Lithium Battery Charging Method and Device

Abstract

The present invention relates to a lithium battery charging method and device. Its charging process includes a first charging control state and a second charging control state; after entering the first charging control state, the supply voltage output by the power supply end is reduced and the charging of the lithium battery BT1 by the charging end is maintained until the voltage difference between the supply voltage output by the power supply end and the voltage of the lithium battery BT1 is less than a preset voltage threshold VTH, then the charging of the lithium battery BT1 by the charging end is stopped and the second charging control state is entered; after entering the second charging control state, when the collected load current is less than the load current threshold ITH, the supply voltage output by the power supply end is increased and the charging state of the lithium battery BT1 by the charging end is restored until the collected load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply end is in the rated voltage state. The present invention can effectively improve the charging efficiency of the lithium battery, and is safe and reliable.

Description

Technical Field

[0001] The present invention relates to a charging method and device, in particular to a lithium battery charging method and device. Background Art

[0002] Currently, charging a lithium battery includes a charging terminal connected to the lithium battery and a power supply terminal connected to an external power supply. The effective charging of the lithium battery is achieved by the cooperation of the power supply terminal and the charging terminal. During charging, the required voltage can be generated by the power supply terminal, and the charging current and the maximum output voltage can be controlled by the charging terminal, that is, constant current / constant voltage control can be achieved through the charging terminal. During charging, the battery voltage gradually increases from a certain voltage.

[0003] When charging a lithium battery, the charging terminal will generate losses. Specifically, the generated losses are proportional to the voltage difference between the output voltage of the charging terminal and the battery voltage. For example, if the charging current of the lithium battery is 1A, the output voltage of the charging terminal is 5V, and the voltage of the lithium battery at the receiving end is 3.0V, the efficiency loss is (5V - 3V) * 1A = 2w, and the effective power, that is, the energy obtained by the lithium battery, is: 3V * 1A = 3w, and the charging efficiency is only: 3w / (2w + 3w) = 60%. The low charging efficiency is difficult to meet the current charging requirements. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies in the prior art and provide a lithium battery charging method and device, which can effectively improve the charging efficiency of the lithium battery and is safe and reliable.

[0005] According to the technical solution provided by the present invention, the lithium battery charging method includes a power supply terminal connected to an external power supply and a charging terminal adaptively connected to the power supply terminal. The charging terminal can be adaptively connected to the lithium battery BT1 to be charged; when charging the lithium battery BT1, the charging process includes a first charging control state and a second charging control state, wherein,

[0006] After charging the lithium battery BT1, collect the load current when the lithium battery BT1 is charged. When the collected load current is greater than the load current threshold ITH, enter the first charging control state;

[0007] After entering the first charging control state, reduce the supply voltage output by the power supply terminal and keep the charging terminal charging the lithium battery BT1 until the voltage difference between the supply voltage output by the power supply terminal and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH, stop the charging terminal from charging the lithium battery BT1 and enter the second charging control state;

[0008] After entering the second charging control state, when the collected load current is less than the load current threshold ITH, the supply voltage output by the power supply terminal is increased, and the charging state of the lithium battery BT1 by the charging terminal is restored until the collected load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply terminal is in the rated voltage state; when the collected load current during charging is greater than the load current threshold ITH, enter the first charging control state;

[0009] Determine the charging state of the lithium battery BT1 during charging, and select to enter the first charging control state or the second charging control state according to the charging state of the lithium battery BT1 until the lithium battery BT1 is in the fully charged state.

[0010] When starting to charge the lithium battery BT1 connected to the charging terminal, the supply voltage output by the power supply terminal is in the rated voltage state;

[0011] When the lithium battery BT1 is close to the fully charged state, the charging current of the lithium battery BT1 is reduced through the charging terminal. When the collected load current is always less than the load current threshold ITH, the power supply terminal maintains the output supply voltage at the rated voltage state;

[0012] When in the first charging control state, the supply voltage output by the power supply terminal is gradually reduced step by step one or more times at intervals; when in the second charging control state, the supply voltage output by the power supply terminal is gradually increased step by step one or more times at intervals.

[0013] The power supply terminal includes a power supply terminal drive circuit and a peak current detection circuit for collecting the load current. The output terminal of the peak current detection circuit is connected to one input terminal of a comparator, and the comparator can be used to compare the load current with the load current threshold ITH;

[0014] The output terminal of the comparator is connected to a timing logic control module. The output terminal of the timing logic control module is connected to a reference adjustment module. The input terminal of the reference adjustment module is also connected to a bandgap reference module. The output terminal of the reference adjustment module is connected to an error amplifier. The output terminal of the error amplifier is connected to a PWM comparator. The PWM comparator is connected to the power supply terminal drive circuit.

[0015] It also includes a current sampling ramp compensation circuit that can collect the load current. The current sampling ramp compensation circuit is connected to the input terminal of the PWM comparator. The output terminal of the PWM comparator is connected to the power supply terminal drive circuit through a logic control circuit;

[0016] The output terminals of the power supply terminal driving circuit are respectively connected to the gate terminals of NMOS transistor Q1 and NMOS transistor Q2. The drain terminal of NMOS transistor Q1 is connected to the input terminal of the peak current detection circuit, the input terminal of the current sampling ramp compensation circuit, and one end of resistor R1. The other end of resistor R1 is connected to power supply VCC. The source terminal of NMOS transistor Q1 is connected to the drain terminal of NMOS transistor Q2 and one end of inductor L1. The source terminal of NMOS transistor Q2 is grounded. The other end of inductor L1 is connected to one end of capacitor C2, one end of resistor R2, and the charging terminal. The other end of resistor R2 is connected to one end of resistor R3 and the input terminal of the error amplifier. The other end of resistor R3 and the other end of capacitor C2 are grounded.

[0017] The charging terminal includes a linear charging control module connected to the power supply terminal. The linear charging control module is adaptively connected to lithium battery BT1. Through the linear charging control module, the supply voltage output by the power supply terminal can be collected, and the supply voltage of the power supply terminal can be compared with the voltage of lithium battery BT1 to obtain the voltage difference between the supply voltage of the power supply terminal and the voltage of lithium battery BT1. And when the voltage difference is less than the preset voltage threshold VTH in the linear charging control module, the linear charging control module stops charging lithium battery BT1.

[0018] According to the states of the load current and the load current threshold ITH, the comparator can load a current comparison signal LL_CTRL to the timing logic control module. Under the action of the current comparison signal LL_CTRL and the clock signal CLK, the timing logic control module can obtain a voltage adjustment flag signal LL_FLAG and a voltage adjustment time period CLK_dealy.

[0019] The reference adjustment module can adjust the bandgap reference voltage value loaded by the bandgap reference module according to the voltage adjustment flag signal LL_FLAG and the voltage adjustment time period CLK_dealy to obtain a reference state value. The power supply terminal driving circuit can reduce or increase the output supply voltage according to the reference state value.

[0020] A lithium battery charging device includes a power supply terminal connected to an external power supply and a charging terminal adaptively connected to the power supply terminal. Through the charging terminal, it can be adaptively connected to the lithium battery BT1 to be charged. When charging the lithium battery BT1, the charging process includes a first charging control state and a second charging control state, where

[0021] After charging the lithium battery BT1, the load current during the charging of the lithium battery BT1 is collected. When the collected load current is greater than the load current threshold ITH, it enters the first charging control state.

[0022] After entering the first charging control state, the supply voltage output by the power supply terminal is reduced and the charging terminal continues to charge the lithium battery BT1 until the voltage difference between the supply voltage output by the power supply terminal and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH. Then, the charging of the lithium battery BT1 by the charging terminal is stopped and the second charging control state is entered.

[0023] After entering the second charging control state, when the collected load current is less than the load current threshold ITH, the supply voltage output by the power supply terminal is increased and the charging state of the charging terminal to the lithium battery BT1 is restored until the load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply terminal is in the rated voltage state. When the load current during charging is greater than the load current threshold ITH, the first charging control state is entered.

[0024] Determine the charging state of the lithium battery BT1 during charging, and select to enter the first charging control state or the second charging control state according to the charging state of the lithium battery BT1 until the lithium battery BT1 is fully charged.

[0025] The power supply terminal includes a power supply terminal drive circuit and a peak current detection circuit for collecting the load current. The output terminal of the peak current detection circuit is connected to one input terminal of the comparator, and the comparator can be used to compare the load current with the load current threshold ITH.

[0026] The output terminal of the comparator is connected to the timing logic control module. The output terminal of the timing logic control module is connected to the reference adjustment module. The input terminal of the reference adjustment module is also connected to the bandgap reference module. The output terminal of the reference adjustment module is connected to the error amplifier. The output terminal of the error amplifier is connected to the PWM comparator. The PWM comparator is connected to the power supply terminal drive circuit.

[0027] It also includes a current sampling ramp compensation circuit that can collect the load current. The current sampling ramp compensation circuit is connected to the input terminal of the PWM comparator. The output terminal of the PWM comparator is connected to the power supply terminal drive circuit through a logic control circuit.

[0028] The output terminals of the power supply terminal driving circuit are respectively connected to the gate terminals of NMOS transistor Q1 and NMOS transistor Q2. The drain terminal of NMOS transistor Q1 is connected to the input terminal of the peak current detection circuit, the input terminal of the current sampling ramp compensation circuit, and one end of resistor R1. The other end of resistor R1 is connected to power supply VCC. The source terminal of NMOS transistor Q1 is connected to the drain terminal of NMOS transistor Q2 and one end of inductor L1. The source terminal of NMOS transistor Q2 is grounded. The other end of inductor L1 is connected to one end of capacitor C2, one end of resistor R2, and the charging terminal. The other end of resistor R2 is connected to one end of resistor R3 and the input terminal of the error amplifier. The other end of resistor R3 and the other end of capacitor C2 are grounded.

[0029] The power supply terminal further includes an overheat protection module and an under-voltage protection module;

[0030] The charging terminal includes a linear charging control module connected to the power supply terminal. The linear charging control module is adaptively connected to lithium battery BT1. Through the linear charging control module, the supply voltage output by the power supply terminal can be collected, and the supply voltage of the power supply terminal and the voltage of lithium battery BT1 can be compared to obtain the voltage difference between the supply voltage of the power supply terminal and the voltage of lithium battery BT1. When the voltage difference is less than the preset voltage threshold VTH in the linear charging control module, the linear charging control module stops charging lithium battery BT1.

[0031] Advantages of the present invention: When the collected load current is greater than the load current threshold ITH, it enters the first charging control state; after entering the first charging control state, the supply voltage output by the power supply terminal is reduced and the charging of lithium battery BT1 by the charging terminal is maintained until the voltage difference between the supply voltage output by the power supply terminal and the voltage of lithium battery BT1 is less than the preset voltage threshold VTH, and the charging of lithium battery BT1 by the charging terminal is stopped and it enters the second charging control state; after entering the second charging control state, when the collected load current is less than the load current threshold ITH, the supply voltage output by the power supply terminal is increased, and the charging state of lithium battery BT1 by the charging terminal is restored until the load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply terminal is in the rated voltage state; when the load current during charging is greater than the load current threshold ITH, it enters the first charging control state;

[0032] Due to the preset voltage difference threshold VTH in the charging terminal, it can ensure that the rated charging current is not affected, only the additional loss of the charging terminal is reduced. After reducing the voltage drop loss of the power supply terminal and the charging terminal, the charging efficiency of lithium battery BT1 can be improved, which is safe and reliable. Brief Description of the Drawings

[0033] Figure 1 It is a system block diagram of the invention.

[0034] Figure 2 It is the structural block diagram of the power supply end of the present invention.

[0035] Figure 3 It is the schematic diagram of the reference adjustment module of the present invention.

[0036] Figure 4 It is the schematic diagram of the timing logic control module of the present invention.

[0037] Explanation of reference numerals: 1 - power supply end, 2 - charging end, 3 - linear charging control module, 4 - status indicator filter, 5 - power supply end drive circuit, 6 - peak current detection circuit, 7 - bandgap reference module, 8 - overheat protection module, 9 - undervoltage protection module, 10 - current sampling ramp compensation circuit, 11 - comparator, 12 - timing logic control module, 13 - PWM comparator, 14 - logic control circuit, 15 - reference adjustment module, 16 - error amplifier, 17 - oscillator, and 18 - clock generator. Specific embodiments

[0038] The present invention will be further described below in conjunction with specific drawings and embodiments.

[0039] As Figure 1 shown: In order to effectively improve the charging efficiency of the lithium battery BT1, the lithium battery charging method of the present invention includes a power supply end 1 connected to an external power supply and a charging end 2 adaptively connected to the power supply end 1, and the charging end 2 can be adaptively connected to the lithium battery BT1 to be charged; when charging the lithium battery BT1, the charging process includes a first charging control state and a second charging control state, wherein

[0040] After charging the lithium battery BT1, the load current during charging of the lithium battery BT1 is collected. When the collected load current is greater than the load current threshold ITH, it enters the first charging control state;

[0041] After entering the first charging control state, the supply voltage output by the power supply end 1 is reduced and the charging of the lithium battery BT1 by the charging end 2 is maintained until the voltage difference between the supply voltage output by the power supply end 1 and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH, then the charging of the lithium battery BT1 by the charging end 2 is stopped and it enters the second charging control state;

[0042] After entering the second charging control state, when the collected load current is less than the load current threshold ITH, the supply voltage output by the power supply end 1 is increased, and the charging state of the lithium battery BT1 by the charging end 2 is restored until the load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply end 1 is in the rated voltage state; when the load current during charging is greater than the load current threshold ITH, it enters the first charging control state;

[0043] Determine the charging status of the lithium battery BT1 during charging, and select to enter the first charging control state or the second charging control state according to the charging status of the lithium battery BT1 until the lithium battery BT1 is fully charged.

[0044] Specifically, the power supply terminal 1 can be connected to an external power source, and the charging terminal 2 can be connected to the lithium battery BT1. The connection cooperation between the power supply terminal 1 and the charging terminal 2, as well as the connection cooperation between the charging terminal 2 and the lithium battery BT1, are the same as the existing ones, which are well-known to those skilled in the art and will not be elaborated here. When the power supply terminal 1 is connected to an external power source and the charging terminal 2 is connected to the lithium battery BT1, the lithium battery BT1 can be charged through the charging terminal 2.

[0045] To improve the charging efficiency of the lithium battery BT1, during the charging process of the lithium battery BT1, the charging process includes a first charging control state and a second charging control state. The specific situations of the first charging control state and the second charging control state will be described below. Generally, when starting to charge the lithium battery BT1 connected to the charging terminal 2, the power supply voltage output by the power supply terminal 1 is in the rated voltage state. The magnitude of the power supply voltage output by the power supply terminal 1 as the rated voltage can be specifically selected according to actual needs, which is specifically related to the situation of the lithium battery BT1, etc., and is well-known to those skilled in the art and will not be elaborated here. When the power supply voltage output by the power supply terminal 1 is in the rated voltage state, rapid charging of the lithium battery BT1 can be achieved.

[0046] During the charging process of the lithium battery BT1, the load current during the charging process of the lithium battery BT1 is collected at the power supply terminal 1. When the load current is less than the load current threshold ITH, the power supply terminal 1 maintains the output power supply voltage in the rated voltage state, and when the collected load current is greater than the load current threshold ITH, it enters the first charging control state. After entering the first charging control state, the power supply voltage output by the power supply terminal 1 is reduced. After reducing the power supply voltage output by the power supply terminal 1, the charging control state of the lithium battery BT1 is maintained by the charging terminal 2, and when the voltage difference between the power supply voltage output by the power supply terminal 1 and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH, the charging of the lithium battery BT1 by the charging terminal 2 is stopped.

[0047] During specific implementation, when reducing the power supply voltage output by the power supply terminal 1, the power supply voltage output by the power supply terminal 1 is gradually reduced at one time or multiple times at intervals. The number of times of specifically reducing the power supply voltage output by the power supply terminal 1, the magnitude of the voltage reduction each time, and the interval time can all be selected according to needs, as long as it can ensure that the charging of the lithium battery BT1 will not be affected, which is well-known to those skilled in the art and will not be elaborated here.

[0048] In an embodiment of the present invention, when entering the second charging control electrical state, the charging terminal 2 stops charging the lithium battery BT1. After the charging terminal 2 stops charging the lithium battery BT1, the collected load current will inevitably be less than the load current threshold ITH. When the load current is less than the load current threshold ITH, the power supply voltage output by the power supply terminal 1 is increased, and the charging state of the charging terminal 2 to the lithium battery BT1 is restored. Increasing the power supply voltage output by the power supply terminal 1 specifically means that compared with the power supply voltage output by the power supply terminal 1 when entering the second charging control state, the current power supply voltage output by the power supply terminal 1 increases. Under the current output power supply voltage, the power supply terminal 1 can simultaneously satisfy that the load current is less than the load current threshold ITH, and the voltage difference between the power supply voltage output by the power supply terminal 1 and the voltage of the lithium battery BT1 is greater than the preset voltage threshold VTH, and a relatively high charging efficiency can be maintained in the current state.

[0049] Thereafter, if the load current is still less than the load current threshold ITH, the power supply voltage output by the power supply terminal 1 can be continuously increased until the load current during charging is greater than the load current threshold ITH or the power supply voltage output by the power supply terminal 1 is in the rated voltage state. From the above description, it can be seen that when the load current during charging is greater than the load current threshold ITH, the first charging control state is entered; when the power supply voltage output by the power supply terminal 1 is in the rated voltage state and the load current is not greater than the load current threshold ITH, the current output power supply voltage of the power supply terminal 1 is maintained, and the charging of the charging terminal 2 to the lithium battery BT1 is maintained until the lithium battery BT1 is close to being fully charged.

[0050] During specific implementation, determining the charging state of the lithium battery BT1 during charging specifically means collecting the magnitude relationship between the load current during charging of the lithium battery BT1 and the load current threshold ITH, and the relationship between the voltage difference between the power supply voltage of the power supply terminal 1 and the voltage of the lithium battery BT1 and the preset voltage threshold VTH, so as to be able to select to enter the first charging control state or the second charging control state according to the charging state of the lithium battery BT1 until the lithium battery BT1 is in a fully charged state. Of course, during the specific charging process, in addition to the first charging control state and the second charging control state, there are also other charging states, such as the state when the lithium battery BT1 starts charging and the state when it is close to being fully charged, etc. The specific states can be consistent with the existing charging states, which are well known to those skilled in the art of the present technology and will not be elaborated here.

[0051] During specific implementation, when the lithium battery BT1 is close to being fully charged, the charging current supplied to the lithium battery BT1 is reduced through the charging terminal 2. When the collected load current is always less than the load current threshold ITH, the power supply terminal 1 maintains the output supply voltage at the rated voltage state. When increasing the supply voltage output by the power supply terminal 1, the supply voltage output by the power supply terminal 1 can be increased step by step at intervals once or multiple times. For the specific situation of increasing the supply voltage output by the power supply terminal 1, reference can be made to the above description of reducing the supply voltage output by the power supply terminal 1, and specific selection can be made according to needs, which will not be elaborated here.

[0052] Under normal circumstances, the power supply terminal 1 provides a constant output voltage, and the charging terminal 2 serves as the load of the power supply terminal 1. The load current of the power supply terminal 1 consists of two parts. One part is the self-loss of the charging terminal 2, and the other part is the charging current for controlling the lithium battery BT1. The self-loss of the charging terminal 2 is relatively small, usually about 1 mA, while the charging current of the lithium battery BT1 is mostly greater than 100 mA. Therefore, the self-loss of the charging terminal 2 can be ignored, and the load current of the power supply terminal 1 can be approximately equal to the charging current of the lithium battery BT1, so that the load current during the charging process of the lithium battery BT1 can be effectively collected.

[0053] During specific implementation, for the collection of the load current, any of the following methods can be used:

[0054] 1) By detecting the inductor current and calculating the load current value according to the working architecture (buck, boost, etc.);

[0055] 2) By adding a sampling resistor and detecting the voltage value on the sampling resistor to reflect the load current;

[0056] 3) Also multiplexing the judgment signal for switching the light load mode as this control signal (switching the light load mode is also judged according to the load being less than a certain threshold);

[0057] 4) ADC sampling can also be used.

[0058] Therefore, the specific form of collecting the load current can be selected according to needs, which is well-known to those skilled in the art and will not be elaborated here.

[0059] In an embodiment of the present invention, a preset voltage difference threshold VTH is set in the charging terminal 2. By means of the preset voltage difference threshold VTH, the charging terminal 2 can be made to enter a charging state or a charging stop state for the lithium battery BT1, and the current changes corresponding to the charging state and the charging stop state are relatively large, so that the power supply terminal 1 can easily judge. For the preset voltage difference threshold VTH, when setting, when the voltage difference between the power supply voltage output by the power supply terminal 1 and the voltage of the lithium battery BT1 is equal to the preset voltage difference threshold VTH, it can exactly ensure that the charging terminal 2 can charge the lithium battery BT1 with the maximum rated current under any conditions. Therefore, the preset voltage difference threshold VTH needs to be selected according to the actual charging situation, which is well known to those skilled in the art and will not be elaborated here.

[0060] For the load current threshold ITH, the load current threshold ITH is set in the power supply terminal 1. By means of the load current threshold ITH, it can be distinguished whether the charging terminal 2 is in a charging state or a charging stop state, and then it is determined whether the power supply terminal 1 raises or lowers the output power supply voltage. For the setting of the load current threshold ITH: Theoretically, the load current threshold ITH only needs to be smaller than the minimum rated charging current of the charging terminal 1, so that as long as the charging terminal 2 stops charging, the power supply terminal 2 can judge. However, considering the error factor, half of the minimum rated charging current of the charging terminal 2 can be selected. In addition, if there are other loads connected to the power supply terminal 1 in addition to supplying power to the charging terminal 2, then this load current threshold ITH needs to be additionally added with the other load currents, otherwise the power supply terminal 1 cannot detect that the charging terminal 2 stops charging the lithium battery BT1.

[0061] In summary, due to the preset voltage difference threshold VTH in the charging terminal 2, it can ensure that the rated charging current is not affected, and only the additional loss of the charging terminal 2 is reduced. Therefore, the charging efficiency of the lithium battery BT1 can be improved, and it is safe and reliable.

[0062] As Figure 2 shown, the power supply terminal 1 includes a power supply terminal drive circuit 5 and a peak current detection circuit 6 for collecting the peak value of the load current. The output end of the peak current detection circuit 6 is connected to an input end of a comparator 11. Through the comparator 11, the comparison between the load current and the load current threshold ITH can be realized;

[0063] The output end of the comparator 11 is connected to a timing logic control module 12. The output end of the timing logic control module 12 is connected to a reference adjustment module 15. The input end of the reference adjustment module 15 is also connected to a bandgap reference module 7. The output end of the reference adjustment module 15 is connected to an error amplifier 16. The output end of the error amplifier 16 is connected to a PWM comparator 13. The PWM comparator 13 is connected to the power supply terminal drive circuit 5.

[0064] It further includes a current sampling ramp compensation circuit 10 capable of collecting the load current. The current sampling ramp compensation circuit 10 is connected to the input end of the PWM comparator 13, and the output end of the PWM comparator 13 is connected to the power supply terminal driving circuit 5 through the logic control circuit 14;

[0065] The output end of the power supply terminal driving circuit 5 is respectively connected to the gate terminals of the NMOS transistor Q1 and the NMOS transistor Q2. The drain terminal of the NMOS transistor Q1 is connected to the input end of the peak current detection circuit 6, the input end of the current sampling ramp compensation circuit 10, and one end of the resistor R1. The other end of the resistor R1 is connected to the power supply VCC; the source terminal of the NMOS transistor Q1 is connected to the drain terminal of the NMOS transistor Q2 and one end of the inductor L1. The source terminal of the NMOS transistor Q2 is grounded. The other end of the inductor L1 is connected to one end of the capacitor C2, one end of the resistor R2, and the charging terminal 2. The other end of the resistor R2 is connected to one end of the resistor R3 and the input end of the error amplifier 16. The other end of the resistor R3 and the other end of the capacitor C2 are grounded.

[0066] Specifically, Figure 2 An implementation of the power supply terminal 1 is shown in . Specifically, taking the buck circuit as an example, the specific functions and cooperation of the error amplifier 16, the PWM comparator 13, the current sampling ramp compensation circuit 10, the logic control module 14, the power supply terminal driving circuit 5, the overheat protection module 8, and the undervoltage protection module 9 are all consistent with the main functions of the existing DC - DC buck circuit, which are well - known to those skilled in the art and will not be elaborated here.

[0067] In the embodiment of the present invention, the driving output can be realized through the power supply terminal driving circuit 5, and the peak value of the load current can be collected through the peak current detection circuit 6. When the comparator 11 performs the comparison, the peak value of the load current is compared with the load current threshold ITH, which improves the accuracy of the comparison between the load current and the load current threshold ITH.

[0068] Specifically, the resistor R1 is a current sampling resistor: generally, to avoid additional power loss, the resistor is set to about 10Ω. The peak current detection module 6 converts the current flowing through the resistor R1 into a voltage and amplifies it to obtain a voltage signal VSENSE reflecting the current flowing through the NMOS transistor Q1; in the buck circuit, the output load current I LOAD and the inductor peak current I PEAK satisfy the following relationship:

[0069]

[0070] where VOUT is the supply voltage output by the power supply terminal 1; VIN is the input power supply of the power supply terminal 1, that is Figure 2The power supply voltage connected to the VCC terminal; L is the inductor of the buck circuit, which is the Figure 2 inductor L1 in

[0071] Comparator 11 can adopt the commonly used existing form. For the convenience of comparison, comparator 11 adopts a voltage comparator, that is, the load current is reflected by VSENSE, and the load current threshold ITH is reflected by VREF1. The voltage VREF1 is output by the bandgap reference module 7. The specific magnitude relationship between the load current and the load current threshold ITH can be determined through the output of comparator 11.

[0072] In specific implementation, the power supply terminal 1 adopts a current-mode buck circuit structure. The oscillator 17 generates a clock signal with a fixed frequency. The reference adjustment module 15 outputs a variable reference voltage, which is input to the error amplifier 16 together with the feedback signal FB of the output voltage. The error amplifier 16 can output an error amplified voltage signal. The current sampling slope compensation circuit 10 samples the current of the inductor L1, and can obtain the required slope signal according to the sampled current and the preset slope compensation signal. Specifically, the harmonic signal can be obtained by using the commonly used technical means in the field, which is well known to those skilled in the art and will not be elaborated here. The error signal and the slope signal are used by the PWM comparator 13 to generate a control signal with an adjustable duty cycle, and then the logic control module 14 processes it with the clock signal generated by the oscillator 17 into a clock signal with a variable duty cycle, which controls the NMOS transistor Q1 and the NMOS transistor Q2 through the power supply terminal drive circuit 5.

[0073] Ignoring the influence of parasitic factors, the relationship between the output voltage V OUT of the buck circuit, the input voltage V IN and the duty cycle D is as shown in the formula: V OUT =V IN *D; thus, when the reference voltage of the reference adjustment module 15 becomes lower, the duty cycle decreases, and the output voltage becomes smaller. Vice versa, that is, the reduction or increase of the supply voltage output by the power supply terminal 1 can be effectively realized.

[0074] Specifically, comparator 11 can load a current comparison signal LL_CTRL to the timing logic control module 12 according to the states of the load current and the load current threshold ITH. Under the action of the current comparison signal LL_CTRL and the clock signal CLK, the timing logic control module 12 can obtain a voltage adjustment flag signal LL_FLAG and a voltage adjustment time period CLK_dealy;

[0075] The reference adjustment module 15 can adjust the bandgap reference voltage value loaded by the bandgap reference module 7 according to the voltage adjustment flag signal LL_FLAG and the voltage adjustment time period CLK_dealy, so as to obtain a reference state value. The power supply terminal drive circuit can reduce or increase the output power supply voltage according to the reference state value.

[0076] As Figure 4 shown, it is a specific implementation schematic diagram of the timing logic control module 12 of the present invention. Among them, the timing logic control module 12 includes a voltage adjustment flag circuit, a voltage time adjustment period circuit, and a time generator 18. The time generator 18 can generate a clock signal CLK, and the time signal CLK generated by the time generator 18 can be loaded into the voltage adjustment flag circuit and the voltage time adjustment period circuit at the same time.

[0077] For the voltage time adjustment period circuit, it includes several D flip-flops, Figure 4 which are D1, D2, …, Dn in the figure. The specific value of n is selected according to the actual situation, so as to obtain the required voltage adjustment time period CLK_dealy. Figure 4 In the figure, the voltage adjustment time period CLK_dealy is 8 ms. For the n D flip-flops in the voltage time adjustment period circuit, the CLK terminal of the D flip-flop D1 is connected to the output terminal of the time generator 18, the D terminal of the D flip-flop D1 is connected to the terminal of the D flip-flop D1, the Q terminal of the D flip-flop D1 is connected to the CLK terminal of the D flip-flop D2, the D terminal of the D flip-flop D2 is connected to the terminal of the D flip-flop D2, the Q terminal of the D flip-flop D2 is connected to the CLK terminal of the D flip-flop D3, the D terminal of the D flip-flop D3 is connected to the terminal of the D flip-flop D3, the Q terminal of the D flip-flop D3 is connected to the CLK terminal of the subsequent D flip-flop, and the connection states between the remaining D flip-flops can refer to the connection and cooperation between the D flip-flop D2 and the D flip-flop D3 until the voltage adjustment time period CLK_dealy can be output through the Q terminal of the D flip-flop Dn.

[0078] For the voltage adjustment flag circuit, it includes D flip-flop DM1, D flip-flop DM2, D flip-flop DM3, and NAND gate U2. Among them, the CLK terminals of D flip-flop DM1, D flip-flop DM2, and D flip-flop DM3 are all connected to the output terminal of the time generator 18. The Q terminal of D flip-flop DM1 is connected to the D terminal of D flip-flop DM2. The Q terminal of D flip-flop DM2 is connected to the D terminal of D flip-flop DM3. The D terminal of D flip-flop Dm1 receives the current comparison signal LL_CTRL. The input terminals of NAND gate U2 receive the current comparison signal LL_CTRL and the enable signal EN simultaneously. The output terminal of NAND gate U2 is connected to the CLR terminals of D flip-flop DM1, D flip-flop DM2, and D flip-flop DM3 simultaneously. The CLR terminal is the reset terminal of the D flip-flop. The voltage adjustment flag signal LL_FLAG can be obtained through the Q terminal of D flip-flop DM3.

[0079] In specific implementation, the timing logic control module 12 can also adopt other implementation forms, which can be specifically selected according to needs and will not be elaborated here.

[0080] As Figure 3 shown, it is a specific implementation of the reference adjustment module 15. Specifically, it includes operational amplifier U1, NMOS transistor Q3, several resistors, and several selection switches. The non-inverting terminal of operational amplifier U1 receives the reference voltage VREF2 generated by the bandgap reference module 7. The output terminal of operational amplifier U1 is connected to the gate terminal of NMOS transistor Q3. The drain terminal of NMOS transistor Q3 is connected to the voltage VDD. The magnitude of the voltage VDD can be selected according to actual needs and is well-known to those skilled in the art. Figure 3 Among them, the resistors include resistor R4, resistor R5, resistor R6, resistor R7, resistor R24, and resistor R25. Among them, resistor R4, resistor R5, resistor R6, resistor R7, resistor R24, and resistor R25 are connected in series in sequence. One end of resistor R4 is connected to the inverting terminal of operational amplifier U1 and the source terminal of NMOS transistor Q3. Resistor R25 is grounded.

[0081] The number of selection switches is the same as the number of the above-mentioned series-connected resistors. By cooperating the selection switches with the resistors, different voltages can be selected. Figure 3Among them, one end of the selection switch S1 is connected to one end of the resistor R4, the inverting terminal of the operational amplifier U1, and the source terminal of the NMOS transistor Q3. One end of the selection switch S2 is connected to the other end of the resistor R4 and one end of the resistor R5. One end of the selection switch S3 is connected to the other end of the resistor R5 and one end of the resistor R6. One end of the selection switch S4 is connected to the other end of the resistor R6 and one end of the resistor R7, and so on. One end of the selection switch S20 is connected to one end of the resistor R24. One end of the selection switch S21 is connected to the other end of the resistor R24 and one end of the resistor R25. Specifically in implementation, the number of selection switches and the number of series-connected resistors can be specifically selected according to actual needs, which will not be elaborated here.

[0082] The other ends of all the selection switches are connected to each other and form a reference voltage adjustment output terminal VRFF. When different selection switches are closed, different adjusted reference voltages can be obtained. For example, when the reference voltage VREF2 is 1.25V, when the selection switch S1 is closed, a voltage of 1.25V can be obtained at the reference voltage adjustment output terminal VREF. When the selection switch S2 is closed, a voltage of 1.225V can be obtained at the reference voltage adjustment output terminal VREF. The situations when other selection switches are closed can be calculated according to the specific conditions of the resistors, which are well-known to those skilled in the art and will not be elaborated here. When it is necessary to reduce the supply voltage output by the supply terminal 1, the voltage of the reference voltage adjustment output terminal VREF can be increased, and when it is necessary to reduce the supply voltage output by the supply terminal 1, the voltage of the reference voltage output terminal VREF can be reduced. That is, the supply terminal drive circuit 5 can adjust the output supply voltage according to the specific change situation of the reference voltage adjustment output terminal VREF.

[0083] Further, the charging terminal 2 includes a linear charging control module 3 connected to the supply terminal 1. The linear charging control module 3 is adaptively connected to the lithium battery BT1. Through the linear charging control module 3, the supply voltage output by the supply terminal 1 can be collected, and the supply voltage of the supply terminal 1 and the voltage of the lithium battery BT1 can be compared to obtain the voltage difference between the supply voltage of the supply terminal 1 and the voltage of the lithium battery BT1. And when the voltage difference is less than the preset voltage threshold VTH in the linear charging control module 3, the linear charging control module 3 stops charging the lithium battery BT1.

[0084] In the embodiment of the present invention, when the supply terminal 1 adopts the above Figure 2 structure, the linear charging control module 3 of the charging terminal 2 is connected to Figure 3The other end of the inductor L1, one end of the capacitor C2, and one end of the resistor R2 are connected, that is, connected to the output end of the power supply terminal 1. In addition, a capacitor C1 is also connected between the output end of the power supply terminal 1 and the charging terminal 2, and the other end of the capacitor C1 is grounded. The output end of the linear charging control module 3, the positive terminal of the lithium battery BT1, and one end of the resistor R100 are connected. The other end of the resistor R100 is connected to the charging status indication filter 4 in the charging terminal 2. Through the charging status indication filter 4, the charging process can be indicated. The specific indication situations, such as the charging status, full charge status, or stop charging status, etc. The linear charging control module 3 and the charging status indication filter 4 in the charging terminal 2 can both adopt the existing common structural forms, which are well-known to those skilled in the art and will not be elaborated here.

[0085] In summary, the lithium battery charging device of the present invention is obtained, which includes a power supply terminal 1 connected to an external power supply and a charging terminal 2 adaptively connected to the power supply terminal 1. Through the charging terminal 2, it can be adaptively connected to the lithium battery BT1 to be charged; when charging the lithium battery BT1, the charging process includes a first charging control state and a second charging control state, where,

[0086] After charging the lithium battery BT1, collect the load current when the lithium battery BT1 is charging. When the collected load current is greater than the load current threshold ITH, enter the first charging control state;

[0087] After entering the first charging control state, reduce the supply voltage output by the power supply terminal 1 and keep the charging terminal 2 charging the lithium battery BT1 until the voltage difference between the supply voltage output by the power supply terminal 1 and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH, stop the charging terminal 2 from charging the lithium battery BT1 and enter the second charging control state;

[0088] After entering the second charging control state, when the collected load current is less than the load current threshold ITH, increase the supply voltage output by the power supply terminal 1 and restore the charging state of the charging terminal 2 to charge the lithium battery BT1 until the collected load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply terminal 1 is in the rated voltage state; when the collected load current during charging is greater than the load current threshold ITH, enter the first charging control state;

[0089] Determine the charging state when the lithium battery BT1 is charging, and select to enter the first charging control state or the second charging control state according to the charging state of the lithium battery BT1 until the lithium battery BT1 is in a fully charged state.

[0090] Specifically, the specific situations of the power supply terminal 1 and the charging terminal 2, as well as the specific cooperation working process, can all refer to the above description and will not be elaborated here.

Claims

1. A lithium battery charging method, comprising a power supply terminal (1) connected to an external power supply and a charging terminal (2) adaptively connected to the power supply terminal (1), and the charging terminal (2) can be adaptively connected to a lithium battery BT1 to be charged; characterized in that: When charging the lithium battery BT1, the charging process includes a first charging control state and a second charging control state. Among them, After charging the lithium battery BT1, collect the load current when the lithium battery BT1 is charging. When the collected load current is greater than the load current threshold ITH, enter the first charging control state; After entering the first charging control state, reduce the supply voltage output by the power supply terminal (1) and keep the charging terminal (2) charging the lithium battery BT1 until the voltage difference between the supply voltage output by the power supply terminal (1) and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH, stop the charging terminal (2) from charging the lithium battery BT1 and enter the second charging control state; After entering the second charging control state, when the collected load current is less than the load current threshold ITH, increase the supply voltage output by the power supply terminal (1), and resume the charging state of the charging terminal (2) to the lithium battery BT1 until the collected load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply terminal (1) is in the rated voltage state; when the collected load current during charging is greater than the load current threshold ITH, re-enter the first charging control state; Determine the charging state of the lithium battery BT1 during charging, and select to enter the first charging control state or the second charging control state according to the charging state of the lithium battery BT1 until the lithium battery BT1 is fully charged; For the preset voltage difference threshold VTH, when setting, when the voltage difference between the supply voltage output by the power supply terminal (1) and the voltage of the lithium battery BT1 is equal to the preset voltage difference threshold VTH, it can just ensure that the charging terminal (2) can charge the lithium battery BT1 with the maximum rated current under any conditions.

2. The lithium battery charging method according to claim 1, wherein: When starting to charge the lithium battery BT1 connected to the charging terminal (2), the supply voltage output by the power supply terminal (1) is in the rated voltage state; When the lithium battery BT1 is close to being fully charged, reduce the charging current of the lithium battery BT1 through the charging terminal (2). When the collected load current is always less than the load current threshold ITH, the power supply terminal (1) keeps the output supply voltage in the rated voltage state; When in the first charging control state, gradually reduce the supply voltage output by the power supply terminal (1) step by step one or more times at intervals; when in the second charging control state, gradually increase the supply voltage output by the power supply terminal (1) step by step one or more times at intervals.

3. The lithium battery charging method according to claim 1 or 2, characterized in that: The power supply terminal (1) includes a power supply terminal drive circuit (5) and a peak current detection circuit (6) for collecting the load current. The output end of the peak current detection circuit (6) is connected to an input end of a comparator (11), and the comparator (11) can be used to compare the load current with the load current threshold ITH; The output terminal of the comparator (11) is connected to the timing logic control module (12), the output terminal of the timing logic control module (12) is connected to the reference adjustment module (15), the input terminal of the reference adjustment module (15) is also connected to the bandgap reference module (7), the output terminal of the reference adjustment module (15) is connected to the error amplifier (16), the output terminal of the error amplifier (16) is connected to the PWM comparator (13), and the PWM comparator (13) is connected to the power supply terminal drive circuit (5).

4. The lithium battery charging method according to claim 3, wherein: It further includes a current sampling ramp compensation circuit (10) capable of collecting the load current. The current sampling ramp compensation circuit (10) is connected to the input terminal of the PWM comparator (13), and the output terminal of the PWM comparator (13) is connected to the power supply terminal drive circuit (5) through the logic control circuit (14); The output terminal of the power supply terminal drive circuit (5) is respectively connected to the gate terminals of the NMOS transistor Q1 and the NMOS transistor Q2. The drain terminal of the NMOS transistor Q1 is connected to the input terminal of the peak current detection circuit (6), the input terminal of the current sampling ramp compensation circuit (10), and one end of the resistor R1. The other end of the resistor R1 is connected to the power supply VCC; the source terminal of the NMOS transistor Q1 is connected to the drain terminal of the NMOS transistor Q2 and one end of the inductor L1. The source terminal of the NMOS transistor Q2 is grounded. The other end of the inductor L1 is connected to one end of the capacitor C2, one end of the resistor R2, and the charging terminal (2). The other end of the resistor R2 is connected to one end of the resistor R3 and the input terminal of the error amplifier (16). The other end of the resistor R3 and the other end of the capacitor C2 are grounded.

5. The lithium battery charging method according to claim 4, characterized in that: The charging terminal (2) includes a linear charging control module (3) connected to the power supply terminal (1). The linear charging control module (3) is adaptively connected to the lithium battery BT1. Through the linear charging control module (3), the supply voltage output by the power supply terminal (1) can be collected, and the supply voltage of the power supply terminal (1) and the voltage of the lithium battery BT1 can be compared to obtain the voltage difference between the supply voltage of the power supply terminal (1) and the voltage of the lithium battery BT1. And when the voltage difference is less than the preset voltage threshold VTH in the linear charging control module (3), the linear charging control module (3) stops charging the lithium battery BT1.

6. The lithium battery charging method according to claim 3, wherein: The comparator (11) can load a current comparison signal LL_CTRL to the timing logic control module (12) according to the states of the load current and the load current threshold ITH. Under the action of the current comparison signal LL_CTRL and the clock signal CLK, the timing logic control module (12) can obtain a voltage adjustment flag signal LL_FLAG and a voltage adjustment time period CLK_dealy; The reference adjustment module (15) can adjust the bandgap reference voltage value loaded by the bandgap reference module (7) according to the voltage adjustment flag signal LL_FLAG and the voltage adjustment time period CLK_dealy to obtain a reference state value. The power supply terminal drive circuit can reduce or increase the output supply voltage according to the reference state value.

7. A lithium battery charging device, comprising a power supply terminal (1) connected to an external power supply and a charging terminal (2) adaptively connected to the power supply terminal (1), and the charging terminal (2) can be adaptively connected to a lithium battery BT1 to be charged; characterized in that: When charging the lithium battery BT1, the charging process includes a first charging control state and a second charging control state. Among them, After charging the lithium battery BT1, collect the load current during the charging of the lithium battery BT1. When the collected load current is greater than the load current threshold ITH, enter the first charging control state; After entering the first charging control state, reduce the supply voltage output by the power supply terminal (1) and keep the charging terminal (2) charging the lithium battery BT1 until the voltage difference between the supply voltage output by the power supply terminal (1) and the voltage of the lithium battery BT1 is less than the preset voltage threshold VTH. Stop the charging terminal (2) from charging the lithium battery BT1 and enter the second charging control state; After entering the second charging control state, when the collected load current is less than the load current threshold ITH, increase the supply voltage output by the power supply terminal (1) and resume the charging state of the charging terminal (2) to the lithium battery BT1 until the load current during charging is greater than the load current threshold ITH or the supply voltage output by the power supply terminal (1) is in the rated voltage state; when the load current during charging is greater than the load current threshold ITH, enter the first charging control state; Determine the charging state of the lithium battery BT1 during charging, and select to enter the first charging control state or the second charging control state according to the charging state of the lithium battery BT1 until the lithium battery BT1 is fully charged; For the preset voltage difference threshold VTH, when setting, when the voltage difference between the supply voltage output by the power supply terminal (1) and the voltage of the lithium battery BT1 is equal to the preset voltage difference threshold VTH, it can just ensure that the charging terminal (2) can charge the lithium battery BT1 with the maximum rated current under any conditions.

8. The lithium battery charging device according to claim 7, characterized in that: The power supply terminal (1) includes a power supply terminal drive circuit (5) and a peak current detection circuit (6) for collecting the load current. The output terminal of the peak current detection circuit (6) is connected to an input terminal of a comparator (11), and the comparator (11) can be used to compare the load current with the load current threshold ITH; The output terminal of the comparator (11) is connected to a timing logic control module (12). The output terminal of the timing logic control module (12) is connected to a reference adjustment module (15). The input terminal of the reference adjustment module (15) is also connected to a bandgap reference module (7). The output terminal of the reference adjustment module (15) is connected to an error amplifier (16). The output terminal of the error amplifier (16) is connected to a PWM comparator (13). The PWM comparator (13) is connected to the power supply terminal drive circuit (5).

9. The lithium battery charging device according to claim 8, characterized in that: It also includes a current sampling ramp compensation circuit (10) that can collect the load current. The current sampling ramp compensation circuit (10) is connected to the input terminal of the PWM comparator (13). The output terminal of the PWM comparator (13) is connected to the power supply terminal drive circuit (5) through a logic control circuit (14); The output terminals of the power supply terminal driving circuit (5) are respectively connected to the gate terminals of the NMOS transistor Q1 and the NMOS transistor Q2. The drain terminal of the NMOS transistor Q1 is connected to the input terminal of the peak current detection circuit (6), the input terminal of the current sampling ramp compensation circuit (10), and one end of the resistor R1. The other end of the resistor R1 is connected to the power supply VCC. The source terminal of the NMOS transistor Q1 is connected to the drain terminal of the NMOS transistor Q2 and one end of the inductor L1. The source terminal of the NMOS transistor Q2 is grounded. The other end of the inductor L1 is connected to one end of the capacitor C2, one end of the resistor R2, and the charging terminal (2). The other end of the resistor R2 is connected to one end of the resistor R3 and the input terminal of the error amplifier (16). The other end of the resistor R3 and the other end of the capacitor C2 are grounded.

10. The lithium battery charging device according to claim 9, characterized in that: The power supply terminal (1) further includes an overheat protection module (8) and an undervoltage protection module (9); The charging terminal (2) includes a linear charging control module (3) connected to the power supply terminal (1). The linear charging control module (3) is adaptively connected to the lithium battery BT1. Through the linear charging control module (3), the power supply voltage output by the power supply terminal (1) can be collected, and the power supply voltage of the power supply terminal (1) and the voltage of the lithium battery BT1 can be compared to obtain the voltage difference between the power supply voltage of the power supply terminal (1) and the voltage of the lithium battery BT1. When the voltage difference is less than the preset voltage threshold VTH in the linear charging control module (3), the linear charging control module (3) stops charging the lithium battery BT1.

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