Providing power to powered device having multiple power supply inputs

Abstract

A system for providing power to a load, having first and second power supply inputs respectively responsive to first and second input signals from first and second power supply sources to supply power to the load. For example, the first power supply input may be configured for supplying the load with power received from a communication link, such as an Ethernet link, and the second power supply input may be configured for supplying the load with power from an auxiliary power source. A power converter is provided to produce an output signal for supplying power to the load in response to the second input signal. The power converter is controlled to produce the output signal in accordance with a value of the first input signal.

1 . A system for providing power to a load comprising:
 a first power supply input responsive to a first input signal from a first power supply source to supply power to the load, and   a second power supply input responsive to a second input signal from a second power supply source to supply power to the load,   a power converter responsive to the second input signal to produce an output signal for supplying power to the load,   the power converter being controlled to produce the output signal in accordance with a value of the first input signal.   
     
     
         2 . The system of  claim 1 , wherein the power converter is controlled to produce the output signal so as to make a difference between a value of the output signal and the value of the first input signal smaller than a difference between a value of the second input signal and the value of the first input signal. 
     
     
         3 . The system of  claim 1 , further comprising a priority mechanism for enabling a user to select between supplying the load from the first power supply input and supplying the load from the second power supply input when both the first and second power supply inputs are provided with power values sufficient to power the load. 
     
     
         4 . The system of  claim 3 , wherein the priority mechanism includes a converter control circuit responsive to a priority select signal for producing a converter control signal for controlling the power converter so as to power the load from a power supply input selected between the first and the second power supply inputs when both the first and second power supply inputs are provided with power values sufficient to power the load. 
     
     
         5 . The system of  claim 4 , wherein the power converter is responsive to the converter control signal to produce the output signal at a level selected to enable the selected power supply input to provide power to the load and to prevent a non-selected power supply input from supplying power to the load. 
     
     
         6 . The system of  claim 4 , wherein the power converter is responsive to the converter control signal to produce the output signal having a value lower than a value of the first power supply signal if the first power supply input is selected to power the load, and to produce the output signal having a value higher than the value of the first power supply signal if the second power supply input is selected to power the load. 
     
     
         7 . The system of  claim 3 , wherein the priority mechanism is configured to enable the user to change a priority of one power supply input over another power supply input when both power supply inputs are provided with power values sufficient to power the load. 
     
     
         8 . The system of  claim 1 , further comprising a power supply sensing mechanism for sensing the second input signal at the second power supply input so as to enable the power converter to operate as a DC/DC converter when the second input signal is a DC signal and to operate as an AC/DC converter when the second input signal is an AC signal. 
     
     
         9 . The system of  claim 1 , wherein the first power supply input is configured for supplying the load with power received from an Ethernet link, and the second power supply input is configured for supplying the load with power from an auxiliary power source. 
     
     
         10 - 31 . (canceled) 
     
     
         32 . A method of providing power to a powered device from first and second power supply inputs, including the steps of:
 converting a first power supply signal from a first power supply input to produce an output signal having a first value selected to power the powered device from the first power supply input and to prevent the second power supply input from powering the powered device, and   converting the first power supply signal from the first power supply input to produce the output signal having a second value selected to power the powered device from the second power supply input and to prevent the first power supply input from powering the powered device.   
     
     
         33 . The method of  claim 32 , wherein a value of the output signal is controlled in accordance with a value of a second power supply signal from the second power supply input. 
     
     
         34 . The method of  claim 32 , further comprising the step of controlling the output signal so as to switch power supply of the powered device between the first power supply input and the second power supply input without disrupting power supplied to the powered device. 
     
     
         35 . The method of  claim 32 , further comprising the step of controlling the output signal so as to select either the first power supply input or the second power supply input for powering the powered device when both the first power supply input and the second power supply input are available to provide sufficient power to power the powered device.