DC / DC module power supplies with its compact size, performance, Sublime, a notable feature easy to use, in communications, networking, industrial, railway, military and other fields increasingly widely used. Many system designers have recognized: the right to use reasonable DC / DC power modules, you can save the power supply design, debugging trouble, will mainly focus on their areas of expertise, so that can not only improve overall system reliability and design level and, more importantly, shorten the product development cycle, as in the fierce competition in the market-leading success to win valuable business opportunities. So, how to properly use reasonable DC / DC module power supply it, the author from the DC / DC power module design and development point of view, combined with the company in recent years Dingli letter promoting the use of the power module to get the process user feedback, to talk about this The problem for the general system for reference.
DC / DC module power supply options
Choose to use the DC / DC module power supplies in addition to the basic voltage conversion, there are several aspects to consider:
1. Rated power
Actual use of power is generally recommended power supply module power rating of 30 ~ 80% is appropriate (specific ratio of the size but also with other factors, will be mentioned later.), The power supply within the module performance of all aspects of play are quite adequate and stable reliable. Load too light a waste of resources, too much is on the temperature, reliability adversely. All modules have a certain power overload, such as Dingli letter up to 120 products to 150%, but still not recommended to work long hours under the conditions of overload, after all, this is a short-term emergency measure.
Module power package a variety of forms, there are also conform to international standards, there are also non-standard, on the same products, the same power products have different packaging, the same package have different power, then select the package then how? There are three aspects: ① the volume will be under a certain power as small as possible in order to the rest of the system more space for more features; ② try to select the packaging of products conform to international standards, since compatibility is better, not limited to 12 Suppliers of; ③ should be scalable, easy system expansion and upgrades. Select a package, system upgrades as features for greater power on the power supply, power supply module Fengzhuang remain unchanged Xitongxianlu Ban Shejikeyi Bubigaidong, upgrade greatly simplified Chanpin upgrading and save time. Dingli letter to the company high-power module power products as an example: all conform to international standards for the industry widely used semi-brick, full brick package, with VICOR, LAMBDA is fully compatible with other famous brands, and half-brick power covering 50 ~ 200W, All brick cover 100 ~ 300W.
3. Temperature range and reduced the amount of use
Power module manufacturers generally have several temperature range of products available for use: commercial grade, industrial grade, military grade, etc., in the choice of power supply module must be considered when the actual needs of the working temperature range, because the temperature levels of different materials and different manufacturing processes price vary widely, poor choice will affect the use, and would have given serious consideration. There are two ways you can choose: one under the use of power and package options, if the volume (package) under certain conditions Shiji close to the rated power using power Yijing, Name nominal temperature of the module would be considerably Yangemanzu actual Xu Yao even a slight margin. Second, under the temperature range to choose, if chosen due to cost considerations smaller temperature range of products, but sometimes the temperature approaching the limit of the situation, how should we do? Derating. Select power or package that is larger product, such a "big horse cart" to lower temperature, to a certain extent, alleviate the problem. Derating ratio varies with the power rating, usually more than 50W for the 3 ~ 10W / ℃. Short or wide temperature range of product selection, better power utilization, packaging and more smaller, but higher prices; or select the general temperature range of products, lower prices, power margin and would have a large number of packages. Should be considered a compromise.
4. Operating frequency
Generally speaking, the higher the frequency, output ripple noise even small, dynamic response and better power supply, but the requirements of magnetic components, especially the higher the cost will increase, so the switching frequency of domestic multi-module power supplies Following in the 300kHz, 100kHz and even some that only about so difficult to meet the dynamic response under load change requirements, thus demanding occasion to consider the application of the products with high switching frequency. On the other hand when the module power supply switching frequency close to the signal frequency of oscillation when the easily lead to beat, when used should take this into account. Dingli letter module power supply switching frequency up to 500kHz, with excellent output characteristics.
5. Isolation Voltage
General occasions the use of the module power supply is not very high isolation voltage requirements, but can guarantee a higher isolation voltage power supply module has a smaller leakage current, higher security and reliability, and EMC characteristics are better, so the industry general level of isolation voltage 1500VDC above.
6. Fault protection
The statistical data show that the effective time of the module power supply within the expected failure is mainly due to external fault conditions, damage. The normal use of the probability of failure is very low. Therefore, the power module to extend the life, increase system reliability an important part is to choose the perfect product protection, that the external circuit in the module power module power supply failure can automatically protect the state which is not permanently disabled, external fault disappears should automatically return to normal. Module power protection should include at least input over-voltage, under voltage, soft start protection; output over voltage, over current, short circuit protection, power products also have over-temperature protection.
7. Power and efficiency
According to the formula, in which Pin, Pout, P module power consumption respectively, input, output power and its power loss. It can be seen that the output power under certain conditions, loss of P consumption module is small, the higher the efficiency, temperature rise is low, longer life. In addition to full normal wear and tear, there are two notable losses: loss of load loss and short circuit (output short-circuit when the module power consumption), as the two smaller loss, indicating that the higher the efficiency modules, in particular, failed to take short-circuit out measures that could last a long time, the smaller short-circuit losses are therefore greatly reduced the chances of failure. Of course, the smaller the loss is also more energy-saving requirements.
Module power supply application notes
1, using a very light load
Module power supply has a minimum load restrictions, different manufacturers are generally about 10% because the load too light when the energy storage device freewheeling current difficulties will not occur Lian Xu, leading to unstable output voltage, which is by the power supply itself working principle of the decision. However, if the user does have light-load or no load conditions used in how to do it, most convenient and effective way is to add some dummy loads, about 2% of output power can be preset by the module manufacturer factory, also can be Users outside of the module to install the appropriate resistor as the load. It is noteworthy that if you choose the former, the module efficiency will decrease. However, some topologies have no minimum load restrictions, such as the Kingdoms letter's power to meet the E series modules users from no load to full load in normal use.
2, multi-output power distribution
Select multiple output power supply module should pay attention to different output power distribution between. To dual product, for example, there are two types: two-way balance the load, that is the same size as the current dual; the other is the unbalanced load, or main, side roads are not the same load current, a large main road , bypass roads small. For this product, select the side roads and main road proposed power ratio 1 / 5 to 1 / 2 is appropriate, within the side roads in this range of voltage stability can only be guaranteed (to within 5%), or bypass roads voltage will high or low. On the other hand, if the load should not have the same dual also advised not to use load balancing based power modules, because this power supply specifically designed for the symmetrical load, if the load imbalance Side voltage accuracy is not high.
3, to lower the temperature rise of the power supply module
Module within the device's operating temperature will directly affect the life of the power module, the device temperature, the lower the longer module life. In certain operating conditions, the module power consumption is a certainty, but can improve the heat dissipation module power supply to reduce its temperature, thus greatly extending its life. For example: 50W power supply module must be installed above the radiator, the radiator's surface area more conducive to heat, and the installation direction of the radiator should be conducive to the natural convection of air power in more than 150W can be installed outside the radiator installed Fan forced air cooling. In addition, the environmental temperature is high or poor ventilation conditions where the module to be used to reduce the power dissipation derating to reduce temperature and prolong life.
4, a reasonable reduction of mechanical stress to install
Module power supply leads are metal pin means, the module power supply and the external circuit, the metal pin and the module power supply circuit within the road are connected by welding. In some special occasions, large mechanical vibration strength, especially in high-power module power supply but also install the radiator, the situation is more serious. Although the module power supply thermal insulation within the general potting rubber components can play a better role of a buffer to protect, but the solder joints could not withstand strong vibration stress and fracture, resulting in the work of the module power supply failure, then the basis must be welded then take the other fixed and mitigation measures, such as clamps or bolts can be used (for a screw module) the module with the chassis, a relatively large circuit boards and other components fixed good vibration performance, and among them a number of flexible material to cushion pad vibration of the stress.
In short, the module power supply and other components, like only a carefully selected, can be reasonably applied to maximize the performance, reliability, full security, power supply module also will be more widely used!