Patent Description:
Some electronic devices may have charging circuitry that enables batteries to be charged without the need to shut down the device. However, the electronic device ceases to be portable when connected to a power source to charge its batteries using the charging circuitry. In either case, the use of a portable electronic device is interrupted whenever its batteries run low. Interruption for charging at a power source can be particularly disruptive in the case of smart glasses with prescription lenses since the wearer may be reliant on the lenses.

<CIT> relates to a battery pack including a battery unit, a connection terminal configured to electrically connect the battery pack to an external device, a loop control unit connected between the battery unit and the connection terminal, and a microcontroller, connected to the loop control unit and suitable to control the loop control unit. The microcontroller is adapted to control the loop control unit according to a voltage of the external device and a voltage of the battery unit, so as to adjust a direction and/or a magnitude of a current passed through the battery unit. The control of the current by the above microcontroller is automated and based on the comparison of the internal and external voltages.

<CIT> describes a proposal for limiting excessive current during connection of a battery in parallel with other batteries.

Typically, batteries powering an electronic device should be maintained at roughly equal levels of charge. An uneven charge between batteries may result in an inrush of current when a relatively fresh battery is connected in parallel to a relatively depleted battery. Such an inrush of current may damage the circuitry of the electronic device. Moreover, powering an electronic device using batteries having different charge levels may be inefficient. For instance, the battery having a higher charge level may be depleted more quickly than the battery having a lower charge level. Additionally, the battery having a lower charge level may have a higher resistance than the battery with the higher charge level, which may cause the battery with the lower charge level to overheat or otherwise become damaged. Further, inrush current may trigger overcurrent protection in the hardware, which may interrupt the intended operation of the device. To avoid these issues, typically all batteries are replaced at the same time to assure similar charge levels between all of the batteries. In situations where rechargeable batteries are used, a user may have to wait until a full set of batteries are completely charged to be certain that each battery in the set carries an equal charge. The requirement for equally charged batteries can thus extend interruptions to the use of portable electronic devices.

Aspects of this disclosure are directed to power management systems for electronic devices. The power management system may allow for a battery of an electronic device to be replaced while the electronic device remains powered by another battery. The power management system may also be configured to manage batteries having different levels of charge.

In one aspect, a power delivery system comprises the features of claim <NUM>.

In some arrangements according to any of the foregoing, the battery connection may be a first battery connection, the soft-start circuit is a first soft-start circuit, and the battery is a first battery, and the system may further comprise a second battery connection, and a second soft-start circuit connected to the battery connection and the main power bus. The second soft-start circuit may be configured to provide increasing levels of power to the main power bus from the second battery connection when a second battery having a voltage level higher than a voltage level on the main power bus is connected to the second battery connection, and stop power delivery from the second battery to the main power bus when the voltage level of the second battery is less than the voltage level on the main power bus.

In some arrangements according to any of the foregoing, the output transistor may be a field effect transistor, and a voltage at a gate of the output transistor is a function of a voltage at the battery connection and a voltage at the power bus.

In some arrangements according to any of the foregoing, the gate of the output transistor and the first input of the operational amplifier may be wired in parallel to the respective battery connection.

In some arrangements according to any of the foregoing, the output transistor may be an n-channel transistor and the governance transistor is a p-channel transistor.

In some arrangements according to any of the foregoing, an electronic system may comprise any of the foregoing power management systems and a charging pod for charging batteries connectable to the battery connections.

In some arrangements according to any of the foregoing, a wearable smart glasses device may comprise any of the foregoing power management systems.

In some arrangements according to any of the foregoing, the smart glasses may include two temple tips, each of the two temple tips including one or more batteries.

In some arrangements according to any of the foregoing, the temple tips may each be independently removable from the electronic device.

In some arrangements according to any of the foregoing, an electronic system may comprise any of the foregoing smart glasses devices and a charging pod including a wireless charging coil configured to receive one or more of the two temple tips and charge the one or more batteries.

In some arrangements according to any of the forgoing the power delivery system may comprise a first electrical connection, a second electrical connection, wherein each of the first electrical connection and the second electrical connection includes a battery connection, and an integrated circuit having stored thereon software instructions that, when executed, will cause the integrated circuit to restrict current draw from a battery connected to the first electrical connection or second electrical connection if the voltage of the battery exceeds a threshold voltage while allowing an electronic device comprising the power delivery system to be maintained powered by one or more batteries connected to the other electrical connection.

In some arrangements according to any of the foregoing, the device may further comprise two soft start switches controlled by the integrated circuit, each soft start switch associated with a respective one of the battery connections so as to be able to limit current draw from the respective one of the battery connections.

In some arrangements according to any of the foregoing, the device may further comprise a gas gauge associated with each of the battery connections and the governance of the current drawn from the battery connections may include monitoring the gas gauges.

In some arrangements according to any of the foregoing, the power delivery system may further comprise a gas gauge associated with each of the battery connections and the integrated circuit may be configured to monitor the gas gauges for a governance of a current draw from batteries connected to the first and second electrical connections.

In some arrangements according to any of the foregoing, the integrated circuit may be configured to send an error message to an output device if a battery having a voltage below a predefined threshold is connected within either of the battery connections.

In some arrangements according to any of the foregoing, the instructions, when executed, may further cause the integrated circuit to decrease the restriction of current draw as time elapses after connection of a battery carrying a voltage exceeding the threshold.

In some arrangements according to any of the foregoing, the instructions, when executed, may further cause the integrated circuit to decrease the restriction of current draw gradually.

In some arrangements according to any of the foregoing, the threshold may be a predefined threshold.

In some arrangements according to any of the foregoing, the battery may be a first battery and the threshold is a voltage of a second battery connected to the second battery connection.

In some arrangements according to any of the foregoing, the restriction of current draw may be directly related to a difference between the voltage of the first battery and the threshold.

In another aspect, a power delivery system according to any one of the foregoing arrangements may comprise at least one additional battery connection and at least one additional soft-start circuit connected to the at least one additional battery connection and the main power bus. The at least one additional soft-start circuit may be configured to provide increasing levels of power to the main power bus when a battery having a voltage level higher than a voltage level on the main power bus is connected to the at least one additional battery connection. The at least one additional soft-start circuit may also be configured to prevent power delivery to the main power bus from the battery connected to the at least one additional battery connection when the voltage level of this battery is less than the voltage level on the main power bus.

In some arrangements according to any of the foregoing, the restriction of current draw may be based on a difference between the voltage of a first battery connected to the first electrical connection and a threshold voltage for a second battery connected to the second battery connection.

In another aspect, an electronic device may comprise a power delivery system according to any of the foregoing arrangements.

In some arrangements according to any of the foregoing, the electronic device may be a wearable smart glasses device.

In some arrangements according to any of the foregoing, the electronic device may comprise two temples for wearing the electronic device on a head of a user, and each temple may comprise a temple tip including one or more batteries.

In another aspect, an electronic system may comprise an electronic device according to any of the foregoing arrangements, and a charging pod for charging one or more batteries that are connectable to a battery connection of the electronic device.

In some arrangements according to any of the foregoing, the charging pod may include a wireless charging coil.

In some arrangements according to any of the foregoing, the charging pod may be configured to charge one or more batteries of a temple tip of the electronic device.

The present disclosure is directed to a power delivery system that allows for safe replacement of a battery of an electronic device to be replaced Each battery may simultaneously provide power to the electronic device through the power delivery system. When a battery is depleted or otherwise has a low charge level, the battery may be removed from the electronic device and replaced with a battery having more charge, such as a freshly charged battery. As the power delivery system provides power to the electronic device from multiple batteries connected in parallel when one of the batteries is removed the power delivery system may continue to provide power from the remaining batteries to the electronic device.

The present disclosure avoids the need for equally charged batteries for safe operation of a battery powered device. According to some aspects, this may be accomplished by configuring the device to soft-start a battery upon connection to the device, when the battery being connected has relatively more charge than the one or more other batteries powering the device. The device may also be configured to stop drawing from a battery that has a relatively low charge relative to the one or more other batteries, so as to draw only from the batteries having greater charge until the batteries are at a relatively equal charge. The above described functionality may enable a battery to be replaced while the electronic device remains powered by another battery. In this regard, the power delivery system of the electronic device may include two or more batteries connected in parallel.

A power management subsystem may be configured to balance the current drawn from the batteries when powering an electronic device. The power management subsystem may inhibit the current draw from a battery having a relatively greater charge. The inhibition may be a function of a difference in charge between two batteries. The power management subsystem may be, for example, a programmable integrated circuit (PIC). In one exemplary embodiment, instructions stored on the PCI may, when executed, cause the integrated circuit to restrict current draw from a battery connected to the first electrical connection or second electrical connection if the voltage of the battery exceeds a threshold voltage. This may for example include instructions to monitor gas gauges of the batteries and adjust current drawn therefrom. Alternatively, the power management subsystem may be a hardware circuit at each battery connection that is constructed to open or close a field effect transistor to varying degrees depending on the proportion of the voltage across the battery to the voltage at a power bus for the other systems of the device.

As used herein the term "electronic device" may include any device capable of being at least partially powered by one or more batteries. For example, an electronic device may be a tablet computer, laptop computer, mobile phone, earphones, wearable devices, such as smart watches, fitness trackers, health monitors, smart fashion, etc. As further described herein, the electronic device may be a pair of smart glasses. The smart glasses may include a battery slot at each temple tip. The battery slots may be connected in parallel to the electronics of the device such that the device may continue to operate when one battery is removed. The device may be provided with a battery charging pod and at least one spare battery so that the device may operate indefinitely. The charging pod may be capable of charging the batteries wirelessly, such as by the inclusion of at least one charging coil for inductive charging.

<FIG> illustrates an electronic device <NUM> connected to a power delivery system <NUM>. The electronic device is connected to a first soft-start circuit <NUM> and second soft-start circuit <NUM> via a power bus <NUM>. As described herein, each soft-start circuit may include a power source, such as one or more batteries that deliver power to the electronic device through the power bus <NUM>. Although not shown, electronic device <NUM> may include any number of components, circuits, or subsystems, any of which may be independent of one another or grouped within systems or subsystems themselves.

As further shown in <FIG>, the power bus <NUM> may receive power through a power management subsystem <NUM> of power delivery system <NUM>, provided collectively by the first soft-start circuit <NUM> and a second soft-start circuit <NUM>. Although <FIG> illustrates only two soft-start circuits, any number of soft-start circuits may be included in the power delivery system <NUM>. The power management subsystem <NUM> is illustrated as including two soft-start circuits <NUM>, <NUM> by way of example only. In this regard, the power management subsystem may include any number of soft-start circuits. Each soft-start circuit may be similar to first soft-start circuit <NUM>, described in detail below, and may each be connected to a common power bus.

<FIG> illustrates first soft-start circuit <NUM>. Second soft-start circuit <NUM> is generally alike to first soft-start circuit <NUM>. That is, the illustration and the following description of the first soft-start circuit <NUM> may apply to the second soft-start circuit <NUM>. In some instances, power delivery system <NUM> may be designed such that second soft-start circuit <NUM> differs from first soft-start circuit <NUM> in some ways, such as with more or fewer components. Likewise, where a device includes more than two soft-start circuits, each additional soft-start circuit may be compared with first soft-start circuit <NUM>, without necessarily being identical to soft-start circuit <NUM>.

As shown in <FIG>, first soft-start circuit <NUM> includes a battery connection <NUM> at which a (first) battery <NUM> may be connected. Battery <NUM>, though illustrated in <FIG> as being integrated into the soft-start circuit <NUM>, may be removable from the first soft-start circuit <NUM>. Moreover, although only a single battery <NUM> is shown, any number of batteries, such as a battery pack containing multiple batteries, may be connected to the battery connection <NUM>.

First soft-start circuit <NUM> is configured to compare the voltage of the battery <NUM> to the voltage on power bus <NUM>. In this regard, the first soft-start circuit <NUM> measures the voltage on power bus <NUM> to the voltage of the battery <NUM>. The first soft-start circuit <NUM> may measure the voltage on the bus measuring line <NUM> to determine the voltage of the power bus <NUM>. The first soft-start circuit may control the power output by the battery <NUM> onto power out line <NUM> dependent on the outcome of the comparison.

In the example illustrated in <FIG>, first soft-start circuit <NUM> will effectively disconnect battery <NUM> from power bus <NUM> when the voltage on power bus <NUM> exceeds the voltage of battery <NUM>. By disconnecting batteries holding relatively low charge, soft-start circuits <NUM>, <NUM> will protect those batteries and the efficiency of the system, as current will be prevented from flowing from power bus <NUM> to a battery of lower voltage. In some arrangements, the soft-start circuits <NUM>, <NUM> may be implemented with a tolerance allowing a battery to remain connected until a difference or ratio between the power bus <NUM> voltage and the battery voltage reaches a minimum threshold. Such tolerance may be provided by, for example, modifying comparison lines <NUM>, <NUM>, described below, or by adding a Schmitt Trigger circuit to the soft-start circuits <NUM>, <NUM>.

The first soft-start circuit <NUM> will restrict power from battery <NUM> to power bus <NUM> when the voltage of battery <NUM> exceeds the voltage on power bus <NUM>. When the voltage of battery <NUM> exceeds the voltage on power bus <NUM>, the degree to which first soft-start circuit <NUM> restricts connection between battery <NUM> and power bus <NUM> will increase as the difference between the voltages increases. That is to say, the amount of power output by the battery <NUM> onto the power bus <NUM> may be prevented or limited when the voltage of the battery <NUM> is larger than the voltage on the power bus <NUM>. Soft-start circuits <NUM>, <NUM> according to the illustrated example will therefore protect depleted batteries and the efficiency of the device by preventing unintended rushes or redirection of current as batteries with a higher charge are connected. By restricting output from batteries carrying a higher voltage than power bus <NUM>, soft-start circuits <NUM>, <NUM> will also protect main system <NUM> from inrush current when a freshly charged battery is connected. Since the restriction of the connection has a direct relationship with the amount that the voltage of a battery exceeds the voltage on power bus <NUM>, the restriction will decrease over time, as further described herein.

The first soft-start circuit <NUM> will provide an unobstructed connection between battery <NUM> and power bus <NUM> when the voltage of battery <NUM> equals the voltage on power bus <NUM>. The soft-start circuits <NUM>, <NUM> may be modified from the numerical ratios stated herein and the arrangement illustrated in <FIG> to allow unobstructed connection between battery <NUM> and power bus <NUM> when the voltage of battery <NUM> differs slightly from voltage on power bus <NUM> as well. The amount of difference tolerable for unobstructed connection depends, at least in part, on the chemistry and type of battery <NUM>. Any plural number of soft-start circuits according to the following description of first soft-start circuit <NUM> may therefore be connected to a common power bus <NUM> to enable batteries at various levels of charge to be safely connected or disconnected from respective soft-start circuits without interrupting operation of main system <NUM>.

To accomplish the above described comparison between the voltage of battery <NUM> and the voltage on the power bus <NUM>, positive comparison line <NUM> and negative comparison line <NUM> are connected to a positive input <NUM> and a negative input <NUM>, respectively, of an operation amplifier (op-amp) <NUM> of the first soft-start circuit <NUM>. The positive power supply terminal <NUM> of op-amp <NUM> is connected to power bus <NUM>, while the negative power supply terminal <NUM> of op-amp <NUM> goes to ground <NUM>. As such, op-amp <NUM> is powered by power bus <NUM>. Although a number of grounds are shown in <FIG>, for clarity only ground <NUM> is labeled.

Positive comparison line <NUM> is connected to a voltage divider formed between battery out line <NUM> and battery ground line <NUM>. As shown in <FIG>, battery out line <NUM> is connected to battery connection <NUM> and battery ground line <NUM> is connected to ground. The voltage divider is formed by resistor <NUM> and resistor <NUM>. The resistors may be sized such that the voltage between resistor <NUM> and resistor <NUM> is within the operating parameters of the op-amp <NUM>. For instance, resistor <NUM> may be <NUM> kiloohm (K) and resistor <NUM> may be <NUM>. Resistors <NUM> and resistor <NUM> are arranged in series to act as a voltage divider between battery out line <NUM> and battery ground line <NUM>.

Positive comparison line <NUM> is connected between resistors <NUM>, <NUM>, and thus carries a fraction of the voltage of battery <NUM>. Capacitor <NUM>, for which a suitable capacitance may be <NUM> microfarad (µF), is arranged in parallel with resistor <NUM> to act as a filter. Voltage on positive comparison line <NUM> and into positive input <NUM> will therefore be generally proportional to voltage across battery <NUM>.

Similarly, negative comparison line <NUM> is connected to bus measuring line <NUM> to carry a fraction of the voltage on the bus measuring line <NUM>. Resistor <NUM> and resistor <NUM>, for which suitable resistances are <NUM> and <NUM>, respectively, are arranged in series between bus measuring line <NUM> and ground to act as a voltage divider. Negative comparison line <NUM> is connected between resistors <NUM>, <NUM>, and thus carries a fraction of the voltage of power bus <NUM>. Capacitor <NUM>, for which a suitable value is <NUM>µF, is arranged in parallel with resistor <NUM> to act as a filter. The voltage on negative comparison line <NUM> and into negative input <NUM> will therefore be generally proportional to the voltage on power bus <NUM>.

The positive input <NUM> and negative input <NUM> to op-amp <NUM> are therefore proportional to the voltages of battery <NUM> and power bus <NUM>, respectively. As such, the output from op-amp <NUM> will vary as the relationship between the voltages of battery <NUM> and power bus <NUM> varies.

Op-amp <NUM> outputs on op-amp output line <NUM> to a gate of a governance transistor <NUM>, which is a normally off transistor that will turn on as voltage at its gate increases beyond voltage at its source. In the illustrated example, governance transistor <NUM> is an enhancement type N-channel metal oxide semiconductor field effect transistor (MOSFET). The source of governance transistor <NUM> is connected to ground, so the drain-source conductivity of governance transistor <NUM> will largely depend on the output of op-amp <NUM>.

A governing line <NUM> connects the drain of governance transistor <NUM> to the gate of an output transistor <NUM>, which is a normally off transistor that will turn on as the voltage at its gate falls below the voltage at its source. In the illustrated example, output transistor <NUM> is an enhancement type P-channel MOSFET. Battery out line <NUM> is connected to the source of output transistor <NUM> and, through a resistor <NUM>, to governing line <NUM>. Voltage on governing line <NUM> is thus proportional to the voltage of battery <NUM> at a magnitude depending on the degree to which governance transistor is turned on, which in turn depends on the relationship between the voltages of battery <NUM> and power bus <NUM>. Power out line <NUM> connects the drain of output transistor <NUM> to power bus <NUM>. Thus, the connection between battery <NUM> and power bus <NUM> is throttled by output transistor <NUM> by an amount depending on the relationship between the voltages of battery <NUM> and power bus <NUM>. Specifically, output transistor <NUM> will be completely off when the voltage on power bus <NUM> exceeds the voltage of battery <NUM>, output transistor <NUM> will be completely on when the voltage on power bus <NUM> equals the voltage of battery <NUM>, and when the voltage of battery <NUM> exceeds the voltage on power bus <NUM>, output transistor <NUM> will be partially on to a degree that is inversely proportional to the difference between voltages.

As shown, first soft-start circuit <NUM> includes resistors and capacitors. Numerical values for suitable resistances and capacitances of these elements are set forth herein. Such values are suitable at least for a battery <NUM> with capacity for, for example, equal to or about <NUM> volts at maximum charge. Such values are merely examples and may differ in other arrangements according to the present disclosure. For example, the values may be increased or decreased in proportion with one another. For that reason, the disclosed values also indicate suitable ratios between the resistances and capacitances of the elements of first soft-start circuit <NUM>. Individual values may also be varied without entirely altering the function of first soft-start circuit <NUM>. For each resistance or capacitance described herein, values greater or less than the stated value by <NUM>% of the stated value are also within the scope of the disclosure. All ratios between values resulting from such variation of individual values are also contemplated.

Resistor <NUM> and resistor <NUM>, for which suitable resistances are <NUM> and <NUM>, respectively, are arranged in series between battery out line <NUM> and governance transistor <NUM> to act as a voltage divider. Governing line <NUM> is connected between resistors <NUM>, <NUM>, and thus carries a fraction of the voltage of battery out line. Capacitor <NUM>, for which a suitable capacitance is <NUM>µF, is arranged in parallel with resistor <NUM> to act as a filter. Capacitor <NUM>, for which a suitable capacitance is <NUM>µF, is also connected in parallel with resistor <NUM> and across the drain and source of governance transistor <NUM>, to act as another filter.

<FIG> illustrates another electronic device <NUM> connected to a power delivery system <NUM>. As illustrated, the electronic device is connected to the power delivery system via power bus <NUM>. Power is supplied to bus <NUM> by a power management subsystem <NUM> including a programmable integrated circuit (PIC) <NUM>, first soft start switch <NUM>, and second soft start switch <NUM>. The first soft start switch <NUM> is controllable by PIC <NUM> to throttle power drawn from a removable first battery <NUM>, and second soft start switch <NUM> is controllable by PIC <NUM> to throttle power drawn from a removable second battery <NUM>. The power delivery system is illustrated with two soft-start switches <NUM>, <NUM> and two batteries <NUM>, <NUM> by way of example only, and alternative arrangements may have any plural number of soft-start switches and batteries generally like those described here.

First battery <NUM> includes a first cell <NUM> and a first gas gauge <NUM>, and second battery <NUM> includes a second cell <NUM> and a second gas gauge <NUM>. Gas gauges <NUM>, <NUM> measure charge held by their respective cells <NUM>, <NUM>, such as through temperature measurements. PIC <NUM> may monitor gas gauges <NUM>, <NUM>, and thereby the charge held by cells <NUM>, <NUM>.

PIC <NUM> may include a processor and a non-transitory computer readable memory medium carrying instructions that, when executed, cause PIC <NUM> to read gas gauges <NUM>, <NUM> and control soft-start switches <NUM>, <NUM> to prevent unintended current rushes or redirections as batteries <NUM>, <NUM> are connected or disconnected, without interruption to the operation of main system <NUM> as long as at least one battery <NUM>, <NUM> carrying sufficient charge remains connected, in a manner similar to that described above with regard to soft-start circuits <NUM>, <NUM>.

In one example, PIC <NUM> may be programmed to control soft-start switches <NUM>, <NUM> to disconnect a battery <NUM>, <NUM> carrying a cell <NUM>, <NUM> with a lower voltage than a voltage on bus <NUM>, as estimated from measurements through gas gauges <NUM>, <NUM>. PIC <NUM> may be programmed to control soft start switches <NUM>, <NUM> to, upon connection of a battery <NUM>, <NUM> carrying a cell <NUM>, <NUM> with a greater voltage than a voltage on bus <NUM> as estimated from measurements through gas gauges <NUM>, <NUM>, initially restrict a connection between the cell carrying the higher voltage and the bus <NUM>. PIC <NUM> may further be programmed to decrease such restriction over time, thus soft-starting the newly connected battery.

In another example, the memory medium of PIC <NUM> may carry instructions that, when executed, cause PIC <NUM> to execute a power management logic illustrated by the flowchart of <FIG>. The logic <NUM> may be followed independently with regard to each connection point where a battery, such as batteries <NUM>, <NUM>, may be attached. PIC <NUM> may begin at step <NUM> by checking, continuously or at intervals, whether a battery is attached to a given battery connection point. When a battery, such as first battery <NUM>, is detected as connected, PIC <NUM> will read the gas gauge at step <NUM>, such as first gas gauge <NUM>.

After acquiring the measurement from the gas gauge, PIC <NUM> will determine whether the battery cell, such as first battery cell <NUM>, is healthy by comparing the gas gauge measurement to a predetermined threshold at step <NUM>. A measurement exceeding the predetermined threshold will indicate that the cell carries a certain minimum amount of charge to be considered "healthy," while a measurement below the predetermined threshold will reveal the battery cell to be "unhealthy. " In the illustrated example, if the cell is found unhealthy, PIC <NUM> may send a warning message at step <NUM> to a user through an output system or user interface of the electronic device. However, in other arrangements, no warning message is sent.

If the cell is determined to be healthy, PIC <NUM> will prevent an inrush current by activating the respective soft-start switch at step <NUM> to restrict connection between the cell and bus <NUM> by a gradually decreasing amount.

The cell, whether healthy or unhealthy, may then remain connected to bus <NUM> until the battery holding the cell is detached. The PIC <NUM> may monitor for detachment of the cell at step <NUM>. After the battery is detached, PIC <NUM> may return to monitoring the battery connection point at step <NUM> for connection of a battery.

<FIG> illustrates an example of an electronic device <NUM> wherein any of the foregoing power delivery systems may be implemented. In the illustrated example, device <NUM> is a pair of smart glasses. In the illustrated example, the device may include any operating hardware typical of smart glasses, such as user interface systems, a projector, a microphone, a speaker, a camera, a radio, wireless communication systems, or any combination of the foregoing.

Smart glasses <NUM> include a left temple <NUM> and a right temple <NUM>, which end, respectively, in a left temple tip <NUM> and a right temple tip <NUM>. Battery connections or connection points according to the above described power delivery systems <NUM>, <NUM> and power management subsystems <NUM>, <NUM> may be located anywhere in the smart glasses <NUM>, with, in some examples, each of the temple tips <NUM>, <NUM> including one connection or connection point. The soft-start circuits <NUM>, <NUM> or soft-start switches <NUM>, <NUM> may also each be included in a respective one of the temple tips <NUM>, <NUM>, or elsewhere within a respective one of the temples <NUM>, <NUM>, or anywhere else in the smart glasses <NUM>.

Batteries may be removably connected to the connections or connection points within temple tips <NUM>, <NUM>. In addition or in the alternative, temple tips <NUM>, <NUM> may be removably connected to the respective temples <NUM>, <NUM>. Thus, in various examples, when a battery needs to be replaced, a user may replace the battery itself, or may remove the temple tip <NUM>, <NUM> containing the battery and replace it with a charged temple tip.

<FIG> illustrates a charging pod <NUM> that may be used with smart glasses <NUM> or any other implementation of the above described power delivery system <NUM>, <NUM> and power management subsystems <NUM>, <NUM>. Charging pod <NUM> according to the illustrated arrangement includes two charging slots <NUM> for receiving and charging a <NUM> or a battery <NUM>, <NUM> (referred to generically as "batteries" below) according to the foregoing arrangements <NUM>, <NUM>. However, in alternative examples, charging pod <NUM> may have only one charging slot <NUM>, or any other natural number quantity of charging slots <NUM>. Charging pod <NUM> may be configured to receive power from any suitable power source, such as a typical plug for a wall outlet, or any variety of USB or similar electronic connection.

Charging slots <NUM> may be any type of apparatus used for charging batteries. In some examples, charging slots <NUM> are inductive charging coils capable of wirelessly charging the batteries. However, in other examples, charging slots <NUM> may include electrical contacts for conductively charging the batteries. According to the above described alternative arrangements of the temple tips <NUM>, <NUM>, the charging slots <NUM> may be configured to receive and charge the batteries alone, or the charging slots <NUM> may be configured to receive one of the temple tips <NUM>, <NUM>, and to charge the battery contained within or connected to a received temple tip.

Charging pod <NUM> may be part of a system including electronic device <NUM>, or any device including power delivery systems <NUM>, <NUM> according to the present disclosure, and at least one rechargeable battery. The system may include, for example, two, three, four, or more batteries. Since the above described power delivery systems <NUM>, <NUM>, enable uninterrupted operation of electronic device <NUM> as batteries are individually connected or disconnected, as long as one charged battery, or a sufficient minimum number of charged batteries, remains connected to device <NUM>, inclusion of plural batteries in the system enables device <NUM> to operate indefinitely. Where multiple batteries are provided, one battery may power device <NUM> while another is charged in pod <NUM>. A charged battery may be connected to device <NUM> before disconnecting a relatively depleted battery from device <NUM> and charging the depleted battery with pod <NUM>. Thus, shutdown of device <NUM> is not necessary.

Claim 1:
A power delivery system, comprising:
a battery connection (<NUM>); and
a soft-start circuit (<NUM>) connected to the battery connection (<NUM>) and a main power bus (<NUM>), wherein the soft-start circuit (<NUM>) is configured to:
provide increasing levels of power to the main power bus (<NUM>) when a battery (<NUM>) having a voltage level higher than a voltage level on the main power (<NUM>) bus is connected to the battery connection (<NUM>), and
prevent power delivery to the main power bus (<NUM>) from the battery (<NUM>) when the voltage level of the battery (<NUM>) is less than the voltage level on the main power bus (<NUM>),
wherein the soft start circuit includes an output transistor (<NUM>), and the provision of power to the main power bus (<NUM>) is through the output transistor (<NUM>),
characterised in that
the soft start circuit further comprises an operational amplifier (<NUM>) and a governance transistor (<NUM>), and
in that
the battery connection (<NUM>) is wired to a first input (<NUM>) of the operational amplifier (<NUM>), the power bus (<NUM>) is wired to a second input (<NUM>) of the operational amplifier (<NUM>), the output of the operational amplifier (<NUM>) is wired to a gate of the governance transistor (<NUM>), and a drain of the governance transistor (<NUM>) is wired to the gate of the output transistor (<NUM>).