Power over data lines detection and classification scheme
A PoDL system includes a PSE connected via a wire pair to a PD, where differential data and DC power are transmitted over the same wire pair. Typically, low voltage/current detection and classification routines are required upon every powering up of the system to allow the PD to convey its PoDL requirements to the PSE. Various techniques are described that simplify or obviate such start-up routines or enable increased flexibility for the PoDL system. Such techniques include: ways to specify a particular PD operating voltage; ways to disable the PD's UVLO circuit during such routines; using opposite polarity voltages for the two routines; using voltage limiters or surge protectors to convey the PoDL information; detecting loop resistance; using a PSE memory to store previous results of the routines; and powering the PD communication circuit using the wire pair while the PD load is powered by an alternate power source.
1. A Power Over Data Lines (PoDL) system comprising:
Power Source Equipment (PSE) coupled to a Powered Device (PD) via a wire pair, wherein differential data signals and DC power are transmitted over the same wire pair, the PSE comprising a first power source for supplying a first voltage to the PD;
the PD comprising a PD load and comprising a digital communications portion, separate from the PD load, for communicating over the wire pair;
an alternate power source coupled to the PD load via other than the wire pair, the alternate power source comprising a second power source generating power independent from the first power source, wherein the second power source is sufficient to fully power the PD load; and
wherein the alternate power source separately powers the PD load while the PSE separately powers the digital communications portion in the PD over the wire pair for allowing data communications via the wire pair.
2. The system of claim 1 wherein the PSE is configured to fully power the PD over the wire pair in the event that power from the alternate power source is removed from the PD.
3. The system of claim 1 wherein the PSE is configured to power to the PD over the wire pair at the same time that power is supplied to the PD by the alternate power source.
4. The system of claim 1 wherein the PSE is configured to initially provide power to the PD upon powering up the PD, followed by the alternate power source providing power to the PD.
5. The system of claim 1 further comprising:
a variable voltage converter in the PSE coupled to receive an input voltage and output a regulated voltage, wherein a magnitude of the regulated voltage is controlled by a control signal;
a classification circuit in the PD coupled to the wire pair;
a PSE controller circuit in the PSE configured to generate classification signals over the wire pair that are received by the classification circuit in the PD and transformed by the classification circuit to provide a classification signature over the wire pair,
wherein the PSE controller circuit detects the classification signature, and wherein the classification signature identifies a particular voltage requirement of the PD;
wherein the PSE controller is configured to control the variable voltage converter to output a voltage corresponding to the particular voltage requirement of the PD identified by the classification signature; and
a PD load coupled to the wire pair for receiving power from the variable voltage converter.
6. A Power Over Data Lines (PoDL) system comprising:
Power Source Equipment (PSE) coupled to a Powered Device (PD) via a wire pair, wherein differential data signals and DC power are transmitted over the same wire pair; and
an alternate power source coupled to the PD via other than the wire pair;
wherein the power transmitted by the PSE over the wire pair powers at least communication circuits in the PD, such that the PD is sufficiently powered via the wire pair to convey information via the wire pair to the PSE,
wherein the PSE is configured to control the alternate power source to power the PD after the PSE determines that the PD and the alternate power source are compatible.