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Rechargeable batteries are widely used in industrial and agricultural production, defense technology and other fields, and the detection and charging of rechargeable batteries is a problem that must be solved in the use of rechargeable batteries. The battery intelligent detection and charging device is a set of equipment specially developed for the detection and charging of rechargeable batteries. In the design process, the BTS660's high-precision and high-current switch is fully utilized to realize the current and voltage conversion of the rechargeable battery during the detection and charging process, thereby realizing various functions.
1 BTS660 performance characteristics
BTS660 is a high-precision high-current power switch produced by INFINEON TECHNOLOGIES AG. It is a power MOSFET that can realize reverse battery protection by self-opening function. It can be used as an alternative to electromechanical relays, fuses and discrete circuits. A grounded load capable of reaching a DC 48 V power switch; suitable for devices such as lamps and generators that load high instantaneous currents, as well as various types of capacitive and inductive loads.
The main features of BTS660 are as follows: overload protection; current limit, load current up to 44 A, short circuit current limit is 90 A; short circuit protection; over temperature protection, operating temperature range -40 to +150 ° C, storage temperature range -55 ~ +150°C: working voltage is 5.0~58 V, overvoltage protection is 70 V; negative voltage output is locked; fast disconnection of inductive load; low resistance reverse current operation; diagnostic feedback of load current information; current open load detection; Power failure protection; electrostatic discharge protection.
2 BTS660 internal structure and its pin description
2.1 Internal structure
The BTs660 is an N-channel vertical power FET with a charge pump. It has a current control input and current feedback diagnostics for the load current. It has a variety of internal protection functions. Figure 1 is a block diagram of the internal functional structure of the BTS660. It consists of a voltage source, a voltage sensor, a temperature sensor, a charge pump standard conversion regulator, and overvoltage, current limiting, and overload protection.
The BTS660 is mainly composed of the following parts: 1) The input circuit, that is, the electrostatic discharge protection, when the current IIN flowing through the pin 3 is 0, the power switch is turned on, the device starts to work; when the IIN is not 0, the switch is closed, The device stops working. 2) Overvoltage protection circuit, when the voltage sensor detects that the voltage exceeds 70 V, the logic control circuit will disconnect the voltage source voltage. 3) Charge pump standard conversion regulator; 4) Output voltage detection circuit, detecting the output voltage to prevent the voltage from being too high or too low; 5) Overload limiting circuit, detecting the load size, when the load is too large, limiting the load to protect . 6) Current judgment and protection circuit, judging the current magnitude, and protecting when overcurrent.
2.2 Pin Description
The BTS660 is available in a T0220-7SMD package with a total of 7 pins. The functions of each pin are as follows: 1) Pins 1, 2, 6, 7: Load output, these pins must be shorted, especially in high current applications; ) Pin 3: Input, when the pin is low, the power switch is turned on; 3) Pin 4: Power input, the operating voltage is 5.0 to 58 V under normal conditions: 4) Pin 5: Load current Diagnostic feedback on the proportion of circulation.
3 BTS660 application in battery intelligent detection and charging device
According to the characteristics of the detection object - military rechargeable battery, the battery intelligent detection and charging device can mainly complete battery capacity detection, fast charging, normal charging, battery discharging, battery repair and other functions. In the system design process, the current variation range of the device is required to be relatively large, and since the reverse pulse charging method is used to realize battery charging and discharging, a charge and discharge conversion is realized in one pulse period, so the control device is required to be high. . At the beginning of the design, other devices were selected for control, but the effect was poor, and it was easy to burn. After repeated argumentation and data review, the BTS660 was finally determined to be used as a charge and discharge controller.
According to the function and characteristics of BTS660, when designing battery intelligent detection and charging device, BTS660 is used to realize battery charge and discharge control. The application design circuit diagram is shown in Figure 2. Two BTS660s (U1 and U2) are used in Figure 2, where U1 controls the charging process current, U2 controls the discharge process current, and U1's output acts as the U2 input, which allows device cascading and the INPUT termination to a constant current source. Pin 4 of BTS660 is connected to power supply; pins 1, 2, 6, and 7 are shorted as output, output is connected to load, load is rechargeable battery when charging, load is discharge resistance when discharging; pin 3 is input, input 4N25 is connected to realize photoelectric isolation; a discharge resistor is connected between the pin 5 and the ground, and the output of the pin is a charge and discharge sampling current, which is connected to the single chip through a voltage sampling circuit.
In the charge and discharge loop control, the charging and discharging circuits are each controlled by one BTS 660. When charging, when pin 3 of U1 is low level, U1 is turned on, and the constant current source and the rechargeable battery form a charging loop. At this time, the current output from the pin 5 of U1 (0UT1) is sent through the charging current sampling circuit. To the microcontroller interface, the microcontroller issues commands to control the charging of the battery. 0UT3 provides battery terminal voltage sampling for the system; when discharging, when pin 3 of U2 is low level, U2 is turned on, and the rechargeable battery and the large current discharge load form a loop. At this time, the current output of pin 5 of U2 (0UT2) After the discharge current sampling circuit sends the data to the interface of the single chip microcomputer, the single chip sends a command to control the battery discharge.
During charge and discharge, pin 3 of BTS660 controls its conduction (ground conduction), and pin 5 reflects the output current Is of the device, which can be calculated by equation (1):
Where, Is is the feedback current output from pin 5, IL is the current output from the BTS660 to the battery, and the value of Kilis is related to temperature and IL.
When detecting current, connect a resistor to ground on pin 5 of BTS660. The resistance is:
Where IL(M) is the maximum current output by the BTS660 during normal operation and Vbb is its input voltage. After calculation, the l kΩ resistor is selected.
The experiment proves that the BTS660 can be applied to the battery intelligent detection and charging device, which can fully meet the design requirements. The battery detection and charging device has also been successfully used in production, with stable operation and good results.
4 Conclusion
The BTS660 is a high-precision, high-current power switch that is powerful and low-priced, making it ideal for a wide range of battery protection and large charger designs. The battery intelligent detection and charging device designed by using BTS660 as the core control device has been mass-produced and successfully applied to a certain military field. The system runs stably and has good effects.
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