Constant-current and constant-voltage charging system

Abstract

The invention discloses a constant-current and constant-voltage charging system which comprises a constant-current and constant-voltage mode conversion circuit, a charging current control circuit, a control circuit and a battery voltage sampling circuit. The control circuit is respectively connected with the constant-current and constant-voltage mode conversion circuit, the charging current control circuit and the battery voltage sampling circuit, and the constant-current and constant-voltage mode conversion circuit is respectively connected with the charging current control circuit and the battery voltage sampling circuit; the constant-current and constant-voltage mode conversion circuit comprises a power conversion circuit, a first triode circuit and a constant-current and constant-voltage conversion circuit, and the charging current control circuit comprises a second triode circuit and an MOS (Metal Oxide Semiconductor) tube circuit. The technical problems that a standby power supply charging circuit of an existing power terminal is complex in structure and control mode and high in cost are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of charging circuits, and in particular to a constant current and constant voltage charging system. Background Art

[0002] The power terminal is usually installed on the secondary side of the transformer at the substation. When the circuit needs to be repaired at the substation, a power-off operation needs to be performed. Therefore, the power terminal is generally equipped with a rechargeable battery or farad capacitor as a backup power supply. The patent document with application number CN202211427880.1 discloses a power terminal power supply, including a switching power supply, a backup power supply unit, a main control module unit and a DCDC conversion unit. The switching power supply is respectively connected to the input end of the backup power supply unit and the input end of the DCDC conversion unit. The output end of the DCDC conversion unit is respectively connected to the main control module unit and the functional unit through a load switch. The output of the backup power supply unit is connected to the input end of the DCDC conversion unit, or the output end of the backup power supply unit is connected to the functional unit through a load switch, or the output end of the backup power supply unit is connected to the main control module unit. The existing backup power supply charging circuit structure and control are complex and the cost is high. Therefore, it is urgent to propose a constant current and constant voltage charging system to solve the technical problems of the complex structure and control method of the backup power supply charging circuit of the existing power terminal, as well as the high cost. Summary of the Invention

[0003] The main purpose of the present invention is to propose a constant current and constant voltage charging system, which aims to solve the technical problems of the complex structure and control method of the backup power charging circuit of the existing power terminal and the high cost.

[0004] To achieve the above objectives, the present invention provides a constant current and constant voltage charging system, wherein the constant current and constant voltage charging system includes: a constant current and constant voltage mode conversion circuit, a charging current control circuit, a control circuit and a battery voltage sampling circuit; the control circuit is respectively connected to the constant current and constant voltage mode conversion circuit, the charging current control circuit and the battery voltage sampling circuit, and the constant current and constant voltage mode conversion circuit is respectively connected to the charging current control circuit and the battery voltage sampling circuit; the constant current and constant voltage mode conversion circuit includes a power conversion circuit, a first transistor circuit and a constant current and constant voltage conversion circuit, the power conversion circuit includes a power chip U1, the power chip U1 is respectively connected to a second transistor circuit, a MOS transistor power supply and a constant current and constant voltage conversion circuit, the first transistor circuit is respectively connected to the MOS transistor circuit and the control circuit, the constant current and constant voltage conversion circuit is respectively connected to the MOS transistor circuit and the battery voltage sampling circuit; the charging current control circuit includes a second transistor circuit and a MOS transistor circuit, and the second transistor circuit is respectively connected to the MOS transistor circuit and the control circuit.

[0005] In one preferred embodiment, the first transistor circuit comprises a transistor Q7, a resistor R6, a resistor R7, a resistor R8 and a capacitor C2.

[0006] The base of the transistor Q7 is connected to the resistor R7, the other end of the resistor R7 is connected to the control circuit and the resistor R8 respectively, the collector of the transistor Q7 is connected to the resistor R6 and the MOS transistor circuit respectively, the other end of the resistor R6 is connected to the power supply terminal and the capacitor C2 respectively, the emitter of the transistor Q7, the resistor R8 and the other end of the capacitor C2 are grounded.

[0007] In one preferred embodiment, the constant current and constant voltage conversion circuit comprises a MOS transistor Q3, a MOS transistor Q5 and a MOS transistor Q6.

[0008] The drain of the MOS transistor Q3 is connected to the MOS transistor circuit, the source of the MOS transistor Q3 is connected to the battery voltage sampling circuit, and the gate of the MOS transistor Q3 is connected to the MOS transistor circuit; the drain of the MOS transistor Q5 is connected to the battery voltage sampling circuit, the source of the MOS transistor Q5 is connected to the drain of the MOS transistor Q6, the MOS transistor circuit and the power conversion circuit respectively, the gate of the MOS transistor Q5 is connected to the MOS transistor circuit, the source of the MOS transistor Q6 is grounded, and the gate of the MOS transistor Q6 is connected to the MOS transistor circuit.

[0009] In one preferred embodiment, the MOS transistor Q3 is an N-channel MOS transistor, the MOS transistor Q5 is a P-channel MOS transistor, and the MOS transistor Q6 is an N-channel MOS transistor.

[0010] In one preferred embodiment, the second transistor circuit comprises a transistor Q2, a resistor R3, a resistor R12 and a resistor R1.

[0011] The base of the transistor Q2 is connected to the resistor R3, the other end of the resistor R3 is connected to the control circuit and the resistor R12 respectively, the collector of the transistor Q2 is connected to the resistor R1 and the MOS transistor circuit respectively, the other end of the resistor R1 is connected to the power conversion circuit and the power supply terminal respectively, and the emitter of the transistor Q2 and the other end of the resistor R12 are grounded.

[0012] In one preferred embodiment, the MOS transistor circuit comprises a MOS transistor Q1, a MOS transistor Q4, a resistor R2 and a resistor R5.

[0013] The source of the MOS transistor Q1 is respectively connected to the source of the MOS transistor Q4, the power conversion circuit, and the constant current and constant voltage conversion circuit; the drain of the MOS transistor Q1 is connected to the resistor R2; the other end of the resistor R2 is respectively connected to the power conversion circuit, the constant current and constant voltage conversion circuit, and the resistor R5; the gate of the MOS transistor Q1 is connected to the second triode circuit; the other end of the resistor R5 is connected to the drain of the MOS transistor Q4; the gate of the MOS transistor Q4 is respectively connected to the constant current and constant voltage conversion circuit and the first triode circuit.

[0014] In one preferred solution, the MOS transistor Q1 is a P-channel MOS transistor, and the MOS transistor Q4 is a P-channel MOS transistor.

[0015] In one preferred embodiment, the control circuit includes a controller U2, a resistor R9, a resistor R10 and a capacitor C3;

[0016] Pin 1 of the controller U2 is connected to the second triode circuit, pin 2 of the controller U2 is connected to the first triode circuit, and pin 3 of the controller U2 is connected to resistor R9, capacitor C3 and resistor R10 respectively. The other end of the resistor R9 is connected to the battery voltage sampling circuit, and the other ends of the resistor R10 and capacitor C3 are grounded.

[0017] In one preferred embodiment, the battery voltage sampling circuit includes a battery BT1, a diode D2, a diode D1, and a diode D3;

[0018] The positive electrode of the battery BT1 is respectively connected to the cathode of the diode D3 and the control circuit, the anode of the diode D3 is respectively connected to the constant current and constant voltage conversion circuit, the cathode of the diode D1 and the cathode of the diode D2, the anode of the diode D1 is connected to the constant current and constant voltage conversion circuit, and the anode of the diode D2 and the negative electrode of the battery BT1 are grounded.

[0019] In the above technical solution of the present invention, the constant current constant voltage charging system includes: a constant current constant voltage mode conversion circuit, a charging current control circuit, a control circuit and a battery voltage sampling circuit; the control circuit is respectively connected to the constant current constant voltage mode conversion circuit, the charging current control circuit and the battery voltage sampling circuit, and the constant current constant voltage mode conversion circuit is respectively connected to the charging current control circuit and the battery voltage sampling circuit; the constant current constant voltage mode conversion circuit includes a power conversion circuit, a first transistor circuit and a constant current constant voltage conversion circuit, the power conversion circuit includes a power chip U1, the power chip U1 is respectively connected to the second transistor circuit, the MOS transistor power supply and the constant current constant voltage conversion circuit, the first transistor circuit is respectively connected to the MOS transistor circuit and the control circuit, the constant current constant voltage conversion circuit is respectively connected to the MOS transistor circuit and the battery voltage sampling circuit; the charging current control circuit includes a second transistor circuit and a MOS transistor circuit, and the second transistor circuit is respectively connected to the MOS transistor circuit and the control circuit. The present invention solves the technical problems of the complex structure and control method of the backup power charging circuit of the existing power terminal, as well as the high cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1 This is a first schematic diagram of a constant current and constant voltage charging system according to an embodiment of the present invention;

[0022] Figure 2 This is a second schematic diagram of a constant current and constant voltage charging system according to an embodiment of the present invention;

[0023] Figure 3 is a schematic diagram of a control circuit according to an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of a constant current slow charging circuit of a constant current and constant voltage charging system according to an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of a constant current fast charging circuit of a constant current and constant voltage charging system according to an embodiment of the present invention;

[0026] Figure 6 A schematic diagram of a constant voltage charging circuit of a constant current and constant voltage charging system according to an embodiment of the present invention;

[0027] Figure 7This is a charging control flow chart of a constant current and constant voltage charging system according to an embodiment of the present invention.

[0028] The realization of the objectives, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0030] It should be noted that all directional indications (such as up, down, etc.) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0031] In addition, the terms "first," "second," and so on, used in this disclosure are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features specified as "first" or "second" may explicitly or implicitly include at least one of these features.

[0032] Moreover, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0033] See also Figure 1According to one aspect of the present invention, the present invention provides a constant current and constant voltage charging system, wherein the constant current and constant voltage charging system includes: a constant current and constant voltage mode conversion circuit, a charging current control circuit, a control circuit and a battery voltage sampling circuit; the control circuit is respectively connected to the constant current and constant voltage mode conversion circuit, the charging current control circuit and the battery voltage sampling circuit, and the constant current and constant voltage mode conversion circuit is respectively connected to the charging current control circuit and the battery voltage sampling circuit; the constant current and constant voltage mode conversion circuit includes a power conversion circuit, a first transistor circuit and a constant current and constant voltage conversion circuit, the power conversion circuit includes a power chip U1, the power chip U1 is respectively connected to a second transistor circuit, a MOS transistor power supply and a constant current and constant voltage conversion circuit, the first transistor circuit is respectively connected to the MOS transistor circuit and the control circuit, the constant current and constant voltage conversion circuit is respectively connected to the MOS transistor circuit and the battery voltage sampling circuit; the charging current control circuit includes a second transistor circuit and a MOS transistor circuit, and the second transistor circuit is respectively connected to the MOS transistor circuit and the control circuit.

[0034] Specifically, in this embodiment, the power conversion circuit includes a power chip U1 and a capacitor C1; the Vin pin of the power chip U1 is connected to the second transistor circuit and the capacitor C1, the other end of the capacitor C1 is grounded, the Vout pin of the power chip U1 is connected to the MOS tube circuit, and the Gnd pin of the power chip U1 is grounded; the power conversion circuit is used to convert a 15V input voltage into a fixed 5V voltage output. After the GND pin of the power chip U1 is suspended through the MOS tube Q6, a constant current circuit can be formed. The power chip U1 supports a maximum input of 30V, and the capacitor C1 is a filter capacitor.

[0035] Specifically, in this embodiment, the first transistor circuit includes a transistor Q7, a resistor R6, a resistor R7, a resistor R8 and a capacitor C2; the base of the transistor Q7 is connected to the resistor R7, the other end of the resistor R7 is respectively connected to the control circuit and the resistor R8, the collector of the transistor Q7 is respectively connected to the resistor R6 and the MOS transistor circuit, the other end of the resistor R6 is respectively connected to the power supply end and the capacitor C2, and the emitter of the transistor Q7, the resistor R8 and the other end of the capacitor C2 are grounded; when the front-end signal of the base resistor R7 of the transistor Q7 is high, the transistor Q7 is turned on, and after the transistor Q7 is turned on, the signal CTR2 at the upper end of the resistor R6 is pulled down to a low level. Level, at this time, the MOS tubes Q4 and MOS tubes Q5 connected to the CTR2 end are turned on, and the MOS tubes Q3 and MOS tubes Q6 are turned off. At this time, the circuit is in constant current charging mode. Due to the large resistance of resistor R5, the MOS tube Q1 is controlled to be turned off at this time, which is a constant current slow charging mode. If the MOS tube Q1 is controlled to be turned on, since the resistor R2 is smaller than the resistor R5, the resistance value is reduced after the two are connected in parallel, and this is a constant current fast charging mode. When the front-end signal of the base resistor R7 of the transistor Q7 is low, the transistor Q7 is turned off. After the transistor Q7 is turned off, the signal CTR2 at the upper end of the resistor R6 is pulled up to a high level by the 15V voltage. At this time, the MOS tube Q4 connected to the CTR2 end is turned off, and the MOS tube Q3 is turned on.

[0036] Specifically, in this embodiment, the constant current and constant voltage conversion circuit includes a MOS transistor Q3, a MOS transistor Q5, and a MOS transistor Q6; the drain of the MOS transistor Q3 is connected to the MOS transistor circuit, the source of the MOS transistor Q3 is connected to the battery voltage sampling circuit, and the gate of the MOS transistor Q3 is connected to the MOS transistor circuit; the drain of the MOS transistor Q5 is connected to the battery voltage sampling circuit, the source of the MOS transistor Q5 is respectively connected to the drain of the MOS transistor Q6, the MOS transistor circuit, and the power conversion circuit, the gate of the MOS transistor Q5 is connected to the MOS transistor circuit, the source of the MOS transistor Q6 is grounded, and the gate of the MOS transistor Q6 is connected to the MOS transistor circuit; the MOS transistors Q3, Q5, and Q6 are used to control the circuit to switch to a constant current and constant voltage mode.

[0037] Specifically, in this embodiment, the MOS transistor Q3 is an N-channel MOS transistor, the MOS transistor Q5 is a P-channel MOS transistor, and the MOS transistor Q6 is an N-channel MOS transistor.

[0038] Specifically, in this embodiment, the second transistor circuit includes a transistor Q2, a resistor R3, a resistor R12 and a resistor R1; the base of the transistor Q2 is connected to the resistor R3, the other end of the resistor R3 is respectively connected to the control circuit and the resistor R12, the collector of the transistor Q2 is respectively connected to the resistor R1 and the MOS transistor circuit, the other end of the resistor R1 is respectively connected to the power conversion circuit and the power supply end, the emitter of the transistor Q2 and the other end of the resistor R12 are grounded; when the front-end signal of the base resistor R3 of the transistor Q2 is low, the transistor Q2 is turned off, and the transistor Q2 is turned off. After transistor Q2 is turned off, the signal CTR1 at the upper end of resistor R1 is pulled up to a high level by the 15V voltage. At this time, the MOS transistor Q1 connected to the CTR1 end is turned off, and the resistor R2 is disconnected. The charging current can be controlled by connecting or disconnecting the resistor R2. When the front-end signal of the base resistor R3 of transistor Q2 is high, transistor Q2 is turned on. After transistor Q2 is turned on, the signal CTR1 at the upper end of resistor R1 is pulled down to a low level. At this time, the MOS transistor Q1 connected to the CTR1 end is turned on, and the resistor R2 is connected to the circuit. The charging current can be controlled by connecting or disconnecting the resistor R2.

[0039] Specifically, in this embodiment, the MOS transistor circuit includes a MOS transistor Q1, a MOS transistor Q4, a resistor R2, and a resistor R5; the source of the MOS transistor Q1 is respectively connected to the source of the MOS transistor Q4, the power conversion circuit, and the constant current and constant voltage conversion circuit; the drain of the MOS transistor Q1 is connected to the resistor R2; the other end of the resistor R2 is respectively connected to the power conversion circuit, the constant current and constant voltage conversion circuit, and the resistor R5; the gate of the MOS transistor Q1 is connected to the second triode circuit; the other end of the resistor R5 is connected to the drain of the MOS transistor Q4; the gate of the MOS transistor Q4 is respectively connected to the constant current and constant voltage conversion circuit and the first triode circuit; the MOS transistor Q1 is controlled by a signal CTR1, and the MOS transistor Q4 is controlled by a signal CTR2.

[0040] Specifically, in this embodiment, the MOS transistor Q1 is a P-channel MOS transistor, and the MOS transistor Q4 is a P-channel MOS transistor.

[0041] Specifically, in this embodiment, see Figure 3The control circuit includes a controller U2, a resistor R9, a resistor R10 and a capacitor C3; pin 1 of the controller U2 is connected to the second transistor circuit, pin 2 of the controller U2 is connected to the first transistor circuit, and pin 3 of the controller U2 is connected to the resistor R9, capacitor C3 and resistor R10 respectively. The other end of the resistor R9 is connected to the battery voltage sampling circuit, and the other ends of the resistor R10 and capacitor C3 are grounded; the controller U2 gives a high level or a low level through pins 1 and 2 to control transistors Q2 and Q7. Pin 3 of the controller U2 is used to sample the battery voltage and control the charging mode according to the state of the battery voltage.

[0042] Specifically, in this embodiment, the battery voltage sampling circuit includes a battery BT1, a diode D2, a diode D1 and a diode D3; the positive electrode of the battery BT1 is respectively connected to the cathode of the diode D3 and the control circuit, the anode of the diode D3 is respectively connected to the constant current constant voltage conversion circuit, the cathode of the diode D1 and the cathode of the diode D2, the anode of the diode D1 is connected to the constant current constant voltage conversion circuit, and the anode of the diode D2 and the negative electrode of the battery BT1 are grounded.

[0043] Specifically, in this embodiment, see Figure 4 It is the constant current slow charging mode of the constant current and constant voltage charging system. After power-on, the constant current slow charging mode is started. At this time, the charging current is very small, and the charging current is reduced to protect the battery. At this time, the system detects the battery voltage and switches the charging mode according to the detected battery voltage range. The gate of the MOS tube Q1 is pulled up by the resistor R1 and is in the closed state. The resistance of the resistor R2 is less than the resistance of the resistor R5. Since the resistance of the resistor R5 is very large, the charging current is limited at this time, and the system is in the constant current slow charging mode.

[0044] Specifically, in this embodiment, see Figure 5 It is the constant current fast charging mode of the constant current and constant voltage charging system. Resistors R2 and R5 are connected to the system. Since the resistance of resistor R2 is much smaller than that of resistor R5, the resistance of resistors R2 and R5 in parallel is smaller than that of resistor R2. At this time, the charging current increases and the system is in constant current fast charging mode.

[0045] Specifically, in this embodiment, see Figure 6 It is a constant voltage mode of a constant current and constant voltage charging system. The constant voltage charging mode is realized by the constant voltage characteristic of the power chip U1. In the present invention, the power chip U1 adopts a power chip model LM78L05, and the capacitor C1 adopts a 10uF chip capacitor. The input voltage of the power chip U1 is 15V. The present invention does not make specific limitations and can be set according to needs.

[0046] Specifically, in this embodiment, when the output of pin 1 of the controller U2 of the control circuit is equal to 0, the CTR1 end of the second transistor circuit is equal to 1, and the MOS tube Q1 is turned off. When the output of pin 2 of the controller U2 is equal to 1, the CTR2 end of the first transistor circuit is equal to 0, the MOS tube Q4 is turned on, the MOS tube Q3 is turned off, the MOS tube Q5 is turned on, and the MOS tube Q6 is turned off. At this time, it is a constant current slow charging mode; when the output of pin 1 of the controller U2 of the control circuit is equal to 1, the CTR1 end of the second transistor circuit is equal to 0, the MOS tube Q1 is turned on, and when ... When the output is equal to 1, the CTR2 end of the first transistor circuit is equal to 0, the MOS tube Q4 is turned on, the MOS tube Q3 is turned off, the MOS tube Q5 is turned on, and the MOS tube Q6 is turned off. At this time, it is a constant current fast charging mode; when the output of the 1 pin of the controller U2 of the control circuit is equal to 0, the CTR1 end of the second transistor circuit is equal to 1, and the MOS tube Q1 is turned off. When the output of the 2 pin of the controller U2 is equal to 0, the CTR2 end of the first transistor circuit is equal to 1, the MOS tube Q4 is turned off, the MOS tube Q3 is turned on, the MOS tube Q5 is turned off, and the MOS tube Q6 is turned on. At this time, it is a constant current charging mode.

[0047] Specifically, in this embodiment, see Figure 7 The charging control process of the constant current and constant voltage charging system is as follows: the system starts the constant current slow charging mode when it is powered on. At this time, the charging current is very small, and the charging current is reduced to protect the battery. At this time, the system detects the battery voltage and switches the charging mode according to the detected battery voltage range. When the battery voltage is greater than the battery threshold voltage, the constant voltage charging mode is started. When the battery voltage is less than the battery threshold and less than the voltage setting value, the constant current fast charging mode is started. When the battery voltage is less than the battery threshold and greater than the voltage setting value, the constant current slow charging mode is started.

[0048] Specifically, in this embodiment, the transistor Q7 adopts a transistor of model LMBT4401LT1G, the resistor R6 adopts a chip resistor with a resistance of 300 ohms, the resistor R7 adopts a chip resistor with a resistance of 1000 ohms, the resistor R8 adopts a chip resistor with a resistance of 2000 ohms, and the capacitor C2 adopts a 10uF chip capacitor; the MOS tube Q5 adopts a P-channel MOS tube of model IRLML6401, the MOS tube Q3 adopts an N-channel MOS tube of model 2N7002LT1G, and the MOS tube Q6 adopts an N-channel MOS tube of model 2N7002LT1G; the transistor Q2 adopts a transistor of model LMBT4401LT1G, the resistor R3 adopts a chip resistor with a resistance of 1000 ohms, and the resistor R12 adopts a chip resistor with a resistance of 2 000 ohm chip resistor, resistor R1 uses a chip resistor with a resistance of 10000 ohm; the MOS tubes Q1 and Q4 use P-channel MOS tubes with model number IRLML6401, resistor R2 uses a chip resistor with a resistance of 100 ohm, and resistor R5 uses a chip resistor with a resistance of 5000 ohm; the controller U2 uses a universal CPU chip, resistor R9 uses a chip resistor with a resistance of 2 megohm, resistor R10 uses a chip resistor with a resistance of 1 megohm, and capacitor C3 uses a 1uF chip capacitor; the battery BT1 uses a 5V rechargeable battery, the diode D2 uses a 7.5V voltage regulator diode, and diodes D1 and D3 use Schottky diodes B340A to prevent battery current backflow; the present invention does not make specific limitations and can be set according to needs.

[0049] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. All equivalent structural transformations made using the contents of the present description and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A constant current and constant voltage charging system, characterized in that: include: Constant current and constant voltage mode conversion circuit, charging current control circuit, control circuit and battery voltage sampling circuit; The control circuit is respectively connected to the constant current and constant voltage mode conversion circuit, the charging current control circuit and the battery voltage sampling circuit, and the constant current and constant voltage mode conversion circuit is respectively connected to the charging current control circuit and the battery voltage sampling circuit; the constant current and constant voltage mode conversion circuit includes a power conversion circuit, a first triode circuit and a constant current and constant voltage conversion circuit, and the power conversion circuit includes a power chip U1, and the power chip U1 is respectively connected to the second triode circuit, the MOS tube power supply and the constant current and constant voltage conversion circuit, the first triode circuit is respectively connected to the MOS tube circuit and the control circuit, and the constant current and constant voltage conversion circuit is respectively connected to the MOS tube circuit and the battery voltage sampling circuit; the charging current control circuit includes a second triode circuit and a MOS tube circuit, and the second triode circuit is respectively connected to the MOS tube circuit and the control circuit.

2. A constant current and constant voltage charging system according to claim 1, characterized in that: The first transistor circuit includes a transistor Q7, a resistor R6, a resistor R7, a resistor R8 and a capacitor C2; The base of the transistor Q7 is connected to the resistor R7, the other end of the resistor R7 is connected to the control circuit and the resistor R8 respectively, the collector of the transistor Q7 is connected to the resistor R6 and the MOS tube circuit respectively, the other end of the resistor R6 is connected to the power supply end and the capacitor C2 respectively, and the emitter of the transistor Q7, the resistor R8 and the other end of the capacitor C2 are grounded.

3. A constant current and constant voltage charging system according to any one of claims 1-2, characterized in that: The constant current and constant voltage conversion circuit includes a MOS transistor Q3, a MOS transistor Q5 and a MOS transistor Q6; The drain of the MOS transistor Q3 is connected to the MOS transistor circuit, the source of the MOS transistor Q3 is connected to the battery voltage sampling circuit, and the gate of the MOS transistor Q3 is connected to the MOS transistor circuit; the drain of the MOS transistor Q5 is connected to the battery voltage sampling circuit, the source of the MOS transistor Q5 is respectively connected to the drain of the MOS transistor Q6, the MOS transistor circuit, and the power conversion circuit, the gate of the MOS transistor Q5 is connected to the MOS transistor circuit, the source of the MOS transistor Q6 is grounded, and the gate of the MOS transistor Q6 is connected to the MOS transistor circuit.

4. A constant current and constant voltage charging system according to claim 3, characterized in that: The MOS transistor Q3 is an N-channel MOS transistor, the MOS transistor Q5 is a P-channel MOS transistor, and the MOS transistor Q6 is an N-channel MOS transistor.

5. A constant current and constant voltage charging system according to any one of claims 1-2, characterized in that: The second transistor circuit includes a transistor Q2, a resistor R3, a resistor R12 and a resistor R1; The base of the transistor Q2 is connected to the resistor R3, the other end of the resistor R3 is connected to the control circuit and the resistor R12 respectively, the collector of the transistor Q2 is connected to the resistor R1 and the MOS tube circuit respectively, the other end of the resistor R1 is connected to the power conversion circuit and the power supply end respectively, and the emitter of the transistor Q2 and the other end of the resistor R12 are grounded.

6. A constant current and constant voltage charging system according to any one of claims 1-2, characterized in that: The MOS transistor circuit includes a MOS transistor Q1, a MOS transistor Q4, a resistor R2 and a resistor R5; The source of the MOS transistor Q1 is respectively connected to the source of the MOS transistor Q4, the power conversion circuit, and the constant current and constant voltage conversion circuit; the drain of the MOS transistor Q1 is connected to the resistor R2; the other end of the resistor R2 is respectively connected to the power conversion circuit, the constant current and constant voltage conversion circuit, and the resistor R5; the gate of the MOS transistor Q1 is connected to the second triode circuit; the other end of the resistor R5 is connected to the drain of the MOS transistor Q4; the gate of the MOS transistor Q4 is respectively connected to the constant current and constant voltage conversion circuit and the first triode circuit.

7. A constant current and constant voltage charging system according to claim 6, characterized in that: The MOS transistor Q1 is a P-channel MOS transistor, and the MOS transistor Q4 is a P-channel MOS transistor.

8. A constant current and constant voltage charging system according to any one of claims 1-2, characterized in that: The control circuit includes a controller U2, a resistor R9, a resistor R10 and a capacitor C3; Pin 1 of the controller U2 is connected to the second triode circuit, pin 2 of the controller U2 is connected to the first triode circuit, and pin 3 of the controller U2 is connected to resistor R9, capacitor C3 and resistor R10 respectively. The other end of the resistor R9 is connected to the battery voltage sampling circuit, and the other ends of the resistor R10 and capacitor C3 are grounded.

9. A constant current and constant voltage charging system according to any one of claims 1-2, characterized in that: The battery voltage sampling circuit includes a battery BT1, a diode D2, a diode D1 and a diode D3; The positive electrode of the battery BT1 is respectively connected to the cathode of the diode D3 and the control circuit, the anode of the diode D3 is respectively connected to the constant current and constant voltage conversion circuit, the cathode of the diode D1 and the cathode of the diode D2, the anode of the diode D1 is connected to the constant current and constant voltage conversion circuit, and the anode of the diode D2 and the negative electrode of the battery BT1 are grounded.

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