Safety Information: How does USB (Type-C) PD3.1 output exceeding LPS/PS2 comply with IEC 62368-1 requirements?

The USB Type-C interface has been widely adopted across various electronic devices, including smartphones, tablets, computers, and monitors. The Type-C interface delivers excellent performance in data transfer, display output, and fast charging. In terms of fast charging, with the continuous updates to USB PD, the new USB PD3.1 fast charging standard supports a maximum voltage output of 48V, with charging power increasing to 240W.

When USB PD protocol transitioned from version 3.0 to USB PD 3.1, shifting from SPR (100W) @ 20V max to EPR (240W) @ 48V max, the safety requirements for USB output also changed. Previously, USB outputs were required to comply with LPS/PS2 power limits (<100W). However, in EPR mode, the power supply can normally exceed 100W. As a result, starting from USB PD 3.1, USB can no longer be regarded as a guaranteed "limited power source." This means that powered devices (PD) connected downstream must be designed with fire-resistant enclosures (unless they are limited to operating in SPR mode). This change is due to the fact that the power-supplying equipment (PSE) in EPR mode operates as a dynamically varying voltage source, no longer constrained to below 100W.

This technological evolution introduces certain contradictions and challenges to fire safety requirements. To address these issues, the IECEE Safety Technical Committee (IEC/TC 108) issued a new resolution, 108/832/INF, aimed at providing rapid solutions to mitigate the risk of fire in EPR mode. Industry experts conducted an analysis of the USB PD protocol against a functional safety communication standard (IEC 61784-3). This evaluation included the following eight common communication errors / failure modes:

1. Message corruption

2. Unintended repetition of a message

3. Incorrect message sequence

4. Message loss

5. Unacceptable delay of message

6. Message insertion

7. Message masquerade

8. Incorrect address

This primarily focuses on evaluating the communication protocol complying with a functional safety and validation test, ensures the provision of EPR power and the handling of EPR receivers when operating in EPR mode, while also implementing adequate protective measures to prevent faults and mitigate fire risks. Furthermore, it ensures that in non-EPR mode, the power transmission between the power supply and receiver is maintained below 100W.

 Power Source vs Powered Device and need for Powered Device fire enclosure:

Regarding the recent popular requirements related to USB Type-C, this article mentions the IECEE (TC 108/832/INF) Functional Safety and the upcoming EU Common Charger Directive, which will be mandatory. 

BTL currently utilizes the latest USB-IF Association-approved testing equipment (GRL-USB-PD-C2-EPR). This enables BTL to provide comprehensive testing services to a wide range of manufacturers and issue recognized certification reports, offering customers a faster, and one-stop solution platform.