초록 ▼

Power over Ethernet (PoE) communication systems provide power and data communications over the same communications link, where a power source device (PSE) provides DC power (for example, 48 volts DC) to a powered device (PD). The DC power is transmitted simultaneously over the same communications me

Power over Ethernet (PoE) communication systems provide power and data communications over the same communications link, where a power source device (PSE) provides DC power (for example, 48 volts DC) to a powered device (PD). The DC power is transmitted simultaneously over the same communications medium with the high speed data from one node to the other node. The PSE typically includes a controller that controls the DC power provided to the PD at the second node of the communications link. The PSE controller measures the voltage, current, and temperature of the outgoing and incoming DC supply lines to characterize the power requirements of the PD. The PSE controller includes a resistorless switch to measure the current. The resistorless switch includes a sense transistor and a current mirror to allowing the PSE controller to calculate the current based upon a replica current.

대표청구항 ▼

What is claimed is: 1. An apparatus for sensing current, comprising:a main transistor configured to have a first drain to source voltage applied between its respective drain and its respective source and a first gate to source voltage applied between its respective gate and its respective source;a s

What is claimed is: 1. An apparatus for sensing current, comprising:a main transistor configured to have a first drain to source voltage applied between its respective drain and its respective source and a first gate to source voltage applied between its respective gate and its respective source;a sense transistor configured to have a second drain to source voltage applied between its respective drain and its respective source and a second gate to source voltage applied between its respective gate and its respective source,a first comparator configured to cause the second drain to source voltage to be a replica of the first drain to source voltage; anda second comparator configured to cause the second gate to source voltage to be a replica of the first gate to source voltage.