How do I start selecting a COSEL supply?

Add the load of every rail on the supply, add margin for the start-up and the lifetime, then choose the voltage class, the cooling and the mechanical form. Those decisions narrow the selection quickly.

What power do I need?

Add the load of every rail, add margin for the start-up and the lifetime, and choose the next standard wattage up. The COSEL PBA series spans 50 W to 600 W and beyond, so most designs have a fit. Our FAE team can help size the supply.

Convection or forced air?

A convection supply suits a sealed or a quiet enclosure and has no fan to wear out, and a fan-cooled supply suits a higher load where the airflow can be provided. Choose by the power and the enclosure, and confirm the derating at the highest ambient. Read the power design notes for the details.

Are the supplies genuine and documented?

Every COSEL supply BeiLuo ships is factory-traceable and includes an import declaration, a certificate of origin and a RoHS compliance file. Mainstream models are held in regional warehouses. Click a model for stock status, or request a quote for current lead time.

How do I start selecting a DC-DC converter?

Fix the input bus and the output voltage, size the power with margin, then confirm the isolation, the package and the temperature range. Those decisions narrow the selection quickly.

When do I need an isolated converter?

Use an isolated converter to break a ground loop, to protect a board from the bus or to meet an isolation requirement in a telecom or an industrial design. It also lets each board derive its own rail from a shared bus. Our FAE team can help choose the converter.

How do I plan the input filtering?

A DC-DC converter reflects a ripple current onto the input, so keep the input capacitor close and add the recommended filter for the conducted emissions. Follow the datasheet application circuit and keep the switching loop small. Our FAE team can review the layout.

Are the converters genuine and documented?

Every COSEL converter BeiLuo ships is factory-traceable and includes an import declaration, a certificate of origin and a RoHS compliance file. Mainstream models are held in regional warehouses. Click a model for stock status, or request a quote for current lead time.

How do I start selecting an EMI filter?

Choose the current above the load, the AC or DC voltage rating from the line, the phase and the stage, then pick the capacitor code for the leakage you can allow. Those decisions narrow the selection quickly.

Why does the capacitor code matter?

The line-to-ground capacitor code sets the leakage current and the attenuation. A smaller capacitor lowers the leakage, which a medical or a sensitive application needs, but it also lowers the attenuation at high frequency, so the code is a trade between the leakage and the filtering. Our FAE team can help choose the code.

Where do I mount the filter?

Mount the filter close to the input connector, keep the input and output wiring separated and bond the case to the chassis, because a filter is only as good as its grounding. A poor placement lets the noise bypass the filter. Our FAE team can review the placement.

Are the filters genuine and documented?

Every COSEL filter BeiLuo ships is factory-traceable and includes an import declaration, a certificate of origin and a RoHS compliance file. Mainstream models are held in regional warehouses. Click a model for stock status, or request a quote for current lead time.

Why is derating important?

A power supply delivers less than its full rating at a higher ambient, so the derating curve sets the real available power. Keep thermal margin so the supply runs cool, which lengthens its life and lowers the failure rate. Read the notes for the derating rules.

How do I handle holdup and inrush?

Check the holdup time against the load and the mains, so the equipment rides through a brief dip, and confirm the inrush against the breaker. Add a suitable fuse and a surge protector at the input where the line is noisy. Our FAE team can help with the front end.

How do I meet the EMC and safety limits?

Add a COSEL EMI filter at the input, choose the capacitor code for the leakage the standard allows and bond the case to the chassis. Confirm the emissions and the leakage on the bench with the real load. Our FAE team can review the EMC design.

Are the parts genuine and documented?

Every COSEL part BeiLuo ships is factory-traceable and includes an import declaration, a certificate of origin and a RoHS compliance file. Mainstream models are held in regional warehouses. Click a model for stock status, or request a quote for current lead time.

What is the standout feature of the COSEL range?

The standout feature is the depth and the proven reliability of the power range: the PBA AC-DC supplies, the CBS and ZUS DC-DC converters and the NAC and EAC EMI filters, so a designer can source the whole power chain from one supplier that has built supplies for decades. The main design care points are the derating and the EMC.

How do the AC-DC supplies perform?

In practice the COSEL PBA supplies give a stable output across the load, a universal input and a good efficiency, and they derate as the datasheet shows when the ambient rises. On the bench the ripple and the regulation held across the range. Confirm the derating and the cooling.

How do the converters and filters perform?

The CBS and ZUS DC-DC converters give a clean isolated rail across the range, and the NAC and EAC EMI filters attenuate the conducted noise from 150 kHz and up when they are installed close to the connector with a good ground. Our FAE team can review the EMC design.

Can I get samples to evaluate?

Yes. We provide samples of the COSEL supplies, converters and filters for your own efficiency, thermal and EMC testing, with documentation included and FAE support during bring-up. Request a sample and we will confirm stock and lead time.

Technical Support | COSEL Expertise | BeiLuo

Guides, application notes and reviews from BeiLuo's FAE team covering COSEL AC-DC power supplies, DC-DC converters and EMI filters in detail and more.

Guides 3 Application Notes 1 Troubleshooting 0 Reviews 1

How to Select a COSEL AC-DC Power Supply

2026-07-26 - Guides - By Liu Wei Ming

Compare COSEL AC-DC power supplies by output power, voltage, cooling, input range and package for industrial, medical and telecom designs and systems.

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How to Select a COSEL DC-DC Converter

2026-07-21 - Guides - By Chen Hao

A practical method for selecting COSEL DC-DC converters by power, input and output voltage, isolation and package for industrial designs and systems today.

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How to Select a COSEL EMI Filter

2026-07-16 - Guides - By Chen Hao

Choose a COSEL EMI filter by current, voltage, phase, stage and attenuation for a clean industrial, medical or telecom power input and more designs today.

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COSEL Power Supply Design Notes

2026-07-09 - Application Notes - By Wang Jian

Power supply design notes for COSEL units: derating, thermal, active PFC, holdup, medical and telecom safety and EMC filtering in a real power system.

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COSEL Power Supply and Filter Review

2026-06-30 - Reviews - By Liu Wei Ming

A hands-on review of COSEL AC-DC supplies, DC-DC converters and EMI filters for industrial and medical designs, covering reliability and EMC and more.

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Meet Our FAE Team

Liu Wei Ming

Senior FAE Engineer, Power

AC-DC SuppliesThermalPower Design

Author profile

Chen Hao

FAE Engineer, DC-DC and Filters

DC-DC ConvertersEMI FiltersEMC

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Wang Jian

FAE Engineer, Power Applications

Power SystemsDeratingReliability

Author profile