laptop Batteries: A new integrated battery charge and discharge control equipment

A new integrated battery charge and discharge control equipment

As a number of military applications large uninterruptible power equipment, energy consumption, so battery packs commonly used in serial mode to avoid excessive current. Serial battery charge and discharge with a single battery charge and discharge is different in different cell battery if the differences were not taken seriously it will cause the battery pack is less efficient, reducing battery life; consider the application of military equipment, the environment special requirements, not on the market today meet these requirements an integrated charge and discharge control equipment, so there could very well designed to meet these needs a new type of integrated battery charge and discharge control equipment.

1 System Overview

The integrated battery charge and discharge control equipment for the control of the MC68HC908SR12 microcontroller core, ancillary control design using FPGA. Including power supply circuit, constant current constant voltage charging control unit, balancing the discharge control unit, the central control unit, FPGA auxiliary control unit, temperature detection circuit, man-machine interface circuit. Integrated battery charge and discharge control equipment, primarily for military applications, a larger number of uninterruptible power equipment, energy consumption, commonly used in the case of the battery power supply in series design. Considered in the design process focused on the balance of the battery characteristics, to improve the series battery-powered group of efficiency and prolong its service life. Figure 1 is a block diagram of the system.

2 Hardware Design

Here on the charge and discharge control equipment, integrated overview of the hardware design process description.

2.1 Power Circuit

Charger using switching power supply as power supply equipment. Switching Power Supply using Pulse Modulation PWM (Pulse Width Modulation) and the MOSFET, BTS, IGBT design and other electronic devices. Switching power supply high degree of integration, with a voltage regulator, current limiting, thermal protection. Compared with the linear power supply input voltage range (typically up to AC 85 ~ 265 V), small size, light weight and high efficiency. Meanwhile, the easy-to-FPGA auxiliary control unit to control it.

2.2 Charge Control Unit

Charging control unit using the current constant current constant voltage charging more mature circuit design is completed. Figure 2 is a circuit schematic. Constant current circuit from Motorola's microcontroller chip MC68HC908SR12 analog circuit module and the chip of the MOSFET switch, Schottky diodes, filter inductors, filter capacitors and other components composition. Analog circuit module is Motorola's microcontroller-specific parts MC68HC908SR12, which consists of the input multiplexer, programmable amplifier groups, on-chip temperature sensor, current detection circuit. The total magnification the amplifier can be programmed 1 to 256. Amplifier input can choose 2 analog input pin (ATD0, ATD1), on-chip temperature sensor, analog input (VSSAM). ATD0 and VSSAM can be connected between a current sense resistor for measuring the external current, it also connected to the current detection circuit, when the current exceeds a specified value and generate an interrupt when the output signal.

In the charge before the start of pre-processing stage, according to the different characteristics of the battery is detected, the software select the appropriate charging algorithm, the charging algorithm assisted by the control unit MCU and FPGA implementation. After the start of charging, the software timer capture the voltage sensing resistor R value, calculated that the output of single chip set control parameters SR12. Meanwhile, the current real-time detection of charge current detection circuit, when the current exceeds a specified value generates an interrupt when the SCM in a timely manner by the SR12 off the charge current to achieve constant current charge control.

Equalizing charge is a comprehensive control of the charge and discharge an important feature of the device. In the charging process, the quality is not the same as the battery capacity of the small, poor quality of the battery terminal voltage during the charge into the same voltage will appear after power up the battery more than the other, and if no measures are taken, they will be the voltage difference will increase, as well as one of the safety of the battery very quickly reach the required voltage, the charging process will be forced to stop. At this time of high pressure should stop charging the battery, that is a balanced charge. This will help restore damaged cells within the battery so that the charging process can go smoothly.

2.3 Discharge Control Unit

Discharge control unit are 2 parts, one flyback balance discharge circuit, can achieve the balance of battery discharge. Equilibrium discharge is the integrated charge and discharge control equipment, an important feature. In the discharge process, due to individual differences in the battery, and if no measures are taken, the battery pack inside the battery of individual differences will become increasingly clear that this would reduce the efficiency of the battery pack, the service life reduced. Returning to the discharge control unit flip-firing circuit design, the schematic diagram shown in Figure 3, the inductance of the circuit itself has a terminal voltage of each contain characteristics (also known as the relaxation of the circuit back) battery discharge the battery can balance the individual discharge. This will help restore the damaged unit within the battery, improving efficiency and battery life. Second, over-discharge protection circuit that can be achieved over the battery discharge protection. Figure 4 is the battery over-discharge protection circuit diagram, when the terminal voltage detection circuit detects the voltage drops below the set of safe discharge voltage, the discharge circuit protection circuit can be cut to achieve the protection of the battery.

2.4 The temperature detection circuit

During charging, the battery temperature will increase with the increase of charge capacity, particularly near the termination charge, temperature, rate of change of △ T / △ t most, this feature is to determine whether the battery is filled with one of the main conditions. Therefore, produced by National Semiconductor's single-chip design of high accuracy digital temperature sensor LM92 temperature detection circuit. The circuit diagram shown in Figure 5.

2.5 man-machine interface unit

(1) keyboard response circuit

Response to the circuit design of the keyboard, use MC68HC908SR12 MCU PORT D (PTD6 and PTD7) port keyboard interrupt (KBI). According to the actual situation, the microcontroller in the keyboard interrupt MC68HC908SR12 enable register KBIER the corresponding value in the write, write "1" means interrupt enable, write "0" can not be interrupted. Keyboard interrupt to allow the port, MC68HC908SR12 SCM will pull its internal 30 kΩ resistor, this circuit design the keyboard response is very simple, should be noted that application software routines to increase the keyboard jitter elimination, to prevent misuse.

(2) status display circuit

Status display circuit design using microcontroller MC68HC908SR12 PORT A (PTA0 ~ PTA5) port, LED direct drive capability. PORT A first set when programming the work of the state, the LED control register is written to the corresponding value of LEDA, write "1" can directly drive LED, write "0" as the standard I / O ports. Have at each stage in the charge status display, such as: the battery is being charged, the battery temperature is too high due to enter the temperature status.

2.6 FPGA central control unit and auxiliary control unit

FPGA central control unit and auxiliary control unit integrated charge and discharge the main control equipment to achieve the status of the control transfer function. Depending on the sensor for different conditions, different written instructions, conversion of different modes.

3 Software Design

Shell discharge control equipment, software, integrated design that is: the various functional components of modular programming, software process using interrupted work. The aim is to make application process clear, readable, easy-to-functional debugging and product maintenance and upgrades. This software mainly consists of initialization, preprocessing, control algorithms, charge and discharge 4 parts.

3.1 Initialization

The initial phase of the program should first initialize the microcontroller MC68HC908SR12 operation, including setting I / O port input / output status, set the PLL phase-locked loop circuit parameters, set the timer TIM parameters.

3.2 Pretreatment

Preprocessing stage is the integrated charge and discharge control equipment, the preparation phase before work. Program is initialized, the first microcontroller based on the use MC68HC908SR12 internal temperature sensors detect ambient temperature. When the ambient temperature is too low or too high, it can not discharge the battery, otherwise it will damage the battery. Then, set the A / D converter and channel parameters to detect the battery voltage. Experience in the testing data with the theoretical value comparison to determine the type of battery and is connected correctly. Of low battery voltage, the use of short pulse current charge, which will help activate the chemical reaction within the battery material, part of the restoration of damaged battery cell.

3.3 The charge and discharge

According to instructions given by the control unit, the charge and discharge. Integrated charge and discharge device in the hardware circuit design to take into account the balance charge, balance discharge and discharge protection, etc., so when given the appropriate software design considerations.

3.4 Control Algorithm

MC68HC908SR12 control algorithm is mainly controlled auxiliary control unit MCU and the FPGA, write the appropriate command, control, charge and discharge coordination of each module integrated device.

4 Conclusion

The integrated battery charge and discharge control equipment designed to take full account of the series battery charge and discharge the balance of effects can be applied to series battery charge and discharge control, can improve the efficiency of the battery pack in series, extending its life; taking into account that the main charge and discharge control equipment with integrated uninterruptible power supply equipment for military use, in its design and taking into account the complexity of military applications and particularity, and thus, the battery charge and discharge in the dual-use integrated control equipment has wide range of applications.

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