Closed loop margin management for battery charging

Abstract

An electronic system can include a charged system and a charging system. The charged system can include a charger and a battery configured to be charged thereby. The charger can be configured to receive power from the charging system, which includes a power converter configured to supply power to the charger and a controller configured to control the power converter. The controller can be configured to receive feedback information from the charged system, including one or more voltages. The controller can be further configured to determine an output voltage compensation value for the power converter as a function of the feedback information, and to set an output voltage of the power converter as a function of the compensation value. The compensation value and the output voltage can be selected to maintain a preselected margin between a battery charge target voltage of the charger and a voltage supplied to the charger.

Description

BACKGROUND

[0001] Modern consumers employ a variety of personal electronic devices that are powered by batteries. As a general principle, it is desirable to charge these batteries as efficiently as possible. In some embodiments, such efficiency requirements can be enhanced. For example, it is becoming common for consumers to charge the batteries of one device from another battery-powered device. One example is wireless earphones (also known as "earbuds") that can be charged from a storage case that includes its own battery. Other examples include charging a smartphone, tablet, etc. from a laptop computer, or charging these and other devices, etc. from a portable power bank. In these applications, maximizing the charging efficiency of the charged device can improve the amount of charge that the charged device can receive, thereby extending its usable time, due to the limited amount of charge available in the charging device.

[0002] In some embodiments, charging a battery can include providing a constant current until the battery reaches a particular state of charge, and then providing a constant voltage until the battery reaches another particular state of charge. In the constant current phase, as the state of charge of the battery increases, the voltage required / supplied to drive the constant current will increase. In cases where the input voltage provided to the charger is significantly greater than the required battery charging voltage, significant inefficiencies can be introduced. However, providing a voltage that is less than that required to meet the battery charge curve can result in a longer charging time than necessary. Thus, what is needed in the art are systems and methods for maintaining the voltage supplied to a battery charger of a portable electronic device at a level that is sufficiently higher than the required battery target voltage to maintain a desired charging rate, but not so high as to introduce the above-mentioned inefficiencies. SUMMARY

[0003] An electronic system can include a charged system and a charging system. The charged system can include at least one battery and at least one charger configured to be charged by the at least one battery. The at least one charger can be configured to receive power from the charging system. The charging system can include a power converter configured to supply power to the at least one charger of the charged system and a controller configured to control the power converter. The controller can be configured to receive feedback information from the charged system, the feedback information including one or more voltages of the charged system. The controller can be further configured to determine an output voltage compensation value of the power converter according to the feedback information. The controller can be further configured to set an output voltage of the power converter according to the compensation value, wherein the compensation value and the output voltage are selected to maintain a preselected margin between a battery charging target voltage of the charger and a voltage supplied to the charger.

[0004] The powered system can include a plurality of batteries and a plurality of chargers. The one or more voltages of the powered system can include at least an input voltage of the at least one charger and an output voltage of the at least one charger. The powered system can further include at least one low dropout regulator or at least one switch coupled between an input of the at least one charger and at least one power contact of the powered system. The powered system can include one or more wireless earphones.

[0005] The charging system can further include one or more switches coupled between an output of the power converter and one or more power contacts of the charging system. The charging system can further include a power source configured to provide power to the power converter. The power source can be coupled to a battery within the charging system, or the power source can be coupled to an external power source through a wired and / or wireless connection.

[0006] A method of supplying power to a battery charger of a powered system for charging a battery of the powered system can include receiving feedback information from the powered system at a controller of a charging system, the feedback information including one or more voltages of the powered system. The method can further include determining, by the controller of the charging system, an output voltage compensation value of a power converter of the powered system configured to deliver power to the battery charger according to the feedback information. The method can additionally include setting, by the controller, an output voltage of the power converter according to the compensation value, wherein the compensation value and the output voltage are selected to maintain a preselected margin between a battery charging target voltage of the charger and a voltage supplied to the charger.

[0007] The powered system can include a plurality of batteries and a plurality of chargers. The one or more voltages of the powered system include at least an input voltage of the at least one charger and an output voltage of the at least one charger. Determining, by the controller of the charging system, an output voltage compensation value of a power converter of the powered system according to the feedback information can include determining whether data received from the powered system is valid. Determining, by the controller of the charging system, an output voltage compensation value of a power converter of the powered system according to the feedback information includes determining whether data received from the powered system is valid can further include setting a powered system state to one of a plurality of states in response to the feedback information. The compensation value can be selected from a plurality of predetermined compensation levels. The predetermined compensation values include a plurality of positive values, at least one negative value, and a zero value. The powered system can include one or more wireless earphones, and the powered system can include a charging case.

[0008] An electronic system may include: at least one battery; at least one charger configured to charge the at least one battery; and a power converter configured to deliver power to the at least one battery. The electronic system may also include means for regulating the output voltage of the power converter such that the output voltage is maintained above a preselection margin of a charging target voltage of the at least one charger. Attached Figure Description

[0009] Figure 1 A block diagram of a battery charging system that can employ closed-loop redundancy management is shown.

[0010] Figure 2 The graphs show the voltage and current associated with battery charging operations, including closed-loop redundancy management.

[0011] Figure 3 This demonstrates the use of closed-loop redundancy management. Figure 1 A high-level flowchart of the control system for the charging system.

[0012] Figure 4 This demonstrates the use of closed-loop redundancy management. Figure 1 A more detailed flowchart of the control system for the charging system.

[0013] Figure 5 A flowchart is shown for determining compensation in response to an error signal in a closed-loop redundancy management algorithm.

[0014] Figure 6 A series of voltage states and error signals of a system employing closed-loop redundancy management are shown.

[0015] Figure 7 A flowchart is shown for controlling a buck / boost converter in a charging system employing closed-loop redundancy management. Detailed Implementation

[0016] In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the disclosed concepts. As part of this description, for simplicity, some of the accompanying drawings of this disclosure are shown as block diagrams of structures and devices. For clarity, not all features of actual specific embodiments are described in this disclosure. Furthermore, the language used in this disclosure has been chosen for readability and guidance purposes and has not been selected to depict or limit the subject matter disclosed. Rather, the appended claims are intended for this purpose.

[0017] Various embodiments of the disclosed concepts are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements throughout the various figures. Reference numerals are repeated in the description for the sake of simplicity and clarity and matters of form and convention can be deemed to exist over and above the illustrative content disclosed. In the interest of clarity, not all aspects of the examples can be described. Additionally, the description can omit a discussion of well-known structures and devices and procedures in relation to the described aspects. Reference to “one” or “an” embodiment in the disclosure means at least one. A given figure can be used to illustrate more than one embodiment or category of features, and not all elements in a given figure can be required for a given embodiment or category. Where provided, reference numerals are used consistently throughout the drawings and the description to refer to the same or like elements. The drawings are not to scale and certain components can be exaggerated in scale or presented with an arbitrary shape or size for the sake of simplicity and clarity. Unless otherwise indicated, the drawings are not drawn to scale and the proportions of certain parts can be exaggerated for the sake of simplicity and clarity.

[0018] Figure 1 An example system 100 is shown that includes a charging device 110 that supplies power to a charged device 140. In the illustrated embodiment, the charged device 140 can include a pair of wireless earphones. The charging device 110 can be a charging case for those wireless earphones. The devices and techniques described herein are not limited to this particular application. Rather, they can be used in any application in which a controllable voltage is supplied to a battery charger and it is desirable to minimize inefficiencies associated with the difference between that controllable supply voltage and a battery charging target voltage.

[0019] Further reference is made to Figure 1 The charging device 110 can include a controller 112. This controller can be a microcontroller, microprocessor, or other suitable electronic control unit for directing the operation of other charging system components. The controller 112 can receive feedback from the charged device 140 that can be used to assist in controlling the charging process, as described further below. In the illustrated embodiment, the controller 112 receives feedback from the first earphone via feedback path 111 and from the second earphone via feedback path 113. In other embodiments, the controller 112 can receive feedback from any number of charged devices or systems, such feedback referenced in controlling the charging process, as described in greater detail below.

[0020] The controller 112 can be coupled to the power converter 114 and direct the operation of the power converter. The power converter 114 can convert a voltage received from the power source 116 to another voltage suitable for delivery to the charged system 140. In the illustrated embodiment, the converter 114 is a buck-boost converter, meaning that it is capable of providing an output voltage that steps up (boosts) (i.e., the voltage supplied to the charged system 140 is greater than the voltage supplied by the power source 116) or steps down (buck) (i.e., the voltage supplied to the charged system 140 is less than the voltage supplied by the power source 116). Many power converter topologies, including buck-boost and other topologies, and their underlying principles of operation are known to those skilled in the art. Any such converter can be used in conjunction with the teachings herein, as appropriate for a particular application.

[0021] The power converter 114 receives power from the power source 116. In the illustrated embodiment, the power source 116 can be a charger in a battery case of a wireless earphone set. Such a charger can be configured to deliver power to the power converter 114 from one or more power sources. Such power sources can include, for example, a battery internal to the charged system 110, a wired external power source connected to the charged system 110, or a wireless (inductive) power transfer source coupled to the charged system 110. The power source / charger 116 can also be configured to deliver power from a wired and / or wireless external power source to a battery contained within the charged system 110. In other embodiments, other types of power sources or combinations of power sources can be used as appropriate.

[0022] As noted above, the controller 112 directs the operation of the power converter 114. To do so effectively, the controller 114 can receive feedback corresponding to the output of the power converter 114. For example, the controller 112 can receive feedback corresponding to the output of the power converter 114 along with the feedback 115. The controller 112 can use this feedback to direct the charging operation, as described in greater detail below. The output of the power converter 114 can also be supplied to optional switches 122 and 124, which can be configured to selectively deliver power to the charged system 140. In the illustrated embodiment, two switches 122 and 124 are provided, each corresponding to one of the wireless earphones making up the charged system 140. However, in other applications, other numbers of switches can be provided as appropriate. These switches can be used to selectively connect and disconnect the loads to be charged as appropriate (e.g., as determined by the controller 112).

[0023] Switches 122 and 124 can be coupled to contacts 132 and 134, respectively. These contacts can comprise conductive elements in charging system 110 that are configured to come into contact with corresponding conductive elements in charged system 140. For example, if charging system 110 is a charging case for wireless earbuds, there can be metal contacts in the case that are configured to physically (and thus electrically) contact corresponding metal contacts on the earbuds themselves. The resulting current path can provide a path for charging the batteries in charged system 140. Additionally, in some embodiments, these contacts or additional electrical contacts can provide a path from the charged system to controller 112 for a feedback signal. In other embodiments, the feedback path can be provided by an alternative physical path, such as a wireless communication path using Bluetooth, WiFi, inductive coupling, or other suitable wireless communication medium.

[0024] In the example shown, as noted above, charged system 140 can be a pair of wireless earbuds. In other embodiments, any personal electronic device having a battery to be charged can be substituted. Figure 1 The load / battery is omitted in the figure. However, Figure 1 The power flow paths are shown, including low dropout regulator (LDO) / switches 142 and 144, chargers 152 and 154, and various feedback voltages provided to controller 112. More specifically, for each load in charged system 140, controller 112 can be provided with the voltage at contacts 132 and 134, which is also the input voltage to LDO / switches 142 and 144. Additionally, controller 112 can be provided with the output voltage of LDO / switches 142 and 144, which is also the input voltage to chargers 152 and 154. Finally, controller 112 can be provided with the output voltage of chargers 152 and 154. These latter voltages can be provided to the batteries of charged system 140. Charged system 140 can also include its own controller (not shown) that can monitor one or more of the aforementioned voltages and / or transmit them back to controller 112 via feedback paths 111 and 113.

[0025] Further reference is made to Figure 1LDO / switches 142 and 140 can receive a voltage from contacts 132 and 134, respectively. This voltage will generally correspond to the output voltage of power converter 114, minus any voltage drop along the path. LDO / switches 142 and 144 can step this voltage down to the appropriate level for input into chargers 152 and 154, as discussed above. LDO / switches 142 and 144 can be controlled by a controller (not shown) of charging system 140, and can also be used to disconnect the battery / load as needed. Chargers 152 and 154 can receive the output voltage of LDO / switches 142 and 144 and generate the appropriate battery target voltage, as described in greater detail below. In some embodiments, chargers 152 and 154 can be linear chargers. The foregoing description has been based on the illustrated example of a charged system 140 that is a pair of wireless earphones, with charging system 110 being a charging case for such earphones. However, it should be understood that any of a variety of charging systems and charged systems can still be used with the technology described herein.

[0026] Figure 2 Relevant voltage and current waveforms associated with an example battery charging operation are shown. For example, the waveforms can be those corresponding to charging a battery of one of a set of wireless earphones. In other embodiments, any load can be used. The current into the battery is shown by curve 210, which includes a constant current portion 210a (corresponding to a constant current battery charging operation) and a decaying current portion 210b (corresponding to a constant voltage battery charging operation). In many embodiments, particularly those involving lithium ion batteries, the battery can be charged by one or more constant current charging operations, each followed by a constant voltage charging operation. Although curve 210 shows only one constant current interval (followed by one constant voltage interval), it should be understood that multiple such intervals can also be employed with the teachings herein. Figure 2 Although curve 210 shows only one constant current interval (followed by one constant voltage interval), it should be understood that multiple such intervals can also be employed with the teachings herein.

[0027] Curve 212 depicts the corresponding battery voltage during the same charging operation. During the initial constant current charge phase 221a, the battery voltage increases as the charge state of the battery increases (to maintain the constant charge current). The battery voltage 212 can be provided by the charger 152 or 154, and can be adjusted to maintain the desired constant charge current 210a. Once the battery reaches the predetermined charge level, the battery charge voltage can become a constant voltage 212b that will produce the reduced battery charge current 210b discussed above. Curve 214 can depict the charger input voltage that can be provided to the charger (such as the output of the LDO / switch 142 or 144). In prior devices, a constant voltage 214a can be provided to the input of the charger. In contrast, in conjunction with the teachings herein, a variable voltage 214b / 214c can be provided that maintains a relatively small margin above the battery target voltage discussed above. Thus, the losses corresponding to the shaded area 214d can be eliminated. These losses not only waste energy that could otherwise be used for the functionality of the corresponding device, but can also cause undesirable heating that can damage / shorten the life of various battery cells. At high levels, battery charge voltage margin management can include having the charger input voltage within a predetermined margin relative to the battery target voltage (as shown by curve 214b), and then maintaining the battery charger input voltage offset from the battery charge voltage by a predetermined margin amount (as shown by curve 214c). Below is a description of one method of doing so in the context of the depicted system above with respect to Figure 1 The following is a description of one method of doing so in the context of the depicted system.

[0028] Figure 3 A flowchart of control techniques 300 that can be performed by one or more controllers (such as controller 112) to implement a battery charge voltage margin management system is shown. Although described in the context of the system described above with respect to Figure 1 The control techniques 300 can also be used with devices and systems other than wireless earphones, however. Starting at block 302, the controller in the charged system 140 (or other suitable controller for a given system) can collect data from analog-to-digital converters regarding the status of various components of the system (including the status of any batteries in the charged system 140) and various system voltages. The battery status information can include information for the battery of the charged system 140, such as battery voltage, temperature, state of charge, etc. In the illustrated example, these are the batteries of the respective earphones, but in other systems, the status of any applicable batteries can be recorded. In addition to the battery status information, control block 302 can also include the relevant system voltages (such as the battery target voltage discussed above with respect to Figure 1The discussion of the feedback voltage) is collected. More specifically, the collected information can include the voltage at contacts 132 and 134 (which is also the input voltage to LDOs / switches 142 and 144), the output voltage of LDOs / switches 142 and 144 (which is also the input voltage to chargers 152 and 154), and the output voltage of chargers 152 and 154 (which is provided to the battery). Such and other appropriate data can be collected at any suitable interval. In at least some embodiments, it can be desirable to average a certain number of recently collected values to provide a suitable filtering level.

[0029] As this data is collected, the controller in the charged system 140 (or other suitable controller) can determine (in block 304) whether a status request has been received from another controller in the overall system, such as controller 112 in the charging system. In some embodiments, the entirety of control technique 300 can be implemented in a single controller, in which case the inter-controller communication steps of control technique 300 can be eliminated. Otherwise, in the multi-controller embodiment shown, the charged system controller (not shown) can wait until it receives a status request from another controller. Once received, control can proceed to block 306, in which the controller (not shown) of the charged system 140 can calculate an error signal (discussed in greater detail below) and send the error signal to another controller (such as controller 112) along with other relevant information, such as the battery state.

[0030] In the embodiment shown, the remaining blocks 308-316 of control technique 300 can be performed by controller 112 in the charging system 110. However, to reiterate, the particular partitioning of monitoring, control, and calculation shown herein should not be interpreted as limiting, as the charge margin management techniques described herein can be implemented in any of a variety of suitable controller architectures. Nonetheless, in the embodiment shown, the battery data, including the error signal, can be sent to controller 112, which can determine (in block 308) whether the received data is valid. Any of a variety of tests can be performed for this validity check. Assuming the battery data is valid, the received data can be saved (block 310). Then, in block 312, it can be determined whether the session state is valid (described in greater detail below). If so, control can proceed to block 314, in which the appropriate battery voltage margin compensation is determined (described in greater detail below). Once the compensation is determined, power converter 114 can be set to the correct mode (according to the compensation required).

[0031] Figure 4An expanded flowchart showing operations associated with blocks 312-316 discussed above in more detail is shown. From block 402, controller 112 (or other suitable controller) can wait to determine whether valid data is received from the charged system 140. In the illustrated implementation relating to a pair of wireless earphones, block 402 can be determined in the affirmative if either of the earphones returns valid data. This concept can be extended such that in any multi-device charged system, control can proceed whenever any battery returns valid data. However, in some multi-device charged system implementations, it can be desirable to wait to determine whether all batteries return valid data before proceeding. For a single device system, control can proceed when the single battery returns valid data.

[0032] Once valid data is returned, in block 404, it is determined whether any connected device (e.g., either of the wireless earphones) is charging. If not, control can return to block 402 because there is no need to implement the charging voltage margin management technique if the battery is not charging. Otherwise, if at least one battery of the charged system 140 is charging, it can be determined in block 406 whether it is time for the closed loop margin management algorithm to run. In at least some implementations, it can be desirable to prevent the algorithm from running continuously because it will take some time for the batteries and other system components to respond to compensation changes made by the algorithm. Thus, a suitable update interval can be implemented to prevent continuous chasing of appropriate compensation values.

[0033] If it is time for the closed loop margin management algorithm to run, it can be determined in block 408 whether the output of the power converter 114 appears to be out of bounds, meaning that the output of the converter is outside of a certain predetermined range. For example, in one implementation, a range of 3.8V to 5V can be deemed appropriate. If the voltage is not out of bounds, control can proceed to block 412a / 412b discussed below. If it is determined that the voltage is out of bounds, a power converter read error flag can be set in block 410 (again, refer to block 422 below), at which point control can proceed to block 412a / 412b.

[0034] Blocks 412a-420a and 412b-420b correspond to the respective left and right wireless earpieces of the illustrated embodiment and describe the required compensation levels of the closed loop margin management technique. These blocks are identical for each earpiece, and the corresponding load will take similar steps. Thus, these steps are described together. Starting in block 412a / 412b, it can be determined if the data from each battery / load of the charging system 140 is valid data. If not, i.e., if the data is invalid, control can bypass blocks 414a / 414b-420a / 420b and proceed to block 422, discussed in greater detail below. If so, it can be determined in block 414a / 414b if the battery is charging. If not, i.e., if no earpiece is charging, control can bypass blocks 416a / 416b-420a / 420b and proceed to block 422, discussed in greater detail below. Otherwise, if it is determined in block 414a / 414b that the corresponding battery is charging, control can proceed to block 416a / 416b, where it can be determined if the session is active.

[0035] The use of a session for closed loop margin management is described in greater detail below. If it is determined in block 416a / 416b that the session is not active, control can bypass blocks 418a / 418b-420a / 420b and proceed to block 422, discussed in greater detail below. Otherwise, if it is determined in block 416a / 416b that the session is active, control can proceed to block 418a / 418b, where the error reported by the charging system (discussed above) can be used to determine the appropriate compensation level, as described in greater detail below. Control can then proceed to block 420a / 420b, where the target voltage of the converter 114 can be determined (using the determined compensation).

[0036] Control then proceeds to block 422. In block 422, it is determined if the charging system session has expired, or if there has been a converter read error (block 410, discussed above). If either of these conditions is true, the closed loop margin algorithm should properly terminate. Thus, the output voltage of the converter 114 can be set to its reset value, i.e., a certain nominal value that provides proper battery charging in all cases. Additionally, but optionally, a delay period (block 424) can be set before the algorithm is run again. Otherwise, if the session has not expired and there has not been a converter out-of-limits error, control can proceed to block 426.

[0037] In block 426, it can be determined whether any of the battery / load of the charged system 140 is in an active session. (Again, sessions for the control algorithm are discussed in more detail below.) If no charged system battery is in an active session, control can return to block 402, the start of the algorithm. Otherwise, if a battery / load of the charged system 140 is in an active session, control can go to block 428, where it is determined whether the required compensation for either path (i.e., either earpiece) is non-zero. If not, meaning that the compensation determined in blocks 418a and 418b is equal to zero, control can return to block 402 (the start of the algorithm) via block 430, where a delay (e.g., 1 second) before running the algorithm again can be set. Otherwise, if at least one path determines a non-zero compensation value, control can go to block 432, where the highest target voltage (corresponding to the maximum compensation) can be selected, and the output of the converter 114 can be set to that maximum target voltage in block 434. Additionally, control can return to the start of the algorithm (block 402) with a suitable delay (e.g., 3 seconds) before returning to the algorithm.

[0038] Figure 5 and Figure 6 depicts determination of a suitable compensation level. Figure 6 depicts a series of increasing / decreasing power converter output voltage levels as a function of the error signal, discussed in more detail below. Figure 5 is a flowchart depicting a technique 500 for selecting among various compensation levels, which can be considered an extension of blocks 418a / 418b and 420a / 420b.

[0039] Referring to Figure 5 , the technique starts in block 502, where it is determined whether the absolute value of the error signal seen by the charged system is greater than a threshold (e.g., 350 mV). Different thresholds can be selected depending on the particular application. The error signal can be determined as the input voltage provided to the power converter 114, less the rail voltage of the charging system 110, less the sum of (a) the margin associated with the LDO / switch 142, (b) the margin associated with the charger 152, and above the required margin or margin level of the battery charge target voltage (e.g., Figure 2 depicted in block 504). In other words, the error signal is intended to compensate for the voltage drop along the power path from the power supply 116 through the converter 114 and the battery of the charged system 140, plus the added margin. In some embodiments, the margin / margin can be about 25-35 mV. Depending on the exact configuration of the system, different error calculations can be used, with the overall idea being to shift the output voltage of the converter 114 (or corresponding converter) to compensate for the voltage drop along the path to the charged battery, plus the predetermined margin margin.

[0040] If it is determined in block 502 that the absolute value of the error signal is greater than a certain first threshold (e.g., 350 mV), then control can pass to block 510, where it is determined whether the error is positive or negative. If the error is negative, then the compensation can be set to a predetermined maximum negative value (e.g., -300 mV). Alternatively, if the error is positive, then the compensation can be set to a predetermined maximum positive value (e.g., 300 mV). These can correspond to regions 608 and 610 in FIG. 6. In other words, if the error signal has a large positive value, then the supplied voltage is significantly greater than the voltage needed to maintain a suitable high-efficiency margin above the target voltage. Thus, the output voltage of the converter 114 can be decreased by a relatively large increment. On the other hand, if the error signal has a large negative value, then the supplied voltage can be significantly less than the voltage needed to maintain a suitable margin above the target voltage, causing the charge to slow down, and the output voltage of the converter 114 can be increased by a relatively large increment to increase the margin. Figure 6

[0041] Alternatively, if it is determined in block 502 that the absolute value of the error signal is less than the first threshold (e.g., 350 mV), then control can pass to block 504, where it is determined whether the error is greater than a second, intermediate threshold (e.g., 150 mV). If so, then the compensation can be set to an intermediate value (block 516). In other words, if the error signal is relatively large (i.e., greater than the second threshold but less than the first threshold), then the supplied voltage can be slightly greater than the voltage needed to maintain a suitable high-efficiency margin above the target voltage, and the output voltage of the converter 114 can be decreased by an intermediate increment to reduce the margin. This corresponds to region 606 in FIG. 6. Figure 6

[0042] Alternatively, if it is determined in block 504 that the value of the error signal is less than the second threshold, then control can pass to block 506, where it can be determined whether the error is greater than a third, minimum threshold or less than zero. If not, which means that the error is a small positive value, then control can pass to block 508, where the compensation is set to zero. This corresponds to the deadband region 602 in FIG. 6. In other words, if the error signal is relatively small, then the output voltage of the converter 114 is close to a value that provides sufficient margin but maximum efficiency in the battery charge. Moreover, in this region, there can be other limitations on the control circuit (such as analog-to-digital converter (ADC) accuracy, etc.). Alternatively, if it is determined in block 506 that the error signal is greater than the third minimum threshold or negative, then control can pass to block 518, where the compensation value can be set to the value of the error signal - 25 mV or any other margin value chosen depending on the details of the given system. Figure 6

[0043] Figure 5 Figure 6 ​​​​The foregoing description is based on a series of three thresholds and corresponding small, medium, and large compensation value ranges. It should be appreciated that more or fewer thresholds and compensation values can be used as appropriate in any particular application. Generally, the compensation point determination is a determination of how far the system is from a suitable high-efficiency minimum margin, where the suitable efficiency can be determined based on the goals and specific parameters of a particular design. If the margin provided to the charger is greater than the margin required, the charger should be manipulated toward the suitable high-efficiency value to maximize efficiency. If the delta from the optimal value is large, the system can be manipulated by a relatively large compensation step. If the delta from the optimal value is relatively small, the system can be manipulated by a relatively small compensation step. On the other hand, if the margin is insufficient, the system should be manipulated to provide at least a minimum amount of margin to maximize the rate at which the battery can be charged without incurring an excessive efficiency penalty and the risk of resulting thermal damage to the system.

[0044] Figure 7 A flowchart 700 is shown for techniques for controlling the output voltage of the converter 114 (or corresponding converter in a similar system). At block 702, it can be determined whether the input power source 116 of the converter 114 is disconnected from any external source (e.g., connected only to the internal battery of the charging system 110). If so, control can proceed to block 710, discussed in more detail below. Alternatively, if it is determined in block 702 that the input power source 116 of the converter 114 is not disconnected from any external source, it can be determined in block 704 whether it is connected to a wired external power source. If so, control can proceed to block 710, discussed in more detail below. Alternatively, if it is determined in block 704 that the power source 116 is not connected to a wired power source, it can be determined in block 706 whether it is connected to a wireless power source. If so, control can proceed to block 710, discussed in more detail below. Otherwise, control can proceed to block 708 (indicating an unknown connection of the input power source 116), which can trigger a setting of the power converter 114 to its default output voltage (block 716). This can correspond to an error condition in which some problem with the system has resulted in a situation in which the output voltage of the converter is not at an appropriate value for charging, and all can be reset to a normal state to resume normal operation.

[0045] Alternatively, if in any of the preceding blocks 702, 704, or 706, it is determined which power converter 114 to couple to, then in block 710 it can be determined whether the power converter 114 can be set to pass-through mode. In pass-through mode, the input voltage (from the connected source, whether a battery, wired, or wireless) can be passed directly through the converter 114, which can operate without switching. This is only feasible if the voltage input into the converter 114 is approximately equal to the charging voltage required by the battery. If so, passing the voltage through the converter 114 without switching (block 714) can allow for more efficient operation than if the converter 114 actually converted the output voltage. Alternatively, if setting the converter 114 to pass-through mode is not feasible, then the output voltage of the converter 114 can be set to the target voltage determined according to the above-described procedure.

[0046] As discussed above with respect to blocks 312 Figure 3 ), 416a, 416b, and 426, session states can be used to track the charging state of the battery in the charged system 140. These session states can be implemented, for example, as various states of a state machine implemented in the controller 112 (or other suitable location). Depending on the details of the particular implementation, various states can be provided with different meanings. In one embodiment, in relation to the wireless earbud example described herein, there can be a total of four states. The four states can be an inactive state (state 0), an in-progress state (state 1), an active state (state 2), and an expired state (state 3). As one non-limiting example, in relation to a wireless earbud implementation, the inactive state can be set when the wireless earbud is not in the charging case, meaning that the battery of the charged system 140 is not available for charging. Similarly, the in-progress state can be set when the last battery data received is older than a threshold, but the timeout condition for re-running the algorithm has not been met. In the in-progress state, the previously determined compensation value and corresponding converter output voltage can be applied to the battery of the charged system 140. The active state can be set when the battery data is relatively recent, but has not yet acted to determine a compensation level and corresponding converter output voltage (in other words, when the algorithm is determining the appropriate compensation level and corresponding converter output voltage). Finally, the expired state can be set when the data from the charged system is stale and the timeout condition has been met, meaning that it is time to re-run the algorithm to determine a compensation level and corresponding converter output voltage level.

[0047] The foregoing states are merely one example of states that can be used to determine whether a controller of a charging system (e.g., controller 112) has valid data from a charged system 140 that can be used to determine an appropriate compensation level and corresponding converter output voltage to maintain closed loop margin control of one or more chargers 152 / 154 of the charged system 140. In general, any tracking technique for ensuring that valid data is being received and valid output is being generated can be used, with the overall goal of (1) charging the battery of the charged system, (2) in such a way that maximizes efficiency and minimizes the risk of thermal damage, while (3) charging as quickly as possible.

[0048] Various features and embodiments relating to closed loop margin management for battery charging systems are described above. Such systems can be used in a variety of applications, but can be particularly advantageous in conjunction with personal electronic devices for which it is desirable to maximize the efficiency of battery charging operations while simultaneously minimizing the risk of thermal damage to the battery. Additionally, while a number of specific features and various embodiments have been described, it should be understood that various features and embodiments can be combined in particular implementations in various permutations, unless otherwise indicated as being mutually exclusive. Accordingly, the various embodiments described above are merely provided as examples and should not be construed as limiting the scope of the disclosure. Various modifications and alterations to the principles and embodiments described herein can be made within the scope of the disclosure and without departing from the scope of the claims.

Claims

1. An electronic system comprising: at least one wireless earpiece, the at least one wireless earpiece comprising at least one charger and at least one battery configured to be charged by the at least one charger, wherein the at least one charger receives power from a charging case; a charging case, the charging case comprising a power converter configured to supply power to the at least one charger of the wireless earpiece and a controller configured to control the power converter; the controller configured to: receive feedback information from the wireless earpiece, the feedback information comprising one or more voltages of the wireless earpiece; determine an output voltage compensation value for the power converter as a function of the feedback information; and set an output voltage of the power converter as a function of the compensation value, wherein the compensation value and the output voltage are selected to maintain a preselected margin between a battery charge target voltage of the charger and a voltage supplied to the charger.

2. The electronic system of claim 1, wherein the at least one wireless earpiece comprises two wireless earpieces.

3. The electronic system of claim 1, wherein the one or more voltages of the wireless earpiece comprise at least an input voltage of the at least one charger and an output voltage of the at least one charger.

4. The electronic system of claim 1, wherein the wireless earpiece further comprises at least one low dropout regulator or at least one switch coupled between an input of the at least one charger and at least one power contact of the at least one wireless earpiece.

5. The electronic system of claim 1, wherein the charging case further comprises one or more switches coupled between an output of the power converter and one or more power contacts of the charging case.

6. The electronic system of claim 1, wherein the charging case further comprises a power source configured to provide power to the power converter.

7. The electronic system of claim 6, wherein the power source is coupled to a battery within the charging case.

8. The electronic system of claim 6, wherein the power source is configured to be coupled to an external power source through a wired connection.

9. The electronic system of claim 6, wherein the power source is configured to be coupled to an external power source through a wireless connection.

10. A method of supplying power to a battery charger of at least one wireless earpiece, the battery charger for charging a battery of the wireless earpiece, the method comprising: receiving feedback information from the wireless earpiece at a controller of a charging case, the feedback information comprising one or more voltages of the wireless earpiece; determining, by the controller of the charging case, an output voltage compensation value for a power converter of the charging case as a function of the feedback information, the power converter configured to deliver power to the battery charger of the at least one wireless earpiece; and setting, by the controller, an output voltage of the power converter as a function of the compensation value, wherein the compensation value and the output voltage are selected to maintain a preselected margin between a battery charge target voltage of the charger and a voltage supplied to the charger.

11. The method of claim 10, wherein the at least one wireless earpiece comprises two wireless earpieces.

12. The method of claim 10, wherein the one or more voltages of the wireless earpiece comprise at least an input voltage of the battery charger and an output voltage of the battery charger.

13. The method of claim 10, wherein determining, by the controller of the charging case, an output voltage compensation value for a power converter of the charging case based on the feedback information comprises determining whether data received from the wireless earpiece is valid.

14. The method of claim 13, wherein determining, by the controller of the charging case, an output voltage compensation value for a power converter of the charging case based on the feedback information comprises determining whether data received from the wireless earpiece is valid, and further comprising setting a wireless earpiece status to one of a plurality of statuses in response to the feedback information.

15. The method of claim 10, wherein the compensation value is selected from a plurality of predetermined compensation levels.

16. The method of claim 15, wherein the predetermined compensation levels comprise a plurality of positive values, at least one negative value, and a zero value.

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