Abstract: Choosing a power supply can have many parameters, such as voltage range, output voltage, power, isolation voltage, efficiency, etc., a little deeper, there are precision, ripple, isolation voltage, EMC, standby power consumption, etc. Will pay attention to the operating temperature parameters of the power supply, may be caused by the negligence of this detail caused by small loss. First, the working temperature range and cost and reliability of the power supply The general manufacturer's module power supply has several temperature range products available: commercial grade, industrial grade, military grade, etc. When selecting the module power supply, it must consider the actual operating temperature range, because the temperature grade is different, the material and The manufacturing process is different, and the price varies greatly. At the same time, the selected temperature range is not suitable, which may bring risks such as poor starting of power, unstable operation, and even burning, which brings many uncontrollable risk factors to the product. Follow the principle of sufficient use and leave a certain margin to avoid over-designing the chicken knife. The derating design can be based on the load power and the actual ambient temperature. Second, the conventional power supply derating selection method There are two options: one is based on the power used and the package type. If the actual power is close to the rated power under certain conditions of volume (package form), then the nominal temperature range of the module must meet the actual needs. Even a little margin. The other is a convenient and effective way to select: from the temperature range, combined with the power for comprehensive comparison, can help engineers quickly find a suitable power supply model. Let's take a look at the specific content of this method. First of all, we need to ensure that the temperature range not only meets the actual needs of the work, but also a little margin. The temperature range requirements are different for different product models. When selecting the temperature range, engineers need to consider the upper limit of the highest temperature and the lowest temperature to avoid unstable system performance after temperature rise or decrease. Happening. For example, the temperature range is selected based on the harsh high temperature and low temperature start-up methods of the test power supply. Refer to Figures 1 and 2. Figure 1 High-temperature start-up test curve of the power supply Figure 2 Low-temperature startup test curve of the power supply If the first condition is met, if the engineer chooses a product with a smaller temperature range because of the cost control problem, then it is necessary to select a product with a larger power or a larger package, which can lower the temperature rise. Can alleviate this contradiction to some extent. Third, according to the experience of derating selection Generally speaking, the ratio of derating of the body will change with the power level. Under normal circumstances, the amount of derating of 50W or more is 3-10W/°C, and the engineer can calculate the amount by this ratio. If the product selected is a wide temperature range, the utilization of the module power supply is sufficient, and the package can be selected to be smaller, but the cost is relatively high; if the product is selected in the general temperature range, the price and The cost is lower, and the power margin and package form must be larger. Both of these situations require engineers to make compromises when the temperature range is determined. Fourth, refer to the manufacturer's manual derating curve design In general, responsible manufacturers will give a clear power VS temperature derating curve. Because the manufacturer knows the key internal data, device characteristics, process parameters and other key data, the derating curve given by the manufacturer has reference significance. Directly according to the derating curve design saves effort and effort. For example, the E0505FS-1W of Guangzhou Zhiyuan Electronics shows the derating curve as shown in the figure below. It can be clearly seen from the figure that the working temperature range is -40~105°C. After the high temperature is above 85°C, the power needs to be reduced. At 105 ° C, the maximum allowable output power is 0.8W. Figure 3 E_FS-1W schematic Figure 4 Temperature derating curve of E0505FS-1W Countertop Electric Oven,Pizza Baking Oven,Fast Cooking Ovens,Electrical Round Oven xunda science&technology group co.ltd , https://www.gasstove.be
