Ciruitry for portable lighting devices and portable rechargeable electronic devices

Abstract

A portable rechargeable electronic device, such as a flashlight, with external charging contacts and a short protection circuit is disclosed. The short protection circuit electrically uncouples one of the exposed charging contacts from the rechargeable power supply for the device when the charging contacts are short circuited. The charging contact is uncoupled without opening the power circuit for the device; thus, the device can continue to operate while the charging contacts are shorted. The power supply for the device may be a rechargeable lithium-ion battery pack.

1 . A rechargeable electronic device comprising:
 a main power circuit including a portable power source and a power consuming load;   a first charging contact electrically coupled to a first electrode of the power source via a first electrical path;   a second charging contact electrically coupled to a second electrode of the power source via a second electrical path;   a printed circuit board; and   a short protection circuit formed on the printed circuit board having a switch interposed at a location that is not within the main-power circuit, wherein the short protection circuit is configured to open the switch if the first and second charging contacts are shorted together.   
     
     
         2 . The rechargeable electronic device of  claim 1 , wherein the short protection circuit includes a comparing device, and the comparing device compares a voltage of a first input signal to a voltage of a second input signal and opens or closes the switch based on the comparison. 
     
     
         3 . The rechargeable electronic device of  claim 2 , wherein the voltage of the first input signal is proportional to the voltage drop between the first charging contact and ground and the voltage of the second input signal is proportional to the voltage of the power source. 
     
     
         4 . The rechargeable electronic device of  claim 3 , wherein the comparing device signals the switch to open when the voltage of the second input signal is greater than the voltage of the first input signal. 
     
     
         5 . The rechargeable electronic device of  claim 4 , wherein the voltage of the first input signal is greater than 50% and less than 60% of the voltage drop between the first charging contact and ground. 
     
     
         6 . The rechargeable electronic device of  claim 1 , wherein the switch is a transistor. 
     
     
         7 . The rechargeable electronic device of  claim 6 , wherein the switch is a p-channel MOSFET. 
     
     
         8 . The rechargeable electronic device of  claim 2 , wherein the comparing device is a voltage comparator. 
     
     
         9 . The rechargeable electronic device of  claim 1 , wherein the rechargeable electronic device is a flashlight. 
     
     
         10 . The rechargeable electronic device of  claim 1 , wherein the portable power source comprises a rechargeable lithium-ion battery pack. 
     
     
         11 . A rechargeable flashlight comprising:
 a portable power source;   a lamp electrically coupled to the portable power source through a main power circuit;   a first charging contact electrically coupled to a first electrode of the power source through a first electrical path;   a second charging contact electrically coupled to a second electrode of the portable power source through a second electrical path;   a printed circuit board; and   a logic circuit formed on the printed circuit board for controlling a switch interposed at a location that is not within the main power circuit, wherein the logic circuit signaling the switch to open if the first and second charging contacts are shorted together.   
     
     
         12 . The rechargeable flashlight of  claim 11 , further comprising a barrel, wherein the barrel contains the power source and the second charging contact comprises at least a portion of the barrel. 
     
     
         13 . The rechargeable flashlight of  claim 11  wherein the logic circuit includes a comparing device, and the comparing device compares a voltage of a first input signal to a voltage of a second input signal and opens or closes the switch based on the comparison. 
     
     
         14 . The rechargeable flashlight of  claim 13 , wherein the voltage of the first input signal is proportional to the voltage drop between the first charging contact and ground and the voltage of the second input signal is proportional to the voltage of the power source. 
     
     
         15 . The rechargeable flashlight of  claim 14 , wherein the comparing device signals the switch to open when the voltage of the first input signal is less than the voltage of the second input signal. 
     
     
         16 . The rechargeable flashlight of  claim 15 , wherein the voltage of the first input signal is greater than 50% and less than 60% of the voltage drop between the first charging contact and ground. 
     
     
         17 . The rechargeable flashlight of  claim 11 , wherein the switch is a transistor. 
     
     
         18 . The rechargeable flashlight of  claim 11 , wherein the switch is a p-channel MOSFET. 
     
     
         19 . The rechargeable flashlight of  claim 13 , wherein the comparing device is a voltage comparator. 
     
     
         20 . The rechargeable flashlight of  claim 11 , wherein the power source comprises a rechargeable lithium-ion battery pack.