Human blood glucose value is likely to lead to serious health threats, so monitoring blood glucose levels is the weight. At present, there are 150 million people in the world with diabetes, so the needs of personal portable blood glucose monitoring instruments (BGM) are huge.
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Figure 1 shows the dynamic blood glucose monitors (CGM) to help diabetic patients check the blood glucose reading in real time, or can monitor blood sugar values during the long period of time. The CGM can continuously monitor the level of blood sugar and then prompt users when the user's blood glucose value is reached a dangerous value. This monitor typically contains the sensor unit shown in FIG. 2 and the aggregator unit shown in FIG.
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Figure 1: Dynamic Blood Sugar Monitor (CGM)
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This sensor unit uses a button battery or a coin battery to connect to the human body (eg, 8 to 10 days) within a certain period of time. The polymer unit is a handheld unit that is powered by a battery, and blood sugar data can be read using radio frequency (RF) techniques such as near field communication. The battery management subsystem of the aggregator unit is composed of a battery charger, a battery electrometric meter, and a protector. 3.7 V Lithium ion cells can run a general aggregator unit. It can be charged by the USB or DC input of the power adapter.
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Figure 2: CGM sensor unit
Figure 3: Schematic block diagram of CGM aggregator unit
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Battery power meter can predict and estimate the remaining capacity, charge state, power exhalation time and operation of the battery in different load states, thereby helping to solve the problem in battery management. With smart battery power meters, users can extend the runtime (as shown in Figure 4) and battery cycle life. The IMPEDANCE TRACKTM measurement algorithm of Texas Instruments (TI) achieves battery capacity prediction of 99% accuracy, making it excellent simulated measurement performance and battery characteristic modeling.
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Figure 4: Using TI power meter to achieve long run time
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This blood glucose monitors offer a variety of single-section battery measurement options, not only small shape, economical, and low power consumption. The electric quantometer can be mounted on a battery pack or on the system PCB, which is more common in portable medical applications.
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Figures 5 and 6 show a typical system side and group-side electricity meter configuration, respectively. The power meter on the system PCB, such as BQ27426, only the lowest user configuration is required, and the current consumption is also small when working properly. For higher levels of integration, some power meters have an integrated detection resistor such as BQ27421-G1.
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On the other hand, if the power meter is mounted in the battery pack, a solution with high-level determination can be provided by a flash-based firmware and a 256-bit integrated security hash algorithm (such as BQ27Z561-R1). BQ2970 and other protective integrated circuits provide voltage, current, and reverse charger protection.
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Figure 5: Typical host / system side electricity meter configuration
Figure 6: Typical battery pack side charge meter configuration
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Battery power meter increases the advanced nature and intelligence level of power management. The system that does not have an accurate electric meter can only be turned off at a fixed voltage. Many devices are turned off, the system voltage is 3.5 V in order to protect the spare capacity for the worst case (reserved electrical energy to shut down), but as shown in FIG. 4, the battery voltage is measured by the microcontroller and analog to digital converter, thereby Generating low battery power warning is not a reliable method of measuring the remaining power. This is because most applications have variable loads. Battery power meter calculates the remaining electricity and changing the shutdown voltage to meet the backup capacity requirements required under any conditions, thereby increasing the operating time.
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In addition to the advantages of the spare capacity, some battery power meters can not be reported to the 0% charge state due to the application generated, so that the battery voltage is below the terminal voltage. This feature is very advantageous when the battery is still high, but the high transient load can cause the termination voltage in advance.
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Battery is a complex electrochemical system, affected by battery aging, temperature and impedance. Algorithms, compact equipment and advanced equipment integration are key features of improved system performance. What is the biggest challenge in the medical battery power supply application such as a dynamic blood glucose monitor? Please tell us your point of view at the end of the article.
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