Abstract:
The disclosed apparatus and systems are adapted to implement dynamic power control in order to condition and store, and/or immediately utilize, energy from one or more available power inputs, whether the inputs are constantly, regularly, or intermittently available, singly or in various combinations. Power control circuits according to the invention provide means for dynamically responding to input availability and output requirements in order to prioritize input energy selection, input signal conditioning, and output power delivery adapted to the application and operating environment.

Description:
TECHNICAL FIELD 
     The invention relates to power control circuitry. More particularly, the invention relates to apparatus and systems for receiving, conditioning, and outputting power from various input power or energy sources for ultimately supplying power to a load, or for charging a storage element such as a battery and then supplying power to a load. 
     BACKGROUND OF THE INVENTION 
     The need for some form of power control circuitry is ubiquitous in electronics. Many power sources are available to electronic system designers. Multiple energy or power sources are often accessible to some degree, however, their availability may occur intermittently and in various combinations, making capitalizing on their availability problematic. Examples of potential power sources that may be capable of using energy available in a system&#39;s operating environment include; piezoelectric generators, solar generators such as photovoltaic circuits, thermoelectric “Seebeck” generators, wind or other mechanical generators, conventional AC sources, disposable batteries, and so forth. Such sources may or may not be continuously available, due to the nature of the energy source, or due to changes in the operating environment of the electronic system. Therefore, an intermediate storage element such as a rechargeable battery or capacitor is often used in order to provide continuity of supply. For example, energy is captured from an available source, e.g., vibration energy is harnessed using a piezoelectric generator, and is stored, e.g., with a battery or array of batteries, for ultimate use by an electrical load. Thus, circuitry useful for charging storage elements such as capacitors or batteries is an important consideration in the design of electronic systems, and particularly for portable systems. In addition to the variability of energy sources, the output needs encountered by a given electronic system may also be variable. Examining batteries as a common example of power control, it is well known that restoring a discharged battery to a fully charged state, and maintaining it in a fully charged condition, is a multifaceted problem involving a number of factors. For example, battery chemistry, (e.g., Nickel-Cadmium (Ni—Cd), Nickel Metal-Hydride (NiMH), and Lithium-Ion (Li-ion)), battery age, useful life, physical environment, capacity, and number of cells, are just some of the factors that must be considered in selecting not only a suitable battery, but also a power control circuit to optimally utilize the battery. The availability of charging power is one such consideration that must be addressed in charging system and associated power control design. Useable apparatus and systems for harnessing variable and intermittent input power levels for power control circuits and electronic systems would provide useful advantages in the arts. 
     It is known that it is often necessary to provide selectable charging level controls for regulating the output of charging circuitry. Charging circuits known in the arts are generally designed for accepting a fixed input power level, and for selecting from two or more predetermined output power levels in order to charge a storage element. For example, in some applications, such as a “universal” charger, it is desirable to accommodate different capacity batteries by providing different pre-determined charging output levels. Appropriate charging rates are generally dependent upon battery chemistry and construction. Generally, fast charging refers to methods that can charge a storage element in one to two hours, and slow charging refers not only to longer charging periods, but also implies a charging level low enough that overcharging the battery is less of a potential problem. It is known in the arts to provide selectable pre-determined charging levels based on a scheme for fast charging a battery (or other storage element) up to a set level, and then providing a lesser slow charging current for maintaining the storage element in a fully charged state. Such charging schemes typically rely on some form of temperature or voltage sensing, and perhaps a timer, in order to protect against overcharging, which could result in shortening battery life, battery failure, or a spectacular explosion. At the other end of the charging continuum, for most battery types, once the battery is discharged into an undervoltage, or overdischarged, condition, a continuing voltage or current draw from the battery beyond the undervoltage level could chemically degrade the battery, permanently reducing its charge capacity, reliability, and useful service life. Thus, particularly for power control systems used with batteries as storage elements, charging circuit efficiency, reverse-current protection, and low quiescent current, are highly desirable traits. 
     The present invention is directed to overcoming or diminishing problems present in electronics, power control circuitry, and particularly charging systems, of the prior art, and contributes one or more heretofore unforeseen useful advantages to the arts. 
     SUMMARY OF THE INVENTION 
     In general, the apparatus and systems of the invention are adapted to implement dynamic power control in order to condition and store, and/or immediately utilize, energy from one or more available power inputs, whether the inputs are constantly, regularly, or intermittently available, singly or in various combinations. It is contemplated that the invention may be used with relatively high or low intensity energy sources for producing power input signals, which may exist in environments commonly encountered by electronic systems. For example, input signals of this nature may include those generated by photovoltaic sources, piezoelectric generators, Seebeck generators, RF generators, mechanical generators such as wind or water turbines, or torque “harvested” as electrical energy by braking rotating machinery. These and similar input power sources, due to their variability, both in availability and intensity, require sophisticated power control circuitry in order to be put to practical use. Multiple input channel power control circuits implemented according to the principles of the invention provide means for dynamically responding to input availability and output requirements in order to prioritize input energy selection, input signal conditioning, and output power delivery adapted to the application and operating environment. 
     According to one aspect of the invention, examples of preferred embodiments are disclosed in which power control circuits include capabilities for using multiple input power sources and producing one or more outputs. Operably coupled between the input sources and outputs, a conditioning circuit is adapted for dynamically altering the input signals to provide one or more output signals within a selected voltage and current range. 
     According to another aspect of the invention, in an example of a preferred embodiment, a power control circuit includes input terminals for receiving one or more input power signals as well as one or more output terminals for delivering output signals. A conditioning circuit is configured for receiving the input power signals and for dynamically converting the input power signals into one or more conditioned signals within desired voltage and current ranges. An intermediate storage element is provided in order to receive the conditioned signals from the conditioning circuit. The conditioning circuit, and its intermediate storage element, are capable of providing output signals to the output terminals. 
     According to another aspect of the invention, an example of a preferred embodiment of a power control circuit further includes reverse blocking circuitry for blocking reverse current at one or more of the terminals. 
     According to yet another aspect of the invention, an example of a preferred embodiment of a power control circuit includes signal conditioning circuitry having an off-active switching module for continuously monitoring one or more terminals and for dynamically switching the conditioning circuit between on and off states responsive to selected variable circuit parameter thresholds. 
     According to still another aspect of the invention, an example of a preferred embodiment of a power control circuit includes a number of input terminals for coupling to external power sources. Output terminals are provided for coupling to chargeable storage elements. Also included is sensing circuitry in a configuration for producing sensor signals indicative of selected variable parameters at one or more terminal. The power control circuit includes a conditioning circuit for receiving and altering the input power signals in order to supply desired output signals to the output terminals. Among its functional blocks, the conditioning circuit has a step-up/step-down regulator for adjusting voltage levels up or down as needed. Reverse blocking circuitry is provided for preventing reverse current at the power control circuit terminals. An off-active switch module is also included for continuously monitoring the terminals in order to dynamically switch the power control circuit, or any of its modules, between on and off states responsive to selected variable parameter thresholds. 
     The invention has advantages including but not limited to providing advantages in economy and efficiency for using a plurality of power sources for charging a storage element or array of storage elements, maintaining a charge level, or powering a load. Further advantages may be realized by harvesting available power inputs for storage or use as opportunities for increased input are manifested, and by prioritizing among potential power inputs. These and other features, advantages, and benefits of the present invention can be understood by one of ordinary skill in the arts upon careful consideration of the detailed description of representative embodiments of the invention in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more clearly understood from consideration of the following detailed description and drawings in which: 
         FIG. 1  is a block diagram of an example of a preferred embodiment of a system of the invention; 
         FIG. 2  is a schematic diagram of an example of a preferred embodiment of a circuit according to the invention; and 
         FIG. 3  is a schematic diagram of an example of a preferred embodiment of a circuit according to the invention. 
     
    
    
     The drawings are not to scale, and some features of embodiments shown and discussed are simplified or amplified for illustrating principles and features, as well as anticipated and unanticipated advantages of the invention. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     While the making and using of various exemplary embodiments of the invention are described herein, it should be appreciated that the present invention provides inventive concepts which can be embodied in a wide variety of specific contexts. It should be understood that the invention may be practiced with various implementations to suit different practical applications without altering the principles of the invention. For purposes of clarity, detailed descriptions of functions and systems familiar to those skilled in the pertinent arts are not included. 
     Apparatus and systems of the invention provide useful improvements directed toward the challenges of power control and charging in electronic systems, particularly for applications in which one or more input power sources may be available intermittently, in various combinations, and at varying voltage and current levels. Power received at various input terminals from available energy sources may preferably be utilized according to a selected priority. Input power is conditioned in order to provide usable voltage and current. The apparatus and systems include controls responsive to preprogrammed and dynamically determined output parameters and power input parameters. 
     Now referring primarily to  FIG. 1 , a simplified overview of an exemplary power control system according to the invention is shown and described. In this block-diagram, a power control system  10  has a conditioning circuit  12 , further described below, operably coupled using suitable input terminals  14 ,  16 ,  18 , to at least one, and preferably several power inputs, such as for example, a photovoltaic device  14 , a turbine-driven generator  16 , and piezoelectric generator  18 . Of course, many alternative power sources may be used without departure from the invention. Each of the power input terminals  14 ,  16 ,  18 , is capable of delivering a power input signal, denoted IN 1 , IN 2 , and IN 3  respectively, to the conditioning circuit  12  from a suitable corresponding input source. Preferably, the input signals IN 1 , IN 2 , IN 3  are variable in availability, intensity, or both. Accordingly, the conditioning circuit  12  is adapted for accepting the input signals IN 1 , IN 2 , IN 3  in virtually any intensity and combination, limited only by the practical capabilities of the input sources. Preferably, the system  10  may be programmed to prioritize among input sources according to preselected criteria relating to system requirements and anticipated operations. For example, in a particular application, a photoelectric input may be assigned a higher priority than a back-up battery, in order to conserve battery power whenever practical. The input sources are coupled to the conditioning circuit  12  by any suitable conductive connector. Suitable input filters may be included at the input terminals or at the sources in order to smooth input power signals and to minimize noise and electromagnetic interference (EMI) from the system  10  to the input sources and from the input sources to the system  10 . Both direct current (DC) and alternating current (AC) sources may be used as known in the arts for charging circuits in general. The conditioning circuit  12  is equipped for dynamically altering one or more, or all, of the received input signals IN 1 , IN 2 , IN 3  by increasing or decreasing their voltages or currents in order to provide one or more output signals, e.g., OUT 1  within dynamically selected ranges at one or more output terminals  20 . Preferably, an intermediate storage element  22  such as a battery, capacitor, combination, or array, is provided in order to accept a conditioned signal from the regulator circuit  24  from a conditioning circuit  12  for ultimately contributing to the output OUT 1 . Additional load elements (not shown) such as electronic circuits or electromechanical apparatus may be directly connected to the output terminals, as well as external storage elements such as batteries, capacitors, either singly or in arrays. External storage or load elements connected to the output terminals for use with the power control circuit  10  may also be concurrently coupled with additional external power sources, devices, and circuitry. For example, the power control circuit  10  may be used for applications that require a constant power supply, in which two storage elements may be connected to the output terminal(s) in an arrangement that allows one storage element to supply power required by a load while the other storage element is recharged using the power control circuit  10 . An output regulator  27  is included in order to control the output signals, e.g., OUT 1  in this example, according to the needs of the application. For example, in a constant-voltage charger application intended for charging Li-ion batteries, the output regulator may be used to force an output terminal connected to the battery to a set-point voltage, for example, about 4.2V, and upon reaching this threshold, to then provide only enough current sufficient to hold output terminal at the set voltage. For another example, in a constant-voltage regulator application, the output regulator may be used to supply an output terminal connected to a microprocessor to provide power to the said microprocessor. 
     Now referring primarily to  FIG. 2 , a schematic diagram depicts an example of practical circuitry for components of a preferred embodiment of a power control circuit  10  in more detail. A conditioning circuit  12  has an input terminal  14  coupled to an input source, such as a paper battery, or photovoltaic cell, and output terminals  20  are provided for receiving the output signals OUT 1 , OUT 2 , produced by the circuit  10 , for example to supply a charge to an external storage element or load (not shown). Preferably, intermediate storage elements  22  such as batteries or capacitors are also included in the power control circuit  10 . The intermediate storage elements  22  are preferably charged when a conditioned signal is available in greater abundance than required at the output terminal(s)  20 . The intermediate storage elements  22  may then be discharged and power added to the output signals, e.g., OUT 1 , OUT 2  at times when an increase in output power is desired. As shown, the input signal IN 1  is received and fed into a regulator module  24 , preferably with external bucket capacitors C 1 , C 2 , C 3  as needed. The regulator module  24  preferably includes step-up/step-down capabilities for conditioning input signals up or down as needed. Preferably, the regulator module  24  output level is set with an enabling switch  26  for selecting an output level based on data relating to the needs of the charge storage element (external to the power control circuit) preferably provided by control means associated with the output terminals  20 . An oscillator  28  is preferably provided for controlling the regulator module  24  based on input voltage or current relative to the desired output. A linear regulator  30  is preferably provided for regulating IN 2  voltage to a selected output level. Reverse-blocking circuitry  32  is also preferably provided in order to prevent reverse current in the event the input voltages are at a lower potential that the voltage across the output terminal  20 . Preferably, an off-active switch  34  is also provided as part of the conditioning circuit  12  as well. The off-active switch  34  is adapted to conserving power by being particularly configured to draw ultra-low bias current when active, and no current when in the “off” state. In the “off” state, the off-active switch  34  will disconnect the intermediate storage elements, e.g., Vcap  22 , Vbat  22 , from the multi-output regulator  27 . 
     The possible variations of implementations of the apparatus and systems using the invention are many and cannot, and need not, all be shown. An additional example of a preferred embodiment of a power control circuit is provided in  FIG. 3 . In this example, the circuit  10  includes power inputs to a conditioning circuit  12  from a low-power battery such as a paper battery  14 , a DC source  16 , such as a more powerful battery, and a piezoelectric generator  18 . In this example, the input signal IN 1 , is preferably transferred to a regulator module  24  with associated bucket capacitors C 1 , C 2 . An enable switch  26  is used to select input level. As in the preferred embodiment described with reference to  FIG. 1 , an oscillator  28 , boost regulator  24 , bridge rectifier  38 , and linear regulator  30  are preferably used to control the step-up/step-down regulator module  22  based on input signal, e.g., IN 1 , IN 2 , IN 3 , and IN 4  levels and output OUT 1 , OUT 2  requirements. Also in common with the above-described embodiment, the regulator circuit  12  preferably includes reverse-blocking circuitry  32  and off-active switch  34 . As shown at reference numeral  38 , a rectifier, such as a bridge rectifier, may be included for conditioning input signals, such as, IN 3 , IN 4 , from the piezoelectric generator  18 . Such an arrangement shown in this example is generally preferred for applications in which input polarity is not fixed and/or in which smoothing of an input signal may be required. A shunt module  40  may preferably be included for shunting excess power from the inputs as required for potential input levels anticipated for particular implementations. 
     A sensor module  42  is preferably adapted for dynamically monitoring various parameters, particularly voltage, current, or temperature, at the terminals of the system  10  and for providing feedback useful to the conditioning circuit  12 . The sensor module  42  preferably includes capabilities for sensing selected variable parameters at the output terminals  20  and/or at connected external storage elements. Preferred embodiments may typically include voltage detectors and temperature detectors positioned proximal the output terminals  20 , or connected storage elements in order to generate feedback signals reflective of conditions at the storage elements. The sensing module  42  may include switching means for interrupting the operation of the system  10  in the event that selected overvoltage or overheating thresholds are reached. For example, in a charging system, the sensor module may be configured to sense voltage level ranges acceptable for the terminals. Under operating conditions at voltages below a selected maximum output voltage threshold, the step-up capabilities of the regulator module may then be used to increase the voltage of the received input signals in order to produce a higher output voltage. In the event a higher input voltage is present, the step-down capabilities may be used to decrease the input voltage to acceptable output levels. In the event an overvoltage or reverse voltage condition is sensed, the inputs may be shunted, stored in intermediate storage elements, or switched off as appropriate to the circumstances. Sensor modules may similarly be used to dynamically switch one or more of the inputs or outputs independently according to operating conditions. It should be appreciated by those skilled in the arts that the power control circuit may be used to implement a variety of different charging modes such as an initial fast charge followed by a trickle charge. 
     The multiple input channel power control circuitry of the invention contributes one or more useful advantages not otherwise present in the arts, including but not limited to providing power control capabilities for efficient and opportunistic energy harvesting for electronic devices and charge storage elements. While the invention has been described with reference to certain illustrative embodiments and particular advantages, those described herein are not intended to be construed in a limiting sense. For example, variations or combinations of steps or apparatus in the embodiments shown and described may be used in particular cases without departure from the invention. Various modifications and combinations of the illustrative embodiments as well as other advantages and embodiments of the invention will be apparent to persons skilled in the arts upon reference to the drawings, description, and claims.