Abstract:
Power supply equipment includes an adapter which converts power from a power source to DC power for powering an electronic device. The adapter further includes circuitry which produces a data signal for use by the electronic device to control power flow within the electronic device. A cable, which is electrically coupled to the adapter, has a connector at its distal end. The power supply equipment further includes a plurality of tips, each of which has an input connector, an output connector and at least three conductors. The input connector of each tip is detachable mateable to the connector on the distal end of the cable. The output connector of each tip is detachably mateable to a corresponding electronic device. The conductors transfer the DC power and the data signal from the input connector to the output connector. A tip output connector has a shape and size dependent on the shape and size of a power input opening of the electronic device to which the tip corresponds. Accordingly, selection of the appropriate tip allows the adapter to provide the data signal, as well as the DC power, to various electronic devices.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 12/840,952, filed on Jul. 21, 2010, now U.S. Pat. No. 7,999,412 issued on Aug. 16, 2011, which is a continuation of application Ser. No. 11/604,950, filed on Nov. 28, 2006, now U.S. Pat. No. 7,868,486 issued on Jan. 11, 2011, which is a continuation-in-part of application Ser. No. 10/758,933, filed on Jan. 15, 2004, now U.S. Pat. No. 7,453,171 issued on Nov. 18, 2008. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field 
         [0003]    This invention relates to power supply equipment which includes an adapter and interchangeable tips. Via the tips, the power adapter is able to provide a data signal, as well as power, to various electronic devices. 
         [0004]    2. Description of the Related Arts 
         [0005]    There are power systems in the art which allow a user to hook up a DC/DC adapter to an automobile outlet, to supply regulated DC power to power an electronic device, such as a notebook computer. Automobile outlets typically provide a DC voltage in a range between 11.0 and 14.1 Volts. Some power systems also allow the user to hook up the DC/DC adapter to an airplane output such as the EMPOWER system. EMPOWER typically provides a DC voltage in a range between 14.5 and 15.5 Volts. 
         [0006]    Accordingly, some DC/DC adapters can be used with both an automobile outlet and the EMPOWER system to provide a regulated DC power to the electronic device such as the notebook computer. Notebook computers often contain lithium ion batteries. Such batteries can be recharged when the notebook computer is hooked up to the DC/DC adapter. For example, if the user is in a car, the user can couple a DC/DC adapter to the notebook computer and to the cigarette lighter outlet to power the notebook computer. The batteries in the notebook computer will draw some of the DC power supplied to recharge the batteries of the notebook computer if they are low in power. Accordingly, the user can simultaneously use the notebook computer and recharge the batteries therein. 
         [0007]    The user can also use the DC/DC adapter while on an airplane, by plugging the DC/DC adapter into the EMPOWER outlet. The EMPOWER outlet and the automobile outlets have different sizes and shapes. Accordingly, the user can directly plug the DC/DC adapter into the EMPOWER outlet, and can place a connector over the EMPOWER plug of the DC/DC adapter and then plug the connector into the automobile cigarette lighter outlet. When the user hooks the DC/DC adapter up to the EMPOWER outlet and then to the electronic device, the electronic device receives the regulated DC power. However, if the charging circuitry in the battery malfunctions, the battery can overheat or even catch on fire when recharging from an EMPOWER DC source. If the battery were to catch on fire while an airplane in which the emPlower outlet is located is flying, the fire would have the potential to cause the airplane to crash or cause substantial damage. 
         [0008]    To address this problem, one system in the art provides a connector to connect between the DC/DC adapter and the notebook computer to inform the notebook computer not to recharge the batteries.  FIG. 1  illustrates a power supply system according to the prior art. As shown, a DC power source  100  is coupled to a DC/DC adapter  105  via a cable  102 . The DC/DC adapter  105  receives power from the DC power source  100  and outputs regulated DC power to an electronic device  120 , via a cable  110  and a connector  115  coupled to the end of the cable  110 . 
         [0009]    The DC/DC adapter  105  can provide three output pins to the electronic device  120 , as shown in  FIGS. 2A and 2B  of the prior art. The first pin can provide the output voltage (i.e., V out ), the second pin can provide a ground reference (i.e., GND), and the third pin can provide a data line (i.e., V data ) to instruct the notebook as to whether the batteries should be recharged or not. For example, as shown in  FIG. 2A , V data  could be tied to GND to indicate that the DC power source  100  is the EMPOWER system and therefore the battery should not be recharged. Alternatively, as shown in  FIG. 2B , V data  could also be left open (i.e., to provide a non-grounded floating voltage) when the DC power source  100  in a cigarette lighter outlet of an automobile. Accordingly, when using the DC/DC adapter  105  while in an automobile, the user would use a connector  115  having the V data  line floating, and when using the DC/DC adapter  105  with the EMPOWER system of an airplane, the user would use a connector  115  having the V data  line tied to GND. 
         [0010]    However, problems arise when the user forgets to change the connector  115  for use with the automobile when the user is in an airplane. Accordingly, if the user has the wrong connector  115  attached when using with the EMPOWER system, a battery of an electronic device  120  such as a notebook computer can charge the battery even when used with the EMPOWER system, and if the charging circuitry of the battery malfunctions, overheating or even a fire can occur, resulting in damage to the notebook computer. Also, if the connector  115  is damaged or flawed, then it may not provide the correct V data  signal to the notebook computer, allowing the notebook computer to recharge the batteries in an airplane when they shouldn&#39;t be allowed to do so. 
         [0011]    Accordingly, current DC/DC power adapter systems are deficient because they are incapable of automatically and intelligently informing an electronic device  120  coupled thereto of the DC power source (i.e., the EMPOWER system or an automobile cigarette lighter outlet). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a power supply system according to the prior art; 
           [0013]      FIG. 2A  illustrates a first connector to coupled a power supply system to an electronic device according to the prior art; 
           [0014]      FIG. 2B  illustrates a second connector to coupled a power supply system to an electronic device according to the prior art; 
           [0015]      FIG. 3  illustrates a power supply system according to an embodiment of the invention; 
           [0016]      FIG. 4A  illustrates a tip having digital control circuitry according to an embodiment of the invention; 
           [0017]      FIG. 4B  illustrates a tip having analog control circuitry according to an embodiment of the invention; 
           [0018]      FIG. 5A  illustrates comparison circuitry according to an embodiment of the invention; 
           [0019]      FIG. 5B  illustrates comparison circuitry according to an additional embodiment of the invention; 
           [0020]      FIG. 6  illustrates an electronic device according to an embodiment of the invention; 
           [0021]      FIG. 7A  illustrates a method of determining and outputting V data  according to an embodiment of the invention; 
           [0022]      FIG. 7B  illustrates a method of receiving V data  and allowing power to flow to devices within the electronic device based on V data  according to an embodiment of the invention; 
           [0023]      FIG. 8  illustrates a power supply system according to an embodiment of the invention; 
           [0024]      FIGS. 9A and 9B  illustrate a tip including control circuitry according to embodiments of the invention; 
           [0025]      FIG. 10  illustrates a tip including control circuitry and a measurement circuit according to an embodiment of the invention; and 
           [0026]      FIG. 11  illustrates a power supply system including a tip according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    An embodiment of the present invention is directed to a power supply system to determine a DC power source (e.g., an automobile cigarette lighter outlet or an EMPOWER airplane outlet) coupled thereto and send a signal indicative of the power source to an electronic device coupled thereto. The electronic device may be a notebook computer or other portable consumer electronic device, for example. Based on the signal sent to the electronic device, the electronic device may control the amount of power drawn to prevent overheating. For example, when a notebook computer is hooked up and the power source is the EMPOWER system, the electronic device may disable charging of the internal batteries of the notebook computer, in order to prevent damage or overheating of the batteries due to malfunction or failure. The DC power source may be determined by voltage comparison circuitry, such as a comparator, or by a voltage comparison device including a processor. 
         [0028]      FIG. 3  illustrates a power supply system  301  according to an embodiment of the invention. As shown, the adapter  340  may be used with an AC power source  300  or a DC power source  305 . In other embodiments, only a DC power source  305  may be utilized to supply power. The AC power source  300  may be coupled to an AC/DC adapter  310  via a cable  342 . The DC power source  305  may be coupled to both a DC/DC adapter  315  and comparison circuitry  320  via a cable  345 . The DC power source  305  may be an automobile&#39;s cigarette lighter outlet or an airplane&#39;s EMPOWER system outlet, for example. AC/DC adapter  310  may convert AC power from the AC power source  300  into regulated DC power, which is supplied to post-regulation circuitry  325 . The post-regulation circuitry  325  may provide an output voltage (V out ) and a ground reference (GND) to a tip  330  coupled to the adapter  340  via a cable  350 , as further explained below with respect to  FIGS. 4A and 4B . The tip  330  may be coupled to an electronic device  335  to provide the power thereto from the power supply system  301 . The tip  330  may be removable from the cable  350  and may be inserted into a power input opening of the electronic device. Tips  330  may have different shapes and sizes, depending up the shape and sizes of the power input openings of the respective electronic devices  335  being powered. The tip  330  may also include control circuitry  365  to provide a signal to control circuitry  370  of the adapter  340 . The signal may be sent to the control circuitry  370  via the cable  350 . In one embodiment, the control circuitry  365  of the tip  330  may include digital components to provide a digital signal to the control circuitry  370  of the adapter  340 . The digital signal may be utilized to set the magnitude of V out  and limit the amount of current which may be drawn from the adapter  340 . The post-regulation circuitry  325  regulates the voltage to what the tip  330  tells it to provide. 
         [0029]    Alternatively, the tip  330  may include analog components and may provide voltage programming and current programming voltages (V Vprogram  and V Iprogram , respectively) to the adapter  340 . V Vprogram  may be utilized to set the magnitude of V out . For example, there may be a linear relationship between V Vprogram  and V out  where V out  is 3 times as large as V Vprogram . Accordingly, if V Vprogram  had a magnitude of 3.0 Volts, V out  would have a magnitude of 9.0 Volts, and if V Vprogram  had a magnitude of 2.0 Volts, V out  would have a magnitude of 6.0 Volts. The analog circuitry may contain passive or active components. 
         [0030]    Accordingly, regardless of whether the tip  330  has analog or digital control circuitry, a single adapter  340  may be used to supply power to a plurality of different electronic devices  335  having different power requirements. 
         [0031]    The adapter  340  may also include comparison circuitry  320 . The comparison circuitry  320  may compare a magnitude of a voltage received from the DC power source  305  with a reference voltage to determine whether the DC power source  305  is an automobile cigarette lighter outlet or an EMPOWER airplane outlet. As stated above, automobile cigarette lighter outlets typically provide a DC voltage having a magnitude within the range of 11.0 Volts and 14.1 Volts. An EMPOWER airplane outlet typically provides a DC voltage having a magnitude within the range of 14.5 and 15.5 Volts. Accordingly, the reference voltage may be set at a level between the high end of the automobile cigarette light outlet voltage (i.e., 14.1 Volts) and the low end of the EMPOWER airplane outlet voltage (i.e., 14.5 Volts). For example, the reference voltage may be set at 14.3 Volts. Accordingly, if the magnitude of the DC power source is greater than 14.3 Volts, then the comparison voltage may determine that the received DC voltage has a greater magnitude than the reference voltage and the DC power source  305  is therefore the EMPOWER airplane outlet. However, if the magnitude of the DC power source is less than 14.3 Volts, then the comparison voltage may determine that the received DC voltage has a smaller magnitude than the reference voltage and the DC power source  305  is therefore the automobile cigarette lighter outlet. 
         [0032]    The comparison circuitry  320  may output a signal V data  based upon whether the DC power source is determined to be the automobile cigarette lighter outlet or the EMPOWER airplane outlet. For example, the comparison may output 5 Volts if the automobile cigarette lighter outlet is detected, and 0.0 Volts if the EMPOWER airplane outlet is detected. In alternative embodiments, different voltages for V data  may be used. In additional embodiments, the comparison circuitry  320  may output a digital signal, such as a stream of bits, indicative of the DC power source  305 . V data  may be sent via cable  350  to the tip  330 , and straight over to the electronic device  335 . The electronic device  335  may include a controller  360  which is responsive to V data . For example, if the electronic device  335  is a notebook computer and V data  is indicative of the EMPOWER airplane outlet system, the controller  360  may disable battery charging circuitry  600 , thereby preventing recharging of the batteries. And if the V data  is indicative of the automobile cigarette lighter outlet as the DC power source  305 , the controller  360  may enable battery charging circuitry to allow the batteries to be recharged. 
         [0033]    Although  FIG. 3  illustrates an adapter  340  which includes both a AC/DC adapter and a DC/DC adapter, other embodiments may include only a DC/DC adapter, and no AC/DC adapter. 
         [0034]      FIG. 4A  illustrates a tip  400  having digital control circuitry  402  according to an embodiment of the invention. As shown, the tip  400  receives V data , V out  and GND from the adapter  340  and allows them to all flow to the electronic device  335 . The digital control circuitry  402  may receive the V out  and GND signals and may output a control signal to the adapter  340  to set the magnitude of V out  and limit the current provided. The control signal may be sent to the adapter  340  via the cable  350  between the tip  400  and the adapter  340 . The digital control circuitry  402  may include a processor and a memory device, for example. In some embodiments, the tip  400  may be separable from cable  350 , and in other embodiments, the tip  400  may be physically part of the cable  350 . 
         [0035]      FIG. 4B  illustrates a tip  405  having analog control circuitry  410  according to an embodiment of the invention. As shown, the tip  405  receives V data , V out  and GND from the adapter  340  and allows them to all flow to the electronic device  335 . The analog control circuitry  410  may receive the V out  and GND signals and may output V Vprogram  and V Iprogram  to the adapter  340 . V Vprogram  and V Iprogram  may be sent to the adapter  340  via the cable  350  between the tip  405  and the adapter  340 . The analog control circuitry  400  may include passive or active components, for example. In some embodiments, the tip  400  may be separable from cable  350 , and in other embodiments, the tip  400  may be physically part of the cable  350 . 
         [0036]      FIG. 5A  illustrates comparison circuitry  320  according to an embodiment of the invention. As shown, the comparison circuitry  320  includes a comparator  500 . The comparator  500  receives (a) the DC power signal from the DC power source  305 , and (b) a reference voltage, V ref . The comparator outputs V data  based on whether the magnitude of the DC power from the DC power source exceeds V ref , as described above with respect to  FIG. 3 . 
         [0037]      FIG. 5B  illustrates comparison circuitry  320  according to an additional embodiment of the invention. As shown, the comparison circuitry  320  includes a processor  505 . The processor  505  receives (a) the DC power signal from the DC power source  305 , and (b) value of a reference voltage stored in memory. The processor  505  then outputs V data  based on whether the magnitude of the DC power from the DC power source exceeds V ref , as described above with respect to  FIG. 3 . The processor  505  may output a single high or low voltage (e.g., 5.0 Volts or 0.0 Volts) based on the detected DC power source. Alternatively, the processor  505  may output a stream of bits to indicate the DC power source. 
         [0038]      FIG. 6  illustrates an electronic device  335  according to an embodiment of the invention. 
         [0039]    As shown, the electronic device  335  may receive GND, V out  and V data  from the tip  330 . V data  may be received by a controller  360 . The controller  360  may disable battery charging circuitry  600  of the electronic device  335  from charging batteries when V data  is indicative of the EMPOWER outlet. Alternatively, the controller  360  enables battery charging circuitry  600  so that the batteries of the electronic device may be charged based on the value of V data . 
         [0040]      FIG. 7A  illustrates a method of determining and outputting V data  according to an embodiment of the invention. The processing shown in  FIG. 7A  may be implemented by the adapter  340 . First, DC power is received  700  from the DC power source  305 . Next, the comparison circuitry determines  705  whether the magnitude of the voltage of the DC power received is greater than V ref . If “no,” the comparison circuitry determines the DC power source  305  to be an automobile cigarette lighter outlet, and processing proceeds to operation  710 , where V data  is output with a signal/voltage magnitude indicating that the DC power source  305  is the automobile cigarette lighter outlet. Processing then returns to operation  700 . If “yes,” at operation  705 , processing proceeds to operation  715 , where V data  is output with a signal/voltage magnitude indicating that the DC power source  305  is the EMPOWER airplane outlet. 
         [0041]      FIG. 7B  illustrates a method of receiving V data  and allowing power to flow to devices within the electronic device  335  based on V data  according to an embodiment of the invention. First, the electronic device  335  receives  720  the V data  signal. As discussed above, the V data  signal is sent from the adapter  340  through the tip  330  and over to the control circuitry  365  of the electronic device  335 . Next, based on the V data  signal, a first set of predetermined devices may be prevented  725  from receiving power. For example, if the electronic device  335  is a notebook computer, the control circuitry  365  may prevent batteries from recharging if V data  indicates that the DC power source is the EMPOWER airplane outlet. Other devices/components in the electronic device  335  may also be prevented from receiving power or from functioning in a certain way. 
         [0042]    At operation  730 , a second set of predetermined devices may be allowed to receive power based on the Vdata signal. For example, if V data  indicates that the DC power source is an automobile cigarette lighter outlet, then power may be available to batteries of the electronic device  335  to allow recharging. Other devices/components in the electronic device  335  may also be allowed to receive power or function in a particular way. 
         [0043]    In embodiments described above, the V data  signal may be used to send a signal to the control circuitry  365  indicating the DC power source. This signaling may be done via a discrete bit, an analog signal, a data signal line, an analog voltage, or via any other suitable manner. The V data  signal may be transmitted from the adapter  340  to the tip  330  and electronic device  335  via a single signaling line or multiple signaling lines. 
         [0044]      FIG. 8  illustrates a power supply system  800  according to an embodiment of the invention. The power supply system  800  is similar to the power supply system  301  shown in  FIG. 3 . However, unlike the power supply system  301 , in which the adapter  340  itself contains comparison circuitry  370 , the adapter  340  of power supply system  800  does not contain the comparison circuitry  805 . Instead, a regular adapter  340  may be used and the electronic device  335  itself includes the comparison circuitry  805  for determining the DC power source. The electronic device  335  may be a notebook computer and may implement the methods shown in  FIGS. 7A and 7B . 
         [0045]      FIG. 9A  illustrates a tip according to an embodiment of the present invention. The tip  900  includes control circuitry  902  and a controller  950 . The tip  900  is coupled to an adapter  940  and may have a cable disposed between the adapter  940  and the tip  900 . The adapter  940  transmits V out  and GND to the tip  900 . In an embodiment of the invention, digital or analog control circuitry  902  transmits a programming signal or a control signal to the adapter  940 . In an embodiment of the invention, digital or analog control circuitry  902  may transmit a plurality of programming signals to the adapter. Illustratively, digital or analog control circuitry  902  may transmit a voltage control signal to regulate the voltage output (Vout) from the adapter  940 . The digital or analog control circuitry  902  may also transmit a current control signal to limit the current output from the adapter  940 . The V out  and GND signals are passed through the adapter  940  to the electronic device  935 , such as a laptop, PDA, or cellular phone, to provide power to the electronic device. 
         [0046]    In an embodiment of the invention, the tip  900  may also receive a value, which is illustrated by reference numeral  980  in  FIG. 9A . The value may be representative of whether or not the power adapter is an approved adapter which can be connected to an electronic device  935 . For example, for safety reasons, certain digital music player or laptop manufactures only desire to have certain manufacturers&#39; power adapter connected to their system. Accordingly, the power adapter may transmit a value that indicates that the power adapter  940  is approved for powering the electronic device. Alternatively, the value may be representative of a maximum power output that is available at the time from the power adapter. For example, the value may represent that only 70 watts of power are available from the power adapter because the power adapter has been limited to that output power. Instead of receiving a value from the power adapter, the tip  900  may receive a character string. The character string may identify whether or not the power adapter is an approved adapter for powering the electronic device  935 . The value or the character string may be received at input connector  985  of the tip  900 . The input connector  985  may receive the value or character string and may pass through this signal or information to the output connector  990 . Under certain operating conditions, there may be no modification of the value or character string in the tip  900 . The output connector  990  is coupled to the electronic device  935  and passes the value or character string to the electronic device. A conductor  995  may couple the input connector  985  to the output connector  990 . 
         [0047]      FIG. 9B  illustrates an alternative embodiment of a tip according to an embodiment of the invention. In an embodiment of the invention, the tip  900  may include a controller  950 , wherein the controller  950  includes a receiver  952 , a memory  954 , and a transmitter  956 . In an alternative embodiment of the invention, a programmable Dallas Semiconductor programmable memory (i.e., DS2502) may be substituted for a controller and may include the receiver  952 , memory  954 , and transmitter  956 . The receiver  952  may receive a signal from the electronic device  935 . The signal may be a request from the electronic device  935  to interrogate the tip  900  and identify whether or not an approved power adapter  940  is coupled to the tip  900  and thus the electronic device  935 . Once the controller  950  receivers the request from the electronic device  935 , the controller  950  extracts a character string from the memory  954  and utilizes the transmitter  956  to transmit the character string to the electronic device  935 . The character string is representative of the power adapter to which the tip  900  is coupled. In an embodiment of the invention, a microcontroller may be programmed and could be utilized in place of the transmitter  956 , a receiver  952  , and a memory  954 . The character string may represent that the power adapter  940  and/or tip  900  is approved to be connected to the electronic device, e.g. a laptop or a cellular phone. Under certain operating conditions, the character string represents that a rechargeable battery within the electronic device can be charged by the power adapter  940  and tip  900  combination. Under certain operating conditions, the character string is indicative of a maximum power available from the power adapter. Under certain operating conditions, a value can be stored in the memory  954  where the value is indicative for the maximum power available from the power adapter. Illustratively, the value may be a power (or wattage) value or a current value. 
         [0048]    The transmitter  956  may communicate with the electronic device  935  via a one-wire interface. The transmitter  956  may communicate with the electronic device  935  via other communication protocols, including serial communication protocols. 
         [0049]      FIG. 10  illustrates a second embodiment of a tip according to an embodiment of the invention. The tip  900  may include an analog or digital control circuitry  910 , a controller  950 , and measurement circuit  960  (e.g., a voltage sense circuit or a current sense circuit). The measurement circuit  960  may measure a magnitude level of a programming or control signal e.g., (V Iprogram ), that is being transmitted to the power adapter  940 . In an embodiment of the invention, the programming or control signal has a value representative of a maximum current available to be output by the adapter  940 . For example, a voltage magnitude of the programming or control signal identifies a value of current (e.g., in amperes) that the power adapter is available to output. Illustratively, each 0.5 volts in the programming or control signal may represent one amp of current that the power adapter can output. A programming or control signal having a magnitude of 2.5 volts represents that the power adapter is limited to output 5 amperes and the power output is limited to 100 watts (if the fixed voltage output is 20 volts). The measurement circuit  960  may be implemented using a comparator or a number of comparators that compare a voltage level of the control signal to a reference voltage level or a number of reference voltages. 
         [0050]    In an alternative embodiment of the invention, the measurement circuit  960  may be implemented by an analog-to-digital converter. The analog-to-digital converter may measure a value of the control signal or the programming signal and identify the value which is representative of the power available to be output from the power adapter. In an embodiment of the invention, the analog-to-digital converter may be used in conjunction with a microcontroller. The analog-to-digital converter may be separate from the microcontroller or the analog-to-digital converter may be incorporated into the microcontroller. 
         [0051]    The measurement circuit  960  takes the measured magnitude level of the programming or control signal and sends the information to the controller  950 . A memory  954  may store a plurality of character strings. Alternatively, the memory  954  may store a plurality of values. Each of the plurality of character strings or values may represent a potential power output level of the power adapter  940 . For example, one character string may be represent that the power adapter can output 90 watts while another character string represents that the power adapter can output 140 watts. The controller  950  receives the magnitude level of the programming/control signal from the measurement circuit  960  and selects the corresponding character string stored in the memory  954 . Alternatively, the controller receives the magnitude level of the programming or control signal and selects the corresponding value stored in the memory  954 . 
         [0052]    After the corresponding character string or value is selected, the corresponding character string is transmitted to the electronic device  935  through the transmitter  956 . The electronic device receives the character string and acts in response to the received character string or value. For example, the character string may indicate that the power adapter coupled to the tip (which is connected to the electronic device) can output 75 watts. Based on this information, a controller in an electronic device  935  (e.g., a laptop) may prevent the power adapter from charging the rechargeable battery within the electronic device  935  because the electronic device  935  may require all of the 75 watts of power. 
         [0053]    The controller  950  may be a microcontroller. The controller  950  including the receiver  952 , transmitter  956 , and memory  954  may be a semiconductor memory chip such as a Dallas Semiconductor DS2502 programmable memory. The receiver  952  and transmitter  956  may communicate with the electronic device via a number of protocols, e.g., the one-wire interface communication protocols, a serial interface communication protocol, etc. 
         [0054]      FIG. 11  illustrates an alternative embodiment of a power supply system utilizing DC power source comparison circuitry according to an embodiment of the present invention.  FIG. 11  is similar to the power supply system illustrated in  FIG. 3  and also includes a microcontroller  950  in the tip  330 . In  FIG. 11 , the microcontroller  950  receives a signal from the power adapter  340  in addition to the V out  signal and ground signal. The power source determination signal may be referred to as a V data  signal and may be generated by the comparison circuitry  320  in the adapter. The power source determination signal may identify a power capability of the external power source is an external automobile DC power source, an external AC power source, or an external airplane DC power source. For example, the power source determination signal may identify that the power adapter is connected to an external airplane DC power source and is limited to a number of watts of output, e.g., 50 or 60 watts of power. Alternatively, the power source determination signal may identify that the power adapter is connected to an external automobile power source, e.g., 90 watts or 100 watts. 
         [0055]    The microcontroller  950  may receive the power source determination signal. Based on the received power source determination signal, the microcontroller  950  may extract a character string corresponding to the received power source determination signal from a memory. The memory  954  (see  FIGS. 9A ,  9 B, and  10 ), as noted before, may store a number of character strings. Alternatively, the memory  954  may store a number of values and the microcontroller  950  may select one of the number of values. Although  FIG. 11  does not illustrate that the microcontroller includes the memory  954 , receiver  952 , and transmitter  956 , the microcontroller  950  may incorporate these components. Alternatively, the memory  954 , receiver  952 , and transmitter  956  may be located in devices outside of the controller  950  (e.g., not incorporated therein). The number of character strings or values may each represent a different power capability of the power adapters which can be coupled to the tip via a cable. Illustratively, one character string or value may represent a 90 watt power adapter, one character string may represent a 130 watt power adapter, one character string may represent a 70 watt power adapter, and one character string may represent that the power adapter has a limited power supply capability, e.g., less than 70 watts. 
         [0056]    In an embodiment of the invention, no character string or value may be transmitted if the power adapter cannot generate a certain wattage of power. This may represent that the power adapter and tip cannot be utilized to charge the battery of the electronic device. The microcontroller  950  may transmit the selected character string to the electronic device. A controller  360  in the electronic device may receive the selected character string and may perform a plurality of actions based on the selected character string. For example, if the selected character string identifies that the power adapter has a limited power capability, e.g., less than 50 watts or 70 watts, the controller  360  may place the electronic device in a mode of low power consumptions, e.g., turning off display earlier or not allowing charging of the battery in the electronic device. Under other operating conditions, the character string or value may identify that an AC adapter is the external power source and can provide 130 Watts, and the controller  360  may allow the battery in the electronic device to be charged by the power adapter and place the electronic device in a high power consumption mode, e.g., brightness of screen and hard drive. 
         [0057]    Under certain operating conditions, rather than a character string, the microcontroller  950  may have a number of current levels that represent different power capabilities of adapters. Illustratively, in other words, a first current level may represent that the power adapter  340  can supply 130 watts, a second current level may represent that the power adapter  340  can supply 90 watts, a third current level represents that the power adapter  340  can supply 70 watts, and a fourth current level may represent the power adapter  340  supplies less that 70 watts. 
         [0058]    While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.