The solution of lithium-ion battery protection

Currently, the application of lithium-ion battery has become more and more widely, including mobile phones, MP3, MP4, GPS, toys and other portable devices, etc. and gas meter needs to persist data, the market capacity has reached hundreds of millions per month. In order to prevent shortening of service life of lithium-ion battery affected by abnormal states such as over charge-discharge, over current, it usually needs a protection device to prevent damage of abnormal states of the battery.

Lithium battery protection circuit principle as shown in figure 1, are mainly controlled by the battery protection IC and external discharge switch M1 and M2 charging switch to achieve. When the P + / P - connected charger, to normal battery charging, M1 and M2 in conducting state; When charging control IC detected anomalies, M2 will shut off charging termination. When the P + / P - connected load, battery normal discharge, M1 and M2 conduction; When control IC detects abnormal discharge, M1 turn off end discharge.

Several existing lithium-ion battery protection scheme

Figure 2 is based on the principle of lithium battery protection designed a kind of commonly used lithium battery protection board. In figure 2 SOT23-6 l encapsulation is control IC, SOP8 encapsulation is double switch tube M1, M2. Due to manufacturing control IC technology and manufacture of the switch tube technology each are not identical, so figure 2 two chips are made from different process, usually the two chips are also provided by different manufacturers.

Appeared in recent years, the industry will be a few chip packages together in order to improve the level of integration, the trend of the reduction of final solution size. Lithium battery protection market is no exception. Two kinds of lithium battery protection scheme in figure 3 A and B is to look in figure 2 two integrated on A chip, but in fact its internal controller IC encapsulation and switch tube chip is still divided, from different manufacturers, the plan is to only the two closes together, commonly known as "the combination of two core".

Due to internal two chips are actually still coming from different vendors, appearance is not a good match, so eventually to encapsulate a variety of shapes, in many cases, general packaging will not be used. This package volume is bigger, and can't save peripheral components, so the scheme of "the unity of" the second core and province actually no too much space. In terms of cost, although the two-cost reduced to a packaging costs, but because of this package is usually large, some is not general encapsulation, sometimes in order to reduce packaging size, need to use chip stack packaging format, so compared with the traditional scheme of two chips, its cost advantage is not obvious.

Figure 4 is a real controller chip and switch tube chip integrated on the same wafer single chip solutions. Traditional scheme principle of the switch tube in figure 1 is N type pipe, joint between B in figure 1 and P -, commonly known as the cathode protection. In figure 4 schemes for technical reasons, switch tube can only be changed to P type tube, between B + and P +, commonly known as the anode protection. Complete protection plate, with the chip in detecting protection board test equipment and the user needs to be replaced when concept. This plan while reduce the packaging cost, but the chip cost has not been reduced, in competition with large amount of mature traditional program had no real cost advantage. In contrast with the traditional scheme of incompatible anode protection concept has become a big obstacle to its promotion process.

Above the unity of "the second core plan and single chip, the anode protection while on the area and cost brings users a certain advantage, but the advantage is not obvious. These solutions at the same time brings some disadvantages, so in competition with traditional scheme of mature customers in the process, finally can only in order to reduce the gross profit space to compete on price. Because of these solutions truly original cost and no obvious advantage, so as the traditional scheme of the control IC and switch tube chip prices, the scheme of "the unity of" the second core or the anode protection scheme was not able to shake the traditional dominance of the market.

Appeared on the market in recent years many new switch tube chip manufacturers, in order to reduce costs, the wrapping originally gold wire into a dozen copper wire, switch tube also without ESD protection. Although these products in performance compared to the brand switch tube have some differences, but because of the cost advantage of quickly preempted the secondary market, also for the traditional scheme with the unity of "the second core and the anode protection scheme to win in the competition in the market have made great contribution.

Fully integrated lithium-ion battery protection scheme

The core microelectronics through independent research and development of a number of devices and circuit patent in combination with the unique technology, integrate control IC and the switch tube in the same chip, launched the world's smallest lithium battery protection scheme XB430X series products. This series of products using the traditional N type switch tube, consistent with the traditional scheme of cathode protection principle, protection board manufacturers or battery manufacturers do not need to change any test equipment or ideas. This series of chip itself is a complete lithium battery protection scheme, without any external components lithium battery protection function can be realized. In order to prevent the Vcc line noise, it is recommended to use XB430X series chips between Vcc and battery negative terminal when an external one capacitor.

XB430X series chip integration is very high, not only to integrate the traditional control IC and switch tube, and the principle of figure 1, R1, R2, are integrated on the same chip. After the integration of the chip is very small, the smallest can use general SOT23-5 l packaging on the market. The chip series switch tube resistance is extremely low, the minimum resistance up to 40 m Ω below, with the best of the switch tube resistance on the market. When the minimum package SOT23-5 l, continuous charging and discharging current of 2.5 amps, and there will be no heat dissipation problem. If continue to charge and discharge current is greater than 2.5 A, it is recommended to use the SOP8 XB430X series packaging products.

XB430X with all the protection functions of traditional protection scheme: the overcharge protection, discharge protection, over current protection and short circuit protection. Not only that, the integration of the control IC and the switch tube in the same chip, chip temperature control IC may at any time to detect switch tube. When the battery for use in high temperature environment for a long time, or when the charge and discharge current exceed the normal charge and discharge current, the but again not over-current protection threshold and other reasons make the chip temperature too high, will start over temperature protection function, in order to protect the chip and battery. In addition, the built-in switch tube with ESD protection function, can significantly improve the protective plate and battery yield in the process.

XB430X internal control IC and switch tube from the same production process, the same manufacturer, choose the most mature generic packaging forms, thus consistent performance than traditional solutions, the unity of "the second core, the anode protection scheme is much higher.

With XB4301 series chips, the final battery protection scheme just two components and compared with the traditional scheme of five components, each SMT machine capacity and efficiency can be raised to 2.5 times. Compared with the traditional scheme, the protection plate manufacturers don't buy the resistance and the switch tube chip, not only simplify the chain of resources, and in the protection board when reduce two resistance welding plate as well as the switch tube eight solder joints, thus greatly reduces the production cost of protection plate.

At present the application of lithium batteries more and more widely, from mobile phones, MP3, MP4, GPS, toys and other portable devices to need to continue to save the data of gas meter, the market capacity has reached hundreds of millions of only a month. In order to prevent the lithium-ion batteries in charging and discharging, over current, such as abnormal state affect battery life, usually by lithium battery protection device to prevent damage of abnormal state of the battery.

Lithium-ion battery protection circuit principle is shown in figure 1, are mainly implemented by battery protection control IC and external discharge switch M1 and charging switch M2. When the P + / P – connects to charger and does normal charging, M1 and M2 are in conducting state; When the control IC detects anomalies, M2 terminates the charging. When the P + / P – connects the load, battery normal discharges, M1 and M2 are conducted; When control IC detects abnormal discharge, M1 terminates discharge.

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