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Intelligent battery charging management program

In Electronic Infomation Category: I | on October 28,2011

1 Introduction

lithium-ion battery is developed in the nineties of last century a new type of rechargeable battery. Because lithium-ion batteries have high energy density and SP691AEN datasheet and long cycle life and SP691AEN price and a series of advantages, so soon in portable electronic equipment is widely available, also received a lithium battery manufacturers favor.

mainly by the lithium-ion battery cathode active material, flammable organic electrolyte and SP691AEN suppliers and carbon negative electrode and other accessories. Therefore, the safety of lithium-ion batteries mainly by the chemical reaction between these components cause.

in use, according to the structural characteristics of lithium batteries, the maximum charge voltage should be less than 4.2 V, must not overcharge, otherwise they will take away the positive ion too dangerous. The charge and discharge are higher, and generally should be a special constant current, constant voltage charger. Usually constant current charging to the set value into the constant voltage charging, constant voltage charging to 0.1 A when the following should stop charging.

lithium battery discharge due to internal structure caused by the discharge can not all move to the cathode of lithium ion, lithium-ion must be retained in the negative part to ensure that the next charging lithium ion channels can be embedded in smooth . Otherwise, the battery life will be shortened, so the need to strictly control the discharge the discharge termination voltage.

Therefore, to design a high-precision Li-ion rechargeable lithium-ion battery management system for applications is essential. This article describes the intelligent battery charging system is designed specifically for lithium-end technology solutions. The system is suitable for lithium-ion / NiMH / Lead-acid batteries and the whole group of single real-time monitoring, cell balancing, charging and discharging voltage, temperature monitoring, using a voltage balance control, over-temperature protection, intelligent technology, is a powerful technical indicators improved battery charge management system.

2 system structure and design

charging system consists of n (expandable) charging module and host PC surveillance software. Support the charging process programming, according to constant current charging, constant voltage and other conditions set for the corresponding combination of work steps, in addition to hardware, over-voltage current protection, but also allows the user to define each channel over-voltage, over current and other parameters value, with data collection, storage, communication and analysis, power-off protection function, without loss of data. Also equipped with lithium battery management system, which is mainly from the charger, control unit, data acquisition unit and man-machine interface components, the hardware block diagram shown in Figure 1.

Figure 1 block diagram of intelligent battery charging system

3 constant current constant voltage source of design

constant current constant voltage source used as the main circuit switching power supply, which consists of the input electromagnetic interference filter (EMI), the rectifier filter circuit, power conversion circuit, PWM control circuit, the output rectifier filter circuit . Auxiliary circuit has input over-voltage protection, output over voltage protection circuit, output over-current protection circuit, output short circuit protection circuit.

switching power supply circuit block diagram shown in Figure 2.

2 switching power supply circuit diagram

unit with varistors for lightning protection, when lightning strikes, high voltage generated by the power grid to import power, varistor voltage is higher than the operating voltage, its resistance decreases, the pressure on energy consumption in the varistor.

input filter circuit composed of inductors and capacitors used double -type filter network, the input power of electromagnetic signals to suppress noise and clutter, but also to prevent high-frequency noise power itself on the grid interference.

power conversion circuit using the current most widely used MOSFET, insulated gate FET, is the use of semiconductor surface acoustic-electric effect to work. Because it is non-conductive state of the gate, it can greatly improve the input resistance. MOS gate-source voltage control is the use of size, to change the amount of charge induced semiconductor surface, thereby controlling the drain current.

forward mode using the main circuit, current mode control chip using the UC3842, the circuit shown in Figure 3. R4, C3, R5, R6, C4, D1, D2 composition buffers, and switching MOS tube and then make the switch voltage stress reduction, EMI reduction is not caused by the secondary breakdown. In the switch Q1 is off, the transformer primary coil is easy to produce peak voltage and peak current, a combination of these components together, can well absorb the peak voltage and current. R3 measured from the peak current signal in the current work cycle of the duty cycle control, and therefore the current work cycle current limit. When the voltage on R5 to 1 V,, UC3842 stop working, switch Q1 off immediately. R1 and Q1 of the junction capacitance CGS, CGD together make up the RC network capacitor charging and discharging switch directly affects the switching speed. R1 is too small, can lead to oscillations, electromagnetic interference will be great; R1 is too large, the switch will reduce the switching speed.

Z1 MOS tube usually limited to 18 V GS voltage of the following, thereby protecting the MOS. Q1s gate voltage controlled saw-shaped wave, the greater the time when the duty cycle, Q1 turns on the longer, the energy stored in the transformer the more; when Q1 is off, the transformer through D1, D2, R5 , R4, C3 release energy, but also to achieve the purpose of the magnetic field reset for the next transformer storage, ready to transfer energy. IC times the output voltage and current adjustment of the saw-shaped wave duty cycle foot size, so as to stabilize the machines output current and voltage. C4 and R6 for the peak voltage absorbing circuit. T1 secondary side rectifier circuit for the Forward.

3 main circuit constant current constant voltage source circuit

4 feedback loop design

constant voltage type of feedback loop shown in Figure 4 by using operational amplifier and the coupler in the form of composition. U0 when output increased by the sampling resistor R7, R8, R10, VR1 partial pressure, U1 pin voltage rise, when it exceeds the reference voltage U1 feet after U1 pin output high, so that Q1 turns on, the optocoupler LED OT1 light-emitting diodes, optical transistor turns on, UC3842 feet potential corresponding to low, thus changing the U1 foot output duty cycle is reduced, U0 reduced. When the output U0 is lowered, U1 foot voltage drop, when its lower than the U1 foot reference voltage U1 pin output low, Q1 is not conducting, optocoupler OT1 LED does not light, the phototransistor does not conduct, UC3842 foot potential rise high, thus changing the duty cycle increases the output U1 feet, U0 reduced. Cycle, so that the output voltage stable. VR1 can be adjusted to change the output voltage.

constant pattern similar to the previous figure, through the relay to switch the op amp current feedback can feet.

feedback loop in Figure 4 Schematic

5 PC software design

lithium battery software mainly consists of two independent software components, namely, charge control and charge data processing and analysis software. Rechargeable lithium battery control software is mainly responsible for the whole charging process monitoring and control, and generate data files and charging the battery charging data record; charging data processing and analysis software mainly for charge data visualization, data processing and data analysis capabilities, while According to the battery with a set of user requirements to provide the function [5].

two major control system software that is charging and charging data processing and analysis software by the respective functional module. Among them, the charge control software, including the preparation of the charging process, security, process the event log, data recovery and backup power protection and management modules, while the charging data processing and analysis software including data processing, graphics, dynamic curve, data export and battery with group and other functional modules.

charging process of the preparation of that channel automatically charge the preparation, it is the channel charge in the core part. Charging process can be a lot of work steps, at every step, you can define different operating modes and operating parameters, such as constant current charging, constant voltage and more. Of course, the charging step includes closing conditions and other parameters.

security is based on security needs to take protective measures. For a reasonable, normal charging process, these protective measures are usually not play a role; but most of the charging process to go through a longer time, which may occur during some of the unexpected things (such as power outages, etc.), but the user also probably because of the negligence of the master and other reasons set reasonable parameters (such as closure conditions, unreasonable), and even tested the battery itself is a problem.

set the security parameters is therefore required. Charge, once the "security" conditions are met, the charge will be safely stopped. After excluding abnormal factors, the user can still use the "continued then start the" functional recovery charge.

in the battery charging process, at any time or power outage problems in the supply system, the charging system can be on-site data protection, to ensure that field data is not lost, re-power, the charging system with self-recovery, from the seamless continuation of the last power-down place, to continue the charging process.

data processing module to achieve the following functions:

1) data of the various viewing operation: data entry, including the display / hide, set the display cycle range, the cycle of folding and start to start the process of folding and other operations;

2) data copied to the WINDOWS clipboard: mainly used to open a data file has been specified data items exported to EXCEL or WORD and other software tools, or as a text format (. TXT) Save;

3) View job information: see the corresponding charging data channel information and set up the charging process and other information;

4) view charge Event: View the channel charge during the accident (such as power failure, security, stop, etc.) or force the user operation, etc. (such as forced jump, the user stops);

5) data printing and print preview: The printer output data.

6 experimental

connected according to Figure 1 and connected to power lines, power supply and 2 on 1 # # power supply system test. First, start the management system, and start charging and discharging device, while charging through the host computer to send commands. Testing personnel records measured charging current (pressure). Table 1 1 # 2 # power supply test power supply and data recording forms.

test data in Table 1 record

7 Conclusion

verified by experiment, is expected to charge and discharge device has reached target, the battery management system will work to achieve the established functional requirements.

This intelligent battery charging system security, reliability, strong anti-interference, good human-computer interaction function; constant voltage constant current charging and discharging device with high precision, reliable, automated functional, and configure a computer running the software, making this set of systems with high precision and improved man-machine interactive function, the operator only needs to issue commands on a computer can complete all operations.

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