A linear controller for charging lithium batteries

Abstract

The application discloses a linear controller for charging a lithium battery, and relates to the field of battery charging, which comprises a logic control circuit and a first comparator, wherein a four-to-two signal gate is designed in the logic control circuit, first voltage, second voltage, battery detection voltage and current setting voltage are input into the four-to-two signal gate respectively, the output end of the logic control circuit is connected with the first comparator and an output charging enable signal respectively, the output end of the first comparator is feedback connected with the logic control circuit, the logic control circuit inputs the current setting voltage and the second voltage into the first comparator when the lithium battery is in a charging stage, and the output signal of the first comparator is feedback connected with the logic control circuit after the lithium battery is charged, the four-to-two signal gate in the logic control circuit selects the battery detection voltage and the first voltage, the voltage of a BAT pin is detected, and the charging function is started.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery charging, in particular to a linear controller for charging lithium battery. BACKGROUND

[0002] With the increasing demand for the safety of electronic device charging, the battery charging technology has made a great progress in recent years, and achieved a leap-forward development. Figure 1 、 Figure 2 As shown in the prior art, the linear controller for charging lithium battery generally adopts three-stage principle to control the charging of lithium battery, i.e. trickle charging ITRICK, constant current charging ICC and constant voltage charging ICV, and when the controller considers that the battery is fully charged, it will remind the user through display means. In the prior art, after the lithium battery is charged to the constant voltage stage, the controller starts to control the charging current to linearly decrease with the increase of the battery voltage, and when the controller detects that the charging current decreases to 10% of the constant current stage current, i.e. 10% ICC, it will control the LED connected to the periphery to change (at this time, if the battery voltage is 4.20V, the LED is off), and remind the user that the electronic device is fully charged. However, in this way, the charging loop of the linear controller is not completely closed, and there is still a small current for charging. If the user does not take it off in time, the electronic device will continue to be charged, and the battery voltage will continue to rise. In normal circumstances, when the battery voltage continues to rise by a small voltage value, there will be no charging current (e.g. 4.21V), i.e. the charging is truly stopped. Because the controller or the battery will have parameter deviation during manufacturing or after use, this control method will cause overcharging of the battery, affect the service life of the battery, and even cause explosion of the battery. SUMMARY

[0003] In view of the above problems existing in the current battery charging field, the present application provides a linear controller for charging lithium battery, which can ensure that the battery stops charging after being fully charged, thereby improving the full charging voltage precision of the battery and ensuring the safety of battery charging.

[0004] To achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

[0005] A linear controller for charging lithium battery, comprising a charging main loop, a lithium battery, a current setting resistor and a charging indicator light, provided with a BAT pin and an ISET pin, the charging main loop is connected with a logic control circuit and the current setting resistor respectively, further comprising a logic control circuit and a first comparator, the logic control circuit is internally designed with a four-to-two signal gate, inputting a first voltage, a second voltage, a battery detection voltage and a current setting voltage respectively, the output end of the logic control circuit is connected with the first comparator and outputs a charging enable signal, the output end of the first comparator is feedback connected back to the logic control circuit, when the lithium battery is in the charging stage, the logic control circuit inputs the current setting voltage and the second voltage to the first comparator; after the lithium battery is fully charged, the output signal of the first comparator is feedback connected back to the logic control circuit, controlling the four-to-two signal gate in the logic control circuit to select the battery detection voltage and the first voltage, and performing BAT pin voltage detection and starting the charging function.

[0006] According to an aspect of the present application, the charging main loop comprises a second comparator, a second gate, a first amplifier, a second amplifier, a third amplifier, a first PMOS tube and a second PMOS tube, the second PMOS tube is a charging PMOS tube, and the size is set to be multiple times of the first PMOS tube, the first PMOS tube and the second PMOS tube are mirror connected, the sources are connected with VIN, the gates are connected with the output ends of the second amplifier and the third amplifier, and the drains are connected with the input end of the first amplifier.

[0007] According to an aspect of the present application, a third PMOS tube and a fourth PMOS tube are further provided, the output end of the first amplifier is connected with the gate of the third PMOS tube, and controls the opening degree of the third PMOS tube, the source of the third PMOS tube is connected with the drain of the first PMOS tube, and the drain of the third PMOS tube is connected with the ISET pin; the source of the fourth PMOS tube is connected with VIN, the gate is connected with the charging enable signal, and the drain is connected with the output ends of the second amplifier and the third amplifier.

[0008] According to an aspect of the present application, the second amplifier is a constant current control module, the negative input end is connected with the second gate, and the positive input end is connected with the ISET pin, the second amplifier inputs a first reference voltage and the ISET pin voltage, and the ISET pin voltage is clamped at a fixed size by setting the size of the first reference voltage.

[0009] According to an aspect of the present application, the output end of the second comparator is connected with the input end of the second gate, the input end of the second comparator is connected with a battery detection voltage and a second reference voltage, and the second comparator is used for detecting the BAT pin voltage, and controls the size of the first reference voltage output by the second gate, so that the charging main loop is in a trickle charging mode or a constant current charging mode.

[0010] According to one aspect of the present application, the input end of the third amplifier is connected to the battery detection voltage and the third reference voltage, when the lithium battery voltage approaches the full charge voltage, the main charging loop enters the constant voltage charging mode, and the third amplifier controls the linear decrease of the charging current.

[0011] According to one aspect of the present application, the first resistor has one end connected to the negative input end of the third amplifier, and the other end connected to the second resistor, the third resistor, the fourth resistor and the ground in sequence, and the connection point of the first resistor and the second resistor is connected to the logic control circuit, the connection point of the second resistor and the third resistor is connected to the second gate, and the connection point of the third resistor and the fourth resistor is connected to the logic control circuit.

[0012] According to one aspect of the present application, the first voltage dividing resistor has one end connected to the positive electrode of the lithium battery through the BAT pin, and the other end connected to the second voltage dividing resistor, and the second voltage dividing resistor is connected to the ground.

[0013] According to one aspect of the present application, the fifth resistor and the first NMOS transistor are further provided, one end of the charging indicator lamp is connected to the VIN, the other end is connected to the fifth resistor, the other end of the fifth resistor is connected to the source of the first NMOS transistor, the gate of the first NMOS transistor is connected to the logic control circuit, and the drain is connected to the ground.

[0014] According to one aspect of the present application, when the lithium battery voltage approaches the full charge voltage, the voltage of the ISET pin decreases with the decrease of the charging current, the output signal of the first comparator is set to high, the charging enable signal output by the logic control circuit is set to low, and the signal input to the first comparator is changed, so that the lithium battery stops charging; when the voltage of the BAT pin decreases to the recharge threshold voltage, the output voltage of the first comparator is set from low to high, the charging enable signal output by the logic control circuit is set from low to high, and the lithium battery starts charging again.

[0015] The embodiment of the present application has the advantages that: the logic control circuit is internally designed with a four-to-two signal gate, and the first voltage, the second voltage, the battery detection voltage and the current setting voltage are input respectively; the output end of the logic control circuit is connected with the first comparator and the output charging enable signal respectively; the output end of the first comparator is feedback connected back to the logic control circuit; when the lithium battery is in the charging stage, the logic control circuit inputs the current setting voltage and the second voltage to the first comparator; after the lithium battery charging is completed, the output signal of the first comparator is feedback connected back to the logic control circuit, and the four-to-two signal gate in the logic control circuit selects the battery detection voltage and the first voltage to detect the BAT pin voltage and start the charging function, so that the charging can be stopped after the battery is fully charged, the full charging voltage precision of the battery is improved, and the safety of the battery charging is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort.

[0017] Figure 1 A circuit structure diagram of a prior art linear controller for lithium battery charging according to the present application;

[0018] Figure 2 A charging state diagram of a prior art linear controller for lithium battery charging according to the present application;

[0019] Figure 3 A circuit structure diagram of a linear controller for lithium battery charging according to the present application;

[0020] Figure 4 A charging state diagram of a linear controller for lithium battery charging according to the present application. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present application.

[0022] Embodiment one:

[0023] As Figure 3As shown, a linear controller for lithium battery charging includes a charging main loop, a lithium battery, a current setting resistor RISET, a charging indicator light, a logic control circuit and a first comparator, in this embodiment, the first comparator is set as an ITERM comparator, and the linear controller for lithium battery charging in the application is set as a chip, including a BAT pin and an ISET pin, the charging main loop is connected with the logic control circuit, the current setting resistor and the lithium battery respectively.

[0024] The logic control circuit is internally designed with a four-to-two signal gate, which respectively inputs a first voltage, a second voltage, a BAT_sense voltage and an ISET voltage, in this embodiment, the first voltage is set as 1.0125V, and the second voltage is set as 0.1V. The output end of the logic control circuit is connected with the ITERM comparator and an output charging enable signal ENCHRG respectively, and the output end of the ITERM comparator is fed back to the logic control circuit. When in the charging stage, the four-to-two signal gate selects the ISET voltage and the 0.1V voltage, that is, the input signal of the ITERM comparator at this time is the ISET voltage and the 0.1V. After the charging is completed, the output signal of the ITERM comparator is fed back to the logic control circuit to control the four-to-two signal gate in the logic control circuit to select the BAT_sense voltage and the 1.0125V voltage, so as to detect the voltage of the BAT pin and prepare to start the recharging function.

[0025] The charging main loop includes a second comparator, a second gate, a first amplifier, a second amplifier, a third amplifier, a first PMOS tube, a second PMOS tube, a third PMOS tube, a fourth PMOS tube, a first NMOS tube and a resistor group, in this embodiment, the second comparator is set as a TRICKL comparator, the first amplifier is set as an operational amplifier MA, the second amplifier is set as an operational amplifier CA, the third amplifier is set as an operational amplifier VA, the first PMOS tube is set as P_sense, the second PMOS tube is set as P_charge, the third PMOS tube is set as P0, the fourth PMOS tube is set as P_pull, and the first NMOS tube is set as Q0. The resistor group includes a first voltage dividing resistor R1, a second voltage dividing resistor R2, a first resistor R3, a second resistor R4, a third resistor R5, a fourth resistor R6 and a fifth resistor R0.

[0026] P_charge is a charging PMOS tube, the size of which is m times that of P_sense, and in the present embodiment, m is set to 1000, and the two tubes are mirror-connected. The sources of P_sense and P_charge are both connected to VIN, the gates are connected to each other and to the output terminals of operational amplifier VA and operational amplifier CA, that is, the same VGS voltage is achieved, so as to set the mirror current Isense of P_charge, and the charging current IBAT is controlled by the mirror. The drain of P_sense is connected to the negative input terminal of operational amplifier MA, and the drain of P_charge is connected to the positive input terminal of operational amplifier MA, and the virtual short and virtual open principle of the operational amplifier is used to clamp the drain voltages of P_sense and P_charge at the same value, so as to ensure that the VDS of P_sense and P_charge is the same, and the precise matching of P_sense and P_charge is achieved, and the precision of the charging current is ensured. The output terminal of operational amplifier MA is connected to the gate of P0, and controls the opening degree of P0, so as to adjust the internal resistance of the mirror current Isense current source, and prevent overcharging during starting. The source of P0 is connected to the drain of P_sense, and the drain of P0 is connected to the ISET pin. The ISET pin is connected to a current setting resistor RISET, and the other end of the current setting resistor RISET is connected to ground. The current setting resistor RISET is used to set the Isense current, that is , in the present embodiment, VISET = 1V, RISET = 1KΩ, and Isense = 1mA is set, and because m = 1000, the charging current IBAT = 1A. The source of P_pull is connected to VIN, the gate is connected to a charging enable signal, and the drain is connected to the output terminals of operational amplifier CA and operational amplifier VA.

[0027] Operational amplifier CA is a constant current control module, the positive input terminal is connected to the drain of P0 and the ISET voltage, the negative input terminal is connected to the second gate and the reference voltage VRCC, and the charging enable signal ENCHRG is also connected, and the output terminal of operational amplifier CA is connected to the gates of P_sense and P_charge. If the reference voltage VRCC is 1V, the VISET voltage is clamped at 1V, and a stable Isense current of 1mA is achieved; if the reference voltage VRCC is 0.1V, the VISET voltage is clamped at 0.1V, and a stable Isense current of 0.1mA is achieved.

[0028] The positive input terminal of the TRICKL comparator is connected to the battery detection voltage BAT_sense, and the negative input terminal is connected to the second reference voltage, which is set to 0.7V in this embodiment. The output terminal of the TRICKL comparator is connected to the input terminal of the second gate. The TRICKL comparator is used to detect the voltage of the BAT pin. If the voltage of the BAT pin is charged to 2.8V, the reference voltage VRCC output by the second gate is 0.1V, i.e. trickle charging. If the voltage of the BAT pin is charged to 2.8V, the reference voltage VRCC output by the second gate is 1V, i.e. constant current charging.

[0029] The positive input terminal of the operational amplifier VA is connected to the battery detection voltage BAT_sense, and the negative input terminal is connected to the third reference voltage, which is set to 1.05V in this embodiment. The output terminal of the operational amplifier VA is connected to the gates of P_sense and P_charge. When the voltage of the lithium battery approaches the full charge voltage VF, the constant voltage stage is entered, and the charging current is controlled to linearly decrease until the full charge is turned off.

[0030] One end of the first voltage dividing resistor is connected to the positive electrode of the lithium battery, and the other end is connected to the positive input terminal of the operational amplifier VA, the logic control circuit and the second voltage dividing resistor, respectively. The other end of the second voltage dividing resistor is connected to the ground.

[0031] One end of the resistor R3 is connected to the negative input terminal of the operational amplifier VA and connected to the third reference voltage. The other end of the resistor R3 is connected to R4, R5 and R6 in sequence and connected to the ground. The connection point of the resistors R3 and R4 is connected to the logic control circuit and outputs a voltage of 1.0125V. The connection point of the resistors R4 and R5 is connected to the second gate and outputs a voltage of 1.0V. The connection point of the resistors R5 and R6 is connected to the logic control circuit and outputs a voltage of 0.1V.

[0032] One end of the charging indicator lamp is connected to VIN, and the other end is connected to the resistor R0. The other end of the resistor R0 is connected to the source of the first NMOS transistor Q0. The drain of the first NMOS transistor Q0 is connected to the ground, and the gate is connected to the logic control circuit.

[0033] As Figure 4As shown, when the VIN voltage rises above a certain threshold level, which is set to 3.6V in this embodiment, a charging cycle begins when a 1% precision setting resistor is connected between the ISET pin and the ground, and when the lithium battery is connected to the BAT pin. When the voltage of the BAT pin is lower than a set value, which is set to 2.8V in this embodiment, the main charging loop enters the trickle charging mode, and at this time, the lithium battery voltage is raised to a safe level by using a 10% ICC charging current. When the voltage of the BAT pin rises above 2.8V, the main charging loop enters the constant current charging, and at this time, a constant charging current ICC is provided to the lithium battery. When the voltage of the BAT pin approaches the final full charging voltage, the main charging loop enters the constant voltage charging mode.

[0034] When the charging system enters the constant voltage charging, as the lithium battery voltage rises, the output voltage of the operational amplifier VA gradually rises, that is, the gate voltages of P_sense and P_charge gradually rise, showing a closing trend, and the charging current gradually decreases. When the battery voltage approaches the full charging voltage VF, which is set to 4.2V in this embodiment, as the charging current decreases, the voltage VISET also decreases, and the voltage drop of RISET also decreases to 10% VISET, at this time , the ITERM comparator input end is connected to the ISET voltage and 0.1V, and it is detected that VISET < 0.1V, and the output of the ITERM comparator is high, which is connected to an input end of the logic control circuit. The logic control circuit will judge that the battery is full according to the charging state, and output the charging enable signal ENCHRG to be low, turn off the operational amplifier VA, the operational amplifier CA, the operational amplifier MA and Q0, stop charging, and turn off the charging indicator light. The signal at the input end of the ITERM comparator is switched to the BAT_sense voltage and 1.0125V, and the BAT pin voltage detection is started at this time. At this time, the ITERM comparator plays the role of the comparator RECHRG. As the battery voltage decreases, when the voltage of the BAT pin decreases to the recharge threshold voltage VRE, which is set to 4.05V in this embodiment, the output signal of the ITERM comparator is changed from high to low, and the logic control circuit changes the output charging enable signal ENCHRG from low to high, thereby starting the operational amplifier VA, the operational amplifier CA, the operational amplifier MA and Q0, and the lithium battery starts charging again. The charging indicator light is started, so as to realize the charging cycle, and the full charging voltage is accurately controlled at the VF voltage value 4.2V.

[0035] The application has the advantages that the logic control circuit is internally designed with a four-to-two signal gate, and the first voltage, the second voltage, the battery detection voltage and the current setting voltage are input respectively; the output end of the logic control circuit is connected with the first comparator and outputs the charging enable signal; the output end of the first comparator is feedback connected with the logic control circuit; when the lithium battery is in the charging stage, the logic control circuit inputs the current setting voltage and the second voltage to the first comparator; after the lithium battery is fully charged, the output signal of the first comparator is feedback connected with the logic control circuit, the four-to-two signal gate selects the battery detection voltage and the first voltage, the BAT pin voltage is detected and the charging function is started, and the charging can be stopped after the battery is fully charged, so that the full charging voltage precision of the battery is improved and the safety of the battery charging is ensured.

[0036] The above is only a specific implementation of the application, but the protection scope of the application is not limited to this, any skilled person in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A linear controller for charging lithium battery, comprising a charging main loop, a lithium battery, a current setting resistor and a charging indicator light, provided with a BAT pin and an ISET pin, the charging main loop is connected with a logic control circuit and a current setting resistor respectively, characterized in that, Also include a logic control circuit and a first comparator, the logic control circuit is internally designed with a four-to-two signal gate, respectively input first voltage, second voltage, battery detection voltage and current setting voltage, the first voltage is set to 1.0125V, the second voltage is set to 0.1V, the output end of the logic control circuit is connected with the first comparator and the output charging enable signal respectively, the output end of the first comparator is feedback connected back to the logic control circuit, when the lithium battery is in the charging stage, if the lithium battery voltage is close to the full charge voltage, the ISET pin voltage decreases with the decrease of the charging current, the logic control circuit inputs the current setting voltage and the second voltage to the first comparator, when the current setting voltage is less than the second voltage, the first comparator output is high, the logic control circuit output charging enable signal is low, and the signal input to the first comparator is changed, the lithium battery stops charging; after the lithium battery charging is completed, the output signal of the first comparator is feedback to the logic control circuit, the internal four-to-two signal gate of the logic control circuit selects the battery detection voltage and the first voltage, if the BAT pin voltage drops to the recharge threshold voltage, the first comparator output is low, the logic control circuit output charging enable signal is high, and the BAT pin voltage detection and charging function are started.

2. The linear controller for charging of lithium batteries according to claim 1, characterized in that, The charging main loop includes a second comparator, a second gate, a first amplifier, a second amplifier, a third amplifier, a first PMOS tube and a second PMOS tube, the second PMOS tube is a charging PMOS tube, and the size is set to be multiple times of the first PMOS tube, the first PMOS tube and the second PMOS tube are mirror connected, the sources are connected with VIN, the gates are connected with the output ends of the second amplifier and the third amplifier, and the drains are connected with the input end of the first amplifier.

3. The linear controller for charging of lithium batteries according to claim 2, characterized in that, A third PMOS tube and a fourth PMOS tube are further arranged, the output end of the first amplifier is connected with the gate of the third PMOS tube, and the opening degree of the third PMOS tube is controlled, the source of the third PMOS tube is connected with the drain of the first PMOS tube, and the drain of the third PMOS tube is connected with the ISET pin; the source of the fourth PMOS tube is connected with VIN, the gate is connected with the charging enable signal, and the drain is connected with the output ends of the second amplifier and the third amplifier.

4. The linear controller for charging of lithium batteries as claimed in claim 2 wherein, The second amplifier is a constant current control module, the negative input end is connected with the second gate, and the positive input end is connected with the ISET pin, the second amplifier inputs the first reference voltage and the ISET pin voltage, and the ISET pin voltage is clamped to a fixed size by setting the first reference voltage.

5. The linear controller for charging of lithium batteries as claimed in claim 2 wherein, The output end of the second comparator is connected with the input end of the second gate, the input end of the second comparator is connected with the battery detection voltage and the second reference voltage, the second comparator is used for detecting the BAT pin voltage, and the size of the first reference voltage output by the second gate is controlled, so that the charging main loop is in the trickle charging mode or the constant current charging mode.

6. The linear controller for charging of lithium batteries as claimed in claim 2 wherein, The input end of the third amplifier is connected with the battery detection voltage and the third reference voltage, when the lithium battery voltage is close to the full charge voltage, the charging main loop enters the constant voltage charging mode, and the third amplifier controls the linear decline of the charging current.

7. The linear controller for charging of lithium batteries according to claim 6, characterized in that, The first resistance, the second resistance, the third resistance and the fourth resistance are further included, one end of the first resistance is connected with the negative input end of the third amplifier, the other end of the first resistance is connected with the second resistance, the third resistance and the fourth resistance in sequence and grounded, the connection point of the first resistance and the second resistance is connected with the logic control circuit, the connection point of the second resistance and the third resistance is connected with the second gate, and the connection point of the third resistance and the fourth resistance is connected with the logic control circuit.

8. The linear controller for charging of lithium batteries as claimed in claim 1 wherein, The first voltage dividing resistor and the second voltage dividing resistor are further provided, one end of the first voltage dividing resistor is connected with the positive electrode of the lithium battery through the BAT pin, the other end of the first voltage dividing resistor is connected with the second voltage dividing resistor, and the second voltage dividing resistor is grounded.

9. The linear controller for charging of lithium batteries as claimed in claim 1 wherein, The fifth resistance and the first NMOS tube are further provided, one end of the charging indicator lamp is connected with the VIN, the other end of the charging indicator lamp is connected with the fifth resistance, the other end of the fifth resistance is connected with the source of the first NMOS tube, the gate of the first NMOS tube is connected with the logic control circuit, and the drain is grounded.

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