MEAN WELL: Redundant power supply for maximum system reliability

Frank Stocker
Field Application Engineer (FAE) Power Supplies

27.11.2025

Figure 1: Image of the DRS-480 all-in-one DC UPS (left) and the UHP-500R 500-watt power supply with integrated redundancy function (right) (source: MEAN WELL)

Why are redundant power supplies indispensable?

Whether in automation, IT infrastructure or industrial production, the reliability of the power supply is a key factor for operational safety. If a busbar fails, the supply to consumers in critical applications must still be guaranteed. Redundant systems – such as those in 1+1 or n+1 operation – enable the remaining devices to take over the entire load in the event of a power supply failure. This keeps plant operation stable and avoids costly downtime. This requires coordinated dimensioning that takes into account both power reserves and the decoupling of the supply rails.

How do classic and modern redundancy concepts work?

The classic design of a redundant power supply consists of two power supply units connected in parallel, whose outputs are decoupled by block diodes. These diodes prevent current from flowing back into the other power supply unit in the event of a defect or short circuit in one power supply unit. This ensures that the consumer continues to be supplied with power. (Figure 2)

Figure 2: 500-watt 1+1 redundant power supply – top: conventional design with block diodes, bottom: design with two MEAN WELL UHP-500R power supplies with integrated MOSFET for decoupling (source: MEAN WELL)

However, this solution also has disadvantages: diodes generate a voltage drop in forward operation, which leads to additional power loss and heat generation. Accordingly, they should be oversized for relief and often equipped with heat sinks. This not only increases energy consumption, but also the space requirements and complexity of the installation. With increasing output power, this concept quickly becomes impractical, especially in confined installation situations in the control cabinet or in systems with high packing density. MOSFET-based redundancy modules offer a more efficient solution. They replace the diodes with electronic switches with extremely low on-resistance (RDS(on)), which reduces the voltage drop during operation. The result is lower losses, less heat generation and a significantly more compact design.

What advantages do MEAN WELL redundancy modules offer?

The redundancy modules in the MEAN WELL DRDN20/40 and ERDN20/40 series were developed specifically for this purpose. They enable 1+1 or 1+N configurations, offering flexible application options – from small systems to complex installations with multiple power supplies connected in parallel.

Key features and advantages include:

• Efficient MOSFET decoupling: Minimal voltage drop and significantly lower power loss compared to classic diode circuits.
• Reduced heat generation: Less thermal load, in many cases no additional heat sink required.
• Compact design: Space-saving DIN rail modules, ideal for use in control cabinets or device installation.
• High flexibility:
  • Supports 1+1 and 1+N configurations for different power requirements.
  • System voltages: 5 V, 12 V, 24 V and 48 V.
  • Rated current: up to 40 A, peak current: up to 60 A (for max. 5 s).
• Integrated monitoring: Both DC strings are continuously monitored for failures or voltage deviations.
• Remote signalling contacts notify the central control system of faults such as overvoltage or undervoltage.
• Increased system availability: Faults can be detected and rectified at an early stage, minimising downtime.
• High reliability: Robust design for continuous industrial operation and applications with high safety requirements.
• Low-maintenance solution: The absence of mechanical components and heat sinks increases long-term operational reliability.

Are there alternatives to external redundancy modules, and if so, what are they?

For applications with limited installation space, power supplies with integrated redundancy functions, such as the UHP-R series from MEAN WELL, are a space-saving solution. The power supplies in this series (models UHP-200R, UHP-350R and UHP-500R) combine an AC/DC power supply with integrated MOSFET decoupling and a DC_OK signal output. This eliminates the need for external redundancy modules, simplifying the design and reducing space requirements. This series was developed for applications that require an uninterruptible power supply and decoupling between redundantly operated power supplies. Areas of application include automation and control technology systems, building technology, communications and testing technology, and industrial plants that place high demands on operational reliability and availability.

The UHP-R series features the following technical characteristics:

• Integrated MOSFET redundancy function: Decouples parallel-connected power supplies, prevents backfeeding and enables safe 1+1 or n+1 operation.
• DC_OK signal output: Signals voltage deviations or failures to the central control system.
• Input voltage range: 85–264 VAC, suitable for worldwide use.
• Efficiency: Up to over 94%, low power loss and reduced heat generation.
• Partial encapsulation and fanless design: Protection against dust, moisture and vibration, designed for low-maintenance operation.
• Temperature range: Operation up to +70 °C, power reduction from +50 °C.
• Power classes: Up to 500 W with standard output voltages from 3.3 V to 55 V.
• Compact design: Low height, suitable for applications with limited installation space.
• Certifications: EN 60335-1, EN 62368-1 and EN 61558-1/-2-16.

The integration of the decoupling function into the power supply reduces the need for external components, simplifies system design and increases overall efficiency.

How is the power supply secured in the event of power failures?

In addition to redundancy solutions, MEAN WELL offers further protection solutions for short-term or longer-term failures, e.g. in low-voltage networks. The all-in-one DC UPS systems (DRS-240/480) combine a power supply unit, charger and monitoring in a single device. They ensure an uninterrupted power supply during longer power failures.

Buffer modules such as the DBUF20 and DBUF40 stabilise voltage dips in the millisecond range. For example, the DBUF40 bridges 250 ms at 40 A load current, and several modules can be connected in parallel. These products ensure a reliable supply – from short voltage dips to complete power failures.

About us

As a power supply distributor we stock power supplies from various manufacturers such as MEAN WELL, Recom, Self Electronics and others. We keep around 8,000 different types of power supplies and DC/DC converters in stock in production-ready quantities at our automated central warehouse in Monheim am Rhein. As a reliable supplier we also offer fast and competent support, for example through direct contact persons and a field service for on-site problem solving. Our customers benefit from the rapid processing of their enquiries, the provision of data sheets and samples, and different delivery quantities from samples to series production.