There are two ways of heat dissipation for key switch, which are the main ways of heat dissipation for key switch. Better understanding of the heat dissipation performance of key switch can help us to use it for a long time, so it is very necessary to understand it. Please find out.
First: Natural Cooling and Heat Dissipation
Natural cooling mode is the traditional cooling mode in the early stage of switching power supply, which mainly relies on large metal radiators for direct heat conduction heat dissipation. Heat transfer Q = KA Delta t (K heat transfer coefficient, A heat transfer area, Delta t temperature difference). When the output power of the rectifier increases, the temperature of its power components will rise, and the temperature difference of Delta T will also increase. So when the heat transfer area of rectifier A is enough, its heat dissipation has no time lag, the temperature difference of power components is small, and its thermal stress and thermal shock are small. But the main disadvantage of this method is the large volume and weight of the radiator. The winding of transformer is to reduce the temperature rise as much as possible to prevent the temperature rise from affecting its working performance, so the material selection margin is large, and the volume and weight of transformer are also large. Rectifier material cost is high, maintenance and replacement is inconvenient. Because of its low requirement for environmental cleanliness, there are still some applications for small capacity communication power supply in some small professional communication networks, such as electricity, oil, radio and television, army, water conservancy, national security, public security, etc.
The Second Cooling and Heat Dissipation Method for Fans
With the development of fan manufacturing technology, the working stability and service life of fans have been greatly improved. The average trouble-free time of fans is 50,000 hours.
The heavy radiator can be subtracted by fan cooling, which greatly improves the volume and weight of the rectifier and reduces the cost of raw materials. With the intensification of market competition and the decline of market price, this technology has become the main trend at present.
The main disadvantage of this method is that the average fault-free time of the fan is shorter than that of the rectifier 100,000 hours. If the fan fails, the failure rate of the power supply will be greatly affected. Therefore, in order to ensure the service life of the fan, the speed of the fan varies with the temperature in the equipment. Its heat dissipation Q = K m Delta t (K heat transfer coefficient, m heat transfer air quality, Delta t temperature difference). The air quality of M heat exchanger is related to the speed of the fan. When the output power of the rectifier increases, the temperature of the power components will rise. The change of the temperature of the power components to the rectifier can detect the change, and then to increase the speed of the fan to enhance heat dissipation, there is a great lag in time. If the load often changes abruptly or the input of electricity fluctuates greatly, the power components will change rapidly in heat and cold. The thermal stress and thermal shock caused by the abrupt temperature difference of the semiconductor will lead to stress cracks in different parts of the components. Make it invalid prematurely.
The heat dissipation mode of key switch must be correctly used and better understood so that it can be used.
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