An active balancing circuit and balancing method suitable for battery balancing

Abstract

The present invention provides an active balancing circuit and balancing method suitable for battery balancing, which relates to the technical field of active balancing circuits, including: a single cell connection network and an energy transfer network; the single cell connection network includes n+1 bidirectional switches, four MOSFETs Q3-Q6, and n single cells, where n is the number of batteries connected to the single cell connection network; the energy transfer network includes two MOSFETs Q1, Q2, two diodes D1, D2, and two transformers T1, T2; the winding ratio of transformer T1 is n:1, and the winding ratio of transformer T2 is 1:n. In a switching cycle, the circuit can simultaneously perform the following two operations through transformers T1 and T2: the battery pack transmits energy to the single cells with lower energy in the battery pack; the single cells with higher energy in the battery pack transmit energy to the entire battery pack. The above operations can increase the battery energy conversion speed, shorten the balancing time, and improve the energy conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of active balancing circuits, and in particular to an active balancing circuit and a balancing method suitable for battery balancing. Background Art

[0002] Compared with traditional lead-acid batteries, power batteries represented by lithium ions have the characteristics of high energy density, long cycle life, low self-discharge and environmental friendliness, and have been increasingly widely used. Common lithium-ion batteries include lithium iron phosphate batteries, ternary lithium batteries, lithium titanate batteries and lithium cobalt oxide batteries. However, the battery cells have small capacity and low load capacity, which cannot meet the actual engineering needs. To this end, people often connect battery cells into modules in a certain way to improve the voltage platform and storage energy of the battery system. However, due to inconsistent control of production processes and production environments during the production process of batteries, there may be differences in the consistency of battery performance, and this consistency difference will gradually accelerate during use. If it cannot be controlled in a timely and effective manner, it will seriously affect the battery life and safety performance. In order to alleviate the problem of battery inconsistency, people usually use balancing technology to optimize battery consistency. Common hardware topologies for active balancing include DC / DC converters, transformers, and external supercapacitors and inductors, which realize energy transfer between different battery cells. The specific form of transfer includes transferring the battery cells with higher energy in the battery pack to the battery cells with lower energy through the energy transmission device, and discharging the battery cells with higher energy, thereby reducing the energy inconsistency difference between the battery cells. Passive balancing uses dissipative electronic components to dissipate the excess energy in the battery cells in the form of heat generated by the electronic components, thereby achieving balancing between the battery cells.

[0003] The balancing circuit of passive balancing technology is called an energy-consuming passive balancing circuit because of its working principle. The passive balancing circuit has two obvious defects. One is that it will cause energy waste, and the other is that it is easy to cause untimely heat dissipation, causing the battery pack to work in a high-temperature and unsafe environment.

[0004] Active balancing technology solves the two defects of passive balancing technology. The excess energy of high-charge batteries is transferred to low-charge batteries through capacitors, inductors or transformers in the active balancing circuit. The redistribution of energy cleverly solves the problem of unbalanced charge. Based on the research of classic inductor circuits, the present invention proposes an active balancing circuit with dual energy carriers. Summary of the invention

[0005] To solve the above problems, the present invention aims to provide an active balancing circuit and balancing method suitable for battery balancing. The circuit can improve the balancing speed and the energy utilization rate.

[0006] To achieve the above object, the present invention provides the following technical solutions.

[0007] An active balancing circuit suitable for battery balancing includes a single cell connection network and an energy transfer network;

[0008] The single-cell battery connection network includes n+1 bidirectional switches, four MOSFETs Q3_Q6 and n single-cell batteries, where n is the number of batteries connected to the single-cell connection network; the n single-cell batteries are connected in series to form a battery pack, the positive electrode of each single-cell battery is connected to one end of a bidirectional switch, and the other end of the bidirectional switch is connected to one end of MOSFET Q5 and MOSFET Q3 respectively; the negative electrode of each single-cell battery is connected to one end of a bidirectional switch, and the other end of the bidirectional switch is connected to one end of MOSFET Q4 and MOSFET Q6 respectively;

[0009] The energy transfer network includes MOSFET Q1, MOSFET Q2, transformer T1 and transformer T2; the winding ratio of the transformer T1 is n:1, and the winding ratio of the transformer T2 is 1:n; one end of the high-voltage side coil of the transformer T1 is connected to the positive electrode of the battery pack, and the other end is connected to the negative electrode of the battery pack through the MOSFET Q1; one end of the low-voltage side coil of the transformer T1 is connected to the other ends of the MOSFET Q5 and MOSFET Q6; the other end of the low-voltage side coil of the transformer T1 is connected to the MOSFET Q3 and MOSFET Q4 respectively;

[0010] One end of the high-voltage side coil of the transformer T2 is connected to the positive electrode of the battery pack, and the other end of the high-voltage side coil of the transformer T2 is connected to the negative electrode of the battery pack; one end of the low-voltage side coil of the transformer T2 is connected to the other end of the MOSFET Q5 and the MOSFET Q6 respectively, and the other end of the low-voltage side coil of the transformer T2 is connected to the MOSFET Q3 and the MOSFET Q4 respectively through the MOSFETQ2.

[0011] Preferably, it also includes a diode D1 and a diode D2; one end of the low-voltage side coil of the transformer T1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is connected to the other end of the MOSFET Q5 and the MOSFET Q6 respectively; one end of the high-voltage side coil of the transformer T2 is connected to the positive electrode of the diode D2, and the negative electrode of the diode D2 is connected to the positive electrode of the battery pack.

[0012] A balancing method for an active balancing circuit suitable for battery balancing comprises the following steps:

[0013] S1: a cycle TS It is divided into two stages, namely t0-t1 and t1-t2;

[0014] S2: At t=t0, turn on MOSFET Q1, MOSFET Q2, S BM and S BM+1 , transfer energy from battery pack B p Transfer to magnetic inductor L m1 , from single cell B M Transfer to magnetic inductor L m2 ; Single cell B M For a single cell with high energy, S BM and S BM+1 For single cell B M and B M+1 Adjacent switch, L m1 and L m2 They are the magnetic inductances of transformer T1 and transformer T2 respectively;

[0015] When B M For even-numbered cells, turn on MOSFET Q3 and MOSFET Q6. M For odd-numbered cells, MOSFET Q4 and MOSFET Q5 are turned on. At this stage, the magnetic inductor L m1 and magnetic inductance L m2 The current i Lm1 and i Lm2 Linear increase:

[0016]

[0017]

[0018] where i Lm1 ,i Lm2 Represents the current through the transformer, V BP Represents the entire battery pack B p Voltage, V BM Represents a single cell with high energy B M Voltage;

[0019] At this time, battery pack B P Charging single battery, high energy single battery B M For battery pack B P Charge;

[0020] S3: At t = t1, turn off MOSFET Q1, MOSFET Q2, S BM and S BM+1 , open S BN , S BN+1, diode D1 and diode D2, at this time the energy is transferred from the magnetic inductor L m1 and magnetic inductance L m2 Transfer to single cell B N and battery pack B p ; Single cell B N For a single cell with low energy, S BN and S BN+1 For single cell B N and B N+1 Adjacent switches;

[0021] When B N For even-numbered cells, turn on MOSFET Q3 and MOSFET Q6. N For odd-numbered cells, turn on MOSFET Q4 and MOSFET Q5. At this stage, the current through diode D1 and diode D2 is:

[0022]

[0023]

[0024] Among them, V BN Represents a single cell with low energy B N At this time, battery pack B p Charging single battery, high energy single battery B M For battery pack B p Charge.

[0025] Beneficial effects of the present invention:

[0026] The present invention proposes an active balancing circuit and balancing method suitable for battery balancing. In one switching cycle, the circuit can simultaneously perform the following two operations through transformers T1 and T2: 1. The battery pack transmits energy to the single battery with lower energy in the battery pack, and 2. The single battery with higher energy in the battery pack transmits energy to the entire battery pack. The above operations can increase the battery energy conversion speed, shorten the balancing time, and improve the energy conversion efficiency.

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is an overall balancing circuit diagram of an active balancing circuit applicable to battery balancing according to an embodiment of the present invention;

[0029] Figure 2 It is a circuit diagram of the charging state of a single battery of a battery pack during a t0-t1 period of an active balancing circuit applicable to battery balancing according to an embodiment of the present invention;

[0030] Figure 3 It is a circuit diagram of the charging state of a battery pack of a high-energy single cell in a t0-t1 active balancing circuit suitable for battery balancing according to an embodiment of the present invention;

[0031] Figure 4 The active balancing circuit for battery balancing according to the embodiment of the present invention is Figure 2 and 3 At the same time, the circuit diagram is carried out;

[0032] Figure 5 It is a circuit diagram of the charging state of a single battery of a battery pack t1-t2 of an active balancing circuit suitable for battery balancing according to an embodiment of the present invention;

[0033] Figure 6 It is a circuit diagram of the charging state of a battery pack of a high-energy single cell of an active equalization circuit suitable for battery equalization according to an embodiment of the present invention;

[0034] Figure 7 The active balancing circuit for battery balancing according to the embodiment of the present invention is Figure 5 and 6 Also make the circuit diagram. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] Example

[0037] An active balancing circuit suitable for battery balancing includes a single cell connection network and an energy transfer network. The overall balancing circuit diagram is as follows: Figure 1 As shown;

[0038] The single-cell battery connection network includes n+1 bidirectional switches, four MOSFETs Q3-Q6 and n single-cell batteries, where n is the number of batteries connected to the single-cell connection network; the n single-cell batteries are connected in series to form a battery pack, the positive electrode of each single-cell battery is connected to one end of a bidirectional switch, and the other end of the bidirectional switch is connected to one end of MOSFET Q5 and MOSFET Q3 respectively; the negative electrode of each single-cell battery is connected to one end of a bidirectional switch, and the other end of the bidirectional switch is connected to one end of MOSFET Q4 and MOSFET Q6 respectively;

[0039] The energy transfer network includes two MOSFETs Q1 and Q2, two diodes D1 and D2, and two transformers T1 and T2; the winding ratio of transformer T1 is n:1, and the winding ratio of transformer T2 is 1:n; one end of the high-voltage side coil of transformer T1 is connected to the positive electrode of the battery pack, and the other end is connected to the negative electrode of the battery pack through MOSFET Q1; one end of the low-voltage side coil of transformer T1 is connected to the positive electrode of diode D1, and the negative electrode of diode D1 is respectively connected to the other ends of MOSFET Q5 and MOSFET Q6; the other end of the low-voltage side coil of transformer T1 is respectively connected to MOSFET Q3 and MOSFET Q4;

[0040] One end of the high-voltage side coil of the transformer T2 is connected to the positive electrode of the diode D2, the negative electrode of the diode D2 is connected to the positive electrode of the battery pack, and the other end of the high-voltage side coil of the transformer T2 is connected to the negative electrode of the battery pack; one end of the low-voltage side coil of the transformer T2 is respectively connected to the other ends of MOSFETQ5 and MOSFETQ6, and the other end of the low-voltage side coil of the transformer T2 is respectively connected to MOSFETQ3 and MOSFETQ4 through MOSFETQ2.

[0041] In this embodiment, a switching period T is set S , the circuit performs the following two operations simultaneously through transformers T1 and T2:

[0042] 1. The battery pack transfers energy to the lower energy cells in the battery pack;

[0043] 2. The single cells with higher energy in the battery pack transfer energy to the entire battery pack.

[0044] A switching cycle T S It is divided into two stages: t0-t1 and t1-t2. The whole battery pack is B P Indicates that the single battery with lower energy in the battery pack uses B N Indicates that the single battery with higher energy in the battery pack uses B M Indicates. BM , S BM+i Representative and B M and B M+i Adjacent switch, S BN , S BN+1 Representative and B N and B N+1 Adjacent switch. L m1 and Representative L m2 Magnetic inductance of transformer T1 and transformer T2.

[0045] Phase 1 (t0-t1): At t=t0, turn on MOSFET Q1, MOSFET Q2, S BMand S BM+1 , at this time, the energy is taken from battery group B P Transfer to magnetic inductor L m1 , from single cell B M Transfer to magnetic inductor L m2 Magnetic inductance L m1 , magnetic inductance L m2 At the same time, from battery pack B P and single cell B M Collect energy when B M For even-numbered cells, turn on MOSFET Q3 and MOSFET Q6. When B M For odd-numbered cells, MOSFET Q4 and MOSFET Q5 are turned on. At this stage, L m1 and L m2 The current i Lm1 and i Lm2 Linear increase:

[0046]

[0047]

[0048] where i Lm1 ,i Lm2 Represents the current through the transformer, V BP Represents the voltage of the entire battery pack, V BM Represents the voltage of the battery with higher energy, L m1 and Representative L m2 Magnetic inductance of transformer T1 and transformer T2.

[0049] At this time, the battery pack passes current i Lm1 To charge a single cell, a high energy single cell passes a current i Lm2 Charge the battery pack; the effective circuit diagram is as follows Figure 2-4 shown.

[0050] Phase 2 (t1-t2): At t=t1, turn off MOSFET Q1, MOSFET Q2, S BM and S BM+1 , open S BN , S BN+1 , diode D1, diode D2, at this time the energy from L m1 and L m2 Transfer to single cell B N and battery pack B P , when B N For even-numbered cells, turn on MOSFET Q3 and MOSFET Q6. NFor odd-numbered cells, turn on MOSFET Q4 and MOSFET Q5. At this stage, the current through diode D1 and diode D2 is:

[0051]

[0052]

[0053] Where V BN Represents the voltage of the battery with lower energy. At this time, the battery pack passes the current i D1 To charge a single cell, a high energy single cell passes a current i D2 Charge the battery pack. The effective circuit diagram is as follows Figure 5-7 shown.

[0054] Table 1 Statistics of the opening states of each bidirectional switch and MOSFET during energy transmission in each period

[0055]

[0056] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An active balancing circuit suitable for battery balancing, characterized in that: Including single cell battery connection network and energy transfer network; The single cell connection network includes n+1 bidirectional switches, four MOSFETs Q3-Q6 and n single cells B1-B n , n is the number of batteries connected to the monomer connection network; n monomer batteries are connected in series to form a battery pack; the monomer battery B n The positive electrode of the single battery B1 is connected to one end of a bidirectional switch, and the other end of the bidirectional switch is connected to one end of MOSFETQ5 and MOSFETQ3 respectively; the negative electrode of the single battery B1 is connected to one end of another bidirectional switch, and the other end of the bidirectional switch is connected to one end of MOSFETQ4 and MOSFETQ6 respectively; the negative electrode of each single battery is connected to a bidirectional switch, and the bidirectional switch is alternately connected to one end of MOSFETQ4 and MOSFETQ6, or MOSFETQ5 and MOSFETQ3 respectively; The energy transfer network includes MOSFETQ1, MOSFETQ2, transformer T1 and transformer T2; the winding ratio of the transformer T1 is n:1, and the winding ratio of the transformer T2 is 1:n; one end of the high-voltage side coil of the transformer T1 is connected to the positive electrode of the battery pack, and the other end is connected to the negative electrode of the battery pack through the MOSFETQ1; one end of the low-voltage side coil of the transformer T1 is connected to the other end of the MOSFETQ5 and the MOSFETQ6; the other end of the low-voltage side coil of the transformer T1 is respectively connected to the other end of the MOSFETQ3 and the MOSFETQ4; One end of the high-voltage side coil of the transformer T2 is connected to the positive electrode of the battery pack, and the other end of the high-voltage side coil of the transformer T2 is connected to the negative electrode of the battery pack; one end of the low-voltage side coil of the transformer T2 is connected to the other ends of the MOSFETQ5 and MOSFETQ6 respectively, and the other end of the low-voltage side coil of the transformer T2 is connected to the other ends of the MOSFETQ3 and MOSFETQ4 respectively through the MOSFETQ2; The balancing method of the active balancing circuit applicable to battery balancing comprises the following steps: S1: a cycle T s It is divided into two stages, namely t0-t1 and t1-t2; S2: At t=t0, turn on MOSFETQ1, MOSFETQ2, S BM and S BM+1 , transfer energy from battery pack B P Transfer to magnetic inductor L m1 , from single cell B M Transfer to magnetic inductor L m2 ; Single cell B M For a single cell with high energy, S BM and S BM+1 For single cell B M The switch connected at both ends of the positive and negative poles, L m1 and L m2 They are the magnetic inductances of transformer T1 and transformer T2 respectively; When B M For even-numbered cells, turn on MOSFET Q3 and MOSFET Q6. M For odd-numbered cells, MOSFET Q4 and MOSFET Q5 are turned on. At this stage, the magnetic inductor L m1 and magnetic inductance L m2 The current i Lm1 and i Lm2 Linear increase: where i Lm1 ,i Lm2 Represents the current through the transformer, V BP Represents the entire battery pack B P Voltage, V BM Represents a single cell with high energy B M Voltage; At this time, battery pack B P Charging single battery, high energy single battery B M For battery pack B P Charge; S3: At t=t1, turn off MOSFETQ1, MOSFETQ2, S BM and S BM+1 , open S BN , S BN+1 , diode D1 and diode D2, at this time the energy is transferred from the magnetic inductor L m1 and magnetic inductance L m2 Transfer to single cell B N and battery pack B P ; Single cell B N For a single cell with low energy, S BN and S BN+1 For single cell B N A switch connected at both ends of the positive and negative poles; When B N For even-numbered cells, turn on MOSFET Q3 and MOSFET Q6. N For odd-numbered cells, turn on MOSFET Q4 and MOSFET Q5. At this stage, the current through diode D1 and diode D2 is: Among them, V BN Represents a single cell B with low energy N At this time, battery pack B P Charging single battery, high energy single battery B M For battery pack B P Charge.

2. The active balancing circuit for battery balancing according to claim 1, characterized in that: It also includes a diode D1 and a diode D2; one end of the low-voltage side coil of the transformer T1 is connected to the positive electrode of the diode D1, and the negative electrode of the diode D1 is connected to the other end of the MOSFET Q5 and the MOSFET Q6 respectively; one end of the high-voltage side coil of the transformer T2 is connected to the positive electrode of the diode D2, and the negative electrode of the diode D2 is connected to the positive electrode of the battery pack.

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