Method for determining a state of charge of an energy store, method for controlling a charging process, and supply circuit for a load

Abstract

The invention provides a method for determining a state of charge of a primary energy store (14), a method for controlling a charging process, and a supply circuit (10) for a load (12). A switching regulator (18) is at least indirectly coupled to the primary energy store (14) and to a secondary energy store (24). The secondary energy store (24) is charged from the primary energy store (14) by means of the activated switching regulator (18) on the basis of at least one predefined charging power. A charging time for which the switching regulator (18) is activated is determined by a control and evaluation device (26). A state of charge of the primary energy store (14) is determined by the control and evaluation device (26) on the basis of an amount of energy ascertained at least by the charging time and the predefined charging power and drawn from the primary energy store (14).

Description

[0001] Method for determining the state of charge of an energy storage device, method for controlling a charging process and supply circuit for a load

[0002] A method for determining the state of charge of a primary energy storage device, a method for controlling a charging process, and a supply circuit for a load are provided.

[0003] Passive energy storage devices are often used to supply power to loads. However, many loads, such as radio modems, exhibit varying operating states that require different power supplies, for example, when increased transmit and / or receive power is needed. This means that a passive energy storage device intended for power supply is exposed to varying load currents. These varying load currents cause the maximum capacity of the passive energy storage device to decrease significantly over its operating time. Consequently, the energy storage device can no longer be charged to its original, specified nominal manufacturing capacity. As a result, sufficient supply voltages for the load can only be provided for shorter periods, thus reducing the operating life of the energy storage device.

[0004] To protect such passive primary energy storage devices, it is known to provide additional energy storage devices that act as buffer elements between the primary energy storage device and the load. These additional energy storage devices provide the supply voltage for the load and absorb load peaks, preventing them from directly affecting the primary energy storage device.

[0005] The additional energy storage devices must be charged by the primary energy storage device to provide the supply voltage for the load. This is achieved using charging circuits with integrated control devices. To trigger charging processes as needed, the state of charge of the primary energy storage device must be known. Current sensors, which measure the output current from the primary energy storage device, are used for this purpose. However, current measurement results in comparatively high electrical losses, thus reducing the operating time of the primary energy storage device. Furthermore, current sensors increase the complexity of the circuit.

[0006] If additional protective measures for the primary energy storage system are omitted, varying output currents from the primary energy storage system can only be mitigated, but not prevented, by secondary energy storage systems. As a result, the operating time of the primary energy storage system remains suboptimal.

[0007] The task to be solved can be seen as providing a method for determining the state of charge of an energy storage device and a corresponding power supply circuit for a load, enabling high precision in state of charge determination while simultaneously extending the operating time of the energy storage device. Furthermore, the task involves providing a method for controlling the charging process of a secondary energy storage device that causes fewer electrical losses compared to existing methods and therefore enables longer operating times.

[0008] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments are specified in the dependent patent claims and the subsequent description, each of which, individually or in (sub-)combination, can represent aspects of the disclosure.

[0009] The problem is solved according to the invention by a method for determining the state of charge of a primary energy storage device. A switching regulator is coupled, at least indirectly, to the primary energy storage device and a secondary energy storage device. The method comprises at least the following steps:

[0010] The secondary energy storage device is charged from the primary energy storage device using the activated switching regulator based on at least a predetermined charging power.

[0011] A charging time, for which the switching regulator is activated, is determined by a control and evaluation device.

[0012] The charge level of the primary energy storage device is determined by the control and evaluation device based on an amount of energy extracted from the primary energy storage device, which is determined at least by the charging time and the specified charging power.

[0013] The method is based on the understanding that a specified charging power for the secondary energy storage device ensures that the charging process is free of power-related fluctuations. This allows the amount of energy drawn from the primary energy storage device to be determined solely based on the charging time, during which the charging process is executed by the switching regulator. This eliminates the need for current sensors that measure the charging current output by the primary energy storage device. Consequently, the electronic circuit underlying the charging process is particularly compact and simple. By avoiding fluctuations in the charging current amplitude using the switching regulator, the amount of energy drawn from the primary energy storage device can be determined with exceptional precision. This allows for a more accurate determination of the remaining energy in the primary energy storage device, and thus its state of charge, than previously possible.

[0014] According to one aspect, the control and evaluation device for determining the state of charge of the primary energy storage device considers a maximum usable capacity of the primary energy storage device at that time. After manufacturing, the maximum usable capacity can essentially correspond to the nominal manufacturing capacity of the primary energy storage device. Subsequently, however, the maximum usable capacity of the primary energy storage device decreases because the internal resistance of the respective energy storage device increases over time.

[0015] The characteristic temporal behavior of the usable maximum capacity of the primary energy storage device can be stored in a data storage device that is part of, or coupled to, the control and evaluation device. Preferably, the control and evaluation device reads the temporal behavior of the usable maximum capacity of the primary energy storage device from the data storage device, thereby enabling a more precise determination of the charge level of the primary energy storage device than previously possible.

[0016] The switching regulator can optionally be configured to charge the secondary energy storage device with at least two different predefined charging powers. This allows the charging process of the secondary energy storage device to be adapted to specific needs. For example, a higher charging power can be used if the secondary energy storage device itself needs to provide higher output power, such as for a load that temporarily draws more power.

[0017] Preferably, the specified charging powers are constant. This simplifies the determination of the primary energy storage system's state of charge. The control and evaluation device then only needs to know the currently selected charging power.

[0018] According to one embodiment, the secondary energy storage device can be charged by means of a charging current output by the switching regulator. The switching regulator is configured, at least, to provide a charging current with a first constant current amplitude. This ensures a first constant charging power, since the output voltage of the primary energy storage device typically varies only slightly, at least during a single charging cycle.

[0019] Preferably, the first constant current amplitude of the charging current output by the switching regulator can be 50 mA or less, more preferably 30 mA or less, more preferably 20 mA or less, more preferably 15 mA or less, more preferably more than 2 mA, more preferably at least 5 mA and at most 10 mA. This means that the method takes into account that the secondary energy storage device is charged by the primary energy storage device with a charging current of a relatively small amplitude. This has a beneficial effect on the maximum usable capacity of the primary energy storage device at any given time.This means that after a comparison period, measured from the date of manufacture, the primary energy storage device will have a usable maximum capacity that differs less from the nominal manufacturing capacity of the primary energy storage device, compared to the case where charging currents with larger amplitudes are drawn from the primary energy storage device by the switching regulator.

[0020] Preferably, the switching regulator is configured to provide a charging current with at least one second constant current amplitude that differs from the first constant current amplitude. Different charging powers can be achieved by using charging currents with different current amplitudes.

[0021] One aspect stipulates that the charging time can be determined by at least one timestamp, which is defined by a change in the charging state of the switching regulator. This means that a change in the charging state of the switching regulator can trigger the setting or output of a timestamp.

[0022] Of course, the charging time can also be defined by more than one timestamp. For example, a first timestamp can be triggered at the start of a charging process and a second timestamp at the end of the charging process.

[0023] However, generally only a single timestamp is necessary to determine the charging time. In one exemplary embodiment, an initial timestamp can be determined by the start of the charging process. When the charging process is completed, the control and evaluation device can wake up from a sleep state, so that the wake-up time can be used by the control and evaluation device to determine the charging time based on a single timestamp. In another embodiment, multiple timestamps can also be triggered when the charging state of the switching controller changes, thus ensuring redundancy.

[0024] Optionally, when determining the primary energy storage system's state of charge, the control and evaluation device takes into account the primary energy storage system's energy consumption during periods when the switching regulator is deactivated. This allows for a more precise determination of the primary energy storage system's state of charge. The term "energy consumption of the primary energy storage system during periods when the switching regulator is deactivated" also includes power amplitudes supplied by the primary energy storage system during these periods to components coupled to it, even though the switching regulator is deactivated. For example, the switching regulator may be supplied with a quiescent current by the primary energy storage system in its deactivated state to ensure basic functionality (standby functionality) of the switching regulator.

[0025] Optionally, the switching regulator is configured to vary the charging voltages for the secondary energy storage device between at least two voltage amplitudes. The control and evaluation device can control the switching converter accordingly. This avoids deactivating the switching regulator. Consequently, the control and evaluation device does not need to consider the switching regulator's turn-on time when determining the charging time. Therefore, the charging time can be determined more precisely in this case, which also allows for a more precise determination of the primary energy storage device's state of charge. The turn-on time describes the period the switching regulator requires to actually output supply signals at an output after receiving a control signal from the control and evaluation device.

[0026] According to a further embodiment, the control and evaluation device is configured to take into account the installation position of the primary and / or secondary energy storage device when determining the state of charge of the respective energy storage device. The installation position of an energy storage device can have a significant influence on the maximum usable capacity of the energy storage device at any given time. For example, the maximum usable capacity can vary by more than 20% depending on the installation position. Therefore, the control and evaluation device can consider information about the installation position of the respective energy storage device, which may, for example, be stored in a data storage device that is part of or coupled to the control and evaluation device. Optionally, the primary and / or the secondary energy storage device can contain lithium thionyl chloride.

[0027] Preferably, the primary and / or secondary energy storage device is a battery or accumulator. The secondary energy storage device is further preferably designed as a supercapacitor. Supercapacitors (also called ultracapacitors) are electrochemical capacitors.

[0028] Compared to batteries of the same weight, supercapacitors have only about 10% of their energy density, but their power density is about ten to one hundred times greater. Supercapacitors can therefore be charged and discharged much faster. They also withstand far more switching cycles than batteries and are therefore suitable as a replacement or supplement when high switching loads are required. Preferably, the supercapacitor is designed as a so-called hybrid capacitor. The hybrid capacitor is preferably designed as a lithium-ion capacitor. Lithium-ion capacitors are supercapacitors with asymmetrical, i.e., differently structured, electrodes. They thus belong to the group of so-called hybrid capacitors.

[0029] According to another aspect, a method for controlling the charging process of a secondary energy storage device is also provided. The secondary energy storage device is charged from the primary energy storage device using a switching regulator controlled by a control and evaluation device. The method comprises the following steps:

[0030] The charge level of the primary energy storage device is determined by the control and evaluation device according to a procedure as previously explained.

[0031] A first voltage amplitude of a supply voltage output by the switching regulator for the secondary energy storage device and / or a second voltage amplitude of a supply voltage provided by the secondary energy storage device to a load is detected or received by the control and evaluation device.

[0032] The method ensures that the charging process of the secondary energy storage device can be influenced as needed by the control and evaluation unit. The detected or received voltage amplitude of the supply voltage output by the respective energy storage device allows inferences to be drawn about the state of charge of that energy storage device, without, however, enabling direct quantitative conclusions about its state of charge. For example, if the state of charge of an energy storage device drops too low, this leads to a reduced output supply voltage. This reduction in the supply voltage can therefore be detected or determined by the control and evaluation unit.By detecting or receiving at least one voltage amplitude of the corresponding supply voltage, the control and evaluation device can determine when a (re)charging process of the secondary energy storage device needs to be initiated or terminated. Based on this information, the switching regulator is controlled by the control and evaluation device as needed, thus ensuring a continuous supply voltage for the load. This extends the operating time of the load compared to previous approaches, while simultaneously discharging the primary energy storage device gently.

[0033] Since the supply voltage for the load is provided by the secondary energy storage device, and since the secondary energy storage device is charged from the primary energy storage device with a predetermined charging power (preferably constant), the primary energy storage device is not exposed to fluctuating output power. In other words, varying load conditions, such as peak loads, are absorbed by the secondary energy storage device compared to the primary energy storage device. This advantageously increases the maximum usable capacity of the primary energy storage device at any given time compared to previous approaches. In other words, the operating time of the primary energy storage device is extended.

[0034] Depending on its functionality, the load can generate different load states that the secondary energy storage system must accommodate. For example, a software update of the load can cause a temporary increase in its current draw. Since the charging process of the secondary energy storage system is based on at least two, and optionally more, different charging power levels, the control and evaluation device can adjust the charging process for such a period by controlling the switching regulator accordingly. This ensures that the charging process is adapted to the specific situation.

[0035] Optionally, the voltage amplitude of a supply voltage output by the switching regulator and / or an energy storage device can be measured by a voltage sensor, which transmits the measured voltage amplitude to the control and evaluation device. In an alternative configuration, the control and evaluation device can also have signal inputs that are directly coupled to the switching regulator and / or a corresponding energy storage device, so that the control and evaluation device can measure the voltage amplitude of the energy storage device's output supply voltage itself.

[0036] Preferably, the voltage amplitude of the supply voltage output by the switching regulator and / or the voltage amplitude of the supply voltage output by the secondary energy storage device is continuously or cyclically measured. While continuous measurement enables particularly precise control of the charging processes of the secondary energy storage device, cyclic measurement leads to reduced electrical losses caused by the voltage measurement itself.

[0037] The continuous or cyclical measurement of the voltage amplitude of a supply voltage output by the switching regulator and / or an energy storage device also advantageously allows the control and evaluation device to determine the voltage amplitude of the supply voltage output by the switching regulator and / or the respective energy storage device with respect to the respective open-circuit voltage and / or for a respective load condition. The primary energy storage device is subject to a load condition as long as the charging process of the secondary energy storage device is activated. The secondary energy storage device is subject to a load condition as long as it provides a load current for the load. This allows the respective energy storage devices to be characterized more precisely by the control and evaluation device at any given time.

[0038] Optionally, recorded values ​​for the open-circuit voltage amplitude and / or for a load state of an energy storage device are stored by the control and evaluation unit in a data memory. The data memory is coupled to the control and evaluation unit or is part of it.

[0039] Preferably, the control and evaluation device compares measured voltage amplitude values ​​of a supply voltage output by the switching regulator and / or an energy storage device with corresponding values ​​stored in the data memory. Based on this comparison, the control and evaluation device can detect a replacement of a respective energy storage device, for example, if the open-circuit voltage and / or the voltage amplitude under load increases by a non-negligible amount compared to a previously measured voltage amplitude value. Particularly preferably, the control and evaluation device can detect a replacement of an energy storage device by the fact that the measured open-circuit voltage and / or the voltage amplitude under load has increased by a value greater than a replacement threshold compared to a previously measured voltage amplitude value.

[0040] Optionally, the control and evaluation device can also detect, based on the measured open-circuit voltage and / or the voltage amplitude under load compared to previously measured voltage amplitude values, that an energy storage device has been replaced with one of a different type. For this purpose, the control and evaluation device can, for example, take into account different type-dependent replacement thresholds. Subsequently, the control and evaluation device considers type-dependent updated values ​​of the maximum usable capacity of the respective energy storage device.

[0041] Optionally, updated values ​​of the maximum usable capacity of an energy storage device at any given time can also be taken into account in the procedure for determining the state of charge of at least the primary energy storage device. This allows for a more precise determination of the state of charge.

[0042] Optionally, the switching regulator can be activated by the control and evaluation device if: o the state of charge of the secondary energy storage falls below a first state of charge threshold, and / or o impending load states of the load coupled at least indirectly to the secondary energy storage are detected or determined that are greater than a load threshold, and / or o the detected or received voltage amplitude of the supply voltage provided by the secondary energy storage for the load falls below a predetermined voltage threshold.

[0043] To detect impending load conditions, the control and evaluation device can be at least indirectly coupled to the load. The load can then transmit relevant information to the control and evaluation device. The previously specified conditions ensure that a power drop at the output of the secondary energy storage device can be reliably prevented, as the control and evaluation device activates the charging process of the secondary energy storage device as needed. This prevents a drop in the voltage supply required by the load and the resulting failure of the functionality it is responsible for. In other words, the operating time of the load can be extended compared to previous approaches.

[0044] Optionally, the switching regulator can be deactivated by the control and evaluation device if: o the specific state of charge of the primary energy storage falls below a second state of charge threshold, and / or o the state of charge of the secondary energy storage exceeds a third state of charge threshold.

[0045] This ensures that the charging process is terminated in time before the charging current output by the primary energy storage device drops below a certain amplitude, which could distort the determination of the primary energy storage device's state of charge if a constant charging power is assumed. Additionally, this prevents the charging process from being terminated uncontrollably. Furthermore, the charging process is terminated in a timely manner if the secondary energy storage device can no longer be charged, which would also lead to an uncontrolled termination of the charging process.

[0046] Preferably, the first, second, and / or third state-of-charge thresholds depend on the characteristics of the respective energy storage device to which they refer. For example, a state-of-charge threshold can be determined by the capacity of an energy storage device. This ensures that the method is tailored to the specific underlying electronic circuit.

[0047] Preferably, the switching regulator is deactivated by reducing the voltage amplitude of the charging voltage output by the switching regulator for the secondary energy storage device relative to a reference voltage value, and / or by reducing the current amplitude output by the switching regulator. Both measures reliably terminate the charging process of the secondary energy storage device from the primary energy storage device.

[0048] In one embodiment, the control and evaluation device can cyclically trigger the charging process of the secondary energy storage device. This means that the charging process is initiated at fixed time intervals. Preferably, the control and evaluation device receives electrical power characteristics from the load, at least indirectly. Alternatively, the electrical power characteristics of the load can also be stored in a data storage device that is coupled to or part of the control and evaluation device.Based on the electrical performance characteristics of the load, the control and evaluation device can then determine, with knowledge of the maximum usable capacity of the secondary energy storage to be considered at any given time, how far the voltage amplitude of the supply voltage output by the secondary energy storage may drop before the charging process of the secondary energy storage must be activated to ensure the voltage supply to the load.

[0049] In one embodiment, the control and evaluation device can estimate the energy consumption of the underlying electronic circuit based on the pause times between charging cycles of the secondary energy storage device. Based on this energy consumption, the control and evaluation device can then determine the state of charge of the secondary energy storage device. In doing so, the control and evaluation device can take into account the maximum usable capacity of the secondary energy storage device at any given time. Consequently, the control and evaluation device can determine whether the supply voltage that the secondary energy storage device outputs to the load could collapse due to an insufficient state of charge of the secondary energy storage device.Taking into account the relevant state-of-charge threshold, the charging process of the secondary energy storage can be activated by the control and evaluation device to prevent the power supply to the load from failing.

[0050] One or more aspects of the procedure for determining the state of charge of the primary energy storage device and one or more aspects of the procedure for controlling a charging process can also be reciprocally aspects of the other procedure.

[0051] According to a further aspect, the invention also relates to a computer program product comprising instructions which, when executed by a processor, cause the processor to execute the previously described method for determining the charge state of a primary energy storage device and / or the method for controlling a charging process, in particular the calculation, comparison, and output steps. The advantages achieved by the methods described herein are also achieved by the computer program product in a corresponding manner.

[0052] According to an additional aspect, the invention also relates to a computer-readable

[0053] Storage medium comprising instructions that, when the computer program product is executed by a processor, cause it to perform the previously described method for determining the charge state of a primary energy storage device and / or the method for controlling a charging process, in particular the calculation, comparison, and output steps. The advantages achieved by the methods described herein are also achieved, correspondingly, by the computer-readable storage medium.

[0054] According to a further aspect, the problem is also solved according to the invention by a supply circuit for a load. The supply circuit comprises at least one primary energy storage device, one secondary energy storage device, a switching regulator at least indirectly coupled to the secondary energy storage device and the primary energy storage device, and a control and evaluation device coupled at least to the switching regulator. The secondary energy storage device is configured to supply the load with a load current.The control and evaluation device is set up to: vary the state of charge of the switching regulator so that, in the activated state, the switching regulator charges the secondary energy storage from the primary energy storage using at least a predetermined charging power; determine a charging time for which the switching regulator is activated; and determine the state of charge of the primary energy storage based at least on the determined charging time and the predetermined charging power.

[0055] The advantages gained through the method for determining the state of charge of the primary energy storage device are similarly achieved through the supply circuit. In particular, the supply circuit is compact and enables precise and efficient determination of the primary energy storage device's state of charge. This allows for a better estimation of how long the primary energy storage device can still be used to charge the secondary energy storage device. Furthermore, the service life of the primary energy storage device can be extended compared to previous approaches due to the predetermined charging power.

[0056] Optionally, the control and evaluation device includes hardware and / or software components. For example, the control and evaluation device may include or be coupled with comparators, digital integrated circuits, microcontrollers, and / or analog-to-digital converters. These components enable energy-efficient signal evaluation. For example, comparators enable energy-efficient signal comparisons. In one embodiment, the control and evaluation device may include or be coupled with a timer. The timer is configured to output a timestamp. In particular, the timer is coupled to the control and evaluation device in such a way that the timer can output timestamps that depend on a change in the state of charge of the switching regulator.

[0057] Optionally, the timer can be set up to output a timestamp only when the switching controller is activated by the control and evaluation device.

[0058] Alternatively, the timer can also be configured to output a timestamp when the switching regulator is deactivated by the control and evaluation device.

[0059] The timestamps output by the timer can be transmitted to or taken into account by the control and evaluation device. This enables a precise determination of the charging time of the activated switching regulator.

[0060] In one embodiment, the timer can be a low-power circuit and / or a microcontroller that has a particularly low energy consumption, in particular an energy consumption that is lower than the energy consumption of the control and evaluation device.

[0061] The control and evaluation device can include at least a counter circuit, a field-programmable gate array (FPGA), a complex programmable logic device (CLPD), a microcontroller and / or a real-time clock (RTC).

[0062] Optionally, the control and evaluation device includes at least one processor.

[0063] The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the examples shown in the drawings. The drawings show:

[0064] - Fig. 1 a simplified schematic representation of a supply circuit according to the invention for a load,

[0065] - Fig. 2 a simplified schematic representation of a method according to the invention for determining a state of charge of the primary energy storage device of the supply circuit, - Fig. 3 a simplified schematic representation of a method according to the invention for controlling a charging process of the secondary energy storage device of the supply circuit, and

[0066] - Fig. 4 shows exemplary schematic signal waveforms of a measured voltage and a control signal.

[0067] All features mentioned below with reference to the exemplary embodiments and / or the accompanying figures can be combined alone or in any subcombination with features of the invention, including features of preferred embodiments.

[0068] Fig. 1 shows a simplified schematic representation of a power supply circuit 10 according to the invention for a load 12. Solid lines represent the possible energy flow within the power supply circuit 10 with respect to the load 12. Dashed lines show the information flow between individual components of the power supply circuit 10 and the load 12.

[0069] The power supply circuit 10 has a primary energy storage device 14. The primary energy storage device 14 can, for example, be a lithium-thionyl chloride battery.

[0070] The primary energy storage device 14 is coupled downstream to optional components 16. These optional components 16 can, for example, include fuses and / or diodes. This ensures a unidirectional energy flow. Furthermore, fuses ensure that the primary energy storage device 14 is not affected by impermissible voltage or current signals.

[0071] The optional components 16 are coupled downstream to a switching regulator 18 such that energy can flow from the primary energy storage device 14 to the switching regulator 18. This means that one input of the switching regulator 18 is coupled to the primary energy storage device 14 via the optional components 16.

[0072] The switching regulator 18 could, for example, be a DC-DC converter.

[0073] The switching regulator 18 is coupled downstream to optional components 20. The optional components 20 may include additional fuses and / or diodes.

[0074] The optional components 20 are coupled downstream to additional optional components 22. The optional components 22 can, for example, include charge protection for the secondary energy storage device 24, which is coupled to the optional components 22.

[0075] The switching regulator 18 is configured to enable current flow from the primary energy storage device 14 to charge the secondary energy storage device 24. Specifically, the switching regulator 18 is configured to provide a supply signal at an output for charging the secondary energy storage device 24, which has a predetermined charging power.

[0076] Optionally, the switching regulator 18 can be configured to provide supply signals with different charging powers at its output.

[0077] In one embodiment, the switching regulator 18 can be configured to provide supply signals at its output with one or more different current amplitudes and / or with one or more different voltage amplitudes.

[0078] The power supply circuit 10 also includes a control and evaluation device 26. The control and evaluation device 26 is arranged such that it receives a supply signal from the optional component 16 and / or from the optional component 22. This ensures that the power supply to the control and evaluation device 26 is independent of the charge state of the switching regulator 18.

[0079] According to this embodiment, the supply circuit 10 includes a microcontroller 28 which is external to the control and evaluation device 26. In general, however, the microcontroller 28 can also be an integral part of the control and evaluation device 26.

[0080] The microcontroller 28 is arranged such that its power supply is ensured by the optional component 22. Because the microcontroller 28 is separate from the control and evaluation device 26, advantages can be achieved with regard to the energy consumption of the power supply circuit 10.

[0081] The load 12 is coupled to the supply circuit 10 in such a way that the energy supply of the load 12 is ensured from the optional component 22 based on the secondary energy storage 24.

[0082] The control and evaluation device 26 optionally receives status information from the optional components 16. The control and evaluation device 26 is configured to receive a measurement voltage 30, which is detected at the output of the switching regulator 18 by means of a voltage sensor. This means that at least the voltage amplitude of the supply signal output by the switching regulator 18 is detected by the voltage sensor and transmitted to the control and evaluation device 26.

[0083] The control and evaluation device 26 is also configured to output a control signal 32 to the switching regulator 18. Based on the control signal 32, the charge state of the switching regulator 18 can be varied by the control and evaluation device 26.

[0084] According to this embodiment, the control and evaluation device 26 also receives a voltage amplitude, which is detected by a further voltage sensor originating from the optional component 20. The voltage amplitude detected here corresponds to the voltage amplitude of the supply voltage output by the secondary energy storage device 24.

[0085] In addition, according to this embodiment, the microcontroller 28 receives status information from the optional components 16, the optional components 22, and the load 12, which is coupled to the power supply circuit 10. For example, the load 12 can transmit to the microcontroller that it will exhibit an increased load state with increased power consumption for a certain period, for example, when a specified software update of the load 12 is to be performed. The microcontroller 28 is also coupled to the control and evaluation device 26, which can use the information received from the microcontroller 28 to control the charge state of the switching regulator 18 as required.

[0086] Since the load 12 is supplied with power from the secondary energy storage device 24, the load 12 is not directly coupled to the primary energy storage device 14. Varying load conditions, which lead to different power consumption by the load 12, therefore do not cause output currents with varying current amplitudes to be drawn from the primary energy storage device 14. Rather, the switching regulator 18 ensures that only output currents with predetermined, preferably constant, current amplitudes are used to charge the secondary energy storage device 24 from the primary energy storage device 14. This allows the switching regulator 18 to draw only very small current amplitudes from the primary energy storage device 14, thereby significantly increasing its service life. Fig.Figure 2 shows a simplified schematic representation of a method according to the invention for determining a state of charge of the primary energy storage device 14 of the supply circuit 10. Optional steps are shown with dashed lines.

[0087] In step S2, the secondary energy storage device 24 is charged from the primary energy storage device 14 by means of the switching regulator 18 according to a predefined charging power. For this purpose, the control and evaluation device 26 outputs the corresponding control signal 32 to the switching regulator 18.

[0088] The switching regulator 18 can, in particular, provide a supply signal for the secondary energy storage device 24, which has a constant first charging power or a constant second charging power. The charging powers can be different. The supply signal can have a constant current amplitude. The current amplitude can, in particular, be relatively small and preferably be 5 mA or more and 10 mA or less.

[0089] Optionally, step S2 can be further developed by step S4, in which the secondary energy storage device 24 is cyclically charged by the switching regulator 18, starting from the primary energy storage device 14. This means that the control and evaluation device 26 triggers and / or terminates a charging process of the switching regulator 18 at predefined, for example, regular, time intervals.

[0090] Following step S2, the procedure includes step S6, in which the control and evaluation device 26 determines the charging time for which the switching regulator 18 is activated. Based on the specified charging power of the switching regulator 18, this determines the amount of energy drawn from the primary energy storage device 14 during the charging process.

[0091] Optionally, step S6 can be further developed by step S8, in which the control and evaluation device 26 takes into account the turn-on time behavior of the switching regulator 18 when determining the charging time. The turn-on time behavior of the switching regulator 18 describes the time interval required for the switching regulator 18 to provide the supply signal for charging the secondary energy storage device 24 at its output after receiving the control signal 32 from the control and evaluation device 26. By considering the turn-on time behavior of the switching regulator 18, the charging time can be determined more precisely. Step S6 can also be further developed by the optional step S10, in which the control and evaluation device 26 considers timestamps defined by a change in the state of charge of the switching regulator 18.A corresponding timer can output a timestamp if the charge level of the switching regulator 18 is varied.

[0092] For example, the charging time for which the switching controller 18 is activated can be determined based on a single timestamp defined by the start of the charging process. When the charging process ends, the control signal 32 is varied accordingly. Based on the varying control signal 32, the control and evaluation device 26 can determine the charging time, knowing the timestamp that describes the start of the charging process.

[0093] Optionally, multiple timestamps can also be output by the timer, provided that the charge level of the switching regulator 18 is varied.

[0094] Following step S6, the procedure includes step S12, in which the control and evaluation device 26 determines the state of charge of the primary energy storage device 14 based on a determined amount of energy drawn from the primary energy storage device 14. For this purpose, the control and evaluation device 26 takes into account the determined charging time from step S6 and the specified charging power of the charging process carried out by means of the activated switching regulator 18.

[0095] Since the specified charging power can be constant, the amount of energy extracted from the primary energy storage 14 can be efficiently determined.

[0096] Optionally, step S12 can be further developed by at least one of the steps S14 to S18.

[0097] According to optional step S14, the control and evaluation device 26 takes into account the maximum usable capacity of the primary energy storage device 14 at any given time. After manufacturing, the primary energy storage device 14 has a nominal production capacity. However, due to an increasing internal resistance over time, the maximum usable capacity decreases. This can be taken into account by the control and evaluation device 26 to determine the state of charge of the primary energy storage device 14 more precisely than before. For this purpose, the control and evaluation device 26 can, for example, read the data storage, which can contain information about the time course of the maximum usable capacity of the primary energy storage device 14. The optional step S14 can be further developed by the optimal step S16, in which the control and evaluation device 26 takes into account the installation position of the primary energy storage device 14.The installation position, in terms of orientation and alignment, can significantly influence the maximum usable capacity of the primary energy storage device 14 at any given time. By taking the installation position into account, the state of charge of the primary energy storage device can be precisely determined. Information about the installation position can also be stored in a data storage device, which is read by the control and evaluation unit 26.

[0098] Step S12 can also be extended by the optional step S18, in which the control and evaluation device 26 takes into account the energy consumption of the primary energy storage device 14 when the switching regulator 18 is deactivated. Even when the switching regulator 18 is deactivated, other components of the power supply circuit 10, such as the control and evaluation device 26 itself, can cause energy consumption that results in limited energy withdrawal from the primary energy storage device 14. By taking the energy consumption into account when the switching regulator 18 is deactivated, the precision of determining the state of charge of the primary energy storage device 14 is further increased.

[0099] To determine the energy consumption with the switching regulator 18 deactivated, the control and evaluation device 26 can, for example, take into account detected voltage amplitudes provided by the optional components 16. In this sense, the optional components 16 can also include voltage sensors.

[0100] Alternatively, the energy consumption of the supply circuit 10 with the switching regulator 18 deactivated can be known in advance and stored in the data memory. In this case, the control and evaluation device 26 only needs to read the corresponding information from the data memory.

[0101] Overall, the state of charge of the primary energy storage device 14 can be determined particularly efficiently, with little effort and with high precision based on the method.

[0102] Naturally, the control and evaluation device 26 can take into account information received from the microcontroller 28 for determining the state of charge of the primary energy storage device 14, for example, information about detected voltage amplitudes. Fig. 3 shows a simplified schematic representation of a method according to the invention for controlling a charging process of the secondary energy storage device 24 of the supply circuit 10. Optional steps are shown with dashed lines.

[0103] In step S12, the charge level of the primary energy storage device 14 is determined by the control and evaluation device 26. For this purpose, the method described with reference to Fig. 2 is used in particular.

[0104] In the subsequent step S20, the control and evaluation device 26 detects or receives at least one voltage amplitude of a supply voltage output by the switching regulator 18 for the secondary energy storage device 24 and / or a voltage amplitude of a supply voltage output by the secondary energy storage device 24 for the load 12. The information about the detected voltage amplitudes can first be supplied to the microcontroller 28, which processes the information about the detected voltage amplitudes and forwards it to the control and evaluation device 26.

[0105] Optionally, voltage amplitudes of supply signals can also be detected in step S20 if the switching regulator 18 is deactivated. For example, the open-circuit voltage of the primary energy storage device 14 can be detected by the optional component 16.

[0106] The procedure may then include the optional step S22, in which at least the recorded values ​​of the voltage amplitudes are stored in a data memory.

[0107] Starting from step S20 or the optional step S22, the procedure then includes step S24, in which the control and evaluation device 26 compares the voltage amplitude values ​​recorded with respect to the supply voltages with stored values ​​of the voltage amplitudes of the corresponding supply voltages. This allows the control and evaluation device 26 to determine how the voltage amplitudes of the corresponding supply voltages develop over time.

[0108] Of course, in the optional steps S22 and S24, the other recorded voltage amplitudes, for example in the case of the deactivated switching regulator 18, can also be stored in a data memory and subsequently compared with corresponding reference values ​​by the control and evaluation device 26.

[0109] The voltage amplitude of the supply voltages should be essentially constant over time. However, increasing internal resistances of the energy storage devices 14, 24 cause the supplied voltages to exhibit voltage amplitudes that decrease over time.

[0110] However, if the control and evaluation device 26 detects a significant variation in the measured voltage amplitude, for example, a relatively large increase, this can be used by the control and evaluation device 26 in the optimal step S26 to identify a replaced energy storage device 14, 24. If a replaced energy storage device 14, 24 is detected by the control and evaluation device 26, this allows the control and evaluation device 26 to take into account a changed maximum usable capacity of the corresponding energy storage device 14, 24 at that time. For example, the updated maximum usable capacity can be taken into account in the procedure for determining the state of charge of the primary energy storage device 14, as described with reference to Fig. 2.

[0111] Following the optional step S26, the procedure includes the optional step S28, in which the control and evaluation device 26 takes into account pause times during which the switching regulator 18 is deactivated and, therefore, the secondary energy storage device 24 is not charged from the primary energy storage device 14. Considering these pause times makes it possible to estimate the energy consumption of the supply circuit 10 and the load 12 coupled to the supply circuit 10. Based on the estimated energy consumption of the entire system, consisting of the supply circuit 10 and the load 12 coupled to it, the control and evaluation device 26 can determine when the switching regulator 18 must be reactivated to prevent the secondary energy storage device 24 from becoming too low.If the charge level of the secondary energy storage device 24 were to drop too drastically, the supply voltage output to the load 12 could collapse, thereby jeopardizing the functionality of the load 12.

[0112] Naturally, the control and evaluation device 26 can take into account information received from the microcontroller 28 within the framework of steps S12 and S20 to S28.

[0113] Starting from the optional step S28, the procedure includes steps S30 and S32.

[0114] In step S30, the switching regulator 18 is activated by the control and evaluation device 26 based on the control signal 32. Specifically, the switching regulator 18 is activated by the control and evaluation device 26 when the state of charge of the secondary energy storage device 24 falls below a first state of charge threshold. The state of charge of the secondary energy storage device 24 can be estimated by the control and evaluation device 26, for example, based on the optional step S28, taking into account the estimated energy consumption of the overall system with regard to the pause times.

[0115] Additionally, the switching regulator 18 is also activated by the control and evaluation device 26 when impending load states of the load 12, which is at least indirectly coupled to the secondary energy storage device 24, are detected or determined and exceed a load threshold. The control and evaluation device 26 can obtain information about impending load states from the microcontroller 28, which is coupled to the load 12 and receives corresponding information from the load 12.

[0116] The switching regulator 18 is also activated by the control and evaluation device 26 when the detected or received voltage amplitude of the supply voltage provided by the secondary energy storage device 24 to the load 12 falls below a predefined voltage threshold. For this purpose, the measured voltage 30 detected by a voltage sensor, which is measured at the output of the optional components 20, can be used, for example. The voltage amplitude of the supply voltage output by the secondary energy storage device 24 decreases when the state of charge of the secondary energy storage device 24 decreases.

[0117] In step S32, the switching regulator 18 is deactivated by the control and evaluation device 26. Specifically, the switching regulator 18 is deactivated if the state of charge of the primary energy storage device 14, determined in step S12, falls below a second state of charge threshold. The state of charge of the primary energy storage device 14 is then too low to reliably charge the secondary energy storage device 24.

[0118] Optionally, the control and evaluation device 26 can in this case issue a notification to an external component or a user interface indicating that the primary energy storage device 14 needs to be replaced.

[0119] Additionally, the switching regulator 18 is also deactivated when the state of charge of the secondary energy storage device 24 exceeds a third state-of-charge threshold. Since the charging power output by the switching regulator 18 is predetermined and, in particular, can be constant, the control and evaluation device 26 can determine, depending on the charging time for which the switching regulator 18 is activated, the amount of energy supplied to the secondary energy storage device 24 during the charging process. Based on the amount of energy supplied, the state of charge of the secondary energy storage device 24 can be estimated, thus enabling the determination of when the third state-of-charge threshold is exceeded. If the secondary energy storage device 24 were to continue charging, the switching regulator 18 would remain activated even though the secondary energy storage device 24 is fully charged.This would be incorrectly interpreted by the control and evaluation device as a charging process in the sense of an amount of energy being drawn from the primary energy storage device 14. This would cause an incorrect determination of the state of charge of the primary energy storage device 14. Therefore, the charging process is deactivated according to step S32 if the state of charge of the secondary energy storage device 24 exceeds a third state-of-charge threshold.

[0120] The procedure can be further developed by the optional step S34, in which the switching regulator 18 is deactivated by the control and evaluation device 26 by reducing the voltage amplitude and / or the current amplitude of a supply signal output by the switching regulator 18. Both measures lead to the termination of the withdrawal of an amount of energy from the primary energy storage device 14.

[0121] Fig. 4 shows exemplary schematic signal waveforms of a measured voltage 30 and the control signal 32.

[0122] According to this embodiment, the control and evaluation device 26 uses a rectangular control signal 32 to vary the charge state of the switching regulator 18. If the control signal 32 has a high amplitude, the switching regulator 18 is activated. Then the secondary energy storage device 24 is charged from the primary energy storage device 14 (T_Charging). For periods in which the control signal 32 has a low amplitude, the switching regulator 18 is deactivated (T_Off), so that the secondary energy storage device 24 is not charged.

[0123] The correct functioning of the switching regulator 18 can be verified by the control and evaluation device 26 using the measured voltage 30, since the measured voltage 30 should exhibit a defined signal profile due to the state of charge of the switching regulator 18. According to this embodiment, the measured voltage 30 has a sawtooth profile.

[0124] The measured voltage 30 is, of course, also used by the control and evaluation device 26 to influence the state of charge of the switching regulator 18 as needed. This prevents the state of charge of the secondary energy storage device 24 from dropping so low that the voltage supply to the load 12 can no longer be guaranteed.

[0125] The method enables a reliable power supply for the load 12. Since the state of charge of the primary energy storage device 14 can be determined more precisely than before, and the power losses of the supply circuit 10 caused by the method are low, the power supply for the load 12 can be maintained for a longer period than before. In other words, the operating time of the load 12 is extended compared to previous approaches with comparable capacities of the energy storage devices 14 and 24.

[0126] Although the disclosure has been presented and described in relation to one or more embodiments, the person skilled in the art will be able to make equivalent changes and modifications after reading and understanding this description and the accompanying drawings.

[0127] Reference symbol

[0128] Power supply circuit

[0129] load

[0130] Primary energy storage

[0131] Optional component

[0132] Switching regulator

[0133] Optional component

[0134] Optional component

[0135] Secondary energy storage

[0136] Control and evaluation device

[0137] microcontroller

[0138] Measuring voltage

[0139] Control signal

Claims

Patent claims 1. Method for determining a state of charge of a primary energy storage device (14), wherein a switching regulator (18) is coupled at least indirectly to the primary energy storage device (14) and a secondary energy storage device (24), and wherein the method comprises at least the following steps: - Charging the secondary energy storage device (24) from the primary energy storage device (14) using the activated switching regulator (18) based on at least a predetermined charging power, - Determining a charging time for which the switching regulator (18) is activated by a control and evaluation device (26), and - Determining the state of charge of the primary energy storage device (14) by the control and evaluation device (26) based on an amount of energy taken from the primary energy storage device (14), which is determined at least by the charging time and the specified charging power.

2. Method according to claim 1, wherein the switching regulator (18) is configured to charge the secondary energy storage device (24) with at least two different predetermined charging powers.

3. Method according to claim 1 or 2, wherein the secondary energy storage device (24) is charged by means of a charging current output by the switching regulator (18), and wherein the switching regulator (18) is at least configured to provide a charging current with a first constant current amplitude.

4. Method according to claim 3, wherein the switching regulator (18) is configured to provide a charging current with at least a second constant current amplitude that differs from the first constant current amplitude.

5. Method according to one of the preceding claims, wherein the charging time is determined by at least one timestamp defined by a change in the charging state of the switching regulator (18).

6. Method for controlling a charging process of a secondary energy storage device (24) from a primary energy storage device (14) using a switching regulator (18) controlled by a control and evaluation device (26), wherein the method comprises the following steps: - Determining the state of charge of the primary energy storage device (14) by the control and evaluation device (26) according to a method according to one of claims 1 to 5, and - Detection or reception of a first voltage amplitude of a supply voltage output by the switching regulator (18) for the secondary energy storage device (24) and / or a second voltage amplitude of a supply voltage provided by the secondary energy storage device (24) for a load (12) by the control and evaluation device (26).

7. The method of claim 6, wherein the method additionally comprises the following steps: - Activation of the switching regulator (18) by the control and evaluation device (26) if: o a charge state of the secondary energy storage device (24) falls below a first charge state threshold, and / or o impending load states of the load (12) coupled at least indirectly to the secondary energy storage device (24) are detected or determined which are greater than a load threshold, and / or o the detected or received voltage amplitude of the supply voltage provided by the secondary energy storage device (24) for the load (12) exceeds a predetermined value. voltage threshold is undershot, and / or - Deactivation of the switching regulator (18) by the control and evaluation device (26) if: o the determined state of charge of the primary energy storage (14) falls below a second state of charge threshold, and / or o the state of charge of the secondary energy storage (24) exceeds a third state of charge threshold.

8. Method according to claim 7, characterized in that the switching regulator (18) is deactivated by reducing the voltage amplitude of a charging voltage output by the switching regulator (18) for the secondary energy storage device (24) compared to a reference voltage value, and / or by reducing the current amplitude output by the switching regulator (18).

9. Supply circuit (10) for a load (12) comprising at least one primary energy storage device (14), one secondary energy storage device (24), one switching regulator (18) coupled at least indirectly to the secondary energy storage device (24) and the primary energy storage device (14), and one control and evaluation device (26) coupled at least to the switching regulator (18), wherein the secondary energy storage device (24) is configured to supply the load (12) with a load current, and wherein the control and evaluation device (26) is configured to: vary the state of charge of the switching regulator (18) so that, in the activated state, the switching regulator (18) charges the secondary energy storage device (24) from the primary energy storage device (14) based on at least a predetermined charging power, and determine a charging time for which the switching regulator (18) is activated.and to determine a state of charge of the primary energy storage device (14) based at least on the determined charging time and the specified charging power.

10. Supply circuit (10) according to claim 9, wherein the switching regulator (18) is configured to charge the secondary energy storage device (24) with at least two different predetermined charging powers.

11. Supply circuit (10) according to claim 9 or 10, wherein the switching regulator (18) is configured to provide a charging current for charging the secondary energy storage device (24) with a first constant current amplitude.

12. Supply circuit (10) according to claim 11, wherein the switching regulator (18) is configured to provide a charging current with at least a second constant current amplitude that differs from the first constant current amplitude.

13. Supply circuit (10) according to one of claims 9 to 12, wherein the control and evaluation device (26) is configured to detect a timestamp defined by a change in the charge state of the switching regulator (18), and wherein the control and evaluation device (26) is configured to take the detected timestamp into account when determining the charging time.

14. Supply circuit (10) according to one of claims 9 to 13, wherein the control and evaluation device (26) is configured to activate the switching regulator (18) if: - the state of charge of the secondary energy storage (24) falls below a first state of charge threshold, and / or - impending load states of a load (12) coupled at least indirectly with the secondary energy storage (24) are detected or determined, which are greater than a load threshold value, and / or - a voltage amplitude of a supply voltage provided by the secondary energy storage device (24) for the load (12) falls below a predetermined voltage threshold.

15. Supply circuit (10) according to one of claims 9 to 14, wherein the control and Evaluation device (26) is set up to deactivate the switching regulator (18) if the determined state of charge of the primary energy storage device (14) falls below a first state of charge threshold.

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