Use of batteries as power sources - Research Paper Example

Running Head: USE OF BATTERIES AS POWER SOURCES Use Of Batteries As Power Sources [The [The of the Institution] Use Of Batteries As Power Sources Battery Circuit Introduction If we analyzed then we come to know that Battery-pack requirements have gone through a main evolution in the history several years, and today's designs have considerable electronic content. No doubt, the requirements for these batteries comprise high release rates, low insertion loss from components in series by means of the cells, high-precision measurements, superfluous security protection, and no upset by means of incredibly high electrostatic discharge (ESD) transients. Moreover, practically all Li-ion protector circuits for one- and two-cell applications have protector FETs in the low (unenthusiastic) surface of the battery. Plus key issues exacting to a low-side Li-ion protector circuit are converse. The transients shaped when the Li-ion protector opens throughout a brief short or when the battery is unplugged even as beneath load may exceed the voltage rating of semiconductors in the battery set. This theme describes a number of plan issues and suggests solutions to make your mind up or get better them. Resolution of these subjects requires attention to together the circuit design and the printed circuit board (PCB) explain. Classic Battery Circuit I. CLASSIC BATTERY CIRCUITRY FOR A LI-ION BATTERY PACK If we analyzed the Fig. 1 then we come to know that it is a block drawing of circuitry in a typical Li-ion battery set. It demonstrates an instance of a security protection circuit for the Li-ion cells and a gas gauge (capacity measuring device). The security circuitry includes a Li-ion protector that controls back-to-back FET switches. No doubt, these switches can be opened to defend the pack next to fault conditions such as in excess of voltage, beneath voltage, and over current. If we analyzed then we come to know that the figure also comprise a temperature responsive three-terminal fuse that will open due to long-drawn-out over present or over temperature, or it can be forced to open by superfluous protection circuitry in case there is a responsibility where the main protection circuitry fails to respond. As opening this fuse is a previous resort, as it will render the pack enduringly disabled. The gas-gauge circuitry events the charge and discharge present by measuring the voltage crossways a low-value sense resistor with low-offset dimension circuitry. Furthermore, the present measurement is incorporated to decide the alter in coulometric ability. In adding up, the gauge measures temperature plus voltage, assess gas-gauging algorithms to decide the obtainable capacity in the battery, and computes time-to-empty and additional values necessary by the host. The available capacity as well as additional measurements and computational outcome are communicated to the host over a sequential communication line. A diagram indication of obtainable ability can be displayed by the LEDs when make active by a push-button switch. Fig. 1. Block diagram of circuitry in a typical Li-ion battery pack. OPTIMIZING THE DESIGN FOR MEASUREMENT PRECISION Let's take a look upon measurement precision requires a precise measurement data gaining system and measurement sensor and also need a cautious board layout. Moreover, if the designer does not pay notice to all these items, the ensuing system performance may not transport the expected results. The sense resistor and how it is linked to the data gaining system are dangerous design decisions. The intelligence resistor may see changes in temperature that are much bigger than the ambient difference of the battery pack due to power debauchery in the resistor. Use of a low-temperature coefficient resistor will get better obtainable capacity and current-measurement precision. The effectual sense confrontation seen by the dimension circuitry may depend on how the printed circuit board (PCB) etch is linked to the sense resistor. If the intelligence resistor is linked in such a manner as to comprise a number of of the PCB etch confrontation in the actual sense resistance seen by the dimension circuitry, the effectual resistance is increased. In adding up to having a bigger resistance than planned, the portion of the effective sense resistance that is due to copper etch will have a extremely high temperature coefficient (0.39%/C). The most excellent practice is to attach the sense resistor into the circuitry at the site that includes the least amount of copper trace in the present path. If this technique is going after, there will be extremely little error due to the voltage drop crossways the link and the connection confrontation will not add to the effectual sense resistor worth (Tom Koppel, 2001, Pg. 56-80). If single-ended measurements are made on the voltage crossways the sense resistor, it is dangerous that the VSS of the measuring device be linked to the sense resistor with much care. In the solitary ended system, the measurement system earth provides one of the inputs for the dimension. Moreover, the value that is measured is the dissimilarity among the single-ended input and the measuring system ground. If the gauge system ground path has voltage dissimilarity among the on-chip ground and the ground end of the voltage dimension desired, this dissimilarity will make an error. The dimension system ground ought to tie to a low-current ground etch. The low-current ground ought to be alienated from the high-current ground, plus the ground end of the sense resistor ought to be the tie point where the low-current ground is tied to the high-current earth. This will also offer a more robust design for electrostatic discharge (ESD), as converse later. No doubt, Voltage measurements of the battery stack are also exaggerated by PCB layout and link drops. A few battery-pack designs may use nickel straps from the PCB link to the battery stack. Nickel is used since it is easy to weld to the battery cells, but its confrontation is five times as much as that of copper. When present flows from side to side these straps, the voltage deliberate by the circuitry on the PCB linked to these straps will not gauge the true cell voltage. To gauge the true cell voltage, divide voltage dimension connections ought to be made by means of wiring that does not carry the load present. This plummet may not be important, but if the circuitry actions every cell voltage, such drops will cause the top and/or base cells to gauge lower or higher (by means of discharge or charge currents) than the further cells. The similar issue exists for copper etch steering on the PCB. According to the mechanical experts a high-current-carrying conductor on the PCB will have a voltage drop crossways it. In universal, the voltage dimension connections require to be made so that these connections have extremely small current flowing during them among the desired measurement point and the input to the dimension IC. If the gas-gauge algorithm uses the lowest cell voltage for formative when the battery is unfilled, a minute voltage drop may stand for an important ability error and reason the gauge to report a lesser obtainable aptitude from the battery. If single-ended measurements are made of the voltage crosswise the sense resistor and also of the voltage, precision considerations state that the sense resistor ground association ought to be very close to the cell stack ground association (TechTarget 2003). Thermal Issues If we analyzed then we come to know that there can be a lot of power debauchery in the battery pack. There will be a number of temperature rise due to power debauchery in the cells. High currents can also create substantial heat from the protector FETs, sense resistor, and even etch and wiring confrontation. Make sure that proposed temperature measurements are not eminent due to nearness of the thermal sensor to a variety of heat sources. For instance, if the substrate temperature of an integrated circuit (IC) increase to the PCB is being measured, a narrow etch that runs under the IC may raise the account temperature by at least 6 with as small as 2 A flowing during the etch (Solidstate Controls, 2000). This is disastrous if the design is a NiMH or NiCd pack plus the temperature dimension is used to determine filled charge by a dT/dt charge extinction. An increase of charge current can reason a false discovery of a completely charged state due to an augmented dT/dt value. Extreme temperatures may also humiliate the measurement correctness of the gas gauge by causing drift in the on-chip orientation. A good design performance is to avoid placing any measurement part close to the heat sources for instance, the protector FETs and sense resistor. Transient Protection The majority designers will be familiar with the required to add transient defense across the pack output terminals if the battery is used to drive a motor or extremely inductive load. Though, lots of designs by means of non-inductive loads do not have any transient-limiting devices and depend only on a number of little capacitors to satisfy the transients. Li-ion cells have a comparatively high inductance for their size due to building techniques. If a battery pack is detached from the system as under load, there is an chance for a damaging transient to occur. No doubt, the battery pack be supposed to have enough capacitance to decrease transients or have something to fasten them. An even greater hazard exists if there is a brief short across the battery pack. Moreover, the Li-ion security guard may open to defend the cells from this short. If the FET switch in the guard opens rapidly, the L dI/dt transient may be extremely large. Furthermore, capacitance or transient-limiting plans on the production of the pack will not see this transient. The transient will come into view on the cell side of the guard. There is a possible to injure any components tied to the cell side of the guard if there is not enough capacitance or other means to satisfy the transient crossways the cell stack. Low-side protector issues Almost all one- and two-cell Li-ion guard are low-side protectors, where the guard FETs are located flanked by the unenthusiastic lead of the battery cell stack and the battery pessimistic terminal. There are more than a few issues that can upshot depending on where the designer decides to put in the protector FETs by means of respect to the battery-pack electronics. Moreover, circuitry in a battery pack, such as a gas gauge, wants to gauge the battery-cell stack voltage at the entire times. This drives the choice to put the Li-ion protector FETs among the ground association of the battery electronics and the unenthusiastic pack terminal. This choice generates two design issues that can live when the Li-ion protector FETs are open. Any communication among the host and the battery electronics may be dislocate when the protector FET opens. The additional grave issue involves protection. Practically every part of ICs will have an interior substrate diode from communication lines to the VSS ground association. This diode is part of the ESD protection arrangement in the machine. Different device will be secluded to 1.5 to 2 kV by this interior structure. Moreover, typical end-equipment stipulation will have an ESD obligation of 15 kV, requiring extra ESD defense components. The interior substrate diode and the outer ESD protection components may together give a return path for sneak accuse currents from a mount that fails in a high-voltage responsibility condition. Fig. 2 shows the path where the charge present may flow. Moreover, if the charger voltage goes beyond the highvoltage trip threshold of the guard by more than one diode drop, the IC substrate diode will be forward-biased, plus accuse present can flow whenever the host drives the message line to a reason zero. Resistance in the message line will boundary the peak present flow, and the responsibility cycle of a logic low on the communication line will have an effect on the average present flow (Staff and Engineering Information Administration, 2004, Pg. 100-150). Fig. 2. Sneak charge-current path from a highvoltage charger failure. Design Circuit Input: 12V DC Output: 90V DC, 10mA Circuit Features No Design necessary It will operate at Supply Voltages from 1V to 30V It put away Only 95mA Supply Current workings in Step-Up or Step-Down Mode just Three outer Off-the-Shelf Components Required Low-Battery Detector Comparator On-Chip User-Adjustable present Limit Interior 1A Power Switch Fixed or Adjustable production Voltage Versions It also use Space-Saving 8-Pin PDIP or SO-8 Package Circuit Applications Pagers Cameras Single-Cell to 5V Converters Battery Backup Supplies Laptop and Palmtop Computers Cellular Telephones Portable Instruments Battery-Powered a, b, and g Particle Detectors Circuit Description According to the expert analysis the LT1073 is a flexible micro power DC/DC converter. The device needs only three outside components to deliver a fixed production of 5V or 12V. The very low smallest amount supply voltage of 1V allows the use of the LT1073 in applications where the main power source is a solitary cell. An on-chip supplementary gain block can purpose as a low-battery detector or linear post-regulator. Standard current drain of the LT1073-5 used as exposed in the Typical Application circuit underneath is just 135mA unpack, making it ideal for applications where extended battery life is significant. The circuit exposed can deliver 5V at 40mA from an input as low as 1.25V plus 5V at 10mA from a 1V input. Moreover, the device can with no trouble be configured as a step-up or step down converter, though for most step-down applications or input sources better than 3V, the LT1173 is optional. Switch present limiting is user-adjustable by adding a single outside resistor. Sole overturn battery protection circuitry restrictions reverse current to secure, nondestructive levels at reverse supply voltages up to 1.6V. Typical Applications Single-Cell to 5V Converter Single Alkaline "AA" Cell Operating Hours vs DC Load Current Pin Functions in designed Circuits ILIM (Pin 1): Attach this pin to VIN for usual use. Where lower current boundary is desired, attach a resistor among ILIM and VIN. A 220W resistor wills boundary the switch existing to about 400mA. VIN (Pin 2): Input Supply Voltage require for this designed battery circuit SW1 (Pin 3): Collector of Power Transistor. For step-up mode attach to inductor/diode. For step-down mode attach to VIN. SW2 (Pin 4): Emitter of Power Transistor. For step-up mode attach to ground. For step-down mode join to inductor/diode. This pin have to never be allowed to go additional than a Schottky diode drop underneath ground. GND (Pin 5): Ground. AO (Pin 6): Secondary Gain Block (GB) Output. Open antenna, can sink 100mA. SET (Pin 7): GB Input. GB is an op amp by means of optimistic input linked to SET pin and harmful input linked to 212mV reference. FB/SENSE (Pin 8): On the LT1073 (flexible) this pin goes to the comparator input. On the LT1073-5 and LT1073-12, this pin goes to the interior application resistor that sets output voltage (Sunggyu Lee, 2006. Pg. 10-78). Block Diagrams Measuring Input Current at Zero or Light Load In this battery circuit get hold of significant numbers for quiet current and competence at low output current involves sympathetic how the LT1073 operates. At extremely low or zero load current, the machine is inactive for seconds at a time. When the output voltage falls sufficient to trip the comparator, the power switch comes on for a small number of cycles until the output voltage rises adequately to conquer the comparator hysteretic. When the power switch is on, inductor current builds up to hundreds of mill amperes. Normal digital multi meters are not able of measuring standard current since of bandwidth and dynamic range limitations. Conclusion To sum up this discussion we may say that battery-circuit design and design are significantly more dangerous than might be expected. The combination of battery requirements includes: high-amplitude ESD to connector pins and exposed surfaces, coupling from an ESD occasion to near etch and components, serious load currents, plugging and unplugging by means of power on the connector pins, manifold circuit ground references counting high-current grounds, dimension of very minute signals, and thermal management. The key to a victorious design is the credits of the variety of issues prior to starting the plan and a close manage of the PCB explain by the design wangle. A good plan is a layered approach; take away any one layer will decrease the efficiency of the others (Frances S. Sterrett, 2004, Pg. 156-168). References Frances S. Sterrett, " Alternative Fuels and the Environment", New York, "CRC Press", October 2004, Pg. 156-168. Sunggyu Lee. " Alternative Fuels", New York, New York, Francis, Inc. September 2006. Pg. 10-78. Staff and Engineering Information Administration, "Society of Automotive Engineer", New York, US Govt. Printing Office, July 2004. Pg. 100-150. Solidstate Controls, Inc. (2000). Uninterruptible Power Supply (UPS) Planning and Installation Guide. Retrieved August 22, 2004 from http://www.sciups.com/techhpapers/papers/planninginstall.html TechTarget. (2003). uninterruptible power supply. Retrieved August 20, 2004 from http://whatis.techtarget.com/definition/0,,sid9_gci214161,00.html Tom Koppel, "Powering the Future", Chicago, Willey, John & Sons, Inc. May2001. Pg. 56-80. T. K. Garrett. "Alternative Fuels and Fuel Systems", Los Angeles, CA, Society of Automotive Engineer, Sept. 2003. Pg. 98-100. Read More