no 5 alkaline battery

　　no 5 alkaline battery protection board circuit

　　no 5 alkaline battery protection board, 16-cell lithium iron phosphate battery protection board, 18650 battery protection board, circuit board manufacturers will give priority to the working principle of lithium battery protection board when designing double-sided circuit boards. Battery City will show you a single power-saving board The principle of lithium battery protection board of core is hoped to be able to draw inferences from one instance to other cases.

　　The circuit and parameters of the lithium battery protection board vary depending on the IC used, voltage, etc. The following is a distribution of DW01 with MOS tube 8205A, including the normal working behavior of its lithium battery protection board.

　　1. Working principle of lithium battery protection board

　　When the cell voltage is between 2.5V and 4.3V, pins 1 and 3 of DW01 both output high level (equal to the supply voltage), and the voltage of the second pin is 0V. At this time, the voltage of pins 1 and 3 of DW01 will be added to pins 5 and 4 of 8205A respectively. The two electronic switches in 8205A are in a conductive state because their G pole is connected to the voltage from DW01, that is, Both electronic switches are on. At this time, the negative electrode of the battery core is directly connected to the p-terminal of the protective plate, and the protective plate has a voltage output.

　　2. Protection board over-discharge protection control principle

　　When the battery core is discharged through an external load, the voltage of the battery core will slowly decrease. At the same time, DW01 will internally monitor the battery core voltage in real time through the R1 resistor. When the battery core voltage drops to about 2.3V, DW01 will consider that the battery core voltage has been exhausted. In the over-discharge voltage state, the output voltage of pin 1 is immediately disconnected, causing the voltage of pin 1 to become 0V. The switch tube in 8205A is turned off because pin 5 has no voltage. At this time, the B- of the battery core and the P- of the protection plate are disconnected. That is, the discharge circuit of the battery core is cut off and the battery core will stop discharging. The protection board is in an over-discharge state and remains so. After the p and p- of the protection board are indirectly connected to the charging voltage, DW01 immediately stops the over-discharge state after detecting the charging voltage through B-, and outputs a high voltage on pin 1 again, turning on the over-discharge control tube in the 8205A. That is, the B- of the battery core and the P- of the protection board are reconnected, and the battery core is charged directly by the charger.

　　3. Protection board overcharge protection control principle

　　When the battery is charged normally through the charger, as the charging time increases, the voltage of the cell will become higher and higher. When the cell voltage rises to 4.4V, DW01 will consider that the cell voltage is in an overcharge voltage state. The output voltage of pin 3 is immediately cut off, so that the voltage of pin 3 becomes 0V, and the switch tube in 8205A is turned off because pin 4 has no voltage. At this time, the B- of the battery core and the P- of the protection plate are disconnected. That is, the charging circuit of the battery core is cut off and the battery core will stop charging. The protection board is in an overcharged state and remains so. After the p and p- of the protection board are indirectly connected to the discharge load, although the overcharge control switch is turned off, the forward direction of the diode inside is the same as the direction of the discharge circuit, so the discharge circuit can discharge. When the voltage of the cell When it is placed below 4.3V, DW01 stops the overcharge protection state and outputs high voltage at pin 3 again, causing the overcharge control tube in the 8205A to conduct, that is, the B- of the battery core and the protection board P- are reconnected. , the battery core can charge and discharge normally.

　　4. Protection board short circuit protection control principle

　　During the process of external discharge of the protection board, the two electronic switches in the 8205A are not completely equivalent to the two mechanical switches, but are equivalent to two resistors with very small resistance, and are called the conduction internal resistance of the 8205A. The on-resistance of each switch is about 30mU03a9 and the total is about 60mU03a9. The voltage applied to the G electrode actually directly controls the on-resistance of each switch tube. When the G-electrode voltage is greater than 1V, the conduction resistance of the switch tube is The internal resistance of the switch is very small (tens of milliohms), which is equivalent to the switch being closed. When the G electrode voltage is less than 0.7V, the internal resistance of the switch tube is very large (several M), which is equivalent to the switch being opened. Voltage UA is the voltage generated by the on-resistance of 8205A and the discharge current. As the load current increases, UA will inevitably increase. Because UA0.006LIUA is also called the tube voltage drop of 8205A, UA can simply indicate the size of the discharge current. When it rises to 0.2V, it is considered that the load current has reached the limit value, so the output voltage of pin 1 is stopped, so that the voltage of pin 1 becomes 0V. The discharge control tube in 8205A is closed, cutting off the discharge circuit of the battery core, and turning off the battery. Discharge control tube. In other words, the maximum output current allowed by DW01 is 3.3A, achieving over-current protection.

　　5. Lithium battery protection board overcurrent protection

　　During the normal discharge process of the battery to the load, when the discharge current passes through two MOSFETs connected in series, due to the on-resistance of the MOSFETs, a voltage will be generated at both ends. The voltage value U=I*RDS*2, RDS is a single MOSFET conduction resistance, the V- pin on the control IC detects the voltage value. If the load is abnormal for some reason, the loop current increases. When the loop current is large enough to make U》0.1V (this value is determined by the control IC (determined (different ICs have different values)), its DO pin will change from high voltage to zero voltage, causing T2 to turn from on to off, thereby cutting off the discharge circuit, making the current in the circuit zero, and causing overcurrent. Protective effects.

　　It is found that there is also a delay time between the control IC detecting the occurrence of overcurrent and sending the shutdown T2 signal. The length of this delay time is determined by C2, usually about 13 milliseconds, to avoid misjudgment caused by interference. From the above control process, it can be seen that the overcurrent detection value not only depends on the control value of the control IC, but also depends on the on-resistance of the MOSFET. When the on-resistance of the MOSFET is larger, for the same control IC, the over-current protection The smaller the value.

　　6. Short circuit protection control process

　　Short-circuit protection is an extreme form of over-current protection. Its control process and principle are the same as over-current protection. The short-circuit is equivalent to adding a small resistor (about 0) between pp- to increase the load of the protection board. When the current reaches more than 10A instantaneously, the protection board immediately performs overcurrent protection.

　　Lithium battery charging circuit principle and application

　　Lithium-ion batteries are widely used in mobile phones, camcorders, laptops, cordless phones, power tools, remote control or electric toys, cameras and other portable electronic devices due to their excellent characteristics.

　　1. Lithium batteries and nickel-cadmium and nickel-metal hydride rechargeable batteries:

　　The negative electrode of a lithium-ion battery is graphite crystal, and the positive electrode is usually lithium dioxide. During charging, lithium ions move from the positive electrode to the negative electrode and are embedded in the graphite layer. During discharge, lithium ions detach from the surface of the negative electrode in the graphite crystal and move toward the positive electrode. Therefore, during the charging and discharging process of the battery, lithium always appears in the form of lithium ions, not in the form of metallic lithium. Therefore, this kind of battery is called a lithium-ion battery, or lithium battery for short.

　　Lithium batteries have the advantages of small size, large capacity, light weight, no pollution, high single cell voltage, low self-discharge rate, and high number of battery cycles, but they are more expensive. Nickel-cadmium batteries are being gradually phased out due to their low capacity, serious self-discharge, and environmental pollution. Nickel metal hydride batteries have a high cost performance and do not pollute the environment, but the cell voltage is only 1.2V, so their range of use is limited.

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