Patent Publication Number: US-9425608-B2

Title: Overvoltage protection system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Field of the Invention 
     The present invention relates to electrical systems and related methods associated with internal combustion engines and, more particularly, to systems and methods for protecting against excessive voltages that may occur in such electrical systems. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines commonly have engine-driven alternators by which normal powered operation of the engine results in the generation of electricity that can be used both to charge a battery associated with the engine (e.g., the battery relied upon to start the engine) and also to power various electrical devices. 
     Notwithstanding the ubiquity of such engines equipped with alternators and the efficacy of using alternators in such engines, various problems continue to exist with the usage of such alternators. In particular, there can occur excessive voltage conditions or overvoltage transients that occur during operation of alternators, for example, due to transient conditions associated with alternator operation or arising from external sources (that is, sources other than the engines on which the alternators are operating). When such excessive voltage conditions occur, the excessive voltages that are applied to the battery and/or other electrical system components of the engine can disrupt operation of those devices and/or damage those devices. Indeed, adverse conditions such as an open line on a battery or due to improper grounding can provide alternator voltage to be applied directly to all existing electrical and electronic components connected to the shared power line. Such conditions can potentially lead to electrical damage as alternator voltage pulses provide a high repetitive energy not readily handled by other protection devices. 
     Although various techniques have been developed to minimize or eliminate the negative effects associated with such excessive voltage conditions, such existing techniques have corresponding disadvantages. In particular, shunting of charging current from alternator and shorting alternator terminals have been used to achieve over voltage protection and voltage regulation. Yet shorting out one or more stator windings of an alternator to achieve voltage regulation or to protect an electrical system from overvoltage conditions has several disadvantages. Alternator windings can overheat due to the short circuit conditions, since under those operational conditions large amounts of current flow through the alternator windings can occur. Voltage regulation using the shunting principle takes out the excess alternator current to common ground which may cause over heating of electronic components, and can necessitate a redesign to handle the additional load and heating. Another disadvantage is that the AC signal from the alternator can be lost during this regulation process due to shorting of the alternator terminals. In many applications alternator AC signal provides energy to loads like headlights, hand warmers and works as source of pulse for a tachometer circuit, and thus the loss of the AC signal from the alternator can preclude or limit desired operation of such electrical devices. 
     For at least these reasons, therefore, it would be advantageous if an improved system (or apparatus or device) and/or method for providing overvoltage protection with respect to batteries and/or other electrical components associated with engines having engine-driven alternators could be developed that avoided one or more of the disadvantages associated with conventional systems and methods such as those mentioned above and/or provided one or more other benefits. 
     BRIEF SUMMARY OF THE INVENTION 
     In at least some embodiments, the present invention relates to a smart battery charging system that uses an engine driven alternator to provide charging current to a battery (e.g., a 12 volt battery or also possibly for example a 6 volt or 24 volt battery) in a controlled format. The system provides overvoltage protection for any device connected to the battery power line from the alternator signal when set limits are exceeded. Additionally, the design provides a unique timed automatic reset of the system based on the latest signal information which allows for the charging operation to resume once the transient signal is no longer active. 
     Further, in at least some embodiments, the system includes an overvoltage protection circuit that protects any electrical or electronic components connected to the battery power line or the charging system by shutting OFF the charging signal and isolating the alternator completely from the system in the event of a defined over voltage condition. The circuit automatically resets to resume charging operation after a predetermined time delay while continuously monitoring for any overvoltage event. In at least some such embodiments, the overvoltage protection system is incorporated on rectifier regulator designs along with diagnostics indicators. Also, in at least some embodiments, the overvoltage protection system can be easily incorporated in relation to rectifier-regulators using either a half or full wave rectification configuration. 
     Additionally, in at least some embodiments, an electrical system for use with an alternator system that supplies electrical power includes a first circuit portion configured to govern whether the electrical power is communicated from the alternator system to a terminal associated with one or both of a battery and a load, and a second circuit portion configured to determine whether a voltage is elevated above a predetermined threshold and to provide a first signal upon determining that the voltage is elevated above the predetermined threshold, where the voltage is either a first voltage at the terminal or a second voltage based at least indirectly upon the first voltage. The electrical system also includes a third circuit portion coupled at least indirectly to each of the first and second circuit portions, where the third circuit portion is configured to provide a second signal for receipt by the first circuit portion upon receiving the first signal from the second circuit portion, and where the second signal is additionally configured to cause the first circuit portion to cease allowing communication of the electrical power to the terminal. 
     Further, in at least some embodiments, a method of operating an electrical system of an engine having an alternator system that is configured to supply alternating current (AC) power to a remainder of the electrical system includes rectifying the AC power supplied by the alternator system and communicating the rectified AC power to a terminal at which are coupled one or both of a battery and a load. The method additionally includes experiencing an overvoltage event at which a first voltage exceeds a threshold, where the first voltage is either a terminal voltage at the terminal or an other voltage based at least indirectly upon the terminal voltage, and causing the communicating of the rectified AC power to the terminal to cease, at least partly in response to the experiencing of the overvoltage event. The method also includes delaying a reestablishment of the communicating of the rectified AC power to the terminal until at least a predetermined time period has elapsed since the overvoltage event. 
     Additionally, in at least some embodiments, an internal combustion engine includes an alternator system that is configured to generate alternating current (AC) power during operation of the engine, and a terminal to which is coupled one or both of a battery and a load. The internal combustion engine further includes an electrical system including means for temporarily decoupling the terminal from the alternator system so as to prevent further supplying of the AC power from the alternator system to the terminal when an overvoltage event is experienced and for at least a predetermined time period subsequent to the overvoltage event. 
     Many other aspects and embodiments are also contemplated and considered within the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are disclosed with reference to the accompanying drawings. It should be understood that the embodiments shown in the drawings arc provided for illustrative purposes only, and that the present invention is not limited in its application or scope to the details of construction or the arrangements of components particularly illustrated in these drawings. 
         FIG. 1  is a schematic diagram showing a portion of an internal combustion engine including an alternator system with a stator and rotor (shown partially in cross-section), and further showing in phantom additional electrical components that in at least the present embodiment include a battery and a load as well as additional circuitry that can include rectification and overvoltage protection circuitry; 
         FIG. 2  is an electrical schematic diagram showing in more detail the alternator system and also the additional electrical components including the battery, load, and additional circuitry of  FIG. 1 ; 
         FIG. 3  is a further schematic diagram illustrating in a conceptual manner various subportions of the additional circuitry as well as the alternator system, battery, and load of  FIGS. 1 and 2  and illustrating how those components interact with one another; 
         FIGS. 4 and 5  are additional electronic schematic diagrams identical to those of  FIG. 2  except insofar certain portions of the additional circuitry corresponding to certain of the subportions shown in  FIG. 3  are highlighted; 
         FIG. 6  is a flow chart illustrating example steps of operation of the additional circuitry of  FIGS. 1-5  in relation to the alternator system, battery, and/or load; and 
         FIGS. 7-9  are timing diagrams further illustrating manners of operation of the additional circuitry of  FIGS. 1-5  in relation to the alternator system, battery, and/or load. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring particularly to  FIG. 1 , an internal combustion engine  10  rotates a shaft  12  that can be coupled to rotate one or more wheels, to operate an implement such as a mower blade or the like (not shown in the drawings), or to deliver rotational power to other components and/or for other purposes. A flywheel  14  mounts to the shaft  12 , and as shown the flywheel supports a ring of permanent magnets  16  that encircle the shaft  12  and face radially inward. Additionally, a stator assembly  18  is mounted to the engine  10  and is positioned in the same plane as the magnets  16 . In the present embodiment, the stator assembly  18  includes eighteen separate coils  20  that are disposed in a circle around the shaft  12  and spaced equidistantly apart. The coils  20  are connected in series and form a single stator winding. The coils  20  of the stator assembly  18  can also be formed so as to surround or wrap around laminations (e.g., E-shaped laminations) that form a core (or multiple core portions) of the stator assembly. 
     When the engine  10  is operating, the shaft  12  rotates the magnets  16  around the stationary stator assembly  18 . An AC current is induced in the stator winding by its interaction with the changing magnetic field produced by the rotating magnets. As is well known in the art, this same interaction which generates the current in the stator winding also produces a torque on the shaft  12  which opposes its rotary motion. The greater the generated current, the greater this opposing torque. Current (and voltage) generated by relative motion of the coils  20  of the stator assembly  18  relative to the magnets  16  can be output by way of one or more (typically two or more) output lines  26 ,  28  and provided to one or more additional electrical components  30  as described in further detail with respect to  FIGS. 2-5 . The combination of the stator assembly  18  with the coils  20  and the permanent magnets  16  (as well as the output lines  26  and  28 ) can be considered to be an engine-driven alternator system  22 . 
     Notwithstanding the above description, the present invention is intended to encompass numerous variations of engine-driven alternator systems, engines, and engine components. For example, in some other embodiments, the alternator system is arranged such that the coils of the stator assembly are mounted concentrically around the magnets, which are positioned along an outer rim of the flywheel or another rotating engine component. Also for example, in some embodiments, the engine  10  (or other engines compassed herein) can be an engine from the Courage family of vertical and/or horizontal crankshaft engines available from the Kohler Company of Kohler, Wis. Also, in at least some embodiments, the engine  10  can be any of a variety of SORE engines including Class 1 and Class 2 small off-road engines (SORE) such as those implemented in various machinery and vehicles, including, for example, lawn movers, air compressors, and the like. 
     Indeed, in at least some such embodiments, the engine(s) can be “non-road engines” as defined in 40 C.F.R. §90.3, which states in pertinent part as follows: “Non-road engine means . . . any internal combustion engine: (i) in or on a piece of equipment that is self-propelled or serves a dual purpose by both propelling itself and performing another function (such as garden tractors, off-highway mobile cranes, and bulldozers); or (ii) in or on a piece of equipment that is intended to be propelled while performing its function (such as lawnmowers and string trimmers); or (iii) that, by itself or in or on a piece of equipment, is portable or transportable, meaning designed to be and capable of being carried or moved from one location to another. Indicia of transportability include, hut are not limited to, wheels, skids, carrying handles, dolly, trailer, or platform.” 
     Turning to  FIG. 2 , an electrical schematic diagram shows components of an example electrical system  40  associated with the engine  10  (and/or a vehicle or other machine with which the engine itself is associated). The electrical system  40  includes each of the alternator system  22  of the engine and the additional electrical components  30  associated with the engine. More particularly, in the present embodiment, the additional electrical components  30  include each of a battery  60  associated with the engine, a load  62  also associated with the engine, and additional circuitry  50 . As discussed in further detail below with respect to  FIGS. 3-5 , the additional circuitry  50  includes portions that serve as a rectifier regulator section as well as an overvoltage protection section, among other things. 
     As shown, the additional circuitry  50  is connected to the stator assembly  18  of the alternator system  22  at first and second AC terminals  52  and  54  of the electrical system  40  (the terminals themselves can be considered part of the additional circuitry  50 ). Further as shown, the additional circuitry  50  is additionally coupled, by way of a B+ line or battery terminal  56  (which also can be considered part of the additional circuitry  50 ) that is linked to the second AC terminal  54  by way of a fuse F 1 , to the battery  60  and the load  62 . As shown, in the present embodiment the battery  60  and the load  62  are coupled in parallel with one another between the battery terminal  56  and ground (represented by ground or triangle symbol). The battery  60  can be for example a 12 Volt DC battery or alternatively a 6 Volt DC or 24 Volt DC battery that is employed to power a starter (not shown) of the engine  10 . The load  62  is intended to be representative of any one or more of a variety of electrical components associated with the engine  10  and/or possibly a vehicle or other system of which the engine is a part (or is otherwise associated) that are powered by one or both of the battery  60  and the alternator system  22 . From  FIG. 2 , it should be apparent that the battery  60  and load  62  are coupled to, and receive power from, the alternator system  22  by way of the additional circuitry  50 . 
     Referring to  FIG. 3 , the electrical system  40 , including the battery  60 , load  62  and alternating system  22  (including the starter assembly  18 ) constituting the AC source of power for the system  40  is shown in a schematic manner to highlight particular sub-portions of the additional circuitry  50  and their functional interrelationships relative to one another and relative to the battery, load, and alternating system. Example electrical components corresponding to the sub-portions of the additional circuitry  50  are then further shown in more detail and described with respect to  FIGS. 4 and 5 . 
     As shown in  FIG. 3 , the additional circuitry  50  includes six functional sub-portions or functional units namely, first, second, third, fourth, fifth, and sixth functional units  102 ,  104 ,  106 ,  152 ,  154 , and  156 , respectively. In the present embodiment, the first functional unit  102  more particularly is a controlled rectifier unit that governs current (and thus power) flow between the alternator system  22  and one or both of the battery  60  and load  62  that are coupled in parallel with one another. Power flow from the alternator system  22  to the controlled rectifier unit or first functional unit  102  is represented by an arrow  72 , while power flow from the first functional unit to the battery  60  and load  62  is represented by an arrow  74 . Operation of the first functional unit  102  is governed by other sub-portions of the additional circuitry  50  as will be described in further detail below and as is represented by a dashed arrow  70 . 
     Further as illustrated, when power is being provided to the battery  60  and the load  62  by way of the first functional unit  102 , the sixth functional unit  156 , which is a charge indicator unit, provides an output signal that is indicative of the charging or power flow that is occurring. In the present environment, the sixth functional unit  156  particularly employs a light emitting diode (LED) for this purpose. However, in other embodiments, other types of indicators can be utilized including, for example, an acoustic indicator such as a beeping device (beeping could occur either charging is occurring or when the charging is not occurring). 
     Additionally in the present embodiment, during operation, the voltage at the battery terminal  56  (V b ) shown in  FIG. 2  is monitored by each of the second functional unit  104 , which operates as a voltage comparator and switch unit, and the fourth functional unit  152 , which serves as an overvoltage shutdown unit. This monitoring is represented in  FIG. 3  by a double-headed arrow  78  extending from the battery  60 /load  62  to each of the second functional unit  104  and the overvoltage shutdown unit  152 . Further, as represented by an arrow  84 , operation of the second functional unit  104  can control or influence operation of the third functional unit  106 , which is a gate trigger and filter unit. More particularly, as will be discussed further below, depending upon whether the voltage (V b ) at the battery terminal  56  is higher or lower (e.g., whether it is above or below a particular threshold), a signal or signals represented by the arrow  84  are generated by the second functional unit  104  that in turn affect operation of the third functional unit  106 . 
     More particularly, the signal(s) generated by the second functional unit  104  cause (or are configured to cause) the third functional unit  106  to operate in a manner so as to itself provide or not provide an appropriate signal or signals to the first functional unit  102  (and particularly to a silicon-controlled rectifier or SCR thereof) as represented by the dashed arrow  70 . Those signal(s) represented by the dashed arrow  70  and provided to the first functional unit  102  particularly cause, or are configured to cause, the first functional unit to turn ON, stay ON, turn OFF, or stay OFF such that power begins or continues to flow between the alternate system  22  and the battery  60 /load  62 , or ceases to flow or continues not to flow. Additionally as indicated, the third functional unit  106  also includes a filter portion to filter out noise and the like as described further below. 
     As already mentioned, the fourth functional unit  152  also monitors the voltage level of the battery  60 /load  62  (also constituting the battery terminal  56  (V b )) as represented by the double-headed arrow  78 . More particularly in this regard, the fourth functional unit (overvoltage shutdown unit)  152  determines based upon the battery terminal  56  (V b )) whether or not an overvoltage condition has occurred. As represented by the arrow  80 , if the fourth functional unit  152  determines that an overvoltage condition has occurred, the fourth functional unit sends signal(s) to the second functional unit  104  that cause portions of the additional circuitry  50  to shut down. More particularly in this regard, upon receiving such signals(s), the second functional unit  104  can again generate signal(s) that are provided to the third functional unit  106  that in turn provides signal(s) to the first functional unit  102  that are configured to cause the communication of power between the alternator system  22  and the battery  60 /load  62  to cease. 
     Further as represented by an arrow  82 , the overvoltage shutdown unit constituting the fourth functional unit  152  is also in communication with the fifth functional unit  154  that serves as an overvoltage indicator unit. When the fourth functional unit  152  detects that an overvoltage condition has occurred resulting in system shut down, the fourth functional unit  152  additionally sends signal(s) to the fifth functional unit  154  that cause the fifth functional unit to provide an output signal indicative of that fact. As with the sixth functional unit  156 , the fifth functional unit  154  in the present embodiment employs a light emitting diode (LED) although in other embodiments other indicators can be used. Finally, as will be discussed in further detail below, in the present embodiment the fourth functional unit  152  not only detects overvoltage conditions and provides signal(s) in response thereto, but also includes a time delay function according to which the fourth functional unit  152  itself determines whether sufficient time has elapsed subsequent to the occurrence of an overvoltage event, and does not provide signals to the second functional unit  104  or the fifth functional unit  154  that precipitate a resumption of normal operation until after that time has elapsed. Once sufficient time elapses, however, signals are provided to each of the second functional unit  104  and the fifth functional unit  154 , as again represented by the arrows  80  and  82 , respectively, to resume normal operation. 
     Referring additionally to  FIGS. 4 and 5 , respectively, the electrical system  40  is again shown with certain sub-portions of the additional circuitry  50  highlighted in each case that correspond to different ones of the functional units  102 ,  104 ,  106 ,  152 ,  154 , and  156  already discussed above in relation to  FIG. 3 .  FIG. 4  particularly highlights circuit components of the additional circuitry  50  that correspond to the first, second, and third functional units  102 ,  104 , and  106 , respectively, and that together with the sixth functional unit  156  of  FIG. 5  serve overall as a rectifier regulator portion  100  of the additional circuitry  50 , while  FIG. 5  particularly highlights circuit components of the additional circuitry  50  that correspond to the fourth and fifth functional units  152  and  154 , respectively, and that serve overall as an overvoltage protection portion  150  of the additional circuitry  50  (again, the sixth functional unit  156  of  FIG. 5  is more properly considered part of the rectifier regulator portion  100 ). 
     Referring then more particularly to  FIG. 4 , the first functional unit  102  includes a silicon-controlled rectifier (SCR) T 1  that serves to provide a link between the alternator system  22  (that is, the engine-driven alternator with multi-pole stator assembly  18  and permanent magnet based flywheel) and the battery  60  and the load  62  by which power can be delivered from the alternator system  22  the battery and/or load. As shown, in the present embodiment the anode (or anode pin) of the SCR T 1  connects to ground while the cathode (or cathode pin) connects to the first AC terminal  52  that is coupled to one side of the stator assembly  18 . Also as shown, the other side of the stator assembly  18  is coupled to the second AC terminal  54  that in turn is connected directly to the battery terminal  56  via the fuse F 1 , where the battery  60  and load  62  are both coupled between the battery terminal and ground. The gate of the SCR T 1  is controlled by the third functional unit  106  that in turn is controlled by the second functional unit  104 . More particularly, the gate of the SCR T 1  is triggered by current as provided by the third functional unit  106 . By virtue of this control, the SCR T 1  is conductive during one half or phase of the stator AC signal and at such time (absent an overvoltage condition) serves to charge the battery  60  by passing current through it. Although in the present embodiment the functional units  106 ,  104 , and  102  (with the SCR T 1 ) provide a half-wave rectifier regulator circuit, in other embodiments this circuitry can be modified to operate as another type of rectifier regulator (e.g., a full-wave rectifier regulator). 
     Also as shown in  FIG. 4 , the second functional unit  104  includes a comparator in the form of a first bipolar junction transistor that in this case is a PNP transistor Q 1 , a voltage divider  108  including a first resistor R 1  and a second resistor R 2 , a first diode D 1  that is a reference Zener diode, and a third resistor R 3 . As shown, the third resistor R 3  is connected between the collector of the PNP transistor Q 1  and the second resistor R 2 , the second resistor is connected between the third resistor R 3  and the base of the PNP transistor Q 1 , the junction between the second and third resistors R 2  and R 3  is also coupled to ground, the first resistor R 1  is connected between the base of the PNP transistor Q 1  (and thus the second resistor R 2 ) and battery terminal  56 , and the first (Zener) diode D 1  is connected between the emitter of the PNP transistor Q 1  and the battery terminal as well, with the cathode of the first diode D 1  particularly being coupled to the battery terminal and the anode of that diode being coupled to the emitter of the PNP transistor Q 1 . Thus, the voltage at the battery terminal  56  (V b ) is sensed and compared to a reference voltage (set by the Zener diode D 1 ), which turns the PNP transistor Q 1  ON and OFF based on the charge level (change in voltage) at the battery  60 . 
     The PNP transistor Q 1  at the same time controls the third functional unit  106 . As shown, the third functional unit  106  includes second and third diodes D 2  and D 3 , respectively, a second bipolar junction transistor that is a PNP transistor Q 2 , a third bipolar junction transistor that is a NPN transistor Q 3 , a capacitor C 2 , and fourth, fifth, and sixth resistors R 4 , R 5 , and R 6 , respectively. More particularly, the emitter of the PNP transistor Q 2  of the third functional unit  106  is coupled to the emitter of the PNP transistor Q 1  of the second functional unit  104  (and thus also to the Zener diode D 1 ), and also coupled to the cathode of the second diode D 2 . The anode of the second diode D 2  is coupled to each of the base of the PNP transistor Q 2 , the collector of the NPN transistor Q 3 , and the collector of the PNP transistor Q 1  of the second functional unit  104  (and thus also to the third resistor R 3 ). Further, the fourth resistor R 4  in turn is coupled between, at one of its end terminals, each of the base of the NPN transistor Q 3  and the collector of the PNP transistor Q 2  and, at its other end terminal, each of the emitter of the NPN transistor  3  and one end of the fifth resistor R 5 , the other end of which is coupled to the anode of the third diode D 3 . Additionally, each of the capacitor C 2  and the sixth resistor R 6  are coupled in parallel with one another between the first AC terminal  52  and the cathode of the third diode D 3 , which also is coupled to the gate of the SCR T 1  of the first functional unit  102 . 
     Given this design, the third functional unit  106  includes not only transistors but also a current control resistor as well as a noise filter unit. More particularly, when the PNP transistor Q 1  of the second functional unit  104  is ON, current triggers the base of the PNP transistor Q 2 , which then turns it ON, thereby triggering the base of the NPN transistor Q 3 . When this occurs, the third functional unit  106  provides sufficient trigger current necessary to trigger the gate of the SCR T 1 . The combination of the sixth resistor R 6  and capacitor C 2  additionally provides immunity from high frequency noise, thereby preventing any undesired triggering of the SCR T 1 . Thus, the third functional unit  106  creates a thyristor equivalent gate trigger circuit for the SCR T 1  along with a low pass filter unit. In this regard, the third functional unit  106  is advantageous relative to at least some other conventional designs for SCR gate trigger circuits, as it provides biasing of the gate of the SCR T 1  using a RC filter (e.g., the sixth resistor R 6  and capacitor C 2 ) to provide immunity from high frequency noise and reduces turn-off time. This feature also provides the ability to choose trigger frequency and adjust the level of gate sensitivity. 
     Referring now more particularly to  FIG. 5 , the sixth functional unit  156  includes simply the series combination of a ninth diode D 9 , a light emitting diode (LED)  158 , and an eleventh resistor R 11 , where the resistor is coupled in series between the anode of the LED and the cathode of the diode D 9 , the cathode of the LED is coupled to the first AC terminal  52  (and thus to each of the capacitor C 2 , the resistor R 6 , and the cathode of the SCR T 1 ), and the anode of the diode D 9  is coupled to the emitter of the NPN transistor Q 3  of the third functional unit  106  (and thus also to the fourth resistor R 4  and the fifth resistor R 5  of that functional unit). With this configuration, the sixth functional unit  156  serves as a charging indicator that can constitute part of an overall (engine) diagnostics system. More particularly, in the present embodiment, the LED  158  glows continuously when normal battery charging operation is occurring. That is, when the PNP transistor Q 1  is ON, it activates the third functional unit  106 , which in turn triggers conduction by the SCR T 1  and thus allows for power to be supplied, to the battery  60 . When this occurs, the sixth functional unit  156  (normal charging indicator) also gets current from the NPN transistor Q 3 , which completes the circuit to ground via the SCR T 1 . The ninth diode D 9  additionally prevents the additional circuitry  50  from encountering reverse battery polarity connections and the eleventh resistor R 11  limits the current in the circuit as required by the LED  158 . In short, when the battery  60  receives charge current when the SCR T 1  turns ON during the positive half of the AC signal from the alternator system  22 , the circuit for the LED  158  is completed via the SCR T 1  activation. 
     Further referring to  FIG. 4 , the fourth functional unit  152  provides an overvoltage protection circuit/overvoltage shutdown unit that shuts OFF the charging operation of the rectifier regulator (formed by the first, second, and third functional units  102 ,  104 , and  106 ) in the event of any overvoltage condition including, for example, an adverse condition such as a battery disconnect, an alternator or engine malfunction, or an external load switching condition that is placed on the associated system (e.g., on the load  62 ). Additionally, the particular overvoltage protection circuit in the present embodiment provided by the fourth functional unit  152  not only affords overvoltage protection as mentioned above, but also affords an automatic reset to resume the charging operation with respect to the battery  60  after a predetermined time delay, while continuously monitoring for any (additional) overvoltage event or events. 
     More particularly as shown in  FIG. 4 , the fourth functional unit  152  includes two additional Zener diodes shown as a fourth diode D 4  and a sixth diode D 6 , an additional general rectifier diode, namely, a fifth diode D 5 , three additional resistors shown as a seventh resistor R 7 , an eighth resistor R 8 , and a ninth resistor R 9 , a capacitor C 1 , and a N-Channel MOSFET Q 4 . The N-Channel MOSFET Q 4  in the present embodiment is a voltage-controlled device rather than a current-controlled device, although current-controlled devices can be employed in alternate embodiments. Further as shown, each of the sixth diode D 6 , the eighth resistor R 8 , and the capacitor C 1  are coupled in parallel between ground (shown as a ground terminal) and a gate of the N-Channel MOSFET Q 4 , with more specifically it being the anode of the sixth diode D 6  that is coupled to ground (the cathode being coupled to the gate of the N-Channel MOSFET). 
     Also as illustrated, a source of the N-Channel MOSFET Q 4  is further coupled directly to ground (as is the anode of the SCR T 1  and the junction between the second and third resistors R 2  and R 3  of the second functional unit  104 ). Additionally, the seventh resistor R 7 , the fifth diode D 5 , and the fourth diode D 4  are all coupled in series between the gate of the N-Channel MOSFET Q 4  and the battery terminal  56 , with the resistor R 7  being coupled between the gate of the N-Channel MOSFET Q 4  and the cathode of a fifth diode D 5 , the anode of the diode D 5  being coupled to the anode of the (Zener) diode D 4 , and the cathode of the diode D 4  being coupled to the battery terminal  56 . Further, the resistor R 9  of the fourth functional unit  152  is coupled between a drain of the N-Channel MOSFET Q 4  and the cathode of a seventh diode D 7  (which is shown as part of the fifth functional unit  154  even though it could be alternatively considered part of the fourth functional unit  152 ), the anode of which is coupled to the base of the PNP transistor Q 1  (as well as to the first and second resistors R 1  and R 2 ). 
     Given this configuration, when an overvoltage event occurs, as identified when the signal voltage amplitude exceeds the voltage reference set by the fourth (Zener) diode D 4  (again, for example, due to adverse conditions caused by inductive load switching or an open battery condition), then the fourth diode D 4  goes into conduction mode and triggers the gate of the N-Channel MOSFET Q 4  which turns it in ON state. The N-Channel MOSFET Q 4  then provides a ground path to the base of the PNP transistor Q 1  through the seventh diode D 7  and the ninth resistor R 9 , thereby turning OFF the PNP transistor Q 1  (which can be viewed as the “main” transistor of the additional circuitry  50 ). This removes the battery charging operation as provided from the rectified alternator signal, which is shut down. More particularly, when an overvoltage condition occurs, the fourth functional unit  152  disables the second functional unit  104  (particularly the PNP transistor Q 1  thereof) and, due to the switching OFF of the PNP transistor Q 1 , no current flows through the third functional unit  106  that can trigger the SCR gate and this effectively causes triggering OFF of the SCR T 1 . Thus, the current path from the first AC terminal  52  to the battery terminal  56  via the SCR T 1 , the third resistor R 3 , and the PNP transistor Q 1  is broken, which switches the alternator system  22  (and particularly the stator assembly  18 ) out of the system to an electrically isolated condition. 
     Also when an overvoltage condition occurs, a portion of the overvoltage pulse is used to charge the capacitor C 1  through the seventh resistor R 7 . The voltage experienced across the capacitor C 1  not only turns ON the N-Channel MOSFET Q 4  but also keeps the N-Channel MOSFET Q 4  in the ON state until the capacitor C 1  discharges through the eighth resistor R 8 . Given proper selection of the resistance of the eighth resistor R 8  and the capacitance of the capacitor C 1 , a high time constant value can be achieved for slow discharge. By virtue of such operation, the N-Channel MOSFET Q 4  can be kept ON based on the chosen values of the capacitance of the capacitor C 1  and resistance of the eighth resistor R 8 , that is, a RESET time during which the N-Channel MOSFET Q 4  is kept ON prior to switching OFF can be adjusted to a pre-determined value as needed. 
     With respect to selecting the respective resistance and capacitance values of the eighth resistor R 8  and the capacitor C 1 , charging and discharging of capacitor are exponential processes, Equation (1) as follows represents capacitor charging:
 
 V   1   C ( t )=[ V   1   C (0)− V   1 IN]*[ e   (−t/RC ) ]+V   1 IN  (1)
 
where V 1 C(t)=capacitor voltage at any given time “t”, V 1 C(0)=capacitor voltage at “t=0”, and V 1 IN=applied input voltage (e.g., battery voltage). Given this equation, the rate of charge of the capacitor depends on the product of the resistance R of the resistor governing charging (in this case, the resistance of the resistor R 7 ) and the capacitance of the capacitor being charged (in this case, the capacitance of the capacitor C 1 ). This product is also referred as time constant which is usually denoted by the Greek letter “τ”, where the unit of time of the time constant τ is seconds. According to equation (1), it takes about 2*τ seconds to charge the capacitor about 95% of the applied input voltage. So for faster charging of capacitor C 1 , the resistance of the resistor R 7  should be chosen small.
 
     As for discharging, equation (2) represents the capacitor discharging process (assuming that the capacitor discharges completely, where the final capacitor voltage after discharge=0V):
 
 V   1   C ( t )= V   1   C (0)* e   (−t/RC)   (2)
 
where V 1 C(t)=capacitor voltage at any given time “t”, and V 1 C(0)=capacitor voltage at “t=0”. As with the charging of the capacitor discussed above, the rate of discharge of the capacitor also depends on the product of the capacitance of that capacitor (again, in this case, the capacitance C 1 ), but also the resistance of the resistor through which discharging occurs. In this case, the particular resistance involved is not the resistance of the resistor R 7  but rather is the resistance of the resistor R 8  by which discharging occurs. It should be noted that, by setting the resistance value of the resistor R 7  to be much less than the resistance value of the resistor R 8  (R 7 &lt;&lt;R 8 ), this allows for faster charging of the capacitor C 1  but slow discharging of that capacitor. Additionally, a RESET time can be controlled by controlling the product of R 8  and C 1 . Per the discharge equation (2), it takes about 3*τ seconds to discharge the capacitor C 1  to 5% of its fully-charged voltage value and so a larger value of τ can provide higher RESET delay time for the overvoltage circuit.
 
     Additionally for example, in this regard, assuming that the resistance value of resistor R 7  is chosen to be 100Ω and the capacitance value of the capacitor C 1  is chosen to be 10 μF, this will result in a time constant τ of 1 milliseconds (again where τ=R*C). So it may take about 2 ms for the capacitor C 1  to get charged up to 95% of the applied input voltage value. Alternatively, if we choose the resistance value of the resistor R 8  as 500 kΩand the capacitance value of the capacitor C 1  to be 10 μF, the resulting time constant τ will be 5 seconds (again where τ=R*C). So it may take about 15 seconds for the capacitor C 1  to get discharged to 5% of its fully charged voltage value. Further as presented in  FIG. 8 , total discharge time or predetermined reset delay would increase when multiple overvoltage events occur (e.g., as represented by spikes  264  and  270  shown in  FIG. 8  and discussed below). 
     Further as shown in  FIG. 5 , the fifth functional unit  154  includes two additional general rectifier diodes, namely, the seventh diode D 7  already mentioned above as well as an eighth diode D 8 , plus a tenth resistor R 10 , and an additional light emitting diode (LED)  160 , which like the LED  158  serves as an indicator light. As already mentioned, the anode of the seventh diode D 7  is coupled to the base of PNP transistor Q 1  (and thus also to the junction between the first and second resistors R 1  and R 2 ) of the second functional unit  104 , and the cathode of the seventh diode D 7  is coupled to the cathode of the eighth diode D 8  as well as the terminal of the ninth resistor R 9  that is opposite the terminal coupled to the drain of the N-Channel MOSFET Q 4 . Additionally, the tenth resistor R 10  is coupled between the anode of the eighth diode D 8  and the cathode of the LED  160 , the anode of which is coupled to the battery terminal  56 . 
     Given this arrangement, when the N-Channel MOSFET Q 4  is in the ON (conductive) state, then the current from the battery (via the battery terminal  56 ) is routed to ground via the LED  160  and the ninth resistor R 9  (as well as the tenth resistor R 10  and the eighth diode D 8 ). Thus, the combination of these circuit components serves as an overvoltage indicator unit. It should further be noted that the tenth resistor R 10  limits the current in the fifth functional unit  154  to power up the LED  160  only when the overvoltage circuit is active. Further, the eighth diode D 8  is incorporated to provide reverse polarity protection for the fifth functional unit  154 . 
     The combination of the overvoltage protection portion  150  of the additional circuitry  50  (formed particularly by the fourth and fifth functional units  152  and  154 ) including the LED  160 , along with the rectifier regulator portion  100  of the additional circuitry  50  (formed particularly by way of the first, second, third, and sixth functional units  102 ,  104 ,  106 , and  156 ) with the LED  158 , serves to provide diagnostic code outputs that can be read by an operator to determine whether the alternator/battery charging system is operating normally. In particular, Table 1 provides a summary of how different operational states of the LEDs  158  and  160  can be interpreted by an operator as indicative of a particular system status: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Diagnostic codes for rectifier regulator 
               
               
                 with overvoltage and charging indicators. 
               
            
           
           
               
               
               
            
               
                 LED1 
                 LED2 
                 Result 
               
               
                   
               
               
                 OFF 
                 ON 
                 Charging system working normally 
               
               
                 ON 
                 OFF 
                 Over voltage event occurred and charging operation 
               
               
                   
                   
                 is OFF 
               
               
                 OFF 
                 OFF 
                 Charging system is NOT working and in need of 
               
               
                   
                   
                 service. 
               
               
                 ON 
                 ON 
                 Charging system is faulty and in need of service. 
               
               
                   
               
            
           
         
       
     
     Turning to  FIG. 6 , a flowchart  200  further illustrates operation of the system  40  and particularly the additional circuitry  50  thereof. As shown, upon the system  50  entering operation at a start step  202 , first and second sub-processes  204  and  206 , respectively, are performed continually and simultaneously. The first sub-process  204  begins, following the start step  202 , at a step  208  in which the system  50  reads the voltage at the battery terminal  56  (or on the B+ line), namely, the battery voltage (V b ). Next, at a step  210 , the system determines whether the battery voltage (V b ) is greater than or equal to a charge set point. The operation of the steps  208  and  210  can be understood to be performed by the second functional unit  104 , which as already described provides a comparator in the form of the PNP transistor Q 1 , the voltage divider from the resistors R 1  and R 2 , and the first (Zener) diode D 1 , and Which senses the battery voltage and compares it to the reference set by the diode D 1  so as to govern the turning ON or OFF of the transistor Q 1 . Further as illustrated in  FIG. 6 , so long as the battery voltage (V b ) is greater than or equal to the voltage (battery charge) set point established, by the first diode D 1 , the process continually cycles back from the step  210  back to the step  208  and then back to the step  210 . 
     However, if it is determined at the step  210  that the battery voltage (V b ) is less than the voltage (battery charge) set point, then the process advances to a step  212 , at which the SCR T 1  is triggered to turn on by way of a trigger signal applied to the gate of the SCR, at which time the SCR then provides for (or allows provision of) charge current to the battery  60  vis-à-vis battery terminal  56 . This triggering of the SCR T 1 , of the first functional unit  102 , is performed particularly by way of the third functional unit  106  (operating as the thyristor gate trigger circuit or SCR gate control circuit). Further as illustrated, once the SCR T 1  is turned on so as to provide charge current to the battery  60 , then the process also performs a step  214  at which the charging indicator LED, that is, the LED  158  of the sixth functional unit  156 , is turned on so as to indicate that charging is taking place. The process then proceeds back to step  208  where battery voltage is again read. 
     As already noted, the sub-process  206  can occur concurrently with the sub-process  204 . The sub-process  206 , following the start step  202 , begins at a step  216 , at which the voltage at the battery terminal  56  (that is, the voltage on the line or the battery voltage (V b )) is monitored for an overvoltage condition. Subsequent to the step  216 , at a next step  218  the system determines whether the current value of the voltage at the battery terminal (V b ) is greater than or equal to an overvoltage set point as determined by the fourth (Zener) diode D 4 . Both of the steps  216  and  218  can be considered performed by the fourth functional unit  154  discussed above. If the voltage at the battery terminal  56  (again, the battery voltage (V b )) is not greater than or equal to the overvoltage set point, then the process returns to the step  216  and the steps  216  and  218  are repeated again and again. 
     However, if the voltage at the battery terminal  56  is determined at the step  218  to be greater than or equal to the overvoltage set point, then instead the process advances to a step  220 , at which the overvoltage control capability is activated and this ultimately results in the shutting OFF of the SCR, gate control circuit, the SCR T 1 . More particularly, as already described, once the fourth diode D 4  begins to conduct due to an overvoltage event, the N-Channel MOSFET Q 4  is triggered at its gate so as to enter the ON state. When this occurs, the N-Channel MOSFET Q 4  provides a ground path to the base of the first transistor Q 1 , which results in the turning OFF of that first transistor Q 1 . This in turn causes the third functional unit  106  (the SCR gate control circuit) to shut down any battery charging operation that might otherwise have (or previously) been occurring due to conduction by the SCR T 1 . Additionally at a step  222 , the overvoltage indicator LED (namely, the LED  160 ), is turned ON. Although this step is shown as being subsequent to the step  220 , it can be considered to occur simultaneous as the step  220 , occurring as soon as an overvoltage event occurs. 
     Further, as already discussed, the N-Channel MOSFET Q 4  upon being turned on can remain on for a period of time as determined by the RC circuit formed by the combination of a capacitor C 1  and the eighth resistor R 8 . Thus at a step  224  such a time delay is provided and the running of such time delay is started. It will be understood that, more particularly, the time delay starts once the overvoltage event has ended, after the charging of the capacitor C 1  has ceased. Further as already discussed, the time delay is predetermined and adjustable based on the selection of the values for the eighth resistor R 8  and capacitor C 1 . 
     Following the step  224 , as represented by steps  226  and  227 , the system continues to be in shut down mode due to the overvoltage event until the time delay is completed. More particularly, as long as the time delay is not over yet as determined at the step  226 , the system continues to further monitor for whether yet another overvoltage event has occurred, at a step  227  (more particularly, by detecting whether the battery voltage is again greater than or equal to the overvoltage set point as was already detected at the step  218 ). If during the time delay period an additional overvoltage event occurs, then the process returns to the step  224  and the time delay is restarted. In this respect, it should be noted also that the time delay that is set in response to each different overvoltage event can be different, based upon the amount of charging of the capacitor C 1  that results from that overvoltage event. Alternatively, further as shown in at the step  226 , it the time delay period expires and no further additional overvoltage event has occurred, then the process advances to a step  228  at which the overvoltage indicator LED is turned off, and then the sub-process  206  returns to the step  216 . 
     Finally it should also be noted as shown in  FIG. 6  that the first and second sub-process  204  and  206  are linked. More particularly as shown, regardless of whether the determination at the step  210  of the sub-process  204  is in the affirmative (that is, the voltage (V b ) is greater than or equal to the charge set point) or in the negative (the voltage (V b ) is less than the charge set point), this also further trigger the performing of the step  218  at which the voltage (V b ) is determined to be greater than or equal to or less than the over voltage set point. 
     Turning to  FIGS. 7 and 8  first and second timing diagrams  200  and  250  are shown, respectively. The timing diagram  200  of  FIG. 7  illustrates example signals that can be experienced by the system  40  (and the additional circuitry  50 ), particularly during operation when a single overvoltage event occurs. By comparison, the timing diagram  250  of  FIG. 8  shows example signals that can be experienced by the system  40  (and the additional circuitry  50 ) when multiple overvoltage events occur within relative rapidly succession such that the capacitor C 1  has not fully discharged before the occurrence of a subsequent overvoltage event (in this instance, two such events are shown to occur). It should be understood that the signals shown in the timing diagrams  200  and  250  are merely intended to highlight or exemplify some operations of the system  40 , but that the system  40  need not operate in accordance with these particular diagrams in any particular embodiment or at any particular circumstance. 
     With respect particularly to the timing diagram  200  of  FIG. 7 , in that timing diagram four curves. In the timing diagram  200 , changes in time are represented along the x axis while values of the various curves at different times are shown to vary along the y axis. A first curve  202  of the timing diagram  200  particularly shows example voltage values at the battery terminal  56  (the battery voltage (V b )) varying with time. The y axis of the timing diagram  200  particularly shows values of this voltage. In addition to the first curve  202 , the timing diagram  200  additionally includes a second curve  204  that is representative of the charging control circuit status in terms of being ON or OFF. That is, the second curve  204  particularly relates to the ON/OFF status of the PNP transistor Q of the second functional unit  104 , which governs operation of the third functional unit  106  and thus governs actuation of the SCR T 1  of the first functional unit  102 . A third curve  205  is representative of battery charging current that varies over time, that is, the current flowing through the SCR T 1 . Finally, a fourth curve  208  shows the voltage on (across) the capacitor C 1  of the fourth functional unit  152 . 
       FIG. 7  illustrates several operational characteristics of note. First,  FIG. 7  illustrates normal charging operation of the system  40  (and additional circuitry  50 ) as occurs in the absence of overvoltage events. As shown, when the second functional unit  104  is in the ON mode of operation as indicated by the second curve  204  between a first time  210  and a second time  212 , the battery voltage (V b ) represented by the first curve  202  increases steadily (or substantially steadily) up until a third time  214  (which in this example is about midway between the first and second times) at which the battery voltage attains a fully-charged level or set point (in this case, about 14.0 V+/−0.2 V). That is, the first curve  202  steadily increases in value while the second functional unit  104  is ON until the battery  60  is fully charged. However, during the time period between the third time  214  and the second time  212  when the second functional unit  104  remains on, during which the battery  60  is fully (or substantially fully) charged, as shown the battery voltage (V b ) does not increase but rather stays the same. That is, between the third and second times  214  and  212 , the first curve  202  remains at a constant (or substantially constant) value. 
     The third curve  205  illustrates the corresponding battery charging current that flows during the time period between the first time  210  and the third time  214  and also between the third time  214  and the second time  212 . As shown, between the first and third times  210  and  214 , respectively, the battery charging current repeatedly shuts on and shuts off as represented by a series of periodic half-wave sinusoidal pulses  206 , which correspond to positive (or alternatively negative) half cycles of the alternator system  22 . The half-wave sinusoidal pulses  206  are shown to occur regularly during this time period between the first and third times  210  and  214 , respectively, since during this time the battery  60  still needs to be charged to higher and higher voltages. However, following the third time  214  and up until the second time  212  at which the second functional unit  104  shuts OFF, the battery charging current is shown to encompass only a few pulses  207  that occur intermittently rather than regularly. This is because, during this period of time, the battery  60  is already fully (or substantially fully) charged and so further battery charge current only flows when the battery charge occasionally falls to a level slightly under its fully-charged level. Such operation, where battery charging current only occasionally flows in order to keep the battery  60  at its voltage set point, can be referred to as “trickle charging operation”. 
     The timing diagram  200  further illustrates example operation of the system  40  (and additional circuitry  50 ) when an overvoltage event occurs. In the example shown, an overvoltage event occurs as represented by a spike  216  in the first curve  202  between the second time  212  and a fourth time  218 . It is during this time period, between the second time  212  and the fourth time  218  that the fourth curve  208  experiences a significant rise as the capacitor C 1  is charged up based upon the overvoltage event that has occurred. In the present example, the fourth time  218  is the time at which the overvoltage event ceases to occur. Following the fourth time  218 , the capacitor C 1  then discharges through the eighth resistor R 8 , as further represented by the diminishing value of the fourth curve  208  between the time  218  and a fifth time  220 . The amount of time between the fourth time  218  and the fifth time  220  is directly proportional to the RC time constant established by the product of the resistance of the eighth resistor R 8  and the capacitance of the capacitor C 1 . While this is occurring, the second functional unit  104  serving as the charging control circuit (or comparator unit) remains OFF, as represented by the second curve  204 . Also during this time period between the fourth time  218  and the fifth time  220 , the battery voltage (V b ) at the battery terminal  56  remains constant or flat as indicated by the first curve  202 . More particularly, the battery voltage during this time period and as represented by the first curve  202  remains flat a level that is slightly lower than the voltage set point that existed prior to the occurrence of the spike  216 . This is because, after the voltage spike  216 , battery charging operation shuts down between the times  218  and  220  so the battery voltage drops down to a normally charged value of about 12.8 Volts. 
     Ultimately, the fifth time  220  is the time at which the capacitor C 1  is sufficiently discharged that the overvoltage shutdown is ended and thus, as shown, at the fifth time  220  the second functional unit  104  again goes into ON mode. At this time (after the fifth time  220 ), charging operation resumes and battery voltage (V b ) rises back up to its set point (again in this case about 14+/−0.2 V, although in other embodiments this can vary significantly). Thus, beginning at the fifth time  220 , the first curve  202  begins to increase again since the battery  60  is being charged. Also, since the second functional unit  104  is ON and since the battery is not fully charged, the third curve  205  again experiences a period of the periodic half-wave sinusoidal pulses  206 . 
     Turning then to  FIG. 8 , the second timing diagram  250  illustrates additional example operation of the system  40  (and additional circuitry  50  thereof) that is similar to that of the first timing diagram  200  but is different insofar as the signals correspond to operation where there are two overvoltage events that occur in relatively rapid succession. Like the timing diagram  200 , the timing diagram  250  shows first, second, third, and fourth curves  252 ,  254 ,  255 , and  258 , respectively, that are representative of the battery voltage (V b ) at the battery terminal  56 , the operational ON/OFF status of the second functional unit  104 , the battery charging current provided by the alternator system  22  and conducted by the SCR T 1 , and the voltage on the capacitor C 1 , respectively. Further as shown, in the timing diagram  250 , the second functional unit  104  is in the ON state beginning at a first time  260  up to a second time  262  at which a first overvoltage event represented by a spike  264  occurs. Relatedly, the first curve  252  indicative of the battery voltage (V b ) increases following the first time  260 , indicating that the battery  60  is being charged. The battery voltage (V b ) levels off and stops increasing at a third time  264 , prior to the second time  262 . Correspondingly, the third curve  255  includes periodic half-wave sinusoidal pulses  256  during the period when the battery is being charged between the first time  260  and third time  264 , and that includes intermittent pulses  257  (one of which is shown) during the time period between the third time  264  and the second time  262  during which trickle charging operation occurs. 
     Once the first overvoltage event represented by the spike  264  begins to occur at the second time  262 , the second curve  254  immediately switches such that the second functional unit  104  is in OFF mode. Additionally, the voltage on the capacitor C 1  represented by the fourth curve  258  increases. In the example of  FIG. 8 , the first overvoltage event corresponding to the spike  264  is short in length and particularly ends at a fourth time  266 , at which point the capacitor C 1  stops being charged. Between the fourth time  266 , and a fifth time  268 , the capacitor C 1  discharges via the eighth resistor R 8 . However, at no time during this time period does the second functional unit  104  switch back from the OFF state to the ON state, since at no time during this time period does the capacitor C 1  discharge to a degree sufficient so that the N-Channel MOSFET Q 4  stops conducting. Further, in contrast to the timing diagram  200 , in the timing diagram  250  an additional or second overvoltage event occurs as represented by a spike  270 , beginning at a fifth time  268  and ending at a sixth time  272 . 
     As a result of this second overvoltage event, the voltage on the capacitor C 1  as indicated by the fourth curve  258  again rises, this time to a higher level than was previously experienced at the fourth time  266 . Again, when the second overvoltage event is concluded at the sixth time  272 , the capacitor C 1  again begins to discharge as represented by the diminishing value of the fourth curve  258  subsequent to that time period. Throughout this time, while the second overvoltage event is occurring and during the discharging time period thereafter, the second functional unit  104  remains in the OFF mode notwithstanding any concurrent positive half cycles that may be occuring in the alternating system  22 , and consequently the battery voltage (V b ) represented by the first curve  252  remains flat (again at a level less than what was previously achieved prior to the second time  262 ). Although not shown, it will be understood that such status of the first and second curves  252  and  254  continues until the capacitor C 1  is sufficiently discharged, in accordance with the RC time constant established by the resistance value of the eighth resistor R 8  and the capacitance level of the capacitor C 1  (that is, the off time is proportional to the product of that resistance and that capacitance). After that time, which is not shown in  FIG. 8 , the second curve  252  can return to ON status and charging of the battery  60  can again occur. 
     Turning to  FIG. 9 , a third timing diagram  300  is provided that shows additional example simulated behavior of the system  40  (and additional circuitry  50  thereof). In particular as shown, a first curve  302  shows example battery voltage (again, for example, the voltage (V b ) at the battery terminal  56 ), a second curve  304  shows example voltage across the capacitor C 1 , and a third curve  306  shows example current flow through the fifth resistor R 5  of the third functional unit  106 , all as a function of time. The current represented by the third curve  306  can also be considered the gate trigger current for the SCR T 1  (which is also the current flowing through the resistor R 5 ). The timing diagram  300  again illustrates example (in this case, simulated) operations that occur when an overvoltage event occurs as represented by a spike  308  in the first curve  302 . As shown, the charging of the battery  60  by way of the SCR T 1  stops instantly when the overvoltage event occurs as indicated at a location  310  on the third curve  306 . Again, the third curve  306  can be considered to be representative of the current through the resistor R 5 , which is part of the third functional unit (SCR gate trigger unit)  106 . Also, as shown, the second curve  304  increases significantly during the overvoltage event as the capacitor C 1  is charged and then, at a time  312  at which the over voltage event is completed, the capacitor C 1  then beings to discharge. Finally, at a time  314  at which the capacitor C 1  has sufficiently discharged, normal charging resumes as indicated both by the first curve  302  and the third curve  306 . In this example, normal charging resumes once the capacitor voltage drops below 1.8 Volts (as the MOSFET Q 4  shuts OFF); nevertheless, the particular voltage level that need to be attained to allow normal charging to resume may vary depending upon the embodiment. Large darkened blocks  309  and  311  are then shown to occur (following the time at which the capacitor voltage falls below 1.8 V) at the end of the first curve  302  and the third curve  306 , respectively, which represent actual battery charge current and SCR gate trigger current, respectively. The blocks  309 ,  311  appear as solid blocks due to the large number of charging current pulses and SCR gate trigger current pulses occurring during the time period shown in the graph. 
     From the above discussion, it should be apparent that in at least some embodiments the systems, circuitry, and/or methods described herein provide a smart and inexpensive battery charging system that can be used with engine driven alternators and that protects existing electrical and electronic components on the system power line (including but not limited to the battery itself) from overvoltage transients that can occur for any of a variety of reasons (e.g., due to the application of direct alternator voltage or from other external sources connected to the system, or for other reasons). In at least some such embodiments, this is achieved by turning OFF the battery charging control circuit and completely isolating the alternator from the charging system when an overvoltage surge is detected. Additionally, in at least some embodiments, following an overvoltage event the system further provides a predetermined time delay which can be adjusted based on application needs or operating conditions. Operation of this feature is such that the turning OFF of the battery charging control circuit/isolating of the alternator is only temporary; that is, this feature resets automatically such that the system resumes normal battery charging operation without any additional intervention. The system (particularly the overvoltage protection circuit) will continue to monitor for the next overvoltage pulse on the power line of the charging system after which, when identified, it causes a reset of the time delay. Additionally, the resetting of the time delay can occur even if the system never resumed normal battery operation subsequent to an earlier overvoltage event, for example, because an additional overvoltage event occurred before a previously-established time delay following earlier overvoltage event elapsed. 
     In at least some embodiments, the system includes an overvoltage protection or overvoltage shutdown circuit (e.g., corresponding to the fourth functional unit  152  discussed above) that controls a charging control circuit that controls a SCR governing the communicating of power from the alternator to the battery (and/or a load). In the event of an overvoltage condition, the overvoltage protection circuit turns OFF the charging control circuit by grounding the base of a comparator and switch transistor (e.g., the PNP transistor Q 1 ) and thereby completely isolating the alternator from the charging system. As already noted, the overvoltage protection circuit also provides a time delay that can be predetermined and adjusted based on application needs, resets automatically to resume normal battery charging operation once the overvoltage signal is no longer active, and continues to monitor for the next overvoltage pulse on the power line of charging system after being reset. In at least some embodiments, the overvoltage protection circuit works directly with the low voltage and low current side of the rectifier regulator system. Hence it can provide relatively reliable control and protection against significant overvoltage spikes as compared to at least some conventional technologies in which excessive current and overheating of alternators are common side effects, and/or in which resetting of the system following an overvoltage event cannot occur without complete shutdown of the system. 
     In view of the above discussion, it should be appreciated that one or more embodiments of the system, circuitry, and/or methods disclosed herein can achieve one or more of a variety of advantages. For example, in at least some embodiments, the circuitry the additional circuitry  50 ) described herein can include or provide an overvoltage protection circuit (e.g., the fourth functional unit  152 ) that is suitable for use with half wave rectifier regulators and/or full wave rectifier regulators, and that shuts OFF battery charging operation by shutting down the SCR gate control circuit, thereby isolating the alternator terminals from the battery. Also for example, in at least some embodiments, the circuitry described, herein includes or provides an overvoltage protection circuit that further provides an automatic reset after the passing of a predetermined time delay and continues to monitor for any overvoltage events on an ongoing basis. Further, the control circuitry deals with the low voltage and low current side of the regulator system and hence provides more reliable control and protection against any significant overvoltage pulses. The ability to adjust the predetermined delay (e.g., by changing the resistance value of the resistor R 1  and/or the capacitance value of the capacitor C 1 ) allows for handling of known or likely conditions while still providing the essential battery charging signal for all or most other cases. 
     Also, advantageously, in at least some embodiments, the overvoltage circuit utilizes the unwanted overvoltage signal to charge a capacitor that is then employed to keep the control circuit OFF for a pre determined period of time (e.g., by way of a capacitor discharge cycle). Further, in at least some embodiments, the overvoltage circuit and/or the rectifier regulation circuit include and/or provide diagnostic indicators, one for normal operation of rectifier regulator and a second as an overvoltage shutdown indicator (e.g., the fifth and sixth functional units  154  and  156 ) via its integration into the overvoltage control circuit. Additionally in at least some embodiments, a gate trigger circuit is employed as part of/in conjunction with the rectifier regulator, where the silicon controlled rectifier has a biased gate using a RC filter to provide immunity from high frequency noise and to lower turn off time of controlled rectifier. This biasing provides ability to choose trigger frequency and adjust level of gate sensitivity. 
     Notwithstanding the above description, the present disclosure is intended to encompass additional circuits, systems, methods, and/or components or portions thereof in addition to or instead of those specifically described above. As already noted, depending upon the embodiment, the overvoltage protection systems encompassed herein can be modified to suit, and implemented in relation to, a variety of types of rectifier regulator/power regulator systems, including half wave and/or a full wave rectifier regulator systems. Further, although the use of a N-Channel MOSFET device as described herein in the overvoltage protection system is advantageous in that the device can be actuated with only a minimal voltage trigger at its gate to turn ON and can drive high current through drain and source terminals, in other embodiments other MOSFETS or other voltage-controlled devices (or still other devices, including for example current-controlled devices) can be employed in the overvoltage protection system and/or to control the battery charge current control circuit. Additionally, although the use of a capacitor and resistor in the overvoltage protection system is advantageous in terms of determining a time delay for resetting of the system, particularly since charging and discharging of a capacitor in a controlled and protected manner can be effective in driving a device such as a MOSFET, in other embodiments other circuit component(s) or devices or methods can be employed, to achieve an appropriate time delay after which normal charging operation can be resumed. Also for example, the eighth resistor R 8  can be replaced with a variable resistor by which an operator can vary the RC time constant governing the discharge of the capacitor C 1  following an overvoltage event. 
     Further, although the MOSFET device and other circuit components of the overvoltage protection circuit described above can be used for shutting down the SCR gate control unit to stop the charging operation and electrically isolate the alternator in the event of an over voltage condition, in other alternate embodiments a variety of other techniques employing a variety of different analog and/or digital circuit components can be employed. indeed, in some such alternate embodiments, a digital control system (e.g., a computer, controller, microcontroller, microprocessor, and/or other digital control components such as programmable logic devices) can be employed in place of some or all of the circuit components constituting the overvoltage protection system and/or other portions of the additional circuitry  50  for achieving overvoltage protection and/or one or more of the other functions discussed above. However, the use of a digital control system (e.g., a microcontroller) can in some circumstances be less advantageous than circuit arrangements such as those described above, for example, since in some cases functional microcontrollers-based systems can themselves require additional signal processing circuit components and/or overvoltage protection circuit components as the digital control system devices can be sensitive to high voltage signals. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.