The design of communication switching power cooling technology must first meet the various technical performance requirements of the industry. In order to better adapt to the special environment of the communication room, its cooling method is required to be highly adaptable to changes in ambient temperature. At present, there are three commonly used cooling methods for rectifiers: natural cooling, pure fan cooling, and a combination of natural cooling and fan cooling.
Natural cooling has the characteristics of no mechanical failure and high reliability; no air flow, less dust, and conducive to heat dissipation; no noise. Pure fan cooling has the characteristics of light equipment weight and low cost. The technology combining fans and natural cooling has the characteristics of effectively reducing the size and weight of equipment, long fan service life, and strong fan fault self-adaptation ability.
Natural cooling
Natural cooling is the traditional cooling method of the early switching power supply. This method mainly relies on large metal radiators for direct heat conduction heat dissipation. Heat exchange Q = KA△t (K heat transfer coefficient, A heat transfer area, △t temperature difference). When the output power of the rectifier increases, the temperature of its power components will rise, and the △t temperature difference will also increase. Therefore, when the heat exchange area of rectifier A is sufficient, there is no time lag in its heat dissipation, the temperature difference of the power components is small, and its thermal stress and thermal shock are small.
However, the main disadvantage of this method is that the heat sink is large in size and weight. The winding of the transformer is to reduce the temperature rise as much as possible to prevent the temperature rise from affecting its working performance, so the margin of its material selection is large, and the volume and weight of the transformer are also large. The material cost of the rectifier is high, and maintenance and replacement are inconvenient. Because it does not require high environmental cleanliness, it is currently used in some small professional communication networks for small-capacity communication power supplies, such as electricity, petroleum, radio and television, military, water conservancy, national security, public security, etc.
Fan cooling
With the development of fan manufacturing technology, the working stability and service life of the fan have greatly improved, and its average failure-free time is 50,000 hours.
After using fan heat dissipation, the bulky radiator can be removed, which greatly improves the volume and weight of the rectifier and greatly reduces the cost of raw materials. With the intensification of market competition and the decline in market prices, this technology has become the main trend at present.
The main disadvantage of this method is that the average failure-free time of the fan is shorter than the 100,000 hours of the rectifier. 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 changes with the temperature change in the equipment. Its heat dissipation Q = Km△t (K heat transfer coefficient, m heat exchange air quality, △t temperature difference). m heat exchange air quality is related to the speed of the fan. When the output power of the rectifier increases, the temperature of its power element will rise.
There is a large time lag from the change in the temperature of the power element to the rectifier being able to detect this change, and then to increasing the speed of the fan to enhance heat dissipation. If the load often changes suddenly, or the mains input fluctuates greatly, it will cause the power element to change rapidly from hot to cold. The thermal stress and thermal shock generated by this sudden semiconductor temperature difference will cause stress cracks in different material parts of the component. Make it fail prematurely.
Combination of fan and natural cooling
Due to changes in ambient temperature and load, the power supply consumes heat energy when working. The combination of fan and natural cooling can dissipate the heat energy faster. This method can reduce the area of the radiator while increasing the fan heat dissipation, so that the power components work under relatively stable temperature field conditions, and the service life will not be affected by changes in external conditions.
This not only overcomes the shortcomings of the power component heat dissipation adjustment lag of pure fan cooling, but also avoids the overall reliability of the rectifier affected by the low service life of the fan. Especially when the ambient temperature of the computer room is very unstable, the cooling technology combining air cooling and self-cooling has better cooling performance. The material cost of the rectifier in this way is between pure fan cooling and natural cooling, with low weight and easy maintenance.
Especially when using intelligent air cooling and self-cooling technology, the rectifier can keep the module temperature rise small under low load working conditions, and the module fan is in a low-speed operation state.
Under high load working conditions, the module heats up. The module temperature rises by more than 55°C. The fan speed increases linearly with temperature changes. Fan fault detection in place, after the fan fails, the fan fault current limiting output, and the fault alarm at the same time. Since the number of fan operations is related to the load size, the service life of the fan is longer than that of pure air cooling, and its reliability is greatly improved.
The communication switching power supply adopts a cooling method that combines fans and natural cooling. It can effectively reduce the internal working temperature of the rectifier and extend the service life of the device when the ambient temperature is high, and the rectifier fan can reduce the speed when the ambient temperature is low and the load is low, thereby extending the service life of the fan. The heat sink is used for heat dissipation, and the device spacing and creepage distance can be relatively far. In the case of high humidity, the safety performance is high. The rectifier is small in size and light in weight, making maintenance work easy.
Summary
In order to ensure the reliable and stable operation of the rectifier of the communication switching power supply, reducing its operating temperature rise is a key technology. It adopts a combination of intelligent air cooling and self-cooling technology. It has technical advantages such as stronger environmental adaptability, long service life, reliability and stability.
