Abstract:
The present invention provides methods and apparatuses for the detection and warning of a critical voltage of a vehicle battery. An apparatus includes a voltage regulator, a voltage-level detector, a logic circuit, and a light-emitting diode (LED) with a current-protection circuit for providing an indication when the battery voltage drops below a critical voltage level.

Description:
[0001]     This application claims priority to provisional U.S. Application Ser. No. 60/608,253 (“Critical-Voltage Indicator for Automobiles”), filed Sep. 9, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to apparatuses that determine whether a voltage of a vehicle battery is below a threshold when the vehicle ignition is activated.  
       BACKGROUND OF THE INVENTION  
       [0003]     The voltage level at the terminals of a vehicle battery typically ranges from 12 to 14 Vdc if the battery is fairly new (within the first three years of purchase). During the useful life of a battery, any loss of electrical charge (corresponding to battery voltage) is replenished by the vehicle&#39;s alternator/charger system. However, with time, due to corrosion and mineral accumulation in the battery, individual cells within the battery lose their ability to retain sufficient charge to start the engine when the ignition is activated.  
         [0004]     One typically becomes aware of a dead or a rapidly dying battery/charger by a fading sound when cranking the engine, a total silence of the starter following the activation of the ignition key, or the sudden stoppage of the engine after a quick braking of the vehicle. Needless to say, these symptoms are too late to prevent an unexpected, inconvenient, and possibly a potentially dangerous situation for the driver and passengers of the vehicle.  
         [0005]     The prior art provides battery-charge indicators and battery voltage-level detectors. However, there is a real need for alarm apparatus to warn an operator of a vehicle about the condition of the battery/charger.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides methods and apparatuses for the detection and warning of a critical voltage of a vehicle battery. In an embodiment of the invention, an apparatus includes a voltage regulator, a voltage-level detector, a logic circuit, and a light-emitting diode (LED) with a current-protection circuit for providing a visual warning light when the battery voltage drops below a critical voltage level. In an embodiment of the invention, complimentary metal oxide semiconductor (CMOS) technology is incorporated, providing a wide operating range for the supply voltage, low-quiescent current, and low-power consumption.  
         [0007]     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description in consideration of the accompanying drawings, in which like reference numbers indicate like features and wherein:  
         [0009]      FIG. 1  is a circuit diagram of an apparatus in accordance with an embodiment of the invention; and  
         [0010]      FIG. 2  shows an implementation of an apparatus in accordance with an embodiment of the invention. 
     
    
       [0011]     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof.  
       DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0012]      FIG. 1  shows circuit diagram  100  of an apparatus in accordance with an embodiment of the invention. For a very distinct and pre-selected range of battery voltages (corresponding to V bat    101 ), zener diode  103  (D 1 ) and resistor  105  (R 3 ) perform two functions: 
    provide a regulated supply voltage to comparator  107  (U 1 A) and     establish a reference voltage at its inverting terminal  109 .      
         [0015]     Resistor  111  (R 6 ) and NAND gate  113  (U 2 A) ensure that under all normal conditions U 2 A output  115  (pin  3 ) is always at a low logic level.  
         [0016]     The voltage level at inverting terminal  109  is typically held at a voltage level approximately equal to the critical voltage of the battery as determined by resistors  135  and  137 . Also, a voltage level at non-inverting input  133  of comparator  107  is set by resistors  139  and  141 . With a good battery that is well charged, the voltage at non-inverting input  133  is greater than the voltage at inverting input  109 . Whenever, the battery voltage drops below the critical value, the output voltage of comparator  107  drops to approximately zero volts. The drop of the output voltage initiates a warning signal, as will be discussed.  
         [0017]     CMOS gate  117  U 2 B and its associated components (C 1   119 , D 2   121 , and R 7   123 ) perform a power-up reset function to remove any ambiguities at U 3 A output  125  (pin  1 ), whenever power is applied (e.g., when the ignition is activated).  
         [0018]     NAND gates  127  and  129  (U 2 C and U 2 D, respectively) also insure that, under normal battery operation, the voltage of U 3 A output  125  is kept a low logic level. Should a low battery voltage exist, apparatus  100  causes U 3 A output  125  to change to a high logic level, typically within 3 msec. Consequently red light emitting diode (LED)  127  activates and emits light.  
         [0019]     When the ignition key (not shown) is activated and if the battery voltage V bat    101  drops to a specific level, comparator  107  (U 1 A) trips, causing the output of gate  113  to transition from a low logic level (Lo) to a high logic level (Hi). The resulting rising-edge, voltage-step clocks flip flop  131  (U 3 A) into a set mode (corresponding to output  125  being at a high logic level) and causes LED  127  to light. LED  127  remains on until either the power is removed (ignition is deactivated) or the battery voltage is restored.  
         [0020]     On the other hand, if a low voltage condition existed while the vehicle was not in use, once any attempt is made to start the engine, the LED will light (typically after 3 msec) and will remain on.  
         [0021]      FIG. 2  shows an implementation of an apparatus in accordance with an embodiment of the invention. Both a functional prototype (corresponding to “Functional Prototype”) and a post-prototype implementation (corresponding to “Real Size”) of apparatus  100  are shown. Other embodiments of the invention may be implemented with an application specific integrated circuit chip (ASIC) or with a processor that interfaces with an analog to digital converter.  
         [0022]     Embodiments of the invention provide a voltage indication for a battery system for a vehicle (e.g., as an automobile, motorcycle, or truck) that is propelled by an internal combustion engine, e.g., spark ignition engine or Diesel engine. Other embodiments of the invention support a vehicle that is propelled by an electric motor or by a hybrid motor configuration (e.g., comprising an electric motor and a gasoline engine).  
         [0023]     It should be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It is also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.  
         [0024]     Various features of the invention are set forth in the following claims.