The technical field generally relates to a power management method for electro-chemical batteries in low capacity state.
Even with all the advances of nowadays portable Information and Communications Technology (ICT) devices, such as, smart phone, tablet computer, system crash due to sudden power cut-off when the battery capacity is low is not uncommon. The main reason for such power cut-off can be explained as follows: the “polarization loss” and associated “impedance” of a Li-ion battery will become very high when the State of Charge (SoC) runs low. The same power fluctuations/surges resulted from running different programs and functions in an ICT device will cause bigger voltage fluctuations at low battery SoC stage. Battery low voltage protection will be activated to cut off the power when a voltage fluctuation reaches the lower voltage threshold. Such low SoC voltage fluctuation will be even bigger for an aged battery due to its impedance increase, and also results in the reduction of precaution lead time for an ICT system to make properly data save and system turn-off. Most of existing power management methods are based on electric/electronics considerations, while battery characteristic curve (BCC) is based on the electrochemical characteristics of a battery shown in
A known problem of the contemporary batteries for electronic devices in low capacity state is that a power surge may occur during the operation to cause the system to shutdown before using up the remaining power in the batteries in low capacity state. The current power management technique it to restrict the user from using functions that consumes a large amount of power in order to prolong the use time of the electronic device when the battery is low. However, the imposed restriction in the power manage technique may cause great inconvenience because the user often intends to use functions that consume more power, such as, making phone calls, sending e-mail with attachments, and so on. At the point of peak power consumption, a battery in low capacity state may reaches the threshold defined for the minimum safe voltage, which will force the battery protection circuit to cut off the battery circuit and shutdown the system without warning when no other effective management is adopted. The observation shows that the peak power consumption often occurs when a function is started for execution, and therefore, the starting of execution of an important function often leads to a premature power shutdown when the peak power consumption exceeds the safety threshold. As a result, the remaining battery capacity is not appropriately utilized even when the remaining power may be sufficient to keep the system operating some important functions for a little longer.
A method detecting the threshold when the polarization loss starts to significantly increase is provided. Such a method is also adaptive to battery aging.
The present disclosure may provide a power management method for electro-chemical batteries in low capacity state. The power management method is based on the BCC which reflects the border line before significant increase of battery polarization at low capacity state. The power management method also provides adaptive means as the battery ages, and is applicable to any devices driven by battery, such as, electrical cars, 3C devices, and so on. By controlling the power consumption of each function component in the device, the power management method might terminate some function threads and start (or keep) some function threads.
One exemplary embodiment relates to a power management method for electro-chemical batteries in low capacity state, comprising: obtaining battery information based on device hardware, to know in advance the maximum allowable current and maximum allowable power when the battery power is low; by detecting the changes in the voltage versus current, updating BCC curve; using BCC curve as power budget to control the ON/OFF of device function thread; and determining whether the minimum battery capacity and the control restriction are reached, and when the minimum battery capacity and the control restriction are reached, turn off the battery through normal shutdown process; otherwise, return to the step of obtaining battery information.
According to another one of the embodiments of the present disclosure, there is provided a non-transitory computer readable recording medium for storing one or more programs, the one or more programs causing a processing unit to perform the methods described herein.
According to another one of the embodiments of the present disclosure, there is provided an apparatus for power management, comprising a processing unit, and memory. The processing unit is configured to perform the steps described in the above embodiments.
According to another one of the embodiments of the present disclosure, there is provided a chip for power management, comprising one or more integrated circuits, the one or more integrated circuits being configured to process the function described in the above embodiments.
With the aforementioned power management method, the disclosed exemplary embodiments may use the BCC for dynamic current/power budget to more precisely control the electronic device power consumption; automatically detect and update BCC; and use a novel algorithm to modulate the total discharge current, where three types of power (peak power, occasional surge power, offset power) are defined and used as the basis for this algorithm. This algorithm is tolerant to the maximum power peaks which are often the calculation basis adopted by other power management algorithm.
Below, exemplary embodiments will be described in detail with reference to accompanying drawings so as to be easily realized by a person having ordinary knowledge in the art. The inventive concept may be embodied in various forms without being limited to the exemplary embodiments set forth herein. Descriptions of well-known parts are omitted for clarity, and like reference numerals refer to like elements throughout.
It should be noted that, in step 302, the updating of the BCC curve is executed regardless of the battery condition, in other words, aged battery, or replacing aged battery with new battery, and so on. Also, three types of power related index are defined for the power consumption of each function component, i.e., execution function thread, in the device so that the device can control the hardware to execute the important function thread based on the maximum allowable current and maximum allowable power. As a result, the power management method allows the device to execute more function threads than the device not using the power management method of the disclosure.
The power management method for electro-chemical batteries in low capacity state is based on the electro-chemical characteristics of the battery and electro-power distribution. As shown in
The BCC curve in the present power management method may be considered as an extension of the technique disclosed in U.S. Publication No. 2012/0133331, wherein the BCC curve is expressed in a voltage versus discharge capacity domain (V-Ah) originally. In the present disclosure, the BCC curve is extended to a current versus discharge capacity domain (I-Ah) and a power versus discharge capacity domain (P-Ah), which are easier to use by power management electronics. In other words, in the present disclosure, the BCC curve is expressed in a V-Ah domain, an I-Ah domain and a P-Ah domain. Through the I-Ah BCC or P-Ah BCC, the device can know in advance the maximum allowable current and maximum allowable power, both are state of charge (SoC) quantitative related. In comparison, the known technique is to fix the maximum allowable current/power at a selected value, or to decrease the current according to the battery operating temperature, while the present disclosure utilizes an equation to define the changes or decrease the current according to the battery operating temperature. The present disclosure uses an equation to define the changes of current/power with respect to SoC of the battery to obtain corresponding quantities for reference by the system and used in battery discharging control. During the battery discharging process so that, the device can automatically search and update the BCC curve. As a result, the power method management can avoid inappropriate shutdown of the system caused by power consumption surge and execute more function threads.
The following describes the theory behind the step of knowing the maximum allowable current and maximum allowable power in advance.
Different batteries show different discharging characteristics.
In V-Ah domain as shown in
V=f(Ah)=aV*Ah+bV
In I-Ah domain as shown in
I=f(Ah)=aI*Ah+bI
In P-Ah domain as shown in
P=f(Ah)=aP*Ah+bP
Therefore, the current and power of the battery under a specific capacity and specific voltage can be obtained through the above equations.
In step 302, the device will automatically search and update the BCC curve. The key to the automatic BCC curve updating is to search the corresponding knee points on the V-Ah curve, I-Ah curve and P-Ah curve. The general guideline for searching for the knee point is to find the point where the impedance, defined as ΔV/ΔI, abruptly increases relatively as the battery discharging capacity increases. The phenomenon can be observed through periodic checking of ΔV/ΔI.
The following uses an exemplary embodiment to describe the finding of the knee point. By reading the relative change ratio of the V and I on the V-I-Ah model, the two ends (i.e., maximum current and minimum current) of the BCC curve can be obtained when reaching limits. The results are reported to the device for effective use of battery capacity.
Then, a constant current discharging experiment, as suggested by U.S. Publication No. 2012/0133331, can be used to establish the relation between the voltage and capacity at different discharging rate, as shown in
The next is to automatically search for the boundary of non-linear region of the battery discharging process (the turning location of V-Ah in
Then, with the multiple of the selected ΔV/ΔI, the I-Ah BCC curve and P-Ah BCC curve can be configured, wherein the following parameters a and b can be obtained by the two turning locations of BCC curve. For example, in
Allowed minimum voltage=aV×discharge capacity+bV (described in U.S. Publication No.US2012/0133331)
Current budget=fI(discharge capacity)=aI×discharge capacity+bI
Power budget=fP(discharge capacity)=aP×discharge capacity+bP
Then, configure the relation between the allowed discharging current and discharging capacity to obtain
current budget=fI(discharge capacity)
An alternative is to connect the two corresponding values of two different currents with a straight line:
power budget=fP(discharge capacity)
Finally, through the battery discharging process (which can be non-constant power discharging) reaching the knee points, using
It should be noted that in step 1002, the battery information includes voltage (V), current (I), discharge capacity, temperature, or the count of discharging process “i”, etc. In step 1003, the middle capacity region can be selected, for example, as 50%±30%, and the corresponding ΔV/ΔI is recorded. Observing ΔV/ΔI during discharging and a multiple comparison is made with the ΔV/ΔI selected in step 1003. When the comparison exceeds a threshold, for example, 10%, a knee—i is determined to be found in the i-th discharging process. In step 1006, the new BCC curve is established by connecting the new knee point with previous knee point knee—i-1 or even more previous knee points. In step 1007, a set of parameters, such as, voltage, current, power, discharge capacity, temperature, can be found from kneei, and compared with the parameters from the knee point kneei-1 of previous (i-1)th discharging process to form linear equations on the V-Ah, I-Ah and P-Ah planes. The lower bound of the voltage, upper bound of the current and upper bound of the power can be obtained from the equations.
Referring to
With the power consumption load pattern for each function thread in the device as in
An experiment shows that the power management method allows the device to activate more execution function threads, as following: when the battery discharges along BCC curve, the battery voltage is adjusted to a higher level as the battery capacity is lowered, while the current is decreased as the battery capacity is lowered. Inferably, a battery operated in such a manner has the advantage of the ability to tolerate the occurrence of peak power, especially when the battery is near the low capacity, whose concentration polarization causes the impedance to increase. Compared to the middle capacity region, a tiny current fluctuation will cause a large response in voltage. In other words, the ΔV/ΔI will increase rapidly. The manner of increasing battery operating voltage (and lowering current) in low battery capacity provides the advantage that—occasional surge power is considered when deciding whether a function thread can be started, as opposed to the known technique to consider maximum peak power when deciding whether to start a function thread. As a result, the present disclosure is more robust for the system stability in comparison with the known technique.
5 W
1 W
To turn on function thread 3 again, the device goes through the above process again. However, function thread 3 cannot be started because of insufficient power budget. The final result will be function thread 1 and function thread 2 running.
In comparison, in the known power management methods that only consider maximum peak power, when the system power remains 2.5 W left, Function thread 1 cannot be started by closing Function thread 2 and 3 to create maximum 1 W+0.8 W extra power allocation.
Furthermore, the CPU operating frequency can also adjusted based on BCC power budget. As shown in
Because BCC-control power budget modulation is a soft-limit, deviation from the curve will not cause the BMS module to cut off the battery power abruptly.
The exemplary embodiments have following features: (1) when the battery is in low capacity state and unable to provide sufficient output power, the method allows the device to compute the maximum allowable power consumption, and using the priority, peak power, occasional surge power and offset power of the function threads, to determine whether a new function thread can be started or running function threads should be terminated; (2) the maximum allowable output estimated by the present method could quantify the maximum allowable power consumption by the battery in low capacity state, and the device could utilize the remaining power in the battery through controlling the function thread execution; and (3) applicable to any devices driven by batteries.
According to another one of the embodiments of the present disclosure, there is provided a non-transitory computer readable recording medium for storing one or more programs, the one or more programs causing a processing unit to perform the methods described herein.
According to another one of the embodiments of the present disclosure, there is provided an apparatus for power management, comprising a processing unit, and memory. The processing unit is configured to perform the steps described in the above embodiments.
According to another one of the embodiments of the present disclosure, there is provided a chip for power management, comprising one or more integrated circuits, the one or more integrated circuits being configured to process the function described in the above embodiments.
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
Number | Date | Country | Kind |
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99140824 | Nov 2010 | TW | national |
This is a continuation-in-part (CIP) application of U.S. application Ser. No. 13/081,514, filed Apr. 7, 2011. The U.S. application Ser. No. 13/081,514 now is U.S. Publication No. 2012/0133331, which also claims the benefit of Taiwan Application Serial No. 99140824, filed Nov. 25, 2010. The CIP application is based on, and claims priorities from, U.S. application Ser. No. 13/081,514 and Taiwan Application Serial No. 99140824, the disclosure of which is incorporated by reference herein in its entirety. The CIP application is also based on, and claims priority from, U.S. Provisional Application No. 61/909,228 filed on Nov. 26, 2013, the disclosure of which is hereby incorporated by reference herein in its entirety.
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Child | 14174472 | US |