CN111934404B - Charging circuit - Google Patents

Charging circuit Download PDF

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Publication number
CN111934404B
CN111934404B CN202011104718.7A CN202011104718A CN111934404B CN 111934404 B CN111934404 B CN 111934404B CN 202011104718 A CN202011104718 A CN 202011104718A CN 111934404 B CN111934404 B CN 111934404B
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voltage
current
charging
constant
charged
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CN111934404A (en
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王本川
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Beijing Thinking Semiconductor Technology Co ltd
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Beijing Thinking Semiconductor Technology Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0029—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries with safety or protection devices or circuits
    • H02J7/00302—Overcharge protection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage

Abstract

The present disclosure relates to a charging circuit, including: the constant-voltage charging module is connected with the constant-current charging module; the constant-voltage charging module is used for acquiring the current voltage of the device to be charged, determining whether the current voltage of the device to be charged is smaller than a reference voltage or not, and generating a control instruction for instructing the constant-current charging module to perform constant-current charging on the device to be charged under the condition that the current voltage is smaller than the reference voltage; the constant current charging module is used for responding to the control instruction and carrying out constant current charging on the device to be charged according to the constant charging current. Therefore, the charging termination voltage of the device to be charged can be accurately controlled by using the simple LDO structure, and the purpose of fully utilizing the capacity of the device to be charged without overshoot is achieved. Moreover, the purpose of controllable charging current is realized, and the problem that the service life of the device to be charged is influenced by overhigh internal temperature due to overlarge current at the initial charging stage can be effectively avoided.

Description

Charging circuit
Technical Field
The present disclosure relates to the field of integrated circuit design technologies, and in particular, to a charging circuit.
Background
In the broadband power line carrier HPLC communication module, a super capacitor charge-discharge management mechanism is needed to realize the function of reporting power failure. The charging of the super capacitor generally adopts a Constant Current (CC) and Constant Voltage (CV) charging mode, which adopts a constant large current charging mode at the initial charging stage, when the capacitor voltage reaches a preset charging termination voltage, the charging current is reduced to zero at the moment, and the preset charging termination voltage is maintained unchanged, i.e. the constant current mode is switched to the constant voltage mode.
However, in the related art, constant voltage charging of a device to be charged (e.g., a supercapacitor) can only be achieved. In the related art, when a device to be charged is charged at a constant voltage, a special charging chip needs to be added, and the special charging chip plays a role in protection when the device to be charged is in overvoltage, but the chip has high cost, and the purpose of charging the device to be charged at a constant current cannot be realized.
Disclosure of Invention
An object of the present disclosure is to provide a charging circuit to solve the problems in the related art.
In order to achieve the above object, the present disclosure provides a charging circuit including: the constant-voltage charging system comprises a constant-voltage charging module and a constant-current charging module, wherein the constant-voltage charging module is connected with the constant-current charging module;
the constant voltage charging module is used for acquiring the current voltage of the device to be charged, determining whether the current voltage of the device to be charged is smaller than a reference voltage, and generating a control instruction for instructing the constant current charging module to perform constant current charging on the device to be charged under the condition that the current voltage is smaller than the reference voltage;
and the constant current charging module is used for responding to the control instruction and carrying out constant current charging on the device to be charged according to the constant charging current.
Optionally, the constant-voltage charging module includes a comparing unit and a shunt branch, wherein the comparing unit is connected to the shunt branch, and the shunt branch is connected in parallel to the device to be charged;
the comparison unit is used for determining whether the current voltage of the device to be charged is smaller than the reference voltage or not, and controlling the shunt branch to be disconnected under the condition that the current voltage is smaller than the reference voltage, so that the constant current charging module performs constant current charging on the device to be charged according to the constant charging current.
Optionally, the comparing unit is further configured to control the shunting branch to be turned on to shunt the constant charging current through the shunting branch when it is determined that the present voltage is greater than or equal to the reference voltage;
and the constant-current charging module is also used for carrying out constant-voltage charging on the device to be charged according to the shunted charging current.
Optionally, the comparison unit is an operational amplifier, and the shunt branch is a first N-type MOS transistor;
the non-inverting input end of the operational amplifier is connected with the voltage input end of the device to be charged so as to obtain the current voltage of the device to be charged, and the inverting input end of the operational amplifier is connected with the reference voltage end so as to obtain the reference voltage of the device to be charged;
the grid electrode of the first N-type MOS tube is connected with the output end of the operational amplifier, the drain electrode of the first N-type MOS tube is connected with the constant current charging module, and the source electrode of the first N-type MOS tube is grounded.
Optionally, the constant current charging module includes: the power supply comprises a power supply source, a current bias circuit, a second N-type MOS tube, a third N-type MOS tube, a first P-type MOS tube and a second P-type MOS tube;
one end of the current bias circuit is connected with the power supply to generate the constant charging current;
the other end of the current bias circuit is respectively connected with the constant-voltage charging module, the drain electrode and the grid electrode of the second N-type MOS tube and the grid electrode of the third N-type MOS tube;
the source electrode of the second N-type MOS tube is grounded with the source electrode of the third N-type MOS tube;
the drain electrode of the third N-type MOS tube is connected with the drain electrode and the grid electrode of the first P-type MOS tube and the grid electrode of the second P-type MOS tube;
the source electrode of the first P-type MOS tube and the source electrode of the second P-type MOS tube are both connected with the power supply;
and the drain electrode of the second P-type MOS tube is connected with the device to be charged and is used for carrying out constant current charging on the device to be charged according to the constant charging current.
Optionally, in a constant current charging stage, a target charging current of the device to be charged is a product of the constant charging current and a first proportionality coefficient and a second proportionality coefficient, where the first proportionality coefficient is a current mirror proportionality coefficient of the third N-type MOS transistor and the second N-type MOS transistor, and the second proportionality coefficient is a current mirror proportionality coefficient of the second P-type MOS transistor and the first P-type MOS transistor.
Optionally, the charging circuit further comprises: the voltage feedback module is connected with the constant voltage charging module;
the voltage feedback module is used for being connected with the device to be charged so as to generate an electric signal for representing the current voltage of the device to be charged;
the constant voltage charging module is further used for obtaining the current voltage of the device to be charged according to the electric signal.
Optionally, the voltage feedback module includes a first resistor, a second resistor, and a voltage detection device, where the voltage detection device is connected to the constant voltage charging module;
one end of the first resistor is connected with the device to be charged, the other end of the first resistor is connected with one end of the second resistor, and the other end of the second resistor is grounded;
the voltage detection device is used for detecting the voltage of the first resistor and/or the second resistor, determining the current voltage of the device to be charged according to the detected voltage, and generating an electric signal for representing the current voltage of the device to be charged.
Optionally, the constant voltage charging module includes an operational amplifier, and the voltage feedback module includes a first resistor and a second resistor;
one end of the first resistor is connected with the device to be charged, the other end of the first resistor is connected with the non-inverting input end of the operational amplifier and one end of the second resistor respectively, the other end of the second resistor is grounded, and the inverting input end of the operational amplifier is connected with a reference voltage end so as to obtain the reference voltage of the device to be charged.
Optionally, the reference voltage is less than a rated voltage of the device to be charged.
Through the technical scheme, when the current voltage of the device to be charged is smaller than the reference voltage, the device to be charged is subjected to constant current charging according to the constant charging current. Therefore, the charging termination voltage of the device to be charged can be accurately controlled by using a simple LDO (low dropout regulator) structure, and the purpose of fully utilizing the capacity of the device to be charged without overshoot is achieved. In addition, in the constant-current charging process, the charging current can be set according to actual requirements, the purpose of controllable charging current is achieved, the problem that the service life of the charging device is influenced by overhigh internal temperature caused by overlarge current in the initial charging stage can be effectively avoided, and the service life of the charging device is prolonged.
Additional features and advantages of the disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure without limiting the disclosure.
Fig. 1 is a schematic diagram illustrating a related art charging circuit according to an example embodiment.
Fig. 2 is a block diagram illustrating a charging circuit in accordance with an example embodiment.
Fig. 3 is a schematic diagram illustrating a charging circuit in accordance with an exemplary embodiment.
Fig. 4 is a schematic diagram illustrating another charging circuit in accordance with an example embodiment.
Detailed Description
The following detailed description of specific embodiments of the present disclosure is provided in connection with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present disclosure, are given by way of illustration and explanation only, not limitation.
The charging circuit in the related art includes: the power supply comprises an operational amplifier, a voltage feedback module, a power supply VDD and a power tube MP. The voltage feedback module is connected with the super capacitor Csuper in parallel and used for feeding back the voltage of the super capacitor Csuper to the operational amplifier. Illustratively, fig. 1 is a schematic diagram illustrating a charging circuit in a related art according to an exemplary embodiment. As shown in fig. 1, the voltage feedback module includes a first resistor R1 and a second resistor R2, one end of the first resistor R1 is connected to the super capacitor Csuper, the other end of the first resistor R1 is connected to the non-inverting terminal of the operational amplifier and one end of the second resistor R2, and the other end of the second resistor R2 is grounded. Therefore, the voltage VFB input by the in-phase end of the operational amplifier can represent the charging voltage of the super capacitor Csuper, the voltage input by the inverting end of the operational amplifier is the reference voltage VREF, the output end of the operational amplifier is connected with the grid electrode of the power tube MP, the source electrode of the power tube MP is connected with the power supply VDD, the drain electrode of the power tube MP is connected with one end of the super capacitor Csuper, so that the power supply charges the super capacitor Csuper, and the charging current is Ich.
In fig. 1, VFB is proportional to the charging voltage VC of the super capacitor Csuper, and the relationship between the two satisfies the following formula: VFB = (R2/(R1 + R2)) × VC, and accordingly, in order to prevent the problem of damage due to the charging voltage VC of the super capacitor Csuper being higher than its rated voltage, in the charging circuit shown in fig. 1, the above-mentioned reference voltage VREF may be less than or equal to the product of the rated voltage of the super capacitor Csuper and R2/(R1 + R2). When the VFB is greater than or equal to VREF, the power tube MP is not turned on, and at this time, the power supply VDD stops charging the super capacitor Csuper. When VFB is smaller than VREF, the power tube MP is conducted, and at the moment, the power supply VDD charges the super capacitor Csuper. Therefore, the charging termination voltage of the super capacitor Csuper can be accurately controlled through the charging circuit.
It should be noted that the charging voltage of the super capacitor Csuper can also be directly used as the input voltage of the non-inverting terminal of the operational amplifier, and thus, the reference voltage VREF may be the rated voltage of the super capacitor Csuper or a voltage slightly smaller than the rated voltage. The present disclosure does not specifically limit this.
However, charging the super capacitor Csuper directly with the power supply based on the LDO architecture may cause the following problems: (1) the control of the charging termination voltage of the super capacitor can be realized only, and the constant current charging can not be carried out on the super capacitor. (2) The charging current is too large in the initial charging period, which causes the internal temperature of the super capacitor Csuper to be too high, thereby affecting the capacitor life. (3) When the charging voltage of the super capacitor Csuper is close to the preset charging termination voltage, if the super capacitor Csuper is charged with a large current, the internal temperature of the super capacitor Csuper is too high, and the capacity characteristic of the super capacitor Csuper is affected. (4) When the charging voltage of the super capacitor Csuper approaches the preset charging termination voltage, instant overshoot phenomenon can occur if the super capacitor Csuper is charged with large current, so that the charging voltage exceeds the rated voltage of the super capacitor Csuper, and the problems of capacity reduction and service life shortening of the super capacitor can be caused.
In view of this, the present disclosure provides a charging circuit to at least implement constant current and constant voltage charging of a device to be charged based on an LDO structure.
Fig. 2 is a block diagram illustrating a charging circuit in accordance with an example embodiment. As shown in fig. 2, the charging circuit 200 may include a constant voltage charging module 201 and a constant current charging module 202, wherein the constant voltage charging module 201 and the constant current charging module 202 are connected.
The constant voltage charging module 201 is configured to obtain a current voltage of the device 300 to be charged, determine whether the current voltage of the device 300 to be charged is less than a reference voltage, and generate a control instruction for instructing the constant current charging module 202 to perform constant current charging on the device 300 to be charged when the current voltage is determined to be less than the reference voltage. The device 300 to be charged may be a super capacitor, a rechargeable battery, or any other device capable of constant current and constant voltage charging. The reference voltage is a preset voltage, which may be the rated voltage of the device to be charged, or a voltage slightly less than the rated voltage.
In one possible manner, the constant voltage charging module 201 may not be connected to the device to be charged 300. When charging, the user detects the voltage of the device 300 to be charged based on the voltage detection device, and sends the voltage to the constant voltage charging module 201, so that the constant voltage charging module 201 obtains the current voltage of the device 300 to be charged.
In another possible manner, the constant voltage charging module 201 may be connected to the device 300 to be charged for obtaining the current voltage level of the device 300 to be charged. For example, the constant voltage charging module 201 is connected to the device to be charged 300 in a circuit by a wire.
After the constant voltage charging module 201 acquires the current voltage of the device to be charged 300 in the above manner, it determines whether to generate a control instruction for instructing the constant current charging module 202 to perform constant current charging on the device to be charged 300 according to the magnitude relationship between the current voltage of the device to be charged and the reference voltage. For example, when the current voltage of the device to be charged 300 is less than the reference voltage, a control instruction for instructing the constant current charging module to perform constant current charging on the device to be charged is generated. And when the current voltage is greater than or equal to the reference voltage, performing constant-voltage charging on the device to be charged.
The constant current charging module 202 is configured to perform constant current charging on the device to be charged 300 according to the constant charging current under the condition that the constant voltage charging module 201 determines to generate the control instruction. The magnitude of the constant charging current can be preset by a user according to actual requirements.
By adopting the charging circuit, when the current voltage of the device to be charged is greater than or equal to the reference voltage, the device to be charged is charged at a constant voltage, and when the current voltage of the device to be charged is less than the reference voltage, the device to be charged is charged at a constant current according to the constant charging current. Therefore, the charging termination voltage of the device to be charged can be accurately controlled by using the simple LDO structure, and the purpose of fully utilizing the capacity of the device to be charged without overshoot is achieved. In addition, in the constant-current charging process, the charging current can be set according to actual requirements, the purpose of controllable charging current is achieved, the problem that the service life of the charging device is influenced by overhigh internal temperature caused by overlarge current in the initial charging stage can be effectively avoided, and the service life of the charging device is prolonged.
To facilitate a better understanding of the charging circuit provided by the present disclosure, the charging circuit is described below in connection with a full embodiment.
The constant voltage charging module 201 in fig. 2 may include a comparing unit and a shunt branch, wherein the comparing unit is connected to the shunt branch, and the shunt branch is connected in parallel to the device to be charged. The comparison unit is used for determining whether the current voltage of the device to be charged is smaller than the reference voltage or not, and controlling the shunt branch to be disconnected under the condition that the current voltage is smaller than the reference voltage, so that the constant current charging module performs constant current charging on the device to be charged according to the constant charging current. And the comparison unit is also used for controlling the shunt branch circuit to be conducted under the condition that the current voltage is determined to be greater than or equal to the reference voltage so as to shunt the constant charging current through the shunt branch circuit, and correspondingly, the constant current charging module is also used for performing constant voltage charging on the device to be charged according to the shunted charging current. It should be noted that, when the shunt branch is turned on, the magnitude of the current flowing through the shunt branch is not constant. In the above embodiment, the control instruction for instructing the constant current charging module to perform constant current charging on the device to be charged may be an instruction for instructing to disconnect the shunt branch.
Illustratively, the comparison unit is an operational amplifier, and the shunt branch is a first N-type MOS transistor. The non-inverting input end of the operational amplifier is connected with the voltage input end of the device to be charged so as to obtain the current voltage of the device to be charged, and the inverting input end of the operational amplifier is connected with the reference voltage end so as to obtain the reference voltage of the device to be charged. The grid electrode of the first N-type MOS tube is connected with the output end of the operational amplifier, the drain electrode of the first N-type MOS tube is connected with the constant current charging module, and the source electrode of the first N-type MOS tube is grounded.
Therefore, when the current voltage of the device to be charged is smaller than the reference voltage, the first N-type MOS transistor MN1 is turned off, and at this time, the current is not shunted, and the constant current charging module charges the device to be charged with the constant charging current. When the current voltage of the device to be charged is greater than or equal to the reference voltage, the first N-type MOS transistor MN1 is turned on, and a part of the constant charging current flows into the ground through the drain and the source of the first N-type MOS transistor MN1, so that the constant current charging module charges the charging device with the shunted charging current.
Therefore, when the current voltage of the device to be charged is smaller than the reference voltage, the device to be charged is charged by using the constant charging current, and the charging efficiency can be improved. When the current voltage of the device to be charged is close to the reference voltage, the shunt branch is conducted to reduce the charging current, so that the problem that the performance of the device to be charged is influenced due to overhigh internal temperature if the device to be charged is charged with large current when the current voltage of the device to be charged is close to the reference voltage can be avoided, and the problems that the capacity of the device to be charged is reduced and the service life of the device to be charged is shortened due to instant overshoot phenomenon caused if the device to be charged is charged with large current when the current voltage of the device to be charged is close to the reference voltage can be avoided.
In addition, the current voltage magnitude of the device to be charged can also be obtained based on the voltage feedback model 203. Illustratively, the voltage feedback module 203 is configured to be connected to the device 300 to be charged to generate an electrical signal for representing a current voltage level of the device 300 to be charged, and the constant voltage charging module 201 is further configured to obtain the current voltage level of the device to be charged according to the electrical signal.
In one embodiment, one end of the voltage feedback module 203 is connected to one end of the device to be charged, and the other end is grounded, so that the voltage feedback module 203 can directly detect the current voltage of the device to be charged, and further generate an electrical signal for representing the current voltage of the device to be charged.
In another embodiment, the voltage feedback module 203 may include a first resistor, a second resistor, and a voltage detection device. The voltage detection device is connected with the constant voltage charging module, one end of the first resistor is connected with the device to be charged, the other end of the first resistor is connected with one end of the second resistor, and the other end of the second resistor is grounded; the voltage detection device is used for detecting the voltage of the first resistor and/or the second resistor, determining the current voltage of the device to be charged according to the detected voltage, and generating an electric signal for representing the current voltage of the device to be charged.
For example, when the voltage detection device detects the voltage of the first resistor or the second resistor, the sum of the voltages of the first resistor and the second resistor, which is the current voltage of the device to be charged, may be calculated based on the resistance value of the first resistor, the resistance value of the second resistor, and the detected voltage value.
In still another embodiment, in case that the constant voltage charging module 201 includes an operational amplifier, the voltage feedback module 203 may further include only the first resistor and the second resistor. One end of the first resistor is connected with the device to be charged, the other end of the first resistor is connected with the non-inverting input end of the operational amplifier and one end of the second resistor respectively, the other end of the second resistor is grounded, and the inverting input end of the operational amplifier is connected with the reference voltage end so as to obtain the reference voltage of the device to be charged.
It should be noted that, in this embodiment, the voltage input to the non-inverting input terminal of the operational amplifier is a voltage across the second resistor, the voltage is proportional to the voltage of the device to be charged, and the ratio between the two is R2/(R1 + R2), where R1 represents the resistance of the first resistor, and R2 represents the resistance of the second resistor. Accordingly, the value of the reference voltage may be the product of the rated voltage and R2/(R1 + R2), or may be slightly smaller than the product of the rated voltage and R2/(R1 + R2).
The charging circuit provided by the present disclosure is described below with a full figure.
Fig. 3 is a schematic diagram illustrating a charging circuit in accordance with an exemplary embodiment. As shown in fig. 3, the device to be charged is a super capacitor Csuper. One end of a first resistor R1 in the voltage feedback module is connected with one end of a super capacitor Csuper, the other end of a first resistor R1 is respectively connected with the non-inverting input end of the operational amplifier and one end of a second resistor R2, the other end of the second resistor R2 is grounded, the inverting input end of the operational amplifier inputs a reference voltage VREF, and the output end of the operational amplifier is connected with the constant current charging module.
The constant-current charging module comprises a power supply, a current bias circuit, a second N-type MOS (metal oxide semiconductor) transistor MN2, a third N-type MOS transistor MN3, a first P-type MOS transistor MP1 and a second P-type MOS transistor MP 2. As shown in fig. 3, one end of the current bias circuit is connected to the power supply VDD to generate a constant charging current, and the other end of the current bias circuit is connected to the output end of the operational amplifier, the drain and the gate of the second N-type MOS transistor MN2, and the gate of the third N-type MOS transistor MN3, respectively; the source of the second N-type MOS transistor MN2 and the source of the third N-type MOS transistor MN3 are grounded. Thus, the second N-type MOS transistor MN2 and the third N-type MOS transistor MN3 constitute a pair of N-type mirror cells.
The drain electrode of the third N-type MOS transistor MN3 is connected with the drain electrode and the gate electrode of the first P-type MOS transistor MP1 and the gate electrode of the second P-type MOS transistor MP 2; the source electrode of the first P-type MOS tube MP1 and the source electrode of the second P-type MOS tube MP2 are both connected with a power supply VDD, and the drain electrode of the second P-type MOS tube MP2 is connected with the super capacitor Csuper and is used for carrying out constant current charging on the super capacitor Csuper according to constant charging current. Thus, the first P-type MOS transistor MP1 and the second P-type MOS transistor MP2 form a pair of P-type mirror cells.
At the beginning of charging, when VFB is smaller than VREF, the first N-type MOS transistor MN1 is not turned on, and the second N-type MOS transistor MN2, the third N-type MOS transistor MN3, the first P-type MOS transistor MP1, and the second P-type MOS transistor MP2 are all in a conducting state. At this time, the constant charging current ICC output by the current bias circuit flows into the super capacitor Csuper through the second N-type MOS transistor MN2, the third N-type MOS transistor MN3, the first P-type MOS transistor MP1 and the second P-type MOS transistor MP2 to perform constant current charging on the super capacitor Csuper.
In the present disclosure, when the super capacitor Csuper is subjected to constant-current charging based on a constant charging current, the target charging current of the super capacitor Csuper is a product of the constant charging current ICC and a first proportionality coefficient and a second proportionality coefficient. The target charging current is the actual charging current. The first proportionality coefficient is a current mirror proportionality coefficient between the third N-type MOS transistor MN3 and the second N-type MOS transistor MN2, and the second proportionality coefficient is a current mirror proportionality coefficient between the second P-type MOS transistor MP2 and the first P-type MOS transistor MP 1.
It is noted that the current bias circuit can be designed according to actual requirements to obtain a desired constant charging current. Similarly, the second N-type MOS transistor MN2, the third N-type MOS transistor MN3, the first P-type MOS transistor MP1, and the second P-type MOS transistor MP2 may be selected according to actual requirements. The present disclosure is not limited thereto.
When VFB is greater than or equal to VREF, the first N-type MOS transistor MN1 is turned on, and the second N-type MOS transistor MN2, the third N-type MOS transistor MN3, the first P-type MOS transistor MP1, and the second P-type MOS transistor MP2 are all in a turned-on state. At this time, part of the current ICV in the constant charging current ICC output by the current bias circuit flows into the ground through the first N-type MOS transistor MN1, and the shunted charging current (ICC-ICV) flows into the super capacitor Csuper through the second N-type MOS transistor MN2, the third N-type MOS transistor MN3, the first P-type MOS transistor MP1 and the second P-type MOS transistor MP2 to charge the super capacitor Csuper with a small current.
In practical applications, VFB is gradually increased, and when VBF is first increased from being smaller than VREF to being equal to VREF, the first N-type MOS transistor MN1 is turned on, and a part of the current ICV in the constant charging current ICC output by the current bias circuit flows into ground through the first N-type MOS transistor MN 1. And, ICV is gradually increased, and accordingly, the shunted charging current (ICC-ICV) is gradually decreased, and before the value is decreased to zero, the voltage of the super capacitor Csuper is still continuously increased, that is, VBF is still continuously increased and is greater than VREF. When the ICV increases to the ICC, the voltage of the super capacitor Csuper remains unchanged. It is worth noting that the increase of ICV from zero to ICC is short and negligible.
Furthermore, if considering the process of increasing the ICV from zero to ICC, the value of the reference voltage VREF may be slightly less than the product of the nominal voltage of the super-capacitor Csuper and R2/(R1 + R2) to ensure that the end-of-charge voltage of the super-capacitor Csuper does not exceed the nominal voltage.
Similarly, when the super capacitor Csuper is charged based on the shunted charging current, the target charging current of the super capacitor Csuper is the product of the shunted charging current (ICC-ICV) and the first and second scaling coefficients, which are as described above and are not described herein again.
Therefore, the charging circuit can realize smooth transition of the device to be charged from the constant-current charging mode to the constant-voltage charging mode.
In addition, the present disclosure also provides another charging circuit. Fig. 4 is a schematic diagram illustrating another charging circuit in accordance with an example embodiment. As shown in fig. 4, the constant voltage charging module 201 includes an operational amplifier and a third P-type MOS transistor MP3, and the constant current charging module 202 includes a power supply VDD, a bias circuit, a fourth P-type MOS transistor MP4, and a fifth P-type MOS transistor MP 5.
In fig. 4, one end of the first resistor R1 is connected to one end of the super capacitor Csuper, the other end of the first resistor R1 is connected to the inverting input terminal of the operational amplifier and one end of the second resistor R2, the other end of the second resistor R2 is grounded, the non-inverting input terminal of the operational amplifier is input with the reference voltage VREF, and the output terminal of the operational amplifier is connected to the gate of the third P-type MOS transistor MP 3. The source of the third P-type MOS transistor MP3, the source of the fourth P-type MOS transistor MP4, and the source of the fifth P-type MOS transistor MP5 are all connected to the power supply VDD, the drain of the third P-type MOS transistor MP3, the drain and the gate of the fourth P-type MOS transistor MP4, and the gate of the fifth P-type MOS transistor MP5 are all connected to one end of a bias circuit, and the other end of the bias circuit is grounded, where the bias circuit is configured to generate a constant charging current ICC. The drain of the fifth P-type MOS transistor MP5 is connected to one end of the super capacitor Csuper.
When VBF is smaller than VREF, the third P-type MOS transistor MP3 is not turned on, the fourth P-type MOS transistor MP4 and the fifth P-type MOS transistor MP5 are both in a conductive state, and at this time, the constant current ICC generated by the bias circuit flows into the super capacitor Csuper through the fifth P-type MOS transistor MP5 to perform constant current charging on the super capacitor Csuper.
When VBF is greater than or equal to VREF, the third P-type MOS transistor MP3 is turned on, the fourth P-type MOS transistor MP4 and the fifth P-type MOS transistor MP5 are still in a conductive state, and at this time, the constant charging current ICC generated by the bias circuit is equal to the sum of the current ICV of the third P-type MOS transistor MP3 and the currents of the fourth P-type MOS transistor MP4 and the fifth P-type MOS transistor MP 5. Namely, the fifth P-type MOS transistor MP5 charges the super capacitor Csuper with a small current based on the charging current of ICC-ICV, and the super capacitor Csuper enters a constant voltage charging stage until ICV equals ICC.
The invention is not limited to the embodiments described above, but can be practiced with modification and alteration within the spirit and scope of the appended claims. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention. Therefore, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention shall be covered by the claims of the present invention.
It should be noted that, in the foregoing embodiments, various features described in the above embodiments may be combined in any suitable manner to avoid unnecessary repetition, and the disclosure does not separately describe various possible combinations.
In addition, any combination of various embodiments of the present disclosure may be made, and the same should be considered as the disclosure of the present disclosure, as long as it does not depart from the spirit of the present disclosure.

Claims (8)

1. A charging circuit, comprising: the constant-voltage charging system comprises a constant-voltage charging module and a constant-current charging module, wherein the constant-voltage charging module is connected with the constant-current charging module;
the constant voltage charging module is used for acquiring the current voltage of the device to be charged, determining whether the current voltage of the device to be charged is smaller than a reference voltage, and generating a control instruction for instructing the constant current charging module to perform constant current charging on the device to be charged under the condition that the current voltage is smaller than the reference voltage;
the constant current charging module is used for responding to the control instruction and carrying out constant current charging on the device to be charged according to the constant charging current;
the constant-voltage charging module comprises a comparison unit and a shunt branch, wherein the comparison unit is connected with the shunt branch, and the shunt branch is connected with the device to be charged in parallel;
the comparison unit is an operational amplifier, and the shunt branch is a first N-type MOS tube;
the non-inverting input end of the operational amplifier is connected with the voltage input end of the device to be charged so as to obtain the current voltage of the device to be charged, and the inverting input end of the operational amplifier is connected with the reference voltage end so as to obtain the reference voltage of the device to be charged;
the grid electrode of the first N-type MOS tube is connected with the output end of the operational amplifier, the drain electrode of the first N-type MOS tube is connected with the constant current charging module, and the source electrode of the first N-type MOS tube is grounded;
the operational amplifier is further configured to control the first N-type MOS transistor to be turned on when it is determined that the current voltage is greater than or equal to the reference voltage, so as to shunt the constant charging current through the first N-type MOS transistor, wherein when the first N-type MOS transistor is turned on, the current flowing through the first N-type MOS transistor gradually increases until the constant charging current is increased, and charging is ended;
and the constant-current charging module is also used for carrying out constant-voltage charging on the device to be charged according to the shunted charging current.
2. The charging circuit according to claim 1, wherein the operational amplifier is configured to determine whether a present voltage of the device to be charged is less than the reference voltage, and control the first N-type MOS transistor to be turned off when the present voltage is determined to be less than the reference voltage, so that the device to be charged is subjected to constant current charging by the constant current charging module according to the constant charging current.
3. The charging circuit of claim 1, wherein the constant current charging module comprises: the power supply comprises a power supply source, a current bias circuit, a second N-type MOS tube, a third N-type MOS tube, a first P-type MOS tube and a second P-type MOS tube;
one end of the current bias circuit is connected with the power supply to generate the constant charging current;
the other end of the current bias circuit is respectively connected with the constant-voltage charging module, the drain electrode and the grid electrode of the second N-type MOS tube and the grid electrode of the third N-type MOS tube;
the source electrode of the second N-type MOS tube is grounded with the source electrode of the third N-type MOS tube;
the drain electrode of the third N-type MOS tube is connected with the drain electrode and the grid electrode of the first P-type MOS tube and the grid electrode of the second P-type MOS tube;
the source electrode of the first P-type MOS tube and the source electrode of the second P-type MOS tube are both connected with the power supply;
and the drain electrode of the second P-type MOS tube is connected with the device to be charged and is used for carrying out constant current charging on the device to be charged according to the constant charging current.
4. The charging circuit according to claim 3, wherein in a constant current charging phase, the target charging current of the device to be charged is a product of the constant charging current and a first proportionality coefficient and a second proportionality coefficient, wherein the first proportionality coefficient is a current mirror proportionality coefficient of the third N-type MOS transistor and the second N-type MOS transistor, and the second proportionality coefficient is a current mirror proportionality coefficient of the second P-type MOS transistor and the first P-type MOS transistor.
5. The charging circuit of claim 1, further comprising: the voltage feedback module is connected with the constant voltage charging module;
the voltage feedback module is used for being connected with the device to be charged so as to generate an electric signal for representing the current voltage of the device to be charged;
the constant voltage charging module is further used for obtaining the current voltage of the device to be charged according to the electric signal.
6. The charging circuit of claim 5, wherein the voltage feedback module comprises a first resistor, a second resistor and a voltage detection device, wherein the voltage detection device is connected to the constant voltage charging module;
one end of the first resistor is connected with the device to be charged, the other end of the first resistor is connected with one end of the second resistor, and the other end of the second resistor is grounded;
the voltage detection device is used for detecting the voltage of the first resistor and/or the second resistor, determining the current voltage of the device to be charged according to the detected voltage, and generating an electric signal for representing the current voltage of the device to be charged.
7. The charging circuit of claim 5, wherein the constant voltage charging module comprises an operational amplifier, and the voltage feedback module comprises a first resistor and a second resistor;
one end of the first resistor is connected with the device to be charged, the other end of the first resistor is connected with the non-inverting input end of the operational amplifier and one end of the second resistor respectively, the other end of the second resistor is grounded, and the inverting input end of the operational amplifier is connected with a reference voltage end so as to obtain the reference voltage of the device to be charged.
8. The charging circuit of claim 1, wherein the reference voltage is less than a voltage rating of the device to be charged.
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