There are several common heat dissipation methods for communication switching power supply rectifier

The design of communication switching power supply cooling technology must first meet the technical performance requirements of the industry. In order to better adapt to the special environment and use environment of the communication equipment room, the cooling method is required to have strong adaptability to the change of ambient temperature. At present, there are three commonly used cooling methods for rectifiers: free cooling, pure fan cooling, natural cooling and a combination of fan cooling. Free cooling has no mechanical failure and high reliability; No air flow, less dust, conducive to heat dissipation; No noise and other features. Pure fan cooling has a device that is lightweight and low-cost. The combination of fan and free cooling technology has the characteristics of effectively reducing the volume and weight of the equipment, the long service life of the fan, and the strong adaptability of fan failure.

1. Natural cooling

The free cooling method is the traditional cooling method in the early days of switching power supply, which mainly relies on a large metal heat sink for direct heat conduction heat dissipation. Heat transfer Q = KA△t (K heat transfer coefficient, A heat exchange area, △t temperature difference). When the output power of the rectifier increases, the temperature of the power element will rise, and the temperature difference of △t will also increase, so when the heat exchange area of rectifier A is sufficient, there is no time lag for heat dissipation, the temperature difference of the power element is small, and the thermal stress and thermal shock are small. However, the main disadvantage of this method is the large size and weight of the heat sink. In order to reduce the temperature rise as much as possible and prevent the temperature rise from affecting its working performance, the material selection margin is large, and the volume and weight of the transformer are also large. The material cost of the rectifier is high, and the maintenance and replacement are inconvenient. Due to its low requirements for the cleanliness of the environment, there are still some applications in some small professional communication networks for small-capacity communication power supplies, such as electric power, petroleum, radio and television, military, water conservancy, national security, public security, etc.

2. Fan cooling

With the development of fan manufacturing technology, the working stability and service life of fans have been greatly improved, and its average time between failures is 50,000 hours.

The use of fan cooling can reduce the bulky heat sink, so that the volume and weight of the rectifier can be greatly improved, and the cost of raw materials can also be greatly reduced. With the intensification of market competition and the decline of market prices, this technology has become the main trend at present.

The main disadvantage of this method is that the average time between failures of the fan is shorter than the 100,000 hours time of the rectifier, and if the fan fails, it will have a great impact on the failure rate of the power supply. 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 the power component will rise, and the change of the temperature of the power element to the rectifier can detect this change, and then increase the speed of the fan to strengthen the heat dissipation, there is a great lag in time. If the load changes abruptly or the mains input fluctuates greatly, it will cause rapid hot and cold changes in the power components, and the thermal stress and thermal shock caused by the sudden semiconductor temperature difference will cause stress cracks in different material parts of the components. Make it fail prematurely.

3. Combination of fan and natural cooling

Due to the change of ambient temperature and load, the heat dissipation energy consumed during the operation of the power supply can be dissipated faster by using a combination of fan and free cooling. In this way, while increasing the heat dissipation of the fan, the heat sink area can be reduced, so that the power components can work under relatively stable temperature field conditions, and the service life will not be affected by the change of external conditions. This not only overcomes the shortcomings of the lag in heat dissipation adjustment of the power components of the pure fan cooling pair, but also avoids the low service life of the fan from affecting the overall reliability of the rectifier. 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 this rectifier is between pure fan cooling and free cooling, with low weight and easy maintenance.

Especially when the intelligent air cooling and self-cooling technology are adopted, the rectifier can be used under low load working conditions, the temperature rise of the module is small, and the module fan is in a low-speed operation state.

Under high load operating conditions, the module heats up. The module warms up to more than 55°C. The fan speed increases linearly with temperature. Fan fault detection in place, after the fan failure, the fan fault current limiting output, and the fault alarm at the same time. Since the number of fan runs is related to the size of the load, the service life of the fan is longer than that of pure air cooling, and its reliability is also greatly improved.

The communication switching power supply adopts a cooling method combining fan and natural cooling, which can not only effectively reduce the working temperature inside the rectifier and prolong the service life of the device under the condition of high ambient temperature, but also reduce the speed of the rectifier fan to work and prolong the service life of the fan under the condition of low ambient temperature and low load. The heat sink is used for heat dissipation, and the device spacing and creepage distance can be relatively far, and the safety performance is high in the case of high humidity. The rectifier is small and lightweight, making maintenance easy.

In order to ensure the reliable and stable operation of the rectifier of the communication switching power supply, it is a key technology to reduce its working temperature rise. It adopts a combination of intelligent air cooling and self-cooling technology. It has the technical advantages of stronger adaptability to the environment, long service life, reliability and stability.