Digital battery

Lithium-ion battery circuit protection includes over-load protection, more protection against overcurrent / short circuit and over-discharge protection, and requires great precision charging protection, protection IC with low power consumption electric volt high-voltage and zero batteries and other features. This paper describes the principle of the three protection circuits, new functions and features required.

 

In recent years, PDAs, digital cameras, cell phones, portable audio devices and Bluetooth products get more and more use of lithium batteries as main power. Li-ion Laptop battery has a small size, high energy density, no memory effect, the high cycle life, high-voltage batteries and the advantages of low self-discharge rate, and nickel-cadmium batteries in nickel metal hydride are not the same lithium batteries must consider the charge and discharge of security so as to prevent deterioration characteristic. To overload the lithium battery, over discharge, over current protection and short-circuit is very important is usually the design of the battery circuit protection to protect Li-ion battery.

 

Because lithium high energy density-ion battery, it is difficult to ensure the safety of the battery. In the most charged, the battery temperature increases after the excess energy, so the decomposition of the electrolyte produced gas because of the internal pressure of the danger arising from the spontaneous combustion or broken on the contrary, over-discharge state, due to the decomposition of the electrolyte causing the Dell Inspiron 5150 battery characteristics and the degradation of sustainability, thus reducing the number of charge cycles.

 

Lithium-ion battery circuit protection is to ensure that this excess charge and discharge state of security and to prevent deterioration characteristic. Lithium-ion battery circuit protection is protected by the CI and structure of two power MOSFETs, including the protection IC for monitoring the battery voltage when there is excessive charges and the discharge state to pass the order to fill the power MOSFET to protect the battery, protect the functions of the IC during the load protection, over-discharge protection and protection against overcurrent / short circuit.

 

1, an overload protection

 

The principle of over-charge protection IC as follows: When an external charger for lithium battery, when, to avoid a temperature rise caused by increased internal pressure must end the state of load. At this stage, the need to test the hp 417066-001 battery voltage to protect IC when the time comes to 4.25V (assuming that the point of overcharging 4.25V) which activate the over-load protection, the MOSFET power to cut through the opening and closing the load.

 

In addition, attention must also be the result of excessive noise generated by the perception of dysfunction detected if determined to be overload protection. Therefore, the need to adjust the delay and time delay can be shorter than the noise.

 

2, over-discharge protection

 

In the case of excessive discharge, the decomposition of the electrolyte in case of damage caused by the characteristics of the battery and cause a reduction in the number of charge cycles. Protection of lithium-IC with on-rejection phenomenon can be avoided to protect the battery.

 

Over-the principle of discharge protection IC: To avoid excessive sony VGP-BPS2A battery status at discharge, assuming that the lithium battery connected to the load when the voltage of the lithium battery is less than the highest - point of discharge voltage detection (assumed to be 2.3V) will activate the over-discharge protection, so that the power MOSFET transition from open-cut and the threshold of discharge, to avoid battery-phenomenon discharge, and keep the battery low quiescent current in standby mode, yet current 0.1μA.

 

When the lithium battery is connected to the charger and the battery voltage lithium is greater than this period of excessive discharge voltage, over-discharge protection is lifted. In addition, taking into account the conditions of discharge pulse, excessive discharge detection circuit with time delay to prevent malfunction.

 

3, the current and short-circuit current

 

For unknown reasons (discharge or negative by metallic objects inadvertently) caused by over-current circuit or short to ensure security, you should immediately cease its discharge.

 

Terms runway Principles of protection against overcurrent IC, when the discharge toshiba PA3399U-1BAS battery current is too large or too short occurs, the protection IC is turned off (short circuit) current protection, over current detection at the moment is to power MOSFET’s Rds (on) as a sensor monitoring the impedance voltage drop in the case, if the ratio set by the voltage-current detection is higher when the discharge stopped, the formula is:

V = I × Rds (on) × 2 (V-for over-current detection voltage, I is discharge current)

Suppose V = 0.2V, Rds () = 25mΩ, and protect the current size of I = 4A on

Similarly, too much time current detection delay should also be provided to prevent current flow generated when there are unexpected failures.

Usually, after the election of overheating if they can remove the excess current factors (such as the charge immediately and out) will resume its normal state, may proceed with the normal load, the discharge action.

 

4 new protection features of the lithium-IC’s

 

In addition to the protection feature of the lithium IC attention the following new battery features is also interesting:

a. Charging over-current protection

When connecting the charger suddenly aware (as the charger is damaged), on-circuit current detection immediately, this time from top to bottom Court, the MOSFET power to cut the open position for protection.

V = I × Rds () × 2

(I is the load current; Vdet4 on voltage-current detection, Vdet4 to-0.1V)

 

b. Overcharge when the lock mode

Usually protect the IC in the over-charging protection will be after a period of delay time, and then it will cut the power MOSFETs to achieve the goal of protection when the battery voltage lithium dropped in points Lifting (hysteresis voltage overload), when it will resume once again continue to impose protection →Discharge charge discharge. Security issues in this state will not be able to get an effective solution, lithium batteries will always repeat the charge discharge →Action load discharge gate MOSFET power will be repeated alternately at high and low voltage state, which could make the MOSFET heater but it also reduces the battery life, if the lock mode is very important. If the circuit of the lithium battery protection detects over-protection mode load locked, IC will not get hot, and the relative security has improved considerably.

In the over-load protection, simply plug the battery charger, the charging time will be entered into lock mode. At this stage, even if the voltage drops of the lithium battery can not produce the recharge of the situation, remove and connect to load and unload the load can be restored condition.

 

c. Reduce the size of the circuit protection component

Will overload and short circuit protection with an integrated capacitor delay for the protection of the IC inside to reduce the size of circuit protection components?

 

5, the protection requirements of IC performance

 

a. Overload protection, high accuracy

When the lithium-ion battery charging excessive state to avoid a temperature rise caused by increased internal pressure required for the threshold state of charge. Protection IC detects the cbattery voltage, when the overcharge is detected, then detection of over-charging power MOSFETs in order to cut the load threshold. At this point should be noted that over-voltage detection burden of high precision, battery charging, battery to a state is a danger of the user, taking into account security issues and should enable the voltage when the threshold state of charge. To simultaneously satisfy these two conditions, there must be a detector of high precision, accuracy of 25mV current detector, the accuracy will be improved.

 

b. In order to reduce IC power consumption to protect

With the increasing use of time was enough lithium power-voltage ion battery will gradually diminish the value of the last low specifications below, this time need to recharge. If you do not charge for continued use, may lead to excessive battery discharge Ershi is not used. To avoid too much discharge protection IC to detect the battery voltage, over-voltage detection of the landfill once they reach the following, you must cut the discharge of MOSFET power and the threshold discharge. But this time, the BATCL50L battery itself, there are still protecting the natural discharge and IC current consumption exist, therefore the need to protect the IC power consumption to a minimum.

 

c. Protection against overcurrent / short-circuit the need for low-voltage detection and precision requirements

Short circuits due to unknown causes must immediately stop selling them. Over-current detection is based on power MOSFET RDS (on) for the impedance of induction to follow the voltage drop of blood at the time when compared with a voltage-current detection is also high at namely, to stop selling them. To MOSFET’s Rds (on) in the current charge and discharge current is the effective use of time is needed for the impedance as low as possible, at present the impedance is approximately 20mΩ ~ 30mΩ, if the voltage-current detection may be lower.

 

d. Resistant to high voltage

Battery and charger to connect the instant the pressure will be generated if the protection must meet the requirements of high voltage IC.

 

e. Low VGP-BPS2B battery consumption

In the protection of the state, its current consumption of 0.1μA rest must be small.

 

f. Zero-Volt Rechargeable

Some batteries may be stored in the process because it takes too long or unusual causes of tension as low as 0V, and therefore need to protect the IC can be achieved when 0V load.

 

6, the protection IC Prospect

 

As mentioned previously, the future protection of integrated circuits should further enhance the detection voltage accuracy and reduce current consumption to protect and improve the CI function to prevent malfunctions and so on, and the charger to connect the terminal High voltage is also the focus of research and development. In the package, at present has been a gradual shift SOT23-6 package SON6 the future, there are CSP package, even COB products to meet the requirements highlighted in a word, light.

 

In functions, protect the IC does not require integration of all functions, according to different materials, to develop a single lithium Dell Latitude D830 battery protection IC, the coverage only if overloaded or over-discharge protection, which can significantly reduce the cost and size.

 

Of course, the functional components is a single crystal of the same goals, such as manufacturers of mobile phones today have been directed towards protecting the IC, charging circuit and power management IC, and other peripheral circuits and logic is a two chip chipset, but rather of power MOSFET’s open reduction of impedance of the circuit is difficult to integrate with other IC, even if it is made of a special single-chip technology, I fear the cost is too high. Therefore, protection of single crystal integrated circuits should take some time to resolve.