TWI405385B - Battery-charging equalization circuit, battery cell, and battery-charging equalization method - Google Patents

Abstract

A battery-charging equalization circuit including (2M+2) switch elements and M storage elements is provided. The battery-charging equalization circuit has a first node and a second node. The (2M+2) switch elements are coupled in series between the first node and the second node. Each of the M storage elements has a first end and a second end. A first end of the Nth storage element is coupled between the (2N-1)th switch element and the (2N)th switch element. A second end of the Nth storage element is coupled between the (2N+1)th switch element and the (2N+2)th switch element, wherein M and N are positive integers, and N ≤ M. Furthermore, a battery system and a battery-charging equalization method are also provided.

Description

Battery voltage equalizing circuit, battery system and battery equalizing method

The present invention relates to a battery grading circuit and method thereof, and more particularly to a non-dissipative battery grading circuit and method therefor.

With the rapid development of science and technology, various types of batteries have been widely used in daily life, such as electric steam locomotives, lighting equipment and uninterruptible power systems. Generally used batteries can be classified into general batteries and rechargeable batteries according to their properties.

Common general batteries include alkaline manganese batteries, zinc batteries, zinc-mercury batteries, and mercury batteries. When the battery is exhausted, it cannot be recharged, so that its electrochemical materials continue to store charge, so it is also called a disposable battery. Rechargeable batteries are also called secondary batteries. The types of rechargeable batteries can be divided into lead-acid batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-hydrogen batteries and lithium-ion batteries. The advantages are long cycle life and full Charge and discharge up to hundreds of times, and the charge capacity of some rechargeable batteries is higher than that of the primary battery. Among them, lithium ion batteries are popular and commonly used secondary batteries in the industry today. Lithium ion is the lightest element in metal, and has high activity and low density. Its standard electrode potential is -3.045V, which is also the most negative element in metal elements. Therefore, it is especially suitable for developing small and lightweight batteries. In addition, lithium-ion batteries have the advantages of high volume capacity density, low self-discharge rate, no memory effect and high operating voltage, and are also widely used for lithium ion batteries.

Since the commonly used battery voltage is only 2.6V-9V, in practical applications, the battery is often used in series to achieve a higher voltage level, so when the battery is recharged, the battery is charged in series. The battery's internal resistance varies with the time of use, temperature, and charge and discharge frequency. Therefore, the same battery string often differs in its internal resistance due to its different use. According to Kirchhoff's law, when the battery string passes the same charging current, the charging voltage across the battery is also different because of its different internal resistance. When the internal resistance of the battery is larger, the charging voltage across it will be larger; conversely, the smaller the internal resistance of the battery, the smaller the charging voltage will be. The influence of the internal resistance of the battery will cause some batteries in the tandem battery pack to be overcharged and often in a state of high discharge current. Under long-term use, the batteries of these overcharged or normally discharged states are easily damaged, thereby causing the whole battery. The serial module is not available.

The invention provides a battery voltage equalizing circuit, which can effectively balance the energy between the batteries on the battery string.

The invention provides a battery system in which the energy of each battery on the battery string can effectively reach an equilibrium state.

The invention provides a battery voltage equalization method, which can effectively balance the energy of each battery on the battery string.

The invention provides a battery voltage equalization circuit. The battery voltage equalization circuit has a first node and a second node, and includes (2M+2) switching elements and M energy storage elements. The (2M+2) switching elements are connected in series between the first node and the second node. In the M energy storage components, each energy storage component has a first end and a second end. The first end of the Nth energy storage component is coupled between the (2N-1)th switching element and the 2Nth switching element. The second end of the Nth energy storage component is coupled between the (2N+1)th switching element and the (2N+2)th switching element, where M and N are positive integers, and N≦M.

The present invention provides a battery system that is suitable for use in an electrical device. The battery system includes the above battery voltage equalizing circuit and a battery pack. The battery pack has a positive end and a negative end, and a plurality of rechargeable batteries are connected in series. Here, the first node and the second node of the battery voltage equalizing circuit are respectively coupled to the positive end and the negative end of the battery pack.

In an embodiment of the invention, the energy storage elements are each a capacitor.

In an embodiment of the invention, the capacitance of the capacitor is greater than 0.1 Farad.

In an embodiment of the invention, the battery pack includes (M+1) rechargeable batteries. The negative terminal of the Kth rechargeable battery is coupled to the source/drain of the 2Kth switching element. The positive terminal of the Kth rechargeable battery is coupled to the source/drain of the (2K-1)th switching element, where K is a positive integer and K≦M+1.

In an embodiment of the invention, the switching element is controlled by a control signal. When the control signal is at the first level, the (2K-1)th switching element is turned on, and the 2Kth switching element is turned off, so that the rechargeable battery charges the corresponding energy storage element.

In an embodiment of the invention, when the control signal is a second level, the (2K-1)th switching element is turned off, and the 2Kth switching element is turned on, so that the energy storage element pair is corresponding. Charging the battery to charge.

In an embodiment of the invention, the battery voltage equalizing circuit further includes (M+1) voltage stabilizing capacitors. The two ends of each voltage stabilizing capacitor are respectively coupled to the positive end and the negative end of the corresponding rechargeable battery.

The present invention further provides a battery voltage equalization method suitable for the above battery system. The battery voltage equalization method includes the following steps. The above battery system is provided. According to a control signal, the corresponding energy storage component is charged by the battery pack. The battery pack is charged by the energy storage component according to the control signal.

In an embodiment of the invention, in the step of charging the energy storage component, when the control signal is at a first level, the corresponding energy storage component is charged by the battery pack.

In an embodiment of the invention, in the step of charging the battery pack, when the control signal is at a second level, the battery pack is charged by the energy storage element.

Based on the above, in the embodiment of the present invention, the energy transfer control is performed with the super capacitor and the battery, so that the battery with higher energy can be transmitted to the battery with lower electric energy to achieve the goal of energy balance of each battery on the battery string.

The above described features and advantages of the present invention will be more apparent from the following description.

Generally, when the battery pack is charged, since only one set of chargers is used for charging, the single battery is not individually charged, but the difference in the chemical composition existing in the battery itself, the different charging acceptance, and the charging capacity are different. However, the voltage values of the individual batteries are different, causing the battery in the battery pack to have uneven power, so that the battery pack has reached the saturation voltage during the same charging time, but some of the batteries are still in the power. Insufficient state, resulting in reduced battery charging and discharging efficiency, will also shorten the battery life.

In view of this, in an exemplary embodiment of the present invention, an improved capacitive switching uniform charging architecture is proposed, which attempts to improve battery charging and discharging efficiency and prolong the service life of the battery pack, wherein uniform charging enables the battery pack to be charged in series. In the state, each battery can obtain proper charging energy, and can avoid overcharging and over-discharging.

In the exemplary embodiment below, a supercapacitor will be used as an exemplary embodiment of an energy storage component, and anyone skilled in the art will recognize that a supercapacitor is not intended to define an energy storage component of the present invention. In the meantime, the present invention is not limited to the capacitive switching uniform charging architecture of the exemplary embodiment below. Any charging architecture that uses capacitive switching is the scope of the present invention.

Supercapacitors, also known as electrochemical capacitors or electric double-layer capacitors, are commonly used in specifications of 4F/2.5V, 1.8F/5V, and 1F/5.5V. This is a high-energy transfer method when the battery is expected to release energy quickly when it is loaded. Provides a dynamic output capability for the energy system to meet transient peak power requirements. However, in some cases, the battery is not suitable for providing transient peak power so frequently. At this time, the super capacitor is the best choice because the super capacitor has high coulombic efficiency, light weight, miniaturization, low internal resistance, and ultra capacitance. It can be used in a very wide temperature range and has a long life.

1 is a circuit diagram of a battery system according to an embodiment of the present invention. Referring to FIG. 1 , the battery system 100 of the present embodiment includes a battery voltage equalizing circuit 110 and a battery pack 120 , wherein the battery pack 120 is composed of a plurality of rechargeable batteries B1 B B4 connected in series.

In this embodiment, the battery voltage equalizing circuit 110 has a first node a and a second node b, which are respectively coupled to the positive end of the rechargeable battery B1 (the positive end of the battery pack) and the negative end of the rechargeable battery B4. (negative end of the battery pack). Further, the battery grading circuit 110 includes (2M+2) switching elements and M energy storage elements, where M is a positive integer.

In the present embodiment, M=3 is taken as an example. Therefore, the battery voltage equalizing circuit 110 includes three energy storage elements C1 to C3 such as super capacitors, and eight switching elements M1 to M8. Here, the capacitance of the super capacitor is, for example, greater than 0.1 Farad, and the switching elements M1 to M8 are, for example, a function of realizing high frequency switching using a gold oxide half field effect transistor (MOSFET). In addition, as can be seen from FIG. 1, the switching elements M1 to M8 are connected in series between the first node a and the second node b.

In this embodiment, one end of the Nth energy storage element is coupled between the (2N-1)th switching element and the 2Nth switching element, and the other end of the Nth energy storage element is coupled to the Between 2N+1) switching elements and (2N+2) switching elements, where N is a positive integer and N≦M.

For example, one end of the first energy storage element C1 is coupled between the first switching element M1 and the second switching element M2, and the other end of the first energy storage element C1 is coupled to the third switch. Between the element M3 and the fourth switching element M4. In other words, when N=1 at this time and N=2, 3, the coupling relationship between the energy storage element and the switching element can be analogized by the above manner.

In the present embodiment, the battery pack 120 includes (M+1) rechargeable batteries. The negative terminal of the Kth rechargeable battery is coupled to the source/drain of the 2Kth switching element. The positive terminal of the Kth rechargeable battery is coupled to the source/drain of the (2K-1)th switching element, where K is a positive integer and K≦M+1.

For example, in the battery pack 120, the negative end of the first rechargeable battery B1 is coupled to the source/drain of the second switching element M2, and the positive end of the first rechargeable battery is coupled to the first switch. Source/drain of element M1. In other words, when K=1 at this time and K=2, 3, and 4, the coupling relationship between the rechargeable battery and the switching element can be analogized by the above manner.

In addition, in this embodiment, a voltage stabilizing capacitor of the same size as the energy storage component is connected in parallel with each of the rechargeable batteries to achieve the function of voltage stabilization and filtering of excess noise. Therefore, the battery grading circuit 110 of the embodiment further includes (M+1) capacitors. Here, taking M=3 as an example, the battery voltage equalizing circuit 110 further includes four voltage stabilizing capacitors C4 to C7. The two ends of each voltage stabilizing capacitor are respectively coupled to the positive end and the negative end of the corresponding rechargeable battery. For example, the two ends of the voltage stabilizing capacitor C4 are respectively coupled to the positive terminal and the negative terminal of the corresponding rechargeable battery B1.

Therefore, the number of energy storage elements, switching elements, and voltage stabilizing capacitors can be inferred from the number of rechargeable batteries in the battery pack 120. If there are (M+1) rechargeable batteries, the required energy storage elements are M, and the switching elements are ( 2M+2) and the voltage regulator capacitor is (M+1).

In addition, the battery system 100 of the present embodiment can be widely applied to various types of electrical devices in daily life, such as electric steam locomotives, lighting devices, and uninterruptible power systems, but the present invention is not limited thereto.

In this embodiment, the switching element is controlled by a control signal. When the control signal is at a first level, the (2K-1)th switching element is turned on, and the 2Kth switching element is turned off, so that the rechargeable batteries B1~B4 charge the corresponding energy storage elements. On the other hand, when the control signal is at a second level, the (2K-1)th switching element is turned off, and the 2Kth switching element is turned on, so that the energy storage element charges the corresponding rechargeable battery.

In detail, FIG. 2 is a schematic diagram of switching switching logic. Referring to FIG. 1 and FIG. 2, in the structure of the battery voltage equalizing circuit 110 of the embodiment, the switching operation of the switching element is, for example, a switching signal of one wave at a fixed frequency, by switching up and down. Turning on, and forming an energy transfer path between the two rechargeable batteries.

In this embodiment, the switching element is implemented by, for example, a gold-oxygen half-field transistor, and the control signal (not shown in FIG. 1) is, for example, a square wave applied to each gate of the transistor to control the conduction state of the switching element. .

In detail, when the control signal is positive half cycle, all the switching elements are turned on upward, that is, the energy storage elements C1 C C3 are connected to the positive end of the corresponding rechargeable battery via the switching elements M1, M3, M5, M7, and at this time, The state is defined as phase 1. Conversely, when the control signal is negative half cycle, all the switching elements are turned on, that is, the energy storage elements C1 C C3 are connected to the negative ends of the corresponding rechargeable batteries via the switching elements M2, M4, M6, M8. The state is defined as phase 2.

In addition, in order to avoid the occurrence of repeated conduction, which affects the operation of the battery voltage equalizing circuit 110, causing damage to the battery pack 120, this embodiment adds a dead time between phase 1 and phase 2. In other words, the switching of the switching elements M1 to M8 by the delay time does not result in repeated conduction. The complete switching period, including the delay time, can be defined as the period T. Wherein D ₁ and D ₂ are time multiplications of phase 1 and phase 2, respectively, and in the present embodiment, D ₁ = D ₂ .

Therefore, the advantages of the battery voltage equalization circuit of the embodiment include at least an additional voltage detection circuit, or an additional design of closed loop control to achieve the balance of the power.

Figure 3 and Figure 4 are schematic diagrams of circuit states and switching logic at different stages. Referring to FIG. 1 to FIG. 4, in combination with the above circuit operation, the operation flow of the battery voltage equalization circuit will be described in detail.

As shown in FIG. 3, in the period D ₁ T, all the switching elements are in the state of being switched upward. At this time, the rechargeable battery B1 starts charging the voltage stabilizing capacitor C4 and the energy storage element C1 through the charging path P1, so that the voltage is regulated. The power of the capacitor C4 and the energy storage component C1 is equal to the battery B1. Similarly, the operation of the rechargeable batteries B2, B3, B4 can be similarly. After a short delay time, the control sequence enters the next cycle D ₂ T.

As shown in FIG. 4, in the period D ₂ T, all the switching elements are in a state of being switched downward. At this time, since the energy of the energy storage element C1 is equal to the rechargeable battery B1, if the voltage of the rechargeable battery B2 is smaller than the rechargeable battery B1, Then, the energy storage device C1 starts charging the rechargeable battery B2 and the voltage stabilizing capacitor C5 through the charging path P2, so the power of the rechargeable battery B2 is equivalent to the battery B1. Similarly, the operation of the batteries B2, B3, and B4 can be similarly performed, and thus a switching period T is completed.

In other words, for the battery pack 120 in which four rechargeable batteries are connected in series, three switching periods T are required to complete uniform charging. In the present embodiment, the switching frequency used by the battery grading circuit 110 is 20 kHz (KHz), so the time required to complete the uniform charging is 0.15 milliseconds (ms).

In an exemplary embodiment of the battery grading circuit, in an exemplary embodiment of the present invention, a battery grading circuit is applied to four lithium batteries having a capacity of 600 milliampere-hours (mAh) and a voltage of 9 volts (votlage, V). Tandem equalization test. Based on safety considerations, the voltage value of the lithium battery is indicated as 9V, but when it is actually charged, its internal protection mechanism limits the voltage to 8.7V. If it exceeds 8.7V, the protection mechanism is activated and the voltage value is displayed as 9V, so the actual full voltage value is 8.7V.

In an exemplary embodiment of the invention, the charging method employed by the battery system is to charge at a constant current and then to charge at a fast and ultra-fast C-rate, respectively. Here, 0.5C is defined as fast charging, and 1C is defined as ultra-fast charging.

In addition, in order to test whether there is a correlation between the maximum voltage difference that the battery grading circuit can withstand and the charging rate, the series charging battery is uniformly charged with a different C-rate based on the voltage difference of 1V. In the battery voltage equalization circuit, the modular concept is adopted, and two batteries are uniformly charged for one module, and finally the modules are connected in series to the required DC link voltage value.

In the exemplary embodiment below, an example embodiment of the voltage equalization of the battery grading circuit at different charging speeds and the equalizing voltage when the pressure difference between the batteries is different will be exemplified.

Equalization pressure at different charging speeds

FIG. 5 and FIG. 6 respectively show test results of direct series charging of the battery packs A and B by fast charging and ultra-fast charging. 5(a) and 6(a) illustrate the battery voltage measured at a fixed time when performing uniform charging, and FIGS. 5(b) and 6(b) show the two batteries at a fixed time. The voltage difference.

Referring to FIG. 5 and FIG. 6, in the present embodiment, at the beginning of the test, it is assumed that the battery voltage changes are recorded every 15 minutes under the initial conditions of the same differential pressure of the battery. At 15 minutes, the voltage difference is reduced to 0.07V and 0.02V respectively during fast charging and ultra-fast charging tests, which means that the battery voltage equalization circuit is remarkable in both fast charging and ultra-fast charging. The pressure equalization effect. Similarly, up to 60 minutes, whether it is a fast charge or ultra-fast charge test, the battery voltage equalization circuit also maintains a good quality equalization effect.

Equalization pressure when the pressure difference between batteries is different

Figure 7 shows the results of the equalization with different pressure differentials during fast charging. Please refer to FIG. 7. FIG. 7(a) and FIG. 7(c) show the results of battery equalization test with initial pressure difference of 1V and 1.17V, respectively, and FIG. 7(b) and FIG. 7(d) are for each recording time. The voltage difference. As can be seen from Fig. 7(a), at 15 minutes, the effect of uniform charging occurred, and the pressure equalization effect continued to be very significant for 60 minutes. Similarly, when the voltage difference is increased to 1.17V, the goal of uniform battery voltage can still be achieved. It can be seen that the battery voltage equalizing circuit of the embodiment can effectively achieve the voltage equalization target.

FIG. 8 is a flow chart showing the steps of a method for equalizing a battery according to an embodiment of the present invention. Referring to FIG. 1 , FIG. 2 and FIG. 8 simultaneously, the battery voltage equalization method of the embodiment includes the following steps. First, in step S800, a battery system 100 such as that of FIG. 1 is provided. Next, in step S802, the corresponding energy storage component is charged by the battery pack 120 according to a control signal. Thereafter, in step S804, the battery pack is charged by the energy storage component according to the control signal.

In addition, the battery voltage equalization method of the embodiment of the present invention can obtain sufficient teaching, suggestion and implementation description from the description of the embodiment of FIG. 1 to FIG. 7, and therefore will not be described again.

In summary, in the battery system of the present invention, the battery voltage equalizing circuit transfers the energy of the battery with high power to the battery with low power by the switching element and the energy storage element, thereby achieving uniform charging. In addition, in the battery system of the present invention, the advantages of the circuit structure of the battery voltage equalization include at least control, no additional voltage detection circuit, and saving the circuit design cost in addition to the purpose of equalization.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100. . . Battery system

110. . . Battery voltage equalization circuit

120. . . Battery

BI~B4. . . Rechargeable Battery

C1~C3. . . Energy storage component

C4~C7. . . Voltage stabilizing capacitor

M1~M8. . . Switching element

T. . . Switching cycle

D ₁ , D ₂ . . . Time magnification

P1, P2. . . Charging path

A, B. . . Battery

S800, S802, S804. . . Steps for battery equalization method

1 is a circuit diagram of a battery system according to an embodiment of the present invention.

Figure 2 is a schematic diagram of switching switching logic.

Figure 3 and Figure 4 are schematic diagrams of circuit states and switching logic at different stages.

FIG. 5 and FIG. 6 respectively show test results of direct series charging of the battery packs A and B by fast charging and ultra-fast charging.

Figure 7 shows the results of the equalization with different pressure differentials during fast charging.

FIG. 8 is a flow chart showing the steps of a method for equalizing a battery according to an embodiment of the present invention.

100. . . Battery system

110. . . Battery voltage equalization circuit

120. . . Battery

B1~B4. . . Rechargeable Battery

C1~C3. . . Energy storage component

C4~C7. . . Voltage stabilizing capacitor

M1~M8. . . Switching element

Claims (20)

A battery grading circuit having a first node and a second node, the battery grading circuit comprising: (2M+2) switching elements, the switching elements being serially connected to the first node and the second Between the nodes; and M energy storage components, each energy storage component has a first end and a second end, wherein the first end of the Nth energy storage component is coupled to the (2N-1)th switch The second end of the element and the 2Nth switching element, and the second end of the Nth energy storage element are coupled between the (2N+1)th switching element and the (2N+2)th switching element, wherein M, N is a positive integer and N≦M. The battery voltage equalizing circuit of claim 1, wherein the energy storage elements are each a capacitor. The battery voltage equalization circuit of claim 2, wherein the capacitance values of the capacitors are greater than 0.1 farads. The battery voltage equalizing circuit of claim 1, wherein the first node and the second node are respectively connected to a positive end and a negative end of a battery pack, and the battery pack is connected in series by a plurality of rechargeable batteries. Composed of. The battery voltage equalizing circuit of claim 4, wherein the battery pack comprises (M+1) rechargeable batteries, and the negative end of the Kth rechargeable battery is coupled to the source/汲 of the 2Kth switching element. And the positive terminal of the Kth rechargeable battery is coupled to the source/drain of the (2K-I)th switching element, where K is a positive integer and K≦M+1. The battery voltage equalizing circuit according to claim 5, wherein the switching elements are controlled by a control signal, and when the control signal is a first level, the (2K-1)th switching element is turned on. And the 2Kth switching element is turned off, so that the rechargeable batteries charge the corresponding energy storage elements. The battery voltage equalizing circuit according to claim 6, wherein when the control signal is a second level, the (2K-1)th switching element is turned off, and the 2Kth switching element is turned on, The energy storage components are caused to charge the corresponding rechargeable batteries. The battery grading circuit of claim 5, further comprising (M+1) voltage stabilizing capacitors, wherein each of the two ends of the stabilizing capacitor is respectively coupled to a corresponding positive end of the rechargeable battery and Negative end. A battery system is suitable for use in an electrical device, the battery system comprising: a battery voltage equalizing circuit having a first node and a second node, the battery voltage equalizing circuit comprising: (2M+2) switches An element, the switching elements are connected in series between the first node and the second node; and M energy storage elements, each energy storage element having a first end and a second end, wherein the Nth energy storage The first end of the component is coupled between the (2N-1)th switching element and the 2Nth switching element, and the second end of the Nth energy storage component is coupled to the (2N+1)th switch Between the component and the (2N+2)th switching element, wherein M and N are positive integers, and N≦M; and a battery pack having a positive terminal and a negative terminal, and the battery pack is composed of a plurality of rechargeable batteries The first node and the second node of the battery voltage equalization circuit are respectively coupled to the positive end and the negative end of the battery pack. The battery system of claim 9, wherein the energy storage elements are each a capacitor. The battery system of claim 10, wherein the capacitance of the capacitors is greater than 0.1 Farads. The battery system of claim 9, wherein the battery pack comprises (M+1) rechargeable batteries, and a negative end of the Kth rechargeable battery is coupled to a source/drain of the 2Kth switching element, and The positive terminal of the Kth rechargeable battery is coupled to the source/drain of the (2K-1)th switching element, where K is a positive integer and K≦M+1. The battery system of claim 12, wherein the switching elements are controlled by a control signal, and when the control signal is at a first level, the (2K-1)th switching element is turned on, and the The 2K switching elements are turned off to enable the rechargeable batteries to charge the corresponding energy storage elements. The battery system of claim 13, wherein when the control signal is a second level, the (2K-1)th switching element is turned off, and the 2Kth switching element is turned on, so that the The energy storage component charges the corresponding rechargeable batteries. The battery system of claim 12, further comprising (M+1) voltage stabilizing capacitors, wherein two ends of each voltage stabilizing capacitor are respectively coupled to the corresponding positive and negative ends of the rechargeable battery. A battery voltage equalization method is suitable for a battery system, the battery voltage equalization method comprising: providing the battery system according to claim 9; according to a control signal, by the battery group, corresponding to the storage The energy component is charged; and the battery pack is charged by the energy storage components according to the control signal. The battery voltage equalization method according to claim 16, wherein in the step of charging the energy storage elements, when the control signal is at a first level, by the battery pack, the corresponding The energy storage components are charged. The battery voltage equalization method according to claim 16, wherein in the step of charging the battery pack, when the control signal is at a second level, the battery is Group charging. The battery voltage equalization method according to claim 16, wherein each of the energy storage elements is a capacitor. The method of equalizing a battery according to claim 19, wherein the capacitance of the capacitors is greater than 0.1 Farad.