Railway Dc-Dc Converters


Welcome to the CUI Railway Dc-Dc Converter product spotlight. This presentation will provide an overview of CUI's railway dc-dc converters, including a summary of product highlights, features, and the requirements of the EN 50155 railway standard.


  • Highlight CUI's railway dc-dc converters through a description of key features and specifications.
  • Summarize the EN 50155 standards for railway equipment.
  • Describe typical applications for the railway dc-dc converters.


CUI's railway dc-dc converters have been designed to meet the specific needs of railway applications. These dc-dc converters provide high power density and efficiency thanks to the use of synchronous rectifiers as opposed to conventional Schottky diodes, making them ideal for applications where board space and energy consumption are concerns. Featuring an ultra wide input voltage range as wide as 43 ~ 160 Vdc, and an operating temperature range up to -40°C ~ 100°C, these high efficiency converters provide precisely regulated output voltages, making them ideal for applications with an unstable line voltage that may experience significant transients or voltage surges.

Product Highlights

  • High power density for compact applications
  • Ultra wide input voltage range as wide as 43 ~ 160 Vdc
  • Wide operating temperature range of -40 ~ 100°C
  • Highly suited for applications with an unstable line voltage


CUI's railway dc-dc converters are housed in a ruggedized package, providing added protection from environmental factors such as dust, moisture, and shock and vibration.  Protections include over voltage, over current, short circuit, under voltage lockout and over temperature. Additionally, all models offer remote on/off control, remote sense, output trim and carry UL/cUL 60950-1 and CE safety certifications.

European Standard EN 50155

  • Modern railway systems achieve efficiency by using a nominal battery voltage of 100 Vdc. However, most electronic equipment runs on 5 Vdc, 12 Vdc, and 24 Vdc. CUI's railway dc-dc converters address this issue by converting the nominal 110 Vdc.
  • To satisfy the stringent EN 61373 shock and vibration standard, the railway bricks have been specially designed with high shock and vibration tolerances.
  • EN 50155 defines the relative humidity standard; the power module should be able to withstand 75% average yearly relative humidity and 30 consecutive days with 95% relative humidity in a given year.
  • Electromagnetic compatibility (EMC) is another main category of the EN50155 standard. It states that the power module should be protected so that it is not negatively affected by conducted or radiated interference. This is referred to as EN 50121-3-2 and should not emit radio frequency interference (RFI) in excess of the defined levels.

EN 50155 Standard Continued

EN 50155 defines several standards for electrical service conditions in an effort to overcome the severity of railway applications and to provide stable service. These standards include input voltage range, input voltage ripple, and input surges.

Input Voltage Requirements (Nominal Input) Permanent Input Voltage Range Brownout 100 ms (0.6 x Vnom) Transient 1s (1.4 x Vnom)
24VDC 16.8-30.0V 14.4V 33.6V
37.5VDC 26.2-47.0V 22.5V 52.5V
48VDC 33.6-60.0V 28.8V 67.2V
72VDC 50.4-90.0V 43.2V 100.8V
96VDC 67.2-120.0V 57.6V 134.4V
110VDC 77.0-137.5V 66.0V 154.0V

CUI's railway bricks have been designed to handle input transients between 43 Vdc ~ 160 Vdc.

Isolation Voltage Summary

Railway converters are galvanically isolated from the input voltage to protect sensitive load circuits from noise and high voltage. CUI's dc-dc modules provides 2250 Vdc of isolation from input to output and input to case.

Condition Isolation
Input/Output 2250 Vdc
Input/Case 2250 Vdc
Output/Case 1500 Vdc

Parameter Value
Isolation Resistance 10M ohm
Isolation Capacitance 1000 pF


CUI's railway dc-dc converters are perfectly suited for a wide range of railway and non-railway applications.

Railway electronics applications:

LED displays, cabin lighting , computer systems, drive systems, control systems.

Non-Railway electronics applications:

Designs that experience high transients including telecom systems and battery-powered equipment.

Product Benefits

CUI's railway dc-dc converters offer a list of benefits over the competition.

  • Ruggedized package
  • Protections: OTP, OVP, OCP, Short CKT and UVLO
  • Remote on/off control
  • Remote sense
  • Output trim
  • UL/cUL 60950-1 and CE certified

Available Products

The converters are available in three different industry standard packages; the 20 W PRF20 is housed in a 2 x 1 package providing efficiencies up to 90%, the 100 W VQB100R is housed in a quarter brick package providing efficiencies up to 92% while the 150 W VHB150R is housed in a half brick package offering 92.5% efficiency.

Series Power (W) Output Voltage (Vdc) Size (in) Standard Package Efficiency
PRF20 20 5, 12, 15, +/-12, +/-15 2.00 x 1.00 x 0.40 2 x 1 90%
VQB100R 100 5, 12, 24 2.28 x 1.45 x 0.5 1/4 Brick 92%
VHB150R 150 5, 12, 24 2.28 x 2.4 x 0.5 1/2 Brick 92.5%


CUI's compact, PRF20, VQB100R and VHB150R dc-dc converters have been developed for railway applications. The modules comply with the EN 50155 standard, which specifies input, EMC, mechanical, and environmental requirements. The internally potted and encapsulated design provides increased system reliability through added protection from environmental factors such as dust, moisture, and shock and vibration.

North America/Global