Charging cable with charge status indication

Abstract

The charging cable has a current sensor, a charge status indicator, and a logic circuit to operate the indicator based on the detected current flowing to the chargeable device. If the sensor detects current below a low threshold, the logic circuit operates the indicator to indicate that the cable is not connected to any chargeable device. If the sensor detects current at or above a higher threshold, the logic circuit operates the indicator to provide a perceptible output indicating that the cable is connected to a chargeable device and that current is charging the battery. If the sensor detects current at or above the low threshold but below the high threshold, the logic circuit operates the indicator to provide a perceptible output indicating that the cable is connected to a chargeable device but is not charging the device's battery, for example, when the battery is full or near full.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Application No. 62 / 809,805, filed on February 25, 2019, entitled “Charging Cable with Charging Status Indicator,” the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The disclosed subject matter includes examples of charging cables, rechargeable devices, and systems combining cables and devices, wherein the cables include status indicators and elements configured to detect and provide responsive indications of various cable-to-device coupling or charging states.

[0004] background

[0005] Many types of electronic devices, such as portable or wearable devices, have integrated electronics and require an internal power source in the form of a battery. From time to time, such devices are connected to a power source to recharge the battery. This method of charging electronic devices often uses a charging cable connected to an appropriate receiver on the electronic device. Rechargeable devices can provide users with battery charge status indicators, including the progress of the battery charge. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings depict one or more embodiments by way of example only, and not by way of limitation. In the drawings, like reference numerals indicate like or similar elements.

[0008] Figure 1 is a high-level block diagram of an example combination or system, including a charging cable and a rechargeable device.

[0009] Figure 2 is an isometric view of an example receptacle for a charging cable head and an example cable plug as a receptacle for a chargeable device (or as part of a receptacle), e.g., for rotatable coupling of the cable to the chargeable device.

[0010] Figure 3 is a functional block diagram of an example of a downstream battery-powered rechargeable device, such as one to be charged.

[0011] Figure 4 is a graph of example current consumption of a rechargeable device in several states and two current detection thresholds used to indicate various coupling or charging states.

[0012] Figure 5 is similar to Figure 4 A graph of an example current draw of a rechargeable device is provided, and also showing modulation of the current in two or more portions of the current draw curve.

[0013] Figure 6is a functional block diagram of a charging cable example.

[0014] Figure 7 is a circuit example that can be used Figure 6 is a logic diagram of a charging cable circuit example that controls perceptible visible output to indicate various connection and charging states.

[0015] Figure 8 , 9 , 10, 11, 12, 13, and 14 are example plots of current sensed and indicated as a function of time with respect to two thresholds for several different system states as sensed using circuitry similar to Figure 7

[0016] Figure 15A , 15B and 15C illustrate several timing aspects of current examples in response to state indications using logic circuitry similar to Figure 7 Figure 8 to 14

[0017] Detailed descriptions

[0018] In the following detailed description, for the purposes of completeness, numerous specific details of the present teachings are set forth in order to provide a thorough understanding of the present teachings. However, it will be apparent to one skilled in the art that the present teachings can be practiced without these specific details.

[0019] The following examples are intended to be read in connection with the accompanying drawings that are included herewith as a part of this written description. In the description, relative terms such as "right", "left", "down", "up", "horizontal", "vertical", "above", "below", "upward", "downward", "top", "bottom", and derivatives thereof (e.g., "horizontally", "downwardly", "upwardly", etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. For example, if a device in the figures is inverted, orientations described herein can be inverted accordingly. The application or devices shown in the figures can be manufactured, used, or sold in any orientation. Terms such as "attached", "connected", and "interconnected" as well as other related terms, should not be construed to mean that the structures are directly connected to each other, unless expressly described as being connected directly. Rather, these terms are intended to encompass the structures depicted as being interconnected either directly or indirectly, as well as other orientations that are equivalent.

[0020] Various examples disclosed herein relate to cables for charging battery-powered electronic devices, systems incorporating such cables with chargeable devices, circuitry of the cables, and possibly circuitry in the chargeable devices, to facilitate detection and provision of perceptible indications of various connection and charging states.

[0021] ​​​It is useful to detect coupling of a charging cable to a chargeable device and one or more charging states, and to indicate the detected states to a user of the charging cable and the chargeable device. Some chargeable devices have provided various types of such indications. However, in the examples illustrated herein and shown in the accompanying drawings, a charging cable senses and provides an indication of coupling of the cable to a chargeable device and one or more charging states. In some examples below, the circuitry of such a charging cable provides an indication to a user of whether the cable is connected to a chargeable device, and if connected, whether the system is charging the battery of the chargeable device during a primary charging state. For example, when connected but not charging or charging at a slower rate (i.e., during a secondary charging state), the battery of the device is typically near or at a full charge.

[0022] Depending on the size and configuration of the chargeable device cable head and the cable receptacle, the cable head can only have two prongs in contact with two corresponding contact pads of the receptacle. However, in examples, the charging cable is able to detect whether a chargeable device is connected to the cable and is able to detect at least two charging states based on sensing of current through the prongs when connected, e.g., without the need for additional prongs in the cable head or additional contact pads in the receptacle for sensing the connection or charging states. To be effective and provide a good user experience, these examples provide fast detection of transitioning to each charging state.

[0023] Although other indicator technologies can be used to provide a perceivable output to a user, e.g., to provide a haptic output device for a visually impaired user, typical examples of indicators are low power light emitting diodes (LEDs) or the like that provide a visible light output. The example configurations of the LED indicators below are configured to handle intermittent disconnections gracefully. These examples can also be configured to be of an optimized size, cost, and efficiency.

[0024] These examples detect cable coupling and charging states from the cable side. The detection includes sensing current on the charging circuit (e.g., via only two prongs of the cable head and two contact pads of the receptacle) and comparing the sensed current value to two current thresholds. One threshold is a low connection state current threshold for detecting that a device is connected to the cable head. The other current threshold is set higher for detecting that the device is charging. When disconnected, no current triggers even the low connection state current threshold. Current equal to or above the charging state current threshold (and thus higher than the lower connection state threshold) indicates that the chargeable device is consuming current to charge the battery. Current at least periodically equal to or above the connection state current threshold but below the charging state current threshold indicates a connection that is not supplying charging current or supplying a relatively low charging current, e.g., when the device is at or near a full battery charge.

[0025] Accordingly, in some particular examples, the charging cable includes a logic circuit configured to compare the current level detected by the current sensor to first and second thresholds and control the status indicator in dependence on the comparison over time to detect different system states. The first threshold is higher than the second threshold. When the current level detected by the current sensor is below the lower second threshold, the logic circuit controls the status indicator to provide a first type of perceptible output indicating that the cable head is not electrically coupled to the receiver. When the current detected by the current sensor is equal to or above the higher first threshold, the logic circuit controls the status indicator to provide a third type of perceptible output indicating that the cable head is electrically coupled to the receiver and the current is charging the battery of the chargeable device during a primary charging state. When the current detected by the current sensor is below the first threshold but also equal to or above the second threshold, the logic circuit also controls the status indicator to provide the third type of perceptible output indicating that the cable head is electrically coupled to the receiver but the current is charging the battery of the chargeable device at a lower rate during a secondary charging state.

[0026] In some examples, the chargeable device also pulse-modulates the current it draws from the charging cable to facilitate certain aspects of coupling and charging state detection. In these examples, the circuit of the chargeable device modulates the current drawn through the cable with current pulses to trigger both current sensing thresholds under certain conditions. In some examples, the modulated current pulses have two different pulse amplitudes. For example, during a pre-charge / trickle-charge state, a high current pulse amplitude periodically triggers the higher current threshold for charging state detection. For example, during a lower portion of the constant-voltage state or in an end-of-charge (EOC) state, a lower current pulse amplitude triggers the lower current threshold for connection detection but does not trigger the higher charging state current threshold.

[0027] According to current sensing, the following examples of logic in the charging cable drive an LED-type status indicator to be off (steady off light output condition) when the cable head and cable plug do not detect the device (disconnected, detection current below a low threshold). The LED flashes to indicate that the battery is charging during a primary charging state when the current meets or exceeds a high threshold during any of several possible active charging states (e.g., in a pre-charge / trickle-charge state, a constant-current charging state, or a higher current portion of a constant-voltage charging state). The LED is driven to provide a steady on light output indicating that the cable is electrically coupled to the device but the current is not charging the battery of the chargeable device, or charging the battery at a relatively slow rate during a secondary charging state (the device is connected and, for example, the battery is fully charged or near full charge).

[0028] Reference will now be made in detail to the examples illustrated in the accompanying drawings and discussed below. Figure 1The system 10 includes a rechargeable device 11 and a charging cable 15.

[0029] The rechargeable device 11 includes a device circuit 17, as described below. Figure 3 As shown, the rechargeable device 11 includes a battery and a battery charger circuit coupled to the battery. The rechargeable device 11 also includes a receiver 18 for coupling to the cable head 33 of the charging cable 15. The exemplary receiver 18 allows for rotatable coupling and, for example, includes a cable plug 19 that includes coupled first and second charging contact pads to supply charging current / power to the battery charger circuit. The insulator electrically isolates the contact pads. Figure 2 In the illustrated example, as discussed in greater detail later, the contact pads of plug 19 include a power contact pad coupled to supply current to the battery charger circuit and a ground contact pad coupled to the ground of rechargeable device 11, and may include an insulator electrically isolating the power contact pad from the ground contact pad. However, it will be apparent that the receiver's contacts or contact pads need not strictly be power or ground, and either pad may serve an alternate function. For convenience only, further discussion of this non-limiting example will sometimes refer to a particular contact or pad as a power contact pad and another contact or pad as a ground contact pad. While the description herein describes a specific example of a cable head 33 of charging cable 15 and a cable plug 19 of rechargeable device 11, it should be understood that this is merely an example and that the present invention may utilize other types of connectors to interconnect a charging cable with a rechargeable device, such as a conventional two-wire connector.

[0030] The charging cable 15 includes a connection to a power source. The power connector in this example is a male USB-type connector 21, although other types of connectors and associated power sources can be used. Although not necessarily part of the system 10, the figures also illustrate a compatible power source, which in the example using the USB connector 21 would be a USB power source 23. Examples of USB power sources 23 include a computer, a wall adapter (e.g., an AC charger, sometimes referred to as a "charging brick"), or a car charger, where the female USB port is configured to receive the male USB connector 21 of the charging cable 15.

[0031] The charging cable 15 in the example includes an insulated wire bundle 25 that includes a power bus 27 and a ground bus 29. Other wires or buses can be included for other purposes. In this example, the wire bundle 25 connects a cable circuit 31 to a cable head 33. The connection of the cable circuit 31 to the pins of the USB connector 21 is not separately shown. However, the arrangement recited is a non-limiting example, and other arrangements of cable elements can be used. In alternative configurations, other wire bundles can be present between the USB connector 21 and the cable circuit 31, possibly with other wires (e.g., data bus wires). In another alternative configuration, the cable circuit 31 can be connected to or integrated with the cable head 33, with the power and ground buses internal to the circuit 31 or the cable head 33.

[0032] In the example of rotatable coupling, the cable head 33 has a recess 55 configured to receive insertion of the cable plug 19 when the head 33 of the cable 15 is rotatably coupled to the receptacle 18 of the chargeable device 11. The cable head 33 has a pair of pins 57, 59 to contact pads of the receptacle 18, such as pads on the cable plug 19. Reference is made below to Figure 2 The cable plug 19 and the cable head 33 are discussed in more detail. Examples of cable circuits are discussed later with reference to Figure 6 and Figure 7 .

[0033] The example charging cable 15 also includes an output device or indicator intended to provide information to a user of the system 10 regarding detected connection or charging status. This example uses a light emitting diode (LED) 34 as the indicator. Other light output elements or other types of indicators can be used instead of or in addition to the LED 34. The LED or other indicator is part of the charging cable 15. In the example of Figure 1 the LED 34 is implemented as part of the cable circuit 31, although the indicator can be located elsewhere on the cable 15 (e.g., on the cable head 33, with one or more additional wires between the cable circuit 31 and the cable head 33 to allow the cable circuit 31 to operate the LED 34). Examples of connection and charging status LED indications sensed by the cable circuit 31 are described in more detail below.

[0034] Reference is now made to Figure 2 the example of rotatable coupling. The cable plug 19 is shown as a cylindrical post extending from a wall 41 of the chargeable device's housing or the like. While other shapes can be used, the fairly round cylindrical shape is particularly effective at enabling rotation of a cable head having a mating receptacle recess of appropriate shape. An example of the cable head 33 is shown in the figure, in the form of a cylindrical receptacle 43 that is laterally connected to the end of the wire bundle 25. For convenience, the cable head 33 is shown as being connected to the wire bundle 25 at the end of the wire bundle 25, but the cable head 33 can be connected to the wire bundle 25 at another location along the length of the wire bundle 25. Figure 2The cable circuit is omitted in the middle. In the example illustrated, the cable plug 19 is exposed on the outer surface of the chargeable device housing, and there are no obstructions in the vicinity that can affect or interfere with the rotation of the cable around the cable plug 19 when the plug 19 and the cable head 33 are coupled together for device charging.

[0035] Although not shown, the cable plug 19 can be recessed as part of a receiver in the device, and other elements of the cable (e.g. Figure 1 the wiring harness 25 or the circuit 31 in the middle) can be connected axially to the end of the cable head receptacle 43 (e.g. to the top side in the direction of illustration) opposite the receptacle recess intended to receive the cable plug 19. In this arrangement, the charging receiver on the device will include a cylindrical recess that is slightly larger than the outer side perimeter of the cylindrical receptacle 43, and the cable plug 19 will be located approximately at the center of this recess. However, if the chargeable device does not have a receiver with such a cylindrical recess, the outer shape of the receptacle 43 need not be cylindrical, and can have some other design or shape, for example, to facilitate user gripping of the cable head receptacle 43 to couple or remove the receptacle 43 to or from the cable plug 19, or to turn the receptacle 43 around the axis of the cable plug 19.

[0036] The cable plug 19 is configured to be inserted into a cylindrical recess 55 Figure 1 that is formed in the receptacle 43 of the cable head 33. The cable plug 19 includes two charging contact pads of a suitable electrically conductive material (e.g. metal) separated by an insulator (e.g. a suitable plastic). Various configurations of contact pads and separators can be used. Figure 2 The example of the middle uses a post 45 made of plastic or other insulating material. The shape of the post 45 is generally cylindrical. Each contact pad 47 and 49 is formed of an electrically conductive material such as metal. At least some surface area of each contact pad 47, 49 is exposed to enable possible electrical contact Figure 1 by one or more prongs 57, 59 located in the receptacle 43 of the example cable head 33. As Figure 2 shown, the contact pads 47, 49 are positioned to provide exposed contact surfaces at different locations around the cylindrical side of the post 45 of the cable plug 19. In the direction of illustration, a first (1) charging contact pad 47 is mounted on the left side of the cylindrical side of the post 45, and a second (2) charging contact pad 49 is mounted on the opposite (right) side of the cylindrical side of the post 45.

[0037] The metal forming the contact pads can be deposited on the cylindrical side of the post 45, in which case the contact pads 47, 49 can be slightly raised or extended outward from the cylindrical side of the post 45. Alternatively, the metal forming the contact pads 47, 49 can be embedded in the material of the post 45 and have a thickness so as to form a smooth cylindrical side of the plug 19. In another alternative example, the metal forming one or both of the contact pads 47, 49 can be embedded sufficiently to form one or more slight depressions in the cylindrical side of the plug 19. In any of these configurations, however, the surface of the contact pads 47, 49 is exposed for mechanical and electrical contact with pins included in the cable head receptacle 43 (e.g., pins 57 and 59 as in Figure 1

[0038] In the example of Figure 2 , the insulating material of the post 45 provides structural support for the contact pads 47, 49 and forms a partition between the contact pads to electrically isolate or separate the contact pads 47, 49 from one another. The insulating material partitions the metal of the contact pads (and the like) on opposite sides of the plug structure (e.g., laterally across the vertical axis of the cylindrical post 45 in the illustrated direction). The example plug structure has exposed portions on the cylindrical side of the insulating material of the post 45 between adjacent ends of the exposed surfaces of the contact pads 47, 49. One of the exposed portions between the ends of the contact pads 47, 49 in the exposed portion 51 on the cylindrical surface of the post 45 is visible in the illustrated direction. A second similar portion is on the opposite (back) face of the cylindrical post 45 and is not visible in the figure.

[0039] Each exposed insulating region 51 can be relatively small so as to minimize the size of any potential dead zone. For example, the region 51 can be only large enough to avoid current flow from the end of one contact pad to the adjacent end of the other contact pad through the region. In another example, the region 51 can be slightly wider than the width of the pins 55, 57 (or the width of the largest of the pins 57, 59) of the cable head 33 so that the pins in the cable head cannot simultaneously contact both of the contact pads 47, 49.

[0040] Figure 3 is a functional block diagram of an example of the components of a chargeable device 11 power supply battery, here including the device circuitry 17 and the cable plug 19 (as a receiver or as part of a receiver). While other receiver and contact pad arrangements can be used, the example of Figure 3 the cable plug 19 in the device example can be as described above with respect to the example of Figure 2 ​The implementation under discussion thus includes two charging contact pads. For such an example configuration, the contact pads of the power source are coupled to supply power to the battery charger circuit 63 at the VBUS port. The other contact pad is connected to the ground of the chargeable device 11. The device circuit 17 includes the battery 61 and the battery charger circuit 63 coupled to the battery 61. Various known circuits can be used to implement the battery charging circuit 63, for example, based on the type and size of the battery 61. The positive terminal of the battery 61 is connected to the battery charger circuit 63, and the negative terminal of the battery 61 is connected to the ground of the chargeable device 11.

[0041] For convenience, the device electronics (if any) that can consume power of the battery 61 for general functions of the device (other than the charging functions considered herein) are omitted. The charging cable and charging techniques discussed here can be applied to any of a variety of portable or wearable devices that utilize a chargeable battery to power a particular electronic component or act as a battery pack to charge other devices.

[0042] The device circuit 17 in the example also includes a first switch 65 and a second switch 66 coupled to draw current from the battery charger circuit 63. The switches 65, 66 in this example are controlled to selectively shunt additional current to ground, which causes the particular type of battery charger circuit 63 to add two different amplitudes of pulses to the current flowing through the charging path formed by the cable plug 19 and the cable tip 33. Any switching device configured to switch an appropriate amount of current can be used, such as any of a variety of switching transistors. This figure, for example, shows a field effect transistor (FET) as the switch 65 and a field effect transistor (FET) as the switch 66.

[0043] A variety of switches to the battery charger 63 can be used, and possibly a variety of intervening or related circuit elements can also be used. In this example, the switch 65 is connected to the switch (SW) port of the battery charger circuit 63 via a resistor Rl and an inductor LI. Similarly, the switch 66 is connected to the switch (SW) port of the battery charger circuit 63 via a resistor R2 and an inductor LI. A path is also provided from the connection point between the inductor LI and the resistors Rl, R2 to the system voltage port (VSYS) of the battery charger circuit 63. Each switch 65 or 66 in this example is connected in series to the ground of the chargeable device 11 from the resistor Rl or R2. The device circuit 17 also includes a device controller that provides a signal (PWM_pulse) to control the switch 65 and a signal (PWM_trickle) to control the switch 66. Although discrete logic, a field programmable gate array, other programmable processor, etc. can be used, this example utilizes a programmable microcontroller (MCU) 67 as the controller of the chargeable device 11.

[0044] The resistors R1 and R2 are selected so that the pulse provided by closing switch 66 is higher than the pulse created by closing switch 65. Also, the resistance values are selected so that the addition of the pulses in the different states will exceed the different thresholds when added to the regular current consumption by the battery charger circuit 63. For example, when the cable 15 is coupled via the receiver to the head of the charging cable 15, the peak of the pulse added to the low current via the operation of switch 65 and resistor R1 will periodically meet or exceed the low current threshold I_detect for detecting the connection. In this example, when the cable 15 is coupled via the receiver to the head of the charging cable 15, the peak of the pulse added to the current equal to or higher than the low current threshold but possibly not triggering the higher charge state current threshold I_chg will cause the modulated current to periodically meet or exceed the higher charge state current threshold I_chg. The threshold levels and the pulse amplitudes (and thus the values of resistors R1 and R2) will be selected based on the charging requirements of the particular type of battery 61 used in the particular chargeable device 11.

[0045] The two switches and associated resistor / inductor circuits are given by way of non-limiting example only; other circuit arrangements can also be used for pulse-modulating the current consumption so that it has two different amplitudes in the different states of the charging current profile. For example, an alternative approach can use a single switch controlled by the MCU 67 and a variable impedance device in series with the switch, where the impedance is set to different impedance values (to establish different pulse amplitudes) in the different states of the charging current profile.

[0046] As mentioned previously, the device circuit 17 also includes a device controller, exemplified by the MCU 67. The MCU is typically a System on Chip (SoC) that includes a processor, memory, peripheral input / output (I / O) interfaces and ports, and possibly other circuit components. For example, a single SoC can incorporate both the battery charger circuit and the circuit forming the MCU. For the purposes of the present discussion, the MCU 67 controls functions related to battery charging, although the MCU can perform other functions related to the device 11 depending on the type of device or the application of the particular electronic device 11. It will be apparent, however, that other controller implementations can be used. The functions of the MCU 67 are determined by executable program instructions or configuration data (e.g. firmware) installed in the memory of the MCU.

[0047] In the example chargeable device 11, the MCU 67 forming the device controller is responsive to power from the cable plug 19 and is configured to operate the switches 65, 66 to pulse-modulate the current through the cable plug 19 by the charger circuit 63, thereby providing state indications to the circuit 31 of the charging cable 15 (see Figure 1In this example implementation for supporting state detection, MCU 67 controls battery charger circuit 63, configures device circuit 17 to implement a regulated current profile for charging battery 61 over a time interval, and adds modulated current pulses to the current flowing through cable plug 19 and charging cable 15 during portions or subintervals of the current draw profile.

[0048] Figure 4 It is used to charge the battery Figure 1 and 3 A graph of an example current draw of an example rechargeable device 11 (shown without optional pulse modulation). The currents at various stages of the graph are given by way of example only. The device 11 may implement different currents or graphs with different stages, for example, to address the charging requirements of a particular type of battery 61 for a particular rechargeable device 11.

[0049] refer to Figure 4 For example, when the device 11 is coupled to the charging path via the cable plug 19, the regulated current is realized Figure 4 Several states of the graph. In the initial portion of the example graph (e.g., during a subinterval when there is a connection to the cable 15 but the charge on the battery 61 is above a certain percentage), the battery charging circuit 63 consumes approximately 100 mA for pre-charge or trickle charge current. At a later time (the second portion of the graph), for example, when certain conditions for MCU operation or battery charging are met, the battery charging circuit 63 enters a primary charge state (e.g., consuming a constant charge current of approximately 500 mA for rapid full-power charging of the battery 61). At a later time, for example, when the battery reaches a certain threshold of charge percentage, the battery charging circuit 63 enters a secondary charge state (e.g., consuming current to apply a constant voltage to the battery 61). In this third portion of the graph, while the voltage remains constant, the current decreases until the battery is fully charged and the device 11 reaches the end-of-charge (EOC) portion of the graph, consuming minimal current. The current values ​​shown in the various portions of the graph are examples only, and other values ​​would apply, for example, when charging other types of batteries 61.

[0050] Figure 4 Also shown is a circuit 31 of the charging cable 15 for state current response detection ( Figure 1) examples of two current thresholds used. The first current detection threshold (I_chg) is used for primary charging state detection. The second current detection threshold (I_detect) is involved in connection state detection. The first current threshold I_chg is higher than the second current threshold I_detect. Detecting a current value below the threshold I_detect indicates that the charging cable 15 is not connected to the chargeable device 11. Any current equal to or above the second current threshold I_detect (including current equal to or above the higher first current detection threshold I_chg) indicates that the charging cable 15 is connected to the chargeable device 11. Thus, a current value equal to or above the second lower threshold I_detect indicates that the charging cable 15 is connected to the chargeable device 11, and a current value equal to or above the first higher threshold I_chg indicates that the battery charging circuit 63 is consuming current to charge the battery 61 during the primary charging state. A current value equal to or above the threshold I_detect but below the threshold I_chg indicates that the charging cable 15 is connected to the chargeable device 11, but the battery charging circuit 63 is not consuming current to charge the battery 61 (see Figure 3 ) or the battery charging circuit is in the secondary charging state.

[0051] As described above, when the battery is sufficiently charged (e.g. fully charged or near fully charged), in the illustrated EOC state, current needs to be sensed to indicate to the cable circuit 31 that the chargeable device 11 is still electrically connected to the charging cable 15. Various techniques can be used to facilitate such detection. For example, the chargeable device can be configured to consume a low current sufficient to trigger the I_detect threshold. If a current sensor with a sufficiently low threshold is used, then any current can work. For example, the idle system current consumption of the chargeable device 11 can be sufficient by itself to trigger the I_detect threshold depending on the type, configuration or application of the chargeable device. Similarly, current needs to be sensed as an indication to the cable circuit 31 that the chargeable device 11 is charging its battery 61 at all charging states of the graph, and various techniques can be used to facilitate such detection. For example, the I-chg charging state current detection threshold can be set to be higher than the connection state current threshold I_detect but lower than Figure 4 a pre-charge / trickle current (e.g. below 100 milliamps) in the example current consumption graph.

[0052] To reduce power consumption in low current states, the example chargeable device consumes as low an idle system current as possible for the device circuitry. Rather than setting the connection state current threshold I_detect low to detect such idle state currents, which can result in false connection detection due to static or noise, the cable circuit 31 utilizes a Figure 4 and 5a slightly higher connected state current threshold Idetect. In such a system example, the cable circuit 31 utilizes a connected state current detection threshold I-chg that is slightly higher than the pre-charge / trickle current, to provide a larger distinction between the thresholds, and to avoid noise in the idle state inadvertently triggering the I-chg connected state current detection threshold. Instead of relying only on regular current consumption to trigger the relevant threshold in all states of the current consumption graph, as Figure 4 and 5 example implementations of the threshold add pulse modulation to the current consumption Figure 5 ) in the connected state.

[0053] Non-limiting examples show a current detection threshold for connection detection (I_detect) of about 60 milliamps, and an example shows a current detection threshold for charge detection (I_chg) of about 300 milliamps. These thresholds are suitable for a particular type or technology of battery 61 and a related type of battery charging circuit 63. Other thresholds are selected for use with other battery types and corresponding charger circuits.

[0054] With respect to the example graph as shown in Figure 4 , the current consumed through the charging path of the cable head and cable plug exceeds the I_detect threshold in the pre-charge or trickle state, the constant current state, and most of the constant voltage state. As the battery approaches full charge in the later part of the constant voltage state, the current consumed through the charging path of the cable head and receiver drops below the I_detect value used by the cable for connection detection. In addition, the current consumption in the end of charge (EOC) state is below the I_detect value used by the cable for connection detection. Thus, in the low current portions of the constant voltage state and the EOC state, the current is too low to trigger connection detection. Also, the current in the pre-charge or trickle state and a portion of the constant voltage state drops below the I_chg threshold used to detect charging, even though the battery charger circuit 63 is consuming charging current. To address the situation where the actual current consumed by the chargeable device 11 does not trigger the appropriate threshold, Figure 3 example device circuit 11 introduces periodic pulse modulation via the periodic operation of switches 65 and 66. An example of such modulation is shown in Figure 5

[0055] ​In general, if the current consumed by the chargeable device 11 can fall below the I_detect threshold used by the cable circuit 31, the addition of the periodic pulses causes the peak of the modulated current to reach or exceed the I_detect threshold. Similarly, if the current consumed by the chargeable device in at least one charging state can reach or exceed the I_detect threshold used by the cable circuit 31, but does not reach or exceed the I_chg threshold used by the cable circuit 31, the addition of the periodic pulses causes the peak of the modulated current to reach or exceed the I_chg threshold.

[0056] Figure 5 is a graph of example current consumption for a chargeable device similar to Figure 4 but also shows an example of such pulse modulation of the current. As described above with respect to Figure 3 the MCU 67 operates the switch 65 to pulse modulate the current through the cable plug 19, adding pulses of one amplitude, and operates the switch 66 to pulse modulate the current through the cable plug 19, adding pulses of another amplitude. Although the relationship of the two amplitudes can vary, for example for different applicable thresholds or for different currents at different stages of the applicable current consumption graph, the pulse amplitude provided by operation of the switch 66 (the first pulse amplitude) is higher than the pulse amplitude provided by operation of the switch 65 (the second pulse amplitude). The resulting pulses of both amplitudes increase the current consumed by the device 11, triggering the connection detection and charge detection thresholds used by the cable circuit 31 as appropriate.

[0057] Referring to Figure 3 and 5 , when the switch 65 is in its open state, the battery charger circuit 63 consumes current as shown in Figure 4 . Each time the switch 65 is periodically closed, current flows through the switch 65 to ground, causing the battery charger circuit 63 to consume an additional amount of current through the charging path formed by the cable plug 19 and the cable tip 33 to add pulses of a second amplitude (determined by the resistance of Rl). Switching back and forth between the open and closed states of the switch 65 produces pulses of the first amplitude and causes the battery charger circuit 63 to superimpose the corresponding pulses on the current through the charging path formed by the cable plug 19 and the cable tip 33. Similarly, each time the switch 66 is periodically closed, current flows through the switch 66 to ground, causing the battery charger circuit 63 to consume an additional amount of current through the charging path formed by the cable plug 19 and the cable tip 33 to add pulses of a first, higher amplitude (determined by the resistance of R2). Switching back and forth between the open and closed states of the switch 66 produces pulses of the second amplitude and causes the battery charger circuit 63 to superimpose the corresponding pulses on the current through the charging path formed by the cable plug 19 and the cable tip 33.

[0058] The amplitude of the modulation pulses resulting from the operation of switch 65 depends on the value of resistor Rl. The value of Rl is selected to provide a low amplitude current pulse for addition to the current that will be above the threshold I-detect in the low current state, e.g., sufficient to detect in the low current connection state at the end of charge (EOC) state of the battery as shown in Figure 5 .

[0059] The amplitude of the modulation pulses resulting from the operation of switch 66 depends on the value of resistor R2. The value of R2 is selected to provide a slightly higher amplitude current pulse for addition to the current in at least one charging current state that is above the connection detection threshold I-detect but can be below the charge state detection threshold I_chg (without the pulse). For example, in the pre-charge or trickle charge state, the added pulse provides sufficient to detect the periodic current amplitude of the battery charge as shown in Figure 5 .

[0060] The lower amplitude pulses resulting from the periodic closure of switch 65 are added to the current draw during the lower portion of the constant voltage portion of the example current draw graph and during the EOC state. The peaks of those lower amplitude pulses of the modulated current rise to equal or above the I-detect threshold. Based on the proper timing of the cable circuit 31, the cable 15 is able to sense the peaks of the current pulses that periodically exceed the I-detect threshold in order to maintain an indication of the connection of the cable head 33 to the cable plug 19, e.g., if the MCU or battery charger circuit determines to increase the charging current, showing the availability of the charging path. For the user, an LED or the like provides an output that generally informs the user that the battery is fully charged.

[0061] The graph represents an example in which the higher amplitude pulses resulting from the periodic closure of switch 66 are added to the current draw during the pre-charge or trickle charge portion of the graph. The peaks of those higher amplitude pulses of the modulated current rise to equal or above the I_chg threshold. Based on the proper timing of the cable circuit 31, the cable 15 is able to sense the peaks of the current pulses that periodically exceed the I_chg threshold in order to maintain a charge indication during the pre-charge or trickle charge portion of the graph.

[0062] Figure 6 is a functional block diagram of an example of a charging cable 15 with current sensing for state detection and a state indicator. Connection to a USB type power source (see Figure 1 ) includes a current sense as shown in Figure 6Power bus 27, shown as VBUS, is used for USB-compatible connections. The wiring to a USB-type power source also includes a ground bus 29. Cable circuit 31 in this example includes a protection circuit 71 that provides one or both of over-voltage protection (OVP) or over-current protection (OCP). Power from protection circuit 71 flows through a current sensor 73 to power pin 57. Ground bus 29 is connected to ground pin 59.

[0063] Cable circuit 31 includes an LED 75, which in this non-limiting example acts as a status indicator. LED 75 is connected to power on the protected side of OVP / OCP circuit 71. LED 75 is connected to ground bus via one or more switches controlled by a logic circuit 77. This example shows two switches 79 and 81. Of course, other arrangements of LED, switches, and their connections to power and ground can be utilized. In this example, logic circuit 77 provides a pulsed signal (LED_PWM) to open and close switch 79 periodically, producing a perceivable flickering light output from LED 75 for a status indication when device 11 is actively charging battery 61 with sufficient current. Logic circuit 77 provides a steady state signal (LED_SOLID) to close switch 81, producing a perceivable steady-on light output from LED 75 for a device-connected but not charging status indication, such as when battery 61 is fully or nearly fully charged at EOC in a secondary charging state. Logic circuit 77 provides a steady state signal to both switches 79, 81 to open both switches 79, 81, leaving the LED off (not producing light steadily) as a perceptible indication of no detected connection between cable 15 and a chargeable device.

[0064] In Figure 6In the example shown, switches 79 and 80 are connected in parallel from LED 75 to ground at 29. The LED light output is off only when both switches are open. If one or both of switches 79 and 80 are closed, light is emitted. For example, to provide a blinking LED output from LED 75, logic circuit 77 periodically opens and closes switch 79 while simultaneously opening switch 81. If switch 81 is continuously closed, LED 75 will provide a continuous light output. Switch 79 can be open while switch 81 is continuously closed, or switch 79 can still be periodically opened and closed. Switches 79, 81, and LED 75 are configured so that the closed switch 81 effectively overrides the operation of switch 79. For example, LED 75 may have a current limit that is maximum when switch 81 is closed, in which case, when switch 79 is periodically closed, no current is drawn even if some of the maximum current through LED 75 flows through the closed switch 79. Even though there is some additional current flowing each time switch 79 is closed, components 75, 79, 81 are configured so that any increase in light output from LED 75 is sufficiently low that this additional periodic light output would appear imperceptible to a typical user. Thus, even though switch 79 is periodically operated, when switch 81 is closed, the light output from LED 75 appears to be steadily on.

[0065] Figure 7 An example of a discrete logic circuit arrangement for implementing the current responsive logic circuit 77 is illustrated. As previously mentioned, current sensing for state detection can be implemented without pulse modulation. However, in Figure 7 In the example logic of FIG. 1 , the logic implements timing associated with detection of a pulse modulated current.

[0066] The functions of the logic circuit 77 can be implemented in other ways, such as using an MCU or other programmed processor. Figure 7 The example logic circuit 77 is configured to sense and indicate a signal similar to Figure 5 The battery charging circuit and MCU can be configured to generate different current consumption profiles, such as for different types of batteries, in which case the logic circuit 77 of the charging cable 15 can be appropriately modified to sense the different current consumption profile states.

[0067] Reference Figure 6 and 7 The illustrated example of the switching logic circuit 77 includes two comparators 85 and 87. The voltage Isense ( Figure 6) proportional to the instantaneously sensed current, and the Isense voltage is coupled to the input of each of comparators 85 and 87. Comparator 85 determines whether the Isense voltage reaches or exceeds an I_det reference voltage proportional to the lower current threshold I_detect used for connection state detection. Comparator 85 provides a relatively high output voltage (e.g., 1) when the voltage Isense representing the sensed current is equal to or higher than (greater than or equal to) the reference voltage I_det. If Isense is lower than the I_det reference, then comparator 85 outputs a low voltage (e.g., 0). Comparator 87 determines whether the Isense voltage reaches or exceeds an I_chg reference voltage proportional to the higher current threshold I_chg used for charge state detection. Comparator 87 provides a relatively high output voltage (e.g., 1) when the voltage Isense representing the sensed current is equal to or higher than (greater than or equal to) the reference voltage I_chg. If Isense is lower than the I_chg reference, then comparator 87 outputs a low voltage (e.g., 0). Comparators 85, 89 have sufficient responsiveness to respond to the peak and trough of pulses of two different amplitudes modulating current draw in different states, as shown in the examples in Figure 5

[0068] For example, if cable 15 is connected to chargeable device 11, then comparator 85 will provide a steady high output voltage during the entire pre-charge / trickle state, the entire constant current state, and the higher current portion of the constant voltage state. Comparator 85 will provide a periodically pulsed high-low output in response to the pulsed modulation of current by device 11 during the lower current portion of the constant voltage state and the end of charge (EOC) state. When there is no device 11 connected to cable 15, comparator 85 will provide a low output when there is no current (or no pulses) to trigger the low I_detect threshold.

[0069] In this example, comparator 89 will provide a high output voltage during the entire constant current state and the higher current portion of the constant voltage state. Comparator 89 will provide a periodically pulsed high-low output in response to the pulsed modulation of current by device 11 during the pre-charge / trickle state. Comparator 89 will provide a low output when there is no current (or no pulses) to trigger the higher I_chg threshold. The low output will include the lower current portion during the constant voltage state and the end of charge (EOC) state, and any time when there is no device 11 connected to cable 15.

[0070] Example state sensing and indication logic 77 includes a coupled delay circuit 89 to receive the output of comparator 85. Circuit 89 implements a delay time interval t_DET relative to each falling edge of the comparator 85 output (e.g., in response to each transition when the value Isense representing the sensed current falls below the I_det threshold).​

[0071] The example status sensing and indication logic 77 also includes a pulse width modulation (PWM) type drive circuit 91 for outputting a periodic signal, in this case, the LED_PWM signal for periodically closing and opening the switch 79 and periodically flashing the light output on and off. The PWM drive circuit 91 receives the output from the delay circuit 89 to activate / deactivate the pulsed signal output of the drive circuit 91 to activate / deactivate the flashing output of the LED 75.

[0072] The example status sensing and indication logic 77 also includes an inverter 92 coupled to one input of an AND gate 93. The output of the comparator 87 is connected to the inverter 92 so that the inverted comparator signal is applied to one input of the AND gate 93. The AND gate 93 receives the output from the delay circuit 89 on the other input of the AND gate 93.

[0073] The example status sensing and indication logic 77 also includes another delay circuit 95 implementing a delay time interval t_CHG. The output of the AND gate 93 goes to an input of the delay circuit 95 and the output of the delay circuit 95 goes to a latch 97. The latch 97 toggles between high and low output states in response to the signal from the delay circuit 95 and holds these states, respectively. The output of the latch 97 is the LED_SOLID signal that operates the switch 81. When the latch output is high, the signal closes the switch 81 and as long as the latch 97 holds the high state output, the LED 75 is on, presenting a steady on state. When the latch output is low, the signal opens the switch 81 and as long as the latch 97 holds the low state output, the LED 75 is off, presenting a steady off state.

[0074] Further discussion will refer to the various timing diagrams of Figure 6 and 7 as well as Figure 8 to 14 simultaneously. A general discussion of the logic is first presented, but the processing portion of the current draw graph that includes the current modulation pulses has not yet been addressed. The aspects of the delay intervals with respect to the different amplitude modulation pulses parameters will be addressed later.

[0075] In general, when the voltage Isense representing the sensed current is below the reference voltage I_det for a significant period of time, as shown in Figure 8 , the comparator 85 outputs a low voltage (e.g., 0). In response, the delay circuit 89 outputs a low voltage (e.g., 0). The driver 91 remains off and there is no signal on the LED_PWM lead to operate the switch 79. The switch 79 remains open. In this state, the voltage Isense representing the sensed current is also below the reference voltage I_chg for a significant period of time, as shown in Figure 8As shown, and comparator 87 outputs a low voltage (e.g., 0). While inverter 92 will provide a high (e.g., 1) value on one input of AND gate 93, AND gate 93 outputs a low voltage (e.g., 0) in view of the low (0) input from delay circuit 89. In response to the low (0) output from AND gate 93, delay circuit 95 outputs a low voltage (e.g., 0), and latch 97 outputs a low voltage (e.g., 0) on the LED SOLID lead to switch 81. Switch 81 remains open. In this state where both switches are open, no current flows through LED 75, and there is no light output (solid off), which serves as a perceptible indication that no chargeable device 11 is connected to charging cable 15.

[0076] When the voltage Isense representing sensed current is equal to or greater than (greater than or equal to) the reference voltage I_det, comparator 85 outputs a higher voltage (e.g., 1). In response, delay circuit 89 outputs a higher voltage (e.g., 1) to activate pulsed LED driver 91. Driver 91 outputs pulses on lead LED PWM to periodically open and close switch 79. Assuming switch 81 is open at this time, pulsed current will flow through LED 75 when switch 79 is open and closed, causing LED 75 to provide a pulsed or "breathing" light output at least indicating that a chargeable device 11 is connected to charging cable 15. However, in this example, logic 77 is configured to apply the I_chg threshold so as to enable the pulsed output from LED 75 further indicating that the connected chargeable device 11 is charging the battery 61 of device 11.

[0077] When there is a chargeable device 11 connected to charging cable 15 and the voltage Isense representing sensed current is equal to or greater than (greater than or equal to) the I_chg reference voltage, the illustrated logic Figure 7 keeps switch 81 open (see Figure 9 ). Current will steadily exceed both thresholds, as Figure 9 shown (charge, LED blinking), for example, during the constant current portion of the graph shown in Figure 4 and 5 . In Figure 9In the state depicted, the flashing light produced by the driver 91, switch 79, and LED 75 indicates that the connected device 11 is consuming current to charge the battery. For the logic circuit illustrated, when the voltage Isense representing the sensed current is equal to or greater than (greater than or equal to) the charge state reference voltage I_chg, the comparator 87 outputs a higher voltage (e.g., 1), which inverter 92 inverts to a low voltage (0) on the input of the AND gate 93. Although the lower I_det threshold of the comparator 85 is triggered due to the voltage Isense, the other input of the AND gate 93 is high (1), but due to the low (0) input from the inverter 92, the AND gate 93 outputs a low voltage (0). In response to the low (0) output from the AND gate 93, the delay circuit 95 outputs a low voltage (e.g., 0), and the latch 97 outputs a low voltage (e.g., 0) on the LED SOLID lead to the switch 81. The switch 81 remains open. In this state where the current is equal to or above the higher I_chg threshold for charge state detection, the logic 77 keeps the switch 81 open, which indicates that the flashing light of the LED 75 indicates that the device is charging.

[0078] As mentioned above, Figure 9 represents a situation where the current is continuously above the higher I_chg threshold, such as during the constant current phase of the current consumption graph. The pre-charge / trickle phase of the current consumption graph presents a different scenario, which the example device circuit 17 and cable circuit 31 handle by modulating the addition and detection of pulses. Figure 10 is an example of pulse-modulated current and threshold in the pre-charge state. The device 11 is connected to the cable 15, and the device 11 is consuming some current to charge the battery 61. As will be discussed later, Figure 11 shows similar pulse timing for lower amplitude pulses added during the low current portion of the constant voltage portion and during the EOC portion of the current consumption graph. Figure 5 ).

[0079] In general, the time interval that the modulated pulse is high is referred to as t_high, and the time interval that the modulated pulse is low is referred to as t_low. While these time lengths can vary between pulses of different amplitudes, the figures (e.g. Figure 10 and 11 ) show examples where t_high and t_low are substantially the same for the respective high and low levels of both types of pulses.

[0080] Now turning specifically to the pre-charge state, Figure 10 (pre-charge, LED flashing) shows pulse timing for higher amplitude pulses added during the pre-charge portion of the current consumption graph. Figure 5 ). The chargeable device circuit 17 Figure 4) configured to operate switch 66 to produce a sufficient amount of modulation pulses such that the current in the pre-charge state periodically rises above the charge state threshold I_chg. In addition, the current is continuously above the connection state threshold I_det, but below the charge state threshold, except when the current sensor 73 detects a peak amplitude of a current modulation pulse.

[0081] The purpose of the pre-charge state is to provide a blinking LED output as an indication of connection and charging, very similar to the state discussed above with respect to Figure 9 For this purpose, the PWM driver 91 will periodically open and close switch 79, thereby pulsing the current through LED 75. As discussed above with respect to Figure 9 the voltage Isense representing the sensed current is equal to or above the reference voltage I_det, the comparator 85 outputs a higher voltage (e.g., 1), and the delay circuit 89 outputs a higher voltage (e.g., 1) to activate the blinking LED driver 91 and periodically open and close switch 79. At the same time, in this state, switch 81 will remain open (so as not to override the pulsing via operation of switch 79).

[0082] As discussed above, when the current is above the threshold I_det, the outputs of comparator 85 and delay circuit 89 are high, and the AND gate 93 receives a high input from delay circuit 89. Whenever the voltage Isense representing the sensed current is equal to or above the reference voltage I_chg, the comparator 87 outputs a higher voltage (e.g., 1), which inverter 92 converts to a low voltage (0) at the input of AND gate 93. In Figure 10 the state illustrated, the comparator 87 outputs a higher voltage (e.g., 1) in response to each peak of a current modulation pulse that causes the sensed current to meet or exceed the I_chg threshold. Otherwise, the comparator 89 outputs a lower voltage (e.g., 0). Thus, the output of the comparator is a series of pulses that substantially corresponds to the timing of the Figure 10 current pulses, and inverter 92 provides an inversion of the pulse string output of comparator 89 to one input of AND gate 93. With the input from delay circuit 89 continuously high, the output of AND gate 93 tracks the input received from inverter 92, i.e., the inversion of the output of comparator 89, and thus tracks the inversion of the modulation current pulses of Figure 10

[0083] ​The arrangement of inverter 92 and AND gate 93 is as shown, with the output of AND gate 93 going high almost simultaneously with the current pulse (and thus the output of comparator 87) going low; the output of AND gate 93 going low almost simultaneously with the current pulse (and thus the output of comparator 87) going high. The pulses only periodically trigger the charge state threshold I_chg. In the logic path to the LED_SOLID lead of control switch 81, delay circuit 95 implements a delay t_CHG, which can be adjusted to match the parameters of the higher amplitude current modulation pulses. The delay interval t_CHG prevents state changes in the interval between pulses that exceed the I_chg threshold (less than or equal to the duration of t_CHG), and thus keeps the output of latch 87 low and switch 81 open during the pre-charge phase of the current draw graph.

[0084] Delay circuit 95 is configured so that its output normally has a high value (e.g., represents a 1) when the output of AND gate 93 has a high value (e.g., 1 when both inputs to AND gate 93 are 1s). Delay circuit 95 is configured so that its output normally has a low value (e.g., represents a 0) when the output of AND gate 93 has a low value (e.g., 0 when at least one of the inputs to AND gate 93 is 0). The output of delay circuit 95 is intended to be low in the charge state. For the pre-charge state, delay circuit 95 is configured so that the output of circuit 95 changes from low to high in response to a rising edge of the gate 93 output (corresponding to a falling edge of the current pulse), but only after the delay interval t_CHG expires following the transition of the AND gate 93 signal output. However, if the input to circuit 95 goes low again (corresponding to a rising edge of a subsequent current pulse) before the delay interval t_CHG expires, circuit 95 resets the count of the delay interval. In this way, if there is another current pulse represented by a low output of AND gate 93, delay circuit 95 keeps latch 97 set to output a low signal to keep switch 81 open, so that the flickering of the LED output from PWM driver 91 and switch 79 is not overridden.

[0085] The pulse-related timing aspects implemented by the actual example logic circuit 77 in the EOC state are next discussed. In the connected state, there is not enough current for active charging of the battery, with the current detected by the current sensor being below a higher first threshold, but still equal to or above a lower second threshold. Before discussing the implementation of the pulse modulation, consider an example (not shown) in which the idle current in the EOC state of the device is above the low connected state detection threshold I_det (e.g., as if the EOC current were higher in Figure 4 Figure 4 the example of FIG. 6, or in the example of FIG. 7, in which the EOC current is lower, or in the example of FIG. 8, in which the EOC current is lower.the charging circuit 63 of the device 11 does not charge the battery 61. Thus, the voltage Isense representing the sensed current is below the reference voltage I_chg for a substantial period of time, and the comparator 87 outputs a low voltage (e.g., 0). The inverter 92 will provide a high (e.g., 1) value on one input of the AND gate 93. The voltage Isense representing the sensed current is equal to or above (greater than or equal to) the reference voltage I_det, and the comparator 85 outputs a higher voltage (e.g., 1). In response, the delay circuit 89 outputs a higher voltage (e.g., 1) to the other input of the AND gate 93. With high (1) values on both inputs, the AND gate 93 outputs a high (1) value. The output of the delay circuit 95 goes high (1), activating the latch 97 to output a voltage on the LED_Solid lead to close the switch 81. While the EOC state persists, the latch output remains high, the switch 81 remains closed, and current flows steadily through the LED 75 to indicate that the connected device 11 is connected, but is not charging or is charging at a relatively low rate during the secondary charging state, e.g., the battery is in a fully charged (EOC) state. While the switch 79 is open and closed in this state, the persistent closure of the switch 81 effectively overrides the pulses via the switch 79, so that the visible indication appears as a steady on.

[0086] The state example at completion of charging in the system is accomplished by using the example circuit, Figure 11 (Full Charge, LED On) shows the pulses of current when the battery charger has reached the end of charge (EOC) low current state (see also Figure 5 ) including the current modulation pulses from the chargeable device 11. Again, the time interval when the modulation pulses are high is referred to as t_high, and the time period when the modulation pulses are low is referred to as t_low. The chargeable device circuit 17 Figure 4 is configured to operate the switch 65 to produce the modulation pulses. In this state, the low amplitude modulation pulses do not trigger the charging state current threshold I_chg. However, the low amplitude modulation pulses have a sufficient amount that the current periodically rises above the I_det threshold. Thus, the peak values of the Isense output voltage exceed the I_det reference voltage used by the comparator 85 Figure 7 , resulting in a periodic comparator high output to the delay circuit 89 input, in turn activating the PWM driver 91 to pulse current to the LED 75 via the switch 79. The delay interval t_DET keeps the output of the delay circuit 89 high for as long as any period between pulses has a duration less than t_DET, and thus provides a steady higher voltage (1) to the input of the AND gate 93.

[0087] As Figure 11As shown, in this state, the I_sense voltage representing the sensed modulated current does not exceed the higher I_chg threshold, indicating that the device 11 is not charging the battery via the cable 15. The comparator 87 outputs a low voltage (0), which the inverter 91 converts to a high voltage (1) input to the AND gate 93. The AND gate 93, delay circuit 95, and latch 97 Figure 7 ) close the switch 81 Figure 6 ) so that there is a constant current flowing through the LED 75. The constant current provided by closing the switch 81 effectively overrides the pulsed current through the switch 79. Thus, the LED provides a steady on light output indicating a connection but not charging, e.g., the battery 61 is fully charged or near full charge.

[0088] As described above, the output of the comparator 85 enters the delay circuit 89. The delay circuit 89 is configured so that the output of the circuit 89 normally has a high value (e.g., represents a 1) when the output of the comparator 85 has a high value (e.g., is 1 when the sensed current value Isense reaches or exceeds the I_det threshold). The delay circuit 89 is further configured so that the output of the circuit 89 changes from high to low in response to a falling edge of the output signal of the comparator 85, but only after expiration of a delay interval t_DET from the falling edge of the signal output from the comparator 85. However, if the input to the circuit 89 again goes high before expiration of the delay interval t_DET, the circuit 89 resets the count of the delay interval.

[0089] More specifically, the delay circuit 89 detects a falling edge of the output of the comparator 85 at the end of one pulse, but waits before switching to a low output. When a subsequent pulse peak above the I_det threshold is detected via the sensor 73 and comparator 85, the output of the comparator 85 again goes high, and the delay circuit 89 stops its count of the delay interval of t_DET. In this way, the output of the delay circuit 89 remains high so long as pulses with valley or minimum values are received, each having a duration t_low less than the delay interval of t_DET.

[0090] For example, after a disconnection for a period longer than t DET, the delay circuit 89 outputs a high value as long as the output of the comparator 85 remains high, for example during the pre-charge / trickle-charge portion of the current consumption profile, the high constant-current portion of the current consumption profile, and some constant-voltage portions of the current consumption profile. The delay circuit 89 can detect a falling edge of the comparator output signal in response to the disconnection of the chargeable device 11 from the cable 15. And in this case, the output of the delay circuit 89 subsequently goes low upon expiration of the delay interval t DET after the falling edge of the comparator 85 output (indicating a sensed disconnection), and remains low as long as there is no device 11 connected to the cable 15, as indicated by the 0 output of the comparator 85. However, the delay circuit 89 is configured with a delay interval t DET that exceeds the duration t low of each valley of the modulated pulses, at least for the lower amplitude pulses. When the current drawn by the device 11 falls below the I det threshold, for example during the low-current portions of the constant-voltage state and the end-of-charge (EOC) state, the comparator 85 pulses between low and high values periodically due to the pulsed modulation of the current. The comparator 85 will output a high value in response to each peak of the current pulses that equals or exceeds the I det threshold, and will output a low value in response to each valley that is below the threshold. However, the delay interval t DET of the circuit 89 is such that the circuit 89 maintains its high output state as long as a consecutive one of the current pulses is received, and the comparator 85 provides a corresponding low-high transition separated by a low output of duration t low that is less than t DET.

[0091] Figure 12 The reset and recovery functions that can be implemented in conjunction with the current response detection and state indication of Figure 9 to 11 are illustrated in the timing diagrams of FIGS. 6A-6D. Figure 12 relate to a reset during the pre-charge phase of the current consumption profile (as compared to Figure 10 ). Figure 13 relate to a reset during the charge phase when the LED is flashing due to a continuous high current (for example, during the constant-current phase, as compared to Figure 9 ). Figure 14 relate to a reset during the EOC phase when the chargeable device is still connected (as compared to Figure 11 ). In the timing diagrams of FIGS. 6A-6D, the worst case is that the reset occurs just before the pulse occurs (i.e., after t LOW). Figure 14 The reset and recovery functions that can be implemented in conjunction with the current response detection and state indication of Figure 15A to 15C are summarized for various states as illustrated in FIG. 7. Figure 9 to 14 The reset and recovery functions that can be implemented in conjunction with the current response detection and state indication of Figure 7Examples of time intervals implemented by delay elements in example logic circuits of the present disclosure. Aspects of the reset and recovery functions should be readily understood from the drawings.

[0092] It should be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding individual disciplines, except where specifically indicated otherwise. For example, the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items, as is common in the art. The terms "comprises", "comprising", "includes", "including", "contains", "containing" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, includes or contains a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by "comprises a", "includes a", "contains a", or "consists of" does not, without further qualification, preclude the existence of additional such elements in the process, method, article, or apparatus that the element, follows. Nothing in the description of a process, method, article, or apparatus constitutes any admission that any, none, or all the examples require, entail, or benefit from that process, method, article, or apparatus.

[0093] Unless otherwise stated, any and all measurements, values, ratings, positions, magnitudes, sizes and other specifications that are set forth in this specification are approximate, not exact. Such amounts are intended to be, and are, used only to enable the claims to encompass within their scope every useful implementation of the application. For

[0094] While the summary of the inventive subject matter has been presented with reference to specific examples, various modifications and changes in the examples can be made as would be obvious to one skilled in the art having the benefit of this disclosure. It is intended that the examples of this inventive subject matter be limited only by the scope of the attached claims, alone or in combination, and that wherein reference is made to an amount, explicitly or by way of illustration alone, that such is intended to mean ±10% from the stated amount unless otherwise specified.

[0095] The examples herein are well enough described that one of ordinary skill in the art can readily devise methods and structures to create further examples and modifications that are within the scope of the disclosure. Other examples can be utilized and derived therefrom, without departing from the scope of the disclosure, which is to be limited only by the scope of the claims, as encompassed by the language of those claims, and equivalents thereof. Accordingly, the disclosure is not to be restricted based on the detailed description.

Claims

1. A system comprising: a chargeable device comprising: a battery; a battery charger circuit coupled to the battery; and a receiver comprising contact pads coupled to the battery charger circuit and a ground of the chargeable device; a charging cable comprising: a power bus; a ground bus; a cable head having a power pin and a ground pin coupled to the power bus and ground bus, respectively, and configured to engage the contact pads when the cable head is coupled to the receiver of the chargeable device; a current sensor coupled to at least one of the buses to detect current through the pins of the cable head; a status indicator to provide a user-perceptible output; and coupled logic circuitry to operate the status indicator configured to compare the current detected by the current sensor to a first threshold and a second threshold, wherein the first threshold is higher than the second threshold, and in response to a result of the comparison, the logic circuitry is further configured to: when the current detected by the current sensor is below the second threshold, control the status indicator to provide a first type of perceptible output indicating that the cable head is not electrically coupled to the receiver; when the current detected by the current sensor is at or above the first threshold, control the status indicator to provide a second type of perceptible output indicating that the cable head is electrically coupled to the receiver and the current is charging the battery of the chargeable device in a primary charging state; when the current detected by the current sensor is below the first threshold and at or above the second threshold, control the status indicator to provide a third type of perceptible output indicating that the cable head is electrically coupled to the receiver but the current is not charging the battery of the chargeable device or is charging the battery of the chargeable device in a secondary charging state; and implement timing logic relative to current pulses detected by the current sensor to: when the current sensor periodically detects peaks of modulated current pulses at or above the first threshold, operate the status indicator to maintain the second type of perceptible output; and when the current sensor periodically detects peaks of modulated current pulses at or above the second threshold and below the first threshold, operate the status indicator to maintain the third type of perceptible output.

2. The system of claim 1, wherein: the receiver of the chargeable device comprises a cable plug; the contact pads are located on the cable plug; the cable head comprises a socket having a recess configured to receive the cable plug to rotatably couple the socket of the cable head to the receiver of the chargeable device; and when the cable plug is received in the recess of the socket of the cable head, the power pin and ground pin protrude into the recess of the socket of the cable head to contact the contact pads of the cable plug, respectively.

3. The system of claim 1, wherein the chargeable device further comprises: ​ at least one coupled switch to draw current from the battery charger circuit; and a device controller responsive to power received from the charging cable through the contact pads of the receptacle, configured to operate the at least one switch to: pulse modulate current through the contact pads of the receptacle at a first pulse amplitude sufficient to periodically reach or exceed the first threshold when current is below the first threshold and equal to or above the second threshold; and pulse modulate current through the contact pads of the receptacle at a second pulse amplitude sufficient to periodically reach or exceed the second threshold when current is flowing but below the second threshold; wherein the first pulse amplitude is higher than the second pulse amplitude.

4. The system of claim 3, wherein the device controller is further configured to control the battery charger circuit to implement a charging current profile, including: a pre-charge trickle current during a first portion of the profile, below the first threshold and equal to or above the second threshold; a constant current during a second portion of the profile, equal to or above the second threshold; a constant voltage during a third portion of the profile, during which current drops from the constant current to a minimum due to an increase in charge stored on the battery; and a continuous minimum current during a fourth portion of the profile, during which the battery has reached a full charge state.

5. The system of claim 4, wherein the device controller is further configured to operate the at least one switch coupled to the battery charger circuit to: pulse modulate current through the contact pads at the first pulse amplitude only during the pre-charge trickle current of the first portion of the profile; and pulse modulate current through the contact pads at the second pulse amplitude only during the lower current portion of the third portion of the profile or during the fourth portion of the profile.

6. The system of claim 1, wherein the logic circuit of the charging cable is further configured to operate an indicator to: provide a steady off output as the perceivable output of the first type, indicating that the cable head is not electrically coupled to the receptacle; provide a pulsed output as the perceivable output of the second type, indicating that the cable head is electrically coupled to the receptacle and the current is charging the battery of the chargeable device in the primary charging state; and provide a steady on output as the perceivable output of the third type, indicating that the cable head is electrically coupled to the receptacle but the current is not charging the battery of the chargeable device or is charging the battery of the chargeable device in the secondary charging state.

7. A charging cable, comprising: a power bus; a ground bus; ​ a cable head having power and ground pins respectively coupled to the power and ground buses and configured to engage contact pads of a receiver of a chargeable device when the cable head is coupled to the receiver of the chargeable device; a current sensor coupled to at least one of the buses to detect current through the pins; a status indicator to provide a user-perceptible output; and a coupled logic circuit to operate the status indicator configured to compare the current detected by the current sensor to a first threshold and a second threshold, wherein the first threshold is higher than the second threshold, and in response to a result of the comparison, the logic circuit is further configured to: control the status indicator to provide a first type of perceptible output indicating that the cable head is not electrically coupled to the receiver when the current detected by the current sensor is below the second threshold; control the status indicator to provide a second type of perceptible output indicating that the cable head is electrically coupled to the receiver and the current is charging a battery of the chargeable device in a primary charging state when the current detected by the current sensor is equal to or higher than the first threshold; and control the status indicator to provide a third type of perceptible output indicating that the cable head is electrically coupled to the receiver but the current is not charging the battery of the chargeable device or charging the battery of the chargeable device in a secondary charging state when the current detected by the current sensor is below the first threshold and equal to or higher than the second threshold; and implement timing logic relative to a pulse of current detected by the current sensor to: operate the status indicator to maintain the second type of perceptible output when the current sensor periodically detects a peak of a modulated current pulse equal to or higher than the first threshold; and operate the status indicator to maintain the third type of perceptible output when the current sensor periodically detects a peak of a modulated current pulse equal to or higher than the second threshold and lower than the first threshold.

8. The charging cable of claim 7, wherein: the cable head includes a socket having a recess configured to receive a cable plug of the receiver carrying the contact pads to rotatably couple the socket of the cable head to the cable plug of the receiver of the chargeable device; and the power and ground pins protrude into the recess of the socket of the cable head to respectively contact the contact pads of the cable plug when the cable plug is received in the recess of the socket of the cable head.

9. The charging cable of claim 7, wherein the logic circuit is further configured to operate the indicator to: provide a steady off output as the first type of perceptible output indicating that the cable head is not electrically coupled to the receiver; ​ ​ providing a steady-on output as the perceptible output of the second type indicating that the cable head is electrically coupled to the receiver and the current is charging the battery of the chargeable device in the primary charging state; and providing a steady-on output as the perceptible output of the third type indicating that the cable head is electrically coupled to the receiver but the current is not charging the battery of the chargeable device or is charging the battery of the chargeable device in the secondary charging state.

10. A chargeable device comprising: a battery; a battery charger circuit coupled to the battery; a receiver comprising a contact pad coupled to the battery charger circuit and to a ground of the chargeable device; at least one coupled switch to draw current from the battery charger circuit; and a device controller responsive to power from the contact pad of the receiver configured to control the battery charger circuit to implement a charging current profile and to operate the at least one switch to: pulse modulate current through the contact pad of the receiver when current defined by the charging current profile is at or above a cable connection state threshold but below a charging state threshold, the current having a first pulse amplitude sufficient to periodically reach or exceed the charging state threshold; and pulse modulate current through the contact pad of the receiver when current defined by the charging current profile is below a cable connection state threshold, the current having a second pulse amplitude sufficient to periodically reach or exceed the connection state threshold but not the charging state threshold; wherein the first pulse amplitude is higher than the second pulse amplitude.

11. The chargeable device of claim 10, wherein the device controller is further configured to control the battery charger circuit to implement the charging current profile to include: a pre-charge trickle current during a first portion of the profile, at or above the cable connection state threshold and below the charging state threshold; a constant current during a second portion of the profile, at or above the charging state threshold; a constant voltage during a third portion of the profile, during which current drops from the constant current to a minimum due to an increase in charge stored on the battery; and a continuous minimum current during a fourth portion of the profile, during which the battery has reached a fully charged state.

12. The chargeable device of claim 11, wherein the device controller is further configured to operate the at least one switch coupled to the battery charger circuit to: pulse modulate current through the contact pad of the receiver at the first pulse amplitude only during the pre-charge trickle current of the first portion of the profile; and pulse modulate current through the contact pad of the receiver at the second pulse amplitude only during the lower current portion of the third portion of the profile or during the fourth portion of the profile. ​

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