2DABAN AUTOMATION

A new sealed lead acid battery charger design and application of
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Abstract: This paper introduces a novel design of sealed lead-acid battery charger principle of charging parameters given to determine the method and the basic formula. Also given a simple and practical, stable and reliable 12V sealed lead-acid battery float charger, dual-level practical application of the circuit.

Keywords: sealed lead-acid battery; charger; over charge; floating charge sealed maintenance free lead-acid battery as a sealed, no leakage, no pollution, etc., are widely used at home and abroad in recent years. However, due to maintenance-free battery charging technology can not meet the special requirements and charging method is not correct and it is difficult to achieve the required cycle life. UC3906 is a special chip sealed lead-acid battery charging, it has the best rechargeable sealed lead acid batteries all the necessary control and monitoring functions. More importantly, it enables various conversion voltage with the battery charger voltage temperature coefficient of change, so that the sealed lead-acid batteries in a wide temperature range to achieve the best charge state. 1 UC3906 structure principle 1.1
UC3906 UC3906 structural characteristics of the internal structure shown in Figure 1. The chip contains independent voltage control loop and current limit amplifier, it can control the drive chip. Drives the output current up to 25mA, can directly drive an exter


nal series pass to adjust the charger output voltage and current. Comparison of voltage and current detection can be used to detect the battery's charge status, and also can be used to control the charge state logic circuit input signal. When the battery voltage or temperature is too low, the charge enable comparator can control the charger enters trickle charge state. When the drive ended, the comparator can output 25mA trickle charge current. Thus, when the battery short circuit or reverse, the charger can only charge a small current, thus avoiding the charge current is too large due to damage to the battery. UC3906's a very important feature is its internal reference voltage with the precise variation of ambient temperature and the temperature characteristics of lead-acid battery voltage exactly. Meanwhile, the chip can only 1.7mA input current work, thus reducing the power consumption of the chip, the work environment to achieve accurate temperature testing to ensure that both the battery fully charged without serious overcharge. In addition, UC3906 chip also includes an input under-voltage detection circuit to initialize the charge cycles and may drive a logic output. When coupled with the input power, the device can also indicate the 7 foot power status. 1.2
UC3906 charging parameters determine the external components can be a very small sealed lead-acid batteries to achieve fast and accurate charging. Figure 2 is a complete charger circuit. Which by the RA, RB, and Rc the resistor divider network can be used to detect the battery voltage. In addition, the circuit can also be a reference voltage with the precise (VREF) compared to determine the float voltage, over-charge voltage and trickle charge threshold voltage. A battery charge cycle can be divided by the time high-current fast charge state, charge state and floating charge over the state and other three, the charging parameters are VF, Voc, IMAX, IOCT and so on. Them with the RA, RB, Rc, Rs relationship can be reflected from the following formula: VOC = VREF 1 + RA / RB + RA / RC VF = VREF 1 + RA / RB IMAX = 0.25V/RsIOCT = 0.025V / Rs in the above formula, VF, Voc and is proportional to VREF. VREF temperature coefficient of-3.9mV / , IMAX, IOCT, Voc, VF can be independently set. As long as the input power to allow or power tubes can bear, IMAX's value can be as large as possible. Although some manufacturers said that if there was sufficient protection circuit, the charging rate can be achieved even more than 2C, but the battery manufacturer's recommended charge rate range C/20 ~ C / 3. Charge termination current IOCT had the choice should be as much as possible close to 100% charge the battery. Voc and the appropriate value depends on the battery charge current when Voc attenuation. IMAX and IOCT respectively by current limiting amplifier and current sense amplifier offset voltage and current sense resistor Rs decisions. VF
, Voc of the value from the internal reference voltage VREF and the external resistors RA, RB, Rc a network to decide. Figure 2
Dual level float charger 2, the practical application of the basic circuit diagram 3 for an environmental parameter test in the practical application of the battery charger circuit. Where: Battery is rated at 12V, capacity 7Ah, VIN = 18V, VF = 13.8V, Voc = 15V, IMAX = 500mA, IOCT = 50mA. As always connected to the battery on the charger to prevent battery into the charger output current should be adjusted in the series between the pipe and the output of a diode in series. In order to avoid the battery after the interruption input power divider resistors R3 through the discharge, the design will be instructed through the power transistor R3 (7 feet) to the ground. When the 18V input voltage added, the series power transistor TIP42C turn, began high current constant current charging, the charge current is 500mA, then the same charge current, battery voltage is gradually increased. When the battery voltage reaches over 95% of charging voltage Voc (ie, 14.25V), the battery state of charge transfer over, this time over the charging voltage to maintain the charge voltage, charge current begins to decline. When the charge current drops off charge termination current (IOCT) when, UC3906 10-pin output high, LM339 comparator output low, the battery automatically transferred to floating state. While LED light indicates fully charged, indicating that the battery is fully charged. Figure 3
12V sealed lead-acid battery float charger, dual-level circuit 3 Conclusion Because of a very small external components to connect in a wide temperature range to achieve precise and rapid battery charging, the battery charger with UC3906 simplifies the design process . The charger shows that in practical applications: it has a simple, practical, stable, and reliable performance. - -" Digital Shanghai "spatial information based data platform Construction Planning
. Proposed organization of management to develop as soon as possible, including on shared ways of data exchange agreements, the normative content of guidance documents and implementation. The basis of established geospatial data sharing platform. The use of ClCompatible with each other and exchange information platform conditions and capabilities. 3, on the "Digital Shanghai" the operation of spatial information organization based data platform vision: 1) administrative organization of the relevant units in the existing form the basis of a
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