Time-based current control in switching regulators

Abstract

Control circuits that employ time-based current control methods for switching voltage regulators are provided. The control circuit includes a current estimation circuit and optionally, a transfer function circuit. The current estimation circuit generates estimates of regulator output current as function of switch period for use as a threshold indicative of peak current limit. This arrangement eliminates the need for error amplifiers to provide effective current mode control. The absence of error amplifiers allows fabrication of switching regulators on smaller die areas and provides switching regulators with reduced power consumption.

1 - 29 . (canceled)  
   
   
       30 . A system comprising: 
 a current-mode regulator, having an output switch with a switching threshold, that provides an output current at a voltage; and    a controller, coupled to said current-mode regulator, that provides a time-based estimate of said output current by measuring a switching period of said output switch and provides a control signal to said current-mode regulator to regulate said voltage by adaptively adjusting said switching threshold.    
   
   
       31 . The system of  claim 30 , wherein said time-based estimate of said output current estimates the peak of said output current.  
   
   
       32 . The system of  claim 30 , wherein said voltage is regulated such that said voltage is maintained substantially constant.  
   
   
       33 . The system of  claim 30 , wherein the controller comprises a estimation circuit for providing said time-based estimate of said output current, wherein said estimation circuit comprises at least one capacitive element.  
   
   
       34 . The system of  claim 33 , wherein said estimation circuit further comprises a voltage source coupled to said at least one capacitive element.  
   
   
       35 . The system of  claim 34 , wherein said voltage source charges said at least one capacitive element to a predetermined initial condition.  
   
   
       36 . The system of  claim 33 , wherein said estimation circuit further comprises a current source coupled to said at least one capacitive element for discharging the at least one capacitive element at a predetermined rate.  
   
   
       37 . The system of  claim 33 , wherein said estimation circuit further comprises: 
 a voltage source coupled to said at least one capacitive element for charging said at least one capacitive element; and    a current source coupled to said at least one capacitive element for discharging said at least one capacitive element.    
   
   
       38 . The system of  claim 33 , wherein said estimation circuit further comprises: 
 a voltage source coupled to said at least one capacitive element for charging said at least one capacitive element to a predetermined initial condition; and    a current source coupled to said at least one capacitive element for discharging said at least one capacitive element at a predetermined rate.    
   
   
       39 . The system of  claim 33 , wherein said estimation circuit further comprises: 
 a voltage source coupled to said at least one capacitive element for charging said at least one capacitive element to a predetermined initial condition; and    a current source coupled to said at least one capacitive element for discharging said at least one capacitive element at a predetermined rate for a period of time such that the charge remaining on said at least one capacitive element is proportional to said output current of said regulator.    
   
   
       40 . The system of  claim 33 , wherein said estimation circuit further comprises a switching element for selectively charging the at least one capacitive element to a predetermined initial condition.  
   
   
       41 . The system of  claim 30 , wherein said controller comprises a transfer function circuit for exponentially relating said estimate to said switching period.  
   
   
       42 . The system of  claim 30 , wherein said controller comprises a transfer function circuit for linearly relating said estimate to said switching period.  
   
   
       43 . The system of  claim 30 , wherein said controller comprises a transfer function circuit for relating said estimate to said switching period.  
   
   
       44 . The system of  claim 30 , wherein said controller provides a second time-based estimate of said output current by measuring a second switching period of said output switch.  
   
   
       45 . The system of  claim 44 , wherein said controller provides an average value of said time-based estimate and said second time based estimate.  
   
   
       46 . A system comprising: 
 regulator means, having an output switch with a switching threshold, for providing an output current at a voltage; and    controller means, coupled to regulator means, for providing a time-based estimate of said output current by measuring a switching period of said output switch and providing a control signal to said regulator means to regulate said voltage by adaptively adjusting said switching threshold.    
   
   
       47 . The system of  claim 46 , wherein said time-based estimate of said output current estimates the peak of said output current.  
   
   
       48 . The system of  claim 46 , wherein said voltage is regulated such that said voltage is maintained substantially constant.  
   
   
       49 . The system of  claim 46 , wherein said controller means comprises estimation means for providing said time-based estimate of said output current, wherein said estimation means comprises at least one capacitive element.  
   
   
       50 . The system of  claim 49 , wherein said estimation means further comprises a voltage source coupled to said at least one capacitive element.  
   
   
       51 . The system of  claim 50 , wherein said voltage source charges said at least one capacitive element to a predetermined initial condition.  
   
   
       52 . The system of  claim 49 , wherein said estimation means further comprises a current source coupled to said at least one capacitive element for discharging said at least one capacitive element at a predetermined rate.  
   
   
       53 . The system of  claim 49 , wherein said estimation means further comprises: 
 a voltage source coupled to said at least one capacitive element for charging said at least one capacitive element; and    a current source coupled to said at least one capacitive element for discharging said at least one capacitive element.    
   
   
       54 . The system of  claim 49 , wherein said estimation means further comprises: 
 a voltage source coupled to said at least one capacitive element for charging said at least one capacitive element to a predetermined initial condition; and    a current source coupled to said at least one capacitive element for discharging said at least one capacitive element at a predetermined rate.    
   
   
       55 . The system of  claim 49 , wherein said estimation means further comprises: 
 a voltage source coupled to said at least one capacitive element for charging said at least one capacitive element to a predetermined initial condition; and    a current source coupled to said at least one capacitive element for discharging said at least one capacitive element at a predetermined rate for a period of time such that the charge remaining on said at least one capacitive element is proportional to said output current of said regulator.    
   
   
       56 . The system of  claim 49 , wherein said estimation means further comprises a switching element for selectively charging said at least one capacitive element to a predetermined initial condition.  
   
   
       57 . The system of  claim 46 , wherein said controller means comprises a transfer function means for exponentially relating said estimate to said switching period.  
   
   
       58 . The system of  claim 46 , wherein said controller means comprises a transfer function means for linearly relating said estimate to said switching period.  
   
   
       59 . The system of  claim 46 , wherein said controller means comprises a transfer function means for relating said estimate to said switching period.  
   
   
       60 . The system of  claim 46 , wherein said controller means provides a second time-based estimate of said output current by measuring a second switching period of said output switch.  
   
   
       61 . The system of  claim 60 , wherein said controller provides an average value of said time-based estimate and said second time based estimate.