Isolation or Non-isolation: How to Choose the Right Power Supply?

Most engineers still focus on meeting the input and output voltage and power load requirements when selecting power supplies, which is only the most fundamental requirement. With the continuous development of the industry, the needs of customers vary accordingly. Some only require the function realization and low price; some require to meet the high reliability and low fault tolerance rate, which is caused by the different directions in selection. In general, the selection mainly focuses on conventional parameters, important parameters, and some hidden parameters that are not usually noticed. Of course, reliability is the most concerned parameter at this stage.

Why does the mark of the products show 100VAC-240VAC while the datasheet shows 85VAC-264VAC?

This is mainly for safety certification purposes. When certification authority tests product performance, they will make the input voltage range on the mark fluctuate by +10% and -15%, so the common practice in the industry is to set the input voltage range of 100VAC-240VAC on the mark.

The AC/DC Converters produce instantaneous high current upon load access. Does this influence the module?

If the large instantaneous current of the AC/DC Converters upon load access does not exceed the over-current protection point of the module, it will not have any impact on the module. See the datasheet for the over-current protection point of the module. If the current exceeds the over-current protection point of the module, the module will trigger the protection and voltage dip occur, and then recover.

What is the possible reason for the surface temperature rise of the power module case?

The temperature rise of the power module case depends on the efficiency and loss of the module, and the surrounding environment temperature. Under the normal circumstance, the temperature for power module will remain stable within 30 to 60 minutes upon start-up. The temperature rise is continuously ascending in the earlier stage. If the power module is in a confined space without an effective heat consumption output, the environment temperature will keep rising due to the presence of the heating elements, which also causes the temperature rise of the module.

Why do the positive and negative voltages change when the load of AC/DC positive and negative dual output products is unbalanced?

AC/DC multi- output products generally apply single output feedback design. The output voltage without feedback will fluctuate when the output load is unbalanced. Most of our AC/DC positive and negative dual output products adopt negative output voltage feedback design, so a load imbalance will cause a change in positive output voltages.

Why are ripple & noise high when products operate in the light load?

To lower the standby power consumption of the product and improve the light load efficiency, AC/DC Converters may operate in a skipping cycle mode in the light load condition. The ripple & noises are fairly high but the output voltage is regulated. 

It is a normal phenomenon for fairly high ripple & noise in the light load condition (below 10%). To avoid this situation, it is recommended that customers use a module with load no lower than 10%.

How to eliminate the interference and high noise among power sources of systems?

The crosstalk interference may occur when the switching power sources are supplied power in input-series connection, and especially when the power sources are in parallel connection. The generally adopted method is to add a filter circuit at the input and output terminals, a CM inductor and X capacitor at the input terminal, and a pi filter at the output terminal.

Does the difference in test methods cause high ripple & noise?

Yes. The test methods of switching power supply ripple & noise should comply with some industrial standards, and the parallel cable measuring method or contact measuring method is adopted. Specific tests can be referred to Diagrams as below,


MORNSUN AC/DC Converter Model Numbering

LS series are compact size, cost-effective converters with universal input voltage range of 85-305VAC in single-in-line package (SIP) .

LDE series are compact size with universal input voltage range of 85-264VAC in dual-in-line package (DIP) .

LHE series are have a variety of options of multiple I/O voltage with universal input voltage range of 85-264VAC in a standard dual-in-line package (DIP) .

LO series are open frame package converters with  optional input voltage range of 32-528VAC.

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