Class 2 vs. Class II Power Supplies

Shopping for power supplies can be an overwhelming experience, with many specifications and factors to consider. For example, you must understand the difference between Class 2 and Class II power supplies to ensure your choice is compatible with the specific device or equipment you intend to use.

This guide explains Class 2 vs. Class II power supplies as electrical devices that safely power various electronic equipment. We also examine their unique safety features and give examples of when to use them.

Power Supply Safety Classes Explained 

Different organizations categorize power supplies based on their safety features and design considerations.

Class 1 and Class 2 power supplies comply with the National Electrical Code and refer to AC-DC products'  output voltage and power capabilities.

• Class 1: Class 1 supplies have a high voltage output but need a protective earth connection for safety within the fixture.
• Class 2: Class 2 supplies limit output to a safe level, preventing overheating or electric shock.

On the other hand, the International Electrotechnical Commission defines three safety classes for power supplies, referring to their internal construction and electrical insulation.

• Class I: These power supplies have insulation that prevents direct contact with live parts, plus a protective earth or ground connection.
• Class II: With double or reinforced insulation, Class II power supplies need no protective earth connection.
• Class III: Class III power supplies require no insulation, as the input voltage is very low.

Class 2 Power Supply 

A Class 2 power supply limits the amount of electrical current it can provide, making it safer for various electronic devices. 

What Is Class 2 Power Supply Used For?

Class 2 devices have distinctively identifiable certification labeling. Compared to Class 1 devices, the wiring methods for Class 2 power supplies are less stringent and often use smaller-gauge wires and connectors. They're safe for contact, which means no earth safety protection is necessary.

Class 2 devices have the following limitations to reduce the risk of electric shock and overheating.

• Maximum power capacity of 100VA
• Output is equal to or below 30V AC or 60V DC

Examples of applications for Class 2 power supplies include:

• LED lighting
• Small transformers
• Doorbells
• Small electronics
• Telecommunications equipment

Efficiency and Performance of Class 2 Power Supplies 

Some manufacturers provide efficiency ratings for their Class 2 products to help consumers understand how well the devices operate.

We can measure efficiency in Class 2 devices by calculating the ratio of output power to input power in watts, expressed as a percentage. 

• Efficiency (%) = (Output power / input power) x 100

Since Class 2 devices have limited output power, measuring efficiency helps evaluate how effectively the device converts input into output. A higher percentage indicates the device wastes less input power as heat or other forms of energy loss.

Class II Power Supply 

Thanks to its additional insulation, a Class II power supply provides electricity without needing a safety ground connection.

What Is Class II Power Supply Used For? 

Class II power supplies protect against electric shock with either two layers of insulation or one reinforced layer of insulation. The insulation eliminates the need for a ground connection — the product's casing grounds the power supply.

Many medical devices are Class II power supplies requiring higher power needs or specific safety considerations. You can recognize them by looking for the concentric square symbol on the label.

Design Considerations for Class II Power Supplies

Generally, a single level of insulation is acceptable, but only if the circuit is not accessible to the user. However, users with access to current-carrying components need an extra layer of protection from hazardous voltages. Class II devices consider the following factors.

• Efficiency: Manufacturers must balance power efficiency with safety measures when designing Class II components.
• Size and form: Users often favor compact devices, requiring manufacturers to plan the layout and place components carefully while building devices. Class II supplies often need larger creepage and clearance distances.
• Insulation materials: Non-conductive materials like plastic usually enclose equipment, but Class II devices may also have metal if there's insulation between the circuit and the user.

Class 2 vs. Class II — A Comparative Analysis

The difference between Class 2 and Class II power supplies is not about superiority. Either will decrease your risk of overheating equipment and electric shock. Instead, your choice will depend on your power needs and whether the device meets or exceeds your application's specifications.

Here's a further comparison between Class 2 and Class II to illustrate the difference.

• Safety level: While Class 2 relies on a ground connection for protection, Class II power supplies provide a higher level of safety with double or reinforced insulation.
• Compliance: Class 2 adheres to NEC specifications with defined power and voltage limits for safety. Class II power supplies follow IEC standards to meet specific insulation levels for enhanced safety.
• Efficiency: Efficiency varies between Class 2 devices, while balancing efficiency with safety measures is essential in Class II device designs to optimize power conversion.
• Design considerations: Class 2 products typically have simpler designs due to their basic insulation requirements. With Class II, design becomes more complicated due to the extra or reinforced insulation layers.
• Cost implications: Due to the design and insulation requirements, Class II devices may be more expensive than Class 2 power supplies.
• Applications: General electrical applications requiring essential protection usually use Class 2 power supplies. On the other hand, applications like medical and industrial devices that require advanced safety measures regularly use Class II power supplies.

Choose the Correct Power Supply Class With Astrodyne TDI

Class 2 and Class II power supplies differ based on their primary focus. Class 2 devices limit their power output to reduce safety hazards, while Class II products' double insulation eliminates their need for ground connection. Each adheres to specific safety, efficiency and reliability standards. Various industries may use these classifications differently, so be sure to double-check the regulations.

Astrodyne TDI can support your power supply needs, whether your application requires Class 2 or Class II devices. If you're unsure which one to pick or you need a custom solution, we have the advanced tools and technology to design and modify your power supplies to meet unique requirements.

Contact our team for help finding your ideal product.