MINMAX’s MIZI03 3W DC-DC Converters and a Look at Standards for Railway Applications

MINMAX has recently introduced the MIZI03 series of converters for railway applications. What requirements and challenges do railway applications face?

Railway applications are unique in many ways when it comes to electronic components. Railway electronic component regulatory standards are stringent, in part because railway applications are so rugged and have so many safety concerns associated with them.

In this News Brief, we'll talk briefly about the new MINMAX MIZI03 series of converters and take a high-level look at the requirements for components in railway applications.

A Look at Railway Standards for Electronics

As with all industries, there are multiple bodies developing standards. There are many standards that dictate component requirements for railway applications, depending on which part of the world you may be in. For example, EU-focused standards are indicated by an "EN" at the beginning of the standard name (e.g., EN 45545-2). IEC standards (e.g., IEC 60068) are developed by the International Electrotechnical Commission and intended for international use.

Sometimes these standards overlap as the IEC coordinates with various national standards. To this end, EN standards numbered 50000 to 59999 are intended to be purely for EU use while EN or IEC standards numbered 60000 to 69999 are intended to be shared between the two standards (with or without changes).
According to the IEC website, the TC 9 and ISO/TC 269 committees seek to standardize the railway field, which includes "rolling stock, fixed installations, management systems for railway operation, and their interfaces and ecological environment."
The MIZI03 series product sheet mentions several standards and certifications. Each one indicates, from a broad perspective, an aspect of safety and reliability related to railway applications.

• EN 45545-2: An EU standard related to fire testing for railway components.
• EN 50121-3-2: An EU standard specific to railway emission and immunity for EMC. It deals with the frequency range from DC to 400 GHz.
• EN 50155 (IEC 60571): Input voltage range and brief variation requirements. According to a breakdown of the standard, "EN50155 and IEC60571 specify a nominal input variation of ±30% including ripple but some other specifications define ±40%."
• EN 55032/11 Class A & FCC Level A: An EU standard addressing EMC emission levels, primarily as they relate to multimedia applications. The "A" refers to the fact that the railway application does not deal with residential applications. (It is identical to CISPR 32.)
• IEC/EN 60068-2: The IEC 60068 standard regards the environmental testing of "electrotechnical products". The "-2" refers to the portion of the standard that describes testing requirements under which components must be able to function or at least be stored. In the case of the MIZI03 series, the converters comply with the following tests for cold, dry heat, and damp heat tests.
  • IEC/EN 60068-2-1: Cold conditions 
  • IEC 60068-2-2: Dry heat conditions
  • IEC/EN 60068-2-30: Cyclic damp heat conditions
• EN 61373: An EU standard specifically for railway application vibration and thermal shock tests.
• UL/cUL/IEC/EN 62368 (60950-1): According to UL.com (a seller of access to standards), "This standard is applicable to mains-powered or battery-powered information technology equipment."

MIZI03 Power Converter Series

There are 15 members of the MIZI03 series, grouped into three input voltage ranges: 24 (9~36)VDC, 48 (18~75)VDC, or 72/110 (40~160) VDC. Within these groupings, there are output voltage availabilities for 5VDC, 12VDC, 15VDC, ±12VDC, and ±15VDC. Each option is offered in an encapsulated DIP-24 package.

Image from the MIZI03 datasheet (PDF).

Isolation and Insulation

The MIZI03 series touts I/O isolation 3000VAC with reinforced insulation. They are also vacuum-sealed with UL94V-0 grade sealants (which are important for reducing flammability). According to MINMAX, the combination of these two factors creates "a robust electrical barrier to secure sensitive circuit load from excess energy mishaps."

Energy Saving

There are two elements related to energy that MINMAX highlights with the MIZI03 series: quick start-up times and efficiency. In the product announcement, a 20ms start-up time is cited and credited with eliminating "timing failures" associated with long start-up times. A corresponding maximum start-up time is cited in the datasheet as 60ms.

Efficiency ratings from the datasheet are between 80% and 85% at maximum load, varying from model to model.

Other Relevant Features

• Voltage output trim
• Remote power control
• Circuit protections
  • Fire
  • Short-circuiting
  • Overvoltage
  • Overload
• No minimum load requirement
• Operating ambient temperature range: -40℃ to +92℃

Do you work with railway applications? Have you tried the MIZI03 series? Please share your experiences with either in the comments below.