What should we pay attention to when selecting a power supply module

What should we pay attention to when selecting a power supply module?The power module is a power supply that can be directly mounted on a printed circuit board and is characterized by an application specific integrated circuit(ASIC),a digital signal processor(DSP),a microprocessor,a memory,and a field programmable gate array(FPGA).)and other digital or analog loads provide power.So what should you pay attention to when choosing a power module?

First,the rated power

In theory,when selecting a module,the power is as large as possible,so that the system can be operated with higher requirements.But the greater the power,the larger the volume,and the greater the cost.Therefore,when designing the power module,it is better to select the working power of the product to maintain 30-80%of the power module used,because for the general module,the performance of the module power supply is compared in this power range.Stable and reliable,it is more conducive to the long-term operation of the module.Choosing too large a power product will cause waste;if you choose just too little or too little power,it will easily cause the load to be too heavy,the light system will be unstable,and the heavy will burn the components.Although some power module products are currently overloaded,they can only be used for emergency purposes.They are not recommended for long-term use.Of course,this depends on different products and different requirements.You can choose the most appropriate power module according to your product characteristics and needs.

Second,the package form

There are many different types of power modules,and some of the commonly used products are in line with international standards,and many are non-standard products.And the same company's products,the same power will have different packaging forms;on the contrary,the same package will have different power,this can be based on the requirements of their own products,a reasonable choice of packaging.Generally consider three points:1.Under the premise of power determination,the package size is as small as possible to meet the heat dissipation requirements of the product,which is more conducive to the volume control of the product,and can also leave the space to more important parts.Of course,if the volume is not very important,in order to make the product more weighty,you can also choose a larger size,and you can get better heat dissipation.2.Try to use international standard products.Because these products are used and verified extensively,they are relatively mature products,thus reducing the risk of product development.And for some reason,it is easier to replace other brands of the same standard products for some reason.3,it is best to have scalability,in order to facilitate the expansion and upgrade.For example,in the same package,due to the upgrade of the product,the power can be replaced,but the size and package remain unchanged,so that the product can be upgraded quickly.So it can be seen that the package form is also considered according to their own needs.Especially for some products with their own characteristics,manufacturers can be required to carry out independent development to meet the requirements of their own products,but also to prevent people from plagiarizing products to protect their products.Then continue to improve in use,so that the power products are getting better and better.

Third,the temperature range and working environment

At present,the classification of power modules is mainly commercial grade,industrial grade and military grade,and different grades are required for the environment,such as working temperature,vibration,humidity,dust,and the like.Therefore,when selecting a module product,it is necessary to fully consider the environment in which the product is located.If it is not properly selected,it will affect the use.Users should take this requirement seriously.If there are special requirements,ask the engineer clearly to prevent the progress of the work.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),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 3~10W/°C above 50W.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 the general temperature range is selected,the price is lower,and the power margin and package form are larger.Should be compromised.

For other special requirements,you can contact the engineer to confirm the environment in which your product is used.

Fourth,the 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 requirements for components,especially magnetic materials,are also higher.The switching frequency of a typical module power supply is below 300 kHz or even lower.Therefore,it is necessary to select a product with a higher switching frequency when the demand is high.

Five,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.

Sixth,fault 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 automatically return to normal after disappearing.The protection function of the module power supply should include at least input overvoltage,undervoltage,and soft start protection;output overvoltage,overcurrent,and short circuit protection,and high-power products should also have over-temperature protection.