一种保护电路，用于一功率转换器。保护电路包括一传感器电路、一侦测电路以及一初始保护电路。传感器电路传感功率转换器的一输出电流以产生一负载信号。侦测电路侦测在一端口的一信号端上的一电压信号。初始保护电路接收负载信号，且比较负载信号与一初始保护临界值。当在保护电路被致能之后，信号端上的电压信号由一低准位切换为一高准位时，功率转换器进入一初始保护模式，且初始保护电路计数一端口认证进程的一初始期间。当在端口认证进程的初始期间中，负载信号大于初始保护临界值时，初始保护电路将产生一第一保护信号以关闭功率转换器。

A protection circuit for a power converter is provided. The protection circuit comprises a sensor circuit, a detection circuit, an initial protection circuit. The sensor circuit senses an output current of the power converter to generate a load signal. The detection circuit detects a voltage signal at a signal terminal of the connection port. The initial protection circuit receives the load signal and compares the load signal with an initial-protection threshold. When the voltage signal at the signal terminal switches to a high level from a low level after the protection circuit is enabled, the power converter enters an initial protection mode and the initial protection circuit counts an initial period of a port-identification procedure. When the load signal is larger than the initial-protection threshold during the initial period of the port-identification procedure, the initial protection circuit will generate a first protection signal to shut down the power converter.