Devices and methods for protection of rechargeable elements

Abstract

A protection circuit for use with a charger and a chargeable element, such as a rechargeable lithium ion battery, comprises a shunt regulator having a threshold ON voltage coupled in parallel across the chargeable element, and a temperature-dependent resistor, e.g., a positive temperature coefficient device, coupled in series between the charger and the chargeable element. The temperature dependent resistor is thermally and electrically coupled to the shunt regulator, wherein the first variable resistor limits current flowing through the shunt regulator if the current reaches a predetermined level less than that which would cause failure of the regulator, due to ohmic heating of the regulator.

1 - 44 . (canceled)  
     
     
         45 . A method for manufacturing a circuit protection device, comprising: 
 forming a substrate comprising a positive temperature coefficient material;    applying an electrically conductive layer to a first surface of the substrate; and    attaching a thermally and electrically conductive element of a voltage regulation device to the conductive layer.    
     
     
         46 . The method of  claim 45 , the voltage regulation device comprising: 
 a transistor formed on a die; and    a heat sink comprising the thermally and electrically conductive element, the heat sink having a first surface attached to the die, and a second surface attached to the conductive layer.    
     
     
         47 . The method of  claim 46 , wherein the transistor is a MOSFET.  
     
     
         48 . A method of manufacturing circuit protection devices, comprising: 
 forming a substrate comprising a positive temperature coefficient material;    applying an electrically conductive layer to a surface of the substrate;    applying an electrically insulating layer on the conductive layer;    removing selected portions of the insulating layer, thereby forming windows in the insulating layer, the windows defining exposed portions of the conductive layer;    attaching voltage regulation devices to the exposed conductive layer portions; and    cutting the substrate into a plurality of pieces.    
     
     
         49 . The method of  claim 48 , wherein the conductive layer comprises a foil that is pressed onto the substrate surface.  
     
     
         50 . The method of  claim 48 , wherein the insulating layer is formed using a silk screening process.  
     
     
         51 . The method of  claim 48 , wherein the selected portions of the insulating layer are removed using a photolithography process.  
     
     
         52 . The method of  claim 48 , wherein the voltage regulators are secured to the exposed portions of the conductive layer by: 
 positioning solder material on the exposed portions of the conductive layer,    positioning a thermally and electrically conductive surface of the respective voltage    regulators in contact with the solder material, and    heating the solder material to cause flow of the solder material.    
     
     
         53 . The method of  claim 52 , the voltage regulators each comprising: 
 a transistor formed on a die, and    a heat sink, the heat sink having a first surface and a second surface, the second surface comprising the thermally and electrically conductive surface,    wherein the die is attached to the first heat sink surface such that the transistor switch is thermally coupled to the heat sink.    
     
     
         54 . The method of  claim 53 , wherein the windows in the insulating layer are sized such that, during the flow of the solder material, the respective heat sinks will self-center within the windows.  
     
     
         55 . The method of  claim 52 , wherein the voltage regulators are secured to the exposed portions of the conductive layer prior to when the substrate is cut into a plurality of pieces.  
     
     
         56 . The method of  claim 52 , wherein the voltage regulators are secured to the exposed portions of the conductive layer after the substrate is cut into a plurality of pieces.  
     
     
         57 . The method of  claim 48 , each of the plurality of pieces comprising a variable resistor chip having a voltage protection device secured to an exposed portion of the conductive layer.