Capacitor startup apparatus and method with failsafe short circuit protection

Abstract

Electronic circuits couple energy storage devices, such as double layer capacitors or rechargeable battery cells, to a power supply output, thereby improving noise suppression and extending ride-through capability of the power supply. In a typical circuit, an energy storage device is coupled in series with a switch that controls the charging current into the energy storage device. The switch is controlled by a comparator that receives a signal related to the voltage level of the power supply. In some embodiments, the comparator also receives a feedback signal related to a charging current flowing into the energy storage device. The circuit is configured so that the switch limits the charging current to a predetermined current level, or does not allow the charging current to flow until the output voltage of the power supply reaches a predetermined voltage level.

1 . A method for coupling an energy storage device to an output of a power supply, the method comprising:
 coupling the energy storage device in series with a switch controllable by a switching signal;   generating a feedback signal representing current flowing into the energy storage device;   comparing the feedback signal to a predetermined control signal; and   generating the switching signal to turn off the switch when the comparing step indicates that the current is not lower than a predetermined level.   
     
     
         2 . A method for coupling an energy storage device to an output of a power supply, the method comprising:
 coupling the energy storage device in series with a switch controllable by a switching signal;   generating a reference signal;   generating a signal representing voltage at the output of the power supply;   comparing the reference signal to the signal representing voltage at the output of the power supply; and   generating the switching signal to turn off the switch when the comparing step indicates that the voltage at the output of the power supply is below a predetermined level.   
     
     
         3 . A system for use with a power supply, comprising:
 a load, the load coupled to output terminals of the power supply;   a charge storage device; and   a current control device, the charge storage device and the current control device coupled to output terminals of the power supply, wherein the current control device controls current flowing through the charge storage device.   
     
     
         4 . The system of  claim 3 , wherein the charge storage device comprises a capacitor. 
     
     
         5 . The system of  claim 4 , wherein the capacitor comprises a nominal operating voltage of no more than about 3 volts. 
     
     
         6 . The system of  claim 4 , wherein the capacitor comprises a double layer capacitor. 
     
     
         7 . The system of  claim 4 , wherein the capacitor comprises a value between 1 Farad and 5000 Farad. 
     
     
         8 . The system of  claim 3 , wherein the charge storage device comprises 2 series connected capacitors, and wherein to the two series connected capacitors are coupled to a voltage balancing circuit. 
     
     
         9 . A circuit for use with a power supply, comprising:
 a charge storage device; and   a current control device, the charge storage device and the current control device coupled to provide output terminals, wherein the current control device controls current flowing through the charge storage device when the output terminals are coupled to the power supply.   
     
     
         10 . A circuit for use with a power supply, comprising:
 charge storage means for storing charge; and   current control means for controlling current through the charge storage means when the charge storage means and current control means are coupled to the power supply.