The requirements for these batteries comprise high release rates, low insertion loss from components in series by means of the cells, high-precision measurements, superfluous security protection, and no upset by means of incredibly high ESD transients.If we analyzed then we come to know that Battery-pack requirements have gone through a main evolution in the history several years, and today’s designs have considerable electronic content.Moreover, practically all Li-ion protector circuits for one- and two-cell applications have protector FETs in the low (unenthusiastic) surface of the battery. Plus key issues exacting to a low-side Li-ion protector circuit are converse. The transients shaped when the Li-ion protector opens throughout a brief short or when the battery is unplugged even as beneath load may exceed the voltage rating of semiconductors in the battery set. This theme describes a number of plan issues and suggests solutions to make your mind up or get better them. Resolution of these subjects requires attention to together the circuit design and the printed circuit board (PCB) explain.If we analyzed the Fig. 1 then we come to know that it is a block drawing of circuitry in a typical Li-ion battery set. It demonstrates an instance of a security protection circuit for the Li-ion cells and a gas gauge (capacity measuring device). The security circuitry includes a Li-ion protector that controls back-to-back FET switches. No doubt, these switches can be opened to defend the pack next to fault conditions such as in excess of voltage, beneath voltage, and over current.
If we analyzed then we come to know that the figure also comprise a temperature responsive three-terminal fuse that will open due to long-drawn-out over present or over temperature, or it can be forced to open by superfluous protection circuitry in case there is a responsibility where the main protection circuitry fails to respond. As opening this fuse is a previous resort, as it will render the pack enduringly disabled. The gas-gauge circuitry events the charge and discharge present by measuring the voltage crossways a low-value sense resistor with low-offset dimension circuitry.
Furthermore, the present measurement is incorporated to decide the alter in coulometric ability. In adding up, the gauge measures temperature plus voltage, assess gas-gauging algorithms to decide the obtainable capacity in the battery, and computes time-to-empty and additional values necessary by the host. The available capacity as well as additional measurements and computational outcome are communicated to the host over a sequential communication line. A diagram indication of obtainable ability can be displayed by the LEDs when make active by a push-button switch.
Fig. 1. Block diagram of circuitry in a typical Li-ion battery pack.
OPTIMIZING THE DESIGN FOR MEASUREMENT PRECISION
Let’s take a look upon measurement precision requires a precise measurement data gaining system and measurement sensor and also need a cautious board layout. Moreover, if the designer does not pay notice to all these items, the ensuing system performance may not transport the expected results.
The sense resistor and how it is linked to the data gaining system are dangerous design decisions. The intelligence resistor may see changes in temperature that are much bigger than the ambient difference of the battery pack due to power debauchery in the resistor. Use of a low-temperature coefficient resistor will get better obtainable capacity and current-measurement precision. The effectual sense confrontation seen by the dimension circuitry may depend on how the printed circuit board (PCB) etch is linked to the sense resistor. If the intelligence re