Friends who have a certain power supply design basis are certainly not familiar with the DC module power supply, and can even skillfully use the DC module power supply in the circuit. But how to choose a reasonable and convenient DC module power supply? This article will analyze the selection of module power supply from the perspective of development and design, to help circuit designers to quickly understand, and as a reference. DC/DC module power supply selection In addition to the most basic voltage conversion functions, there are several aspects to consider when using DC/DC module power supplies: rated power It is generally recommended that the actual power used is 30 to 80% of the rated power of the module power supply (the specific ratio is also related to other factors, which will be mentioned later). In this power range, the performance of all aspects of the module power supply is relatively sufficient and stable. . Too light a load causes waste of resources, and too heavy is unfavorable for temperature rise and reliability. All module power supplies have a certain overload capacity, but it is still not recommended to work under overload conditions for a long time. After all, this is a short-term emergency plan. Package form Module power supply packages are available in a variety of ways, in accordance with international standards, non-standard, as well as the same company products, the same power products have different packages, the same package has different power, then how to choose the package form? There are three main aspects: 1. The volume should be as small as possible under certain power conditions, so that more space and more functions can be given to other parts of the system. 2, try to choose products that meet the international standard packaging, because the compatibility is better, not limited to one or two suppliers. 3. It should be scalable to facilitate system expansion and upgrade. Selecting a package, the system requires higher power supply requirements due to functional upgrades, the power module package remains unchanged, and the system board design can be modified without modification, which greatly simplifies product upgrades and saves time. Take Dinglixin's high-power module power supply products as an example: all meet the international standards, and are widely used in the industry for half-brick and full-brick packaging. They are fully compatible with famous brands such as VICOR and LAMBDA, and the power range of half-brick products covers 50-200W. The whole brick product covers 100~300W. Temperature range and derating 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 must consider the actual operating temperature range, because the temperature grade is different materials and manufacturing processes Prices vary widely, and improper selection can affect usage, so they have to be carefully considered. There are two options: one is to choose according to the power and package form. 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 strictly meet the actual needs or even Slightly marginal. The second is to choose according to the temperature range. If a product with a smaller temperature range is selected due to cost considerations, but sometimes there is a temperature approaching the limit, what should I do? Derating. That is to choose the power or package a larger product, so that the "big horse car", the temperature rise is lower, can alleviate this contradiction to some extent. The derating ratio varies with the power level, and is generally 3 to 10 W/° C above 50 W. In short, either a wide temperature range of products is selected, power utilization is more adequate, and the package is smaller, but the price is higher. Either choose a general temperature range product, the price is lower, the power margin and package form are larger. Should be compromised. working frequency Generally speaking, the higher the operating frequency, the smaller the output ripple noise, and the better the dynamic response of the power supply. However, the higher the requirements on components, especially magnetic materials, the higher the cost, so the switching frequency of domestic module power products is higher. In order to be below 300 kHz, and even some are only about 100 kHz, it is difficult to meet the dynamic response requirements under load-changing conditions. Therefore, high-requirement applications should consider products with high switching frequency. On the other hand, when the module power switch frequency is close to the signal operating frequency, it is easy to cause beat oscillation, and this should be taken into consideration when selecting. Dinglixin module power switch frequency up to 500kHz, with excellent output characteristics. Isolation voltage In general, the power supply isolation voltage requirement for the module is not very high, but the higher isolation voltage can ensure that the module power supply has less leakage current, higher safety and reliability, and better EMC characteristics. The universal isolation voltage level is above 1500 VDC. Fault protection Relevant statistics indicate that the main cause of failure of the module power supply within the expected effective time is damage under external fault conditions. The probability of failure of normal use is very low. Therefore, an important part of extending the power life of the module and improving the reliability of the system is to select a product with perfect protection function, that is, when the external circuit of the module power supply fails, the module power supply can automatically enter the protection state without permanent failure, and the external fault should be able to disappear. Automatically resumes normal. The protection function of the module power supply should include at least input overvoltage, undervoltage, and soft start protection. Output overvoltage, overcurrent, short circuit protection, high power products should also have over temperature protection. Power consumption and efficiency According to the formula, the Pin, Pout, and P consumptions are the module power input, output power, and self power loss, respectively. It can be seen that under certain conditions of output power, the smaller the module loss P consumption, the higher the efficiency, the lower the temperature rise and the longer the life. In addition to the full load normal loss, there are two losses worth noting: no-load loss and short-circuit loss (module power loss when the output is shorted), because the smaller the two losses, the higher the module efficiency, especially the short-circuit is not taken in time. In the case of measures, it may last for a long time, and the smaller the short-circuit loss, the greater the probability of failure. 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