Current-limiting charging system for communication battery
By adding a parallel bypass between positive-end switch and positive-end filtering in the communication battery current-limit charging system, the high-power design problem of the current-limit charging system caused by the EMC problem of the current-limit charging system in the prior art is solved, and a small-volume and low-cost system design is realized, which improves the performance and competitiveness of the system.
Patent Information
- Application Number
- CN202411837719.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-04-11
AI Technical Summary
In the prior art, when solving the EMC problem, the current limit charging system faces the problem of large size and high cost due to high power design of the device, which is difficult to meet customer needs.
Design a communication battery current limit charging system, by adding a positive terminal switch and positive terminal filtering parallel bypass, cutting off the charging path, so that the current passes through the charging current limit DC-DC conversion circuit only, reducing the current design requirement of the EMC filter circuit.
It realizes a current-limited charging system with simple structural design, small PCBA size and low cost, effectively solves the EMC problem and improves the system's performance, delivery and cost competitiveness.
Smart Images
Figure CN119813433A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of uninterruptible power supply, and in particular to a communication battery current limiting charging system. Background Art
[0002] In the application of base station communication equipment and communication room uninterruptible power supply, the current limiting charging system usually involves EMC (battery compatibility) issues. The current limiting charging DC / DC module is the source of EMC interference. The existing EMC solution is mainly to connect the EMC filter circuit to the main circuit of the power supply (such as Figure 1 As shown in the figure, the conducted interference is filtered out on the main circuit path of the power supply. The filter inductor is required in the three working modes of fast charging, current limiting charging and high current discharging: during fast charging, the path is the positive terminal P+ of the charger → EMC filter circuit → positive electrode B+ of the battery pack, negative electrode B- of the battery pack → negative terminal switch (discharging, charging) → EMC filter circuit → negative terminal P- of the charger, and the charging current is 100A; during current limiting charging, the path is the positive terminal P+ of the charger → EMC filter circuit → positive electrode B+ of the battery pack, negative electrode B- of the battery pack → negative terminal switch (discharging) → current limiting charging DC / DC module → EMC filter circuit → negative terminal P- of the charger, and the charging current is limited to 10A; during high current discharging, the positive electrode B+ of the battery pack → EMC filter circuit → positive terminal P+ of the charger → negative terminal P- of the charger → EMC filter circuit → negative terminal switch (discharging, charging) → negative terminal B- of the battery pack, and the discharge current is 100A. Among them, the role of the anti-reverse switch is: on the one hand, it connects the input and output filter capacitors and freewheeling diodes to the positive electrode B+ of the battery pack by conduction to ensure the normal operation of the BUCK circuit topology; on the other hand, it controls the disconnection in the abnormal case of reverse connection of the charger to prevent circuit damage.
[0003] The components of the EMC filter circuit in the above EMC solution must be designed with high power as the main power circuit. The larger the power, the larger the volume and the higher the cost. For example, when the current reaches 100A, the system is basically faced with the limitation of space and the pressure of sharply rising costs. Therefore, in some cases, it is even necessary to compromise the design by reducing the power, which obviously cannot truly meet customer needs. Summary of the invention
[0004] The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a communication battery current limiting charging system which has a simple structural design, a small PCBA volume, a low cost, and can effectively solve the EMC problem of current limiting charging.
[0005] The technical solution adopted by the present invention to solve its technical problems is: a communication battery current limiting charging system, including a charger, a charging current limiting DC-DC conversion circuit, a negative end switch and a battery pack, and also including an input EMC filter circuit, an output EMC filter circuit, a positive end switch and an anti-reverse switch. The positive end of the charger is connected to the positive electrode of the battery pack through the positive end switch, and the negative end is connected to the negative electrode of the battery pack through the negative end switch. The first end of the input EMC filter circuit is connected to the common end of the charger positive end and the positive end switch through the anti-reverse switch, and the output EMC end is connected to the negative end of the charger. The first end of the output EMC filter circuit is connected to the positive electrode of the battery pack, and the second end is connected to the negative end switch. The input EMC filter circuit is connected to the output EMC filter circuit through the charging current limiting DC-DC conversion circuit.
[0006] Furthermore, the charging current limiting DC-DC conversion circuit includes an air-core inductor L, a transistor Q, a diode D, filters C1, C2, a resistor R, a control chip, a first drive chip and an auxiliary power supply. Pin 1 of the air-core inductor L is connected to the drain of the transistor Q, and its pin 2 is connected to the source of the transistor Q through filters C1, C2 and resistor R in sequence. One end of the diode D is connected to the common end of the air-core inductor L and the transistor Q, and the other end is connected to the common end of the filters C1 and C2. The common end of the air-core inductor L and the filter C1 is connected to the output EMC filter circuit, the common end of the transistor Q and the filter C2 is connected to the input EMC filter circuit, and the common ends of the filters C1 and C2 are respectively connected to the input EMC filter circuit and the output EMC filter circuit. The two ends of the resistor R are respectively connected to the control chip, the control chip is respectively connected to the first drive chip and the auxiliary power supply, the auxiliary power supply is connected to the common end of the filters C1 and C2, and the first drive chip is respectively connected to the gate of the transistor Q and the auxiliary power supply.
[0007] Furthermore, the negative terminal switch and the positive terminal switch are transistors, relays or switch circuits.
[0008] Further, the input EMC filter circuit includes a common-mode inductor L1, capacitors C3, C4, C5, C6, C7, and C8, pin 1 of the common-mode inductor L1 is connected to the common end of the charger positive terminal and the positive switch through an anti-reverse switch, and its pin 2 is connected to the negative terminal of the charger, one end of the capacitor C3 is connected to pin 1 of the common-mode inductor L1, and the other end is connected to pin 2 of the common-mode inductor L1, one end of the capacitor C4 is connected to pin 1 of the common-mode inductor L1, and the other end is connected to pin 2 of the common-mode inductor L1 through capacitor C5, pins 3 and 4 of the common-mode inductor L1 are respectively connected to the charging current limiting DC-DC conversion circuit, one end of the capacitor C6 is connected to pin 3 of the common-mode inductor L1, and the other end is connected to pin 4 of the common-mode inductor L1, one end of the capacitor C7 is connected to pin 3 of the common-mode inductor L1, and the other end is connected to pin 4 of the common-mode inductor L1 through capacitor C8.
[0009] Furthermore, the output EMC filter circuit includes a common-mode inductor L2, capacitors C9, C10, C11, C12, C13, and C14, pins 1 and 2 of the common-mode inductor L2 are respectively connected to the charging current limiting DC-DC conversion circuit, one end of the capacitor C9 is connected to pin 1 of the common-mode inductor L2, and the other end thereof is connected to pin 2 of the common-mode inductor L2, one end of the capacitor C10 is connected to pin 1 of the common-mode inductor L2, and the other end thereof is connected to pin 2 of the common-mode inductor L2 through capacitor C11, pin 3 of the common-mode inductor L2 is connected to the positive electrode of the battery pack, and pin 4 thereof is connected to the negative terminal switch, one end of the capacitor C12 is connected to pin 3 of the common-mode inductor L2, and the other end thereof is connected to pin 4 of the common-mode inductor L2, one end of the capacitor C13 is connected to pin 3 of the common-mode inductor L2, and the other end thereof is connected to pin 4 of the common-mode inductor L2 through capacitor C14.
[0010] Furthermore, the negative end switch includes a discharge switch Q1 and a charging switch Q2, the source of the discharge switch Q1 is connected to the negative terminal of the battery pack, and its drain is connected to the drain of the charging switch Q2, the source of the charging switch Q2 is connected to the negative terminal of the charger, and the pin 4 of the common mode inductor L2 is connected to the common terminal of the discharge switch Q1 and the charging switch Q2.
[0011] Furthermore, it also includes a control circuit, which includes a main control chip, a second drive chip, a first drive circuit and a second drive circuit. The positive end switch is connected to the main control chip through the second drive chip, the anti-reverse switch is connected to the main control chip through the first drive circuit, and the negative end switch is connected to the main control chip through the second drive circuit.
[0012] The beneficial effects of the present invention are:
[0013] (1) The present invention adds a positive switch and a positive filter in parallel bypass, and a negative switch in the original circuit in parallel bypass with a negative filter, cuts off the positive switch and the negative switch (charging), so that the charging path only passes through the charging current limiting DC-DC conversion circuit with a filter bypass in the middle, starts the charging current limiting DC-DC conversion circuit and turns on the anti-reverse switch, so that the current flowing through the input EMC filter circuit and the output EMC filter circuit is a small current (such as 10A), then the components of the input EMC filter circuit and the output EMC filter circuit only need to meet the small current design, which reduces the PCBA volume, greatly reduces the material cost, is easy to implement, and is competitive in performance, delivery and cost.
[0014] (2) The present invention retains the negative-end switch in the main power circuit and adds a positive-end switch to cut off the positive-end circuit of the charger, thereby blocking the conduction interference that may leak from the internal circuit along the positive end of the charger; at the same time, the positive-end switch, as a protection device, meets higher safety standards and plays a secondary protection role in the event of a failure of the negative-end switch (i.e., a single-point failure of the protection device), thereby enhancing the safety of the battery pack.
[0015] (3) The present invention adds an output EMC filter circuit at the output end of the charging current limiting DC-DC conversion circuit, so that the interference generated by the charging current limiting DC-DC conversion circuit is blocked between its input and output ends and does not leak out, and the conducted interference is more thoroughly filtered out inside the interference source.
[0016] (4) While ensuring the original function of the anti-reverse switch, the present invention takes into account the reliability design of the anti-reverse switch, the positive end switch and the EMC filter device in the selection and control logic. The anti-reverse switch and the positive end switch perform synchronous reverse logic control, that is, when the positive end switch is turned on, the anti-reverse switch is turned off, and the current limiting charging stops; when the positive end switch is turned off, the anti-reverse switch is turned on, and the current limiting charging starts. The above control ensures the stability of the switching between fast charging and current limiting charging, especially considering the backup power scenario. After the city power is cut off, when the current limiting charging switches to the discharge operation, at the transition moment when the positive end switch turns on and the anti-reverse switch turns off but has not yet been executed, the anti-reverse switch, the EMC filter device and the circuit in which they are located can withstand an overcurrent capacity of more than 100A to meet the demand for uninterrupted power supply. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The present invention is further described below in conjunction with the accompanying drawings and embodiments.
[0018] Figure 1 It is a circuit framework diagram of the prior art;
[0019] Figure 2 It is a circuit framework diagram of the present invention;
[0020] Figure 3 It is a circuit schematic diagram of the present invention.
[0021] In the figure: 1. Charger; 2. Charging current limiting DC-DC conversion circuit; 3. Negative end switch; 4. Battery pack; 5. Input EMC filter circuit; 6. Output EMC filter circuit; 7. Positive end switch; 8. Anti-reverse switch; 9. Control circuit. DETAILED DESCRIPTION
[0022] The present invention will now be further described in conjunction with the accompanying drawings and preferred embodiments. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.
[0023] like Figure 2 As shown, a communication battery current limiting charging system includes a charger 1, a charging current limiting DC-DC conversion circuit 2, a negative terminal switch 3, a battery pack 4, an input EMC filter circuit 5, an output EMC filter circuit 6, a positive terminal switch 7 and an anti-reverse switch 8. The positive terminal of the charger 1 is connected to the positive electrode of the battery pack 4 through the positive terminal switch 7, and its negative terminal is connected to the negative electrode of the battery pack 4 through the negative terminal switch 3. The first end of the input EMC filter circuit 5 is connected to the common end of the positive terminal of the charger 1 and the positive terminal switch 7 through the anti-reverse switch 8, and the second end is connected to the negative terminal of the charger 1. The first end of the output EMC filter circuit 6 is connected to the positive electrode of the battery pack 4, and the second end is connected to the negative terminal switch 3. The input EMC filter circuit 5 is connected to the output EMC filter circuit 6 through the charging current limiting DC-DC conversion circuit 2. Add a positive-end switch 7 and a positive-end filter bypass in parallel, and a negative-end switch 3 of the original circuit and a negative-end filter bypass in parallel, cut off the positive-end switch 7 and the negative-end switch 3 (charging), so that the charging path only passes through the charging current-limited DC-DC conversion circuit 2 with a filter bypass in the middle, start the charging current-limited DC-DC conversion circuit 2 and turn on the anti-reverse switch 8, so that the current flowing through the input EMC filter circuit 5 and the output EMC filter circuit 6 is a small current (such as 10A), then the components of the input EMC filter circuit 5 and the output EMC filter circuit 6 only need to meet the small current design, which reduces the PCBA volume, greatly reduces the material cost, is easy to implement, and is competitive in performance, delivery and cost. On the basis of retaining the negative terminal switch 3 in the main power circuit, a positive terminal switch 7 is added to cut off the positive terminal circuit of the charger 1, blocking the conduction interference that may leak from the internal circuit along the positive terminal of the charger 1; at the same time, as a protection device, the positive terminal switch 7 meets higher safety standards, and plays a secondary protection role in the case of failure and breakdown of the negative terminal switch 3 (i.e., single-point failure of the protection device), thereby enhancing the safety of the battery pack 4. Specifically, the negative terminal switch 3 and the positive terminal switch 7 are transistors, relays or switch circuits; the anti-reverse switch 8 can be a MOS tube, a relay, etc.
[0024] On the basis of ensuring the original function of the anti-reverse switch 8, the anti-reverse switch 8, the positive switch 7 and the EMC filter device have taken into account the reliability design in the selection and control logic. The anti-reverse switch 8 and the positive switch 7 perform synchronous anti-logic control, that is, when the positive switch 7 is turned on, the anti-reverse switch 8 is disconnected, and the current limiting charging stops; when the positive switch 7 is disconnected, the anti-reverse switch 8 is turned on, and the current limiting charging starts; the above control ensures the stability of the switching between fast charging and current limiting charging, especially considering the backup power scenario. After the city power is cut off, when the current limiting charging is switched to discharging, at the transition moment when the positive switch 7 is turned on and the anti-reverse switch 8 is turned off, the anti-reverse switch 8, the EMC filter device and the line where they are located can withstand an overcurrent capacity of more than 100A to meet the needs of uninterrupted power supply.
[0025] like Figure 3 As shown, the charging current limiting DC-DC conversion circuit 2 includes an air-core inductor L, a transistor Q, a diode D, filters C1, C2, a resistor R, a control chip, a first drive chip and an auxiliary power supply. Pin 1 of the air-core inductor L is connected to the drain of the transistor Q, and its pin 2 is connected to the source of the transistor Q through filter capacitors C1, C2 and the resistor R in sequence. One end of the diode D is connected to the common end of the air-core inductor L and the transistor Q, and the other end is connected to the common end of the filters C1 and C2. The common end of the air-core inductor L and the filter C1 is connected to the output EMC filter circuit 6, the common end of the filter C2 and the resistor R is connected to the input EMC filter circuit 5, the common end of the filters C1 and C2 is respectively connected to the input EMC filter circuit 5 and the output EMC filter circuit 6, the two ends of the resistor R are respectively connected to the control chip, the control chip is respectively connected to the first drive chip and the auxiliary power supply, the auxiliary power supply is connected to the common end of the filters C1 and C2, and the first drive chip is respectively connected to the gate of the transistor Q and the auxiliary power supply. The setting of the charging current limiting DC-DC conversion circuit 2 limits the input current of the charger 1 to a set small current value to charge the battery pack 4 when the main charging power (such as current 100A) circuit is cut off, so as to ensure charging safety.
[0026] like Figure 3As shown, the input EMC filter circuit 5 includes a common-mode inductor L1, capacitors C3, C4, C5, C6, C7, and C8. Pin 1 of the common-mode inductor L1 is connected to the common end of the positive end of the charger 1 and the positive end switch 7 (i.e., transistor Q3) through the anti-reverse switch 8, and its pin 2 is connected to the negative end of the charger 1. One end of the capacitor C3 is connected to pin 1 of the common-mode inductor L1, and the other end is connected to pin 2 of the common-mode inductor L1. One end of the capacitor C4 is connected to pin 1 of the common-mode inductor L1, and the other end is connected to pin 2 of the common-mode inductor L1 through the capacitor C5. Pins 3 and 4 of the common-mode inductor L1 are respectively connected to the charging current limiting DC-DC conversion circuit 2. One end of the capacitor C6 is connected to pin 3 of the common-mode inductor L1, and the other end is connected to pin 4 of the common-mode inductor L1. One end of the capacitor C7 is connected to pin 3 of the common-mode inductor L1, and the other end is connected to pin 4 of the common-mode inductor L1 through the capacitor C8. Specifically, a common end of the capacitors C4 and C5 is grounded; a common end of the capacitors C7 and C8 is grounded.
[0027] like Figure 3 As shown, the output EMC filter circuit 6 includes a common-mode inductor L2, capacitors C9, C10, C11, C12, C13, and C14. Pins 1 and 2 of the common-mode inductor L2 are respectively connected to the charging current limiting DC-DC conversion circuit 2. One end of the capacitor C9 is connected to pin 1 of the common-mode inductor L2, and the other end thereof is connected to pin 2 of the common-mode inductor L2. One end of the capacitor C10 is connected to pin 1 of the common-mode inductor L2, and the other end thereof is connected to pin 2 of the common-mode inductor L2 through capacitor C11. Pin 3 of the common-mode inductor L2 is connected to the positive electrode of the battery pack 4, and pin 4 thereof is connected to the negative terminal switch 3. One end of the capacitor C12 is connected to pin 3 of the common-mode inductor L2, and the other end thereof is connected to pin 4 of the common-mode inductor L2. One end of the capacitor C13 is connected to pin 3 of the common-mode inductor L2, and the other end thereof is connected to pin 4 of the common-mode inductor L2 through capacitor C14. An output EMC filter circuit 6 is added to the output end of the charging current limiting DC-DC conversion circuit 2, so that the interference generated by the charging current limiting DC-DC conversion circuit 2 is contained between its input and output ends and does not leak out, and the conducted interference is more thoroughly filtered out inside the interference source. Specifically, the common end of the capacitors C10 and C11 is grounded; the common end of the capacitors C13 and C14 is grounded.
[0028] It should be noted that the input EMC filter circuit 5 and the output EMC filter circuit 6 are not limited to the above circuit forms, but also include other circuit forms composed of components such as common mode inductors, differential mode inductors, X capacitors and Y capacitors adjusted according to actual conditions.
[0029] like Figure 3As shown, the negative end switch 3 includes a discharge switch Q1 and a charging switch Q2, the source of the discharge switch Q1 is connected to the negative terminal of the battery pack 4, and its drain is connected to the drain of the charging switch Q2, the source of the charging switch Q2 is connected to the negative terminal of the charger 1, and the pin 4 of the common mode inductor L2 is connected to the common terminal of the discharge switch Q1 and the charging switch Q2.
[0030] The communication battery current limiting charging system also includes a control circuit 9 for controlling the positive terminal switch 7, the anti-reverse switch 8 and the negative terminal switch 3. The control circuit 9 includes a main control chip, a second drive chip, a first drive circuit and a second drive circuit. The positive terminal switch 7 is connected to the main control chip through the second drive chip, the anti-reverse switch 8 is connected to the main control chip through the first drive circuit, and the negative terminal switch 3 is connected to the main control chip through the second drive circuit. Specifically, the second drive circuit is connected to the gate of the discharge switch Q1 and the gate of the charging switch Q2 respectively.
[0031] like Figure 2 As shown, during fast charging, "loop 1" is used, the current limiting circuit does not work, and the path is the positive terminal P+ of charger 1→positive terminal switch 7→positive electrode B+ of battery pack 4, negative electrode B- of battery pack 4→negative terminal switch 3→negative terminal P- of charger 1, and the charging current is 100A; during current limiting charging, "loop 2" is used, at this time, the positive terminal switch 7 is disconnected, and the path is the positive terminal P+ of charger 1→input EMC filter circuit 5→charging current limiting DC-DC conversion circuit 2→output EMC filter circuit 6→positive electrode B+ of battery pack 4, negative electrode B- of battery pack 4→output EMC filter circuit 6→charging current limiting DC-DC conversion circuit 2→input EMC filter circuit 5→negative terminal P- of charger 1, and the charging current is 10A. By adding the positive terminal switch 7 to change the path, fast charging and current limiting charging are separated into two independent working paths. The present invention realizes more, more reliable and safer functions at a lower price.
[0032] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.
Claims
1. A communication battery current limiting charging system, comprising a charger (1), a charging current limiting DC-DC conversion circuit (2), a negative terminal switch (3) and a battery pack (4), characterized in that: The device also comprises an input EMC filter circuit (5), an output EMC filter circuit (6), a positive terminal switch (7) and an anti-reverse switch (8); the positive terminal of the charger (1) is connected to the positive terminal of the battery pack (4) through the positive terminal switch (7), and the negative terminal thereof is connected to the negative terminal of the battery pack (4) through the negative terminal switch (3); the first terminal of the input EMC filter circuit (5) is connected to the common terminal of the positive terminal of the charger (1) and the positive terminal switch (7) through the anti-reverse switch (8), and the second terminal thereof is connected to the negative terminal of the charger (1); the first terminal of the output EMC filter circuit (6) is connected to the positive terminal of the battery pack (4), and the second terminal thereof is connected to the negative terminal switch (3); the input EMC filter circuit (5) is connected to the output EMC filter circuit (6) through a charging current limiting DC-DC conversion circuit (2).
2. The communication battery current limiting charging system according to claim 1 is characterized in that: The charging current limiting DC-DC conversion circuit (2) comprises an air-core inductor L, a transistor Q, a diode D, filters C1, C2, a resistor R, a control chip, a first drive chip and an auxiliary power supply. Pin 1 of the air-core inductor L is connected to the drain of the transistor Q, and pin 2 of the air-core inductor L is connected to the source of the transistor Q through filters C1, C2 and the resistor R in sequence. One end of the diode D is connected to the common end of the air-core inductor L and the transistor Q, and the other end of the diode D is connected to the common end of the filters C1 and C2. The common end of the air-core inductor L and the filter C1 is connected to the output EMC filter circuit (6). The common end of the filter C2 and the resistor R is connected to the input EMC filter circuit (5). The common ends of the filters C1 and C2 are respectively connected to the input EMC filter circuit (5) and the output EMC filter circuit (6). Both ends of the resistor R are respectively connected to the control chip. The control chip is respectively connected to the first drive chip and the auxiliary power supply. The auxiliary power supply is connected to the common end of the filters C1 and C2. The first drive chip is respectively connected to the gate of the transistor Q and the auxiliary power supply.
3. The communication battery current limiting charging system according to claim 1, characterized in that: The negative end switch (3) and the positive end switch (7) are transistors, relays or switch circuits.
4. The communication battery current limiting charging system according to claim 1, characterized in that: The input EMC filter circuit (5) comprises a common-mode inductor L1, capacitors C3, C4, C5, C6, C7 and C8, wherein pin 1 of the common-mode inductor L1 is connected to the common end of the positive end of the charger (1) and the positive end switch (7) through an anti-reverse switch (8), and pin 2 of the common-mode inductor L1 is connected to the negative end of the charger (1), one end of the capacitor C3 is connected to pin 1 of the common-mode inductor L1, and the other end of the capacitor C3 is connected to pin 2 of the common-mode inductor L1, one end of the capacitor C4 is connected to pin 1 of the common-mode inductor L1, and the other end of the capacitor C4 is connected to pin 2 of the common-mode inductor L1 through capacitor C5, pins 3 and 4 of the common-mode inductor L1 are respectively connected to a charging current limiting DC-DC conversion circuit (2), one end of the capacitor C6 is connected to pin 3 of the common-mode inductor L1, and the other end of the capacitor C6 is connected to pin 4 of the common-mode inductor L1, one end of the capacitor C7 is connected to pin 3 of the common-mode inductor L1, and the other end of the capacitor C7 is connected to pin 4 of the common-mode inductor L1 through capacitor C8.
5. The communication battery current limiting charging system according to claim 1, characterized in that: The output EMC filter circuit (6) comprises a common-mode inductor L2, capacitors C9, C10, C11, C12, C13, and C14, wherein pins 1 and 2 of the common-mode inductor L2 are respectively connected to the charging current-limiting DC-DC conversion circuit (2), one end of the capacitor C9 is connected to pin 1 of the common-mode inductor L2, and the other end thereof is connected to pin 2 of the common-mode inductor L2, one end of the capacitor C10 is connected to pin 1 of the common-mode inductor L2, and the other end thereof is connected to pin 2 of the common-mode inductor L2 through capacitor C11, pin 3 of the common-mode inductor L2 is connected to the positive electrode of the battery pack (4), and pin 4 thereof is connected to the negative terminal switch (3), one end of the capacitor C12 is connected to pin 3 of the common-mode inductor L2, and the other end thereof is connected to pin 4 of the common-mode inductor L2, one end of the capacitor C13 is connected to pin 3 of the common-mode inductor L2, and the other end thereof is connected to pin 4 of the common-mode inductor L2 through capacitor C14.
6. The communication battery current limiting charging system according to claim 5, characterized in that: The negative end switch (3) comprises a discharge switch Q1 and a charge switch Q2, the source of the discharge switch Q1 being connected to the negative terminal of the battery pack (4), and the drain of the discharge switch Q1 being connected to the drain of the charge switch Q2, the source of the charge switch Q2 being connected to the negative terminal of the charger (1), and the pin 4 of the common mode inductor L2 being connected to the common terminal of the discharge switch Q1 and the charge switch Q2.
7. The communication battery current limiting charging system according to claim 1, characterized in that: The device also comprises a control circuit (9), wherein the control circuit (9) comprises a main control chip, a second drive chip, a first drive circuit and a second drive circuit, wherein the positive end switch (7) is connected to the main control chip via the second drive chip, the anti-reverse switch (8) is connected to the main control chip via the first drive circuit, and the negative end switch (3) is connected to the main control chip via the second drive circuit.