Current detection method in lithium battery charging circuit

Lithium is a very active metal. Lithium ion batteries made of lithium have been widely used because of their high discharge current, low internal resistance, long life and no memory effect. However, overcharge, overdischarge and short circuit are strictly prohibited in the use of lithium-ion batteries, otherwise, the battery life will be shortened or accidents such as fire and explosion will be caused. Therefore, rechargeable lithium-ion batteries will be connected with a charging and discharging protection circuit board (often referred to as protection board) to protect the safety of cells. Current detection and charge discharge control circuit is an important part of lithium battery protection circuit. When the current detection circuit detects that the charging and discharging current is too large, the lithium battery protection circuit cuts off the charging circuit by closing the overcharge or overdischarge control tube, so as to protect the lithium battery. At present, the lithium battery protection circuit with current detection circuit is mainly some ASIC. These ASIC have the problems of high cost and low detection current.

The following introduces a charging current detection circuit to solve the problems of high cost and small detection circuit in the existing lithium battery protection circuit.

The charging current detection circuit includes a current detection chip sc810, a controller, a decoupling capacitor C1, a noise reduction capacitor C2, an overdischarge control tube and an overcharge control tube; the negative pole of the lithium battery is connected with the source pole and the ground of the overdischarge control tube, the drain pole of the overdischarge control tube is connected with the drain pole of the overcharge control tube, and the source pole of the overcharge control tube is connected with the negative pole p - of the battery system.

The sc810 series of Xinggong micro is an isolated current detection chip based on the open-loop Hall sensor detection principle. By introducing the current wire at the high voltage side into the package, based on the magnetic effect of the current, the proportional magnetic field generated around the measured wire is induced by the magnetic sensor of the built-in chip, and then converted into a processable proportional voltage signal. The voltage signal is read and amplified by the built-in high-precision ADC, and the loops such as temperature, noise, hysteresis and nonlinearity are removed with digital calibration technology Environment variable, the final output and measured current value into an ideal ratio of the voltage value, to achieve isolated current measurement.

When the lithium battery is charged and discharged, the current detection circuit outputs a voltage signal according to the current, and the controller converts the voltage signal by ad. the converted value is used to judge overcharge or overdischarge. When overcharge or overdischarge occurs, the overcharge control tube or overdischarge control tube is used to control the charge and discharge current, so as to detect up to tens of amperes at a very low cost It solves the problems of high cost and small detection circuit in the existing lithium battery protection circuit.

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