How does a tiny adapter manage to output video and charge your Switch at the same time? The answer lies in two key USB-C technologies.
USB-C Alternate Mode
USB-C connectors contain 24 pins. While some pins handle standard USB data and power, others can be repurposed for alternate functions. The Switch uses “DisplayPort Alt Mode” or “HDMI Alt Mode” to send video signals through the USB-C port.
When you connect a compact HDMI adapter, the Switch detects the alternate mode negotiation and reroutes video signals from the GPU to the USB-C pins instead of the internal display.
How the Adapter Processes Video
Inside the compact adapter, a dedicated chip performs two tasks:
- Protocol conversion: Converts the DisplayPort or raw video signal from the Switch into HDMI-compliant signals
- Signal amplification: Boosts the signal strength so it can travel through an HDMI cable without degradation
The quality of this conversion chip directly affects output stability. Cheap chips introduce noise, causing flickering or signal dropout.
USB Power Delivery (PD)
TV mode requires more power than the Switch’s battery can provide alone. USB PD allows the adapter to pass through power from an external charger to the Switch while simultaneously processing the video signal.
The Switch requests 15V at 2.6A (39W) from the charger in TV mode. If the charger cannot supply this, the Switch may fail to enter TV mode or may run the battery down even while “charging.”
Why Heat Is Generated
Signal conversion and voltage regulation are not 100% efficient. The lost energy becomes heat. Metal-bodied adapters act as heat sinks, dissipating this heat into the air. Plastic-bodied adapters insulate the heat, causing temperatures to rise and potentially affecting performance.
Summary
Compact HDMI adapters work by leveraging USB-C Alt Mode for video output and USB PD for power delivery. The quality of the internal conversion chip and heat management design determines real-world performance. Understanding this helps you make an informed choice when buying.