Simple multi-section lithium battery series charging circuit

Abstract

A simple multi-section lithium battery series and parallel charging circuit, the existing series and parallel charging circuit uses mechanical switches such as relays, inserts and the like to complete the switching of series and parallel circuits, and there are problems of high circuit cost, large size and short service life. The new type includes a lithium battery pack, the lithium battery pack is a first battery, a second battery, a third battery and a fourth battery, a group A MOS tube, a group B MOS tube and a group C MOS tube; the negative electrode of the first battery is grounded, the positive electrode is connected with a boost driving module, the positive electrodes of the second battery, the third battery and the fourth battery are respectively connected with a step-down discharge module output through the group A MOS tube, the negative electrodes are respectively grounded through the group B MOS tube, the first battery, the second battery, the third battery and the fourth battery are sequentially connected in series through the group C MOS tube, wherein the positive electrode of the fourth battery is externally connected with the step-down discharge module as the total positive electrode of the series-connected battery pack, and the output voltage is the highest 16V step-down adjustable. The utility model is applied to the field of lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a simple multi-cell lithium battery series-connected and parallel-charged circuit. Background Technology

[0002] With the rapid development of electric vehicles, energy storage systems, and consumer electronics, lithium batteries have become the mainstream power solution due to their advantages such as high energy density, long cycle life, low self-discharge rate, and environmental friendliness. Many devices (such as power tools, energy storage inverters, and drones) require high voltage input to reduce current loss. However, the voltage of a single lithium battery cell is typically 3.6V-3.7V, which is insufficient to directly meet the voltage requirements of different electrical devices. While battery packs composed of multiple lithium batteries connected in series can provide higher voltages, series circuits suffer from problems such as overcharging of individual cells and voltage imbalance between batteries during charging.

[0003] Therefore, constructing multi-cell lithium battery packs through series and parallel connections has become a key technological approach, and the design of the series-discharge-parallel charging circuit directly determines the performance, safety, and lifespan of the battery pack. However, existing series-discharge-parallel charging circuits mostly use mechanical switches such as relays and plug-in switches to switch between series and parallel circuits, resulting in high circuit costs, large size, and short lifespan, making them difficult to achieve in terms of simplicity and portability. Utility Model Content

[0004] To address the problems of high cost, large size, and short lifespan associated with existing series-parallel charging circuits that primarily use mechanical switches such as relays and plug-in switches for switching between series and parallel circuits, this invention provides a simple series-parallel charging circuit for multiple lithium batteries.

[0005] The technical solution of this application is: A simple multi-cell lithium battery series-discharge circuit includes a lithium battery pack consisting of a first battery, a second battery, a third battery, and a fourth battery, and also includes a step-down charging module, a step-down discharging module, a group A of MOSFETs, a group B of MOSFETs, and a group C of MOSFETs. The negative terminal of the first battery is grounded, and the positive terminal is connected to the boost drive module. The positive terminals of the second, third, and fourth batteries are connected to the output of the buck discharge module through group A MOSFETs, and the negative terminals are grounded through group B MOSFETs. The first, second, third, and fourth batteries are connected in series through group C MOSFETs. The positive terminal of the fourth battery serves as the positive terminal of the series battery pack connected to the buck discharge module, and the output voltage is adjustable up to 16V.

[0006] Furthermore, it also includes a resistor R1 and a MOSFET Q10. The lithium battery pack drives the C group of MOSFETs through the resistor R1, and the gate of the C group of MOSFETs is grounded through the MOSFET Q10.

[0007] Furthermore, it also includes a boost drive module and resistor R2; the gates of parallel A group MOSFETs, B group MOSFETs and MOSFET Q10 are connected to the output of the boost drive module and pulled down to ground through resistor R2; The input terminals of the buck charging module and the boost driving module are connected to a 5V power supply, and the output voltage of the boost driving module reaches the gate threshold of the MOSFET.

[0008] Furthermore, the A group MOSFETs, the B group MOSFETs, the C group MOSFETs, and the MOSFET Q10 are N-channel enhancement-mode MOSFETs with a gate threshold voltage of 1.5V. The MOSFETs are turned on when the gate threshold voltage is greater than 1.5V, and the on-resistance is 43mΩ.

[0009] Furthermore, when the lithium battery pack is converted into a series circuit, resistor R1 feeds back the 3.7V positive terminal of the fourth battery to the C group MOSFET and turns it on, while the parallel MOSFET is turned off, thus forming a series circuit for the lithium battery pack.

[0010] Furthermore, when the lithium battery pack is a parallel circuit, the boost drive module provides a drive voltage to the series-connected A group MOSFETs, B group MOSFETs and Q10 and turns them on, while the series-connected MOSFETs are turned off, and the battery pack forms a parallel circuit.

[0011] Furthermore, the MOSFETs in group A are MOSFETs Q1, Q2, and Q3, and MOSFETs Q1, Q2, and Q3 are connected in series.

[0012] Furthermore, the MOSFETs in group B are MOSFETs Q4, Q5, and Q6, and MOSFETs Q4, Q5, and Q6 are connected in series.

[0013] Furthermore, the C group of MOSFETs consists of MOSFETs Q7, Q8, and Q9, which are connected in series.

[0014] Compared with the prior art, this application has the following advantages: The circuit structure proposed in this invention is suitable for multi-cell lithium battery series discharge and parallel charging systems. The circuit system is simple in design and offers excellent cost-effectiveness.

[0015] This utility model's multi-cell lithium battery series-parallel switching circuit uses 10 N-channel MOSFETs, has a simple circuit structure, and a small circuit board size.

[0016] The lithium battery pack proposed in this invention has a charging voltage greater than 4.2V, making it compatible with most chargers, such as 5V chargers.

[0017] The lithium battery pack of this invention uses parallel charging during charging, which is suitable for high-current fast charging. At the same time, voltage balancing between batteries is performed during charging, thereby improving battery life. Attached Figure Description

[0018] Appendix Figure 1 This is a schematic diagram of the four-cell lithium battery series-parallel charging circuit of this utility model; Appendix Figure 2 This is a schematic diagram of the series equivalent circuit; Appendix Figure 3 This is a schematic diagram of the parallel equivalent circuit.

[0019] In the diagram: 1. MOSFETs in group A, 2. MOSFETs in group B, 3. MOSFETs in group C. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate this application, but are not intended to limit the scope of this application. Specific Implementation Method 1 A simple multi-cell lithium battery series-discharge circuit includes a lithium battery pack consisting of a first battery, a second battery, a third battery, and a fourth battery. The circuit is characterized by further including a step-down charging module, a step-down discharging module, a group A MOSFET 1, a group B MOSFET 2, and a group C MOSFET 3. The negative terminal of the first battery is grounded, and the positive terminal is connected to the boost drive module. The positive terminals of the second, third, and fourth batteries are connected to the output of the buck discharge module through group A MOSFETs, and the negative terminals are grounded through group B MOSFETs. The first, second, third, and fourth batteries are connected in series through group C MOSFETs. The positive terminal of the fourth battery serves as the positive terminal of the series battery pack connected to the buck discharge module, and the output voltage is adjustable up to 16V. Specific Implementation Method Two: According to Embodiment 1, a simple multi-cell lithium battery series-discharge circuit further includes a resistor R1 and a MOSFET Q10. The lithium battery pack drives the C group of MOSFETs through the resistor R1, and the gate of the C group of MOSFETs is grounded through the MOSFET Q10. Specific implementation method three: According to Embodiment 1 or 2, a simple multi-cell lithium battery series-discharge circuit further includes a boost drive module and a resistor R2; the gates of parallel A group MOSFETs, B group MOSFETs and MOSFET Q10 are connected to the output of the boost drive module and pulled down to ground through resistor R2; The input terminals of the buck charging module and the boost driving module are connected to a 5V power supply, and the output voltage of the boost driving module reaches the gate threshold of the MOSFET. Specific implementation method four: According to Embodiment 1, 2, or 3, a simple multi-cell lithium battery series-discharge and parallel-charge circuit is provided. The A group MOSFET, the B group MOSFET, the C group MOSFET, and the MOSFET Q10 are N-channel enhancement-mode MOSFETs with a gate threshold voltage of 1.5V. The MOSFETs are turned on when the gate threshold voltage is greater than 1.5V, and the on-resistance is 43mΩ. Specific implementation method five: According to a simple multi-cell lithium battery series-connected and parallel-charged circuit described in Embodiment 1, 2, 3, or 4, when the lithium battery pack is converted into a series circuit, resistor R1 feeds back the positive terminal 3.7V of the fourth battery to the C group MOSFET and turns it on, while the parallel MOSFET is turned off, thus forming a series circuit for the lithium battery pack. Specific implementation method six: According to Embodiment 1, 2, 3, 4, or 5, a simple multi-cell lithium battery series-discharge and parallel charging circuit is provided. When the lithium battery pack is a parallel circuit, the boost drive module provides a drive voltage to the series-connected A group MOSFETs, B group MOSFETs, and Q10 and turns them on, while the series-connected MOSFETs are turned off, and the battery pack forms a parallel circuit. Specific implementation method seven: According to Embodiment 1, 2, 3, 4, 5, or 6, a simple multi-cell lithium battery series-discharge circuit is provided, wherein Group A consists of MOSFETs Q1, Q2, and Q3, and MOSFETs Q1, Q2, and Q3 are connected in series.

[0028] Group B consists of MOSFETs Q4, Q5, and Q6, with MOSFETs Q1, Q2, and Q3 connected in series.

[0029] Group C consists of MOSFETs Q7, Q8, and Q9, which are connected in series. Detailed implementation method eight: According to Embodiment 1, 2, 3, 4, 5, 6, or 7, a simple multi-cell lithium battery series-discharge circuit is described, and its specific working principle is as follows: Figure 1 This is a schematic diagram of the four-cell lithium battery series-discharge-parallel charging circuit of the present invention. As shown in the figure, the negative terminal of the first battery is grounded, and the positive terminal is connected to the output of the buck charging module. The positive terminals of the second, third, and fourth batteries are connected to the output of the buck charging module through MOSFETs Q1, Q2, and Q3, respectively, and the negative terminals are grounded through MOSFETs Q4, Q5, and Q6, respectively.

[0031] The first, second, third, and fourth batteries are connected in series via MOSFETs Q7, Q8, and Q9, respectively. The positive terminal of the fourth battery serves as the overall positive terminal of the series battery pack, which is connected to an external step-down discharge module. The overall positive terminal of the battery pack drives the three series MOSFETs Q7, Q8, and Q9 through a resistor R1. At the same time, the gates of the three series MOSFETs are grounded through MOSFET Q10.

[0032] MOSFETs Q1, Q2, Q3, Q4, Q5, and Q6 are connected in parallel. The gate of MOSFET Q10 is connected to the output of the boost driver module and pulled down to ground through resistor R2. The inputs of the buck charging module and the boost driver module are connected to a 5V power supply.

[0033] The specific series-parallel circuit switching process is as follows: When the battery pack switches from parallel to series connection, the 5V power supply is removed, the boost drive module and buck charging module stop outputting, and resistor R2 pulls down the gate potentials of MOSFETs Q1, Q2, Q3, Q4, Q5, Q6, and Q10. MOSFETs Q1, Q2, Q3, Q4, Q5, Q6, and Q10 are turned off, and the parallel circuit between the battery packs is shut down. Simultaneously, due to the turn-off of MOSFET Q10, the gate potentials of MOSFETs Q7, Q8, and Q9 are pulled up through current limiting by R1, turning the MOSFETs on. The battery pack is now in series connection. Figure 2 The series equivalent circuit shown here is used to ignore the MOSFET that is turned off.

[0034] When the battery pack switches from series connection to parallel connection, a 5V power supply is applied, and the boost drive module and buck charging module begin outputting. The boost drive module outputs a high-level signal to the gates of MOSFETs Q1, Q2, Q3, Q4, Q5, Q6, and Q10, turning them on. Because MOSFET Q10 is on, the gate potentials of MOSFETs Q7, Q8, and Q9 are pulled low, causing them to turn off. The series circuit between the battery packs is then disconnected, and the battery packs are connected in parallel. (Refer to...) Figure 3 The parallel equivalent circuit shown is used here, where the off MOSFETs are ignored. Simultaneously, voltage balancing is performed between the batteries, and the buck charging module begins charging the parallel battery pack.

[0035] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has disclosed the preferred embodiment as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the technical solution of this application, based on the technical essence of this application and within the spirit and principles of this application, shall still fall within the protection scope of the technical solution of this application.

Claims

1. A simple multi-cell lithium battery series-discharge circuit, comprising a lithium battery pack, wherein the lithium battery pack consists of a first battery, a second battery, a third battery, and a fourth battery, characterized in that, It also includes a buck charging module, a buck discharging module, a group A MOSFET, a group B MOSFET, and a group C MOSFET; The negative terminal of the first battery is grounded, and the positive terminal is connected to the boost drive module. The positive terminals of the second, third, and fourth batteries are connected to the output of the buck discharge module through group A MOSFETs, and the negative terminals are grounded through group B MOSFETs. The first, second, third, and fourth batteries are connected in series through group C MOSFETs. The positive terminal of the fourth battery serves as the positive terminal of the series battery pack connected to the buck discharge module, and the output voltage is adjustable up to 16V.

2. The simplified multi-cell lithium battery series-discharge circuit according to claim 1, characterized in that, It also includes a resistor R1 and a MOSFET Q10. The lithium battery pack drives the C group of MOSFETs through the resistor R1, and the gate of the C group of MOSFETs is grounded through the MOSFET Q10.

3. The simplified multi-cell lithium battery series-discharge-parallel charging circuit according to claim 1, characterized in that, It also includes a boost drive module and resistor R2; the gates of parallel A group MOSFETs, B group MOSFETs and MOSFET Q10 are connected to the output of the boost drive module and pulled down to ground through resistor R2; The input terminals of the buck charging module and the boost driving module are connected to a 5V power supply, and the output voltage of the boost driving module reaches the gate threshold of the MOSFET.

4. The simplified multi-cell lithium battery series-discharge circuit according to claim 3, characterized in that, The MOSFETs in group A, group B, group C, and MOSFET Q10 are N-channel enhancement-mode MOSFETs with a gate threshold voltage of 1.5V. The MOSFETs are turned on when the gate threshold voltage is greater than 1.5V, and the on-resistance is 43mΩ.

5. The simplified multi-cell lithium battery series-discharge circuit according to claim 1, characterized in that, When the lithium battery pack is converted into a series circuit, resistor R1 feeds back the 3.7V positive terminal of the fourth battery to the C group MOSFET and turns it on, while the parallel MOSFET is turned off, thus forming a series circuit for the lithium battery pack.

6. The simplified multi-cell lithium battery series-discharge circuit according to claim 1, characterized in that, When the lithium battery pack is a parallel circuit, the boost drive module provides a drive voltage to the series-connected A group MOSFETs, B group MOSFETs and Q10 and turns them on, while the series-connected MOSFETs are turned off, and the battery pack forms a parallel circuit.

7. The simplified multi-cell lithium battery series-discharge-parallel charging circuit according to claim 1, characterized in that, Group A consists of MOSFETs Q1, Q2, and Q3, which are connected in series.

8. The simplified multi-cell lithium battery series-discharge-parallel charging circuit according to claim 1, characterized in that, Group B consists of MOSFETs Q4, Q5, and Q6, with MOSFETs Q1, Q2, and Q3 connected in series.

9. The simplified multi-cell lithium battery series-discharge-parallel charging circuit according to claim 1, characterized in that, Group C consists of MOSFETs Q7, Q8, and Q9, which are connected in series.

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