Posted on 03 July 2019

Low Profile AC/DC Power Supplies

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The modern market of AC / DC power supplies is widely represented by products with operating temperature range of minus 10 to +70 ° C and of relatively larger size. In addition, power supplies of power more than 150 watts often has in its composition such potentially unreliable unit, such as built-in fan.

By Alexander Goncharov, P. h.D., Konstantin Stepnev and Oleg Negreba, AEPS Group


There are operating conditions for industrial and special purpose machinery with special requirements to power supplies for compactness and resistance to intense influence of mechanical, climatic and chemical factors (vibration, wide temperature range, dust, salt fog, etc.).

AEPS Group has developed universal AC / DC power supplies that are designed to power industrial and special equipments in all areas of critical application with respect to combination of wide temperature range, resistance to external influencing factors and low profile compact design. Below, you will get a detailed overview of AEPS Group power supplies and their functionality in three main area: Industrial, Standard and Military.

Radio electronic equipments for «Military» and «Industrial» category products typically require rated stabilized DC voltage of two to ten from the range 3.3 V, 5 V, 9 V, 12 V, 15 V, 24 V, 27 V, 36 V, 48 V, 60 V for powering, which are generated from AC voltage of 220-230 V, 47 ... 440 Hz. Rated voltage of 14 V, 28 V and 56 V (taking into account drop in ORing diode) are also used while operating with buffer battery.

Currently, two structures, shown in Figures 1 and 2, are widely used for distributed power systems.

Distributed power supply system without intermediate conversation

Distributed power supply system with intermediate conversation

Each of the given structure of power distribution has its own advantages and disadvantages.

The disadvantage of the first structure is the remoteness of power supplies from supply loads due to the need to exclude a large number of high voltage wires of input mains.

However, maximum efficiency and minimum heat loss is achieved under this construction of power supply, which is often the determining factor. The second structure has greater flexibility and unlimited functional capabilities. For example, one can separately remote control each DC / DC module. Only in such structure, power supplies can be brought maximum closer to the electronic devices being powered.

Power Supply Category

The range of AC / DC power supplies is categorized as «Standard», «Industrial» and «Military».

The low cost AC / DC power supplies of «Standard» category are designed to power a variety of industrial equipment for general use. They are produced on standard component base, supplied without sealing/potting and operate in temperature range of minus 10 ... + 70 ° C. The optimum configuration for most applications reduces the cost while creating power supply system.

AC / DC power supplies of «Industrial» category with range of operating temperature minus 40 ... + 85 ° C is designed to power industrial equipment of different climatic versions. Power supplies are made on component base, tested in wide range of temperatures and filled with heat conducting compound that protects the components from adverse external influencing factors.

Composition, basic characteristics and service functions of AC-DC AEPS Group modules

AC / DC power supplies of «Military» category have operating temperature range of minus 50 ... + 85 ° C and produced on custommade component base. They have polymer thermal conducting sealing and are designed for powering industrial and special equipments in most severe climatic conditions. These modules undergo special types of temperature and limit tests, including butn-in test with extreme conditions modes of on and off.

Modules of «Industrial» and «Military» category are produced as per design document coordinated with instances determining the requirements towards quality and parameters of article for defense application.

AC/DC power supplies are designed for using in various configurations of power supply systems. Hence, modules of power up to 200 W inclusive is optimum for use as power source in power supply system without intermediate conversion (figure 1). They can have up to three output channels and built on the basis of flyback convertor with galvanic isolation between the input and output (figure 3).

Block diagram of modules of output power up to 200 W inclusive

Modules of output power above 200 watts usually have one output channel and can be used as a centralized stabilizer in the structure shown in Figure 2. They are a half bridge asymmetrical forward converter with galvanic isolation between input and output, shown schematically in Figure 4.

Block diagram of modules of output power above 200 W

Power supplies modules not only have high specific power/energy characteristics, but have a special design for common heat-removal base thus reducing the volume required for power supply system.

Figure 5 shows schematically the design of modules in section. There is an aluminum casing in the module base on which heat is removed from all thermal loaded components of the circuit - power transistors, diodes, transformers, chokes. As a result, the module casing also acts as a radiator having good heat dissipation. Thus, KS500A-230WS24-SCN series power supplies without additional heat sink under normal climatic conditions are capable to supply load of power around 200 watts, and with radiator and forced cooling – power load of 500 W up to ambient temperature of + 85 °C.

Schematic design of module in cross section

The casing has mounting holes for installation of modules on the heat sink; there is also version for mounting on DIN-rack. Module PCB is protected against mechanical and climatic influences by a thin-walled steel cover. Such a design of casing with four sides closing the power supply components further improves its electromagnetic compatibility (EMC) with other equipments. Power supplies versions with polymer potting (heat conducting sealing) are produced for better protection against external influencing factors in industrial and special-purpose equipments, which eliminates damage to power supplies due to vibration or dust, moisture and salt fog.

There are input and output screw terminal blocks on the module PCB’s, modification with soldering pin leads or flexible mounting lead is also possible.

The described implementation of technical solution allows to confidently compete AC/DC power supplies of AEPS Group with similar products from other manufacturers.



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