Enhanced battery pack monitoring interface

An enhanced battery pack monitoring interface combines battery pack model identification and temperature monitoring functions. The enhanced system eliminates the need for some connecting contacts as well as several logic and converter circuits in the portable electronic device and the battery pack.

BACKGROUND
 The present specification relates to a battery pack for a portable
 electronic device.
 A battery pack is typically the main power source for portable electronic
 devices, such as cellular phones and portable computers. However, a
 battery pack can require careful handling, particularly during recharging.
 For example, in order to avoid damage, some kinds of batteries should
 typically be charged only when within a certain temperature range.
 Accordingly, many portable electronic devices provide mechanisms for
 monitoring the temperature of the battery pack to avoid charging the pack
 outside of its preferred temperature range.
 The battery pack's temperature can be monitored using a temperature sensing
 device to ascertain the precise temperature of the battery pack before
 charging. For example, a thermistor placed near or in contact with the
 battery pack is used to relay temperature information to a processor in
 the portable device powered by the battery pack.
 A cellular phone handset uses a rechargeable battery pack that often uses
 electrical connections. The handset often draws power, supplies charging
 current, verifies the model of the battery pack, and monitors the cell
 voltage and temperature during charge and discharge. This uses several
 logic circuits and analog-to-digital converters (ADC) in the handset, as
 well as many connecting contacts to the battery pack. A battery
 identification resistor provides a convenient method of tagging and
 identifying the battery pack.
 SUMMARY
 The present disclosure involves an enhanced battery pack monitoring
 interface which combines battery pack model identification and temperature
 monitoring functions. The enhanced system can eliminate the need for some
 connecting contacts as well as several logic and converter circuits in the
 portable electronic device and the battery pack.
 A combined battery model identification and temperature sensing element in
 the battery pack produces a resistive signal which is received by
 electronics in the portable device. The device electronics operates to
 extract both battery type and temperature information from the received
 signal. A gross resistance value in the signal indicates the battery type
 while the temperature is determined by an algorithmically compensated fine
 resistance value.
 The details of one or more embodiments are set forth in the accompanying
 drawings and the description below. Other embodiments and advantages will
 become apparent from the following description and drawings, and from the
 claims.

Like reference numbers and designations in the various drawings indicate
 like elements.
 DETAILED DESCRIPTION
 FIG. 1A shows a front perspective view of a conventional battery pack 100
 typically used in a portable electronic device. The conventional battery
 pack 100 has four connections 101: the positive and the negative terminals
 supplying the battery power, a battery model ID resistor terminal, and a
 temperature sensing device terminal.
 A block diagram of a battery pack 100 is shown in FIG. 1B. Battery 102 has
 a positive terminal connected to BAT+ output 110 and its negative terminal
 connected to BAT- output 112. The battery pack 100 also includes a battery
 protection circuit 104 coupled to the positive and the negative terminals
 of the battery 102.
 A battery model ID resistor 106 identifies a type of battery 102 used in
 the battery pack 100. This information is typically used by a portable
 device processor to adjust device parameters according to the battery
 model or type. A temperature sensing device 108, such as a thermistor,
 enables the device processor to monitor the temperature of the battery
 pack 100.
 FIG. 1C shows a portable device electronics 120 which is powered by battery
 pack 100. The device electronics 120 has four connections to match the
 battery pack 100 connections, and is powered through BAT+ and BAT-
 terminals. The device electronics 120 also includes resistor networks 122,
 ADCs 124 and a device processor 126.
 The resistor networks 122, connected to the battery model ID terminal and
 the temperature sensing terminal, translate the resistance values of the
 battery model ID resistor 106 and the thermistor 108 to analog voltages.
 The ADC circuit 124 converts the analog voltages to digital values
 indicative thereof. The device processor 126 uses the digital information
 to determine the type and temperature of the battery pack.
 FIGS. 2A and 2B illustrate the response profiles of the battery model ID
 resistor 106 and the thermistor 108, respectively. The battery model ID
 resistor 106 response profile shows a constant resistance value, R.sub.R,
 to indicate a specific type of battery pack. The thermistor 108 response
 profile shows a non-linear response for translating the digital
 information to a temperature reading. Thus, for example, a resistance
 value of 500 ohms, which may be equivalent to a digital value 0x1C,
 translates to 20.degree. C.
 FIG. 3A shows a front perspective view of an enhanced battery pack 300 for
 a portable electronic device. The enhanced battery pack 300 has only three
 connections 302, 304, 306. Two of the three connections are for the
 positive 302 and the negative 306 terminals supplying the battery power.
 The remaining connection 304 supplies a combined battery identification
 and temperature information. The connections 302, 304, 306 are made of
 conducting material to supply power and information to a portable
 electronic device.
 FIG. 3B shows a block diagram of the enhanced battery pack 300. The figure
 shows a battery 308 with its positive terminal connected to BAT+ output
 302 and its negative terminal connected to BAT- output 306. The battery
 pack 300 also includes a battery protection circuit 310 coupled to the
 positive and the negative terminals of the battery 308.
 The enhanced battery pack 300 combines the battery pack model ID and
 temperature monitoring functions by adding a model ID resistor to a
 thermistor circuit to form a hybrid circuit 312. In some embodiments, the
 hybrid circuit 312 is configured to operate in a narrower band of
 resistance values than the thermistor 108 in the conventional battery pack
 100. However, the operating temperature range is same as the conventional
 battery pack 100. The band of resistance values, in which the hybrid
 circuit 312 operates, indicates the model or the type of the battery pack
 300, whereas the response profile of the hybrid circuit 312 specifies a
 particular temperature corresponding to a resistance value within the
 band.
 FIG. 3C shows portable device electronics 320 which connects to an enhanced
 battery pack 300. The device electronics 320 has only three connections to
 match the enhanced battery pack 300 connections, and is powered through
 BAT+ and BAT- terminals. The connections are similarly made of conducting
 material to receive power and information from the battery pack 300. The
 device electronics 320 includes only one resistor network 322 and one ADC
 324 to translate and convert the measured resistance value into a digital
 data. A device processor 326 processes the digital data into battery model
 ID and temperature reading.
 FIG. 4 shows a response profile of the hybrid circuit 312 in the battery
 pack 300 in which bands of resistance values correspond to different types
 of battery packs. Since the total dynamic range of resistance values is
 same as the conventional battery pack, the band for any particular battery
 type is narrower than the conventional battery pack. However, in some
 embodiments, the resolution and the accuracy of the temperature reading is
 made comparable or higher by using higher resolution or higher order ADCs
 (i.e. more bits).
 In one embodiment, the total dynamic range of resistance values is chosen
 to be from 0x00 to 0xFF (hex) with the total range divided into four bands
 400, 402, 404, 406. In some embodiments, each of the four bands represents
 a battery type, thus allowing for four types of battery packs. In other
 embodiments, some bands represent a `no battery connected` mode 400 and a
 `test` mode 406. Each band is also provided with a guard band 408 to
 prevent ambiguity in recognizing the battery model or type.
 Once the battery type or model has been identified, the ADC input range is
 configured to narrow in on the voltage range, and subsequently the
 temperature range, for the battery of interest.
 FIG. 5 shows a response profile of an alternative embodiment. of the hybrid
 circuit 312 in which some bands are extended from the center toward the
 extremes in order to increase the resolution. The more often-used battery
 types are assigned to wider bands. For example, the battery types one 500
 and two 502 are assigned to the bands that are five times as wide as the
 battery types three 504 and four 506. In some embodiments, the battery
 types three 504 and four 506 are used to represent a `no battery` mode and
 a `test` mode.
 A further alternative embodiment is shown in FIG. 6 in which the response
 profile of the hybrid circuit 312 is linear. The linear response circuit
 312 provides a more accurate and uniform temperature resolution. In other
 embodiments, the thermistor/resistor configuration in the hybrid circuit
 312 is optimized for each battery type, given the required dynamic range
 for each.
 FIGS. 7A and 7B show front and rear views of a cellular telephone handset
 700 using an enhanced battery pack 702 and a corresponding device
 electronics 704. The conducting connections 706 on the battery pack 702
 mate with the corresponding connections 708 on the handset 700 which
 connect to the device electronics 704. The handset 700 also includes a key
 pad 712, various other buttons 714, a speaker 716, a microphone 718, an
 antenna 720, and other communication electronics 722 contained within the
 telephone housing 710.
 FIGS. 8A and 8B show top and bottom perspective views of a portable
 computer 800, such as a laptop computer, using an enhanced battery pack
 802 and a corresponding electronic circuitry 804. The portable computer
 800 also includes a main housing 806 that protects the computer's
 electronic circuitry 804; input devices, such as a keyboard 808 and a
 touchpad 810; and one or more output devices, such as a flat-panel display
 812 embedded in a lid housing 814.
 The advantageous features of the enhanced battery pack monitoring interface
 system include fewer connecting contacts between the battery pack and the
 portable electronic device, as well as decrease in component counts of
 logic and converter circuitry in the battery pack and the portable
 electronic device. These features lower the cost of manufacturing both
 devices. They also can lower the cost of a battery recharger since there
 are fewer connecting contacts. The contact area can also be made smaller.
 Although only a few embodiments have been described in detail above, those
 of ordinary skill in the art certainly understand that modifications are
 possible. For example, the combined interface technique is flexible enough
 to include other monitoring functions which can be sensed with
 thermistor/resistor combination. In addition, the number of connections
 (e.g. three in this disclosure) between the enhanced battery pack and a
 portable device can be changed to fit the needs of a particular
 application. All such modifications are intended to be encompassed within
 the following claims, in which: