Distinguishing network interface card from short circuit condition in power over ethernet system
View Patent ↗Novel system and methodology for distinguishing a Network Interface Card (NIC) from a short circuit condition in a Power over Ethernet (PoE) system. A system for providing power to a powered device (PD) includes a PD probing circuit that generates a detection signal supplied to a device being probed and determines a response signal produced in response to the detection signal, and a control circuit that determines a detection value based on the response signal. The control circuit detects a short circuit if the detection value is in a first predetermined range, and detects a NIC if the detection value is in a second predetermined range outside of the first predetermined range.
1. A system for providing power to a powered device (PD) in a Power over Ethernet (PoE) system, comprising:
a PD probing circuit for determining first and second response signals produced in response to respective first and second detection signals supplied over an Ethernet link to a device being probed, and
a control circuit, configured for:
controlling the PD probing circuit to supply over the Ethernet link the second detection signal greater than the first detection signal if the first response signal does not exceed a threshold value, and
determining that a short circuit condition is detected if a detection value defined by a difference between the second response signal and the first response signal is in a first predetermined range, and determining that a Network Interface Card connected to the Ethernet link is detected if the detection value is in a second predetermined range outside of the first predetermined range.
2. The system of claim 1 , wherein the control circuit is configured for determining that an improper device is detected if the detection value is in a third predetermined range outside of the first and second predetermined ranges.
3. The system of claim 1 , wherein the detection value includes a detection resistance value indicating a resistance of the device being probed.
4. The system of claim 3 , wherein the control circuit is configured to determine that the short circuit condition is detected if the detection resistance value is less than a first predetermined resistance.
5. The system of claim 4 , wherein the control circuit is configured to determine that the Network Interface Card is detected if the detection resistance value is in a range between the first predetermined resistance and a second predetermined resistance higher than the first predetermined resistance.
6. The system of claim 5 , wherein the control circuit is configured to determine that an improper device is detected if the detection resistance value exceeds the second predetermined resistance.
7. A Power Sourcing Equipment (PSE) in a Power over Ethernet (PoE) system, comprising:
a probing circuit for determining a first response voltage produced in response to a first detection current supplied over an Ethernet link to a device being probed, and for determining a second response voltage produced in response to a second detection current supplied over the Ethernet link if the first response voltage is less that a threshold value, the second detection current being greater than the first detection current, and
a detection circuit responsive to the probing circuit to determine a detection resistance value indicating a resistance of the device being probed, the detection resistance value being defined by a difference between the second response voltage and the first response voltage,
the detection circuit being configured for determining that a short circuit condition is detected if the detection resistance value is in a first predetermined range, and determining that a Network Interface Card connected to the Ethernet link is detected if the resistance detection value is in a second predetermined range outside of the first predetermined range.
8. The PSE of claim 7 , wherein the detection circuit is configured for determining that an improper device is detected if the detection resistance value is in a third predetermined range outside of the first and second predetermined ranges.
9. The PSE of claim 7 , wherein the detection circuit is configured to determine that a short circuit condition is detected if the detection resistance value is less than a first predetermined resistance.
10. The PSE of claim 9 , wherein the detection circuit is configured to determine that the Network Interface Card is detected if the detection resistance value is in a range between the first predetermined resistance and a second predetermined resistance higher than the first predetermined resistance.
11. The PSE of claim 10 , wherein the detection circuit is configured to determine that the improper device is detected if the resistance detection value exceeds the second predetermined resistance.
12. A method of detecting a powered device (PD) in a Power over Ethernet (PoE) system, comprising the steps of:
producing a first detection signal supplied to a device being probed to determine a first response signal,
producing a second detection signal larger than the first detection signal if the first response signal is less than a threshold value,
determining a detection resistance value defined by a difference between a second response signal produced in response to the second detection signal, and the first response signal,
detecting a short circuit condition if the detection resistance value is less than a first predetermined resistance,
detecting a Network Interface Card if the detection resistance value is in a range between the first predetermined resistance and a second predetermined resistance higher than the first predetermined resistance; and
indicating a result of detection.
13. The method of claim 12 , further comprising the step of detecting an improper device if the resistance detection value exceeds the second predetermined resistance.