Most electronic device designers are using or considering rechargeable batteries. Cars, cellphones, laptops, media players, and even airplanes are increasingly reliant on lithium chemistry. As we’ve seen in some famous examples, if they are not engineered properly, thermal runaway in these batteries can make them very dangerous. That’s a product performance problem you really don’t need!
Several design factors have been attributed to thermal runaway, but some result from counterfeit batteries and chargers that don’t include the requisite safety features. The engineers at Texas Instruments (TI) have looked into these causes to develop a battery platform and portable power management system to help prevent the batteries in your designs from catching fire.
Temperature Monitoring of Rechargeable Batteries
Many things can increase the chances that a battery will overheat. Some notable causes of overheating are: improper ventilation (like charging under a pillow), using the device while charging (or in extreme conditions), and using counterfeit batteries. Thankfully, a simple thermistor can help detect when the battery is over-heating.
When a battery is being charged, a certain amount of voltage and current is being applied to the battery. Too much current or too much voltage can create a very hot battery. Many battery management systems will monitor only current or voltage, but TI’s bq24060 and bq24070 will monitor them both to ensure safe charging. This video shows that once the temperature reaches a safety margin, the power to the battery is shut off.
However, temperature monitoring is the last line of defense to ensure product and user safety. Designers must also ensure that authentic batteries are used and the charging is properly managed.
Authentication & Identification of Replacement Batteries
Not all consumers will listen to the warnings to use your custom made batteries and chargers. Unfortunately, counterfeit batteries that aren’t specifically designed for a device may not supply the correct voltage and current levels while charging.
To prevent counterfeit battery use, TI has a portfolio of authentication devices that range from the basic to very complex. If the battery doesn’t pass authentication, then the device will either not start or it will send an error message during start-up.
The simplest of schemes use Identification-Based Authentication. It works somewhat like wireless authentication and identification. A host (phone) sends a constant signal to the responder (battery) and a constant reply is sent back. The host can then read the data and verify that the battery was made for the product. The bad news with this scheme is that the codes can be duplicated by counterfeiters, often within just weeks of production.
For added security, a challenge and response-based authentication scheme can help to confound the counterfeiters. This scheme changes the challenge and response each time the battery is inserted. The security is in a secret key that is shared between the device and the battery. When the battery is plugged in, the phone sends a set of numbers that are fed into the key. If the returned value matches the value calculated by the host, the device is powered up.
The challenge and response-based scheme also employs public authentication. Public authentication platforms are effective because they can more thoroughly evaluate against attacks seeking to uncover the secret key.
For even more security, the SHA-1/HMAC-based (Secure Hash Algorithm-1/Hash Message Authentication Code) can be implemented. This method has been used for several years to secure internet transactions. It works similarly to the Challenge and Response scheme using a secret key. However, this method uses a 160-bit challenge. This creates 2160 or 1.46 x 1048 possibilities, which greatly increases security. If you want to use this method, then TI’s bq26100 IC is right for your design.
Charging Management
As a safety feature, typical chargers place the battery and the system in parallel with each other. In this configuration, if a user is charging their battery while using the phone, less current is available to charge the battery. In some designs, if the system current is greater than the battery current, then the battery will actually start discharging. That’s why turning off GPS and Wi-Fi systems will charge your phone faster.
Other configurations manage battery charging differently. For example, the current flow Power Path Management (PPM) system uses a pair of transistors to control how much power is on the power bus and the amount of current that is applied to the battery. This ensures a regulated amount of voltage and current are applied to the battery during the charging cycle.
Additionally, a Dynamic PPM (DPPM) will maximize the available power from the adapter by monitoring the power bus for input fluctuations. In this set up, if the battery and system current becomes greater than the current being supplied, then adjustments are made so that both receive a proper amount of current equal to what is available. Additionally, this configuration will allow your design to use a smaller power rating and a less expensive AC adapter. This DPPM set up is used in TI’s bq24070 IC.
Fuel Gauging
Has your battery gauge ever told you that you have 20 minutes of charge remaining, only to shut down 2 seconds later? Fuel gauging isn’t just for user satisfaction. It’s also important in measuring the proper battery charge.
Most devices employ either a voltage-based or the coulomb counting-based algorithm to determine the charge of your device’s battery. However, both of these algorithms have their limitations.
TI’s patented Impedance Track™ technology, however, uses both algorithms to help measure the charge and the resistance of the battery over time. Another algorithm is used to learn the behavior of the battery to better utilize the battery’s capacity. The system then keeps a database of various characteristics of the battery. This method helps to predict the remaining battery capacity with up to 99% accuracy. TI’s bq27520-G4 uses Impedance Track technology to perform this function. The IC can also report:
battery capacity (mAh)
state-of-charge (%)
state-of-health (SOH%)
run-time to empty (min.)
voltage (mV)
temperature (°C)
Power management isn’t just for cell phones. Whether you are dealing with power tools or eMotorcyles, portable medical monitoring devices or portable audio systems, TI’s power management system can increase the battery safety on your project. If you want to see how these design advances can impact your electronic device performance, TI has the documentation that can help get you started.
Several design factors have been attributed to thermal runaway, but some result from counterfeit batteries and chargers that don’t include the requisite safety features. The engineers at Texas Instruments (TI) have looked into these causes to develop a battery platform and portable power management system to help prevent the batteries in your designs from catching fire.
Temperature Monitoring of Rechargeable Batteries
Many things can increase the chances that a battery will overheat. Some notable causes of overheating are: improper ventilation (like charging under a pillow), using the device while charging (or in extreme conditions), and using counterfeit batteries. Thankfully, a simple thermistor can help detect when the battery is over-heating.
When a battery is being charged, a certain amount of voltage and current is being applied to the battery. Too much current or too much voltage can create a very hot battery. Many battery management systems will monitor only current or voltage, but TI’s bq24060 and bq24070 will monitor them both to ensure safe charging. This video shows that once the temperature reaches a safety margin, the power to the battery is shut off.
However, temperature monitoring is the last line of defense to ensure product and user safety. Designers must also ensure that authentic batteries are used and the charging is properly managed.
Authentication & Identification of Replacement Batteries
Not all consumers will listen to the warnings to use your custom made batteries and chargers. Unfortunately, counterfeit batteries that aren’t specifically designed for a device may not supply the correct voltage and current levels while charging.
To prevent counterfeit battery use, TI has a portfolio of authentication devices that range from the basic to very complex. If the battery doesn’t pass authentication, then the device will either not start or it will send an error message during start-up.
The simplest of schemes use Identification-Based Authentication. It works somewhat like wireless authentication and identification. A host (phone) sends a constant signal to the responder (battery) and a constant reply is sent back. The host can then read the data and verify that the battery was made for the product. The bad news with this scheme is that the codes can be duplicated by counterfeiters, often within just weeks of production.
For added security, a challenge and response-based authentication scheme can help to confound the counterfeiters. This scheme changes the challenge and response each time the battery is inserted. The security is in a secret key that is shared between the device and the battery. When the battery is plugged in, the phone sends a set of numbers that are fed into the key. If the returned value matches the value calculated by the host, the device is powered up.
The challenge and response-based scheme also employs public authentication. Public authentication platforms are effective because they can more thoroughly evaluate against attacks seeking to uncover the secret key.
For even more security, the SHA-1/HMAC-based (Secure Hash Algorithm-1/Hash Message Authentication Code) can be implemented. This method has been used for several years to secure internet transactions. It works similarly to the Challenge and Response scheme using a secret key. However, this method uses a 160-bit challenge. This creates 2160 or 1.46 x 1048 possibilities, which greatly increases security. If you want to use this method, then TI’s bq26100 IC is right for your design.
Charging Management
As a safety feature, typical chargers place the battery and the system in parallel with each other. In this configuration, if a user is charging their battery while using the phone, less current is available to charge the battery. In some designs, if the system current is greater than the battery current, then the battery will actually start discharging. That’s why turning off GPS and Wi-Fi systems will charge your phone faster.
Other configurations manage battery charging differently. For example, the current flow Power Path Management (PPM) system uses a pair of transistors to control how much power is on the power bus and the amount of current that is applied to the battery. This ensures a regulated amount of voltage and current are applied to the battery during the charging cycle.
Additionally, a Dynamic PPM (DPPM) will maximize the available power from the adapter by monitoring the power bus for input fluctuations. In this set up, if the battery and system current becomes greater than the current being supplied, then adjustments are made so that both receive a proper amount of current equal to what is available. Additionally, this configuration will allow your design to use a smaller power rating and a less expensive AC adapter. This DPPM set up is used in TI’s bq24070 IC.
Fuel Gauging
Has your battery gauge ever told you that you have 20 minutes of charge remaining, only to shut down 2 seconds later? Fuel gauging isn’t just for user satisfaction. It’s also important in measuring the proper battery charge.
Most devices employ either a voltage-based or the coulomb counting-based algorithm to determine the charge of your device’s battery. However, both of these algorithms have their limitations.
TI’s patented Impedance Track™ technology, however, uses both algorithms to help measure the charge and the resistance of the battery over time. Another algorithm is used to learn the behavior of the battery to better utilize the battery’s capacity. The system then keeps a database of various characteristics of the battery. This method helps to predict the remaining battery capacity with up to 99% accuracy. TI’s bq27520-G4 uses Impedance Track technology to perform this function. The IC can also report:
battery capacity (mAh)
state-of-charge (%)
state-of-health (SOH%)
run-time to empty (min.)
voltage (mV)
temperature (°C)
Power management isn’t just for cell phones. Whether you are dealing with power tools or eMotorcyles, portable medical monitoring devices or portable audio systems, TI’s power management system can increase the battery safety on your project. If you want to see how these design advances can impact your electronic device performance, TI has the documentation that can help get you started.
No comments:
Post a Comment