Device and method for current limiting equalization charging of battery pack

Abstract

The present disclosure provides a device and method for current-limited equalization charging of a battery pack. A device for charging a battery pack includes: a main power supply, whose negative pole is coupled to the negative pole of the battery pack, and the main power supply is configured to provide a direct current; an inverter unit, whose positive pole at the input end is coupled to the positive pole of the main power supply, and whose negative pole at the input end is coupled to the positive pole of the battery pack, and the inverter unit is configured to convert the direct current provided by the main power supply into a high-frequency alternating current, and adjust the charging current of the battery pack by controlling the inverter unit; a transformer unit, including a primary winding and a plurality of secondary windings, and the primary winding is coupled to the output end of the inverter unit; a plurality of rectifier units, the input end of each rectifier unit is coupled to the corresponding secondary winding of the transformer unit, the output end of each rectifier unit is coupled to the corresponding battery in the battery pack, and each rectifier unit is configured to convert the high-frequency alternating current input from the corresponding secondary winding of the transformer unit into a direct current.

Description

Technical Field

[0001] The present disclosure relates to the technical field of battery charging, and in particular to a device and method for current limiting and equalizing charging of a battery pack. Background Art

[0002] At present, the batteries used in communication base stations are mainly lead-acid batteries. The technology of lead-acid batteries has a long history of development. Due to its low cost, mature technology, and easy maintenance, it has always been one of the most widely used energy storage batteries in current communication power supplies. However, lead-acid batteries have some difficult-to-solve problems due to their theoretical characteristics and product characteristics, such as short cycle life, low energy density, easy theft, and environmental pollution. Therefore, there is an urgent need for energy storage devices with excellent performance and not too much increase in comprehensive costs to replace traditional lead-acid batteries.

[0003] Lithium batteries are commonly used in the field of mobile phones, but they can also be used as backup power supplies in communication base stations, and they have excellent performance. From an environmental perspective, lithium batteries do not contain harmful heavy metals that can cause pollution, such as cadmium, lead, and mercury. They will not cause pollution that harms human health during production and use, and will not pollute water sources and soil during the recycling of waste batteries. From the perspective of battery performance, lithium batteries have advantages that lead-acid batteries do not have. The cycle life, high temperature characteristics, charge and discharge rate performance, and energy density of lithium batteries are all better than lead-acid batteries. For example, the volume and weight of lithium batteries of the same capacity are one-half to one-third of those of lead-acid batteries, and they can be connected and placed arbitrarily, with no special requirements for building space and load-bearing capacity, which greatly reduces the cost of renting a site. In addition, the excellent high temperature characteristics of lithium batteries can reduce the configuration and power consumption of air conditioners in base stations. After a lithium battery is stolen, its recycling value is not great, because lithium batteries require a battery management system, so they cannot be used directly, thereby reducing the risk of backup power being stolen.

[0004] Currently, due to the advantages of lithium batteries such as long life and low maintenance and replacement costs, the TCO (Total Cost of Ownership) of lithium batteries during their life cycle is even lower than that of lead-acid batteries. In the future, as the electric vehicle and energy storage industries develop, lithium battery applications will continue to scale up, and their prices will become lower and lower, becoming more and more competitive. The advantages of lithium batteries in differentiated scenarios are more prominent. In areas with poor power grids, they can be used as circulating backup power. Taking advantage of their long cycle life, lithium batteries can be configured with much less capacity than lead-acid batteries to meet short-term backup requirements, saving space and costs.

[0005] Lithium batteries used for communication energy storage need to be used in conjunction with an excellent battery management system in order to be truly safe and stable. The theoretical characteristics of lithium batteries determine that they are sensitive to overcharging and over-discharging. Due to the short development time of lithium batteries, the industry has not conducted in-depth research on issues such as their consistency, stability, large-scale series and parallel connection, and temperature control. Therefore, it is necessary to focus on the research and development of battery management systems in order to use lithium batteries more effectively and safely. General battery management systems can only guarantee the basic safety of lithium battery packs. Good battery management systems can extend the service life of lithium battery packs, discover safety and performance risks, and reduce failure rates. In the future, as energy storage lithium batteries are mass-produced and costs continue to decline, lithium batteries will play an increasingly important role in the field of communication backup power supplies.

[0006] In the backup power supply system of communication base stations, lithium battery packs have been widely used and promoted. However, during the use of lithium batteries, the batteries must be strictly managed to ensure safety and stable performance. For example, the DC power supply in the communication base station usually operates at a stable equalization charging voltage of 54V or an equalization charging voltage of 56.4V. In the case of a lithium battery pack, taking a ternary lithium battery as an example, 13 cells are generally connected in series, and taking a lithium iron phosphate battery as an example, 16 cells are generally connected in series. When the mains power is cut off, the lithium battery pack begins to discharge, and the lowest discharge voltage of the communication lithium battery pack may be, for example, 40V or even lower. When the mains power is restored, the original high-power base station communication switch power supply system in the base station charges the lithium battery pack. The floating charge voltage of the communication switch power supply is set to, for example, 54V according to the lead-acid battery pack. At this time, if the 40V lithium battery is charged without current limiting, because the internal resistance of the lithium battery pack is very small, the current will be very large, exceeding the charging rate that the lithium battery can withstand, and it may burn the lithium battery pack, causing safety hazards. Therefore, it is necessary to limit the charging of the lithium battery pack used in the communication base station.

[0007] In a communication lithium battery pack (for example, a 16-series lithium iron phosphate battery pack or a 13-series ternary lithium battery pack), the performance and life of the battery pack are significantly lower than those of a single battery, mainly due to the consistency of the battery. Since it is difficult to achieve complete consistency for a single battery in series, this will cause inconsistency in the voltage of each battery during the charging process, and in the later stages of charging, individual batteries may be over-voltage, resulting in abnormal and rapid degradation of lithium battery performance, and even safety hazards. Therefore, it is necessary to perform voltage balancing on the single batteries in the series lithium battery pack.

[0008] Although batteries can be screened at the factory to keep them as consistent as possible, screening will increase the cost of battery production. Moreover, during the use of batteries in groups, the different operating conditions of each battery will gradually cause inconsistency of the batteries. Inconsistency of batteries may cause the performance of lithium battery packs to decay too quickly and significantly shorten their lifespan.

[0009] Battery balancing usually refers to the voltage balancing of each battery in a series battery pack. Battery balancing is generally divided into passive balancing and active balancing. Both balancing schemes are currently used in battery packs.

[0010] Passive balancing generally refers to the method of balancing batteries through resistor discharge. Passive balancing appeared before active balancing. Because of its simple circuit and low cost, it is still widely used. The principle of passive balancing is to discharge the energy of high-voltage batteries through resistors according to the characteristics of the positive correlation between battery power and voltage, and to keep the power of low-voltage batteries equal to that of low-voltage batteries according to the voltage data of single-string batteries; the highest voltage can also be used as a criterion. For example, the highest voltage of ternary lithium batteries is 4.2V, and once it exceeds 4.2V, discharge balancing begins. The work of passive balancing is to "cut the long without making up for the short". The energy in the battery with high power is dissipated as heat, and the efficiency of power use is low. Not only that, because the power is converted into heat dissipation, it brings a dilemma: if the balancing current is large, the heat dissipated is large, and how to dissipate heat will become a problem; if the balancing current is small, then the efficiency of balancing the power is very low when the power difference in large-capacity battery packs is large, and it takes a long time to achieve balance, which is less effective in applications. Weighing the pros and cons, the current of passive balancing is generally at the level of 100 mA.

[0011] Active balancing generally refers to a method of solving battery consistency problems by transferring energy. The benefits of active balancing are obvious: high efficiency, most of the energy is transferred, and the loss is only the transformer coil loss, which accounts for a small proportion of the total energy; the balancing current can be designed to be relatively large, reaching several amperes or even 10A, and the balancing effect is fast. Compared with passive balancing, active balancing circuits are more complex, less reliable, and more expensive, but the balancing current and power are larger, especially when the battery consistency problem is serious, active balancing is particularly effective.

[0012] In order to solve the problem that the voltage of lithium battery packs is low after discharge and the current is too large when charging starts, the existing partial charging technology of lithium battery packs in communication base stations does not limit the current of battery pack charging, resulting in excessive current when the battery starts charging after discharge, and a high failure rate.

[0013] Therefore, it is necessary to design a new circuit that integrates current limiting charging and voltage balancing, and simultaneously solves the current limiting charging problem and voltage balancing problem in the charging process of the communication base station lithium battery pack, so as to achieve the effect of charging the lithium battery pack in an energy-saving and environmentally friendly manner. Summary of the invention

[0014] According to a first aspect of the present disclosure, there is provided a device for charging a battery pack, comprising: a main power supply, wherein the negative pole of the main power supply is coupled to the negative pole of the battery pack, and the main power supply is configured to provide a direct current; an inverter unit, wherein the positive pole of the input terminal of the inverter unit is coupled to the positive pole of the main power supply, and the negative pole of the input terminal of the inverter unit is coupled to the positive pole of the battery pack, and the inverter unit is configured to convert the direct current provided by the main power supply into a high-frequency alternating current, and adjust the charging current of the battery pack by controlling the inverter unit; a transformer unit, comprising a primary winding and a plurality of secondary windings, and the primary winding is coupled to the output terminal of the inverter unit; and a plurality of rectifier units, wherein the input terminal of each of the plurality of rectifier units is coupled to the corresponding secondary winding of the transformer unit, and the output terminal of each of the plurality of rectifier units is coupled to the corresponding battery in the battery pack, and each rectifier unit is configured to convert the high-frequency alternating current input from the corresponding secondary winding of the transformer unit into a direct current.

[0015] According to a second aspect of the present disclosure, a method for charging a battery pack is provided, comprising: charging the battery pack using the apparatus as described above.

[0016] One of the advantages of the embodiments disclosed herein is that it can integrate current limiting charging and voltage balancing, and simultaneously solve the current limiting charging problem and voltage balancing problem in the charging process of the communication base station lithium battery pack, thereby ensuring the safety, efficiency, energy saving and environmental protection of the charging process of the lithium battery pack.

[0017] Other features and advantages of the present disclosure will become more apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0019] The present disclosure can be more clearly understood from the following detailed description with reference to the accompanying drawings.

[0020] in:

[0021] Figure 1 The invention is a circuit diagram showing a step-down chopper current limiting circuit in the prior art.

[0022] Figure 2 is a circuit diagram illustrating a passive equalization circuit of the prior art.

[0023] Figure 3 is a schematic diagram illustrating an apparatus for charging a battery pack according to an embodiment of the present disclosure.

[0024] Figure 4is a circuit diagram illustrating an apparatus for charging a battery pack according to an embodiment of the present disclosure.

[0025] For ease of understanding, the position, size, range, etc. of each structure shown in the drawings and the like may not represent the actual position, size, range, etc. Therefore, the present disclosure is not limited to the position, size, range, etc. disclosed in the drawings and the like. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present disclosure.

[0027] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0028] It should also be understood that the terms used in this disclosure are only for the purpose of describing specific embodiments and are not intended to limit the disclosure. As used in the specification and appended claims of the disclosure, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0029] It should be further understood that the term “and / or” used in the specification of the present disclosure and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0030] Figure 1 The circuit diagram of a step-down chopper current limiting circuit of the prior art is shown. The current limiting circuit adopts a traditional step-down chopper circuit, the output average voltage Uo is less than the input voltage Ui, and the output voltage has the same polarity as the input voltage.

[0031] The chopper circuit converts a constant DC voltage or current into a series of pulse voltages or currents by quickly controlling the on-off of power electronic switching devices. By changing the on-off action frequency of the switching device, or changing the on-off time ratio of the switching device, the pulse width of the pulse voltage or current can be changed to adjust the average value of the output voltage or current. Although the chopper current limiting circuit can solve the problem of excessive charging current, the circuit function is single and cannot achieve equalization of battery voltage while limiting current charging.

[0032] To solve the voltage balancing problem of series-connected batteries in a lithium battery pack, a passive balancing circuit with resistor discharge is generally used to balance the voltage of the battery pack. Figure 2 The passive balancing circuit of the prior art is shown in the figure. The passive balancing circuit has a small balancing current and poor balancing effect, which cannot well meet the performance requirements of the battery pack for balancing, and is insufficient for ensuring the performance and extending the life of the battery. In addition, the passive balancing consumes energy and generates heat, which is not conducive to energy saving and environmental protection.

[0033] The present disclosure provides a circuit capable of performing current limiting charging while performing battery charge balancing, and can overcome the defects and problems existing in the above-mentioned two common circuits of the prior art.

[0034] Figure 3 is a schematic diagram illustrating an apparatus for charging a battery pack 5 according to an embodiment of the present disclosure. The battery pack 5 includes a plurality of batteries connected in series, for example Figure 3 As shown, the multiple batteries connected in series may include batteries B1, B2, ..., Bn (n is an integer not less than 2), and each battery B1, B2, ..., Bn is respectively coupled to a rectifier unit 4. In one embodiment, n can be 13, that is, the battery pack includes 13 batteries B1, B2, ..., B13 connected in series, and batteries B1, B2, ..., B13 can be batteries obtained by connecting 36 2500mAh ternary 18650 batteries in parallel, and the battery pack 5 composed is nominally 48V 90Ah. The advantages of ternary high energy density batteries are small size and light weight. In other embodiments, the battery pack 5 can be composed of multiple storage batteries or other types of lithium batteries, and is not limited to the 2500mAh ternary 18650 batteries mentioned above.

[0035] like Figure 3 As shown, the charging device may include: a main power supply 1, an inverter unit 2, a transformer unit 3, and a plurality of rectifier units 4. The main power supply 1 may be used to provide a DC current for charging; the inverter unit 2 may be used to convert the DC current provided by the main power supply 1 into a PWM high-frequency AC current; the transformer unit 3 may be used to isolate and transform the PWM high-frequency AC current output by the inverter unit 2 to output a plurality of transformed AC currents; the plurality of rectifier units 4 may be used to rectify the transformed AC current into a DC current; the input current of the inverter unit 2 may be adjusted by PWM to adjust the pulse width of the inverter unit 2, and then the output current of the plurality of rectifier units 4 may be adjusted, thereby realizing the regulation of the charging current of the battery pack 5. The charging current limiting and active balancing of the battery pack 5 are combined together to realize voltage balancing while realizing current limiting charging.

[0036] The main power source 1 may be a power source that provides a direct current for charging the battery pack 5. Figure 3As shown, the negative pole of the main power source 1 can be coupled to the negative pole of the battery pack 5 , and the positive pole of the main power source 1 can be coupled to the positive pole of the input terminal of the inverter unit 2 .

[0037] The inverter unit 2 may include a high-frequency switching power supply circuit, which converts direct current into PWM high-frequency alternating current. The inverter unit 2 may be controlled by performing pulse width modulation on the conduction pulse of the inverter unit 2. The positive pole of the input end of the inverter unit 2 is coupled to the positive pole of the main power supply 1, the negative pole of the input end of the inverter unit 2 is coupled to the positive pole of the battery pack 5, and the output end of the inverter unit 2 is coupled to the primary winding of the transformer unit 3.

[0038] Figure 4 FIG. 2 shows a circuit diagram of a device for charging a battery pack 5 according to an embodiment of the present disclosure. Figure 4 The high-frequency switching power supply circuit may include field effect transistors Q21, Q22, Q23, and Q24. The field effect transistors Q21, Q22, Q23, and Q24 may form a full-bridge circuit, and the positive electrode of the input end of the high-frequency switching power supply circuit may be coupled to the positive electrode of the main power supply 1, and the negative electrode of the input end of the high-frequency switching power supply circuit may be coupled to the positive electrode of the battery pack 5. The average input current of the inverter unit 2 may be adjusted by controlling the conduction pulse width of the field effect transistors Q21, Q22, Q23, and Q24 to limit the charging current of the battery pack 5.

[0039] Field effect transistors Q21, Q22, Q23, and Q24 can be used as high-frequency switches and work in a switching state, wherein field effect transistors Q21 and Q24 can be turned on or off at the same time, field effect transistors Q22 and Q23 can be turned on or off at the same time, field effect transistors Q21 and field effect transistors Q23 can be turned on and off alternately, and field effect transistors Q22 and field effect transistors Q24 can be turned on and off alternately.

[0040] By making the four field effect transistors work in the above-mentioned manner of conducting and / or cutting off, the current of the base station DC system charging the lithium battery pack 5 can be regulated. By controlling the conduction pulse width of the field effect transistors Q21, Q22, Q23, and Q24, the average input current of the inverter circuit can be adjusted, thereby limiting the charging current of the battery pack 5, and preventing the problem of excessive current when the battery pack 5 is discharged and the mains is restored to charge, thereby improving the reliability of the battery pack 5 and ensuring the stable and safe performance of the battery pack 5.

[0041] See also Figure 4, the four MOS tubes Q21, Q22, Q23, and Q24 work in the switching state, and each can be parasitic with an anti-parallel diode D21, D22, D23, and D24. A parasitic anti-parallel diode D21 can be connected in parallel between the source and drain of the field effect tube Q21; a parasitic anti-parallel diode D22 can be connected in parallel between the source and drain of the field effect tube Q22; a parasitic anti-parallel diode D23 can be connected in parallel between the source and drain of the field effect tube Q23; and a parasitic anti-parallel diode D24 can be connected in parallel between the source and drain of the field effect tube Q24. When Q21 and Q24 are turned off at the same time, due to the leakage inductance of the primary winding R31 of the transformer, a very high potential will be generated on Q21 and Q24, which may cause Q21 and Q24 to be broken down and damaged due to overvoltage. The existence of D22 and D23 allows the voltage on Q21 and Q24 to be limited to be lower than the main power supply voltage. Similarly, the existence of D21 and D24 can limit the voltage on Q22 and Q23 to be lower than the main power supply voltage, thereby ensuring the safety of the circuit.

[0042] In order to achieve current limiting charging and voltage balancing, it is necessary to control the input current of the inverter unit 2, and the control requires sampling of the actual current. Specifically, the charging device according to the present disclosure may include a current measuring unit, which can measure the current passing through the primary winding of the transformer unit 3. When the current passing through the primary winding is less than the current reference value, the width of the conduction pulse of the inverter unit 2 can be increased; and when the current passing through the primary winding is greater than or equal to the current reference value, the width of the conduction pulse of the inverter unit 2 can be reduced. In some embodiments, the current reference value can be designed based on the maximum charging current of the battery pack 5. In some embodiments, the current reference value can be adjustable. In some embodiments, taking into account the balanced charging of each battery by the secondary side of the transformer unit 3, the current reference value can be appropriately smaller than the design current of the battery pack 5.

[0043] In addition, in some embodiments, in order to avoid overvoltage and extend the service life of the battery, the charging current can be appropriately reduced when the voltage of the battery is close to the full voltage. Specifically, the charging device according to the present disclosure may include a voltage measuring unit, which can measure the total voltage across the battery pack 5. When the total voltage across the battery pack 5 is close to the full voltage of the battery pack 5, the primary current of the transformer unit 3 can be reduced, so as to prevent overvoltage charging and make the battery pack 5 gradually balanced and full. In addition, the voltage measuring unit can also measure the voltage across each battery in the battery pack 5. When the voltage across any battery in the battery pack 5 exceeds the maximum charging voltage, the primary current of the transformer unit 3 can be reduced, so as to prevent any battery from being overcharged. In some embodiments, reducing the primary current of the transformer unit 3 can be achieved by reducing the pulse width of the inverter unit 2. In some embodiments, reducing the pulse width of the inverter unit 2 can be achieved by reducing the current reference value described above.

[0044] By adjusting the pulse width of the inverter unit 2 through PWM, the input current of the inverter unit 2 is adjusted, and the output current of multiple rectifier units 4 is adjusted at the same time, so as to adjust the charging current of the battery pack 5. At the same time, the number of turns of the winding R32 of the transformer unit 3 connected to the rectifier unit 4 corresponding to each single battery is the same, so that the output voltage of the rectifier unit 4 is basically consistent, so as to achieve balanced charging of each single battery in the battery pack 5. By adjusting the pulse width of the inverter unit 2, the current limiting of the charging current can be achieved, which can achieve both maximum current limiting and constant current limiting.

[0045] In some embodiments, see Figure 4 , a filter capacitor C29 may be coupled between the main power supply 1 and the inverter unit 2. The filter capacitor C29 may be coupled between the positive electrode of the main power supply 1 and the negative electrode of the input terminal of the inverter unit 2. The positive electrode of the capacitor C29, the drain of the field effect transistor Q21, the cathode of the diode D21, the drain of the field effect transistor Q22, and the cathode of the diode D22 may be connected together so that the positive electrode of the input terminal of the inverter unit 2 and the positive electrode of the main power supply 1 are coupled together. The negative terminal of the capacitor C29, the source of the field effect transistor Q23, the anode of the diode D23, the source of the field effect transistor Q24, and the anode of the diode D24 may be connected together so that the negative electrode of the input terminal of the inverter unit 2 and the negative electrode of the main power supply 1 are coupled together. The filter capacitor C29 may filter the voltage when the output of the main power supply 1 is in a floating charge state, so that the voltage value input to the inverter unit 2 is more stable. For example, the main power supply 1 mentioned above may be a 48V power supply of a communication base station, which is generally in a floating charge state, and the voltage input to the inverter unit 2 may be 54V.

[0046] The transformer unit 3 may include a switching power converter with an isolation transformer, and include a primary winding and a plurality of secondary windings. The primary winding of the transformer unit 3 may be coupled to the output end of the inverter unit 2, thereby being coupled between the positive pole of the main power supply 1 and the positive pole of the battery pack 5. Each secondary winding of the transformer unit 3 may be coupled to the input end of a corresponding rectifier unit 4 among a plurality of rectifier units. In some embodiments, each battery in the battery pack 5 may be the same, and the number of turns of the plurality of secondary windings may be the same. In some embodiments, the number of secondary windings may be the same as the number of batteries in the battery pack 5. In some embodiments, the number of turns of the secondary winding may be adjustable.

[0047] See also Figure 4 The transformer unit 3 may include a primary winding R31 and a plurality of secondary windings R32 , and each secondary winding R32 is coupled to one of the plurality of rectifying units 4 .

[0048] The rectifier unit 4 may include a synchronous rectifier circuit. The input end of each rectifier unit 4 is coupled to the corresponding secondary winding of the transformer unit 3, and the output end of each rectifier unit 4 is coupled to the corresponding battery in the battery pack 5. In some embodiments, when each battery in the battery pack 5 is the same, it is necessary to make the charging voltage output by the rectifier unit 4 to each battery as consistent as possible, so as to achieve active balanced charging of each battery in the battery pack 5 while current limiting charging. The voltage balance of each battery in the series battery pack 5 can prevent overvoltage and damage caused by the inconsistency of individual batteries during the charging process, thereby extending the service life of the battery pack 5.

[0049] See also Figure 4 , the rectifier unit 4 may include field effect transistors Q41 and Q42. The rectifier unit 4 may use field effect transistors Q41 and Q42 for synchronous rectification, which may reduce the voltage difference and loss, thereby achieving energy-saving and environmentally friendly charging. The field effect transistors Q41 and Q42 may convert the AC power obtained by the isolation transformation of the transformer unit 3 into DC power, thereby charging each single battery in the battery pack 5.

[0050] See also Figure 4 A parasitic anti-parallel diode D41 may be connected in parallel between the source and drain of the field effect transistor Q41, and a parasitic anti-parallel diode D42 may be connected in parallel between the source and drain of the field effect transistor Q42. The parasitic anti-parallel diodes D41 and D42 can improve the stability and safety of the entire circuit.

[0051] Each battery can be coupled to a corresponding rectifier unit 4, and the voltages output by each rectifier unit 4 can be consistent. When the voltage of a battery in the battery pack 5 is low, the current of the battery can be increased accordingly; when the voltage of a battery in the battery pack 5 is high, the current of the battery can be reduced accordingly, thereby achieving active balancing.

[0052] In addition, in some embodiments, the output end of each rectifier unit 4 can be coupled to the corresponding battery through an LC filter circuit. Figure 4 The LC filter circuit may include a filter capacitor C45 and a filter inductor L46, wherein the filter capacitor C45 may be connected in parallel to the output end of the rectifier unit 4, and the filter inductor L46 may be connected in series between the positive electrode of the output end of the rectifier unit 4 and the positive electrode of the filter capacitor C4. The filter inductor L46 may filter the current passing through the rectifier unit 4, and the filter capacitor C45 may filter the current output by the rectifier unit 4.

[0053] As described above, the charging device according to the embodiment of the present disclosure can achieve current limiting of the charging current by adjusting the pulse width of the inverter unit, and can use the consistency of the voltage output by multiple rectifier units to balance the charging of each battery, that is, through balanced superposition charging, the active balanced charging of a single battery in the battery pack is achieved. The charging device realizes the integration of current limiting charging and voltage balancing, and can simultaneously solve the current limiting charging problem and voltage balancing problem in the charging process of the lithium battery pack in the communication base station, and has the effect of energy saving and environmental protection. Moreover, the charging device integrates the current limiting and balancing functions together, which simplifies the structure and reduces the cost compared with a separate current limiting device and a balancing device.

[0054] The charging device and the method for charging a battery pack using the charging device can be applied to communication base stations or other scenarios where batteries are required to provide electrical energy.

[0055] It should be noted that those skilled in the art can clearly understand that the specific implementation process of the current limiting and balancing method of the device for charging a battery pack can refer to the corresponding description in the embodiment of the device for charging a battery pack mentioned above. For the convenience and brevity of description, it will not be repeated here.

[0056] In summary, the present disclosure provides a device for charging a battery pack, comprising: a main power supply, wherein the negative pole of the main power supply is coupled to the negative pole of the battery pack, and the main power supply is configured to provide a direct current; an inverter unit, wherein the positive pole of the input end of the inverter unit is coupled to the positive pole of the main power supply, and the negative pole of the input end of the inverter unit is coupled to the positive pole of the battery pack, and the inverter unit is configured to convert the direct current provided by the main power supply into a high-frequency alternating current, and adjust the charging current of the battery pack by controlling the inverter unit; a transformer unit, comprising a primary winding and a plurality of secondary windings, and the primary winding is coupled to the output end of the inverter unit; a plurality of rectifier units, wherein the input end of each of the plurality of rectifier units is coupled to the corresponding secondary winding of the transformer unit, and the output end of each of the plurality of rectifier units is coupled to the corresponding battery in the battery pack, and each rectifier unit is configured to convert the high-frequency alternating current input from the corresponding secondary winding of the transformer unit into a direct current.

[0057] In some embodiments, the inverter unit includes a full-bridge circuit, and the inverter unit is controlled by performing pulse width modulation on a conduction pulse of the inverter unit.

[0058] In some embodiments, the device further includes a current measuring unit, which is configured to measure the current passing through the primary winding, and the device is further configured to: increase the width of the conduction pulse when the current passing through the primary winding is less than the current reference value; and reduce the width of the conduction pulse when the current passing through the primary winding is greater than or equal to the current reference value.

[0059] In some embodiments, the current reference value is set based on a maximum charging current of the battery pack.

[0060] In some embodiments, the current reference value is adjustable.

[0061] In some embodiments, the device further includes a voltage measuring unit configured to measure the voltage across the battery pack, and the device is further configured to reduce the current reference value when the difference between the voltage across the battery pack and the full voltage of the battery pack is less than the voltage difference reference value.

[0062] In some embodiments, the device further includes a voltage measuring unit configured to measure the voltage across the batteries in the battery pack, and the device is further configured to reduce the current reference value when the voltage across any battery in the battery pack exceeds the maximum charging voltage.

[0063] In some embodiments, each rectifying unit includes a synchronous rectifying circuit.

[0064] In some embodiments, each battery in the battery pack is identical and the number of turns of the plurality of secondary windings is identical.

[0065] In some embodiments, the number of turns of the secondary winding is adjustable.

[0066] In some embodiments, an output terminal of each rectifier unit among the plurality of rectifier units is coupled to a corresponding battery through an LC filter circuit.

[0067] In some embodiments, the apparatus further includes a filter capacitor coupled between a positive electrode of the main power source and a negative electrode of the input terminal of the inverter unit.

[0068] The present disclosure also provides a method for charging a battery pack, comprising: charging the battery pack using the device as described above.

[0069] Although some specific embodiments of the present disclosure have been shown in detail by examples, it should be understood by those skilled in the art that the above examples are intended to be illustrative only and do not limit the scope of the present disclosure. Some components in the aforementioned system are not necessarily arranged according to the diagram, and those skilled in the art can add some components or omit some components as needed. It should be understood by those skilled in the art that the above embodiments can be modified without departing from the scope and essence of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A device for charging a battery pack, comprising: a main power source, a negative electrode of the main power source being coupled to the negative electrode of the battery pack, the main power source being configured to provide a direct current; an inverter unit, wherein a positive electrode of an input terminal of the inverter unit is coupled to a positive electrode of the main power source, and a negative electrode of an input terminal of the inverter unit is coupled to a positive electrode of the battery pack, the inverter unit is configured to convert a direct current provided by the main power source into a high-frequency alternating current, and comprises a full-bridge circuit, and the full-bridge circuit controls the inverter unit to adjust a charging current of the battery pack by performing pulse width modulation on a conduction pulse of the inverter unit; A transformer unit, comprising a primary winding and a plurality of secondary windings, wherein the primary winding is coupled to an output end of the inverter unit; A plurality of rectifier units, wherein an input end of each rectifier unit in the plurality of rectifier units is coupled to a corresponding secondary winding of a transformer unit, an output end of each rectifier unit in the plurality of rectifier units is coupled to a corresponding battery in the battery pack, and each rectifier unit is configured to convert a high-frequency alternating current input from a corresponding secondary winding of the transformer unit into a direct current; a current measuring unit configured to measure a current passing through the primary winding; The device is further configured to: when the current passing through the primary winding is less than the current reference value, increase the width of the conduction pulse; And when the current passing through the primary winding is greater than or equal to a current reference value, the width of the conduction pulse is reduced, wherein the current reference value is set based on the maximum charging current of the battery pack.

2. The device according to claim 1, wherein: The current reference value is adjustable.

3. The device according to claim 1 or 2, further comprising a voltage measuring unit, wherein the voltage measuring unit is configured to measure the voltage across the battery pack, and the device is further configured to: When the difference between the voltage across the battery pack and the full voltage of the battery pack is less than the voltage difference reference value, the current reference value is reduced.

4. The device according to claim 1 or 2, further comprising a voltage measuring unit, wherein the voltage measuring unit is configured to measure the voltage across the battery in the battery pack, and the device is further configured to: When the voltage across both ends of any battery in the battery pack exceeds the maximum charging voltage, the current reference value is reduced.

5. The device according to claim 1, wherein: Each rectifying unit includes a synchronous rectifying circuit.

6. The device according to claim 1, wherein: Each battery in the battery pack is identical, and the number of turns of the plurality of secondary windings is identical.

7. The device of claim 1, wherein: The number of turns of the secondary winding is adjustable.

8. The device of claim 1, wherein: The output end of each of the plurality of rectifying units is coupled to a corresponding battery through an LC filtering circuit. 9 . The apparatus of claim 1 , further comprising a filter capacitor coupled between a positive electrode of the main power source and a negative electrode of the input terminal of the inverter unit.

10. A method for charging a battery pack, comprising: A battery pack is charged using the device according to any one of claims 1 to 9.

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