A method for estimating the charge state of a battery in a low-power system, and a system implementing the estimation method.

Abstract

The present invention relates to a method for estimating the charging or discharging state of a battery or cell in a low-power system such as a portable object. [Solution] The system comprises at least one power management circuit (3) connected to a battery or cell (2), and a processing unit (14) of a module (4) connected to the power management circuit (3), wherein when a method for estimating the charging or discharging state of the battery or cell (2) is implemented, at least one battery voltage value is communicated by the power management circuit (3) to the processing unit (14) of the module (4), an algorithm for controlling the charging or discharging state of the battery (2) is executed, and the algorithm is stored in the processing unit (14) to provide the charging or discharging state of the battery or cell (2).

Description

Technical Field

[0001] The present invention relates to a method for estimating the state of charge or discharge of a battery in a low-power consumption system. The low-power consumption system may include a portable object such as an electronic or electromechanical watch or a wristwatch that can be powered by a battery or cell such as a lithium battery.

[0002] The present invention further relates to a system that implements a method for estimating the state of charge or discharge of a battery.

Background Art

[0003] For example, in automotive applications, it has been conventionally known to control the state of charge of a battery in consideration of temperature or other parameters. However, in the automotive industry, since the capacity of the battery is large and the self-consumption of the system for estimating the state of charge (SOC) can be ignored, it is easy to develop applications for estimating the state of charge of the battery.

[0004] In watch applications, the state of charge of a smartwatch is approximated using a look-up table of battery voltages with respect to the state of charge of 100 points multiplied by three different temperatures. This solution is limited in that the memory footprint of the ROM-type memory is large and the accuracy of the method with respect to temperature and absolute accuracy is low. Furthermore, there is no compensation for the electrochemical phenomena of the battery such as relaxation time between charging and discharging. The recharge stage is estimated by a counter. In order to manage the effects of relaxation and hysteresis of the battery due to charge and discharge cycles, a lot of peripheral code needs to be written.

[0005] The most appropriate solution for estimating the state of charge of a battery has been, so far, to use a Coulomb counter, which is a circuit that counts the energy drawn from or collected by the battery. However, in the design of an ultra-low-power wristwatch, this electronic circuit is very expensive in terms of energy and is not compatible with an ultra-low-power consumption system.

[0006] In watchmaking applications, battery power must be limited to the maximum battery voltage (terminal voltage) when fully charged and cannot fall below the minimum battery voltage value (cutoff voltage) to avoid damaging the battery available to power the watch or the watch's electronic circuits. Galvanic or inductive charging may also be used to charge the battery to a certain extent.

[0007] In applications such as timepieces or systems worn by people during sports activities, such as GPS systems, the above-described coulomb counter is often used to estimate the battery charge state. However, this type of counter consumes a considerable amount of power and cannot be used in low-power or low-consumption watches or timepieces. For example, all components of a low-power circuit placed within a watch case must be low-power, and as a result, the battery charge state is controlled so that when the voltage level read from or measured from the battery approaches or equals a lower limit voltage which can be set to equal the battery's cutoff voltage, the power supply from the battery to the electronic circuit is interrupted, and when fully charged, a voltage close to the battery's terminal voltage is generated.

[0008] U.S. Patent No. 10,700,539 describes an electronic device comprising a display and controller that acquires time-series information regarding the battery's output voltage in order to detect the battery's charge state. This patent describes performing mathematical regression to generate a lookup table and importing it into a microcontroller unit. Thus, a drawback is that the lookup table is considered after it enters the microcontroller unit, making it impossible to precisely control the battery's charge state. [Overview of the project]

[0009] Therefore, the present invention proposes a method for estimating the charging or discharging state of a battery or cell, which rapidly provides information for determining the charging or discharging state by mathematical regression performed directly in a processing unit, which may be a microcontroller unit.

[0010] This makes it possible to quickly and perfectly match the operating point of an electronic circuit or module, overcoming the drawbacks of the prior art. The present invention also makes it possible to measure voltage more easily and with greater accuracy, overcoming the drawbacks of the prior art.

[0011] For this purpose, the present invention relates to a method for estimating the charge or discharge state of a battery or cell, which is performed by a low-power charge and discharge control system as described in independent claim 1.

[0012] The specific steps of the estimation method are described in dependent claims 2 to 8.

[0013] For this purpose, the present invention further relates to a charge or discharge control system for implementing a low-power method for estimating the charge or discharge state of a battery or cell as described in independent claim 9.

[0014] Specific implementations of the control system are described in claims 10 to 12.

[0015] One advantage of a low-power method for estimating the charge or discharge state of a battery or cell is that the decision is made directly in a microcontroller unit of a portable object, preferably a clock, which makes it possible to quickly provide the charge or discharge state of the battery or cell.

[0016] Algorithms for controlling the charging or discharging state of batteries or cells in portable objects, particularly watches, are incorporated into a microcontroller unit, preferably an electronic module. This makes it possible to directly control the charging or discharging state of the battery and provide results quickly.

[0017] Advantageously, when the algorithm operates on a microcontroller unit, the Coulomb counter is not used, significantly reducing the current consumed to determine the charge or discharge state of the battery or cell. Under these conditions, the power consumed to determine the charge or discharge state of the battery or cell according to the present invention is very small.

[0018] Furthermore, by directly implementing the mathematical regression of the algorithm in the microcontroller unit, the memory footprint of the microcontroller unit is reduced.

[0019] Another advantage of using the algorithm of the microcontroller unit of the present invention is that it compensates for artifacts related to the battery or cell voltage caused by the temperature of the battery or cell and the switching between charging and discharging (hysteresis and relaxation phenomena). [Brief explanation of the drawing]

[0020] The purpose, advantages, and features of a low-power or low-consumption method for estimating the charge or discharge state of a battery or cell, and a system for implementing such a method, will become apparent in the following non-limiting description, which is given with reference to the drawings. [Figure 1] This invention provides a low-power system for controlling the charge or discharge state of a battery or cell, which implements a method for estimating the charge or discharge state of a battery or cell according to the present invention. [Figure 2] The present invention provides a microcontroller unit for an electronic module such as a wristwatch module, which incorporates an algorithm for controlling the charging or discharging state of a battery or cell in order to control the charging or discharging state of the battery or cell with low power consumption. [Figure 3] This shows the charging curves of a battery or cell in a low-power consumption control system at different temperatures. [Figure 4]Shows the discharge curves of batteries or cells in a low-power consumption control system at different temperatures.

Best Mode for Carrying Out the Invention

[0021] The following description relates to a method for estimating the charging or discharging state of a battery or cell of a portable object such as a low-power wristwatch, and a system for implementing the estimation method so as to accurately control the charging or discharging state of the battery or cell of the wristwatch. Preferably, the wristwatch includes an energy source in the form of a lithium battery. However, other cell types may also be envisioned.

[0022] It should be noted that the present invention refers to a system for controlling or estimating the charging or discharging state of a low-power battery or cell as shown in FIG. 1. The control or estimation system 1 may be a portable object including a module 4 powered by a battery or cell 2 and including a power management circuit 3 and a processing unit 14. When this method is implemented, the power management circuit 3 communicates data and / or parameters including at least the voltage of the battery 2 to the processing unit 14 of the module to execute an algorithm for controlling the charging or discharging state of the cell 2. This algorithm is stored in the processing unit.

[0023] The processing unit may preferably be a microcontroller unit 14, and the portable object may be an electronic or electromechanical wristwatch or clock including a wristwatch module 4 with ultra-low power consumption and including the microcontroller unit 14. This power may be consumed in the operating state of the wristwatch system for a method of estimating the charging or discharging state of the battery or cell 2 of the wristwatch.

[0024] During normal operation of the estimation system 1 for a low-power consumption electronic or electromechanical wristwatch or clock, there may be a current consumption of several μA.

[0025] A method for estimating the charging or discharging state of a battery or cell 2 of a low-power consumption system 1 for a portable object or the like is preferably implemented for a wristwatch or an electronic or electromechanical clock.

[0026] A system 1 for estimating the charging or discharging of a battery or cell 2 of a wristwatch or a clock includes at least a battery or cell 2 connected to a power management integrated circuit 3 called a PMIC. Usually, this integrated circuit 3 can communicate directly with a wristwatch module 4 including a microcontroller unit 14 in which an algorithm for controlling the charging or discharging state of the cell 2 is stored. The communication executed by the power management integrated circuit 3 includes control parameters for executing an algorithm stored in the microcontroller unit 14 of the wristwatch module 4. Regarding the execution of the algorithm in the microcontroller unit 14, it will be described below with reference to FIG. 2 of the method for estimating the charging or discharging state of a battery or cell. The purpose of this algorithm is to quickly provide the user of a portable object with the charging or discharging state of the battery or cell 2.

[0027] The method for estimating the charging or discharging state of a battery or cell 2 can be automatically implemented during a defined period.

[0028] A system 1 for estimating the charging of a battery or cell 2 or further the discharging of a battery or cell may further include a temperature sensor 6 that supplies a temperature value to the power management integrated circuit 3 so as to be transmitted as a parameter to the microcontroller unit 14 of the clock module 4 by a processing algorithm stored in the microcontroller unit 14 to directly and quickly determine the charging or discharging state of the battery or cell. Further, an external energy source 5 can be connected to the system 1 in direct connection with the power management integrated circuit 3. This external energy source 5 may be a galvanic charger or an inductive charger.

[0029] Figure 2 shows a microcontroller unit 14 with all processing elements when an algorithm for controlling the charging or discharging state of a battery or cell is executed. The first functional block 24 takes into account the battery voltage Vbat and the charging or discharging mode. Preferably, this first functional block 24 can further take into account the battery temperature and operating mode (charging or discharging).

[0030] This algorithm preferably implements mathematical regressions performed on actual charge or discharge data of a battery or cell at several temperature levels and several charge or discharge currents. The regression coefficients are then stored in a lookup table and interpolated for the measured temperature.

[0031] The output of the first functional block 24 is provided to the second functional block 34 to manage the DC charging voltage (CV) stage as the initial point for mathematical regression. Charging in DC voltage mode uses the percentage of the battery's charging current Icp relative to the maximum charging current and the state of the DC and DC voltage (CV) stages or modes. If the battery voltage no longer changes in DC voltage (CV) mode and there is still about 15% of the energy to be supplied to the watch, e.g., the state of charge (SOC), the state of charge is estimated by mathematical regression with respect to the charging current.

[0032] A third functional block 44, defined as a charge or discharge state selector, is connected to the outputs of the first functional block 24 and the second functional block 34, and is controlled by the DC current and DC voltage mode states. This block 44 is responsible for switching the SOC value between CV charge mode and other modes by mathematical regression of the SOC from the battery voltage.

[0033] The switch from charging current to discharging current has the effect of generating overvoltage or undervoltage artifacts in the battery voltage that are completely unrelated to the battery's State of Charge (SOC). This is due to electrochemical phenomena (charge diffusion) within the battery. To "eliminate" these artifacts, the SOC value is maintained in its previous state before the transition for a certain period of time defined by the measurement in the fourth functional block 54.

[0034] During battery charge / discharge transitions, the SOC value exhibits small increases or decreases that do not reflect the state of the SOC (charge or discharge). This is why the SOC value is filtered by a sliding average in the fifth functional block 64.

[0035] The proposed algorithm offers the following advantages: - The memory footprint becomes more compact. - Temperature accuracy improves. - Relaxation phenomena are taken into consideration. - The charging stage of the CV DC voltage is taken into consideration. - The code is simulated, speeding up its development and parameter tuning. - The code is generated automatically.

[0036] Figure 3 shows the charging curves at different temperatures. The charging curves show their respective DC-CV transition regions, but these are very different and dependent on the battery temperature.

[0037] Figure 4 shows the discharge curve, which indicates that the voltage drops faster at low temperatures than at high temperatures. In the low-energy region, the battery voltage drops very rapidly.

[0038] It goes without saying that other implementations of a system for estimating the charging or discharging state can be conceived by those skilled in the art without departing from the scope of the present invention as defined by the claims.

Claims

1. A method for estimating the charging or discharging state of a battery or cell (2) of a low-power system (1) such as a portable object, wherein the system comprises at least one power management circuit (3) connected to the battery or cell (2), and a processing unit (14) of a module (4) connected to the power management circuit (3), A method characterized in that, when a method for estimating the charging or discharging state of a battery or cell (2) is implemented, at least one battery voltage value is communicated by the power management circuit (3) to the processing unit (14) of the module (4), an algorithm for controlling the charging or discharging state of the battery or cell (2) is executed, and the algorithm is stored in the processing unit (14) to provide the charging or discharging state of the battery or cell (2).

2. The method according to claim 1, wherein the processing unit (14) of the module (4) is a microcontroller unit (14) of the electronic module (4), and when a method for estimating the charging or discharging state of the battery or cell (2) is implemented, the microcontroller unit (14) is activated by communication of data and / or parameters from the power management integrated circuit (3), and when the microcontroller unit (14) is switched on, an algorithm for controlling the charging or discharging state of the battery or cell is executed to determine the charging state of the battery or cell (2) or the discharging state of the battery or cell (2) as a function of a selected charging mode or a selected discharging mode of the power management integrated circuit.

3. The method according to claim 1, characterized in that the algorithm for controlling the charging or discharging state of the battery or cell (2) is automatically executed over a defined period of time and controlled by a microcontroller unit (14).

4. The method according to claim 1, characterized in that the temperature sensor of the system (1) provides a temperature value to the power management circuit (3) during the operation of the system (1) for communication as a parameter to the processing unit (14), enabling the algorithm for controlling the charging or discharging state of the battery or cell (2) to provide the charging or discharging state of the battery or cell (2) according to the temperature and operating mode of the battery or cell being charged or discharged.

5. The method according to claim 4, wherein a microcontroller unit (14) executes the algorithm for controlling the charging or discharging state of the battery or cell (2), and in a first functional block (24), the algorithm performs mathematical regression on actual charging or discharging data of the battery or cell, and then stores the coefficients of the regression in a lookup table.

6. The method according to claim 5, characterized in that the mathematical regression is performed on actual charge or discharge data of the battery or cell at several temperature levels and at several charge or discharge currents, and the coefficients of the mathematical regression are stored in the lookup table and interpolated with respect to the measured temperature.

7. The method according to claim 5, characterized in that the output of the first functional block (24) is supplied to a second functional block (34) for managing the stages of the DC charging voltage (CV), a third functional block (44) is connected to the output of the first functional block (24) and the output of the second functional block (34) and is controlled by the mode states of the DC current and DC voltage to define a charging or discharging state, and the third functional block (44) switches between the charging mode (CV) and the main mode using mathematical regression of the battery voltage.

8. The method according to claim 7, characterized in that the transition from charging current to discharging current generates an overvoltage or undervoltage artifact with respect to the battery or cell voltage, the previous charge or discharge state prior to the transition is maintained for a fixed time predetermined by a measurement in a fourth functional block (54) following the third functional block (44), and finally, filtering is performed by sliding averaging in a sixth functional block (64) following a fifth functional block (54).

9. A system (1) that implements the method described in claim 1, wherein the system comprises at least one power management circuit (3) connected to a battery or cell (2), and a processing unit (14) of a module (4) connected to the power management circuit (3).

10. The system (1) according to claim 9, characterized in that the processing unit (14) of the module (4) is a microcontroller unit (14) of the clock module (4).

11. The system (1) according to claim 9, characterized by comprising a temperature sensor (6) connected to the power management circuit (3).

12. The system (1) according to claim 9, characterized by comprising an external energy source (5) derived from a galvanic charger or an induction charger.

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