensive analysis of the heat dissipation problem of the module power supply from various angles, and it is convenient for everyone to understand through the introduction of examples. 

            I hope you can find the answers you want in the analysis given in this article.