AC vs. DC Switch: Which One to Choose?

Network switches, like most electronic devices, require power to operate. When it comes to switches powered by different power systems, there are two primary types in the market: AC (alternating current) switches and DC (direct current) switches. Understanding the differences between these two options is crucial for selecting the right switch for your specific needs. In this article, we will explore the disparities between AC and DC switches and provide insights on how to make an informed choice.

AC Switch vs. DC Switch: What Are They?

What is an AC Switch?

AC-powered network switches are designed to operate using Alternating Current (AC) electricity, which is the standard form of power supplied to homes and businesses through wall outlets. Most AC switches are designed to be compatible with global power grids and support 100V–240V AC. AC switches required in industrial environments usually support a wider voltage fluctuation range, such as 85V–264V AC, to cope with unstable power grids.

These switches typically have an internal power supply that converts the incoming AC voltage to the DC voltage required for the internal electronics of the switch. Many common network switches, especially those for home or office use, fall into this category and often come with a standard power cord to plug into an AC outlet. Take S5850-24S2C as an example. It supports dual hot-swappable AC power supplies.

What is a DC Switch?

DC-powered network switches are purpose-built for deployment in environments that demand high availability, continuous operation, and telecoom-grade power infrastructure. Powered by a -48V DC input (typically within a -36V to -72V range), these switches are ideal for telecom central offices, data centers, transportation hubs, power utilities, and other critical network scenarios. With robust hardware design, support for dual redundant DC power inputs, and wide-voltage tolerance, DC-powered switches ensure uninterrupted network connectivity even in the event of AC power failures or fluctuations. Take S5800-48T4S-DC as an example. It supports dual hot-swappable DC power supplies.

AC vs. DC Switch: What Are the Differences?

One of the key differences between AC and DC powered switches lies in the nature of the power they control. AC switches are designed to handle the alternating nature of the current, while DC switches are optimized for the steady flow of direct current. Additionally, AC switches need to be able to interrupt the current flow during both positive and negative half-cycles, which adds complexity to their design.

Another significant difference is the presence of an arc during the switching process. AC power switches experience natural zero-crossings during the AC wave, which help extinguish arcs when interrupting the current flow. In contrast, DC switches have no zero-crossings, making it more challenging to extinguish arcs. Therefore, DC power switches often require additional measures, such as magnetic blowouts or arc chutes, to suppress arcs effectively.

Furthermore, the electrical components used in AC and DC switches differ due to the unique requirements of each system. AC switches typically employ electromechanical contacts, such as relays or contactors, to handle the high voltage and current levels associated with AC power. DC switches, on the other hand, commonly use solid-state components like transistors or thyristors, which can efficiently control the flow of direct current.

AC vs. DC Switch: How to Choose?

In essence, the choice depends largely on your power infrastructure, reliability needs, and energy efficiency goals.

For most enterprise, home, or general data center use without existing DC infrastructure, AC powered switches are more practical due to the ubiquity of AC power, easier deployment, and standardized equipment. However, they involve more conversion steps and slightly lower efficiency.

If your environment already has a DC power plant (common in telecom or some data centers), or if you prioritize maximum uptime and energy efficiency, DC powered network switches are preferable. They reduce conversion losses, improve reliability by running directly off batteries, and are standard in telco-grade equipment.

Consideration

AC Powered Switches

DC Powered Switches

Typical Use Case	General enterprise, homes, data centers without DC infrastructure	Telecom, telco-grade data centers, environments requiring high uptime and battery backup
Power Infrastructure	Standardized AC power outlets and UPS systems	Requires DC power distribution, rectifiers, and battery banks
Energy Efficiency	Lower efficiency due to multiple AC/DC conversions	Higher efficiency, fewer conversions, less heat
Reliability	Dependent on UPS transfer switching	Runs directly off batteries, no transfer delay, higher reliability
Installation Complexity	Easier, plug-and-play with standard power cords	More complex, requires DC fuse panels and specialized wiring
Cost Considerations	Lower initial setup cost	Potentially higher initial cost, but savings over time in energy and maintenance

Then if you choose the wrong type of switch, what should you do? To use AC switch in the DC location, a power inverter (changes DC to AC) should be added. DC switches can also convert AC power to DC power by using a rectifier. That is to say, when you choose the wrong DC/AC power switch, you may have to buy another network device(power inverter or rectifier) as a remedy. Or you can choose a switch that can operate on both AC and DC power supplies.

FS AC/DC Switches Recommendations

To simplify the selection process, FS offers various switches that support AC and DC power. These switches provide the flexibility to handle different power sources, making them versatile solutions for various applications. Here is a table showcasing the specifics of some FS switch models that support both AC and DC power.

Note: This table is constantly updated.

Switch Model

Ports

Switching Capacity

Forwarding Rate

Power Supply

Fan

S5500-48F6S	48x 1G SFP | 6x 1G/10G SFP+	216 Gbps	162 Mpps	2 (1+1 Redundancy) Hot-swappable, DC	3 Built-in
S5500-48T6S	48x 10/100/1000BASE-T RJ45 | 6x 1G/10G SFP+	216 Gbps	162 Mpps	2 (1+1 Redundancy) Hot-swappable, AC	2 Built-in
S5800-48T4S	48x 10/100/1000BASE-T RJ45 | 4x 1G/10G SFP+	176 Gbps	132 Mpps	2 (1+1 Redundancy) Hot-swappable, AC	3 Built-in
S5800-48F4SR	48x 1G SFP | 4x 10G SFP+	176 Gbps	132 Mpps	2 (1+1 Redundancy) Hot-swappable, AC	3 Built-in
S5850-24S2C	24x 1/10G SFP+ | 2x 40/100G QSFP28	880 Gbps	540Mpps	2 (1+1 Redundancy) Hot-swappable, AC	3 Built-in
S5850-24S2Q	24x 1G/10G SFP+ | 2x 40G QSFP+	640 Gbps	480 Mpps	2 (1+1 Redundancy) Hot-swappable, AC	3 Built-in
S5850-48S8C-DC	48x 10Gb SFP+ | 8x 40G/100G QSFP28	2.56Tbps	1905Mpps	2 (1+1 Redundancy) Hot-swappable, DC	4 Built-in

Final Thought

In conclusion, the choice between an AC or DC powered network switch depends on the specific power infrastructure available, the environment of deployment, and the overall system design requirements. By understanding the differences and considering the factors discussed in this article, you can make an informed decision and select the most suitable switch for your needs. Whether it's an AC switch or a DC switch, FS has you covered with reliable and versatile options to ensure efficient power control and distribution in your network.