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Contents
1. a power converter circuit having an output coupled to the power line to provide current to the coupled portable device for charging a battery of the portable device the power converter to receive a feedback input signal a signal conditioning circuit having a first input a second input and an output to provide the feedback input signal based on the first and second inputs the first input being coupled to the output of the power converter and a compensation processor having an input coupled to the data line to receive a code that represents a measure of a battery charging circuit s input voltage the processor to generate a compensation signal at the second input ofthe signal conditioning circuit to adjust the feedback input signal in response to the received code 27 The electronic device of claim 26 wherein the commu nications interface supports 1 a first communications pro tocol for use by a core circuit of the electronic device to perform core communications with the coupled portable device and 2 a second different communications protocol for use by the compensation processor to perform voltage drop compensation 28 The electronic device of claim 27 wherein the compen sation processor is to use the second communications proto col to signal at least one of the following pertaining to the electronic device manufacturer date of manufacture maxi mum output power capability specified power line voltage serial number and2. may bea communications interface connec tor such as a USB connector or other computer peripheral bus connector has at least one data line or data pin D1 a power line or power pin P and a return reference pin R While the one or more data lines are primarily used for data communi cations with an external device the power line is primarily used for delivering power from the EPS 18 Note that in this example there are two data lines D1 and D2 serving prima rily the role ofa serial differential communications link The connector 20 in this case has four electrical contacts or pins a separate one for each of the data power and return lines These electrical contacts will mate with a mating connector that is at the end of the cable assembly 12 referred to as the PD side connector 11 allowing communications with an external device over the data lines D1 D2 This is enabled by a bus phy circuit 22 that performs translations between the physical layer signaling on the data lines D1 D2 and higher layer functions of the PD 10 not discussed here The PD 10 also includes a battery charging circuit 26 having an input coupled to receive current through the power line P of the connector 20 when coupled to the EPS 18 Between the connector 20 and input port of the battery charg ing circuit 26 the power line P exhibits parasitic resistors and inductors e g due to flexible wiring circuits and ferrites In this example an overvoltage prot
3. the Vbus line The controller 3 also has an input which is used to sense or measure the voltage on the power line Vbus at the input of the battery charging circuit as digitized by the ADC 25 The controller 3 may also set a current limit of the battery charging circuit 26 which draws current on the Vbus line based on having detected the identification of the EPS 18 and in particular the output de current capability of the EPS 18 These functions of the controller 3 may be performed and implemented for the most part as described above for the other embodiments of the invention Still referring to FIG 6 the controller 3 once it has deter mined that the EPS 18 is a special accessory device or adapter or other type of power source that may have greater current capability than a default level begins a communica tion session with the compensation decoder and control logic 86 also referred to as processor 86 of the EPS 18 This is performed over the at least one data line D For instance when a pair of data lines D D are available a two wire bi directional protocol such as 12C may be used See I C bus specification and user manual Rev 03 19 Jun 2007 UM10204 Note that other serial bus protocols that are relatively low cost because there is no need for high speed communications in this case may be used The controller 3 may have level shifters to impose and sense transitions on the otherwise pulled up D D lines pull
4. authentication value 29 An electronic device comprising a communications interface to be coupled to a portable device the interface having first and second data lines and a power line a power converter circuit having an output coupled to the power line to provide current to the coupled portable device for charging a battery of the portable device the power converter to receive a feedback input signal a difference amplifier having a first input coupled to the first data line and a second input coupled to the second data line a selector having a first input a second input and an output to provide the feedback input signal based on the first and second inputs alternately the first input being coupled to the output of the power converter the second input being coupled to an output ofthe difference ampli fier and decoder and control logic having an input coupled to one of the first and second data lines to receive an indication from the coupled portable device that there is a need for voltage drop compensation and in response signal the selector to switch from its first input to its second input 30 The electronic device of claim 29 wherein the first and second data lines are for differential signaling 31 A method in an electronic device for supplying current to an external portable device comprising indicating through a data line of a communications inter face that is coupled to the external portable device that US
5. diagram of an example process that may be performed in the PD to compensate for voltage drop in the communications interface through which the PD is coupled to an EPS for purposes of charging the battery ofthe PD Not all of the operations depicted in FIG 3 are needed in all instances furthermore their sequence may be different Also the process in FIG 3 is particularly suited to the above 20 25 30 35 40 45 50 55 60 65 8 described circuit schematic of FIG 2 and especially where the EPS is a USB power adapter however the concepts are also applicable to other types of EPS and other types of communications interfaces One of the first operations to be performed in the process of FIG 3 is to determine whether an EPS is coupled to the PD through the communications interface One way to do so is to check for sufficient voltage on the power line ofa computer peripheral bus operation 51 and then attempt to enumerate on the one or more data lines of the bus operation 53 Ifthe voltage is insufficient then the process stops If the enumera tion succeeds then the coupled EPS may be assumed to be a computing host whose current limit max current capacity is then determined If the enumeration fails then it may be assumed the EPS is a dedicated power adapter unit e g a USB wall adapter a USB cigarette lighter adapter and its current limit is determined by for instance decoding a signal on the data
6. drawn from the power line into an input node of a battery charging circuit and sensing a voltage at the input node and wherein the driving the power line includes signaling a code that represents the sensed voltage 19 An electronic device comprising a communications interface to be coupled to a portable device the interface having a data line and a power line a power converter circuit having an output coupled to the power line to provide current to the coupled portable device for charging a battery of the portable device an analog multiplexer circuit having a first signal input coupled to the data line and a second signal input coupled to the output ofthe power converter an output to provide a feedback input signal as derived from one of the first and second signal inputs and a control input and control circuitry having an input to receive a measure of said current and an output coupled to the control input to select between the first and second signal inputs in response to the measure of said current 20 The electronic device of claim 19 wherein the commu nications interface comprises aconnector through which the data and power lines pass to receive a mating and detachable connector that is at an end of a cable 21 The electronic device of claim 19 further comprising a current detector to determine when the measure of said current is above a predetermined threshold 22 The electronic device of claim 21 further comprising an
7. external power source EPS through a communica tions interface connector of the device the connector having a data line and a power line selecting a higher current limit rather than a lower current limit for drawing current from the power line to charge the battery and driving the data line so as to stimulate the EPS to compen sate for voltage drop on the power line wherein dc voltage ofthe power line rises in response to the data line being driven US 8 350 522 B2 13 14 The method of claim 13 wherein the detecting com prises sensing that the power line exhibits sufficient voltage and attempting to enumerate on the data line and then failing to enumerate 15 The method of claim 13 further comprising identifying output current capability of the EPS through the data line and wherein the selecting a higher current limit is respon sive to having identified the capability of the EPS 16 The method of claim 15 further comprising determining that the data line is sufficiently floating or undriven prior to the driving 17 The method of claim 13 further comprising charging the battery using current drawn from the power line into an input node of a battery charging circuit and sensing a voltage at the input node and wherein the driving the power line includes overdriving the power line by an amount that is in relation to the sensed voltage 18 The method of claim 13 further comprising charging the battery using current
8. indicator circuit coupled to the data line to indicate that the power converter can provide said current above the predetermined threshold 23 An electronic device comprising a communications interface to be coupled to a portable device the interface having a data line and a power line a power converter circuit having an output coupled to the power line to provide current to the coupled portable device for charging a battery of the portable device a signal conditioning circuit having a signal input coupled to the output ofthe power converter an output to provide a feedback input signal and a control input and control circuitry having an input coupled to the data line to receive a control signal and an output coupled to the control input to adjust the feedback input signal in response to the control signal 5 5 20 25 40 45 50 55 60 65 14 24 The electronic device of claim 23 wherein the commu nications interface comprises aconnector through which the data and power lines pass to receive a mating and detachable connector that is at an end of a cable 25 The electronic device of claim 23 further comprising an indicator circuit coupled to the data line to indicate that the power converter can provide said current above a predetermined threshold 26 An electronic device comprising a communications interface to be coupled to a portable device the interface having a data line and a power line
9. the first controller drives the data line by signaling a predetermined code or in essence a control signal on the data line where this code indicates that the battery charging circuit is drawing a higher current level On the EPS side the second controller recognizes or decodes this predetermined code and then changes the feedback input signal ofthe voltage regulator function in accordance with the decoded code to compensate for the voltage drop in the communications interface The above summary does not include an exhaustive list of all aspects ofthe present invention It is contemplated that the invention includes all systems and methods that can be prac ticed from all suitable combinations of the various aspects summarized above as well as those disclosed in the Detailed Description below and particularly pointed out in the associ ated claims Such combinations may have particular advan tages not specifically recited in the above summary BRIEF DESCRIPTION OF THE DRAWINGS The embodiments ofthe invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements It should be noted that references to or one embodiment of the invention in this disclosure are not necessarily to the same embodiment and they mean at least one FIG 1 illustrates different scenarios of a PD coupled to an EPS FIG 2 is a circuit schema
10. 8 350 522 B2 15 a predetermined amount of current can be sourced through a power line of the interface detecting that at least the predetermined amount of current is being sourced from a power converter circuit in the electronic device through the power line deriving a feedback input signal to the power converter circuit from the data line when at least the predeter mined amount of current is being sourced from the power converter circuit and deriving the feedback input signal from the power line when less than the predetermined amount of current is being sourced from the power converter circuit 32 The method of claim 31 further comprising indicating through the data line that the electronic device is ofatypethat can compensate for power line voltage drop in the communications interface 33 A method in an electronic device for supplying current to an external portable device comprising 5 15 16 indicating through a data line of a communications inter face that is coupled to the portable device that a prede termined amount of current can be sourced through a power line of the interface applying an analog scaling parameter to an output of a power converter circuit to derive a feedback input signal for the power converter circuit decoding a control signal received through the data line from the portable device and adjusting the analog scaling parameter based on the decoded control signal 34 The method o
11. AMOd INS3IX3 LY US 8 350 522 B2 Sheet 6 of 7 Jan 8 2013 U S Patent 97914 gi S3 TIOMLNOCO 3dIisS Sd3 40853020 21901 m A M3d093d NOLLVSN3d WOO LN38fIO LAS NOILYSNAd WOO 9SU9 Ul A ASNAS SNQA jno ul 19313Q QI 110 41 LN33800 0949 NI ONIONVHO S3183ANOO M3MOd Au311V8 01 YOLVYANSD 39310 YAMOd 1 66 00044 81 Sd3 US 8 350 522 B2 Sheet 7 of 7 Jan 8 2013 U S Patent AYSLLVE OL 6 U3 TIOHLNOO 1415 44 1INOUIO ONIOUVHO no 11 8 ul A 0 04 lt 2 ld 81 d3 MOSS300Md Ly NOILVSN3d WOO 310 N34 u 9j NI YS LYSANOO MAMOd YOLVYANAD QI 39unos YAMOd IVNSA3LX3 US 8 350 522 B2 1 EXTERNAL POWER SOURCE VOLTAGE DROP COMPENSATION FOR PORTABLE DEVICES FIELD An embodiment of the invention relates to portable devices such as smart phones and techniques for powering the portable device using an external power source such as a Universal Serial Bus USB power adapter Other embodi ments are also described BACKGROUND A portable device PD such as a smart phone a laptop or notebook computer and a cellular handset just to name a few is of course battery operated and therefore needs to be coupled to an external power source EPS to charge the battery Typic
12. E INTERFACE IS AVAILABLE E G SUFFICIENTLY FLOATING AND OR Lpo OF THE DATA LINE UNDRIVEN IS NOT AVAILABLE ENABLE THE DATA LINE TO BE DRIVEN SO AS TO CHANGE THE VOLTAGE AT A DATA LINE SENSE POINT IN THE EXTERNAL POWER SOURCE RAMP UP THE CURRENT LIMIT OF BATTERY CHARGER FOR DRAWING CURRENT FROM THE POWER LINE TO THE DETERMINED EPS MAXIMUM FIG 3 U S Patent Jan 8 2013 Sheet 4 of 7 US 8 350 522 B2 EXTERNAL POWER SQURCE START DETECT THE AMOUNT OF DC CURRENT BEING SOURCED BY A POWER CONVERTER THROUGH THE INTERFACE SELECT DATA LINE SENSE SELECT POWER LINE POINT TO PROVIDE OUTPUT SENSE POINT TO PROVIDE VOLTAGE FEEDBACK TO OUTPUT VOLTAGE FEEDBACK THE POWER CONVERTER TO THE POWER CONVERTER RESULT POWER CONVERTER INCREASES ITS OUTPUT VOLTAGE RELATIVE TO WHEN THE FEEDBACK IS FROM THE POWER LINE SENSE POINT THEREBY COMPENSATING FOR IR DROPS IN THE POWER LINE OF THE COMPUTER PERIPHERAL INTERFACE FIG 4 US 8 350 522 B2 Sheet 5 of 7 Jan 8 2013 U S Patent L8 S SIs 194130 v8 31901 TOULNOO YATIONLNOO 44005 3dIS dd J 6 3SN3S 39VLIOA al NOILVSN3d WOO Sd3 11 OL n ONIOHVHO 0 LINDY A3114 8 ul 0 dd lt 81 01901 L NV TIOULNOO Y30940 3115593 NOILVSNAd NOO 919 3 18VIYA ul qj 110 ul H3183ANOO 4 110 ul YOLVYANAD Al 3ounos Y
13. IG 7 depicts yet another embodiment of the invention where in this case the PD 10 has a pair of switches that are to be activated by the controller 3 to connect or in this example short the D and D pins of the communications interface to the power and return pins labeled here as Vbus and ground respectively The controller 3 after having determined that voltage drop compensation may be needed on the Vbus line e g in response to or just prior to signaling a higher current limit to the battery charging circuit 26 will activate the pair of switches so that in effect a remote output sense circuit is created for providing feedback to the voltage regulator in the power converter This is achieved by using a difference ampli fier 47 having its inputs coupled to the data lines D D respectively and its output being one of two signals that are alternately provided to the feedback input of the power con verter 43 The output of the difference amplifier 47 is consid ered to be the remote sense input when the D D lines have been connected to the Vbus and ground lines in the PD side A selector provides the desired selection between the remote and local feedback inputs under control of the pro cessor 86 In particular in response to the processor 86 receiv ing an indication from the coupled PD 10 that there is a need for voltage drop compensation the selector is signaled to switch from the local sense to the remote sense this assum
14. PD SIDE PORTABLE 30 US 8 350 522 B2 Sheet 1 of 7 Jan 8 2013 U S Patent HJTIOHINOO ZI 6 Sd3 6 0 30 3d 3 18VLUOd H3 gl US 8 350 522 B2 Sheet 2 of 7 Jan 8 2013 U S Patent GL H3TIOHLNCO 014 3dIs Sd3 OL 8 0 39IA3G 10 05 318viHOd TVNH3LDXGI I I I I I I 1 1 1 1 1 I gS i BE M3TIOMINOO 3dIS Od I I I I I I I I 80 LINDYIO SLInO3IO 3AIHOSSAO O A YAMOd Y3H10 ONY heri nis ul AMALLVE OL AHSIIVS 300030 INIOd I Ss BEST 9 72 1NIOd 3SN3S HJMOd gu pe LX aay VIVO Gz AHd a YOLVYANIO btao 1 304008 YAMOd TVNHALDG 02 YOLOANNOO LL HOLOANNOO 22 FAIS 391430 3 18VIHOd GN3318VO U S Patent Jan 8 2013 Sheet 3 of 7 US 8 350 522 B2 PORTABLE HOST DEVICE 31 STOP IF THEREIS CHECK POWERLINE OF COMPUTER n PERIPHERAL INTERFACE FOR SUFFICIENT pig CHARGING A BATTERY OF THE 53 DEVICE ATTEMPT TO ENUMERATE ON A DATA LINE ee D D OF THE INTERFACE 2 IF CANNOT ENUMERATE THEN ASSUME THE INTERFACE IS CONNECTED TO A DEDICATED POWER ADAPTER UNIT DECODE THE ID OF THE EXTERNAL POWER SOURCE THAT IS CONNECTED TO THE INTERFACE DETERMINE MAX CURRENT CAPACITY OF THE EXTERNAL POWER SOURCE CHECK WHETHER THE DATA LINE OF TH
15. US008350522B2 a2 United States Patent 10 Patent No US 8 350 522 B2 Johnson 45 Date of Patent Jan 8 2013 54 EXTERNAL POWER SOURCE VOLTAGE 2005 0174094 Al 8 2005 Purdy et al DROP COMPENSATION FOR PORTABLE 2006 0015757 Al 1 2006 Tupman et al DEVICES 2006 0181241 AI 8 2006 Veselic 2007 0046268 Al 3 2007 Irie 2007 0108938 1 5 2007 Veselic 75 Inventor Timothy M Johnson San Jose CA 2008 0259654 Al 10 2008 Huynh et al US 2008 0278132 Al 11 2008 Kesterson et al 2009 0102429 AI 4 2009 Xu et al 73 Assignee Apple Inc Cupertino CA US 2009 0189569 7 2009 Hsu et al 2009 0261786 Al 10 2009 Hsu et al Notice Subject to any disclaimer the term of this A 2 ee eal patent is extended or adjusted under 35 U S C 154 b by 424 days FOREIGN PATENT DOCUMENTS EP 1198049 Al 4 2002 21 Appl No 12 721 223 WO WO 2004075039 Al 9 2004 22 Filed 10 2010 OTHER PUBLICATIONS PCT Invitation to Pay Additional Fees and Where Applicable Pro 65 Prior Publication Data test Fee for PCT US2011 026461 mailed May 16 2012 PCT International Search Report and Written Opinion dated Sep 20 US 2011 0221604 1 15 2011 2012 International Application No PCT US201 1 026461 Interna tional Filing Date Feb 28 2012 21 pages 51 Int CI 01 10 44 2006 01 cited by examiner H01M 10 46 2006 01 52 USCI sonata iue 320 107 Primary Examiner Edward Tso 58 Field of Classification Searc
16. a line The first controller may be configured to recognize several different current limits which may be those of different types of EPSs that can be coupled to the PD Once the controller has determined that the EPS has a higher current limit as com pared to a lower one it may signal this information to the battery charging circuit which can then increase the current it draws from the power line e g up to the higher limit To compensate for the greater voltage drop caused by the increased current the first controller may drive the data line so as to change the dc voltage ofthe data line For example as the voltage at the input of the battery charging circuit drops due to increasing load on the power line the voltage on the US 8 350 522 B2 3 data line is actively raised in lock step e g in a linear rela tionship a one to one in relationship or in a non linear rela tionship The changing dc voltage on the data line in turn adjusts the feedback input signal of the power converter to in a sense emulate a lower voltage at the output of the power converter so that the closed loop voltage regulator function of the power converter responds by for example increasing its duty cycle to thereby raise its regulated dc output voltage in accordance with its normal feedback control loop process Thus the EPS compensates in a direct manner for the voltage drop that occurs through the communications interface In another embodiment
17. ally a PD has a battery charging circuit that draws current from a power pin power line of a communi cations interface connector of the device For example the current needed to charge the battery may be drawn from the Vbus pin of a Universal Serial Bus USB connector while the latter is connected to a USB power adapter orto a desktop personal computer s high power USB port The USB connec tor also has a data pin data line more specifically a pair of differentially driven data lines used to primarily transfer data rather than power between the PD at one end and another computing device that is connected to the other end of a USB cable As PDs evolve with greater power consumption and larger battery capacity the amount of current drawn from the EPS while charging the battery rises for instance to one ampere or more In addition industry recommended requirements for communications interfaces that also are power conduits place an upper limit on the dc voltage of the power line that is close to the battery voltage For example a Vbus specification of 5 Volts dc at the output port of the USB power adapter circuit is close to the cell voltage of a fully charged lithium polymer cell namely about 4 2 Volts SUMMARY A battery charging circuit of a PD needs sufficient head room i e voltage between its output and input ports to operate properly and thereby fully charge the battery This headroom however is expected to shrink a
18. e battery charging circuit is substantially less e g 4 9 Vdc then the compensation value that is generated may rep resent the difference namely 0 1 Vdc This value would then be subtracted from the sensed voltage at the output of the power converter in the EPS side by the summing circuit thereby providing a feedback input signal that has been adjusted downward this causes the power converter to respond by boosting its output voltage appropriately or in proportion to the compensation value In addition to signaling the need for voltage drop compen sation and the measured input voltage at the battery charging US 8 350 522 B2 11 circuit the communications interface and mainly the D and D data lines may be used by the compensation processor 86 control logic 86 to send information to the PD 10 by sig naling at least one of the following attributes pertaining to the EPS 18 manufacturer name date of manufacture maximum output power capability specified power line voltage serial number and authentication value This information may be signaled using a different protocol than that used by a core circuit of the EPS 18 to perform core communications with the coupled PD 10 For instance the EPS 18 may be a desktop computer that uses a USB protocol over the communications interface for its core communications with a coupled periph eral device whereas the control logic 86 uses I2C to commu nicate with the PD side controller 3 F
19. e cable assembly 12 The desktop computer may be powered by being plugged into an AC wall outlet as shown In another instance the PD 10 is coupled to the EPS 18 being an AC wall power adapter unit In yet another instance not shown the EPS 18 may be a cigarette lighter adapter unit In one instance the cable assembly 12 has a PD side cable connector 11 that is designed to mate with a built in connector of the PD 10 not shown in addition to an EPS side cable connector 13 The latter would be pluggable with a mating connector built into the EPS 18 The cable assembly 12 may for example be in accordance with a computer peripheral communications interface specification such as Universal Serial Bus USB or other suitable communications interface The communications interface may also be referred to as a communications bus Note that in another instance the cable assembly 12 while having the PD side connector 11 has no corresponding EPS side connector 13 In that case the wires of the cable assembly 12 may be hardwired into circuitry inside a housing of the EPS 18 Turning now to FIG 2 a circuit schematic of EPS side and PD side controller circuitry that achieve voltage drop com pensation in accordance with an embodiment of the inven tion is shown The EPS 18 contains an EPS side controller 15 that interacts with a PD side controller 3 located in the PD 10 Beginning with the PD 10 a PD side connector 20 which as suggested above
20. e said current and on that 20 25 30 35 40 45 50 55 60 65 12 basis drive the first pin to stimulate the power converter circuit to raise voltage on the second pin 2 The portable device of claim 1 wherein the controller is to raise a current limit of the battery charging circuit after starting to drive the first pin to stimulate the power converter circuit 3 The portable device of claim 1 wherein the connector is a computer peripheral serial bus connector 4 The portable device of claim 3 wherein the controller is to determine whether the connector is coupled to the EPS by checking for sufficient voltage on the second pin and by attempting to enumerate on the bus connector 5 The portable device of claim 3 wherein the controller is to determine whether the connector is coupled to the EPS by checking for sufficient voltage on the second pin and by attempting and then failing to enumerate on the bus connec tor 6 The portable device of claim 1 wherein the controller is to determine whether the connector is coupled to the EPS by decoding an indication on the first pin that indicates a current limit of the EPS 7 The portable device of claim 1 wherein the controller is to drive the first pin by raising dc voltage of the first pin as an inverse function of dc voltage at the input of the battery charging circuit 8 The portable device of claim 1 wherein the controller is to drive the first pin by signali
21. ection undervoltage protec tion OVP UVP switch circuit 27 is also present contribut ing further to the voltage drop in the communications inter face The battery charging circuit 26 may have several functions at least one of which is to charge a battery not shown that serves as a portable power source of the PD 10 which is typically integrated within the PD 10 housing not shown The battery charging circuit 26 regulates the amount of cur rent it feeds to the battery drawn from the power line P through its input port so as to efficiently charge the battery to its full state This may occur at variable current levels while monitoring battery voltage In one instance the battery charg US 8 350 522 B2 5 ing circuit 26 is capable of properly charging a lithium poly mer rechargeable cell having a nominal voltage of 3 7 volts and a fully charged voltage of about 4 2 volts This of course is an example only as other types of battery chemistries and associated battery charging circuitry can be used instead In one embodiment the PD device 10 and in particular all of its other power supplies i e other than the ones that may be deemed part of the battery charging circuit 26 itself may be powered directly from the battery terminals when the EPS 18 is not present In other words the battery charging circuit 26 in this case acts like a diode between its in and out termi nals when the EPS 18 is present the battery charging circ
22. ed between the data lines D1 D2 by a switch S1 An EPS identification decoder 24 is provided that evaluates the digitized values or codes on the data lines to make the determination as to the type of EPS 18 that is coupled to the PD 10 The code may be generated by an EPS identification generator 41 inside the EPS 18 For example the EPS 18 may be identified as an AC wall adapter unit that conforms with the USB specification capable of providing 5 volts dc on the power line P at up to 1 ampere of current I The EPS identification decoder 25 may have previ ously stored codes for several different types of EPS 18 It may recognize the coupled EPS 18 by comparing the code that it reads on the data lines D1 D2 to those previously stored codes For various EPS identification techniques see U S Patent Application Publication No 2006 0015757 of Tup man et al In one instance the codes may be generated in the EPS 18 using pull up and pull down resistors on one or both of the data lines D1 D2 such that a range of different max or rated currents can be identified For example the following table can be programmed into the EPS identification decoder 24 Current Capability D1 D2 100 mA 5 Volts 0 Volts 500 mA 2 5 Volts 0 Volts 1A 2 5 Volts 2 5 Volts 5 40 45 60 65 6 where each data line in this example can have any one ofthree different states here zero 0 V 2 5V and 5V allowing for up to nine different comb
23. ed up on the EPS side for instance to encode data and clock information These commands are interpreted or recognized by the processor 86 on the EPS side as signaling that voltage drop compensation on the communications bus is needed Note that in this case the PD side controller 3 may be viewed as the master of the communications session on the data lines while the processor 86 on the EPS side is considered the slave The PD side controller 3 as a master signals a code on the data lines D D that represents the voltage at the input of the battery charging circuit 26 that it has sensed or measured This code is then recognized by the EPS side of compensation decoder and control logic 86 as also an indication that voltage drop compensation is needed for the Vbus and ground lines of the communications interface The control logic 86 thus receives a measure of the de voltage at the input of the battery charging circuit 26 and responds by generating an error or compensation value that is then converted to analog form by the digital to analog converter DAC A summing circuit provides the feedback input signal fb_in to the power con verter based on a combination of the output of the power converter and the compensation value generated by the con trol logic 86 For instance if the specified output voltage on Vbus is known to the control logic 86 as being 5 Vdc yet the code received from the PD side indicates that the input volt age ofth
24. emulates a lower output voltage for the voltage regulator in the EPS resulting in the voltage on the power line P increasing so as to com pensate at least in part and in some cases fully the voltage drop that would otherwise occur on the power line P espe cially at an elevated current I Note that if the max available current as determined by the EPS identification decoder 24 is lower than a predetermined threshold then the voltage drop in the communications inter face may not be significant such that the data line need not be driven to stimulate the power converter circuit 43 of the EPS 18 This low current mode may be defined as switches S2 S3 both being open On the EPS side the data and power lines are available therein as part ofthe communications interface as shown The power line is fed by the output port of the power converter US 8 350 522 B2 7 circuit 43 which may include a voltage regulator function that regulates the dc voltage at the output port at a given specification e g 5 volts dc for a typical USB specifica tion In most cases the power converter 43 includes a switch ing voltage regulator that converts an ac or dc input voltage to the specified dc output using a feedback input signal in derived from its output The feedback input signal is part ofa feedback control loop of the regulator which enables the regulator to maintain its output voltage at a steady level regardless of variations at the inpu
25. ent from the power line up to the determined max current limit of the EPS To achieve voltage drop compensation the PD side pro cess of FIG 3 can be accompanied by an EPS side process which is depicted in FIG 4 In the EPS the current I being sourced by the power converter through the power line which is rising due to the battery charging circuit drawing more current is monitored operation 71 As explained above this may be done using a direct sensing approach e g a current sense resistor in series with the power line or an indirect approach e g measuring the pulse width modulation duty cycle of a switching voltage regulator and comparing to pre viously learned patterns and their associated current levels When the detected current is greater than a previously determined threshold operation 72 the data line 1s selected to derive the feedback input signal for the voltage regulator operation 75 When the detected current is less than the previously determined threshold operation 73 the power line or power converter output is selected to derive the feed back input signal operation 77 The result is that the feed back controlloop ofthe power converter responds by increas ing its output voltage relative to when the feedback is from the power line sense point thereby compensating in full or in part for the I R drops in the power line US 8 350 522 B2 9 Turning now to FIG 5 another embodiment of the inven tio
26. es that the D D lines have been connected to the Vbus and ground lines in the PD side As the remotely sense voltage is less than the locally sensed voltage due to the voltage drop through the communications interface cable assembly the output of the power converter 43 will be automatically boosted in proportion thereby compensating for the voltage drop While certain embodiments have been described and shown in the accompanying drawings it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention and that the invention is not limited to the specific constructions and arrangements shown and described since various other modifications may occur to those ofordinary skill in theart For example although the PD 10 depicted in FIG 1 is a smart phone the invention is applicable to other types of PDs e g laptop notebook com puters dedicated navigation devices digital media players cellular phones and personal digital assistants The descrip tion is thus to be regarded as illustrative instead of limiting What is claimed is 1 A portable electronic device comprising a connector having a first pin and a second pin a battery charging circuit having an input coupled to receive current through the second pin to charge a bat tery and a controller to determine whether the connector is coupled to an external power source EPS having a power con verter circuit that can provid
27. f claim 33 further comprising indicating through the data line that the electronic device is ofatypethat can compensate for power line voltage drop in the communications interface
28. h 320 107 74 Attorney Agent or Firm Blakely Sokoloff Taylor amp 320 112 114 127 128 137 Zafman LLP See application file for complete search history 57 ABSTRACT 56 References Cited A portable electronic device has a connector with a first pin U S PATENT DOCUMENTS and a second pin and a battery charging circuit having an Vues Rearea input coupled to receive current through the second pin to Aa enr etal charge a battery of the device The portable device also has a 5 532 524 A 7 1996 Townsley et al f a 5 783 927 A 7 1998 Chen i55 reete 320 110 Controller to determine whether the connector is coupled to an 5 841 996 A 11 1998 Nolan et al 710 305 external power source EPS having a power converter circuit ud em d that can provide the current The controller on that basis eller et al i 6300743 Bl 10 2001 Patino et al drives the first pin to stimulate the power converter circuit to 6 681278 1 2004 Jakl raise voltage on the second pin Other embodiments are also 7 421 594 B2 9 2008 Nakajima et al described and claimed 7 421 604 9 2008 Mimberg 2004 0164707 Al 8 2004 Veselic et al 34 Claims 7 Drawing Sheets CABLE END PORTABLE DEVICE SIDE 22 E x GENERATOR 35 8 SENSE POINT POWER ES In POWER _ CONVERTER in out EPS SIDE CONTROLLER 15 CONTROLLER 3 OVERDRIVE CIRCUIT 28
29. ily fully the voltage drop that is occurring in the communica tions interface Several possibilities for the second controller to change the feedback input signal responsive to the data line i e in response to actions taken on the data line by the first controller are given here In one embodiment the first controller PD side deter mines whether its connector is coupled to the EPS by check ing for sufficient voltage on the power pin and then attempting a bus device enumeration process through the connector If the attempt to enumerate fails then this may be an indication that a particular type of EPS is present e g an AC power adapter unit a cigarette lighter adapter unit which is suitable to provide a larger current needed to more quickly charge the battery Other techniques for making this determination can be used The first controller may also determine a current limit or maximum output current of the EPS For instance the first controller can decode an indication or signal on the data line to recognize this current limit The indication may be for example an analog code defined by a selected combination of one or more resistors that are coupled to the data line inside the EPS Some EPSs would have greater current capability than others this may be indicated by the analog codes present on their data lines Alternatively other techniques for indicat ing the current capability may be used e g a digital code on the dat
30. inations of current capability to be recognized In identifying the EPS 18 the EPS identification decoder 24 may indicate the maximum current capacity of a power converter circuit 43 that is to deliver the current I This infor mation can be specified to the battery charging circuit 26 which in turn can increase its current draw on the power line P to the specified limit Note that since there may be several different types of EPS 18 that can be coupled to the PD 10 where each type of EPS may have a different current limit the EPS identification decoder 24 will enable the battery charg ing circuit 26 to adapt to the different current limits Thus the consumer or end user of the PD 10 can be assured that the battery will be charged at the fastest possible rate regardless ofthe type of EPS 18 to which he has connected his PD 10 It should be noted that references here to maximum avail able current or current capacity are used generically to also cover instances where the power converter circuit 43 of the EPS 18 is identified using its corresponding maximum power or power capability The PD side controller 3 and in particular its control logic 30 on the basis of having determined that the connector 20 is coupled to the EPS 18 and that the max current or available power from the EPS 18 is greater than a given threshold may signal the battery charging circuit 26 that it may increase its current draw e g to enable it to charge
31. instance several ranges can be defined for the input voltage e g nominal low and very low with their respective associated command codes that translate into corresponding changes to the feedback input signal of the voltage regulator in the EPS 18 The command codes sent to the EPS 18 over the data line D are decoded by compensation decoder and control logic 86 The EPS side controller 15 in this case has an analog signal conditioning circuit e g a variable scale circuit 87 having a signal input coupled to the output of the power converter 43 an output to provide the feedback input signal and a control input Each code can represent a different type of condition ing e g amount of scaling that is to be applied to the sensed power line voltage to derive the feedback input signal For instance the code for battery charging input voltage being very low meaning that the current draw is particularly high could translate into a greater attenuation of the sensed power line voltage than the low code this would cause the power converter 43 to raise its output voltage more for the very low code than for the low code As another example when the code received from the PD 10 indicates that the current I is low or the battery charger input voltage is within anominal specified range for the communications interface then the variable scale circuit is signaled into a default setting thereafter when a subse
32. line operation 55 Ifthe EPS has been identified as one that can source more than a predetermined amount of current through the power line of the interface then a decision can be made to increase the current limit of the battery charging circuitry If the pre determined amount of current is sufficiently great as to be expected to cause a significant voltage drop in the interface when operating at or above the predetermined amount of current e g 1 Ampere then voltage compensation will be needed on the power line Therefore the data line of the interface is checked to first ensure that it is not being driven or is sufficiently floating operation 57 The process stops ifthe data line is not available the data line cannot be driven to stimulate the EPS to compensate for the expected voltage drop Ifthe data line is available then the compensation process can continue with enabling the data line to be driven so as to change the dc voltage at the data line sense point in the EPS and the voltage regulator feedback input signal in the EPS operation 59 In other words the dc voltage on the data line can now be forced to change so as to cause the feedback input signal to change in a desired manner e g continuously vari able as a function of the dc voltage at the input of the battery charging circuit or in one or more discrete steps The current limit of the battery charger circuit can now be ramped up drawing increasingly more curr
33. n data line sense point where the combination of the overdriven data line D1 and the amount of scaling applied by the scale circuit 45 result in the feedback input signal becoming smaller thereby causing the closed loop voltage regulator function of the power converter 43 to respond by appropriately raising its output voltage When current I is low switch S4 is at the local position power line sense point where the scale circuit 44 governs how the feedback input signal is derived Thus the EPS side controller 15 changes the feedback input signal of the power converter circuit 43 responsive to detecting that the current I is above a predetermined threshold where the power converter circuit 43 in response raises its output voltage to compensate for the voltage drop in the communications inter face with the PD 10 It should be noted that the current detection circuit 49 may be implemented in several different ways For example a series sense resistor on the power line P to which are coupled associated analog and digitizing circuitry may be used to give a directed or sensed reading In contrast the current I could detected indirectly e g estimated by monitoring the pulse with modulation duty cycle ofthe switching voltage regulator function of the power converter circuit 43 and then inferring the load current I using a previously determined look up table in view ofthe voltage at the input ports ofthe power converter 43 FIG 3 is a flow
34. n is shown where the PD side controller 3 sends a coded command or control signal to the EPS side over the data line D for purposes of requesting and obtaining voltage drop compensation This is in contrast to the embodiment of FIG 3 and FIG 4 where the controller 3 adjusts the dc voltage on the data line to merely reflect the fact that the voltage at the input of the battery charging circuit has dropped The coded command is generated by a compensation coder 82 in response to a decision made by control logic 84 The latter is informed of the EPS current limit by an EPS identification detect circuit 81 which may be similar to the combination of the ADC 25 and EPS identification decoder 24 of FIG 1 When the EPS has a higher current limit the control logic 84 may decide to signal the EPS that voltage drop compensation is needed by requesting the compensation coder 82 to drive the data line D with the appropriate command code The control logic 84 may then signal the battery charging circuit 26 that it may now increase its input current up to the EPS current limit Note that there may be several predetermined command codes from which one or more can be selected The selection may be a function of a real time measure of the dc voltage at the input of the battery charging circuit A voltage sense circuit 83 may be used to sample and then digitize this input voltage which is then processed by the control logic 84 to make the selection For
35. ng a predetermined code on the first pin 9 The portable device of claim 8 wherein the code indi cates that the battery charging circuit is drawing a higher current level 10 The portable device of claim 1 wherein the controller is to measure dc voltage at the input of the battery charging circuit and to drive the first pin by signaling a code that represents the measured dc voltage 11 A portable electronic device comprising aconnector having a first pin a second pin a third pin and a fourth pin a first switch to connect the first pin and the second pin when activated a second switch to connect the third pin and the fourth pin when activated a battery charging circuit having an input coupled to receive current through the second pin to charge a bat tery and return current through the fourth pin and a controller to determine whether the connector is coupled to an external power source EPS having a power con verter circuit that can provide said current and on that basis activate the first and second switches to enable the power converter circuit to compensate for voltage drop on the second pin 12 The portable device of claim 11 wherein the controller has a port coupled to one of the first and third pins for determining output power capability of the EPS 13 A method in a portable electronic device for charging a battery of the device comprising detecting that the portable electronic device is connected to an
36. quent code is received from the PD 10 indicating that the current 11 now high or the battery charger input voltage dropped below its nominal range then the variable scale circuit 87 is signaled into a plus setting i e a different scale factor is applied to the power lines sense point to change the feedback input signal so as to emulate a condi tion where the power converter output is lower than it actually is The latter will then cause the voltage regulator to raise its output in accordance with the changed feedback input signal thereby compensating for the voltage drop through the inter face FIG 6 is a circuit schematic of controller circuitry in the EPS and in the PD in accordance with yet another embodi ment of the invention Beginning with the PD side the con troller 3 has at least one and in this case a pair of I O ports that are connected to the one or more data lines in this case D D which are a differential signaling pair of the com 20 25 30 35 40 45 50 55 60 65 10 munications bus The controller 3 uses its I O ports as input to detect or identify the EPS 18 e g as part of a bus enu meration process and communicate with the EPS side pro cessor 86 The controller 3 uses its I O ports as output to send command codes to the processor 86 in response to having determined that there may be a need to do so given the relatively high current draw expected or actually occurring on
37. re cost of the inter face In one embodiment the voltage drop compensation tech nique has two aspects On the PD side ofthe communications interface a first controller is provided that determines whether a connector which includes at least a first pin e g data pin or data line and a second pin e g power pin or power line is coupled to an EPS having a power converter circuit The coupling may include a communications inter face cable e g a USB cable The controller determines whether the power converter circuit can provide a certain amount ofcurrent through the second pin to a battery charg ing circuit in the PD On that basis the controller drives the first pin of the connector so as to stimulate the power con verter circuit to raise its output voltage This results in the voltage on the second pin of the connector rising and thereby compensating for the voltage drop on the power line On the EPS side ofthe communications interface a second controller in the coupled EPS responds to the driven first pin by changing a feedback input signal of a dc voltage regulator in the power converter circuit This signal may be an input to anerroramplifier ofthe voltage regulator with the other input being a reference signal representing the desired or regulated output voltage The change in the feedback input signal causes the voltage regulator to raise its regulated dc output voltage slightly enough to compensate for not necessar
38. s PDs demand more current to charge their larger batteries more quickly due to the voltage drop I R on the dc path ofthe power line ofthe communications interface between the EPS and the input port ofthe battery charging circuit This voltage drop which is due to the R having contributions from cable resistance and printed circuit board components such as overvoltage undervoltage switches flexible wire circuits and ferrites may leave insufficient headroom for the battery charging circuit at high current T An embodiment of the invention is a technique that com pensates for the power line voltage drop in a communications interface between a power converter circuit of an EPS and the battery charging circuit of a PD In one instance the tech nique helps maintain sufficient headroom for the battery charging circuit while remaining within the bounds of the USB specification for Vbus on the power line The technique may also be applicable to other communications interfaces used by PDs The technique may work to compensate for relatively long cables that can connect the EPS to the PD Further the technique may decouple the design of the inter 20 25 30 35 40 45 50 55 60 65 2 face so that less effort would be needed to reduce I R drops e g higher performing lower Rds on transistor switches may not be needed multiple inductors in parallel may not be needed thereby reducing the manufactu
39. t ports and changes in the load at the output port To achieve voltage drop compensation the EPS side con troller 15 changes the feedback input signal fb in responsive to the data line D1 In one embodiment of the invention this is achieved using an analog multiplexer circuit composed of a switch S4 having an output that provides the feedback input signal and at least two different scale circuits 44 45 whose inputs are coupled to the output ofthe power converter 43 and the data line D1 respectively Control logic 47 is provided to receive a measure of the current I being sourced into the power line P This measure of the current I is obtained using a current detect circuit 49 The control logic 47 has an output that is coupled to the control input of the analog multiplexer control of the switch S4 to alternately select between the scale circuit 44 local or power line sense point and scale circuit 45 remote or data line sense point The scale circuits 44 45 may be fixed at the time of the manufacture of the EPS side controller 15 based on an understanding of the expected voltage change presented on the data line at higher power line currents When the PD 10 is drawing in excess of a predetermined threshold amount ofcurrent I the control logic 47 may decide that the analog multiplexer be switched from the power line sense point to the data line sense point In other words when current I is high switch S4 is at the remote positio
40. the battery faster At that point voltage drop compensation may be needed so that the control logic 30 decides that the data line D1 needs to be driven in a way that stimulates the power converter circuit 43 to raise its output voltage on the power line P Several ways in which this can be achieved are described First FIG 2 illustrates the embodiment where the data line D1 is overdriven That is the dc voltage on the data line is actively raised e g as a continuous inverse function ofthe dc voltage at the input of the battery charging circuit 26 In the example circuit shown here this is achieved by the control logic 30 commanding the switches S2 S3 to close and S1 to switch to the data line D1 As the current draw on the power line P increases and the voltage at the input of the battery charging circuit 26 decreases due to the voltage drop caused by the parasitic components illustrated as resistors and induc tors as well as the OVP UVP switch circuit 27 this drop in the input voltage is sensed by the overdrive circuit 28 The latter may include an amplifier which is able to sense the voltage at the input when the switch S3 is closed The amplifier may be designed to have a gain such that when the switch S2 is closed the data line D1 is overdriven inversely proportional to the voltage at the battery charger circuit input As explained below this overdriving of the data line D1 is translated into a feedback input signal that
41. tic of controller circuitry in the EPS and in the PD that achieve voltage drop compensation in accordance with an embodiment of the invention FIG 3 is a flow diagram of operations that may be per formed in the PD FIG 4 is a flow diagram of operations that may be per formed in the EPS FIG 5 is a circuit schematic of controller circuitry in the EPS and in the PD in accordance with another embodiment of the invention FIG 6 is a circuit schematic of controller circuitry in the EPS and in the PD in accordance with yet another embodi ment of the invention FIG 7 is a circuit schematic of controller circuitry in the EPS and in the PD in accordance with yet another embodi ment of the invention DETAILED DESCRIPTION Several embodiments ofthe invention with reference to the appended drawings are now explained While numerous details are set forth it is understood that some embodiments of the invention may be practiced without these details In other instances well known circuits structures and tech niques have not been shown in detail so as not to obscure the understanding of this description 20 25 30 35 40 45 50 55 60 65 4 FIG 1 illustrates different scenarios of a PD 10 that is coupled to an EPS 18 for purposes of charging a battery not shown of the PD 10 Two instances are shown where in one instance the PD 10 is coupled to a desktop personal computer through a communications interfac
42. uit 26 supplies power to not just the battery but also all other power supply circuits ofthe PD 10 on the same power supply rail as shown in FIG 2 and when the EPS 18 is absent the battery charging circuit 26 is essentially an open circuit so that power supply rail is fed directly by the battery The battery charging circuit 26 may have the additional function of acting as a programmable current limiter to the power line For example it could limit the max current on the P line to 1 A pursuant to instructions from the control logic 30 and the EPS identification decoder 24 and distribute the 1 A as follows about 0 8 A for charging the battery and the rest about 0 2 A for running the other power supplies of the PD 10 The control logic 30 may have the intelligence to allocate the max current drawn on the P line differently depending on known power management algorithms The PD side controller 3 just as the EPS side controller 15 to be discussed below may be implemented as a combination of analog and digital hardwired circuitry and programmed data processing components that control the manner in which the voltage compensation process is conducted The PD side controller may be composed of the following functional unit blocks To determine whether the connector 20 is coupled to an EPS 18 the controller 3 has an analog to digital converter ADC 25 which digitizes the signals on the one or more data lines the ADC is in this case switch
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