Battery charge termination voltage reduction

Abstract

This document discusses, among other things, apparatus, systems, and methods to prevent a voltage of a charging battery from exceeding a voltage threshold, including receiving charging information from a battery and controlling an output current of a travel adapter, including adjusting the received battery current information using a load current to prevent the voltage of the battery from exceeding a voltage threshold, and providing output current limit information to the travel adapter using the adjusted battery current information.

1 . A circuit, comprising:
 a bypass charge circuit coupled between a travel adapter and a battery that is configured to provide unregulated power directly from the travel adapter to the battery when enabled; and   a charge control circuit coupled to the travel adapter, the battery, and the bypass charge circuit, the charge control circuit configured to:
 compute a load current as a difference between a sensed battery current and a current limit of the travel adapter; and 
 provide a signal to reduce an output current of the travel adapter according to the load current while the bypass charge circuit is enabled. 
   
     
     
         2 . The circuit according to  claim 1 , wherein the output current of the travel adapter is reduced in proportion to the load current to protect the battery from damage. 
     
     
         3 . The circuit according to  claim 1 , wherein the load current corresponds to a variable load coupled to the bypass charge circuit so that a change in the variable load causes a change in a battery current supplied to the battery. 
     
     
         4 . The circuit according to  claim 3 , wherein reducing the output current of the travel adapter according to the load current while the bypass charge circuit is enabled prevents a battery voltage of the battery from exceeding a maximum voltage level when the change in the variable load occurs. 
     
     
         5 . The circuit according to  claim 1 , further comprising:
 a charger coupled between the travel adapter and the battery that is configured to receive unregulated power directly from the travel adapter and to provide regulated power to the battery when the bypass charge circuit is disabled.   
     
     
         6 . The circuit according to  claim 5 , wherein the charger is a switching charger. 
     
     
         7 . The circuit according to  claim 5 , wherein the charger is a linear charger. 
     
     
         8 . The circuit according to  claim 5 , wherein the charge control circuit is further configured to:
 receive a battery voltage;   compare the battery voltage to a bypass threshold to obtain a comparison, and   enable or disable the bypass charge circuit according to the comparison.   
     
     
         9 . The circuit according to  claim 8 , wherein the bypass charge circuit is:
 enabled when the battery voltage is below the bypass threshold; and   disabled when the battery voltage is above the bypass threshold.   
     
     
         10 . The circuit according to  claim 8 , wherein enabling the bypass charge circuit when the battery voltage is below the bypass threshold reduces heat dissipated during charging and/or reduces a charging time. 
     
     
         11 . The circuit according to  claim 8 , wherein the charge control circuit receives the battery voltage from an analog-to-digital converter configured to sense the battery voltage. 
     
     
         12 . The circuit according to  claim 11 , wherein the analog-to-digital converter is further configured to sense the sensed battery current from a current sense resistor. 
     
     
         13 . The circuit according to  claim 1 , wherein the charge control circuit includes a communication channel configured to provide information to the travel adapter. 
     
     
         14 . The circuit according to  claim 13 , wherein the communication channel is a universal serial bus (USB). 
     
     
         15 . A method for charging a battery comprising:
 sensing a battery voltage of the battery;   comparing the battery voltage to a bypass threshold to obtain a comparison;   enabling, based on the comparison, a bypass charge circuit to couple unregulated power directly from a travel adapter to charge a battery and to power a variable load;   sensing a battery current from the battery;   computing a computed load current supplied to the variable load as a difference between the battery current and a current limit of the travel adapter; and   reducing an output current of the travel adapter according to the computed load current supplied to the variable load while charging the battery.   
     
     
         16 . The method for charging a battery according to  claim 15 , wherein the reducing the output current of the travel adapter according to the computed load current supplied to the variable load while charging the battery includes:
 preventing the battery voltage from exceeding a maximum voltage when the variable load is changed.   
     
     
         17 . The method for charging a battery according to  claim 15 , further comprising:
 disabling, based on the comparison, the bypass charge circuit so that a charger, coupled between the travel adapter and the battery, is configured to receive the unregulated power directly from the travel adapter and provide regulated power to the battery.   
     
     
         18 . The method for charging a battery according to  claim 17 , wherein the bypass charge circuit is enabled when the battery voltage is below the bypass threshold and enabled when the battery voltage is above the bypass threshold. 
     
     
         19 . The method for charging a battery according to  claim 18 , wherein the bypass threshold is set to decrease heat associated with the charger during charging and increase a speed at which the battery is charged. 
     
     
         20 . The method for charging a battery according to  claim 15 , wherein the reducing an output current of the travel adapter according to the computed load current supplied to the variable load while charging the battery includes:
 sending information to the travel adapter over a communication channel, the information causing the travel adapter to reduce the output current.