Windows users occasionally encounter the frustrating ERROR_INSUFFICIENT_POWER (639 or 0x27F in hexadecimal) when connecting USB devices or peripherals. This error indicates your system cannot provide adequate power to the connected device, potentially disrupting workflows and limiting device functionality.

Understanding ERROR_INSUFFICIENT_POWER

The error code 0x27F typically appears when:
- Connecting power-hungry USB devices
- Using USB hubs without external power
- Experiencing driver conflicts
- Having faulty USB ports or cables
- Running on insufficient system power supply

Windows generates this error as a protective measure to prevent damage to both the device and your computer's USB controllers.

Primary Causes of Error 0x27F

  1. Inadequate USB Port Power
    - Standard USB 2.0 ports provide 500mA (2.5W)
    - USB 3.0/3.1 ports offer 900mA (4.5W)
    - Some devices require up to 1.5A (7.5W)

  2. Faulty or Underpowered USB Hubs
    - Unpowered hubs split available power
    - Daisy-chaining multiple hubs compounds the issue

  3. Driver Conflicts
    - Outdated or corrupt USB drivers
    - Incorrect power management settings

  4. System Power Supply Issues
    - Overloaded PSU
    - Failing power supply unit

Step-by-Step Troubleshooting Guide

1. Basic Checks

  • Try different USB ports (preferably USB 3.0+)
  • Connect the device directly to the computer
  • Test with a different cable
  • Try the device on another computer

2. Use Powered USB Hubs

For multiple devices or power-hungry peripherals:
- Purchase a hub with external power adapter
- Look for hubs with at least 2A total power output
- Avoid daisy-chaining multiple hubs

3. Update USB Drivers

  1. Press Win+X and select Device Manager
  2. Expand Universal Serial Bus controllers
  3. Right-click each USB Root Hub and select Update driver
  4. Choose "Search automatically for updated driver software"
  5. Repeat for all USB controllers

4. Modify Power Management Settings

  1. In Device Manager, right-click USB Root Hub
  2. Select Properties > Power Management
  3. Uncheck "Allow the computer to turn off this device to save power"
  4. Click OK and restart your computer

5. Disable USB Selective Suspend

  1. Open Control Panel > Power Options
  2. Click "Change plan settings" for your active plan
  3. Select "Change advanced power settings"
  4. Expand USB settings > USB selective suspend setting
  5. Set to Disabled
  6. Click Apply and OK

6. Check BIOS/UEFI Settings

  1. Restart your computer and enter BIOS/UEFI (typically F2, F12, or DEL)
  2. Look for USB configuration options
  3. Ensure:
    - USB legacy support is enabled
    - USB power delivery is set to maximum
    - XHCI hand-off is enabled for USB 3.0
  4. Save changes and exit

7. Test with a Different Power Supply

If you're using a desktop:
- Try a higher wattage PSU
- Ensure all power connectors are properly seated
For laptops:
- Try using the AC adapter instead of battery
- Check for battery health issues

Advanced Solutions

Modify Registry Settings (Advanced Users)

  1. Press Win+R, type regedit, and press Enter
  2. Navigate to:
    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\USB
  3. Right-click > New > DWORD (32-bit) Value
  4. Name it "DisableSelectiveSuspend"
  5. Double-click and set Value data to 1
  6. Restart your computer

Reinstall USB Controllers

  1. In Device Manager, right-click each USB controller
  2. Select Uninstall device
  3. Restart your computer to automatically reinstall drivers

When to Seek Professional Help

Consider professional assistance if:
- The error persists across multiple computers
- You experience frequent USB disconnections
- Your computer shows other power-related symptoms
- You suspect motherboard USB controller failure

Preventive Measures

  • Always use powered hubs for multiple devices
  • Regularly update your system and drivers
  • Avoid using excessively long USB cables
  • Periodically clean USB ports from dust
  • Consider PCIe USB expansion cards for additional power

By methodically working through these solutions, most users can resolve the ERROR_INSUFFICIENT_POWER issue and restore full functionality to their USB devices.