Abstract:
Apparatus for indicating multiple operating states of a battery charger is formed by first and second color light emitting circuits coupled to a control circuit and one of the output terminals of the battery charger with first and second sense terminals of the respective first and second color light emitting circuits coupled to the other one of the battery charger output terminals such that operating bias may be applied to the light emitting circuits. The light emitting elements of the first and second color light emitting circuits may be positioned to emit light through a common diffusing lens to provide a third color substantially distinct from the first and second colors.

Description:
BACKGROUND OF THE INVENTION 
     Battery chargers are well known in the art as are numerous methods of indicating the operating status of the battery charger when it is connected to a battery for recharging. Such indicators typically range from a simple lamp or a colored spot associated with an on/off switch to built-in current and volt meters or displays with accompanying warning lamps to indicate fault conditions. Heretofore, simpler kinds of indicators have been limited in function. Similarly, indicating systems capable of providing many kinds of status information are usually prohibitively expensive in a low cost battery charging instrument. Thus the need exists for a readout or indicating system capable of multiple indications from the simplest possible structure in order to minimize costs providing this feature. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention apparatus for indicating multiple operating states of a battery charger providing a charging voltage across a positive output and a negative output is provided. Such apparatus may comprise a first color LED circuit having a first sense terminal and a common terminal; a second color LED circuit having a second sense terminal and a common terminal coupled to the common terminal of said first color LED circuit; a control circuit having a common terminal coupled to the common terminals of the first and second color LED circuits and having first and second charger terminals coupled in series with one of the positive and negative output terminals of the battery charger; wherein the first and second sense terminals of the respective first and second color LED circuits are coupled to the other one of the positive and negative output leads such that the coupling of the first and second LED circuits is operable to apply operating bias to the LED circuits. 
     In the preferred embodiment the first color LED circuit emits substantially red light upon activation and the second color LED circuit emits substantially green light. The light-emitting elements of the first and second color LED circuits may be disposed to emit light through a common diffusing lens so that simultaneous activation provides an appearance of a third color substantially distinct from the first and second colors. Operating bias may be applied to the first and second color LED circuits separately or in combination, continuously or alternately. Other features and advantages of the invention will become more readily understood from the following detailed description taken in connection with the appended claims and attached drawing in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a block diagram illustrating a status indicator for a battery charger in accordance with the invention; 
     FIG. 2 is a pictorial drawing of indicating elements useable with the status indicator of the embodiment in FIG. 1; and 
     FIG. 3 is a schematic diagram of a portion of a battery charger containing an embodiment of the status indicator of the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Throughout the several views of the drawing like numerals are used to indicate like parts. The drawing figures are not to scale but are intended to disclose the inventive concepts by illustration and are incorporated herein to illustrate presently preferred embodiments of the invention. The drawing should not be construed as limiting the invention to the illustrated and described embodiments. 
     FIG. 1 is a block diagram of a status indicator for a battery charger according to the present invention. Battery charger  100  is shown having a positive output terminal  102  and a negative output terminal  104 . Coupled to output terminal  102  is an output lead  106  and coupled to output terminal  104  is an output lead  108 . Output leads  106  and  108  provide for coupling to a status indicator  110  and further to a battery  120  to be charged by battery charger  100 . Output lead  106  includes a node  112  for connection of certain portions of status indicator  110 . A portion of status indicator  110  (a control circuit  114 ) is connected in series with the output lead  108  which connects to control circuit  114  at a first terminal  116  and continues from control circuit  114  at a second terminal  118  along output lead  122  to the negative terminal of the battery  120 . Output lead  106  passes through node  112  and connects to the positive terminal of the battery  120 . 
     An indicator circuit A  124  is coupled between node  112  and a common node  128 . Node  112  is coupled to indicator circuit A by a first sense lead  126 . Similarly, an indicator circuit B  130  is coupled between node  112  and common node  128  wherein the node  112  is coupled by a second sense lead  132  to indicator circuit B  130 . The common node  128  is coupled to control circuit  114  at a common terminal  134 . Operating voltage V CC  for control circuit  114  is supplied along a lead to terminal  136  on control circuit  114 . A third terminal  138  on control circuit  114  receives a sample of the battery voltage of the battery  120  from node  112  along path  140  coupled to the third terminal  138 . Indicator circuit A  124  and indicator circuit B  130  may each include a light-emitting element and associated circuitry for controlling illumination of the light-emitting element in the respective indicator circuit. 
     In operation battery charger  100  provides a charging voltage across the positive output terminal  102  and the negative output terminal  104  to be applied for recharging battery  120 . The status indicator  110  coupled in output leads  106  and  108  (including lead  122 ) responds to the voltage and current applied to or present in battery  120  to develop control signals for indicating the particular status of the battery charging operation. 
     FIG. 2 is a pictorial drawing of a pair of light-emitting elements assembled adjacent each other and placed in close proximity to a translucent diffusing lens. The visible element  200  includes light-emitting element A  202  having a common lead  204  and a first lead  206 . Similarly, a light-emitting element B  208  includes a common lead  210  and a second lead  212 . Common leads  204  and  210  are connected together at common terminal  214 . Light-emitting elements  202  and  208  are placed in close proximity to each other and in close proximity to a translucent diffusing lens  216  which is typically placed on or very close to the light-emitting surfaces of the light-emitting elements  202  and  208 . Thus, whenever either light-emitting element is caused to emit light, the respective light indicating signal is visible through translucent diffusing lens  216 . 
     The translucent diffusing lens  216  acts to spread light emitted from the individual light-emitting elements  202  and/or  208 . In one embodiment light-emitting element  202  may, for example, be configured to emit red light when it is activated. Similarly, light-emitting element  208  may be configured to emit, for example, green light. The human eye perceives each of these colors when illuminated individually as the respective color of the light being emitted which corresponds to the wavelength of light emitted by the light-emitting element  202  or  208 . However, the perception of color by the human eye and brain is, at least in part, a subjective physiological and psychological response so that, in the case where the light-emitting elements  202  and  208  emit red light and green light respectively at the same time, the color perceived by the viewer will appear yellow. Thus, the structure illustrated in FIG. 2 permits the use of two light-emitting elements to be perceived as three different colors, depending upon the particular activation of the individual light-emitting elements  202  and  208 . It will be further appreciated that numerous combinations of indications are possible among the three colors merely by varying the kind of signals applied to the light-emitting elements, e.g., continuous or intermittent, alternating or simultaneous, etc. Moreover, the light-emitting elements may be caused to flash in code for indicating data of various kinds. 
     FIG. 3 is a schematic diagram of a portion of a battery charger which includes a circuit for operating the status indicating system of the present invention. The portion of the battery charger circuit illustrated in FIG. 3 includes the secondary side of the battery charging circuit  300 , including the isolation transformer  302  having a secondary winding  304 . One end of the secondary winding is coupled to node  306  and the other end of the secondary winding is coupled to node  308 . Connected to node  306  is a rectifier  310  shown with its anode connected to node  306  and its cathode connected to a node  312 . Also connected between node  306  and node  312  is the series combination of a capacitor  314  and a resistor  316 . Node  312  is connected through an electrolytic capacitor  318  to node  308  which is coupled to earth ground  320 . Also coupled to earth ground  320  at node  308  is a resistor  322 , the other end of which is coupled to a node  324 . Node  324  connects to the emitter of an NPN transistor which has its collector coupled to a node  334  to which is also connected the negative voltage output line  332  of the battery charger. Output line  332  (also labeled V out −) corresponds to the output line  122  in FIG. 1 shown connected to the negative terminal of battery  120 . 
     An output lead  326  is connected between node  312  and node  328  to which is also connected to a positive output lead  330  (also labeled V out +) for connecting the battery charger output to a battery to be recharged. Node  335  mentioned previously as being connected to the collector of NPN transistor  334  is further coupled through resistor  336  to node  340  which, in turn, is coupled through resistor  338  to the emitter terminal of NPN transistor  334 . Node  340  is also connected to the base of an NPN transistor  342  which has its emitter terminal connected to the emitter terminal of NPN transistor  334 . The collector terminal of NPN transistor  342  is also connected to the base terminal of NPN transistor  346 . The base terminal of NPN transistor  346  is connected to node  344  and therefrom through resistor  345  to node  372 . The emitter terminal of NPN transistor  346  is coupled through resistor  348  to the base terminal of NPN transistor  334 . The collector terminal of NPN transistor  346  is coupled to node  350  which is coupled through resistor  352  to node  328 . 
     An indicator assembly  354  is shown which, in the illustrative embodiment of FIG. 3, includes a red light-emitting diode (LED)  356  and a green light-emitting diode (LED)  358 . The cathodes of LED  356  and LED  358  are connected together internally to the indicator assembly and proceed along a common lead to node  350 . The anode of the green LED  358  is connected to the anode of a zener diode  360  and the cathode of zener diode  360  is connected to node  328 . The anode of red LED  356  is connected to the cathode of a rectifier  362  and the anode of rectifier  362  is connected to node  364 . In operation the red LED  356  or the green LED  358  are individually or simultaneously activated, depending upon the relative voltages present at the respective anode and cathode terminals of the LED elements to be described hereinbelow. 
     Node  306  is also connected through a rectifier  366  to a node  368  which is coupled to earth ground  320  through an electrolytic capacitor  370 . In the embodiment of FIG. 3, the anode of rectifier  366  is connected to node  306  and the cathode of rectifier  366  is connected to node  368 . This particular connection of rectifier  366  and the capacitor  370  provides an operating voltage for a portion of the status indicating circuit  300 . Node  368  is connected to the V cc  terminal of a control circuit  376 . The ground terminal of control circuit  376  is coupled to a node  378  which is connected to earth ground  320 . Control circuit  376  typically contains two operational amplifiers for sensing various voltage levels in the battery charging output circuit and generating control signals used in the feedback system of the battery charging circuit and also in the status indicator circuit  300 . A first operational amplifier (op amp) within control circuit  376  provides an output at node  364  which is connected to the cathode of a rectifier  386 . The anode of the rectifier  386  is connected to a node  384  which, in turn, is connected to the cathode of the light-emitting diode within an optocoupler  382 . When illuminated, optocoupler  382  is used to provide an isolated output signal coupled into the primary side of the battery charger circuit (not shown in FIG.  3 ). The anode of the light-emitting diode in optocoupler  382  is coupled to node  368  through resistor  380 . The positive input of the first op amp in control circuit  376  is connected internally to a 2.5 volt reference relative to ground and the 2.5 volt reference is also connected externally of control circuit  376  to node  372 . The negative input to the first op amp in control circuit  376  is coupled to node  392  which is, in turn, connected to the junction of resistor  395  and  397 . Also coupled from node  392  is a capacitor which is connected to node  364 . Resistor  397  is connected from node  392  to node  328  and resistor  395  is connected from node  392  to node  378 . The positive input of a second op amp in control circuit  376  is connected to node  393 . Node  393  is connected through resistor  398  to node  372  and node  393  is also connected through resistor  399  to node  378 . The output of the second op amp in control circuit  376  is connected to a node  390  which, in turn, is connected to the cathode of a rectifier  388 . The anode of rectifier  388  is connected to node  384 . The node  390  is also coupled to node  394  at the negative input of the second op amp and control circuit  376  through a capacitor  385 . Node  394  is also coupled through a resistor  396  to the node  324 . 
     In operation the outputs of first and second op amps in control circuit  376  are in the quiescent state providing a high logic potential. The respective rectifiers, rectifier  386  connected to node  364  and rectifier  388  connected to node  390 , are reversed biased when the outputs of the op amps in control circuit  376  are in a high logic state. The positive input of each of the first and second op amps in control circuit  376  is coupled to the internal 2.5 volt reference either directly in the case of the first op amp or through a resistive divider in the case of the positive input to the second op amp in control circuit  376 . The signal input to the first op amp of control circuit  376  at node  392  is sensitive to the output voltage of the battery charger as divided by the combination of resistor  395  and resistor  397  so that when the output voltage of the battery charger, which is also the terminal voltage of the battery being recharged relative to the negative terminal of the battery, exceeds the 2.5 volt reference at the positive terminal of the first op amp of control circuit  376 , then the op amp in control circuit  376  changes state and its output goes to a logic low which forces node  364  toward ground. This action forward biases rectifier  386  which is coupled between node  384  and  364  and causes the LED in optocoupler  382  to turn on and send a light pulse to the primary side of the battery charger circuit for the purpose of regulating the battery charger output voltage. Similarly, the second op amp in control circuit  376  is sensitive to the output current of the battery charger which is coupled to the negative input of the op amp through resistor  396  from node  324 . Node  324  is coupled to the negative side of the secondary winding of isolation transformer  302  through resistor  322 . The voltage across resistor  322  is proportional to the current supplied to the battery and this voltage at node  324  is sensed through resistor  396  to the negative terminal of the second op amp and control circuit  376 . When the voltage at node  394  representing the battery charger output current exceeds the reference voltage present at the positive input terminal of the second op amp in control circuit  376 , then the second op amp is caused to change states and its output goes to a logic low, forcing the voltage at node  390  to a low potential. This logic low present at node  390  thrusts forward bias rectifier  388  and supplies operating current to the light-emitting diode portion of optocoupler  382 , again sending a light pulse to the primary side of the battery charging circuit to participate in the regulation of the battery charger output. 
     Attention is drawn to the three NPN transistors (transistor  334 , transistor  342  and transistor  346 ) shown in FIG.  3 . Operating voltages for this control circuit for the status indicator are supplied from several sources. The collector voltage for NPN transistor  342  at node  344  is supplied through resistor  345  from node  372  which is coupled to the 2.5 volt reference in control circuit  376 . The collector voltage for transistor  346  is supplied through resistor  352  connected between the battery charger output at node  328  and node  350  at the collector of transistor  346 . The control circuit consisting of these three transistors ( 334 ,  342  and  346 ) is thus connected so that the transistors have operating voltages present whenever the battery charger is providing output voltage to a battery being recharged. The bias current for causing transistors  346  and  334  to conduct originates at node  372  through resistor  345 , the base emitter junction of transistor  346  and its emitter resistor  348 , and then through the base emitter junction of transistor  334  and therealong to node  324  and through resistor  322  to the earth ground at node  320 . Bias current for transistor  342  originates at the negative output terminal of the battery charger which is positive with respect to node  320  and there from node  334  flows through resistor  336  through the base emitter junction of transistor  342  to node  324 . The operating state of each transistor in the control circuit just described depends on the voltage and current conditions present at the battery being charged which conditions will cause the respective light-emitting elements within the status indicating assembly  354  to illuminate individually or together or continuously or alternatively as will be described hereinbelow. 
     As in illustrative example of the operation of the embodiment shown in FIG. 3, the status indicator of the present disclosure is summarized in Table 1. The operating conditions are defined as: 
     Output voltage: 
     (a) 13.5 VDC@ D.V. mode, I L =0A; or 
     (b) 7v˜13 V @ C.C. mode, I L ≈1.25A; 
     Full load: 13 VDC @ 1.25 A typically; and 
     Power ON and charger output on V-I curve. 
     where C.V.=constant voltage; C.C.=constant current; and 
     I L =load current (to battery being charged) 
     
       
         
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 V OUT   
                 I O   
                 Q 342   
                 Q 346   
                 Q 334   
                 Red 
                 Green 
                 Yellow 
               
               
                   
               
             
             
               
                 0 neg 
                 &gt;full load 
                 ON 
                 off 
                 off 
                 off 
                 off 
                 off 
               
               
                 &lt;3 V 
               
               
                 3 V- 
                 &gt;full load 
                 off 
                 ON 
                 ON 
                 ON/off* 
                 off 
                 off 
               
               
                 7 V 
                 &gt;&gt;full load 
                 off 
                 off 
                 ON 
               
               
                 7 V- 
                 full load 
                 ON 
                 ON 
                 ON 
                 ON 
                 off 
                 off 
               
               
                 13 V 
               
               
                 13 V- 
                 &lt;full load 
                 off 
                 ON 
                 ON 
                 ON 
                 ON 
                 ON 
               
               
                 13.5 V 
               
               
                 =13.5 V 
                 full load 
                 off 
                 ON 
                 ON 
                 off 
                 ON 
                 off 
               
               
                 &gt;13.5 V 
                 &gt;&gt;full load 
                 ON 
                 off 
                 off 
                 off 
                 off/ON* 
                 off 
               
               
                   
                 &gt;full load 
                 off 
                 ON 
                 ON 
                 off 
               
               
                   
               
               
                 *blinks  
               
             
          
         
       
     
     It will be apparent from the foregoing that the principles of the invention may be used to form battery chargers with status indicators which employ the principles of the invention. It is to be understood that even though numerous characteristics and advantages of the invention have been set forth in the foregoing description together with details of the structure and function of the illustrated embodiments, this disclosure is to be considered illustrative only. Various changes and modifications may be made in detail, especially in matters of shape, size, arrangement and combination of parts, without departing from the spirit and scope of the invention as defined by the appended claims.