In industrial automation, a stable DC power supply is crucial for PLCs, HMIs, relays, and other control devices. Switched Mode Power Supplies (SMPS) provide reliable DC voltage, ensuring consistent operation of all low-power components inside control and instrumentation panels.

What is an SMPS and Why It’s Used

An SMPS converts AC mains voltage (110–230V) into regulated DC output, typically 24V for control panel applications. While 5V is occasionally used for small devices, 24V DC is the industry standard.

Moreover, advanced SMPS units include adjustable output voltage, usually within 21–27V DC. This flexibility allows engineers to fine-tune the voltage for specific devices, optimizing performance and reliability. Selecting an SMPS requires considering the total DC load, which can range from 5A to 30A depending on panel requirements.

Author Insight: Using a well-sized SMPS improves panel reliability and reduces stress on sensitive PLC and instrumentation components.

Features of Modern SMPS

Modern SMPS units often include relay contacts that signal if the output voltage deviates from the desired range. PLCs can use these signals as digital inputs for automatic alerts or system shutdowns, enhancing control system safety and fault monitoring.

How Redundant SMPS Works

Redundant power supplies provide uninterrupted DC output by using two SMPS units—one primary and one standby. Both receive the AC input, but their outputs are slightly offset (e.g., 24V primary vs. 23.5V standby).

Diodes at each output ensure only the higher voltage supply feeds the load. If the primary supply fails, the standby SMPS automatically takes over. When the primary recovers, it resumes supplying power.

This redundancy prevents panel downtime and maintains continuous operation, which is critical in industrial automation and factory automation systems.

Types of Redundant SMPS Configurations

1. Integrated Redundant Units: Both SMPS modules are built into a single package with pre-configured diodes.

2. Separate SMPS with Diode Modules: Two individual SMPS units connected via an external diode module achieve redundancy.

Both methods ensure seamless transition between primary and backup power, avoiding interruption to PLCs, HMIs, and other control devices.

Industry Perspective: Redundant SMPS is essential in critical control applications, such as DCS systems in power plants, manufacturing lines, and industrial automation setups where uptime is non-negotiable.

Choosing the Right SMPS for Your Control Panel

When selecting an SMPS, consider:

• Total current rating of all DC devices in the panel.

• Adjustable output voltage range for flexibility.

• Optional relay contacts for system integration.

• Redundancy requirements for critical operations.

Author Insight: Investing in the right SMPS and redundancy setup improves equipment reliability, reduces maintenance costs, and ensures smooth factory automation processes.

Application Cases and Industrial Solutions

• PLC Panels in Manufacturing: SMPS ensures reliable 24V DC for PLCs and HMI interfaces.

• Process Automation in Power Plants: Redundant SMPS units prevent control system downtime.

• Instrumentation Panels in Industrial Plants: Adjustable voltage SMPS optimizes sensitive sensors and relays.