Identification circuit for power sourcing equipment, and powered device

摘要

An electronic detection circuit for detecting a power level provided by a power sourcing device to a powered device in a Power over Ethernet (POE) system, the electronic detection circuit comprising a power input end, a power output end, a charge retention module configured to generate a control voltage from the input voltage, a load module configured to draw power at a test power level from the power sourcing device, a connection switch, and an overload detection module connected to receive the input voltage to detect whether the input voltage has dropped to zero during the test period.

主权项

1. An electronic detection circuit for detecting a power level provided by a power sourcing device to a powered device in a Power over Ethernet (POE) system, wherein the power sourcing device is capable of providing power at a supply voltage at either a high power level or a low power level and has an overload reaction time for the power sourcing device to shutdown in response to being overloaded, the electronic detection circuit comprising:
a power input end for connecting to the power sourcing device to receive an input voltage from the power sourcing device; a power output end for connecting to the powered device to provide power to the powered device; a charge retention module configured to generate a control voltage from the input voltage, wherein the control voltage is configured to ramp from zero to a threshold voltage value over a test period after the power input end is connected to the power sourcing device, and wherein, when the input voltage is maintained at the supply voltage over the test period, the test period is selected to be longer than the overload reaction time of the power sourcing device; a load module configured to draw power at a test power level from the power sourcing device, wherein the test power level is between the high power level and the low power level, and wherein the load module is controlled by the control voltage to stop drawing power when the control voltage reaches the threshold voltage value; a connection switch controlled by the control voltage and disposed to connect power from the power input end to the power output end when the control voltage reaches the threshold voltage value; and an overload detection module connected to receive the input voltage to detect whether the input voltage has dropped to zero during the test period and to generate a power level indicating signal, the power level indicating signal having a first value indicating that the power sourcing device is of the high power level when the input voltage has not dropped to zero during the test period, and a second value indicating that the power sourcing device is of the lower power level when the input voltage has dropped to zero during the test period.