MPS Generation System and Method

Abstract

An MPS generation method, the method constituted of: at a predetermined frequency, alternately outputting a first MPS current pulse for a predetermined first time period and not outputting the first MPS current pulse for a predetermined first off time period; during the first time period, determining the magnitude of a current drawn by an input capacitor of a DC to DC converter; and responsive to the determined input capacitor current magnitude, outputting between the first terminal and the second terminal a second MPS current pulse for a predetermined second time period during the predetermined first off time period.

1 . A powered device (PD) interface comprising:
 a first terminal and a second terminal arranged for connection towards a power supply equipment;   a maintain power signature (MPS) circuitry;   a current sense circuitry arranged to sense the magnitude of a current flowing therethrough; and   a control circuitry in communication with said current sense circuitry, said MPS circuitry responsive to said control circuitry,   wherein said MPS circuitry is arranged, at a predetermined frequency, responsive to said control circuitry, to alternately:
 output a first current pulse for a predetermined first time period; and 
 not output said first current pulse for a predetermined first off time period, 
   wherein said control circuitry is arranged, responsive to said sensed current magnitude, to compare the magnitude of a current sensed by the current sense circuitry to a predetermined minimum magnitude current value,   wherein said control circuitry is arranged, responsive to comparing the magnitude of a current sensed by the current sense circuitry to a predetermined minimum magnitude current value to output a second current pulse for a predetermined second time period during said predetermined first off time period if the magnitude of the current sensed by the current sense circuitry is less than the predetermined minimum magnitude current value.   
     
     
         2 . The PD interface of  claim 1 , wherein the predetermined minimum magnitude current value is a predetermined function of a nominal magnitude of current drawn by the MPS circuitry. 
     
     
         3 . The PD interface of  claim 1  wherein the predetermined minimum magnitude current value is equal to 0.5 mA less than the magnitude of current drawn by the MPS circuitry during the first current pulse. 
     
     
         4 . The PD interface of  claim 1 , wherein the predetermined minimum magnitude current value is about 10 mA. 
     
     
         5 . The PD interface of  claim 1 , wherein:
 said control circuitry is arranged, responsive to said sensed current magnitude, to compare the magnitude of the current sensed by the current sense circuitry to the predetermined minimum magnitude current value for a predetermined evaluation period, and   wherein said control circuitry is arranged, responsive to comparing the magnitude of a current sensed by the current sense circuitry to the predetermined minimum magnitude current value to output the second current pulse for the predetermined second time period during said predetermined first off time period if the magnitude of the current sensed by the current sense circuitry is less than the predetermined minimum magnitude current value for the predetermined evaluation period.   
     
     
         6 . The PD interface of  claim 5 , wherein said control circuitry is arranged to output a second current pulse for the predetermined second time period during said predetermined first off time period if the magnitude of the current sensed by the current sense circuitry is less than the predetermined minimum magnitude current value for a predetermined evaluation period of about 0.5 mS. 
     
     
         7 . The PD interface of  claim 1 , wherein said current sense circuitry is coupled between said MPS circuitry and a DC to DC converter input capacitor. 
     
     
         8 . The PD interface of  claim 1 , wherein said predetermined second time period is greater than said predetermined first time period. 
     
     
         9 . The PD interface of  claim 1 , wherein said predetermined first time period is about 7 mS and the predetermined second time period is about 75 mS. 
     
     
         10 . A maintain power signature (MPS) generation method, the method comprising:
 at a predetermined frequency, alternately outputting a first MPS current pulse for a predetermined first time period and not outputting said first MPS current pulse for a predetermined first off time period;   during said first time period, sensing the magnitude of a current drawn during the output of the first MPS current pulse; and   responsive to said sensed current magnitude being less than a predetermined minimum magnitude current value, outputting between the first terminal and the second terminal a second MPS current pulse for a predetermined second time period during said predetermined first off time period;   upon completion of said output second current pulse, not outputting either of said first current pulse or said second current pulse for a predetermined second off time period having a length that is generally equal to the length of said predetermined first off time period; and   upon completion of said predetermined second off time period, outputting said first current pulse.   
     
     
         11 . The MPS generation method of  claim 10 , wherein the predetermined minimum magnitude current value is a predetermined function of a nominal magnitude of current drawn by the MPS circuitry. 
     
     
         12 . The MPS generation method of  claim 10 , wherein the predetermined minimum magnitude current value is equal to 0.5 mA less than the magnitude of current drawn by the MPS circuitry during the first current pulse. 
     
     
         13 . The MPS generation method of  claim 10 , wherein the predetermined minimum magnitude current value is about 10 mA. 
     
     
         14 . The MPS generation method of  claim 10 , further comprising:
 responsive to said sensed current magnitude, comparing the magnitude of the current sensed by the current sense circuitry to a predetermined minimum magnitude current value for a predetermined evaluation period, and   responsive to comparing the magnitude of a current sensed by the current sense circuitry to a predetermined minimum magnitude current value, outputting the second current pulse for the predetermined second time period during said predetermined first off time period if the magnitude of the current sensed by the current sense circuitry is less than the predetermined minimum magnitude current value for the predetermined evaluation period.   
     
     
         15 . The MPS generation method of  claim 14 , wherein outputting the second current pulse for a predetermined second time period during said predetermined first off time period comprises outputting the second current pulse if the magnitude of the current sensed by the current sense circuitry is less than the predetermined minimum magnitude current value for a predetermined evaluation period of about 0.5 mS. 
     
     
         16 . The MPS generation method of  claim 10 , wherein sensing the magnitude of the current drawn during the output of the first MPS current pulse comprises sensing said current drawn between said MPS circuitry and a DC to DC converter input capacitor. 
     
     
         17 . The MPS generation method of  claim 10 , wherein said predetermined second time period is greater than said predetermined first time period. 
     
     
         18 . The MPS generation method of  claim 10 , wherein said predetermined first time period is about 7 mS and the predetermined second time period is about 75 mS.