3V 1.5A AC-DC Power Supply - 2.1mm x 5.5mm Center Negative | SW-31GN

Part SW-31GN is a wall-mount, regulated switching power supply that converts 100–240V AC input to 3V DC at up to 1500mA (1.5A). Its 2.1mm x 5.5mm barrel plug has center-negative polarity for equipment specifically requiring this connection.

IMPORTANT: CENTER-NEGATIVE OUTPUT. NOT CENTER POSITIVE.
The barrel plug's inner contact is negative (−), and its outer sleeve is positive (+). Do not connect this supply to equipment requiring center-positive power. Matching the voltage and plug size alone is not enough; incorrect polarity can damage equipment.

Technical Specifications

• Part: SW-31GN
• Input: 100–240V AC
• Output: Regulated 3V DC
• Maximum Output Current: 1500mA (1.5A)
• Maximum Output Power: 4.5W
• Connector: 2.1mm inner diameter x 5.5mm outer diameter barrel plug
• Polarity: Center negative (−), outer sleeve positive (+)
• Power Supply Type: Regulated switching AC-DC
• Mounting Style: Wall-mount

Common Applications & Replacement Guidance

Use as a replacement supply for equipment whose manufacturer specifies 3V DC, center-negative polarity, a matching 2.1mm x 5.5mm power connection, and a current requirement of 1.5A or less. No specific device compatibility is claimed. Confirm the complete power requirements before ordering, including barrel insertion length and physical clearance.

Compatibility Checklist

• Voltage and output type: Your device must require 3V DC, not AC output or a different DC voltage.
• Current: Your device must require no more than 1500mA (1.5A).
• Polarity: Your device must require center negative (−), with the outer sleeve positive (+).
• Connector fit: Confirm 2.1mm ID x 5.5mm OD, insertion length, and clearance.
• Input connection: Confirm the wall plug fits your outlet and the supply voltage is within 100–240V AC.

Frequently Asked Questions

Is this center negative or center positive?
Center negative. The inner barrel contact is negative (−), and the outer sleeve is positive (+). It is not a center-positive supply.

Can I use this with a center-positive device?
No. Do not connect this supply directly to a device requiring center-positive polarity, even if the voltage and connector dimensions match.

What are the output voltage and current?
The regulated output is 3V DC, with a maximum current capacity of 1500mA (1.5A), equivalent to 4.5W.

Can it power a device that uses less than 1500mA?
A lower current requirement can be suitable, provided the manufacturer permits a regulated 3V DC supply and the polarity, connector dimensions, and physical fit all match. The device draws the current it needs.

Does a matching barrel plug guarantee compatibility?
No. Check the required voltage, DC output type, current, center-negative polarity, and complete connector fit against the device documentation.

Is this a 3V AC transformer?
No. This is a regulated switching supply with 3V DC output. The 100–240V AC specification describes its input, not its output.

Can I use it as a replacement for a battery-powered device?
Only if the device manufacturer supports external 3V DC power through the matching center-negative connection. Battery voltage alone does not establish adapter compatibility.