A protection circuit for a variable voltage lithium battery pack

Abstract

A protection circuit for a variable voltage lithium battery pack, the protection circuit comprising a first battery pack; a first RC filter; a first signal detection and processing circuit; a second battery pack; a second RC filter; a second signal detection and processing circuit; characterized in that it also comprises a bidirectional isolation circuit; and an input-output interface circuit. The advantages of the present invention are that, without changing the existing charge and discharge interface, during charging, the two lithium battery packs and their protection circuits in the pack are charged with a common positive pole and controlled separately; during discharging, the two lithium battery packs and their protection circuits are determined by an external connection mode whether they work in a series state or a parallel state, and the use is flexible and convenient; the variable voltage output of the battery pack is realized, which greatly broadens the application range of the battery pack.

Description

Technical Field

[0001] The invention relates to a lithium battery protection circuit, in particular to a protection circuit for a variable voltage lithium battery pack. Background Art

[0002] Overcharging, overdischarging, overtemperature or overcurrent of lithium batteries will affect the service life of the battery, especially overcharging can easily cause explosion and other dangers. For safety reasons, protection boards are installed in the charging and discharging circuits of lithium batteries, and the industry has strict requirements for the design of charging protection circuits for lithium batteries.

[0003] like Figure 1 As shown, it is a working principle diagram of the lithium battery protection circuit in the prior art. In order to filter out interference signals, an RC filter circuit 2' is usually connected between the lithium battery pack 1' and the signal detection and processing circuit 3'. When charging, the charger wakes up the lithium battery protection circuit through the ID port, and the signal detection and processing circuit 3' monitors the voltage of each battery cell (more than two lithium batteries in parallel are also counted as one lithium battery) and the battery pack temperature and other data in real time. When all the battery cells are not overcharged and other charging conditions are met, the signal detection and processing circuit 3' outputs a charging permission signal to the ID end through the input and output interface circuit 4', and the charger continues to charge; on the contrary, when any battery cell is overcharged or other charging conditions are not met, the signal detection and processing circuit 3' A charging prohibition signal is output to the ID end through the input-output interface circuit 4', and the charger stops charging; during discharge, the discharge control circuit wakes up the lithium battery protection circuit through the ID port (or another port), and the signal detection and processing circuit 3' monitors the voltage of each battery cell, the battery pack temperature and other data in real time. When all battery cells are not over-discharged and other discharge conditions are met, the signal detection and processing circuit 3' outputs a discharge permission signal to the ID end through the input-output interface circuit 4', and the discharge control circuit continues to discharge; conversely, when any battery cell is over-discharged or other discharge conditions are not met, the signal detection and processing circuit 3' outputs a discharge prohibition signal to the ID end through the input-output interface circuit 4', and the discharge control circuit stops discharging.

[0004] The lithium battery protection circuit corresponding to the lithium battery pack in the above-mentioned prior art can usually only output a fixed nominal voltage. In actual applications, for the convenience of use, the application of dual voltage is becoming more and more popular, that is, a battery pack contains two lithium battery packs and their protection circuits, which are presented to the outside as two positive output terminals and two negative output terminals. When charging, the two groups of lithium batteries and their protection circuits share a common ground and are respectively positively controlled to charge; when discharging, the external connection method determines whether the two groups of lithium batteries work in a series state or a parallel state. At present, for the cost and the compatibility of the front and rear interfaces of the new and old battery packs, for the protection circuit of the dual-voltage battery pack, it is generally required that the number of ports corresponding to the input and output interface circuits in the protection circuit cannot be increased at will, and there are coordination tasks such as parameter allocation and data transmission processing between the two signal detection circuits of the two lithium battery packs in the dual-voltage battery pack, and the two signal detection processing circuits sometimes share a common ground and sometimes do not share a common ground, which brings difficulties to the circuit design, making the circuit structure in the existing design complex and the design and manufacturing costs high.

[0005] In addition, considering that the existing old battery pack with single voltage output has some fixed designs, such as integrating the discharge protection execution circuit into the lithium battery protection circuit, the discharge protection execution circuit itself is an existing functional module, which includes a power switch circuit 5', a freewheeling circuit 6' and a load detection circuit 7', such as Figure 4 As shown, in this case, if two old battery packs with single voltage output are directly combined to achieve dual voltage output, the components in the original freewheeling circuit may be damaged by overcurrent when the two old battery packs are connected in series, and the traditional freewheeling circuit connection method is no longer applicable; and during discharge control, the signal detection and processing circuit cannot identify the series and parallel state of the battery voltage corresponding to the external device, so it is impossible to make a corresponding protection strategy for the battery pack. Therefore, in order to continue to use the old battery pack in the existing technology in the new battery pack with dual voltage output, while ensuring the reliable operation of each component in the new circuit, it is necessary to redesign and improve the protection circuit of the new battery pack to meet the circuit safety requirements of dual voltage output and take into account the compatible use of the old battery pack. Summary of the invention

[0006] The first technical problem to be solved by the present invention is to provide a protection circuit for a variable voltage lithium battery pack with a simple circuit structure and good compatibility in view of the above-mentioned existing technical status.

[0007] The second technical problem to be solved by the present invention is to provide a protection circuit for a variable voltage lithium battery pack that can prevent damage to freewheeling components and has high working reliability in view of the above-mentioned existing technical status.

[0008] The third technical problem to be solved by the present invention is to provide a protection circuit for a variable voltage lithium battery pack that can effectively identify the series-parallel working voltage corresponding to an external load in response to the above-mentioned existing technical status.

[0009] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a protection circuit of a variable voltage lithium battery pack, the protection circuit comprising

[0010] A first battery pack includes at least two lithium batteries connected in series;

[0011] The first RC filter includes a plurality of RC filter circuits connected in series with each lithium battery in the first battery pack;

[0012] The first signal detection processing circuit comprises a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the first RC filter is connected to the corresponding detection signal input terminal of the first signal detection processing circuit;

[0013] A second battery pack includes at least two lithium batteries connected in series;

[0014] The second RC filter includes a plurality of RC filter circuits connected in series with each lithium battery in the second battery pack;

[0015] The second signal detection processing circuit comprises a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the second RC filter is connected to the corresponding detection signal input terminal of the second signal detection processing circuit;

[0016] It is characterized in that: the protection circuit also includes

[0017] A bidirectional isolation circuit, which can realize bidirectional communication and signal isolation between the first signal detection and processing circuit and the second signal detection and processing circuit, and the bidirectional isolation circuit includes a first signal transmission end and a second signal transmission end;

[0018] An input-output interface circuit, comprising a first signal terminal and a second signal terminal capable of realizing bidirectional communication, the input-output interface circuit being used to realize signal transmission between the battery pack and the charger and between the battery pack and the discharge controller;

[0019] Among them, the first signal detection and processing circuit includes a first communication end and a second communication end, the second signal detection and processing circuit includes a third communication end, the first signal transmission end of the bidirectional isolation circuit is connected to the first communication end, the second signal transmission end of the bidirectional isolation circuit is connected to the third communication end, the first signal end of the input-output interface circuit is connected to the second communication end of the first signal detection and processing circuit, and the second signal end of the input-output interface circuit is connected to the input end of the charger circuit or the discharge controller as a total output end.

[0020] In order to simplify the circuit structure, as an option, the bidirectional isolation circuit can use an optocoupler as the core, specifically including a first optocoupler, a second optocoupler, a first resistor and a second resistor, the first communication end including a first output communication end and a first input communication end, and the third communication end including a third output communication end and a third input communication end; wherein, the positive electrode of the light-emitting diode of the first optocoupler is connected to the first output communication end, the negative electrode of the light-emitting diode of the first optocoupler is connected to the negative electrode of the first battery group via the first resistor, the transistor collector of the first optocoupler is connected to the third input communication end, and the transistor emitter of the first optocoupler is connected to the negative electrode of the second battery group; the positive electrode of the light-emitting diode of the second optocoupler is connected to the third output communication end, the negative electrode of the light-emitting diode of the second optocoupler is connected to the negative electrode of the second battery group via the second resistor, the transistor collector of the second optocoupler is connected to the first input communication end, and the transistor emitter of the second optocoupler is connected to the negative electrode of the first battery group.

[0021] Preferably, the first signal detection and processing circuit and the second signal detection and processing circuit can be implemented by various chips in the prior art. Preferably, an integrated circuit of the BigSur6 model is preferred.

[0022] The technical solution adopted by the present invention to solve the second and third technical problems is: a protection circuit of a variable voltage lithium battery pack, the protection circuit comprising

[0023] A first battery pack includes at least two lithium batteries connected in series;

[0024] The first RC filter includes a plurality of RC filter circuits connected in series with each lithium battery in the first battery pack;

[0025] The first signal detection processing circuit comprises a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the first RC filter is connected to the corresponding detection signal input terminal of the first signal detection processing circuit;

[0026] A second battery pack includes at least two lithium batteries connected in series;

[0027] The second RC filter includes a plurality of RC filter circuits connected in series with each lithium battery in the second battery pack;

[0028] The second signal detection processing circuit comprises a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the second RC filter is connected to the corresponding detection signal input terminal of the second signal detection processing circuit;

[0029] It is characterized in that: the protection circuit also includes

[0030] A bidirectional isolation circuit, which can realize bidirectional communication and signal isolation between the first signal detection and processing circuit and the second signal detection and processing circuit, and the bidirectional isolation circuit includes a first signal transmission end and a second signal transmission end;

[0031] An input-output interface circuit, comprising a first signal terminal and a second signal terminal capable of realizing bidirectional communication, the input-output interface circuit being used to realize signal transmission between the battery pack and the charger and between the battery pack and the discharge controller;

[0032] The first power switch circuit and the second power switch circuit are used to control the conduction and cutoff of the external discharge controller circuit when the first battery pack and the second battery pack are in different series-parallel states;

[0033] The freewheeling circuit provides a current loop for the reverse electromotive force generated by the inductive load at the moment when the power switch circuit is turned off;

[0034] A series-parallel detection circuit is used to detect the series-parallel working state of the protection circuit by the external load;

[0035] A load detection circuit, used to detect whether an external load is connected to the protection circuit and send a trigger signal to the first signal detection processing circuit; wherein the first signal detection processing circuit includes a first communication terminal and a second communication terminal, the second signal detection processing circuit includes a third communication terminal, the first signal detection processing circuit also includes a fourth communication terminal, a fifth communication terminal and a sixth communication terminal, and the second signal detection processing circuit also includes a seventh communication terminal;

[0036] The first signal terminal of the input-output interface circuit is connected to the sixth communication terminal of the first signal detection and processing circuit, and the second signal terminal of the input-output interface circuit is connected to the input terminal of the charger circuit or the discharge controller as a total output terminal;

[0037] The first signal transmission end of the bidirectional isolation circuit is connected to the first communication end of the first signal detection and processing circuit, and the second signal transmission end of the bidirectional isolation circuit is connected to the third communication end of the second signal detection and processing circuit;

[0038] The second communication terminal of the first signal detection processing circuit is connected to the series-parallel detection circuit; the fourth communication terminal of the first signal detection processing circuit is connected to the input terminal of the first power switch circuit, the output terminal of the first power switch circuit serves as the first negative discharge output terminal of the entire protection circuit, and the positive electrode of the first battery pack serves as the first positive discharge output terminal of the entire protection circuit; the fifth communication terminal of the first signal detection processing circuit is connected to the output terminal of the load detection circuit, and the input terminal of the load detection circuit is connected to the first negative discharge output terminal;

[0039] The seventh communication terminal of the second signal detection and processing circuit is connected to the input terminal of the second power switch circuit, the output terminal of the second power switch circuit serves as the second negative discharge output terminal of the entire protection circuit, and the positive electrode of the second battery pack serves as the second positive discharge output terminal of the entire protection circuit;

[0040] The freewheeling circuit is also connected in series between the second positive discharge output terminal and the first negative discharge output terminal.

[0041] Preferably, the bidirectional isolation circuit includes a first optocoupler, a second optocoupler, a first resistor and a second resistor, the first communication terminal includes a first output communication terminal and a first input communication terminal, and the third communication terminal includes a third output communication terminal and a third input communication terminal; wherein the positive electrode of the light-emitting diode of the first optocoupler is connected to the first output communication terminal, the negative electrode of the light-emitting diode of the first optocoupler is connected to the negative electrode of the first battery pack via the first resistor, the transistor collector of the first optocoupler is connected to the third input communication terminal, and the transistor emitter of the first optocoupler is connected to the negative electrode of the second battery pack; the positive electrode of the light-emitting diode of the second optocoupler is connected to the third output communication terminal, the negative electrode of the light-emitting diode of the second optocoupler is connected to the negative electrode of the second battery pack via the second resistor, the transistor collector of the second optocoupler is connected to the first input communication terminal, and the transistor emitter of the second optocoupler is connected to the negative electrode of the first battery pack. The dual optocoupler isolation circuit has a simple structure and is easy to implement, which can realize signal isolation between two signal detection and processing circuits and bidirectional communication between two signal detection circuits.

[0042] Preferably, the first signal detection and processing circuit and the second signal detection and processing circuit are integrated circuits of model BigSur6 respectively.

[0043] In order to ensure reliable freewheeling when the first battery pack and the second battery pack are used in series or in parallel, preferably, the freewheeling circuit includes a freewheeling diode, the positive electrode of the freewheeling diode is connected to the first negative discharge output terminal, and the negative electrode of the freewheeling diode is connected to the second positive discharge output terminal.

[0044] Since the discharge protection execution circuit is integrated in the lithium battery protection circuit, when the load is connected, the battery pack needs to know as soon as possible whether the load connected this time is to use the two battery packs in series or in parallel, so as to allocate working parameters and related data processing. In order to detect the working voltage of the external load (that is, the series-parallel use status of the two battery packs), as a preference, the series-parallel detection circuit can simply adopt the following circuit structure, which includes a digital transistor, the collector of the digital transistor is connected to the second communication end of the first signal detection and processing circuit package, the emitter of the digital transistor is connected to the negative electrode of the first battery pack, and the base of the digital transistor is connected to the negative electrode of the second battery pack.

[0045] Compared with the prior art, the advantages of the present invention are: without changing the existing charging and discharging interface, one battery pack contains two lithium battery groups, presenting two positive and two negative output terminals to the outside, and the two lithium battery groups are awakened and communicated through a bidirectional isolation circuit, the protection function is reliable, and the circuit structure is simple; when charging, the two lithium battery groups and their protection circuits in the pack are charged with positive poles controlled by a common ground, and when discharging, the two lithium battery groups and their protection circuits are determined by the external connection method whether they work in series or in parallel, which is flexible and convenient to use; the battery pack of this embodiment can output two working voltages when the two lithium battery groups are in different states of series or parallel connection, realizing the variable voltage output of the battery pack, greatly broadening the application range of the battery pack, and at the same time being compatible with the existing old battery packs with single voltage output, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is one of the working principle diagrams of the lithium battery pack protection circuit in the prior art (non-discharge protection execution circuit).

[0047] Figure 2 This is a working principle diagram of a variable voltage lithium battery pack protection circuit according to Embodiment 1 of the present invention.

[0048] Figure 3 This is a specific circuit diagram of the bidirectional isolation circuit and the input / output interface circuit in the first embodiment of the present invention.

[0049] Figure 4 This is the second working principle diagram of the lithium battery pack protection circuit in the prior art (including the discharge protection execution circuit).

[0050] Figure 5 This is a working principle diagram of a variable voltage lithium battery pack protection circuit according to the second embodiment of the present invention.

[0051] Figure 6 It is a specific circuit diagram of the bidirectional isolation circuit, input-output interface circuit, series-parallel detection circuit, freewheeling circuit, load detection circuit and power switch circuit in the second embodiment of the present invention. DETAILED DESCRIPTION

[0052] The present invention is further described in detail below with reference to the accompanying drawings.

[0053] Embodiment 1, as Figure 2 , Figure 3 As shown:

[0054] This embodiment discloses a protection circuit for a variable voltage lithium battery pack. The protection circuit includes:

[0055] The first battery pack 1 comprises at least two lithium batteries connected in series;

[0056] The first RC filter 2 includes a plurality of RC filter circuits connected in series with each lithium battery in the first battery pack 1;

[0057] The first signal detection processing circuit 3 includes a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the first RC filter 2 is connected to the corresponding detection signal input terminal of the first signal detection processing circuit 3;

[0058] The second battery pack 5 includes at least two lithium batteries connected in series;

[0059] The second RC filter 6 includes a plurality of RC filter circuits connected in series with each lithium battery in the second battery pack 5;

[0060] The second signal detection processing circuit 7 includes a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the second RC filter 6 is connected to the corresponding detection signal input terminal of the second signal detection processing circuit 7;

[0061] A bidirectional isolation circuit 8, which can realize bidirectional communication and signal isolation between the first signal detection and processing circuit 3 and the second signal detection and processing circuit 7, and the bidirectional isolation circuit 8 includes a first signal transmission terminal 81 and a second signal transmission terminal 82;

[0062] The input-output interface circuit 4 includes a first signal terminal 4a and a second signal terminal 4b that can realize two-way communication. The input-output interface circuit 4 is used to realize signal transmission between the battery pack and the charger and between the battery pack and the discharge controller.

[0063] Wherein, the first signal detection processing circuit 3 includes a first communication terminal 31 and a second communication terminal 32, the second signal detection processing circuit 7 includes a third communication terminal 71, the first communication terminal 31 of the first signal detection processing circuit 3 includes a first output communication terminal 311 and a first input communication terminal 312, the second communication terminal 32 of the first signal detection processing circuit 3 includes a second output communication terminal 321 and a second input communication terminal 322, and the third communication terminal 71 of the second signal detection processing circuit 7 includes a third input communication terminal 711 and a third output communication terminal 712;

[0064] The first signal transmission terminal 81 of the bidirectional isolation circuit 8 is connected to the first communication terminal 31 of the first signal detection and processing circuit 3, and the second signal transmission terminal 82 of the bidirectional isolation circuit 8 is connected to the third communication terminal 71 of the second signal detection and processing circuit 7. The input-output interface circuit 4 includes two signal terminals that can communicate bidirectionally. The first signal terminal 4a of the input-output interface circuit 4 is connected to the second communication terminal 32 of the first signal detection and processing circuit 3, and the second signal terminal 4b of the input-output interface circuit 4 is connected to the input terminal of the charger circuit or the discharge controller as the total output terminal ID. The input-output interface circuit 4 is arranged between the first signal detection and processing circuit 3 and the total output terminal ID.

[0065] In the above circuit module, the first RC filter 2, the second RC filter 6, the first signal detection processing circuit 3 and the second signal detection processing circuit 7 are all existing technologies and can be implemented using corresponding circuit structures in the existing technology. Preferably, the first signal detection processing circuit 3 and the second signal detection processing circuit 7 are respectively integrated circuit U1 and integrated circuit U2 of model BigSur6.

[0066] For the protection circuit of the dual-voltage battery pack, it is generally required that the number of ports corresponding to the input-output interface circuit 4 in the protection circuit cannot be increased at will. The original input-output interface circuit 4 in the case of a single battery pack has two corresponding ports. Now, with the protection circuit of the dual-voltage battery pack, only one input-output interface circuit 4 is retained, and the corresponding ports are still two. The input-output interface circuit 4 here can be implemented using the circuit structure in the prior art. In this embodiment, the following circuit structure is specifically adopted: the input-output interface circuit 4 includes a first transistor Q1 and a second transistor Q2, the collector of the first transistor Q1 is connected to the second input communication terminal 322, and the emitter of the first transistor Q1 is connected to the negative electrode of the first battery pack 1; the base of the second transistor Q2 is connected to the second output communication terminal 321, and the emitter of the second transistor Q2 is connected to the negative electrode of the first battery pack 1. The collector of the second transistor Q2 and the base of the first transistor Q1 are connected together as the total output terminal ID connected to the input terminal of the charger circuit or the discharge controller.

[0067] The core components of the bidirectional isolation circuit 8 can be optical isolation, magnetic isolation, or capacitance-based isolation components. The bidirectional isolation circuit 8 of this embodiment adopts an optical coupling structure. Specifically, the bidirectional isolation circuit 8 includes a first optical coupler U3, a second optical coupler U4, a first resistor R1, and a second resistor R2. The positive electrode of the light-emitting diode of the first optical coupler U3 is connected to the first output communication terminal 311, and the negative electrode of the light-emitting diode of the first optical coupler U3 is connected to the negative electrode of the first battery group 1 via the first resistor R1. The transistor collector of the first optical coupler U3 is connected to the third input communication terminal 711, and the transistor emitter of the first optical coupler U3 is connected to the negative electrode of the second battery group 5; the positive electrode of the light-emitting diode of the second optical coupler U4 is connected to the third output communication terminal 712, and the negative electrode of the light-emitting diode of the second optical coupler U4 is connected to the negative electrode of the second battery group 5 via the second resistor R2. The transistor collector of the second optical coupler U4 is connected to the first input communication terminal 312, and the transistor emitter of the second optical coupler U4 is connected to the negative electrode of the first battery group 1.

[0068] The basic working principle of the first embodiment is as follows:

[0069] When the charger or discharge controller is not connected to the dual-voltage battery pack, or is connected but not working, the total output terminal ID port does not present a valid voltage signal. At this time, the first transistor Q1 is turned off, the collector of the first transistor Q1 maintains a high level, the first signal detection processing circuit 3 is still in a dormant state, and the second signal detection processing circuit 7 is also dormant; when the charger or discharge controller is connected and starts working, the total output terminal ID port presents a valid voltage signal. At this time, the first transistor Q1 is turned on, and the second input communication terminal 322 of the first signal detection processing circuit 3 receives a change signal from the collector of the first transistor Q1 from high to low, and the first signal detection processing circuit 3 is awakened. The first signal detection processing circuit 3 then wakes up the second signal detection processing circuit 7 through the first optocoupler U3. At the same time, the first signal detection processing circuit 3 controls the second transistor Q2 to send a signal to the charger or discharge controller through the second output communication terminal 321.

[0070] When the charger or discharge controller disconnects the total output terminal ID or is still connected to the total output terminal ID but has stopped working, at this time, the first transistor Q1 is cut off, the collector of the first transistor Q1 maintains a high level, and the first signal detection and processing circuit 3 notifies the second signal detection and processing circuit 7 to enter sleep mode through the first optocoupler U3, so the first signal detection and processing circuit 3 itself also enters sleep mode.

[0071] During the charging and discharging process, the second signal detection and processing circuit 7 also monitors in real time whether the charging and discharging conditions are met. If not, the second signal detection and processing circuit 7 sends a signal to the first signal detection and processing circuit 3 through the second optocoupler U4. After receiving the charge and discharge prohibition signal, the first signal detection and processing circuit 3 stops charging and discharging, and then enters sleep.

[0072] In this embodiment, by setting a bidirectional isolation circuit 8, when the battery pack is connected to a charger or a discharge controller, the second signal detection processing circuit 7 can be awakened by the first signal detection processing circuit 3, thereby realizing the series-parallel operation of the two battery packs. At the same time, the second signal detection processing circuit 7 can output a feedback signal through the bidirectional isolation circuit 8, thereby stopping charging when the battery pack is fully charged, or stopping discharging when the battery pack is insufficient.

[0073] Embodiment 2, as Figure 5 , Figure 6 As shown:

[0074] The difference between this embodiment and the first embodiment is that in this embodiment, the discharge protection execution circuit is integrated into the lithium battery protection circuit. In order to ensure the reliable operation and safe use of the circuit, when realizing the dual-voltage battery pack application, the protection circuits of two single battery groups each with a discharge protection execution circuit cannot be simply combined directly, and some improvements and adjustments need to be made.

[0075] The protection circuit of the variable voltage lithium battery pack of this embodiment includes:

[0076] The first battery pack 1 comprises at least two lithium batteries connected in series;

[0077] The first RC filter 2 includes a plurality of RC filter circuits connected in series with each lithium battery in the first battery pack 1;

[0078] The first signal detection processing circuit 3 includes a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the first RC filter 2 is connected to the corresponding detection signal input terminal of the first signal detection processing circuit 3;

[0079] The second battery pack 5 includes at least two lithium batteries connected in series;

[0080] The second RC filter 6 includes a plurality of RC filter circuits connected in series with each lithium battery in the second battery pack 5;

[0081] The second signal detection processing circuit 7 includes a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the second RC filter 6 is connected to the corresponding detection signal input terminal of the second signal detection processing circuit 7 .

[0082] The protection circuit of this embodiment also includes:

[0083] A bidirectional isolation circuit 8, which can realize bidirectional communication and signal isolation between the first signal detection and processing circuit 3 and the second signal detection and processing circuit 7, and the bidirectional isolation circuit 8 includes a first signal transmission terminal 81 and a second signal transmission terminal 82;

[0084] An input-output interface circuit 4, comprising a first signal terminal 4a and a second signal terminal 4b capable of realizing bidirectional communication, the input-output interface circuit 4 being used to realize signal transmission between the battery pack and the charger and between the battery pack and the discharge controller;

[0085] The first power switch circuit 41 and the second power switch circuit 42 are used to control the conduction and cutoff of the external load circuit when the first battery pack 1 and the second battery pack 5 are in different series-parallel states;

[0086] The freewheeling circuit 43 provides a current loop for the reverse electromotive force generated by the inductive load at the moment when the power switch circuit is turned off; when the current passes through the inductive load (such as a coil), an induced electromotive force will be generated at both ends of the inductive load. When the current disappears, the induced electromotive force of the inductive load will generate a reverse voltage on the components in the circuit. When the reverse voltage is higher than the reverse breakdown voltage of the component, it will cause damage to the components such as triodes and thyristors. Therefore, it is usually necessary to connect a freewheeling diode Dx in reverse parallel at both ends of the inductive load. When the current flowing through the inductive load (such as a coil) disappears, the induced electromotive force generated by the inductive load is consumed by the circuit formed by the diode and the coil, thereby protecting the safety of other components in the circuit;

[0087] A series-parallel detection circuit 9 is used to detect the series-parallel working state of the protection circuit by the external load;

[0088] The load detection circuit 44 is used to detect whether an external load is connected to the protection circuit and send a trigger signal to the first signal detection processing circuit 3, wherein the first signal detection processing circuit 3 includes a first communication terminal 31 and a second communication terminal 32, and the second signal detection processing circuit 7 includes a third communication terminal 71; the first signal detection processing circuit 3 also includes a fourth communication terminal 33, a fifth communication terminal 34 and a sixth communication terminal 35, and the second signal detection processing circuit 7 also includes a seventh communication terminal 72;

[0089] The first signal terminal 4a of the input-output interface circuit 4 is connected to the sixth communication terminal 35 of the first signal detection and processing circuit 3, and the second signal terminal 4b of the input-output interface circuit 4 is connected to the input terminal of the charger circuit or the discharge controller as the total output terminal ID;

[0090] The first signal transmission terminal 81 of the bidirectional isolation circuit 8 is connected to the first communication terminal 31 of the first signal detection and processing circuit 3, and the second signal transmission terminal 82 of the bidirectional isolation circuit 8 is connected to the third communication terminal 71 of the second signal detection and processing circuit 7;

[0091] The second communication terminal 32 of the first signal detection processing circuit 3 is connected to the series-parallel detection circuit 9; the fourth communication terminal 33 of the first signal detection processing circuit 3 is connected to the input terminal of the first power switch circuit 41, the output terminal of the first power switch circuit 41 serves as the first negative discharge output terminal P1- of the entire protection circuit, and the positive electrode of the first battery pack 1 serves as the first positive discharge output terminal P1+ of the entire protection circuit; the fifth communication terminal 34 of the first signal detection processing circuit 3 is connected to the output terminal of the load detection circuit 44, and the input terminal of the load detection circuit 44 is connected to the first negative discharge output terminal P1-;

[0092] The seventh communication terminal 72 of the second signal detection and processing circuit 7 is connected to the input terminal of the second power switch circuit 42, the output terminal of the second power switch circuit 42 serves as the second negative discharge output terminal P2- of the entire protection circuit, and the positive electrode of the second battery pack 5 serves as the second positive discharge output terminal P2+ of the entire protection circuit;

[0093] A freewheeling circuit 43 is also connected in series between the second positive discharge output terminal P2+ and the first negative discharge output terminal P1-.

[0094] In this embodiment, the first negative discharge output terminal P1-, the first positive discharge output terminal P1+, the second negative discharge output terminal P2- and the second positive discharge output terminal P2+ are four reserved electrode interface terminals. When the external load is applied in series, the second negative discharge output terminal P2- and the first positive discharge output terminal P1+ are externally short-circuited, the first negative discharge output terminal P1- is the total negative electrode of the entire battery pack, and the second positive discharge output terminal P2+ is the total positive electrode of the entire battery pack; when the external load is applied in parallel, the first positive discharge output terminal P1+ and the second positive discharge output terminal P2+ are externally short-circuited as the total positive electrode of the entire battery pack, and the first negative discharge output terminal P1- and the second negative discharge output terminal P2- are externally short-circuited as the total negative electrode of the entire battery pack.

[0095] In the above circuit module, the first RC filter 2, the second RC filter 6, the first signal detection processing circuit 3 and the second signal detection processing circuit 7 are all existing technologies and can be implemented using corresponding circuit structures in the existing technology. Preferably, the first signal detection processing circuit 3 and the second signal detection processing circuit 7 are respectively integrated circuit U1 and integrated circuit U2 of model BigSur6.

[0096] The first power switch circuit 41, the second power switch circuit 42, the load detection circuit 44 and the freewheeling circuit 43 are generated because the discharge protection execution circuit is integrated in the battery pack protection circuit. The circuit structures of the first power switch circuit 41, the second power switch circuit 42, the load detection circuit 44 and the freewheeling circuit 43 are all existing technologies and can be implemented by various circuit structures in the existing technology. As a preferred embodiment, the functional modules related to the above-mentioned discharge protection execution circuit are implemented by the following specific circuit structures:

[0097] The first power switch circuit 41 includes a first field effect transistor Qa, the second power switch circuit 42 includes a second field effect transistor Qb, the freewheeling circuit 43 includes a freewheeling diode Dx, and the load detection circuit 44 includes a first diode D1 and a third resistor R3;

[0098] Among them, the positive electrode of the freewheeling diode Dx is connected to the first negative discharge output terminal P1-, and the negative electrode of the freewheeling diode Dx is connected to the second positive discharge output terminal P2+; whether connected in series or in parallel, the first negative discharge output terminal P1- can always represent the total negative electrode of the battery pack output, and the second positive discharge output terminal P2+ can always represent the total positive electrode of the battery pack output. The freewheeling diode Dx is connected in this way. Whether the two battery packs are in parallel or in series, the reverse electromotive force generated by the inductive load in the circuit at the moment when the power switch circuit is turned off can be eliminated to protect the components in the circuit; the gate of the first field effect transistor Qa is connected to the first signal detection The fourth communication terminal 33 of the processing circuit 3, the drain of the first field effect transistor Qa is connected to the first negative electrode discharge output terminal P1-, and the source of the first field effect transistor Qa is connected to the negative electrode of the first battery group 1; the gate of the second field effect transistor Qb is connected to the seventh communication terminal 72 of the second signal detection processing circuit 7, the drain of the second field effect transistor Qb is connected to the second negative electrode discharge output terminal P2-, and the source of the second field effect transistor Qb is connected to the negative electrode of the second battery group 5; the anode of the first diode D1 is connected to the first negative electrode discharge output terminal P1-, and the cathode of the first diode D1 is connected to the fifth communication terminal 34 of the first signal detection processing circuit 3 via the third resistor R3.

[0099] The core component of the bidirectional isolation circuit 8 may be optical isolation, magnetic isolation, or a capacitance-based isolation component. The bidirectional isolation circuit 8 of this embodiment includes a first optical coupler U3, a second optical coupler U4, a first resistor R1, and a second resistor R2. The first communication terminal 31 includes a first output communication terminal 311 and a first input communication terminal 312. The third communication terminal 71 includes a third input communication terminal 711 and a third output communication terminal 712.

[0100] The positive electrode of the light-emitting diode of the first optical coupler U3 is connected to the first output communication terminal 311, the negative electrode of the light-emitting diode of the first optical coupler U3 is connected to the negative electrode of the first battery pack 1 via the first resistor R1, the transistor collector of the first optical coupler U3 is connected to the third input communication terminal 711, and the transistor emitter of the first optical coupler U3 is connected to the negative electrode of the second battery pack 5;

[0101] The positive electrode of the light-emitting diode of the second optocoupler U4 is connected to the third output communication terminal 712, the negative electrode of the light-emitting diode of the second optocoupler U4 is connected to the negative electrode of the second battery group 5 via the second resistor R2, the transistor collector of the second optocoupler U4 is connected to the first input communication terminal 312, and the transistor emitter of the second optocoupler U4 is connected to the negative electrode of the first battery group 1.

[0102] The series-parallel detection circuit 9 includes a digital transistor Q3. An ordinary transistor requires an external bias resistor, but the digital transistor Q3 has a built-in bias resistor, which can simplify the circuit structure; the collector of the digital transistor Q3 is connected to the second communication terminal 32 of the first signal detection and processing circuit 3, the emitter of the digital transistor Q3 is connected to the negative electrode of the first battery group 1, and the base of the digital transistor Q3 is connected to the negative electrode of the second battery group 5.

[0103] The working principle of the second embodiment is as follows:

[0104] After the protection circuit of this embodiment is connected to the load (during discharge), it is necessary to know as soon as possible whether the current connection is a load that uses two battery packs in series or a load that uses two battery packs in parallel, so as to allocate working parameters and related data processing. Here, the series-parallel application of the external load is mainly realized through the series-parallel detection circuit 9.

[0105] like Figure 6 As shown, if the external load is applied in parallel, that is, the first negative discharge output terminal P1- and the second negative discharge output terminal P2- are externally short-circuited, the negative electrode of the first battery group 1 is connected to the first negative discharge output terminal P1- through the turned-on first field effect transistor Qa, and the negative electrode of the second battery group 5 is connected to the second negative discharge output terminal P2- through the turned-on second field effect transistor Qb. At this time, the negative electrode of the first battery group 1 and the negative electrode of the second battery group 5 are at the same potential, the digital transistor Q3 is cut off, and the second communication terminal 32 of the first signal detection and processing circuit 3 connected to the collector of the digital transistor Q3 obtains a high level (with an internal pull-up).

[0106] If the external load is applied in series, the second negative discharge output terminal P2- and the first positive discharge output terminal P1+ are externally short-circuited, the second positive discharge output terminal P2+ is the total positive output of the entire battery pack, the first negative discharge output terminal P1- is the total negative output of the entire battery pack, and the negative electrode B2- of the second battery group 5 is connected to the second negative discharge output terminal P2- (that is, the first positive discharge output terminal P1+) through the turned-on second field effect transistor Qb. At this time, the base of the digital transistor Q3 is connected to the positive electrode of the first battery group 1, and the emitter of the digital transistor Q3 is connected to the negative electrode of the first battery group 1. The digital transistor Q3 is turned on, and the second communication terminal 32 of the first signal detection and processing circuit 3 connected to the collector of the digital transistor Q3 obtains a low level.

[0107] It can be seen that the high and low levels obtained by the second communication terminal 32 of the first signal detection and processing circuit 3 can determine whether the external load is applied in series or in parallel.

[0108] The first signal terminal and the second signal terminal of the input / output interface circuit 4 in this embodiment are signal terminals that can realize bidirectional communication. The specific circuit structure and implementation principle of the input / output interface circuit 4 are the same as those in the first embodiment and will not be described in detail here.

[0109] In addition, the working principle of the bidirectional isolation circuit 8 in this embodiment is the same as that in the first embodiment, and will not be described in detail here.

Claims

1. A protection circuit for a variable voltage lithium battery pack, the protection circuit comprising A first battery pack (1) comprises at least two lithium batteries connected in series; The first RC filter (2) comprises a plurality of RC filter circuits connected in series with each lithium battery in the first battery pack (1); The first signal detection processing circuit (3) comprises a plurality of detection signal input terminals and at least one communication terminal, wherein: The output end of each RC filter circuit in the first RC filter (2) is connected to the corresponding detection signal input end of the first signal detection processing circuit (3); A second battery pack (5) comprises at least two lithium batteries connected in series; The second RC filter (6) includes a plurality of RC filter circuits connected in series with each lithium battery in the second battery pack (5); The second signal detection processing circuit (7) comprises a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the second RC filter (6) is connected to the corresponding detection signal input terminal of the second signal detection processing circuit (7); It is characterized in that: the protection circuit also includes A bidirectional isolation circuit (8) capable of realizing bidirectional communication and signal isolation between the first signal detection processing circuit (3) and the second signal detection processing circuit (7), the bidirectional isolation circuit (8) comprising a first signal transmission end (81) and a second signal transmission end (82); An input-output interface circuit (4) comprises a first signal terminal (4a) and a second signal terminal (4b) capable of realizing bidirectional communication, and the input-output interface circuit (4) is used to realize signal transmission between the battery pack and the charger and between the battery pack and the discharge controller; The first signal detection processing circuit (3) includes a first communication terminal (31) and a second communication terminal (32), the second signal detection processing circuit (7) includes a third communication terminal (71), the first signal transmission terminal (81) of the bidirectional isolation circuit (8) is connected to the first communication terminal (31) of the first signal detection processing circuit (3), the second signal transmission terminal (82) of the bidirectional isolation circuit (8) is connected to the third communication terminal (71) of the second signal detection processing circuit (7), the first signal terminal (4a) of the input / output interface circuit (4) is connected to the second communication terminal (32) of the first signal detection processing circuit (3), and the second signal terminal (4b) of the input / output interface circuit (4) is connected to the input terminal of the charger circuit or the discharge controller as a total output terminal (ID); The bidirectional isolation circuit (8) comprises a first optical coupler (U3), a second optical coupler (U4), a first resistor (R1) and a second resistor (R2); the first communication terminal (31) comprises a first output communication terminal (311) and a first input communication terminal (312); and the third communication terminal (71) comprises a third output communication terminal (712) and a third input communication terminal (711); The positive electrode of the light-emitting diode of the first optical coupler (U3) is connected to the first output communication terminal (311), the negative electrode of the light-emitting diode of the first optical coupler (U3) is connected to the negative electrode of the first battery pack (1) via the first resistor (R1), the transistor collector of the first optical coupler (U3) is connected to the third input communication terminal (711), and the transistor emitter of the first optical coupler (U3) is connected to the negative electrode of the second battery pack (5); The positive electrode of the light-emitting diode of the second optical coupler (U4) is connected to the third output communication terminal (712), the negative electrode of the light-emitting diode of the second optical coupler (U4) is connected to the negative electrode of the second battery pack (5) via the second resistor (R2), the transistor collector of the second optical coupler (U4) is connected to the first input communication terminal (312), and the transistor emitter of the second optical coupler (U4) is connected to the negative electrode of the first battery pack (1); The first signal detection and processing circuit (3) and the second signal detection and processing circuit (7) are both integrated circuits of the BigSur6 model.

2. A protection circuit for a variable voltage lithium battery pack, the protection circuit comprising A first battery pack (1) comprises at least two lithium batteries connected in series; The first RC filter (2) comprises a plurality of RC filter circuits connected in series with each lithium battery in the first battery pack (1); The first signal detection processing circuit (3) comprises a plurality of detection signal input terminals and at least one communication terminal, wherein: The output end of each RC filter circuit in the first RC filter (2) is connected to the corresponding detection signal input end of the first signal detection processing circuit (3); A second battery pack (5) comprises at least two lithium batteries connected in series; The second RC filter (6) includes a plurality of RC filter circuits connected in series with each lithium battery in the second battery pack (5); The second signal detection processing circuit (7) comprises a plurality of detection signal input terminals and at least one communication terminal, wherein the output terminal of each RC filter circuit in the second RC filter (6) is connected to the corresponding detection signal input terminal of the second signal detection processing circuit (7); It is characterized in that: the protection circuit also includes A bidirectional isolation circuit (8) capable of realizing bidirectional communication and signal isolation between the first signal detection processing circuit (3) and the second signal detection processing circuit (7), the bidirectional isolation circuit (8) comprising a first signal transmission end (81) and a second signal transmission end (82); An input-output interface circuit (4) comprises a first signal terminal (4a) and a second signal terminal (4b) capable of realizing bidirectional communication, and the input-output interface circuit (4) is used to realize signal transmission between the battery pack and the charger and between the battery pack and the discharge controller; The first power switch circuit (41) and the second power switch circuit (42) are used to control the conduction or cutoff of an external load circuit when the first battery pack (1) and the second battery pack (5) are in different series-parallel states; A freewheeling circuit (43) provides a current loop for the reverse electromotive force generated by the inductive load at the moment when the power switch circuit is turned off; A series-parallel detection circuit (9) is used to detect the series-parallel working state of the protection circuit by the external load; A load detection circuit (44) for detecting whether an external load is connected to the protection circuit and sending a trigger signal to the first signal detection processing circuit (3); The first signal detection processing circuit (3) includes a first communication terminal (31) and a second communication terminal (32), and the second signal detection processing circuit (7) includes a third communication terminal (71); the first signal detection processing circuit (3) also includes a fourth communication terminal (33), a fifth communication terminal (34) and a sixth communication terminal (35), and the second signal detection processing circuit (7) also includes a seventh communication terminal (72); The first signal terminal (4a) of the input / output interface circuit (4) is connected to the sixth communication terminal (35) of the first signal detection and processing circuit (3), and the second signal terminal (4b) of the input / output interface circuit (4) is connected to the input terminal of the charger circuit or the discharge controller as a total output terminal (ID); The first signal transmission end (81) of the bidirectional isolation circuit (8) is connected to the first communication end (31) of the first signal detection and processing circuit (3), and the second signal transmission end (82) of the bidirectional isolation circuit (8) is connected to the third communication end (71) of the second signal detection and processing circuit (7); The second communication terminal (32) of the first signal detection processing circuit (3) is connected to the series-parallel detection circuit (9); the fourth communication terminal (33) of the first signal detection processing circuit (3) is connected to the input terminal of the first power switch circuit (41), the output terminal of the first power switch circuit (41) serves as the first negative discharge output terminal (P1-) of the entire protection circuit, and the positive electrode of the first battery pack (1) serves as the first positive discharge output terminal (P1+) of the entire protection circuit; the fifth communication terminal (34) of the first signal detection processing circuit (3) is connected to the output terminal of the load detection circuit (44), and the input terminal of the load detection circuit (44) is connected to the first negative discharge output terminal (P1-); The seventh communication terminal (72) of the second signal detection and processing circuit (7) is connected to the input terminal of the second power switch circuit (42), the output terminal of the second power switch circuit (42) serves as the second negative discharge output terminal (P2-) of the entire protection circuit, and the positive electrode of the second battery pack (5) serves as the second positive discharge output terminal (P2+) of the entire protection circuit; The freewheeling circuit (43) is also connected in series between the second positive discharge output terminal (P2+) and the first negative discharge output terminal (P1-); The bidirectional isolation circuit (8) comprises a first optical coupler (U3), a second optical coupler (U4), a first resistor (R1) and a second resistor (R2); the first communication terminal (31) comprises a first output communication terminal (311) and a first input communication terminal (312); and the third communication terminal (71) comprises a third input communication terminal (711) and a third output communication terminal (712); The positive electrode of the light-emitting diode of the first optical coupler (U3) is connected to the first output communication terminal (311), the negative electrode of the light-emitting diode of the first optical coupler (U3) is connected to the negative electrode of the first battery pack (1) via the first resistor (R1), the transistor collector of the first optical coupler (U3) is connected to the third input communication terminal (711), and the transistor emitter of the first optical coupler (U3) is connected to the negative electrode of the second battery pack (5); The positive electrode of the light-emitting diode of the second optical coupler (U4) is connected to the third output communication terminal (712), the negative electrode of the light-emitting diode of the second optical coupler (U4) is connected to the negative electrode of the second battery pack (5) via the second resistor (R2), the transistor collector of the second optical coupler (U4) is connected to the first input communication terminal (312), and the transistor emitter of the second optical coupler (U4) is connected to the negative electrode of the first battery pack (1); The freewheeling circuit (43) comprises a freewheeling diode (Dx), the positive electrode of the freewheeling diode (Dx) is connected to the first negative discharge output terminal (P1-), and the negative electrode of the freewheeling diode (Dx) is connected to the second positive discharge output terminal (P2+); The series-parallel detection circuit (9) comprises a digital triode (Q3), the collector of which is connected to the second communication terminal (32) of the first signal detection and processing circuit (3) package, the emitter of which is connected to the negative electrode of the first battery pack (1), and the base of which is connected to the negative electrode of the second battery pack (5).

3. The protection circuit of the variable voltage lithium battery pack according to claim 2, characterized in that: The first signal detection and processing circuit (3) and the second signal detection and processing circuit (7) are both integrated circuits of the BigSur6 model.

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