内蒙古工业大学毕业论文外文翻译

Design of a Lead-Acid Battery Charging and

Protecting IC in Photovoltaic System

1.Introduction

Solar energy as an inexhaustible, inexhaustible source of energy more and more

attention. Solar power has become popular in many countries and regions, solar

lighting has also been put into use in many cities in China. As a key part of the solar

lighting, battery charging and protection is particularly important. Sealed

maintenance-free lead-acid battery has a sealed, leak-free, pollution-free,

maintenance-free, low-cost, reliable power supply during the entire life of the battery

voltage is stable and no maintenance, the need for uninterrupted for the various types

of has wide application in power electronic equipment, and portable instrumentation.

Appropriate float voltage, in normal use (to prevent over-discharge, overcharge,

over-current), maintenance-free lead-acid battery float life of up to 12 ~ 16 years float

voltage deviation of 5% shorten the life of 1/2. Thus, the charge has a major impact

on this type of battery life. Photovoltaic, battery does not need regular maintenance,

the correct charge and reasonable protection, can effectively extend battery life.

Charging and protection IC is the separation of the occupied area and the peripheral

circuit complexity. Currently, the market has not yet real, charged with the protection

function is integrated on a single chip. For this problem, design a set of battery

charging and protection functions in one IC is very necessary.

2.System design and considerations

The system mainly includes two parts: the battery charger module and the

protection module. Of great significance for the battery as standby power use of the

occasion, It can ensure that the external power supply to the battery-powered, but also

in the battery overcharge, over-current and an external power supply is disconnected

the battery is to put the state to provide protection, the charge and protection rolled

into one to make the circuit to simplify and reduce valuable product waste of

resources. Figure 1 is a specific application of this Ic in the photovoltaic power

内蒙古工业大学毕业论文外文翻译

generation system, but also the source of this design.

Maintenance-free lead-acid battery life is usually the cycle life and float life

factors affecting the life of the battery charge rate, discharge rate, and float voltage.

Some manufacturers said that if the overcharge protection circuit, the charging rate

can be achieved even more than 2C (C is the rated capacity of the battery), battery

manufacturers recommend charging rate of C/20 ~ C/3. Battery voltage and

temperature, the temperature is increased by 1 °C, single cell battery voltage drops 4

mV, negative temperature coefficient of -4 mV / ° C means that the battery float

voltage. Ordinary charger for the best working condition at 25 °C; charge less than the

ambient temperature of 0 °C; at 45 °C may shorten the battery life due to severe

overcharge. To make the battery to extend the working life, have a certain

understanding and analysis of the working status of the battery, in order to achieve the

purpose of protection of the battery. Battery, there are four states: normal state,

over-current state over the state of charge, over discharge state. However, due to the

impact of the different discharge current over-capacity and lifetime of the battery is

not the same, so the battery over discharge current detection should be treated

separately. When the battery is charging the state a long time, would severely reduce

the capacity of the battery and shorten battery life. When the battery is the time of

discharge status exceeds the allotted time, the battery, the battery voltage is too low

may not be able to recharge, making the battery life is lower.

Based on the above, the charge on the life of maintenance-free lead-acid batteries

have a significant impact, while the battery is always in good working condition,

battery protection circuit must be able to detect the normal working condition of the

battery and make the action the battery can never normal working state back to

normal operation, in order to achieve the protection of the battery.

3.Units modular design

3.1The charging module

Chip, charging module block diagram shown in Figure 2. The circuitry includes

current limiting, current sensing comparator, reference voltage source, under-voltage

内蒙古工业大学毕业论文外文翻译

detection circuit, voltage sampling circuit and logic control circuit.

The module contains a stand-alone limiting amplifier and voltage control circuit,

it can control off-chip drive, 20 ~30 mA, provided by the drive output current can

directly drive an external series of adjustment tube, so as to adjust the charger output

voltage and current . Voltage and current detection comparator detects the battery

charge status, and control the state of the input signal of the logic circuit. When the

battery voltage or current is too low, the charge to start the comparator control the

charging. Appliances into the trickle charge state when the cut-off of the drive, the

comparator can output about 20 mA into the trickle charge current. Thus, when the

battery short-circuit or reverse, the charger can only charge a small current, to avoid

damage to the battery charging current is too large. This module constitutes a charging

circuit charging process is divided into two charging status: high-current

constant-current charge state, high-voltage charge status and low-voltage constant

voltage floating state. The charging process from the constant current charging status,

the constant charging current of the charger output in this state. And the charger

continuously monitors the voltage across the battery pack, the battery power has been

restored to 70% to 90% of the released capacity when the battery voltage reaches the

switching voltage to charge conversion voltage Vsam charger moves to the state of

charge. In this state, the charger output voltage is increased to overcharge pressure Voc

is due to the charger output voltage remains constant, so the charging current is a

continuous decline. Current down to charge and suspend the current Ioct, the battery

capacity has reached 100% of rated capacity, the charger output voltage drops to a

lower float voltage VF.

3.2 Protection Module

Chip block diagram of the internal protection circuit shown in Figure 3. The

circuit includes control logic circuit, sampling circuit, overcharge detection circuit,

over-discharge detection comparator, overcurrent detection comparator, load

short-circuit detection circuit, level-shifting circuit and reference circuit (BGR).

This module constitutes a protection circuit shown in Figure 4. Under the chip

内蒙古工业大学毕业论文外文翻译

supply voltage within the normal scope of work, and the VM pin voltage at the

overcurrent detection voltage, the battery is in normal operation, the charge and

discharge control of the chip high power end of the CO and DO are level, when the

chip is in normal working mode. Larger when the battery discharge current will cause

voltage rise of the VM pin at the VM pin voltage at above the current detection

voltage Viov, then the battery is the current status, if this state to maintain the tiov

overcurrent delay time, the chip ban on battery discharge, then the charge to control

the end of CO is high, the discharge control side DO is low, the chip is in the current

mode, general in order to play on the battery safer and more reasonable protection, the

chip will battery over-discharge current to take over the discharge current delay time

protection. The general rule is that the over-discharge current is larger, over the

shorter the discharge current delay time. Above Overcharge detection voltage, the

chip supply voltage (Vdd> Vcu), the battery is in overcharge state, this state is to

maintain the corresponding overcharge delay time tcu chip will be prohibited from

charging the battery, then discharge control end DO is high, and charging control

terminal CO is low, the chip is in charging mode. When the supply voltage of the chip

under the overdischarge detection voltage (Vdd dl,), then the battery is discharged

state, this state remains the overdischarge delay time tdl chip will be prohibited to

discharge the battery at this time The charge control side CO is high, while the

discharge control terminal DO is low, the chip is in discharge mode.

4.Circuit Design

Two charge protection module structure diagram, the circuit can be divided into

four parts: the power detection circuit (under-voltage detection circuit), part of the

bias circuit (sampling circuit, the reference circuit and bias circuit), the comparator

(including the overcharge detection /overdischarge detection comparator, over-current

detection and load short-circuit detection circuit) and the logic control part.

This paper describes the under-voltage detection circuit (Figure 5), and gives the

bandgap reference circuit (Figure 6).

Battery charging, voltage stability is particularly important, undervoltage,

内蒙古工业大学毕业论文外文翻译

overvoltage protection is essential, therefore integrated overvoltage, undervoltage

protection circuit inside the chip, to improve power supply reliability and security.

And protection circuit design should be simple, practical, here designed a CMOS

process, the undervoltage protection circuit, this simple circuit structure, process and

easy to implement and can be used as high-voltage power integrated circuits and other

power protection circuit.

Undervoltage protection circuit schematic shown in Figure 5, a total of five

components: the bias circuit, reference voltage, the voltage divider circuit, differential

amplifier, the output circuit. The circuit supply voltage is 10V; the M0, M1, M2, R0 is

the offset portion of the circuit to provide bias to the post-stage circuit, the resistance,

Ro, determine the circuit's operating point, the M0, M1, M2 form a current mirror; R1

M14 is the feedback loop of the undervoltage signal; the rest of the M3, M4 and M5, M6,

M7, M8, M9, M10, M11, M12, M13, M14, composed of four amplification comparator;

M15, DO, a reference voltage, the comparator input with the inverting input is fixed

(V+), partial pressure of the resistance R1, R2, R3, the input to the inverting input of

the comparator, when the normal working of the power supply voltage, the inverting

terminal of the voltage detection is lost to the inverting terminal voltage of the

comparator is greater than V+. Comparator output is low, M14 cutoff, feedback circuit

does not work; undervoltage occurs, the voltage divider of R1, R2, R3, reaction is more

sensitive, lost to the inverting input voltage is less than V when the resistor divider,

the comparator the output voltage is high, this signal will be M14 open, the voltage

across R into M at both ends of the saturation voltage close to 0V, thereby further

driving down the R1> R2, the partial pressure of the output voltage, the formation of

the undervoltage positive feedback. Output, undervoltage lockout, and plays a

protective role.

5. Simulation results and analysis

The design of the circuit in CSMC 0.6 μm in digital CMOS process simulation

and analysis of the circuit. In the overall simulation of the circuit, the main

observation is that the protection module on the battery charge and discharge process

内蒙古工业大学毕业论文外文翻译

by monitoring Vdd potential and Vm potential leaving chip CO side and DO-side

changes accordingly. The simulation waveform diagram shown in Figure 7, the

overall protection module with the battery voltage changes from the usual mode

conversion into overcharge mode, and then return to normal working mode, and then

into the discharge mode, and finally back to normal working mode. As the design in

the early stages of the various parameters to be optimized, but to provide a

preliminary simulation results.

6.Conclusion

Designed a set of battery charging and protection functions in one IC. This

design not only can reduce the product, they can reduce the peripheral circuit

components. The circuit uses the low-power design. This project is underway to

design optimization stage, a complete simulation can not meet the requirements, but

also need to optimize the design of each module circuit.