Transient protection and current control of devices

Abstract

An apparatus including an electrical device electrically coupled to a power source and transient suppression and current control circuitry electrically coupled to the electrical device. The circuitry includes a negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge. The circuitry also includes a positive temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to a change in electrical current to maintain the electrical current below an acceptable threshold level.

1 . An apparatus, comprising: 
 an electrical device electrically coupled to a power source; and    transient suppression and current control circuitry electrically coupled to the electrical device, including: 
 a first negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge; and  
 a first positive temperature coefficient thermistor electrically coupled between the power source and the electrical device and being responsive to a change in electrical current to maintain the electrical current below a threshold level.  
   
   
   
       2 . The apparatus of  claim 1 , wherein the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor are electrically connected in series between a first node of the power source and the electrical device.  
   
   
       3 . The apparatus of  claim 2 , wherein the first negative temperature coefficient thermistor is electrically connected to the first node of the power source and wherein the first positive temperature coefficient thermistor is electrically connected between the first negative temperature coefficient thermistor and the electrical device.  
   
   
       4 . The apparatus of  claim 1 , wherein the transient suppression and current control circuitry further includes a second negative temperature coefficient thermistor electrically coupled between the power source and the electrical device and a second positive temperature coefficient thermistor electrically coupled between the power source and the electrical device.  
   
   
       5 . The apparatus of  claim 4 , wherein the second negative temperature coefficient thermistor and the second positive temperature coefficient thermistor are electrically connected in series between a second node of the power source and the electrical device.  
   
   
       6 . The apparatus of  claim 5 , wherein the second negative temperature coefficient thermistor is electrically connected to the second node of the power source and wherein the second positive temperature coefficient thermistor is electrically connected between the second negative temperature coefficient thermistor and the electrical device.  
   
   
       7 . The apparatus of  claim 1 , wherein the electrical device comprises a sensor operable to detect one or more physical characteristics and to provide a corresponding electrical sensor signal.  
   
   
       8 . The apparatus of  claim 7 , wherein the one or more physical characteristics include a change in a magnetic field detectable with the sensor.  
   
   
       9 . The apparatus of  claim 7 , further comprising a controller including the power source, the controller being responsive to the sensor signal.  
   
   
       10 . The apparatus of  claim 9 , further comprising an output device coupled to the controller, the controller being operable to provide an output signal to the output device in response to a change in the sensor signal.  
   
   
       11 . The apparatus of  claim 7 , wherein the sensor and the transient suppression and current control circuitry are incorporated into an integral sensing device unit.  
   
   
       12 . The apparatus of  claim 7 , further comprising at least one indicator electrically coupled to the sensor; and 
 wherein the sensor and the at least one indicator are electrically coupled in series with the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor.    
   
   
       13 . The apparatus of  claim 1 , further comprising a controller including the power source; 
 an output device coupled to the controller; and    wherein the controller is responsive to a change in an electrical output signal provided by the electrical device; and    wherein the controller provides a corresponding control signal to the output device.    
   
   
       14 . The apparatus of  claim 1 , wherein the electrical device and the transient suppression and current control circuitry are incorporated into an integral package assembly.  
   
   
       15 . A method of providing transient suppression and current control, comprising: 
 providing electrical power to an electrical device;    suppressing a transient power surge by dissipating at least a portion of the surge using a negative temperature coefficient thermistor; and    maintaining electrical current below a threshold level using a positive temperature coefficient thermistor.    
   
   
       16 . The method of  claim 15 , wherein the electrical device comprises a sensing device; and 
 wherein the method further comprises detecting a change in one or more physical characteristics with the sensing device.    
   
   
       17 . The method of  claim 15 , further comprising: 
 coupling the electrical device and an output device to a controller;    providing an input signal from the electrical device to the controller; and    providing an output signal to the output device from the controller in response to an input signal from the electrical device.    
   
   
       18 . The method of  claim 15 , wherein the suppressing is provided by a negative temperature coefficient thermistor; and 
 wherein the maintaining is provided by a positive temperature coefficient thermistor; and    wherein the negative temperature coefficient thermistor and the positive temperature coefficient are connected in series between the power source and the electrical device.    
   
   
       19 . The method of  claim 18 , further comprising packaging the electrical device and the thermistors within an integral package body.  
   
   
       20 . An apparatus, comprising: 
 an electrical device;    a connector configured to electrically couple the electrical device to a power source; and    first and second thermistors electrically coupled between the connector and the electrical device, one of the first and second thermistors being responsive to an electrical power surge condition to dissipate at least a portion of the power associated with the surge, another of the first and second thermistors being responsive to a change in electrical current to maintain the electrical current below a threshold level.    
   
   
       21 . The apparatus of  claim 20 , wherein the first thermistor comprises a first negative temperature coefficient thermistor and wherein the second thermistor comprises a first positive temperature coefficient thermistor.  
   
   
       22 . The apparatus of  claim 21 , wherein the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor are electrically connected in series between a first node of the connector and the electrical device.  
   
   
       23 . The apparatus of  claim 22 , wherein the first negative temperature coefficient thermistor is electrically connected to the first node of the connector and wherein the first positive temperature coefficient thermistor is electrically connected between the first negative temperature coefficient thermistor and the electrical device.  
   
   
       24 . The apparatus of  claim 22 , further comprising a second negative temperature coefficient thermistor and a second positive temperature coefficient thermistor; and 
 wherein the second negative temperature coefficient thermistor and the second positive temperature coefficient thermistor are electrically connected in series between a second node of the connector and the electrical device.    
   
   
       25 . The apparatus of  claim 24 , wherein the second negative temperature coefficient thermistor is electrically connected to the second node of the connector and wherein the second positive temperature coefficient thermistor is electrically connected between the second negative temperature coefficient thermistor and the electrical device.  
   
   
       26 . The apparatus of  claim 20 , wherein the electrical device comprises a sensor operable to detect one or more physical characteristics and to provide a corresponding electrical sensor signal.  
   
   
       27 . The apparatus of  claim 26 , further comprising: 
 a controller operable to provide the power source and being responsive to the sensor signal; and    an output device coupled to the controller; and    wherein the controller is operable to provide an output signal to the output device in response to a change in the sensor signal.    
   
   
       28 . The apparatus of  claim 20 , wherein the electrical device and the first and second thermistors are incorporated into an integral package body.  
   
   
       29 . The apparatus of  claim 28 , wherein the connector is incorporated into the integral package body.  
   
   
       30 . A system, comprising: 
 a sensor operable to detect a change in one or more physical characteristics and to provide a corresponding sensor signal;    a controller including a power source electrically coupled to the sensor; and    transient suppression and current control circuitry electrically coupled between the sensor and the power source of the controller, the circuitry including: 
 a first negative temperature coefficient thermistor responsive to an electrical power surge condition to dissipate at least a portion of the electrical power associated with the surge; and  
 a first positive temperature coefficient thermistor responsive to a change in electrical current to maintain the electrical current below a threshold level.  
   
   
   
       31 . The system of  claim 30 , wherein the first negative temperature coefficient thermistor and the first positive temperature coefficient thermistor are connected in series between the power source and the sensor.  
   
   
       32 . The system of  claim 31 , wherein the first negative temperature coefficient thermistor is electrically connected to a first node of the power source and wherein the first positive temperature coefficient thermistor is electrically connected between the first negative temperature coefficient thermistor and the sensor.  
   
   
       33 . The system of  claim 31 , wherein the transient suppression and current control circuitry further includes a second negative temperature coefficient thermistor and a second positive temperature coefficient thermistor electrically connected in series between a second node of the power source and the sensor.  
   
   
       34 . The system of  claim 30 , wherein the one or more physical characteristics include a change in a magnetic field detectable by the sensor.  
   
   
       35 . The system of  claim 30 , wherein the sensor and the transient suppression and current control circuitry are incorporated into an integral sensing device unit.