Battery protection IC introduces battery equalization function
Updatezeit: 2022-09-02 17:20:38
Battery management ICs have been a very hot category of products, and the application of the right battery management ICs can improve the efficiency of battery power, extend the service life, and make the system more reliable. Different categories of battery management IC applications vary greatly, from battery certification ICs to charger ICs, from power monitoring to balancers, and what we are focusing on today - battery protectors.
We know that battery packs containing lithium-based (lithium-ion and lithium polymer) chemistry have high energy density and long endurance but do not have memory effects compared to some other technology lithium batteries. These characteristics make Li-ion batteries ideal for portable electronic systems. Still, Li-ion batteries need to operate within their rated limits, focusing on performance and safety. Therefore, detecting various fault conditions (including overvoltage OV, Undervoltage, discharge overcurrent OCD, and overheating OT) in single-cell and multi-cell batteries is critical. The application of battery protectors is to avoid such fault conditions and enhance the safety of the battery pack.
How to choose the battery protector, battery monitor, and charge monitor meter?
Battery protectors, monitors, and power meters are similar in their applications. This battery management ICs will signal the system or respond directly when a monitored value or several monitored values (voltage, current, temperature) are out of limits. Such a response may be to send a signal to the system, communicate with the system, or make a switch to prevent charging or discharging, or in some cases, the response may even be to disconnect the fuse directly.
So what is the most appropriate choice? This needs to be determined by the type of battery pack. For simple battery packs, a simple protector will meet all protection needs, and at the integration level, the protector is the simplest hardware-based protection. This battery protector can be a basic overvoltage or advanced protector capable of responding to Undervoltage, temperature faults, or current faults.
Battery monitors are used in higher cell counts. The battery monitor measures a single cell's voltage, current, and temperature and reports these values to the controller. Battery monitors can also provide battery balancing to extend battery runtime and life. Typical battery monitors also include highly configurable IC protection features.
A power meter can be used for more advanced battery packs, which is the most integrated class of ICs from an integration standpoint. Power meters incorporate the functionality of battery monitors and integrate advanced monitoring algorithms on top of them. The power meter IC reports the remaining battery power, runtime, and charge status, and software-based protection further enhances the battery protection.
Suppose the battery monitor greatly increases the flexibility of the battery pack design. In that case, the power monitor meter maximizes the integration of the battery pack design. In contrast, the battery protector, as the simplest hardware-based protection, keeps the complexity of the battery pack design to a minimum.
Different protection types of battery protectors with balanced function introduction
According to the different protection types of battery protectors, the different protection levels now have over-voltage protection, over-voltage plus discharge over-current protection, and over-voltage plus discharge over-current plus over-heat protection. Generally speaking. However, battery packs either require protection ICs that provide only the most basic overvoltage protection or provide fully integrated various protection functions.
Some simple battery packs may require only basic overvoltage protection (OVP). The battery protection device provides precise monitoring and triggering threshold for overcurrent protection in the event of high discharge/charge current operation or overcharging of the battery. Typically, these overvoltage protection-only ICs monitor external power FETs to provide protection during high charging or discharging currents. Some overvoltage protection ICs will integrate charge pump FET drivers to provide high-side primary cell protection for single-cell LiPo batteries, achieving consistency in Rdson for all cell voltages. In terms of overvoltage protection, these most basic battery protection ICs currently have an industry-leading accuracy of around ±10mV and Under-voltage protection accuracy of around ±20mV.
Achieve a full set of voltage, current, and temperature protection functions of the battery protection IC is now more common and can be independently monitored for each battery has over-voltage, under-voltage, and open circuit conditions. Overheat detection is mostly done by adding external NTC or PTC thermistors.
Some battery protectors implement intelligent battery balancing algorithms without MCU control through integrated FETs. The balancing function enables the battery pack to be balanced in a multi-cell battery by automatically discharging the high-voltage fully charged cells and keeping the low-voltage cells in the series charged during charging.
Primary and secondary protection
In some high-cell battery packs, overvoltage and discharge overcurrent protection and overheat protection are not enough to meet the needs of the battery pack. This time you need the battery mentioned above protection IC with battery autonomy balancing function, this type of protection IC is usually used as a primary protector. This device controls the charging and discharging FET to respond to different types of protection faults.
The fuse will be blown when an overvoltage condition is detected to prevent the battery pack from overcharging. The protector belongs to the secondary protection, a higher response than the FET safety factor. Generally, when secondary protection is required, the battery system needs to be equipped with a battery monitor or power monitor because the battery voltage and current are transmitted to the MCU for system-level decision-making, and the battery monitor is generally more selective.
The secondary protector independently monitors each battery for an overvoltage condition. Depending on the configuration, the secondary protector will trigger an output after a fixed delay if any of the multiple batteries are overvolted. After the overvoltage condition meets the specified delay timer condition, the output will trigger to a high state, and the fuse will blow.
Li-ion battery protection chip gates the battery pack safety to prevent battery overcharge, over-discharge, and over-current function. With more and more applications of multi-cell lithium batteries, large-capacity battery pack requirements for the protection IC is also increasingly high. To ensure the safety of the battery pack, the battery protection IC also needs to equalize the battery to eliminate the individual battery pressure difference to enhance the battery pack's performance.
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