Robust DC Surge Protectors for Demanding Applications

For applications that are frequently subjected to severe over-voltage transients, RECOM has developed a range of surge protection modules for PCB mounting. These modules are designed to be conformant to stringent standards such as RIA12, NF F 01-510, and EN50155 specifications for railway rolling stock, or to the MIL-STD-416G or MIL-STD-1275E surge protection defense standards. The RSP series of surge protectors are designed to be inserted before the EMI input filter stage so that both the filter components and the following DC/DC converters are effectively protected against high energy over-voltage surges and transients.

Railway and defense applications present uniquely challenging electrical environments. Equipment in these sectors is often exposed to significant voltage surges and transients originating from various sources, such as power line fluctuations, switching events, nearby lightning strikes, or in defense contexts, specific field conditions. Without robust overvoltage protection, sensitive electronic components, particularly DC/DC converters and their control circuitry, are at high risk of damage or premature failure. This is why adherence to stringent standards like EN50155 for railway surge protection and MIL-STD-1275E or MIL-STD-416G for defense surge protection is not just recommended, but often mandatory to ascertain operational integrity and longevity of the system.

The RSP series modules are available in 20W, 45W, 150W, 200W, or 300W continuous power ratings for either 110VDC or 24/28VDC nominal input voltages. The surge protector output tracks the supply voltage (pass-through) in the ranges of 40 to 165VDC or 9 to 36VDC, but then clamps the output voltage to 168VDC or 40VDC respectively, providing precise overvoltage limiting. The RSPxx-40M series additionally feature built-in inrush current limiting and an on/off control, while the RSPxxx-168 series can handle input voltage surges of up to 385VDC. These features make the RSP series a versatile solution for ensuring the reliability of power systems in harsh electrical environments.

Choosing the right DC surge protector involves more than matching voltage and power ratings. Engineers must also evaluate parameters such as:

• Clamping Voltage Precision: The protector must reliably clamp transient voltages to a level that is safely below the susceptibility threshold of downstream components, like DC/DC converters, yet above the normal operating voltage range.
• Energy Absorption Capability (Joules): The expected surge energy in the application dictates the required absorption rating of the surge protection module.
• Response Time: A faster response time offers better protection against rapid transient events.
• Compliance and Certification: Verification against relevant industry standards (e.g., RIA12, NF F 01-510 for railway, or specific MIL-STDs) provides confidence in the protector's performance and suitability.
• Physical Characteristics: Factors like PCB footprint, mounting style, and operating temperature range are crucial for seamless integration into the overall design. A thorough analysis of these factors, coupled with an understanding of how the surge protector integrates with other protective elements like EMI filters, ensures the chosen device effectively safeguards the application and contributes to overall system reliability when used with RECOM’s converters.