Passthrough battery management system

Abstract

A passthrough battery management system has a plurality of batteries 414, 416, a power input 406, a detector 404 that detects whether input power is regulated or unregulated, a power output 422, and a switch network 408-412, 418-20 for reconfigurably connecting the power input 406, the batteries 414, 416 and the power output 422. Control circuitry 400 is adapted to reconfigure the switch network 408-412, 418-20 either in a direct passthrough configuration for regulated power, or in a sequence of indirect supply configurations for unregulated power. The indirect configurations discharge a subset 414 of batteries 414, 416 while not charging them, while charging a remaining subset 416 that are not being discharged. The subset being discharged changes with each reconfiguration of the switch network in the sequence of indirect supply configurations.

Description

The present invention relates to passthrough battery management systems, for example suitable for a single board computer (SBC) with a low-power microcontroller (MCU), which can take as an input regulated or unregulated power (such as variable voltage from a solar panel). Background Art In a single board computer (SBC) with a low-power microcontroller unit (MCU), it is useful to power the MCU and other components of the SBC with a battery, but also from a regulated power supply. Direct passthrough allows input power to bypass the battery to supply the MCU, and this is suitable for passing regulated power. But sometimes only unregulated power is available, for example from a solar panel directly connected to USB-C (Universal Serial Bus Type-C). It is a problem that direct passthrough of unregulated power can harm the MCU. In a rechargeable SBC having a battery, the battery can be used as a buffer to protect the MCU from unregulated power, but with one battery it has to operate in a charge / discharge passthrough configuration, which is not good for battery health. Alternatively a costly, and lossy, onboard regulator has to be provided to protect the MCU. Summary of invention It is desirable to provide a battery management system that overcomes at least some of the above-identified problems. According to a first aspect of the present invention, there is provided a passthrough battery management system comprising: - a plurality of batteries; - a power input for receiving input power; - a detector operable to detect whether the input power is regulated or unregulated; - a power output; - a switch network for reconfigurably connecting the power input, the batteries and the power output; and - control circuitry adapted to reconfigure the switch network, to: - either, responsive to detection of a regulated input power by the detector, in a direct passthrough configuration, supply the regulated input power from the input to the output, - or responsive to detection of an unregulated input power by the detector, while not supplying the regulated input power from the input to the output by direct passthrough, in a sequence of indirect supply configurations: discharge a subset of the plurality of batteries to supply power to the output, while not charging the subset with the unregulated input power, while charging a remaining subset of the plurality of batteries with the unregulated input power, and while not discharging the remaining subset to the output, wherein the subset being discharged to supply power changes with each reconfiguration of the switch network in the sequence of indirect supply configurations. Preferably, the control circuitry is adapted to reconfigure the switch network to alternate between a first indirect supply configuration and a second indirect supply configuration. Preferably, the plurality of batteries comprises more than two batteries and the control circuitry is adapted to reconfigure the switch network with more than one battery in the subset being discharged to supply power. (Figures 6a-c) Preferably, the plurality of batteries comprises more than two batteries and the control circuitry is adapted to reconfigure the switch network with more than one battery in the remaining subset being charged. (Figures 5a-c) Preferably, the control circuitry is adapted to reconfigure the switch network to rotate between indirect supply configurations. Preferably, the control circuitry is adapted to reconfigure the switch network in the direct passthrough configuration to supply the regulated input power from the input to the output while charging one or more of the plurality of batteries with the regulated input power. Preferably, the control circuitry is adapted to reconfigure the switch network in the direct passthrough configuration to supply the regulated input power from the input to the output while not discharging any of the plurality of batteries to the output. Preferably, the control circuitry is adapted to reconfigure the switch network in the direct passthrough configuration to: charge a first battery of the plurality of batteries by connecting it to the input; prevent the first battery from discharging by disconnecting it from the output; charge a second battery of the plurality of batteries by connecting it to the input; and prevent the second battery from discharging by disconnecting it from the output. Preferably, the control circuitry is adapted to reconfigure the switch network in a first indirect supply configuration to: discharge a first battery of the plurality of batteries by connecting it to the output; prevent the first battery from charging by disconnecting it from the input; charge a second battery of the plurality of batteries by connecting it to the input; and prevent the second battery from discharging by disconnecting it from the output. Preferably, the control circuitry is adapted to reconfigure the switch network in a second indirect supply configuration to: discharge the second battery by connecting it to the output; prevent the second battery from charging by disconnecting it from the input; prevent the first battery from discharging by disconnecting it from the output; and charge the first battery by connecting it to the input. Preferably, the control circuitry is adapted to reconfigure the switch network in a stored power supply configuration, responsive to detection of an unregulated input power by the detector, while not supplying the regulated input power from the input to the output by direct passthrough, to: prevent any of the plurality of batteries from charging by disconnecting them from the input; and discharge at least one of the plurality of batteries by connecting it or them to the output. According to a second aspect of the present invention, there is provided a computer comprising the passthrough battery management system of any preceding claim and a processor configured to receive power supplied by the passthrough battery management system. Brief description of drawings Embodiments of the present invention will now be described, by way of example only, with reference to the drawings, in which: Figure 1 illustrates, in schematic form, a known passthrough battery management system and MCU with direct passthrough of regulated power. Figure 2 illustrates, in schematic form, a known passthrough battery management system and MCU with indirect passthrough of unregulated power using simultaneous charge and discharge of a battery. Figure 3 illustrates, in schematic form, a known passthrough battery management system and MCU with conversion of unregulated power using an onboard regulator. Figures 4a to 4c illustrate, in schematic form, a passthrough battery management system in a single-board computer in accordance with an embodiment of the present invention, with the switch network in (a) a direct passthrough configuration, (b) a first indirect supply configuration and (c) a second indirect supply configuration respectively. Figures 5a to 5c illustrate, in schematic form, a passthrough battery management system in a single-board computer, with the switch network reconfigured in a sequence of three indirect supply configurations with more than one battery being charged, in accordance with an embodiment of the present invention. Figures 6a to 6c illustrate, in schematic form, a passthrough battery management system in a single-board computer, with the switch network reconfigured in a sequence of three indirect supply configurations with more than one battery supplying power, in accordance with an embodiment of the present invention. Figure 7 illustrates, in schematic form, a passthrough battery management system in a single-board computer with two batteries, with the switch network in a stored power supply configuration. Figure 8 illustrates, in schematic form, a passthrough battery management system in a single-board computer with three batteries, with the switch network in a stored power supply configuration. Description of embodiments Embodiments of the present invention can manage both regulated and unregulated input voltages. This allows the MCU to continue to function while the input voltage to the system varies. The system can be charged on a solar panel directly connected to it via USB C, ranging in voltage for example from 0V - 7V output. Each battery may be charged individually, with the batteries not connected together in series or in parallel with the same bus bars. The charging current and voltage can be varied for each individual battery, at the same time as charging other batteries. A suitable battery charger integrated circuit is the TP4056 Standalone Linear Li-Ion Battery Charger with Thermal Regulation from Nanjing Top Power ASIC Corp. All batteries can be charged while the system still runs with a regulated supply, as a direct pass through can still be allowed with all cells charging. With a regulated supply, the charging current and voltage input can be varied for each individual battery that is being charged, separately at the same time. In examples, the charging paths switch depending on regulated / unregulated power. There may be two output switches for each battery, one is blocked immediately as soon as power is inputted (from the USB-C) to prevent power being drawn through the cell and its charger which could destroy the charger and possibly destroy the cell. To prevent unregulated power from disrupting the MCU operation, when one or more battery is selected to power the MCU, the direct passthrough of unregulated power (bypassing the batteries) is blocked. The overall charging current, battery temperature, battery voltage and mains input voltage may be constantly monitored and an algorithm applied for optimal charging and power use performance. In the description and claims, the term battery may apply to a single or a plurality of cells. Individual batteries are individually chargeable. They may be separately packaged or in the same package. Figure 1 illustrates a known passthrough battery management system with direct passthrough of regulated power from a regulated power source 100. In this configuration it charges a single battery 114 from a USB-C (Universal Serial Bus Type-C) input 102 via a closed switch 110. It simultaneously supplies power to the MCU 124 from the USB input 102 via a closed switch 108. Charge / discharge passthrough by the battery 114 is blocked by the open switch 118 at the output of the battery 114. In the drawings of Figure 1 and in subsequent drawings, features labelled with the same numerals correspond to the same features in subsequent drawings. Therefore, a description of a feature in any drawing should also apply to a feature labelled with the same numeral elsewhere. Figure 2 illustrates the known passthrough battery management system of Figure 1, but with indirect passthrough of unregulated power from an unregulated power source 200 using simultaneous charge and discharge of the battery 114. This configuration charges the battery 114 via the closed switch 110 and simultaneously supplies power to the MCU 124 from the battery 114. It is not desirable to have direct passthrough of unregulated power, as it may damage the MCU 124, so a switch 108 is opened to block unregulated direct passthrough. Instead, this solution uses the battery 114 to supply the MCU 124 via closed switch 118. But having just one battery requires simultaneously charging and discharging the battery (charge / discharge passthrough) which is bad for battery health. It is a problem that one battery with an unregulated supply needs charge / discharge passthrough. Figure 3 illustrates a known passthrough battery management system with conversion of unregulated power using an onboard regulator. To avoid the undesirable charge / discharge passthrough described with reference to Figure 2, an onboard regulator 203 is included, which receives the unregulated power from the unregulated power source 200 via the USB input 102 and provides a regulated output to the MCU 124 via the closed switch 108. This configuration charges the battery 114 via the closed switch 110. A switch 118 at the output of the battery 114 is opened to block charge / discharge passthrough. The onboard regulator 203 is inherently lossy, so it provides direct passthrough but with lower power. This is a problem if the unregulated input power is already low power, such as from a solar panel. If the unregulated input drops below a threshold at which the voltage regulator can function, it can interrupt the supply to the MCU 124, which is another problem. Providing an onboard regulator also increases design complexity and component cost, and uses more board space. Figures 4a to 4c illustrate a passthrough battery management system in an SBC, with the switch network in (a) a direct passthrough configuration, (b) a first indirect supply configuration and (c) a second indirect supply configuration respectively. The passthrough battery management system has a plurality of batteries 414, 416, a power input (in this example at a single input node 406) for receiving input power from a USB-C connector 402, and a detector 404 operable to detect whether the input power is regulated or unregulated. A suitable detector is an on-board multimeter equivalent (such as the INA219 Zero-Drift, Bidirectional Current / Power Monitor With l2C Interface from Texas Instruments), which can detect variable (solar) power availability. A power output is also provided (in this example at a single output node 422). A switch network 408-412, 418-20 is provided for reconfigurably connecting the power input node 406, the batteries 414, 416 and the power output node 422. Control circuitry 400 is adapted to reconfigure the switch network 408-412, 418-20. The control circuitry may comprise GPIO (General Purpose Input Output) from a microcontroller, routed to the switches. With respect to Figure 4a, the control circuitry 400 has reconfigured the switch network 408-412, 418-20, responsive to detection of a regulated input power by the detector 404. The regulated input power can for example be voltage regulated at 5V. The switch network 408-412, 418-20 is configured in a direct passthrough configuration, to supply the regulated input power from the input node 406 to the output node 422 via the closed switch 408. This is done while charging one or more of the plurality of batteries (in this example both batteries 414, 416) with the regulated input power. This is also done while not discharging any of the plurality of batteries 414, 416 to the output node 422. The control circuitry 400 has reconfigured the switch network 408-412, 418-20 in the direct passthrough configuration to charge the first battery 414 by connecting it to the input node 406 by closing a switch 410 its input, and to prevent the first battery 414 from discharging by disconnecting it from the output node 422 by opening a switch 418 at its output. The control circuitry has also reconfigured the switch network to charge the second battery 416 by connecting it to the input node 406 by closing a switch 412 at its input, and to prevent the second battery 416 from discharging by disconnecting it from the output node 422 by opening a switch 420 at its output. Thus, charge / discharge passthrough is blocked for both the first battery 414 and the second battery 416, which is beneficial for their health. With respect to Figures 4b and 4c, the control circuitry 400 has reconfigured the switch network 408-412, 418-20, responsive to detection of an unregulated input power by the detector 404 in a sequence of indirect supply configurations. With respect to Figure 4a, the switch network 408-412, 418-20 is configured in a first indirect supply configuration, to discharge the first battery 414 (i.e. a subset of the batteries) to supply power to the output node 422, while not supplying the regulated input power from the input node 406 to the output node 422 by direct passthrough. The power supplied from the battery can be regulated at for example 3.3V or 5V. This supply is done while not charging the first battery 414 with the unregulated input power, and while charging a second battery 416 (i.e. the remaining subset of the batteries) of the plurality of batteries 414, 416 with the unregulated input power. This is also done while not discharging the second battery 416 to the output. The control circuitry 400 has reconfigured the switch network 408-412, 418-20 in the first indirect supply configuration to discharge the first battery 414 by connecting it to the output node 422 by closing the switch 418 at its output, and to prevent the first battery 414 from charging by disconnecting it from the input node 406 by opening the switch 410 at its input. The control circuitry 400 has also reconfigured the switch network 408-412, 418-20 to charge the second battery 416 by connecting it to the input node 406 by closing the switch 412 at its input, and to prevent the second battery 416 from discharging by disconnecting it from the output node 422 by opening the switch 420 at its output. With respect to Figure 4c, the control circuitry has again reconfigured the switch network 408-412, 418-20, still responsive to detection of the unregulated input power by the detector 404. The switch network 408-412, 418-20 is configured in a second indirect supply configuration, to discharge the second battery 416 (i.e. a subset of the batteries) to supply power to the output node 422 while not supplying the regulated input power from the input node 406 to the output node 422 by direct passthrough. This is done while not charging the second battery 416 with the unregulated input power, and while charging the first battery 414 (i.e. the remaining subset of the batteries) with the unregulated input power, and while not discharging the first battery 414 to the output. The control circuitry 400 has reconfigured the switch network 408-412, 418-20 in the second indirect supply configuration to discharge the second battery 416 by connecting it to the output node 422 by closing the switch 420 at its output, and to prevent the second battery 416 from charging by disconnecting it from the input node 406 by opening the switch 412 at its input. The control circuitry 400 has also reconfigured the switch network 408-412, 418-20 to prevent the first battery 414 from discharging by disconnecting it from the output node 422 by opening the switch 418 at its output, and to charge the first battery 414 by connecting it to the input node 406 closing the switch 410 at its input. Thus, charge / discharge passthrough is blocked for both the first battery 414 and the second battery 416, which is beneficial for their health. Corresponding connections and disconnections can be used in the same way when there are more than two batteries, for example for the embodiments as described with reference to Figures 5a to 5c and 6a to 6c below. With reference to Figures 4b and 4c, the subset being discharged to supply power (i.e. the first battery 414 in Figure 4b) changes with each reconfiguration of the switch network in the sequence of indirect supply configurations. It changes to the second battery 416 in Figure 4c, then back to then back to the first battery 414 in Figure 4b, and so on. The control circuitry 400 is thus adapted to reconfigure the switch network 408-412, 418-20 to alternate between the first indirect supply configuration (as described with reference to Figure 4b) and the second indirect supply configuration (as described with reference to Figure 4c), when an unregulated supply is detected. The alternation may be interspersed with direct passthrough as described with respect to Figure 4a, when regulated input power is detected. In an example described below with reference to Figure 7, if both batteries are fully charged then both the battery chargers are switched off. This will then block power flowing from the USB-C to power the MCU and the SBC can run on both batteries until one or either drain to 20% where they can then start to be re-charged. In an example, if one battery is full and the other is out of charge, the charger for the fully charged battery will be switched off and it will begin to discharge to supply to MCU. Power will be blocked from flowing from the USB-C to power the MCU. The other battery will be charged until it reaches 80% charge and / or the other battery drains to for example 20% and then the batteries being charged and supplying the MCU are then switched. In an example, if both batteries run out of charge, the variable voltage (solar panel) will need to provide enough power to charge both the batteries and power the board, for it to then properly re-start the board. This case is useful, for if the board is plugged into regulated 5V USB power from the mains, a quick charge and revival of the board is possible. Having both batteries switched off as default is not desirable. This is because if plugging in to a regulated 5V input could be used to revive the board on delivery to an end user and, when then plugged in, the MCU opens up the battery channels for it to then power the board and revive itself, however if the MCU is then reset and its GPIO port closes, then the product becomes dead again until revival from enough current to supply the MCU. This is not an ideal scenario and so therefore can be avoided. If the board completely runs out of power, then it is able to trickle charge itself back into life. In an example, if there is not enough charge current to recharge either of the batteries, the SBC can put itself into deep sleep mode and drain down the battery very slowly (for example over 1 year from full charge) until sufficient power is available to recharge it. With reference to Figures 5a to 5c and 6a to 6c, the passthrough battery management system may have more than two batteries and the control circuitry 400 is adapted to reconfigure the switch network 408-412, 418-20 in a sequence of configurations with more than one battery in the remaining subset being charged (Figures 5a to 5c) and with more than one battery in the subset being discharged (Figures 6a to 6c). The control circuitry 400 can reconfigure the switch network 408-412, 512, 418-20, 520 to rotate between indirect supply configurations. Figures 5a to 5c illustrate, in schematic form, a passthrough battery management system with three batteries rotating in a sequence of three indirect supply configurations with more than one battery being charged. With reference to Figure 5a, the passthrough battery management system is configured in an indirect supply configuration with a first battery 414 (i.e. a subset of batteries) supplying power to the MCU 424, but with a second battery 416 and a third battery 516 (i.e. the remaining subset of the batteries) being charged. The third battery 516 is charged via a closed switch 512 at its input, while being prevented from discharging by an open switch 520 at its output. With reference to Figure 5b, the passthrough battery management system is configured in another indirect supply configuration of the sequence with a first battery 414 and the third battery 516 (i.e. a remaining subset of batteries) being charged, and the second battery 416 (i.e. a subset of batteries) supplying power to the MCU 424. With reference to Figure 5c, the passthrough battery management system is configured in another indirect supply configuration of the sequence with the first battery 414 and the second battery 416 (i.e. a remaining subset of batteries) being charged, and the third battery 516 (i.e. a subset of batteries) supplying power to the MCU 424. With reference to Figures 5a to 5c, the subset being discharged to supply power (i.e. the first battery 414 in Figure 5a) changes with each reconfiguration of the switch network in the sequence of indirect supply configurations. It changes to the second battery 416 in Figure 5b and to the third battery 516 in Figure 5c, then back to the first battery 414 in Figure 5a, and so on. Figures 6a to 6c illustrate a passthrough battery management system with three batteries rotating in a sequence of three indirect supply configurations with more than one battery being discharged. With reference to Figure 6a, the passthrough battery management system is configured in an indirect supply configuration in the sequence with a first battery 414 and the second battery 416 (i.e. a remaining subset of the batteries) being discharged to supply power to the MCU 424, and with the third battery 516 (i.e. a subset of the batteries) being charged via a closed switch 512 at its input, while being prevented from discharging by an open switch 520 at its output. With reference to Figure 6b, the passthrough battery management system is configured in another indirect supply configuration in the sequence with the first battery 414 (i.e. the remaining subset of the batteries) being charged, and with the second battery 416 and the third battery 516 (i.e. the subset of the batteries) being discharged to supply power to the MCU 424. With reference to Figure 6c, the passthrough battery management system is configured in another indirect supply configuration in the sequence with the first battery 414 and the third battery 516 (i.e. a subset of the batteries) supplying power to the MCU 424, and the second battery 516 (i.e. the remaining subset of the batteries) being charged. The individual indirect supply configurations illustrated in Figures 5a to 6c may be combined in different orders into a long sequence, interspersed with direct passthrough similar to that described with respect to Figure 4a, when regulated input power is detected. In other examples (not illustrated) the control circuitry may reconfigure the switch network in a sequence of indirect supply configurations in which one or more indirect supply configuration has one or more battery floating by neither charging nor discharging (by opening the switches at the input and output of the respective battery). This may occur as long as at least one battery is supplying power to the output node, while unregulated input power is detected by the detector. It may be useful when a battery is fully charged, to prevent it from being overcharged. The unregulated power can then be distributed to charge other batteries that are not yet full. Figure 7 illustrates a passthrough battery management system with two batteries, with the switch network in a stored power supply configuration. This is similar to the system described with reference to Figure 4a except, because the batteries 414, 416 have both been fully charged, both can be disconnected from the input node 406 by opening the switches 410, 412 at their inputs to prevent charging, while one or more (in this example both) supply power by discharging to the output node 422 via closed switches 418, 420 at their outputs. Figure 8 illustrates a passthrough battery management system with three batteries, with the switch network in a stored power supply configuration. This is similar to the system described with reference to Figure 5a except, because all three batteries 414, 416, 516 have been fully charged, they all can be disconnected from the input node 406 by opening the switches 410, 412, 512 at their inputs to prevent charging, while they all supply power by discharging to the output node 422 by discharging via closed switches 418, 420, 520 at their outputs. In other examples (not shown), one or more (but not all) batteries supply power to the MCU, while the remainder are 5 floating, being disconnected from both the input node and output node, to store charge before being switched into use later.

Claims

1. A passthrough battery management system comprising:- a plurality of batteries;- a power input for receiving input power;- a detector operable to detect whether the input power is regulated or unregulated;- a power output;- a switch network for reconfigurably connecting the power input, the batteries and the power output; and- control circuitry adapted to reconfigure the switch network, to:- either, responsive to detection of a regulated input power by the detector, in a direct passthrough configuration, supply the regulated input power from the input to the output,- or responsive to detection of an unregulated input power by the detector, while not supplying the regulated input power from the input to the output by direct passthrough, in a sequence of indirect supply configurations:discharge a subset of the plurality of batteries to supply power to the output,while not charging the subset with the unregulated input power, while charging a remaining subset of the plurality of batteries with the unregulated input power, andwhile not discharging the remaining subset to the output, wherein the subset being discharged to supply power changes with each reconfiguration of the switch network in the sequence of indirect supply configurations.

2. The passthrough battery management system of claim 1, wherein the control circuitry is adapted to reconfigure the switch network to alternate between a first indirect supply configuration and a second indirect supply configuration.

3. The passthrough battery management system of claim 1 or claim 2, wherein the plurality of batteries comprises more than two batteries and the control circuitry is adapted to reconfigure the switch network with more than one battery in the subset being discharged to supply power. (Figures 6a-c)4. The passthrough battery management system of any preceding claim, wherein the plurality of batteries comprises more than two batteries and the control circuitry is adapted to reconfigure the switch network with more than one battery in the remaining subset being charged. (Figures 5a-c)5. The passthrough battery management system of claim 3 or claim 4, wherein the control circuitry is adapted to reconfigure the switch network to rotate between indirect supply configurations.

6. The passthrough battery management system of any preceding claim, wherein the control circuitry is adapted to reconfigure the switch network in the direct passthrough configuration to supply the regulated input power from the input to the output while charging one or more of the plurality of batteries with the regulated input power.

7. The passthrough battery management system of any preceding claim, wherein the control circuitry is adapted to reconfigure the switch network in the direct passthrough configuration to supply the regulated input power from the input to the output while not discharging any of the plurality of batteries to the output.

8. The passthrough battery management system of any preceding claim, wherein the control circuitry is adapted to reconfigure the switch network in the direct passthrough configuration to:charge a first battery of the plurality of batteries by connecting it to the input; prevent the first battery from discharging by disconnecting it from the output; charge a second battery of the plurality of batteries by connecting it to the input; andprevent the second battery from discharging by disconnecting it from the output.

9. The passthrough battery management system of any preceding claim, wherein the control circuitry is adapted to reconfigure the switch network in a first indirect supply configuration to:discharge a first battery of the plurality of batteries by connecting it to the output;prevent the first battery from charging by disconnecting it from the input;charge a second battery of the plurality of batteries by connecting it to the input; andprevent the second battery from discharging by disconnecting it from the output.

10. The passthrough battery management system claim 9, wherein the control circuitry is adapted to reconfigure the switch network in a second indirect supply configuration to:discharge the second battery by connecting it to the output;prevent the second battery from charging by disconnecting it from the input; prevent the first battery from discharging by disconnecting it from the output; andcharge the first battery by connecting it to the input.

11. The passthrough battery management system of any preceding claim, wherein the control circuitry is adapted to reconfigure the switch network in a stored power supply configuration, responsive to detection of an unregulated input power by the detector, while not supplying the regulated input power from the input to the output by direct passthrough, to:prevent any of the plurality of batteries from charging by disconnecting them from the input; anddischarge at least one of the plurality of batteries by connecting it or them to the output.

12. A computer comprising the passthrough battery management system of any preceding claim and a processor configured to receive power supplied by the passthrough battery management system.

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