Abstract:
A method and apparatus for generating a high voltage at a battery system. The apparatus in one embodiment includes a supply node configured for direct or indirect coupling to a supply voltage. A converter is coupled between an input node and an output node, wherein the converter is configured to operate in a forward mode or a reverse mode. The converter generates a voltage at the converter output node for charging a battery when operating in the forward mode, wherein a magnitude of the voltage generated at the converter output node is less than a magnitude of the supply voltage. The converter generates a voltage at the converter input node when operating in the reverse mode, wherein a magnitude of the voltage generated at the converter input node is different than a magnitude of a voltage provided by the battery. A control circuit is coupled to and configured to control operation of the converter in the forward mode or the reverse mode.

Description:
BACKGROUND 
     Mobile devices such as smart phones, tablet computers (tablets), etc., employ rechargeable batteries. Mobile devices are often sold with AC power adapters to enable users to recharge the batteries when needed. AC power adapters typically generate DC power in high voltage form. Batteries, however, often require a lower voltage DC power to recharge. 
     DC-DC voltage convertors, such as step down DC-DC converters, are often employed inside mobile devices and used in converting high voltage DC power into low voltage DC power for recharging batteries. These DC-DC converters are often non-isolated, which means they do not employ a transformer when converting power. The present invention will be described with reference to DC-DC voltage converters it being understood the present invention should not be limited thereto. 
     SUMMARY 
     A method and apparatus for generating a high voltage at a battery system. The apparatus in one embodiment includes a supply node configured for direct or indirect coupling to a supply voltage. A converter is coupled between an input node and an output node, wherein the converter is configured to operate in a forward mode or a reverse mode. The converter generates a voltage at the converter output node for charging a battery when operating in the forward mode, wherein a magnitude of the voltage generated at the converter output node is less than a magnitude of the supply voltage. The converter generates a voltage at the converter input node when operating in the reverse mode, wherein a magnitude of the voltage generated at the converter input node is different than a magnitude of a voltage provided by the battery. A control circuit is coupled to and configured to control operation of the converter in the forward mode or the reverse mode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention may be better understood in its numerous objects, features, and advantages made apparent to those skilled in the art by referencing the accompanying drawings. 
         FIGS. 1A and 1B  are block diagrams illustrating a voltage converter employing the present invention. 
         FIG. 2A  is block diagram illustrating an example DC-DC converter that could be employed in the voltage converter of  FIGS. 1A and 1B . 
         FIG. 2B  is a graph illustrating operational aspects of the DC-DC converter in  FIG. 2A . 
         FIG. 3  is a block diagram illustrating an example mobile device employing one embodiment of the present invention. 
         FIGS. 4A and 4B  are timing charts illustrating operational aspects of the DC-DC converter employed in the mobile device of  FIG. 3 . 
         FIG. 5  is a block diagram illustrating an example mobile device employing another embodiment of the present invention. 
         FIG. 6  is a block diagram illustrating example mobile devices, each employing a respective embodiment of the present invention. 
     
    
    
     The use of the same reference symbols in different drawings indicates similar or identical items. 
     DETAILED DESCRIPTION 
       FIGS. 1A and 1B  illustrate in block diagram form a voltage converter employing the present invention. The voltage converter is coupled to a rechargeable battery and a power node capable of receiving high voltage DC power from an AC power adapter. The combination of voltage converter and rechargeable battery may be employed in a mobile device. 
       FIG. 1A  shows the voltage converter receiving high voltage DC power.  FIG. 1A  shows the voltage converter operating in a forward mode in which it converts the high voltage DC power into low voltage DC power for recharging the battery. The voltage converter can also operate in a reverse mode when the power node is open. In the reverse mode, the voltage converter converts low voltage DC power provided by the battery into a lower, equal or higher voltage DC power for use by another circuit (not shown). For the purposes of explanation only, the present invention will be described with reference to the voltage converter converting the low voltage DC power provided by the battery into a higher voltage DC power, it being understood the present invention should not be limited thereto.  FIG. 1B  shows the voltage converter operating in the reverse mode. 
     The voltage converter shown in  FIGS. 1A and 1B  may take many different forms. In one embodiment, the voltage converter of  FIGS. 1A and 1B  my employ a non-isolated, DC-DC converter (hereinafter DC-DC converter), it being understood that the voltage converter of  FIGS. 1A and 1B  should not be limited thereto.  FIG. 2A  illustrates in block diagram form, relevant components of an example DC-DC converter  100 , it being understood DC-DC converters should not be limited thereto. The example DC-DC converter  100  is coupled to receive an input DC voltage Vin from the AC power adapter (not shown). DC-DC converter  100  generates a DC output voltage (i.e., Vout), which is lower in magnitude than Vin. In this regard, DC-DC converter  100  is operating in the forward mode as a step-down converter. 
     With continuing reference to  FIG. 2A , high side and low side transistors M 1  and M 2 , respectively, are coupled at a common node to inductor  102 , which in turn is coupled to output node  104 . For purposes of explanation only, all transistors described herein will take form in an N-channel or P-channel MOSFETs, it being understood that the present invention should not be limited thereto. Moreover, DC-DC converters described herein can be formed on a single silicon substrate, either alone or with other circuit devices such as drivers, analog-to-digital converters, microcontrollers, etc., it being understood the present invention should not be limited thereto. 
     Driver  106  generates complimentary, high side and low side square waves for controlling transistors M 1  and M 2 , respectively. In the illustrated example, driver  106  generates the complimentary square waves as a function of a square wave input Vsw provided by, for example, a microcontroller (not shown). The pulses of the complimentary high side and low side square waves activate transistors M 1  and M 2 , respectively. The high side square wave controlling transistor M 1  has a pulse width of t1, while the low side square wave controlling transistor M 2  has a pulse width of t2. Transistor M 1  transmits current I 1  to output node  104  via inductor  102  with each pulse of the high side square wave, and transistor M 2  transmits current I 2  from ground to output node  104  via inductor  102  with each pulse of the low side square wave.  FIG. 2B  illustrates a graphical representation of currents I 1  and I 2 , the combination of which forms Iout. Since the high side and low side square waves are complimentary, which means they do not overlap, only one of the transistors M 1  and M 2  is activated at a time. 
     Square wave input Vsw can have an adjustable duty cycle t1/(t1+t2). One of ordinary skill in the art understands the magnitude of Vout depends on duty cycle t1/(t1+t2). Thus, a microcontroller that generates Vsw can adjust the magnitude of Vout by adjusting the duty cycle t1/(t1+t2) for Vsw. The frequency of all square waves described herein can vary, it being understood that the present invention should not be limited thereto. 
     Some mobile devices such as smart phones and tablet computers employ internal system components (e.g., CPUs) that operate on low voltage power provided by rechargeable batteries. As noted, DC-DC converters can be used to recharge these batteries. It is also noted that while recharging the batteries, DC-DC converters can also provide operational power to internal system components. 
     Mobile devices can be manufactured with ports that provide high DC voltage (i.e., voltage higher than the voltage provided by internal batteries) to external devices. In order to provide this higher voltage, mobile devices are manufactured with an additional converter (e.g., a step-up DC-DC converter and associated microcontroller) for converting battery power for external use. Unfortunately, the inclusion of the additional converter increases the manufacturing costs of mobile devices. 
       FIG. 3  illustrates relevant components of an example mobile device  300  that employing one embodiment of the present invention. As will be more fully described, battery system  301  includes a voltage converter  302  coupled to a battery pack  304 , which includes a rechargeable battery cell or cells (hereinafter battery)  306  and a fuel gage integrated circuit  308 . In the embodiment shown in  FIG. 3 , converter  302  and battery pack  304  are coupled to one or more internal system components (e.g., a CPU)  309  and can provide low voltage power thereto. Converter  302  and battery pack  304  can also provide high voltage power to a device external to the mobile device. Mobile device  300  may take form in a smart phone, tablet computer, docking station, etc, or any other device that employs a rechargeable battery for mobile operation. 
     Battery system  301  can operate in distinct modes. In a charging or forward mode of operation, converter  302  converts high DC voltage power provided by an AC adapter (not show) into low voltage DC power for internal use, e.g., recharging battery  306 . In a reverse mode of operation, converter  302  can convert low voltage DC power provided by battery  306  into high voltage DC power. This high voltage can be used to power a device, such as a device that is external to mobile device  300 . Converter  302  can dynamically adjust the magnitude of the voltage it provides to the external device Importantly, mobile device  300  need not include a separate device (e.g., a step up DC-DC converter and associated microcontroller) for generating the high voltage power during mobile operation. 
     Converter  302  includes the DC-DC converter  100  of  FIG. 1 . DC-DC converter  100  can be operated in the forward mode as a step-down converter to convert high voltage provided by an AC adapter (not shown), into low voltage power at output node  320 . The low voltage output of DC-DC converter  100  can be used for recharging battery  306 . The low voltage output can also be used to power one or more system components  309  (e.g., a CPU) if present. DC-DC converter  100  can also be operated in the reverse mode as a step-up converter for converting low voltage provided by battery  306  into high voltage for use by an external device. DC-DC converter  100  provides this high voltage at external connector  323  via node  322 . For purposes of explanation only, this description will presume that all internal system components, including the one or more system components  309 , operate on the lower voltage power provided by DC-DC converter  100  or battery  306 . In other words, converter  302  only provides high voltage power to external devices. Additionally, this description will presume converter  302  provides high voltage power to external devices only when converter  302  operates in the reverse mode. During this mode of operation, converter  302  is not coupled to the AC power adapter. 
     As noted, battery system  301  can provide high voltage power to an external device via node  322  and connector  323 . In another embodiment, battery system  301  may include several connectors uniquely configured (e.g., sized) for connection to different types of external devices, respectively. Converter  302  or another device can selectively couple node  322  to any one of these several connectors. In this alternative embodiment, DC-DC converter  100  can be operated to provide the connector with a voltage having a magnitude that depends on the connector to which node  322  is coupled. In yet another embodiment, connector  323  can be selectively coupled to node  322  or node  320  to enable battery system  301  to provide an external device with low voltage power from battery  306  or high voltage power from DC-DC converter  100 . Converter  302  or another device can selectively couple nodes  320  or  322  to connector  323  in this alternative embodiment. 
     With continuing reference to  FIG. 3 , converter  302  includes a converter control integrated circuit (CCIC)  312 , which includes a microcontroller  314  and other components (not shown), e.g., analog-to-digital converters that can generate digital representations of Vout, Vin, Iin, etc. Microcontroller  314  can perform various functions in response to processing these digital representations and/or other information in accordance with executable instructions stored in memory. For example microcontroller  314  can use one or more digital representations of Vin and/or Iin to determine whether an AC power adapter is coupled to supply node  310 . Microcontroller  314  can use one or more of the digital representations to calculate the duty cycle of Vsw that is needed to maintain Vin or Vout at a predetermined voltage magnitude. 
     When microcontroller  312  detects supply node  310  is coupled to an AC power adapter, microcontroller  314  should operate DC-DC converter  100  in the forward mode of operation during which microcontroller  314  calculates a duty cycle t1/(t1+t2) for Vsw that is needed to maintain Vout at a first predetermined magnitude for charging battery  306 .  FIG. 4A  is a timing chart that illustrates aspects of DC-DC converter  100  operating as a step-down converter during the forward mode of operation. When microcontroller  314  detects supply node  310  is open, microcontroller  314  may operate DC-DC converter  100  in the reverse mode of operation in which high voltage power is provided to an external device via node  322  and connector  323 . In the reverse mode, microcontroller calculates a duty cycle t1/(t1+t2) needed to maintain the voltage at node  322  and connector  323  at a second predetermined magnitude, which is higher than the first predetermined magnitude. It is noted that microcontroller  314  may alter the duty cycle of Vsw in the reverse mode of operation as the voltage provided by battery  306  varies. Thus, as the charge on battery  306  depletes during the reverse mode of operation, microcontroller  314  decreases the duty cycle of Vsw in order to maintain the voltage at node  322  at the second predetermined magnitude. It should be noted that in the reverse mode of operation, the one or more system components  309  can continue operate using power provided by battery  306 .  FIG. 4B  is a timing chart that illustrates aspects of DC-DC converter  100  operating as a step-up converter during the reverse mode of operation. 
     In an alternative embodiment, microcontroller  314  can receive information that identifies the type of external device coupled to connector  323 . In this embodiment, microcontroller  314  can calculate the second predetermined magnitude of voltage needed by the external device, and adjust the duty cycle of Vsw accordingly. In other words, converter  302  can generate the external voltage with a magnitude that depends on the type of external device coupled to connector  323 . Additional functions of microcontroller  314  are contemplated. 
     As noted, converter  302  can provide low voltage for use by the one or more system components  309  and/or for recharging battery  306  when operating in the forward mode. Converter  302  can also provide high voltage power for use by a device external to mobile device  300  when operating in the reverse mode. It is noted that in this latter mode of operation, one or more system components  309  may continue operating using the low voltage power provided by battery  306 . 
     Battery pack  304  includes fuel gage integrated circuit (FGIC)  308 , which includes a microcontroller  316  and other components (not shown) such as analog-to-digital converters that generate digital representations of, for example, the voltage across battery  306  and the current flow into or out of battery  306 . Microcontroller  316  can perform various functions in response to processing these digital representations and/or other information in accordance with executable instructions stored in memory. For example microcontroller  316  can use the digital representations and/or other information to monitor operational parameters of battery  306 . Microcontroller  316  can disconnect battery  306  from output node  320  if the voltage across battery  306  falls outside a predetermined range. Additionally, microcontroller  316  can calculate a value representing the total charge of battery  306 , which in turn can be used to calculate the remaining time mobile device  300  can operate before battery  306  needs to be recharged. The time can be displayed by the mobile device  300 . Additional functions of microcontroller  316  are contemplated. It is noted that microcontrollers  314  and  316  can communicate with each other while performing various functions such as monitoring and/or controlling the battery system. In one embodiment, a unified microcontroller can replace microcontrollers  314  and  316  and provide the functional features thereof. It is noted that components contained in CCIC  312  and FGIC  324  can operate off the voltage provided by battery  306  or DC-DC converter  100 . 
     As noted, mobile device  300  can provide high voltage power to an external device by reverse operation of DC-DC converter  100 . To further illustrate this concept,  FIG. 5  shows a mobile device  502  releasably connected to another mobile device  504 . For the purposes of explanation only, mobile device  502  takes form in a tablet computer (tablet) while mobile device  504  takes form in a tablet computer docking station (docking station), it being understood that tablets and docking stations should not be limited thereto. 
     As will be more fully described, docking station  504  includes a DC-DC converter that can be operated in the forward or reverse modes. In the forward mode, the DC-DC converter can convert high voltage into low voltage (e.g., 4.0V-8.4V) for recharging a battery. In the reverse mode, the DC-DC converter can convert low voltage provided by the battery into high voltage for use by tablet  502 . 
     With continuing reference to  FIG. 5 , docking station  504  contains a battery system that includes most of the components of the battery system of mobile device  300 . As a result, the battery system of docking station  504  operates in substantially the same manner as mobile device  300  described above. While mobile device  300  and docking station  504  are similar, some differences exist. Docking station  504  does not include the one or more system components  309 . Further, connector  323  of docking station  504  can be selectively coupled to node  322  or node  320 , in order to provide tablet  502  with the voltage from battery  306  or the higher voltage provided by the battery system when it operates in the reverse mode. 
     Tablet  502  also contains a battery system, which is similar to the battery system in docking station  504 . The battery system of tablet  502  includes a converter  506  and battery pack  508 , each of which can provide low voltage (e.g., 2.0V-4.2V DC) power to one or more system components  510 . Battery pack  508  includes a one cell battery  512  coupled to a field gauge integrated circuit (FGIC)  514 . 
     The battery system of tablet  502  can operate in a charging or forward mode. In the charging mode, converter  506  converts high voltage power provided by an AC adapter (not shown) coupled to first supply node  516  or high voltage power provided by docking station  504 . The voltage provided by docking station  504  can be either the voltage (i.e., 4V-8.4V DC) provided by battery  306  or the stepped up voltage provided by converter  302  at node  322 . The converted power at node  524  can be used to recharge battery  512  or to operate the one or more system components  510 . When the converter is not operating in the charging mode, converter  506  is disabled, but battery pack  508  continues to provide low voltage power to the one more system components  510 . 
     Converter  506  includes a DC-DC converter  518 , which is identical to the DC-DC converter  100  of docking station  504 . DC-DC converter  518  operates as a step-down converter during the charging mode of operation, and converts high voltage provided at node  516  or node  522  into low voltage power at node  524 . In the embodiment shown in  FIG. 5 , DC-DC converter  518  is not operated as a step-up converter. 
     Converter  506  includes a converter controller integrated circuit (CCIC)  526 , which includes a microcontroller  530  and other components (not shown), e.g., analog-to-digital converters that can generate digital representations of T/Vout, T/Vin, T/Iin, etc. Microcontroller  530  can perform various functions in response to processing these digital representations and/or other information in accordance with executable instructions stored in memory. For example, microcontroller  530  can use the digital representations and/or other information to determine whether voltage is present at first supply node  516  and/or second supply node  522 . If microcontroller  530  determines that a voltage is present at first supply node  516 , microcontroller  530  can open switch  520  thereby isolating DC-DC converter  518  from second supply node  522 . If microcontroller  530  determines that first supply node  516  is open and high voltage is present at second supply node  522 , microcontroller  530  can close switch  520 . 
     Microcontroller  530  can calculate a duty cycle for T/Vsw that is needed to convert the high voltage T/Vin at node  536  into low voltage at node  524 . It is noted the duty cycle needed to maintain T/Vout at a particular voltage (e.g., 2.4 volts) depends on the magnitude of T/Vin, which may differ depending on whether switch  520  is opened or closed. Thus, microcontroller calculates the duty cycle of T/Vsw as a function of the magnitude of T/Vin that is measured at node  536 . It is also noted that battery  512  can be more rapidly recharged by converter  506  using the higher voltage power provided reverse mode operated DC-DC converter  100  as opposed to the voltage provided by battery  306 . Lastly, microcontroller  530  can determine if supply nodes  516  and  522  are both open (no voltage is detected at supply nodes  516  and  522 ). If no voltage is detected at these nodes, microcontroller  530  may disable DC-DC converter  518 . 
     Battery pack  504  includes fuel gauge integrated circuit (FGIC)  514  that includes a microcontroller  532  and other components (not shown) such as analog to digital converters that generate digital representations of, for example, the voltage across battery  512  and the current flow into or out of battery  512 . FGIC  514  is substantially similar to FGIC  308  of docking station  504 . As such, microcontroller  532  performs essentially the same functions that are performed by microcontroller  316  described above. For example, microcontroller  532  can use the digital representations and/or other information to monitor operational parameters of battery  512 . Microcontroller  532  can disconnect battery  512  if the voltage across battery  512  falls outside a predetermined range. Microcontroller  532  can also calculate the remaining time tablet  502  can operate before battery  512  needs to be recharged. 
     In an alternative embodiment, tablet  502  may provide high voltage power to an external device.  FIG. 6  illustrates tablet  502  shown in  FIG. 5  with an external connector coupled to node  536 . In this alternative embodiment, the functional aspects of microcontroller  530  are extended so that converter  506  can operate in the forward or reverse mode. Microcontroller  530  can detect the presence of an external device at connector  534 . When the external device is detected, converter  506  operates DC-DC converter  518  in the reverse mode as a step-up converter to convert the low voltage of battery  512  into high voltage at node  536 . This high voltage power is provided to the external device via connector  534 . As the charge on battery  512  depletes, microcontroller  530  can dynamically adjust the duty cycle of T/Vsw in order to maintain the magnitude of voltage at node  536 . 
     Although the present invention has been described in connection with several embodiments, the invention is not intended to be limited to the specific forms set forth herein. On the contrary, it is intended to cover such alternatives, modifications, and equivalents as can be reasonably included within the scope of the invention as defined by the appended claims.