A charging circuit and a charging device

Abstract

The embodiment of the application provides a charging circuit and a charging device, which comprise a charging power supply, a first switch and a control unit; the charging power supply comprises at least one programmable constant voltage source, the first switch is connected between the charging power supply and a battery, and the control unit is connected with the charging power supply and the first switch respectively; wherein the control unit obtains a first control voltage for controlling the first switch or a second control voltage for controlling the programmable constant voltage source according to a target charging current, so as to control the size of the charging current, and the programmable constant voltage source constant current charging can be realized.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of charging, in particular to a charging circuit and a charging device. BACKGROUND

[0002] A rechargeable battery usually has pre-charging, constant current charging and constant voltage charging stages during the charging process. In the constant current charging stage, the charger generally adopts a closed-loop control strategy to control the output power according to the feedback of the output current, and generally uses a programmable constant current source to control the battery constant current charging. However, when there is no constant current source but constant current charging is needed, how to use a constant voltage source to achieve constant current charging is a problem that needs to be solved urgently. SUMMARY

[0003] Embodiments of the present application provide a charging circuit and a charging device, which can achieve constant current charging through a constant voltage source.

[0004] One technical solution adopted by the embodiments of the present application is to provide a charging circuit, comprising: a charging power supply, a first switch and a control unit.

[0005] The charging power supply comprises at least one programmable constant voltage source, the first switch is connected between the charging power supply and the battery, and the control unit is connected to the charging power supply and the first switch respectively.

[0006] The control unit is configured to:

[0007] obtain a target charging current;

[0008] obtain N-level first target currents according to the target charging current, N≥2, N being a positive integer;

[0009] In the i-th charging period, a first control voltage is periodically calculated according to the i-th first target current, or a second control voltage of each programmable constant voltage source is obtained;

[0010] The first switch is controlled according to the first control voltage, or the corresponding programmable constant voltage source is controlled according to the second control voltage, so as to control the charging current and charge the battery, 1≤i, i being a positive integer, and when i≥N, the i-th first target current is the target charging current.

[0011] In some embodiments, before the first charging period, the control unit is further configured to:

[0012] obtain a 0-th first target current according to the target charging current;

[0013] The first control voltage is periodically calculated according to the 0-th first target current, and the battery is charged for one charging period.

[0014] In some embodiments, the control unit is further configured to:

[0015] In each charging cycle, obtain a voltage of the battery, a first output voltage of the charging power supply, and a first actual charging current of the charging circuit;

[0016] According to the first output voltage and the first actual charging current, obtain a line loss of the charging circuit;

[0017] According to the first output voltage, the voltage of the battery, and the first actual charging current, obtain a battery internal resistance of the battery.

[0018] In some embodiments, in each charging cycle, the control unit is configured to obtain a first control voltage, or obtain a second control voltage of each of the programmable constant voltage sources, according to the first target current, comprising:

[0019] If the first target current of the i-th stage is less than or equal to a first current value, the control unit is configured to obtain the first control voltage according to the first target current of the i-th stage in each charging cycle;

[0020] If the first target current of the i-th stage is greater than the first current value, the control unit is configured to obtain the second control voltage according to the first target current of the i-th stage in each charging cycle.

[0021] In some embodiments, the control unit is configured to obtain the first control voltage according to the first target current of the 0-th stage in each charging cycle, and obtain the first control voltage according to the first target current of the i-th stage in each charging cycle, comprising:

[0022] In the charging cycle, obtain an ambient temperature and a second actual charging current of the charging circuit;

[0023] According to the first target current and the second actual charging current, obtain a first target current difference;

[0024] According to the first target current difference and the ambient temperature, obtain a first control voltage difference;

[0025] According to the first control voltage difference and the first control voltage obtained in the last calculation cycle, obtain the first control voltage in each charging cycle, or according to the first control voltage difference and a first control initial voltage, obtain the first control voltage.

[0026] In some embodiments, the control unit is further configured to obtain a battery temperature of the battery in the charging cycle;

[0027] For one of the programmable constant voltage sources, the control unit is configured to obtain the second control voltage according to the first target current in each charging cycle, comprising:

[0028] obtaining an output current of the programmable constant voltage source;

[0029] obtaining a second target current of the programmable constant voltage source according to the first target current;

[0030] obtaining a second output voltage of the charging circuit;

[0031] obtaining a second target current difference according to the second target current and the output current;

[0032] obtaining a second control voltage difference according to the second target current difference, the line loss obtained in the last charging period, and the battery internal resistance obtained in the last period;

[0033] obtaining a third control voltage by period calculation according to the second control voltage difference and the second output voltage;

[0034] if the battery voltage is greater than a constant current charging cutoff voltage, or the battery temperature is greater than or equal to a first temperature, taking a first voltage as the second control voltage corresponding to the programmable constant voltage source;

[0035] if the third control voltage is greater than or equal to a maximum output voltage of the programmable constant voltage source, taking the maximum output voltage as the second control voltage corresponding to the programmable constant voltage source;

[0036] if the third control voltage is less than the maximum output voltage, taking the third control voltage as the second control voltage corresponding to the programmable constant voltage source.

[0037] In some embodiments, the charging circuit includes at least two programmable constant voltage sources connected in parallel;

[0038] The obtaining of the second target current of the programmable constant voltage source according to the first target current includes:

[0039] obtaining a first number of the programmable constant voltage sources connected in parallel, and obtaining the second target current according to the first target current and the first number;

[0040] The obtaining of the third control voltage by period calculation according to the second control voltage difference and the second output voltage includes:

[0041] if the second control voltage difference is less than or equal to each maximum allowed voltage difference, taking the second control voltage difference as a ring voltage difference;

[0042] if the second control voltage difference is greater than the maximum allowed voltage difference, taking the maximum allowed voltage difference as the ring voltage difference;

[0043] acquiring a second actual charging current of the charging circuit;

[0044] obtaining a total ring voltage difference according to the first target current and the second actual charging current;

[0045] periodically calculating the third control voltage according to the partial ring voltage difference, the total ring voltage difference and the second output voltage.

[0046] In some embodiments, the charging circuit comprises at least two serially connected programmable constant voltage sources;

[0047] The periodically calculating the third control voltage according to the second control voltage difference and the second output voltage comprises:

[0048] acquiring a second number of the serially connected programmable constant voltage sources;

[0049] obtaining a third control voltage difference of each of the programmable constant voltage sources according to the second number and the second control voltage difference;

[0050] obtaining the third control voltage according to the third control voltage difference and the second output voltage.

[0051] In some embodiments, the charging circuit further comprises a second switch;

[0052] The second switch is connected in parallel with the first switch, and the second switch is further connected to the control unit.

[0053] In some embodiments, the charging circuit further comprises a voltage acquisition unit;

[0054] A first end of the voltage acquisition unit is connected to a first end of the first switch and a first end of the battery respectively, a second end of the voltage acquisition unit is connected to a first end of the charging power supply and a second end of the battery respectively, and a third end of the voltage acquisition unit is further connected to the control unit.

[0055] In some embodiments, the charging circuit further comprises at least one current acquisition unit;

[0056] Each of the current acquisition units is arranged in a loop formed between each of the programmable constant voltage sources, the first switch and the battery.

[0057] Each of the current acquisition units is further connected to the control unit.

[0058] In some embodiments, the charging circuit further comprises a first temperature acquisition unit and a second temperature acquisition unit;

[0059] The control unit is connected with the first temperature acquisition unit and the second temperature acquisition unit respectively, and is configured to acquire the temperature of the battery through the first temperature acquisition unit and acquire the ambient temperature through the second temperature acquisition unit.

[0060] In a second aspect, the embodiment of the present application provides a charging device, which comprises the charging circuit according to any one of the first aspect.

[0061] Compared with the prior art, the embodiment of the present application has the following beneficial effects: different from the prior art, the embodiment of the present application provides a charging circuit and a charging device, which comprise a charging power supply, a first switch and a control unit; the charging power supply comprises at least one programmable constant voltage source, the first switch is connected between the charging power supply and a battery, and the control unit is connected with the charging power supply and the first switch respectively; wherein the control unit is configured to: acquire a target charging current; obtain N levels of first target currents according to the target charging current, N≥2, and N is a positive integer; in the ith charging period, obtain a first control voltage or second control voltages of each programmable constant voltage source according to the ith first target current; control the first switch according to the first control voltage or control the corresponding programmable constant voltage source according to the second control voltage, so as to control the charging current and charge the battery, 1≤i, i is a positive integer, and when i≥N, the ith first target current is the target charging current. By adjusting and controlling the control voltage of the first switch or the programmable constant voltage source, the charging current is controlled, and the programmable constant voltage source constant current charging can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0062] The one or more embodiments are exemplarily described by pictures in the corresponding drawings, which do not constitute a limitation on the embodiments, and elements / modules and steps with the same reference numerals in the drawings represent similar elements / modules and steps, unless otherwise specified, and the drawings do not constitute a proportional limitation.

[0063] Figure 1 is a structural block diagram of a charging circuit provided by the embodiment of the present application;

[0064] Figure 2 is a schematic diagram of the relationship between the conduction current of an NMOS tube and a double-source voltage provided by the embodiment of the present application;

[0065] Figure 3 is an equivalent circuit diagram of a charging circuit provided by the embodiment of the present application;

[0066] Figure 4 is a charging control flowchart of a control unit provided by the embodiment of the present application;

[0067] Figure 5 is Figure 4A flowchart of step S130 in the method of charging the battery is shown in FIG. 13;

[0068] Figure 6 A structural block diagram of another charging circuit provided by an embodiment of the present application is shown in FIG. 14;

[0069] Figure 7 An equivalent circuit diagram of another charging circuit provided by an embodiment of the present application is shown in FIG. 15;

[0070] Figure 8 A structural block diagram of another charging circuit provided by an embodiment of the present application is shown in FIG. 16;

[0071] Figure 9 A charging control flowchart of another control unit provided by an embodiment of the present application is shown in FIG. 17;

[0072] Figure 10 A double-loop control system provided by an embodiment of the present application is shown in FIG. 18;

[0073] Figure 11 A structural block diagram of another charging circuit provided by an embodiment of the present application is shown in FIG. 19;

[0074] Figure 12 Another double-loop control system provided by an embodiment of the present application is shown in FIG. 20. DETAILED DESCRIPTION

[0075] The present application will be described in detail below with specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present application. These are within the scope of protection of the present application.

[0076] In order to facilitate understanding of the present application, the present application will be described in more detail below in conjunction with the drawings and specific embodiments. Unless otherwise defined, all technical and scientific terms used in the specification have the same meaning as understood by those skilled in the art. The terms used in the specification of the present application are only for the purpose of describing the specific embodiments and are not intended to limit the present application. The term "and / or" used in the specification includes any and all combinations of one or more related listed items.

[0077] It should be noted that the various features in the embodiments of the present application can be combined with each other without conflict, and are within the scope of protection of the present application. In addition, although the functional modules are divided in the device schematic diagram, in some cases, the module division in the device can be different. In addition, the "first", "second" and the like used herein do not limit the data and execution order, but only distinguish the same items or similar items with basically the same function and effect.

[0078] The embodiment of the present application provides a charging circuit, please refer to Figure 1 The charging circuit comprises a charging power supply 10, a first switch 20 and a control unit 30.

[0079] The charging power supply 10 comprises at least one programmable constant voltage source, the first switch 20 is connected between the charging power supply 10 and a battery 200, and the control unit 30 is connected to the charging power supply 10 and the first switch 20 respectively.

[0080] Specifically, please refer to Figure 1 The first end of the charging power supply 10 is connected to the first end of the first switch 20, the second end of the first switch 20 is connected to the second end of the battery 200, the second end of the charging power supply 10 is connected to the second end of the battery 200, and the charging power supply 10 and the first switch 20 are further connected to the control unit 30.

[0081] In the charging circuit, the output voltage Vs of the programmable constant voltage source can be regulated by the programmed voltage Vprog of the control unit 30, and the output voltage Vs of the programmable constant voltage source and the programmed voltage Vprog have the following relationship:

[0082] Vs=f(Vprog); (1)

[0083] Wherein, the function f represents the relationship between the output voltage Vs of the programmable constant voltage source and the programmed voltage Vprog, and the formula represented by the function f can be measured in practical application to the programmable constant voltage source.

[0084] Exemplarily, the first switch 20 can adopt a MOS tube. Please refer to Figure 2 When the MOS tube works in the amplification zone, the conduction current Id of the MOS tube and the voltage Vgs between the gate and the source and the ambient temperature Te have the following relationship:

[0085] Id=g(Vgs,Te); (2)

[0086] Wherein, the function g represents the relationship between the conduction current Id of the MOS tube and the voltage Vgs between the gate and the source, and the formula represented by the function g can be measured in practical application to the MOS tube. The MOS tube can adopt an NMOS tube or a PMOS tube, for example, when the first switch 20 adopts an NMOS tube, the source of the NMOS tube can be connected to the charging power supply, the drain of the NMOS tube can be connected to the battery, and the gate of the NMOS tube is connected to the control unit. It can be understood that for the NMOS tube in the amplification zone, the greater the voltage Vgs between the gate and the source, the greater the conduction current Id of the MOS tube, and for the PMOS tube in the amplification zone, the smaller the voltage Vgs between the gate and the source, the greater the conduction current Id of the MOS tube.

[0087] In this way, when the target charging current is small, for example, less than the saturation region current of the NMOS transistor, the charging current size can be controlled by controlling the gate-source voltage of the MOS transistor, at which time the charging circuit is as shown in FIG. 8. Figure 3 When the gate-source voltage exceeds a certain voltage range, for example, when the MOS transistor is in a saturated working state, the charging current size cannot be changed by continuously adjusting the gate-source voltage of the MOS transistor. Therefore, when the target charging current is large, for example, greater than the saturation region current of the MOS transistor, the charging current size can be controlled by controlling the output voltage of the charging power supply.

[0088] The battery can include only one cell or at least two cells connected in series and / or in parallel. It can be used to charge a power load, which can be a mobile phone, a drone, a car, etc.

[0089] The control unit can be an STM8, STM16 or STM32 series microcontroller, or any other suitable microcontroller that can be used to receive, process, store and output data.

[0090] The control unit is configured to perform the following steps: Figure 4

[0091] Step S110: obtaining a target charging current;

[0092] Specifically, the target charging current It is the required charging current size of the programmable constant voltage source during constant current charging.

[0093] Step S120: obtaining N levels of first target currents according to the target charging current, N≥2, N being a positive integer;

[0094] Specifically, after obtaining the target charging current It, the target charging current can be divided into N levels, for example, the first target current of the ith level is Ic=It*2i-N, when i≥N, the first target current of the ith level is the target charging current It. In actual applications, the size of the first target current of the ith level can be set according to actual needs, as long as the currents of each level are sequentially increased, and the change trend of the first target current of each level can be linear or curved, which is not limited herein.

[0095] It can be seen that, during the first N charging periods, the charging circuit is in a rising current stage, and when the first target current of the ith level is the target charging current It, the charging circuit is in a constant current stage.

[0096] Step S130: obtaining a first control voltage or a second control voltage of each programmable constant voltage source by periodically calculating the first target current of the ith level during the ith charging period;

[0097] ​In each charging cycle, a charging phase and a discharging phase are included, and during the charging process, the battery is periodically charged in a charge-stop manner so that energy is transmitted to the battery. It can be understood that, in the discharging phase, the control unit 30 controls the first switch 20 to be turned off, and the charging power supply 10 cannot charge the battery 200. The time occupied by the charging phase and the time occupied by the discharging phase in each cycle can be set according to actual needs, which is not limited herein.

[0098] Step S140: controlling the first switch according to the first control voltage or controlling the corresponding programmable constant voltage source according to the second control voltage to control the charging current and charge the battery, 1≤i, i is a positive integer, and when i≥N, the first target current of the i-th stage is the target charging current.

[0099] In the formula, Vgs is the gate-source voltage of the first switch 20, so that after the first control voltage Vgs is obtained, the first switch can be controlled, thereby controlling the size of the charging current. If the second control voltage Vs is obtained, the programming voltage of the programmable constant voltage source corresponding to the second control voltage Vs can be obtained through the inverse function of the function f, so that the control unit can control the programmable constant voltage source according to the programming voltage, thereby controlling the size of the charging current and realizing the constant current charging of the programmable constant voltage source.

[0100] In the charging circuit, the battery is charged by combining the rising current phase and the constant current phase, so that the charging current is more stable. In the charging circuit, in the case of small current, the charging current is regulated by using the amplification state of the MOS tube, that is, the size of the charging current is changed by changing the gate-source voltage of the MOS tube, and in the case of large current, the charging current is regulated by using the charging power supply, that is, the size of the charging current is changed by changing the programming voltage of the programmable constant voltage source, so that the programmable constant voltage source realizes the constant current charging of the battery, and the constant current charging can be realized without the need of a constant current source, which can reduce the cost of the charging power supply. In addition, different regulation methods are used under different target currents, which can improve the accuracy of the control current.

[0101] In some embodiments, referring to Figure 5 , the step S130 includes:

[0102] Step S131: if the first target current of the i-th stage is less than or equal to the first current value, the first control voltage is periodically calculated according to the first target current of the i-th stage;

[0103] Step S132: if the first target current of the i-th stage is greater than the first current value, each second control voltage is periodically calculated according to the first target current of the i-th stage.

[0104] Wherein, the first current value can be a MOS tube saturation region current, in practical application, the first current value can be determined by selecting different MOS tubes. In the charging circuit, in small current case, the MOS tube amplification state is used to control the output current, the charging current size is changed by changing the gate-source voltage of the MOS tube, in large current case, the charging current size is changed by changing the programming voltage of the programmable constant voltage source, and different control modes are used under different target currents, so that the accuracy of the controlled current can be improved.

[0105] In order to avoid the voltage drop caused by the current on the first switch in large current charging work, in some embodiments, please refer to Figure 6 The charging circuit further comprises a second switch 40. The second switch 40 is connected in parallel with the first switch 20, and the second switch 40 is further connected to the control unit. In this way, in large current case, the control unit can control the second switch 40 to be closed, so that the first switch 20 is short-circuited, and at this time, the charging circuit is equivalent to Figure 7 As shown, the voltage drop and heat caused by the large current on the first switch 20 can be avoided, and the charging efficiency is affected.

[0106] In some embodiments, please continue to refer to Figure 6 The charging circuit further comprises a voltage acquisition unit 60. The first end of the voltage acquisition unit 60 is connected to the first end of the first switch 20 and the first end of the battery 200 respectively, the second end of the voltage acquisition unit 60 is connected to the first end of the charging power supply 10 and the second end of the battery 200 respectively, and the third end of the voltage acquisition unit 60 is further connected to the control unit.

[0107] Specifically, the first end of the voltage acquisition unit is connected to the first end of the MOS tube and the first end of the battery respectively, and the second end of the voltage acquisition unit is connected to the first end of the charging power supply and the second end of the battery respectively. In this way, when the first switch and the second switch are opened, the control unit can obtain the voltage of the battery through the voltage acquisition unit, and when the first switch or the second switch is closed, the control unit can obtain the output voltage of the charging power supply through the voltage acquisition unit. It can be seen that by setting the voltage acquisition unit, the output voltage of the charging power supply and the battery voltage can be monitored. The voltage acquisition unit can adopt any suitable device for acquiring voltage in the prior art, which is not limited here.

[0108] In some embodiments, please continue to refer to Figure 6 The charging circuit further comprises at least one current acquisition unit 51. One current acquisition unit 51 is arranged in each loop formed between the programmable constant voltage source 11, the first switch 20 and the battery 200, and each current acquisition unit 51 is further connected to the control unit. The current acquisition unit can adopt any suitable device for acquiring current in the prior art, which is not limited here.

[0109] Specifically, please refer to Figure 6 The charging power supply 10 comprises a programmable constant voltage source 11, and a current acquisition unit 51 is arranged between the programmable constant voltage source 11 and the first switch 20 in the charging circuit. The current acquisition unit 51 is used to acquire the charging current in the charging circuit and transmit the charging current to the control unit.

[0110] Please refer to Figure 8 The charging power supply 10 comprises two programmable constant voltage sources 11 connected in parallel, and a current acquisition unit 51 is arranged between each programmable constant voltage source 11 and the first switch 20. Each current acquisition unit 51 is used to acquire the charging current in the charging circuit formed by each programmable constant voltage source 11, the first switch 20 and the battery 200, and transmit the charging current to the control unit.

[0111] It can be seen that by arranging the current acquisition unit in the charging circuit, the current output by each programmable constant voltage source can be monitored.

[0112] In some embodiments, the charging circuit further comprises a first temperature acquisition unit and a second temperature acquisition unit. The control unit is connected to the first temperature acquisition unit and the second temperature acquisition unit, respectively, and is used to acquire the temperature of the battery through the first temperature acquisition unit and acquire the ambient temperature through the second temperature acquisition unit. The first temperature acquisition unit and the second temperature acquisition unit can be temperature sensors, and the first temperature acquisition unit is arranged close to the battery and can be used to detect the temperature of the battery in real time.

[0113] In some embodiments, please refer to Figure 9 Before the first charging cycle, the control unit is further used to perform the following steps:

[0114] Step S111: obtaining the first target current of the 0th level according to the target charging current;

[0115] Step S112: periodically calculating the first control voltage according to the first target current of the 0th level to charge the battery for one charging cycle.

[0116] Specifically, after obtaining the target charging current It, the first target current Ic of the 0th level can be obtained, such as Ic = It / 4. In actual application, it is only required to ensure that the first target current Ic of the 0th level is less than the charging safety current or the saturation region current of the MOS tube, and the limitation in this embodiment does not need to be strictly followed.

[0117] So, in the charging circuit, the control unit uses the first target current of the 0th stage to charge the battery for one charging period, so that the charging circuit is in a preparation stage, and initial parameters in the charging circuit, such as the battery internal resistance and the line loss, can be obtained. It should be noted that, in the case of small current, when the circuit equivalent diagram is as shown in Figure 3 , the calculated line loss includes the line loss resistance on the first switch 20.

[0118] Specifically, in some embodiments, the control unit is further configured to obtain the voltage of the battery, the first output voltage of the charging power supply, and the first actual charging current of the charging circuit in each charging period; obtain the line loss of the charging circuit according to the first output voltage and the first actual charging current; and obtain the battery internal resistance of the battery according to the first output voltage, the voltage of the battery, and the first actual charging current.

[0119] Specifically, please refer to Figure 6 , in each charging period, the control unit controls the first switch 20 and the second switch 40 to be both open, and then obtains the battery voltage Vb through the voltage acquisition unit 60. Next, in each charging period, the control unit controls the first switch 20 or the second switch 40 to be closed, and then obtains the first output voltage Vo1 of the charging power supply 10 through the voltage acquisition unit 60, and obtains the first actual charging current I1 flowing through the battery 300 through the current acquisition unit 51, and then the line loss Rc of the charging circuit can be obtained according to the following formula:

[0120] Vo1 = Vs - I1 * Rc; (3)

[0121] and the battery internal resistance Rb can be obtained according to the following formula:

[0122] Rb = (Vo1 - Vb) / I1; (4)

[0123] wherein Vs is the output voltage of the programmable constant voltage source 11.

[0124] In order to improve the accuracy of the data, the battery voltage should be obtained at the same time point in each charging period, and in addition, the line loss and the battery internal resistance are usually calculated when each charging period is about to end. In the above manner, the battery voltage, the line loss of the charging circuit, and the battery internal resistance in each charging period can be calculated.

[0125] In some embodiments, the first control voltage is calculated according to the first target current in the 0th stage, and the first control voltage is calculated according to the first target current in the ith stage, including: obtaining the ambient temperature and the second actual charging current of the charging circuit in the charging period; obtaining a first target current difference according to the first target current and the second actual charging current; obtaining a first control voltage difference according to the first target current difference and the ambient temperature; calculating the first control voltage according to the first control voltage difference and the first control voltage obtained in the last calculation period, or obtaining the first control voltage according to the first control voltage difference and a first control initial voltage.

[0126] As known from the foregoing, when the MOS transistor is in the amplification region, the conduction current of the MOS transistor is related to the ambient temperature Te and the gate-source voltage Vgs. Therefore, the control unit can obtain the ambient temperature Te through the second temperature acquisition unit and the second actual charging current output by the programmable constant voltage source through the current acquisition unit, and obtain the gate-source voltage Vgs, i.e., the first control voltage, which needs to be controlled by the MOS transistor.

[0127] Specifically, please refer to Figure 6 and Figure 10 In each charging period, the ambient temperature Te is obtained through the second temperature acquisition unit, and the second actual charging current I2 of the charging circuit is obtained through the current acquisition unit 51. Then, the first target current difference ΔI1 is obtained according to the following formula:

[0128] ΔI1 = Ic - I2 (5)

[0129] Then, since the first target current difference ΔI1 is less than or equal to the conduction current of the MOS transistor, the first control voltage difference ΔVgs can be obtained according to the following formula:

[0130] ΔVgs = g -1 (ΔI1, Te) (6)

[0131] Therefore, the first control voltage Vgs is:

[0132] Vgs = Vgs' + ΔVgs (7)

[0133] Wherein, Vgs' is the first control voltage obtained in the last calculation period or the first control initial voltage.

[0134] It should be noted that, when the first control voltage is calculated in the initial charging stage, there is no charging state, i.e. the first actual charging current I2 is 0 A and the Vgs' of the first calculation period is 0 V. Finally, in each charging period, the first control voltage is calculated repeatedly in the above manner, and the first control voltage is calculated periodically. The time of the calculation period can be 10 ms or other time, which is not limited here.

[0135] In some embodiments, the control unit is further configured to obtain a battery temperature of the battery in the charging period. For one of the programmable constant voltage sources, the periodically calculating the second control voltage according to the first target current comprises: obtaining an output current of the programmable constant voltage source; obtaining a second target current of the programmable constant voltage source according to the first target current; obtaining a second output voltage of the charging circuit; obtaining a second target current difference according to the second target current and the output current; obtaining a second control voltage difference according to the second target current difference, the line loss obtained in the last charging period, and the battery internal resistance obtained in the last charging period; periodically calculating a third control voltage according to the second control voltage difference and the second output voltage; if the battery voltage is greater than the constant current charging cutoff voltage, or the battery temperature is greater than or equal to a first temperature, taking a first voltage as the second control voltage of the programmable constant voltage source; if the third control voltage is greater than or equal to a maximum output voltage of the programmable constant voltage source, taking the maximum output voltage as the second control voltage of the programmable constant voltage source; if the third control voltage is less than the maximum output voltage, taking the third control voltage as the second control voltage of the programmable constant voltage source.

[0136] Specifically, please refer to Figure 6 and Figure 10 In each charging period, the battery temperature Tb of the battery is obtained by the first temperature acquisition unit, the battery voltage Vb is obtained by the voltage acquisition unit 60, and the output current Io of the corresponding programmable constant voltage source is obtained by the current acquisition unit 51.

[0137] In the charging period, the second target current difference ΔI2 is obtained according to the following formula:

[0138] ΔI2 = Ic2 - Io; (8)

[0139] Wherein, Ic2 is the second target current, and Io is the output current of the programmable constant voltage source.

[0140] It can be understood that, in the embodiment shown in Figure 6 , the charging power supply 10 has only one programmable constant voltage source 11, or in the embodiment shown in Figure 11In the shown embodiment, the charging power supply 10 includes a plurality of programmable constant voltage sources 11 connected in series, and the second target current Ic2 of each programmable constant voltage source 11 is the first target current Ic, and the output current Io of the programmable constant voltage source is the second actual charging current I2. Figure 8 In the shown embodiment, the charging power supply 10 includes a plurality of programmable constant voltage sources 11 connected in parallel, and the second target current Ic2 of each programmable constant voltage source 11 is the quotient of the first target current Ic and the first number M1 of the programmable constant voltage source, i.e., Ic2=Ic / M1, and the second actual charging current Ic2 is the sum of the output currents Io of the programmable constant voltage sources.

[0141] Next, the second output voltage Vo2 of the charging circuit is obtained by the voltage acquisition unit, and the second control voltage difference AV is obtained according to the following formula:

[0142] AV=AI2*(Rb+Rc) (9)

[0143] wherein Rb is the battery internal resistance obtained in the last charging period, and Rc is the line loss obtained in the last charging period, and the third control voltage Vt is obtained according to the following formula:

[0144] Vt=Vo2+AV (10)

[0145] After the third control voltage is obtained, the third control voltage needs to be judged to determine the voltage size Vs that the programmable constant voltage source needs to finally output, i.e., the second control voltage Vs:

[0146]

[0147] wherein Vbmax is the constant current charging cutoff voltage, Tbmax is the first temperature, which can be the highest temperature allowed under safe charging, and Vsmax is the maximum output voltage of the programmable constant voltage source.

[0148] Finally, after the second control voltage Vs is obtained, the programming voltage Vprog of the programmable constant voltage source is obtained according to the following formula:

[0149] Vprog=f -1 (Vs) (12)

[0150] In summary, through the algorithm of the combined control of the current loop and the voltage loop, the first control voltage and the second control voltage can be obtained to control the first switch and the charging power supply.

[0151] Specifically, the specific process of the charging circuit provided by the embodiment of the present application is described in detail below with reference to the shown embodiment. Figure 6

[0152] ​In the preparation stage, first, the first switch 20 and the second switch 40 are both disconnected, then the battery voltage Vb is acquired by the voltage acquisition unit 60, the battery temperature Tb is acquired by the first temperature acquisition unit, and the ambient temperature Te is acquired by the second temperature acquisition unit.

[0153] At this time, the first target current Ic of the 0th stage is It / 4, then the first control voltage Vgs and the second control voltage Vs are obtained by the double-loop control system shown in FIG. 2, and in the charging period, the first control voltage Vgs and the second control voltage Vs are repeatedly calculated according to the above steps, and the calculation period time can be 10 ms. Since the charging power supply does not output current at the beginning, the initial first target current difference is Ic, and the first control initial voltage Vgs' = 0V. In addition, since the first target current difference is always less than the saturation conduction current of the MOS tube at this stage, the second control voltage difference ΔV needs to be assigned to obtain the second control voltage Vs, for example, the second control voltage difference ΔV = 0.3V. Figure 10 Finally, at the end of the charging stage of each charging period, the output voltage Vo1 of the programmable constant voltage source 11 is acquired by the voltage acquisition unit 60, and the first actual charging current I1 flowing through the battery 300 is acquired by the current acquisition unit 51, and the battery internal resistance Rb and the line loss Rc are obtained by formulas (3) and (4).

[0154] In each charging period in the rising current charging stage, similarly, first, when the first switch 20 and the second switch 40 are both disconnected, the battery voltage Vb is acquired by the voltage acquisition unit 60, the battery temperature Tb is acquired by the first temperature acquisition unit, and the ambient temperature Te is acquired by the second temperature acquisition unit. According to the first target charging current of each stage, the first control voltage Vgs and the second control voltage Vs are obtained by the double-loop control system shown in FIG. 2, and in the charging period, the first control voltage Vgs and the second control voltage Vs are repeatedly calculated according to the above steps, and the calculation period time can be 10 ms. Finally, at the end of the charging stage of each charging period, the output voltage Vo1 of the programmable constant voltage source 11 is acquired by the voltage acquisition unit 60, and the first actual charging current I1 flowing through the battery 300 is acquired by the current acquisition unit 51, and the battery internal resistance Rb and the line loss Rc are obtained by formulas (3) and (4).

[0155] Figure 10 Finally, at the end of the charging stage of each charging period, the output voltage Vo1 of the programmable constant voltage source 11 is acquired by the voltage acquisition unit 60, and the first actual charging current I1 flowing through the battery 300 is acquired by the current acquisition unit 51, and the battery internal resistance Rb and the line loss Rc are obtained by formulas (3) and (4).

[0156] ​Finally, in the constant current charging phase, in each cycle, similarly, first, when the first switch 20 and the second switch 40 are both disconnected, the battery voltage Vb is obtained by the voltage acquisition unit 60, the battery temperature Tb is obtained by the first temperature acquisition unit, and the ambient temperature Te is obtained by the second temperature acquisition unit. According to the first target charging current of each level, the first control voltage Vgs and the second control voltage Vs are obtained by the formula (5) to the formula (11), and in the charging cycle, the first control voltage Vgs and the second control voltage Vs are repeatedly calculated according to the above steps, and the calculation cycle time can be 10 ms. Finally, at the end of each charging cycle, the output voltage Vo1 of the programmable constant voltage source 11 is obtained by the voltage acquisition unit 60, and the first actual charging current I1 flowing through the battery 300 is obtained by the current acquisition unit 51, and the battery internal resistance Rb and the line loss Rc are obtained by the formula (3) and the formula (4). Figure 10 The double-loop control system shown in the formula (5) to the formula (11) is used to charge the battery in one cycle, that is, the first control voltage Vgs and the second control voltage Vs are obtained by the formula (5) to the formula (11), and in the charging cycle, the first control voltage Vgs and the second control voltage Vs are repeatedly calculated according to the above steps, and the calculation cycle time can be 10 ms. Finally, at the end of each charging cycle, the output voltage Vo1 of the programmable constant voltage source 11 is obtained by the voltage acquisition unit 60, and the first actual charging current I1 flowing through the battery 300 is obtained by the current acquisition unit 51, and the battery internal resistance Rb and the line loss Rc are obtained by the formula (3) and the formula (4).

[0157] In summary, it can be seen that the charging circuit provided by the embodiment of the application can realize constant current charging of the battery by using the programmable constant voltage source, and can reduce the power supply cost. In each stage, the double-loop control is performed by the current loop and the voltage loop, the architecture is unified, the process is simple, the control accuracy and safety can be improved. In addition, the control strategies used in different current levels are different, and the accuracy of the control current can be provided.

[0158] In some embodiments, please refer to Figure 8 When the charging circuit includes at least two programmable constant voltage sources connected in parallel, the second target current corresponding to the programmable constant voltage source is obtained according to the first target current, including: obtaining the first number of the programmable constant voltage sources connected in parallel, and obtaining the second target current according to the first target current and the first number.

[0159] Specifically, the control unit obtains the first number M1 of the programmable constant voltage sources connected in parallel, and the second target current Ic2 of one of the programmable constant voltage sources is Ic / M1. Then, the second target current difference ΔI2 at this time is Ic2-Io=(Ic / M1)-Io, and then the second control voltage difference ΔV can be obtained according to the formula (9).

[0160] The third control voltage is periodically calculated according to the second control voltage difference and the second output voltage, and comprises: if the second control voltage difference is less than or equal to the maximum allowable voltage difference of each programmable constant voltage source, the second control voltage difference is taken as a partial ring voltage difference; if the second control voltage difference is greater than the maximum allowable voltage difference, the maximum allowable voltage difference is taken as the partial ring voltage difference; a second actual charging current of the charging circuit is obtained; a total ring voltage difference is obtained according to the first target current and the second actual charging current; and the third control voltage is periodically calculated according to the partial ring voltage difference, the total ring voltage difference and the second output voltage.

[0161] Specifically, please refer to Figure 8 and Figure 12 For one of the programmable constant voltage sources 11, after the second control voltage difference ΔV is obtained according to the foregoing formula (9), since each programmable constant voltage source is in a parallel connection mode, it is required to ensure that the voltages output by each programmable constant voltage source are consistent in an ideal case, and in actual application, the voltage difference between each programmable constant voltage source is allowed to be within a certain range, which is the maximum allowable voltage difference ΔVsmax of each programmable constant voltage source, and then the partial ring voltage difference ΔV(i) of one of the programmable constant voltage sources 11 can be obtained according to the following formula:

[0162]

[0163] Then, the second actual charging current I2 of the charging circuit is obtained, which can be obtained by adding the output currents Io flowing through each programmable constant voltage source, or a current collection unit can be arranged in the total charging circuit to obtain the total charging current in the total charging circuit, that is, the second actual charging current I2.

[0164] After the second actual charging current I2 is obtained, the total ring target current difference ΔIa is obtained according to the following formula:

[0165] ΔIa = Ic - I2; (14)

[0166] Then, the total ring voltage difference ΔVa is obtained through the following formula similar to formula (9):

[0167] ΔVa = ΔIa * (Rb + Rc); (15)

[0168] Then, the third control voltage Vt is:

[0169] Vt = V + ΔV(i) + ΔVa; (16)

[0170] After the third control voltage Vt is obtained, the second control voltage Vs is obtained according to formula 11, and finally the programming voltage Vprog of one of the programmable constant voltage sources is obtained through formula 12.

[0171] In summary, the above-mentioned method can be used to realize constant current charging of the battery by connecting multiple programmable constant voltage sources in parallel. By connecting multiple programmable constant voltage sources in parallel, the output current of the charging power supply can be improved, thereby improving the output power of the charging power supply to meet the charging demand.

[0172] In some embodiments, referring to Figure 11 The charging circuit includes at least two programmable constant voltage sources connected in series. The periodic calculation of the third control voltage according to the second control voltage difference and the second output voltage includes: obtaining a second number of the programmable constant voltage sources connected in series; obtaining a third control voltage difference of each programmable constant voltage source according to the second number and the second control voltage difference; and obtaining the third control voltage according to the third control voltage difference and the second output voltage.

[0173] Specifically, after obtaining the second control voltage difference ΔV according to the formula (8) and the formula (9), the third control voltage Vt is obtained by the following formula:

[0174] Vt=V+ΔV / M2; (17)

[0175] After obtaining the third control voltage Vt, the second control voltage Vs is obtained according to the formula 11, and finally the programming voltage Vprog of one of the programmable constant voltage sources is obtained by the formula 12.

[0176] In summary, the above-mentioned method can be used to realize constant current charging of the battery by connecting multiple programmable constant voltage sources in parallel. By connecting multiple programmable constant voltage sources in parallel, the output current of the charging power supply can be improved, thereby improving the output power of the charging power supply to meet the charging demand.

[0177] In a second aspect, the embodiments of the present application also provide a charging device, which includes the charging circuit according to any one of the first aspect. The charging device can realize constant current charging by using programmable constant voltage sources, thereby reducing the cost of the charging power supply.

[0178] It should be noted that the apparatus embodiments described above are only schematic and that the units as described above can or can not be physically separate units. The units as displayed can or can not be physical units; that is, some or all of the units can be located in one place or distributed over multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiments.

[0179] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not limited to them; under the idea of the present application, the technical features of the above examples or different examples can also be combined, the steps can be implemented in any order, and there are many other changes of different aspects of the present application as described above, which are not provided in details for simplicity; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A charging circuit, characterized in that, include: Charging power supply, first switch, and control unit; The charging power supply includes at least one programmable constant voltage source, the first switch is connected between the charging power supply and the battery, and the control unit is connected to the charging power supply and the first switch respectively. The control unit is used for: Obtain the target charging current; Based on the target charging current, the first target current of level N is obtained, where N≥2 and N is a positive integer; During the i-th charging cycle, the first control voltage or the second control voltage of each programmable constant voltage source is calculated periodically based on the first target current of the i-th stage. The first switch is controlled according to the first control voltage, or the corresponding programmable constant voltage source is controlled according to the second control voltage to control the charging current to charge the battery, where 1≤i, i is a positive integer, and when i≥N, the first target current of the i-th stage is the target charging current.

2. The charging circuit according to claim 1, characterized in that, Before the first charging cycle, the control unit is further configured to: Based on the target charging current, the first target current for level 0 is obtained; Based on the first target current at level 0, the first control voltage is calculated periodically, and the battery is charged for one charging cycle.

3. The charging circuit according to claim 2, characterized in that, The control unit is also used for: During each charging cycle, the voltage of the battery, the first output voltage of the charging power supply, and the first actual charging current of the charging circuit are obtained. The line loss of the charging circuit is obtained based on the first output voltage and the first actual charging current. The internal resistance of the battery is obtained based on the first output voltage, the voltage of the battery, and the first actual charging current.

4. The charging circuit according to claim 3, characterized in that, Within each charging cycle, the cycle calculation yields either a first control voltage or a second control voltage for each of the programmable constant voltage sources, including: If the first target current of the i-th stage is less than or equal to the first current value, then the first control voltage is calculated periodically based on the first target current of the i-th stage. If the first target current of the i-th stage is greater than the first current value, then the second control voltage is periodically calculated based on the first target current of the i-th stage.

5. The charging circuit according to claim 4, characterized in that, The step of periodically calculating the first control voltage based on the first target current at level 0, and the step of periodically calculating the first control voltage based on the first target current at level i, include: During the charging cycle, the ambient temperature and the second actual charging current of the charging circuit are obtained; The first target current difference is obtained based on the first target current and the second actual charging current; The first control voltage difference is obtained based on the first target current difference and the ambient temperature; The first control voltage is calculated periodically based on the first control voltage difference and the first control voltage obtained in the previous calculation cycle, or the first control voltage is obtained based on the first control voltage difference and the first initial control voltage.

6. The charging circuit according to claim 4, characterized in that, The control unit is also used to acquire the battery temperature of the battery during the charging cycle; For one of the programmable constant voltage sources, the step of periodically calculating each of the second control voltages based on the first target current includes: Obtain the output current of the programmable constant voltage source; Based on the first target current, the corresponding second target current of the programmable constant voltage source is obtained; Obtain the second output voltage of the charging circuit; The second target current difference is obtained based on the second target current and the output current; The second control voltage difference is obtained based on the second target current difference, the line loss obtained in the previous charging cycle, and the battery internal resistance obtained in the previous charging cycle. The third control voltage is calculated periodically based on the second control voltage difference and the second output voltage. If the battery voltage is greater than the constant current charging cutoff voltage, or if the battery temperature is greater than or equal to the first temperature, then the first voltage is used as the second control voltage corresponding to the programmable constant voltage source. If the third control voltage is greater than or equal to the maximum output voltage of the programmable constant voltage source, then the maximum output voltage is used as the second control voltage corresponding to the programmable constant voltage source. If the third control voltage is less than the maximum output voltage, then the third control voltage is used as the second control voltage corresponding to the programmable constant voltage source.

7. The charging circuit according to claim 6, characterized in that, The charging circuit includes at least two programmable constant voltage sources connected in parallel. The step of obtaining the corresponding second target current of the programmable constant voltage source based on the first target current includes: Obtain the first number of the parallel-connected programmable constant voltage sources, and obtain the second target current based on the first target current and the first number; The step of periodically calculating the third control voltage based on the second control voltage difference and the second output voltage includes: If the second control voltage difference is less than or equal to the maximum allowable voltage difference of each programmable constant voltage source, then the second control voltage difference is used as the loop voltage difference; If the second control voltage difference is greater than the maximum allowable voltage difference, then the maximum allowable voltage difference shall be used as the loop voltage difference; Obtain the second actual charging current of the charging circuit; The total loop voltage difference is obtained based on the first target current and the second actual charging current; The third control voltage is calculated periodically based on the sub-loop voltage difference, the total loop voltage difference, and the second output voltage.

8. The charging circuit according to claim 6, characterized in that, The charging circuit includes at least two programmable constant voltage sources connected in series. The step of periodically calculating the third control voltage based on the second control voltage difference and the second output voltage includes: Obtain the second number of the series-connected programmable constant voltage sources; Based on the second number and the second control voltage difference, the third control voltage difference of each programmable constant voltage source is obtained; The third control voltage is obtained based on the third control voltage difference and the second output voltage.

9. The charging circuit according to claim 1, characterized in that, The charging circuit also includes a second switch; The second switch is connected in parallel with the first switch, and the second switch is also connected to the control unit.

10. The charging circuit according to claim 1, characterized in that, The charging circuit also includes a voltage acquisition unit; The first end of the voltage acquisition unit is connected to the first end of the first switch and the first end of the battery, the second end of the voltage acquisition unit is connected to the first end of the charging power supply and the second end of the battery, and the third end of the voltage acquisition unit is also connected to the control unit.

11. The charging circuit according to claim 1, characterized in that, The charging circuit also includes at least one current acquisition unit; In the circuit formed between each programmable constant voltage source, the first switch and the battery, a current acquisition unit is provided; Each of the current acquisition units is also connected to the control unit.

12. The charging circuit according to claim 1, characterized in that, The charging circuit also includes a first temperature acquisition unit and a second temperature acquisition unit. The control unit is connected to the first temperature acquisition unit and the second temperature acquisition unit respectively. The control unit is used to acquire the battery temperature through the first temperature acquisition unit and to acquire the ambient temperature through the second temperature acquisition unit.

13. A charging device, characterized in that, Includes the charging circuit as described in any one of claims 1-12.

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