Abstract:
A plurality of the voltage sources may be selectively connectable in a variety of different arrangements using a switch array whose connections are determined by a programmable controller. For example, a desired output voltage may be automatically provided by altering the connections between the voltage sources to achieve the desired voltage. A programmable controller may determine how to connect the voltage sources to achieve the desired output voltage.

Description:
BACKGROUND 
     This invention relates generally to voltage sources, such as batteries, for any of a variety of applications including operating a processor-based system. 
     Conventionally, battery powered or portable processor-based systems utilize a battery power source whose output is controlled by a voltage regulator. The voltage source may be made up of a plurality of batteries as one example. Because the equipment being powered, such as a processor-based system, may demand a particular input voltage and because that voltage requirement may vary during operation, typically voltage sources use a regulator to hide the variances of the voltage source due to battery discharge, for example. 
     Voltage regulators are somewhat inefficient because they dissipate some power in the course of regulating the voltage. Some types of regulators may change their output voltages on the fly, but those types of regulators are inherently linear operating regulators and require extra circuits for a digital control. In addition, regulators may require a relatively long time to change the output voltage. In some cases, switching voltage regulators may emit radio frequency interference (RFI) and so may need some type of RFI shielding. 
     Thus, there is a need for better ways to control the output voltage of a plurality of voltage sources. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a circuit diagram in accordance with one embodiment of the present invention with the voltage sources connected in series; 
     FIG. 2 is a circuit diagram of the embodiment shown in FIG. 1 with the voltage sources connected in parallel; 
     FIG. 3 is a block depiction of a controller for controlling the output voltage of a plurality of voltage sources; 
     FIG. 4 is a flow chart for software that may be utilized with the controller shown in FIG. 3 in accordance with one embodiment of the present invention; and 
     FIG. 5 is a flow chart for software that may be utilized with the controller shown in FIG. 3 in accordance with one embodiment of the present invention; and 
     FIG. 6 is a flow chart for software that may be utilized with the controller shown in FIG. 3 in accordance with one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a power supply  10  may include a plurality of voltage sources  12   a ,  12   b  and  12   c.  As indicated by the broken lines in the figure, the number of voltage sources  12  that are included may be highly variable and in some cases many more voltage sources may be included. The voltage sources  12  may be batteries as one example or solar cells as another example. A switch array  14  including switches  14   a  and  14   b  may be provided to alter the connections between the various voltage sources  12  to change the voltage across the output terminals  20  of the supply  10 . That is, any one of the voltage sources  12  may be disconnected from the output terminals  20 , may be connected in series with other voltage sources  12 , may be connected in parallel with other sources  12  or may be connected in some combination of series and parallel to develop a desired output voltage. 
     In one embodiment to the present invention, the switch array  14  includes a double pole double throw (DPDT) switch, operated by a controller, not shown in FIG.  1 . In another embodiment, transistor switches, such as field effect transistor switches, may be utilized to control the connections between the voltage sources  12 . 
     In general, any switching system may be utilized to form the switch array  14  that enables digital control of the switch state and thereby the manner connecting the voltage sources  12 . Thus, in the illustrated embodiment, the switch array  14  may be positioned to connect the voltage sources  12  in series as shown in FIG. 1 or in parallel as shown in FIG.  2 . With more voltage sources  12  a wide variety of connections may be possible to greatly increase the number of possible output voltages that may be supplied. The number of possible output voltages may also be increased by using voltage sources of a variety of different output voltages. 
     A parallel-connected capacitor  16  may be provided to smooth any switching transients. In addition, a voltage sensor  18  may be provided to detect the actual output voltage across the output terminals  20 . The sensor  18  may provide feedback to determine whether the connections set by the switch array  14  were effective in providing the desired output voltage. In some cases, the voltage sources  12  may not produce their nominal voltages. Instead, their nominal voltages may diminish over time and as a result, the resulting output voltage may be different than what would be expected. In addition, the voltage sensor  18  may be utilized to check the voltages of one or more of the voltage sources  12  in some embodiments. 
     Turning next to FIG. 3, a controller  22  may be connected to each of the switches  14   a ,  14   b  and  14   n  making up the switch array  14 . The number of switches may be highly variable as it may include any number of switches  14   a  to  14   n.  In addition, the controller  22 , which may be a processor-based device, may be coupled to receive the voltage sensor  18  output signal. The controller  22  may include its own storage  26  that stores software routines  28  and  40 . In addition, the controller  22  may provide output signals and receive input signals from an input/output device  24 . For example, user inputs may be provided to the controller  22 . As one example, when a voltage source  12  needs to be replaced the user can so indicate to the controller  22 . In response, the controller  22  may place the voltage sources  12  in parallel so that one of those voltage sources  12  may be replaced without losing device state. 
     Referring to FIG. 4, the software  28  may be utilized to monitor the output voltage of the supply  10 . Initially, the controller  22  receives a sensed voltage across the output terminals  20  from the voltage sensor  18  as indicated in block  30 . This output voltage is then compared to a table of voltages that would be expected with the connection between the voltage sources  12  that was implemented, as indicated in block  32 . If an error exists, as determined in diamond  34 , an additional voltage source  12  may be switched in, either in place of an existing voltage source  12  or as an adjunct to one or more existing voltage sources  12  or a change in the switch array  14  may be provided in order to create the desired voltage output. In some cases, auxiliary voltage sources  12  may be provided, that are connectable through switch array  14  to the rest of the supply  10 , on an as needed basis. 
     Generally, the user may provide an input signal through the input/output terminals  24  to the controller  22  indicating a desired output voltage as indicated in FIG.  5 . After receiving a user specified voltage as (indicated in block  52 ), the software  50  may cause the controller  22  to use a look-up table or may calculate the connections for the various voltage sources  12  needed to supply the desired output voltage as indicated in block  54 . The controller  22  then develops output signals that control the connections of the switch array  14  to create the desired output voltage across the terminals  20  as indicated in block  56 . Of course, each voltage change may be very quickly implemented since the controller  22  may rapidly cause the switch array  14  to changed its connections. 
     Referring to FIG. 6, voltage tracking software  40  may be used to monitor the output voltages produced by each of the voltage sources  12 . Initially, the software  40  receives source  12  voltage information as indicated in block  42 . The source  12  voltage information provides information about how much voltage was supplied at any given time by an individual voltage source  12 . This may be achieved by actually sensing the output voltage using the sensor  18  or by calculation knowing the desired output voltage and thereby determining the contribution from any one voltage source  12  to that output voltage. 
     In addition, software  40  receives information about the amount of time that a particular voltage source  12  supplied a given voltage as indicated in block  44 . With the output voltage level and supply time, the software  40  calculates the burden on each source  12  as indicated in block  46 . The output burden is accumulated output burden that includes the current service performance as well as past history. Based on the load on any one voltage source, the use of the voltage source  12  in the future may be balanced. That is, if one voltage source  12  is being used to an excessive degree, in the future the supply  10  may automatically preferentially use other voltage sources  12  in place of an overused voltage source  12 . This in turn may result in an extension of the life of the various voltage sources  12  in some embodiments. 
     While an embodiment is illustrated in which the voltage setting, compensation and drain balance are accomplished by using software, hardware techniques may be utilized as well. 
     The present invention may be utilized with a variety of devices that use a range of voltages such as radio subsystems for variable power transmission, displays for variable brightness, and processors for variable performance, to mention a few examples. 
     In accordance with some embodiments of the present invention, the regulation inefficiency of conventional voltage regulators may be avoided or reduced, resulting in longer voltage source life and potentially fewer voltage sources. In some embodiments, digital control may be provided over the voltage sources, facilitating digital or on the fly voltage changes. Moreover, these changes may be implemented relatively quickly compared to systems using voltage regulators, especially when the switch array  14  uses transistor switches. In addition, in some cases, radio frequency interference (and the need to shield against such interference) may be avoided. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.