CN107453452A - A kind of more battery core serial lithium batteries based on load switch - Google Patents

Abstract

The invention provides a kind of more battery core serial lithium batteries based on load switch, applied to battery powered field, including：The series connection lithium cell and multiple load switches of multi-section serial, the accumulator being connected with load switch, voltage detector and controller.Technical scheme can realize the transfer of electricity when detecting that each battery core electricity is unbalanced by automatically controlling load switch.

Description

A multi-cell series lithium battery based on load switch

technical field

The invention relates to the field of lithium batteries, in particular to a multi-cell series lithium battery based on a load switch.

Background technique

Lithium battery is a type of battery that uses lithium metal or lithium alloy as the negative electrode material and uses a non-aqueous electrolyte solution. Due to the characteristics of high energy storage density, long service life and high rated voltage, lithium batteries are widely used in the fields of electronic products and new energy vehicles.

Existing lithium batteries usually use multiple lithium cells in series to form a whole lithium battery. The cells of each lithium battery can be regarded as an equivalent circuit in which the internal resistance and capacitance of the battery are connected in series, and the capacitance can be regarded as the capacity of the cell. For the overall charging operation of a multi-cell lithium battery, because the internal resistance and battery capacity of each cell are different, under the same charging cut-off voltage, some cells must be fully charged first, usually the negative part of the battery. It is the first to be fully charged, and some of the cells are not fully charged, resulting in incomplete charging of the lithium battery, which greatly reduces the efficiency of the lithium battery; however, if the charging continues, some of the fully charged cells will be overcharged, affecting the life of the cells. Therefore, it is necessary to improve the existing lithium battery structure.

Contents of the invention

In view of the above-mentioned problems existing in the field of lithium batteries in the prior art, a load switch-based multi-cell lithium battery in series is now provided.

The specific technical scheme is as follows:

A multi-cell series lithium battery based on a load switch is applied in the field of battery power supply, and the multi-cell series lithium battery includes:

A plurality of series-connected lithium batteries, the series-connected lithium batteries are sequentially connected in series to form a series-connected lithium battery pack, the positive pole of each of the series-connected lithium batteries is respectively connected to the first end of a first switch, and the negative pole of each of the series-connected lithium batteries respectively connected to the first end of a second switch;

The negative lithium battery cell is connected in series with the series lithium battery cell group, and the positive electrode of the negative electrode lithium battery cell is connected to the negative electrode of the series lithium battery cell group, and the positive electrode of the negative electrode lithium battery cell is also connected to the first end of a third switch, so The negative electrode of the negative electrode lithium battery cell is connected to the source electrode of a first N-type field effect transistor;

An energy storage, the positive pole of the energy storage is connected to the second end of each of the first switches and the second end of the third switch, and the negative pole of the energy storage is connected to each of the second the second end of the switch and the drain of the first N-type field effect transistor;

A voltage detector, respectively connected to the positive and negative poles of each of the series-connected lithium cells and the negative lithium cells, for detecting the real-time voltage of each of the series-connected lithium cells and the negative lithium cells;

a controller, respectively connected to the voltage detector, the control terminal of the first switch, the control terminal of the second switch, the control terminal of the third switch, and the gate of the first N-type field effect transistor , for controlling the first switch, the second switch, the third switch, and the second An on-off combination of an N-type field effect transistor transfers the electricity of the negative lithium battery cell to the corresponding lithium battery cell in series through the energy storage device.

Preferably, the controller is a programmable logic controller, which includes:

The comparison unit is connected to the voltage detector, and a balanced voltage difference is preset for the real-time voltage of any one of the series-connected lithium batteries to be lower than the real-time voltage of the negative lithium battery and the difference is greater than the balanced voltage. When there is a voltage difference, send a control command to the control unit;

The control unit is connected to the comparison unit, and a charging and discharging time is preset, and the control unit is used to control the conduction of the first N-type field effect transistor after receiving the control instruction, and control the second Three switches conduct and limit current;

After the charging and discharging time has elapsed, turning off the first N-type field effect transistor and the third switch;

Afterwards, controlling the conduction of the first switch of the corresponding series-connected lithium battery cell, controlling the conduction and current limiting of the second switch of the corresponding series-connected lithium battery cell;

After the charging and discharging time elapses, the first switch and the second switch are turned off.

Preferably, the voltage detector is an analog-to-digital conversion detection device for converting the detected real-time voltage into a digital signal.

Preferably, the energy storage device is a capacitor or a lithium battery.

Preferably, the first switch, the second switch and the third switch are all load switches, and the load switches include:

Two second N-type field effect transistors connected in series, connected in series between the first terminal and the second terminal of the load switch, for controlling the conduction state of the load switch;

A charge pump, the output end of the charge pump is connected to the gate of the second N-type field effect transistor, and is used to output a control voltage to the gate of the second N-type field effect transistor to control the second N-type field effect transistor. The on-off state and current-limiting state of the FET;

A current-limiting controller is connected to the charge pump and the controller respectively, and is configured to control the control voltage output by the charge pump according to instructions of the controller.

Preferably, the load switch further includes a voltage selector connected to the first terminal and the second terminal of the load switch respectively, and is used to select the high level of the first terminal and the second terminal of the load switch. The load switch supplies power.

Preferably, the load switch further includes a low-drop voltage source connected to the voltage high selector for generating the operating voltage of the load switch from the high level.

Preferably, the load switch further includes an overvoltage protection unit and an undervoltage protection unit, which are respectively connected to the charge pump, and are used to control the load switch not to turn on when the operating voltage of the load switch is too high or too low. Pass.

Preferably, each of the second N-type field effect transistors is provided with a parasitic diode, and the first end and the second end of the load switch are both connected to a drain of the second N-type field effect transistor.

The above technical solution has the following advantages or beneficial effects:

By setting a load switch on each lithium battery cell to connect the energy storage device, the controller can control the load switch to transfer the power of the lithium battery to the battery cell with less charge through the energy storage device, thereby realizing The active balance of lithium battery power maximizes the storage capacity of lithium batteries and improves the efficiency of use.

Description of drawings

Embodiments of the present invention are more fully described with reference to the accompanying drawings. However, the accompanying drawings are for illustration and illustration only, and do not limit the scope of the present invention.

FIG. 1 is a schematic diagram of the overall structure of an embodiment of a multi-cell series lithium battery based on a load switch in the present invention;

2 is a schematic structural diagram of a load switch in an embodiment of a load switch-based multi-cell lithium battery in series according to the present invention;

FIG. 3 is a schematic structural diagram of a controller in an embodiment of a load switch-based multi-cell lithium battery in series according to the present invention.

detailed description

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but not as a limitation of the present invention.

In a preferred embodiment of the present invention, as shown in Figure 1, a load switch-based multi-cell series lithium battery is applied to the field of battery power supply, including:

A plurality of series-connected lithium batteries A1, the series-connected lithium batteries A1 are sequentially connected in series to form a series-connected lithium battery pack, the positive pole of each series-connected lithium battery is respectively connected to the first end of a first switch, and the negative pole of each series-connected lithium battery is respectively connected to a first the first end of the second switch;

Negative lithium battery A0 is connected in series with the series lithium battery pack, and the positive pole of the negative lithium battery A0 is connected to the negative pole of the series lithium battery pack, the positive pole of the negative lithium battery A0 is also connected to the first end of a third switch, and the negative pole of the negative lithium battery A0 Connect the source of a first N-type field effect transistor N1;

The energy storage C1, the positive pole of the energy storage C1 is respectively connected to the second end of each first switch and the second end of the third switch, and the negative pole of the energy storage C1 is respectively connected to the second end of each second switch and the second end of the third switch. A drain of an N-type field effect transistor N1;

A voltage detector (not shown in the figure) is connected to the positive and negative poles of each series-connected lithium battery cell A1 and the negative electrode lithium battery cell A0, respectively, for detecting the real-time voltage of each series-connected lithium battery cell A1 and the negative electrode lithium battery cell A0;

The controller B1 is respectively connected to the voltage detector, the control terminal of the first switch, the control terminal of the second switch, the control terminal of the third switch, and the grid of the first N-type field effect transistor N1, and is used to control the voltage at any time according to the real-time voltage. When the voltage of a series-connected lithium battery A1 is lower than the voltage of the negative lithium battery A0, by controlling the combination of the first switch, the second switch, the third switch and the on-off of the first N-type field effect transistor N1, the power of the negative lithium battery A0 It is transferred to the corresponding series-connected lithium battery cell A1 through the energy storage C1.

Specifically, in this embodiment, for a lithium battery with multiple lithium cells connected in series, the first switch and the second switch are used to control the connection between each lithium cell and the energy storage device C1; the energy storage device C1 is used to connect the negative lithium cell A0 After the electric energy is temporarily stored, it is transferred to the series lithium cell A1 with less electric energy; the voltage detector is used to detect the voltage of each lithium cell and sent to the controller B1 as the basis for power balance; the controller B1 is used to realize According to the voltage of each lithium battery cell, the first switch, the second switch and the first N-type field effect transistor N1 are controlled to conduct, and the energy storage C1 is charged, and then the first switch and the first switch of the corresponding lithium battery cell A1 connected in series with less power are controlled. The second switch is turned on to transmit the electric energy of the energy storage C1 to the corresponding lithium battery cell A1 in series. By balancing the power of the negative lithium battery cell to each series connected lithium battery cell A1, the active balance of the lithium battery power is realized, and the power storage capacity of the lithium battery is maximized.

As shown in Figure 1, for a lithium battery with four lithium cells connected in series, the lithium cells connected in series are A11, A12, and A13 respectively, and the load switch connected to the positive pole of the lithium cell A1 is a load switch S7, load switch S6, load switch S4, load switch S2, the load switches connected to the negative pole of the series lithium cell A1 are load switch S1, load switch S3, load switch S5. The voltage detector detects the voltage of the positive and negative poles of each lithium battery cell respectively. Since each lithium battery cell is connected in series, the detected V0 is the negative electrode voltage of the negative electrode lithium battery cell A0, and V1 is the positive electrode voltage of the negative electrode lithium battery cell A0, which is also the series connected lithium battery cell A13. V2 is the positive voltage of the series lithium battery A13 and the negative voltage of the series lithium battery A12, V3 is the positive voltage of the series lithium battery A12 and the negative voltage of the series lithium battery A11, V4 is the positive voltage of the series lithium battery A11, Therefore, the voltage of each lithium cell is the voltage difference corresponding to the positive and negative electrodes. Wherein, the first switches are respectively: a load switch 7 , a load switch 6 , and a load switch 4 . The second switches are respectively: load switch 5 , load switch 3 , and load switch 1 . The third switch is a load switch S2.

In a preferred embodiment of the present invention, as shown in FIG. 3, the controller B1 is a programmable logic controller B1, and the controller B1 includes:

The comparison unit B11 is connected to a voltage detector, and a balanced voltage difference is preset, which is used to send a signal to the control unit B12 when the real-time voltage of any series lithium battery A1 is lower than the real-time voltage of the negative lithium battery A0 and the difference is greater than the balanced voltage difference. Regulatory instructions;

The control unit B12 is connected to the comparison unit B11 and has a preset charging and discharging time. The control unit B12 is used to control the conduction of the first N-type field effect transistor N1 and control the conduction and current limiting of the third switch after receiving the control command;

After the charging and discharging time has passed, turn off the first N-type field effect transistor N1 and the third switch;

After that, control the conduction of the first switch of the corresponding series lithium battery A1, control the conduction of the second switch of the corresponding series lithium battery A1 and limit the current;

After the charge and discharge time elapses, the first switch and the second switch are turned off.

Specifically, in this embodiment, the comparison unit B11 is used to compare each series-connected lithium battery cell A1 with the negative electrode lithium battery cell A0, and the target series-connected lithium battery cell A1 whose voltage is lower than the voltage of the negative electrode lithium battery cell A0 and whose difference is greater than the equilibrium voltage difference is obtained, The control unit B12 is used to control the conduction of the first N-type field effect transistor N1 connected to the negative lithium battery A0 and the third switch, and control the third switch to limit the current to ensure the stability of power transmission and realize energy storage to the energy storage C1 , and stop the energy storage after the charge and discharge time, and at the same time control the conduction of the corresponding first switch and the second switch of the target series lithium cell A1 with a lower voltage obtained by the comparison unit B2, and receive the electric energy of the energy storage device C1, By limiting the current of the second switch of the target series lithium cell A1, the stability of electric energy transmission is ensured. The above process is a single electric energy equalization process. In actual application, multiple electric energy equalization operations can be performed, so as to keep the electric power of each lithium cell in the lithium battery consistent.

In a preferred embodiment of the present invention, the voltage detector is an analog-to-digital conversion detection device for converting the detected real-time voltage into a digital signal.

Specifically, in this embodiment, the analog-to-digital conversion detection device is used, and the voltage can be sent to the controller B1 in the form of a digital signal while detecting the voltage. At the same time, the controller B1 is a programmable logic controller B1, which can only Logical judgment is made on the digital signal, therefore, it is convenient for the controller B1 to compare the voltage of each lithium battery cell to determine whether it is sufficient for voltage equalization operation.

In a preferred embodiment of the present invention, as shown in FIG. 1 , the energy storage device C1 is a capacitor or a lithium battery. Specifically, both capacitors and energy storage lithium batteries can be used to store and release electric energy.

In a preferred embodiment of the present invention, as shown in Figures 1 and 2, the first switch, the second switch and the third switch are all load switches, and the load switches include:

Two second N-type field effect transistors N2 connected in series, connected in series between the first terminal and the second terminal of the load switch, are used to control the conduction state of the load switch;

The charge pump K1, the output terminal of the charge pump K1 is connected to the gate of the second N-type field effect transistor N2, and is used to output the control voltage to the gate of the second N-type field effect transistor N2, and control the second N-type field effect transistor N2 On-off state and current-limiting state;

The current limiting controller K2 is connected to the charge pump K1 and the controller B1 respectively, and is used to control the control voltage output by the charge pump K1 according to the instruction of the controller B1.

Specifically, in this embodiment, two second N-type field effect transistors N2 are used to control the on-off state and current-limiting state of the load switch by utilizing its property that the conduction state can be adjusted under the influence of the gate voltage; The pump K1 generates a voltage to affect the gate of the second N-type field effect transistor N2; the current-limiting controller K2 is used to control the voltage generated by the charge pump K1 to control the second N-type field effect transistor N2, and the controller B1 controls the current-limiting The control of the device K2 realizes the control of the load switch.

In a preferred embodiment of the present invention, as shown in FIG. 2, the load switch further includes a voltage selector K3, which is respectively connected to the first end and the second end of the load switch for selecting the first end and the second end of the load switch. The high level in the two terminals supplies power to the load switch.

In a preferred embodiment of the present invention, as shown in FIG. 2 , the load switch further includes a low-drop voltage source K4, which is respectively connected to a voltage high selector K3 for generating an operating voltage of the load switch from a high level.

Specifically, in this embodiment, the voltage high selector K3 can be used to select a higher high level VH according to the two ends of the load switch for power supply of the internal module; the low voltage drop voltage source K4 generates a low voltage for internal operation from VH VLDO is 5V or 3.3V; the conduction voltage of the second N-type field effect transistor N2 is set to VH+VLDO, and the charge pump K1 charges the gate voltage of the second N-type field effect transistor N2 to VH+VLDO. At this time, the NMOS is completely conduction.

In a preferred embodiment of the present invention, as shown in FIG. 2 , the load switch further includes an overvoltage protection unit K5 and an undervoltage protection unit K6, which are respectively connected to the charge pump K1, and are used to protect the load switch when the operating voltage is too high or When it is too low, the control load switch is not turned on.

In a preferred embodiment of the present invention,

Each of the second N-type field effect transistors N2 is provided with a parasitic diode D1, and the first end and the second end of the load switch are both connected to the drain of a second N-type field effect transistor DI.

Specifically, in this embodiment, the second N-type field effect transistor N2 and the parasitic diode D1 are arranged back-to-back, and the anode and cathode of the parasitic diode D1 are set in opposite directions, that is, the two second N-type field effect transistors N2 The source and drain are reversely connected in series, which can effectively prevent uncontrolled voltage backfeeding.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the implementation and protection scope of the present invention. For those skilled in the art, they should be able to realize that all equivalents made by using the description and illustrations of the present invention The solutions obtained by replacement and obvious changes shall all be included in the protection scope of the present invention.

Claims (9)

1. A multi-cell series lithium battery based on a load switch, which is applied to the field of battery power supply, is characterized in that, comprising: A plurality of series-connected lithium batteries, the series-connected lithium batteries are sequentially connected in series to form a series-connected lithium battery pack, the positive pole of each of the series-connected lithium batteries is respectively connected to the first end of a first switch, and the negative pole of each of the series-connected lithium batteries respectively connected to the first end of a second switch; The negative lithium battery cell is connected in series with the series lithium battery cell group, and the positive electrode of the negative electrode lithium battery cell is connected to the negative electrode of the series lithium battery cell group, and the positive electrode of the negative electrode lithium battery cell is also connected to the first end of a third switch, so The negative electrode of the negative electrode lithium battery cell is connected to the source electrode of a first N-type field effect transistor; An energy storage, the positive pole of the energy storage is connected to the second end of each of the first switches and the second end of the third switch, and the negative pole of the energy storage is connected to each of the second the second end of the switch and the drain of the first N-type field effect transistor; A voltage detector, respectively connected to the positive and negative poles of each of the series-connected lithium cells and the negative lithium cells, for detecting the real-time voltage of each of the series-connected lithium cells and the negative lithium cells; a controller, respectively connected to the voltage detector, the control terminal of the first switch, the control terminal of the second switch, the control terminal of the third switch, and the gate of the first N-type field effect transistor , for controlling the first switch, the second switch, the third switch, and the second An on-off combination of an N-type field effect transistor transfers the electricity of the negative lithium battery cell to the corresponding lithium battery cell in series through the energy storage device. 2. The multi-cell lithium battery in series according to claim 1, wherein the controller is a programmable logic controller, and the controller includes: The comparison unit is connected to the voltage detector, and a balanced voltage difference is preset for the real-time voltage of any one of the series-connected lithium batteries to be lower than the real-time voltage of the negative lithium battery and the difference is greater than the balanced voltage. When there is a voltage difference, send a control command to the control unit; The control unit is connected to the comparison unit, and a charging and discharging time is preset, and the control unit is used to control the conduction of the first N-type field effect transistor after receiving the control instruction, and control the second Three switches conduct and limit current; After the charging and discharging time has elapsed, turning off the first N-type field effect transistor and the third switch; Afterwards, controlling the conduction of the first switch of the corresponding series-connected lithium battery cell, controlling the conduction and current limiting of the second switch of the corresponding series-connected lithium battery cell; After the charging and discharging time elapses, the first switch and the second switch are turned off. 3. The multi-cell lithium battery in series according to claim 2, wherein the voltage detector is an analog-to-digital conversion detection device for converting the detected real-time voltage into a digital signal. 4. The multi-cell lithium battery in series according to claim 1, wherein the energy storage device is a capacitor or a lithium battery cell. 5. The multi-cell lithium battery in series according to claim 1, wherein the first switch, the second switch, and the third switch are all load switches, and the load switches include: Two second N-type field effect transistors connected in series, connected in series between the first terminal and the second terminal of the load switch, for controlling the conduction state of the load switch; A charge pump, the output end of the charge pump is connected to the gate of the second N-type field effect transistor, and is used to output a control voltage to the gate of the second N-type field effect transistor to control the second N-type field effect transistor. The on-off state and current-limiting state of the FET; A current-limiting controller is connected to the charge pump and the controller respectively, and is configured to control the control voltage output by the charge pump according to instructions of the controller. 6. The multi-cell lithium battery in series according to claim 5, wherein the load switch further comprises a voltage high selector connected to the first end and the second end of the load switch respectively for selecting the selected voltage. The high level of the first terminal and the second terminal of the load switch is used to supply power to the load switch. 7. The multi-cell lithium battery in series according to claim 6, wherein the load switch further includes a low-drop voltage source connected to the voltage high selector for generating the high voltage from the high level. The operating voltage of the load switch described above. 8. The multi-cell lithium battery in series according to claim 5, wherein the load switch further comprises an overvoltage protection unit and an undervoltage protection unit, which are respectively connected to the charge pump for switching on the load switch. When the operating voltage is too high or too low, the load switch is controlled not to conduct. 9. The multi-cell lithium battery in series according to claim 5, wherein each of the second N-type field effect transistors is provided with a parasitic diode, and the first end and the second end of the load switch are connected to A drain of the second N-type field effect transistor.