CN109278589B

CN109278589B - Bidirectional active equalization electric vehicle battery monitoring system based on PIC single chip microcomputer and control method

Info

Publication number: CN109278589B
Application number: CN201811431819.8A
Authority: CN
Inventors: 杨平; 张健; 温培和; 桂连彬; 陈昌涛
Original assignee: Sichuan Vocational College of Chemical Technology
Current assignee: Sichuan Vocational College of Chemical Technology
Priority date: 2018-11-28
Filing date: 2018-11-28
Publication date: 2021-10-22
Anticipated expiration: 2038-11-28
Also published as: CN109278589A

Abstract

The invention discloses a PIC singlechip-based bidirectional active equalization electric vehicle battery monitoring system and a control method, which comprise a lithium battery monitoring module for monitoring the voltage of a single lithium battery in a battery pack in real time, an equalization module for realizing bidirectional active equalization operation between the battery packs, a control module for realizing system control by adopting a PIC18LF27K40 chip, and an isolated communication module for realizing SPI communication between the control module and the lithium battery monitoring module. The invention adopts the special charge balancer LTC3300-1, realize the two-way initiative equilibrium of group battery and individual battery, has shortened the voltage equalization time, has raised the charge transfer efficiency, has raised the integration level and accuracy of the system, has reduced the cost, the current detection module set up, detect the current while charging and discharging of the battery, guarantee the system works normally, has raised the reliability of the system.

Description

Bidirectional active equalization electric vehicle battery monitoring system based on PIC single chip microcomputer and control method

Technical Field

The invention relates to a battery monitoring system of an electric automobile, in particular to a bidirectional active equalization battery monitoring system of the electric automobile based on a PIC single chip microcomputer and a control method.

Background

Under the great challenge of the global automobile industry facing financial crisis and energy and environmental issues, the concept of new energy vehicles has been proposed. The pure electric vehicle is developed, the electrification of an energy power system of the vehicle is realized, the strategic transformation of the vehicle industry is promoted, and the consensus is formed internationally. One of the core technologies of electric vehicles is battery technology. The battery is a power source of the electric automobile and is a main factor restricting the development of the electric automobile. Therefore, it is very important to manage the battery of the electric vehicle. The battery management system BMS of the electric automobile is a link between a user and a battery, and the main working object of the BMS is a secondary battery. Because the performance of the secondary battery is very complex and different types of batteries have great differences, the battery management system needs to improve the utilization rate of the battery, avoid overcharge and overdischarge of the battery, prolong the service life of the battery as much as possible and monitor the working state of the battery.

The existing publication No. CN107359671A discloses a charge-discharge balance control system and a control method for a space high-voltage storage battery pack, wherein voltage information is collected by a single-cell voltage sampling circuit of a storage battery, a storage battery pack balancer receives the voltage information and realizes bidirectional energy transmission between a single cell and a battery pack through a flyback transformer, so as to realize the balance of the voltage of the high-voltage storage battery pack, improve the balance speed, and realize the high-integration design of the system, and although the control system can meet the balance requirement of the high-voltage power supply system under the high common-mode voltage, the control system has the following defects:

(1) the design is complicated, with high costs: in the isolation communication mode, the storage battery single voltage sampling chip LTC6811-1 communicates with the LTC6820 through an isolation transformer, the LTC6820 needs to carry out four-wire SPI communication with a control unit through an isolator, the isolator is arranged, the complexity of system design is increased to a certain extent, and the using quantity of the isolator is increased.

(2) The reliability of the system is low: according to the technical content disclosed, the voltage information is collected through the storage battery monomer voltage sampling circuit, the voltage balance is realized through the instruction of the storage battery pack balancer by the flyback transformer, the current flowing through the storage battery pack is not detected in the balancing process, the current cannot be found in time under the condition of abnormal charging and discharging, and the reliability of the system is reduced.

(3) The accuracy of the equalization is low: in the scheme, a voltage threshold is arranged in the battery pack, and when the voltage of the single battery is detected not to be within the range of the set voltage threshold, the flyback transformer is started to realize voltage balance, so that energy transfer between the voltage of the battery pack and the voltage of the single battery is realized; therefore, the equalization operation is performed when the cell voltage is not within the set range, and the equalization operation is not performed when a certain cell is unbalanced but does not exceed the voltage threshold, so that the accuracy of the equalization among the cells in the system is reduced.

Disclosure of Invention

The invention aims to provide a PIC singlechip-based bidirectional active balancing electric vehicle battery monitoring system and a control method, and solves the problems of high design cost, low reliability and low balancing accuracy of the conventional battery balancing system.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

two-way balanced electric automobile battery monitored control system of initiative based on PIC singlechip includes:

the lithium battery monitoring module is used for monitoring the voltage of a single lithium battery in the battery pack in real time, communicating with the balancing module in real time through the GPIO port and transmitting an output signal to the control module through the isolated communication module;

the isolated communication module is used for isolating strong current and weak current and communicating with the lithium battery monitoring module through the isolation transformer and the twisted pair to enable the whole system to work in a low-voltage state;

the control module adopts a PIC18LF27K40 chip to realize system control, the current detection module detects a voltage signal of the battery pack through the sampling resistor, transmits the voltage signal to the control module to perform A/D conversion, and judges whether voltage equalization operation is needed or not through the calculated current;

the equalizing module adopts two LTC3300-1 chips, twelve groups of batteries are connected with the equalizing module through a peripheral circuit connected to the LTC3300-1 chips, and charge transfer between the battery group and a single battery needing to be balanced is realized efficiently through a voltage equalizing circuit connected with the LTC3300-1 chips.

Further, the two LTC3300-1 chips of the equalization module are connected in a daisy chain mode, the LTC3300-1 chip at the next stage of the daisy chain is U1, and the LTC3300-1 chip at the previous stage of the daisy chain is U2.

Further, the voltage equalization circuit comprises a diode D14 with a cathode connected with the pin 30 of the U2 and an anode connected with the pin 27 of the U2, a capacitor C33 and a capacitor C34 with one ends connected with the cathode of the diode D14 and the other ends connected with the anode of the diode D14 after being connected in parallel, a zener diode D15 with a cathode connected with the pin 32 of the U2 and an anode connected with the pin 27 of the U2, a resistor R32 connected with the pin 32 of the U9, a MOS tube Q6 with a gate connected with the other end of the resistor R32, a resistor R33 with one end connected with the pin 31 of the U2 and the other end connected with the source of the MOS tube Q6, a capacitor C2 with one end connected with the pin 31 of the U2 and the other end connected with the pin 27 of the U2, a resistor R2 with one end connected with the source of the MOS tube Q2 and the other end connected with the pin 27 of the U2, a resistor R2 and a drain of the MOS tube Q2 and a capacitor C2 and a drain 2 connected with the capacitor C2 after being connected in series, a voltage stabilizing diode D16 with a cathode connected with the drain of the MOS tube Q6 and an anode connected with the source of the MOS tube Q6, a transformer T1 with a dotted terminal of a primary coil connected with the 30 pin of U2 and a dotted terminal connected with the drain of the MOS tube, a capacitor C41 and a resistor R37 with one end connected with the dotted terminal of the secondary coil of the transformer T1 and the other end connected with the dotted terminal of the secondary coil of the transformer T1 after series connection, an MOS tube Q7 with a drain connected with the dotted terminal of the secondary coil of the transformer T1, a voltage stabilizing diode D17 with a cathode connected with the drain of the MOS tube Q7 and an anode connected with the source of the MOS tube Q7, a capacitor C44 and a capacitor C46 with a parallel terminal connected with the 39 pin of U2 and the other end connected with the 39 pin of U1, a resistor R40 with one end connected with the 7 pin of U2 and the other end connected with the gate of the MOS tube Q7, a resistor R7 with one end connected with the source pin of the U2 and the source pin of the MOS tube Q39, a resistor R38 with one end connected with pin 39 of U1 and the other end connected with the source of MOS transistor Q7, and a capacitor C43 with one end connected with pin 8 of U2 and the other end connected with pin 39 of U1.

Further, the lithium battery monitoring module adopts an LTC6811-1 chip U3.

Further, the isolated communication module adopts an isolated communication interface LTC6820 chip U4.

Further, the control module comprises a PIC18LF27K40 chip U5, a resistor R36 and a crystal oscillator Y1 which are connected in parallel, one end of the resistor R36 is connected with a pin 9 of U5, the other end of the resistor R36 is connected with a pin 10 of U5, one end of the capacitor C38 is connected with a pin 9 of U5, the other end of the capacitor C38 is grounded, one end of the capacitor C40 is connected with a pin 10 of U5, the other end of the capacitor C40 is grounded, a diode D18 of which the anode is connected with a pin 16 of U5, a resistor R41 of which one end is connected with the cathode of the diode D18 and the other end of the diode D20 is grounded, a diode D20 of which the anode is connected with a pin 17 of U5, a resistor R20 of which one end is connected with the cathode of the diode D20 and the other end of the diode D20 is grounded, a diode D20 of which the cathode is connected with the cathode of the diode D20, a triode Q20, one end of which the base is connected with the diode R20 and the cathode of the diode D20, the resistor R47 is connected with the collector of the triode Q8 at one end and the cathode of the diode D19 at the other end, the switch S1 and the capacitor C52 are connected with the anode of the diode D19 at one end and the ground at the other end after being connected in parallel, the 7 pin of the U5 is connected with the 5 pin of the U4, the 14 pin of the U5 is connected with the 4 pin of the U4, the 15 pin of the U5 is connected with the 3 pin of the U4, and the 18 pin of the U5 is connected with the 2 pin of the U4.

Furthermore, the current detection module comprises an AD7400A chip U6, an RS722 chip U7, a capacitor C6 with one end connected to pin 1 of U6 and the other end grounded, a capacitor C6 with one end connected to pin 2 of U6 and the other end connected to pin 3 of U6, a resistor R6 and a resistor R6 which are connected in parallel with the capacitor C6 after series connection, a capacitor C6 with one end connected to pin 14 of U6 and the other end connected to pin 16 of U6, a capacitor C6 with one end connected to pin 3 of U6 and the other end grounded, a capacitor C6 with one end connected to pin 1 of U6 and the other end connected to pin 3 of U6 and the resistor R6 after series connection, a resistor R6 with one end connected between the capacitor C6 and the resistor R6 and the other end connected to pin 11 of U6, a resistor R6 with one end connected to pin 1 of U6 and the other end connected to pin 2 of U6, and the resistor R6 and the other end connected to pin 1 of U6 and the other end connected to pin 6 and the resistor R6, one end of the resistor R81 is connected to a 7 pin of the U7, the other end of the resistor R76 is connected to a 6 pin of the U7, one end of the resistor R76 is connected between the capacitor C61 and the resistor R74, the other end of the resistor R76 is connected to a 5 pin of the U7, one end of the capacitor C64 is connected to a 5 pin of the U7, the other end of the capacitor C64 is grounded, one end of the capacitor C59 is connected to an 8 pin of the U7, the other end of the capacitor C59 is grounded, a 7 pin of the U7 is connected to a 24 pin of the U5, the 8 pin of the U7 and a 14 pin of the U6 are both loaded with 5V voltage, one end of the resistor R77 and the resistor R79 which are connected is grounded, and the resistor R77 and the resistor R75 are connected to the equalizing module.

The control method of the bidirectional active balancing electric vehicle battery monitoring system based on the PIC singlechip comprises the following steps:

(1) the communication between the control module and the lithium battery monitoring module is realized through the isolated communication module, the lithium battery monitoring module monitors the voltage of a single lithium battery in the battery pack in real time and transmits data to a voltage balancing circuit of the balancing module;

(2) when the lithium battery monitoring module detects that the voltage of an individual battery is higher than the voltages of other batteries in the battery pack, a discharging operation is performed, the MOS tube Q6 of the primary coil is switched on, the current flowing into the same-name end of the primary coil of the transformer T1 rises in a slope mode, until a programming peak current is detected at the circuit detection input end, the MOS tube Q6 is switched off immediately, and the energy stored in the transformer T1 is transferred to the secondary coil;

(3) synchronously switching on the MOS tube Q7 of the secondary coil, enabling the output current of the synonym end of the secondary coil to flow in the secondary coil of the transformer T1, transferring charges to the whole battery pack until the current in the secondary coil is reduced to zero, realizing the discharge operation, and once the current in the secondary coil reaches zero, rapidly switching off the MOS tube Q7 and switching on the MOS tube Q6 again;

(4) and (4) after the discharging operation is finished, repeating the charge transfer operation in the steps (2) to (3) in the next round until the voltage balance of each single battery is monitored.

(2) when the lithium battery monitoring module detects that the voltage of an individual battery is lower than the voltage of other batteries in the battery pack, the charging operation is carried out, the MOS tube Q7 of the secondary coil is switched on, the current flowing into the synonym terminal of the secondary coil of the transformer T1 flows out through the whole battery pack, and once the peak detection current is reached in the secondary coil, the MOS tube Q7 of the secondary coil is switched off, which is the same as the discharging condition;

(3) the MOS transistor Q6 of the primary winding is switched on synchronously, current then flows in the primary winding, the selected battery can be charged from the whole secondary battery pack, once the current in the primary winding drops to zero, the MOS transistor Q6 of the primary winding is switched off and the MOS transistor Q7 of the secondary winding is switched on again;

(4) and (4) after the charging operation is finished, repeating the charge transfer operation in the steps (2) to (3) in the next round until the voltage balance of each single battery is monitored.

Compared with the prior art, the invention has the following beneficial effects:

(1) the isolated SPI interface chip LTC6820 is connected with an LTC6811-1 chip of the lithium battery monitoring module through the isolation transformer and the twisted pair, when the isolated SPI interface chip LTC6820 is communicated with a PIC18LF27K40 chip of the control module, the isolated SPI interface chip and the LTC6811-1 chip are in direct communication, an isolator does not need to be added, the complexity of a circuit is reduced on the premise that the communication effect is guaranteed, isolation between strong current and weak current with low cost is achieved, the problem that the design cost of an existing battery equalization system is high is solved, meanwhile, the power consumption of the system can be well reduced by adopting a low-power-consumption operation mode, and the service time of a battery is prolonged.

(2) The LTC6811-1 chip of the lithium battery monitoring module can adopt a daisy chain connection mode to improve the number of monitoring batteries, the input end of the LTC6811-1 chip is used for filtering high-frequency interference through an RC low-pass filter, and the current detection module connected with the battery pack is used for detecting charging and discharging currents of 12 channels, so that the whole battery system can be ensured to run in a good working state, and the reliability of the system is improved.

(3) When the lithium battery monitoring module monitors that the voltage of a certain battery is higher or lower than the voltages of other batteries in the battery pack, the voltage can be immediately balanced through the balancing module, the response speed is high, and the sensitivity for detecting the voltage abnormality of the single battery is high, so that high-precision balancing is realized.

(4) The LTC3300-1 chip of the equalizing module can carry out transformer-based bidirectional active balance control on 6 batteries in series, charges from any selected battery can be transmitted back and forth between the LTC3300-1 chip and the whole battery pack with high efficiency, and the LTC3300-1 chip is provided with a unique level conversion SPI compatible serial interface, can complete series connection of a plurality of LTCs 3300-1 without adopting an optical coupler or an isolator, realizes active balance of a longer battery pack in series connection, and completes efficient charge transfer between a given unbalanced battery and an adjacent larger battery pack in the battery pack within the least time.

Drawings

Fig. 1 is a schematic view of the overall structure of the present invention.

Fig. 2 is a circuit diagram of the control module.

FIG. 3 is a diagram of a daisy-chain mode expansion connection of two LTC3300-1 chips of an equalization module.

Fig. 4 is a voltage equalization circuit diagram.

Fig. 5 is a connection circuit diagram of the lithium battery monitoring module and the isolated communication module.

Fig. 6 is a circuit diagram of the current detection module.

Detailed Description

The present invention will be further described with reference to the following description and examples, which include but are not limited to the following examples.

Examples

As shown in fig. 1, the bidirectional active balancing electric vehicle battery monitoring system based on the PIC single-chip microcomputer disclosed by the invention comprises:

As shown in fig. 2, the control module includes a PIC18LF27K40 chip U5, a resistor R36 and a crystal oscillator Y1 connected in parallel, one end of the resistor R36 and the other end of the resistor R36 are connected to pin 9 of U5 and pin 10 of U5, a capacitor C38 connected to pin 9 of U5 and the other end of the capacitor C38 are grounded, a capacitor C40 connected to pin 10 of U5 and the other end of the capacitor C40 are grounded, a diode D18 connected to pin 16 of U5, a resistor R41 connected to the cathode of the diode D18 and the other end of the diode D18, a diode D20 connected to pin 17 of U5, a resistor R44 connected to the cathode of the diode D20 and the other end of the diode D5, a triode Q8 connected to the anode of the diode D19 and a triode Q8 connected to the emitter and the cathode of the triode Q8, and one end of the triode Q8 is connected to the base of the transistor Q8, The other end of the resistor R46 is connected with the cathode of a diode D19, one end of the resistor R47 is connected with the collector of a triode Q8, the other end of the resistor R47 is connected with the cathode of a diode D19, after the resistor R47 is connected in parallel, one end of the switch S1 is connected with the anode of a diode D19, the other end of the switch S1 is grounded, and a capacitor C52 are connected with one another, a pin 7 of the U5 is connected with a pin 5 of the U4, a pin 14 of the U5 is connected with a pin 4 of the U4, a pin 15 of the U5 is connected with a pin 3 of the U4, and a pin 18 of the U5 is connected with a pin 2 of the U4.

As shown in fig. 3, to achieve active equalization of longer series connected battery packs, the LTC3300-1 chip U1 and LTC3300-1 chip U2 of the equalization module are extended using daisy chain mode; the LTC3300-1 can perform transformer-based bi-directional active equalization control for 6 series connected cells, and charge from any selected cell can be transferred back and forth between itself and a 12-stage adjacent cell with high efficiency. Meanwhile, the single-chip low temperature co-fired power supply is provided with a unique level conversion SPI compatible serial interface, so that a plurality of LTCs 3300-1 can be connected in series without adopting an optical coupler or an isolator, and the active balance of a longer series-connected battery pack is realized.

In contrast to passive equalization, active equalization circuits do not discharge the charge uselessly through resistors in the form of heat, but rather effect a transfer of charge between the individual cells and the entire battery. The existing active equalization circuits transfer charge to the battery pack by releasing the voltage of the individual battery when the voltage of the battery is too high. However, if the voltage of each cell is lower than that of the majority of the cells in the whole battery pack, the balancing efficiency is very low and the balancing time is long. The bidirectional active equalization designed by the invention can realize the efficient transfer of charges in the least time under the two unbalanced states.

As shown in fig. 4, the voltage equalization circuit includes a diode D14 having a cathode connected to the 30 pin of U2 and an anode connected to the 27 pin of U2, a zener diode D15 having a cathode connected to the cathode of diode D14 and an anode connected to the anode of diode D14, a resistor R32 connected to the 32 pin of U2, a MOS transistor Q6 having a gate connected to the other end of resistor R32, a resistor R33 having one end connected to the 31 pin of U2 and the other end connected to the source of MOS transistor Q6, a capacitor C2 having one end connected to the 31 pin of U2 and the other end connected to the pin of U2, a resistor R2 having one end connected to the source of MOS transistor Q2 and the other end connected to the pin 27 of U2, a resistor R2 having one end connected to the 30 pin of U2, the other end connected to the drain of MOS transistor Q2, and a capacitor C2 connected to the drain of the capacitor C2 and 2, a voltage stabilizing diode D16 with a cathode connected with the drain of the MOS tube Q6 and an anode connected with the source of the MOS tube Q6, a transformer T1 with a dotted terminal of a primary coil connected with the 30 pin of U2 and a dotted terminal connected with the drain of the MOS tube, a capacitor C41 and a resistor R37 with one end connected with the dotted terminal of the secondary coil of the transformer T1 and the other end connected with the dotted terminal of the secondary coil of the transformer T1 after series connection, an MOS tube Q7 with a drain connected with the dotted terminal of the secondary coil of the transformer T1, a voltage stabilizing diode D17 with a cathode connected with the drain of the MOS tube Q7 and an anode connected with the source of the MOS tube Q7, a capacitor C44 and a capacitor C46 with a parallel terminal connected with the 39 pin of U2 and the other end connected with the 39 pin of U1, a resistor R40 with one end connected with the 7 pin of U2 and the other end connected with the gate of the MOS tube Q7, a resistor R7 with one end connected with the source pin of the U2 and the source pin of the MOS tube Q39, a resistor R38 with one end connected with pin 39 of U1 and the other end connected with the source of MOS transistor Q7, and a capacitor C43 with one end connected with pin 8 of U2 and the other end connected with pin 39 of U1.

As shown in fig. 5, the lithium battery monitoring module employs an LTC6811-1 chip U3, and the isolated communication module employs an isolated communication interface LTC6820 chip U4. The battery monitoring module is characterized in that an RC low-pass filter consisting of a capacitor C64, a resistor R56 and a resistor R55 can be used for filtering high-frequency interference, meanwhile, the resistor can protect an input port, and the lithium battery monitoring module configures a general I/O port GPIO3-GPIO5 of the lithium battery monitoring module into an SPI port which is connected with a corresponding port of an LTC3300-1 at the bottom end of a daisy chain to realize serial communication; the battery pack to be tested is not only a power source of the electric automobile, but also supplies power to the whole control circuit. Because the series voltage of the battery pack is very high, and the whole control system needs to work in a low-voltage state, in order to realize the isolation of strong current and weak current, the isolation communication chip LTC6820 is combined with a low-cost transformer to solve the communication problem of the strong current and weak current parts.

As shown in fig. 6, the current detection module includes an AD7400A chip U6, an RS722 chip U7, a capacitor C6 having one end connected to pin 1 of U6 and the other end grounded, a capacitor C6 having one end connected to pin 2 of U6 and the other end connected to pin 3 of U6, a resistor R6 and a resistor R6 connected in parallel with capacitor C6 after series connection, a capacitor C6 having one end connected to pin 14 of U6 and the other end connected to pin 16 of U6, a capacitor C6 having one end connected to pin 3 of U6 and the other end grounded, a capacitor C6 and a resistor R6 connected in series connection, a resistor R6 having one end connected between the capacitor C6 and the resistor R6 and the other end connected to pin 11 of U6, a resistor R6 having one end connected to pin 1 of U6 and the other end connected to pin 2 of U6, a resistor R6 connected to pin 1 of U6 and the other end connected to pin 7 and the resistor R6 and the other end connected to pin 7, one end of the resistor R81 is connected to a 7 pin of the U7, the other end of the resistor R76 is connected to a 6 pin of the U7, one end of the resistor R3829 is connected between the capacitor C61 and the resistor R74, the other end of the resistor R76 is connected to a 5 pin of the U7, one end of the capacitor C64 is connected to a 5 pin of the U7, the other end of the capacitor C64 is grounded, one end of the capacitor C59 is connected to an 8 pin of the U7, the other end of the capacitor C59 is grounded, a 7 pin of the U7 is connected to a 24 pin of the U5, the 8 pin of the U7 and a 14 pin of the U6 are both loaded with 5V voltage, one end of the resistor R77 and the resistor R79 are connected to the ground, and a pin 21 of the U1 in the equalizing module is connected between the resistor R77 and the resistor R75.

In the scheme, the current detection is realized by adopting an analog isolation mode, an isolation ADC is jointed with an active filter, an AD7400A chip is a second-order sigma-delta type isolation ADC, an analog voltage signal obtained by sampling is input to an AD7400A chip through a differential input noise reduction filter consisting of resistors R75, R79 and a capacitor C60, the signal is sampled, and the result is isolated and output. The noise is shaped by the modulator and then shifted to a higher frequency, and finally the analog voltage signal is transmitted to the RS772 to be recovered and transmitted to the PIC18LF27K40 to be A/D converted.

When the transformer is adopted for balance control, a primary coil of the transformer is connected with a single battery in parallel, a secondary coil of the transformer is connected with the whole series battery pack in parallel, and the two working modes of charging and discharging of the bidirectional active balance control circuit are analyzed by combining the voltage balance circuit.

When the lithium battery monitoring module detects that the voltage of an individual battery is higher than the voltages of other batteries in the battery pack, a discharging operation is performed, the MOS tube Q6 of the primary coil is turned on, the current flowing into the dotted terminal of the primary coil of the transformer T1 rises in a ramp manner until a programmed peak current is detected at the circuit detection input terminal, the MOS tube Q6 is turned off immediately, the energy stored in the transformer T1 is transferred to the secondary coil, the MOS tube Q7 of the secondary coil is synchronously turned on, the power loss during energy conversion is reduced to the maximum extent, the output current of the dotted terminal of the secondary coil flows in the secondary coil of the transformer T1, charges are transferred to the whole battery pack until the current in the secondary coil is reduced to zero, once the current in the secondary coil reaches zero, the MOS tube Q7 is rapidly turned off, the MOS tube Q6 is turned back on at the same time, and the cycle is performed, so that charges are transferred from the batteries under discharge to all the batteries connected between the top end and the bottom end of the secondary coil Thereby charging the adjacent battery;

when the lithium battery monitoring module detects that the voltage of an individual battery is lower than the voltages of other batteries in the battery pack, a charging operation is performed, the MOS transistor Q7 of the secondary coil is turned on, the current flowing into the synonym terminal of the secondary coil of the transformer T1 flows through the entire battery pack, once the peak detection current is reached in the secondary coil, the MOS transistor Q7 of the secondary coil is turned off, similarly to the discharging case, the MOS transistor Q6 of the primary coil is turned on in synchronization, the current then flows in the primary coil, the selected battery can be charged from the entire secondary battery pack, once the current in the primary coil drops to zero, the MOS transistor Q6 of the primary coil is turned off, and the MOS transistor Q7 of the secondary coil is turned back on, thereby repeating;

the LTC6811-1 chip of the lithium battery monitoring module can detect the voltage of 12 batteries connected in series, and if the number of the monitored batteries needs to be increased, a daisy chain connection mode can be adopted; the LTC3300-1 chip of the balancing module can carry out bidirectional active balancing control on 6 series batteries based on a transformer, in order to realize detection of 12 batteries, two LTC3300-1 chips are used, wherein 43 pins (SDOI), 44 pins (SCKO) and 45 pins (CSBO) of the chips are used for daisy chain expansion connection and are connected with 18 pins, 17 pins and 16 pins of the LTC3300-1 chip at the upper stage of a daisy chain; the invention adopts the transformer to carry out balance control, the primary coil of the transformer is connected with a single battery in parallel, the secondary coil of the transformer is connected with the whole series battery pack in parallel, and when the voltage of a certain battery is detected to be abnormal, the on-off of an MOS (metal oxide semiconductor) tube in the voltage balancing circuit is controlled, so that the charge is transferred between the primary coil and the secondary coil, thereby realizing bidirectional active balance.

Through the design, the problem of high design cost of the existing battery equalization system is effectively solved, the bidirectional active balance between the battery pack and the individual battery is realized by adopting the special charge balancer LTC3300-1, the balance time is shortened, the charge transfer efficiency is improved, the integration level and the accuracy of the system are improved, the LTC6820 is directly communicated with the control module, the use amount of the isolator is reduced, and the design cost of the system is reduced; the invention is provided with the current detection module to detect the current when the battery is charged and discharged, thereby ensuring the normal work of the system and improving the reliability of the system.

The above-mentioned embodiment is only one of the preferred embodiments of the present invention, and should not be used to limit the scope of the present invention, but all the insubstantial modifications or changes made within the spirit and scope of the main design of the present invention, which still solve the technical problems consistent with the present invention, should be included in the scope of the present invention.

Claims

1. Two-way balanced electric automobile battery monitored control system of initiative based on PIC singlechip, its characterized in that includes:

the equalizing module adopts two LTC3300-1 chips, twelve groups of batteries are connected with the equalizing module through a peripheral circuit connected to the LTC3300-1 chips, and charge is efficiently transferred between the battery group and a single battery needing to be balanced through a voltage equalizing circuit connected with the LTC3300-1 chips;

two LTC3300-1 chips of the equalization module are connected in a daisy chain mode, the LTC3300-1 chip at the next stage of the daisy chain is U1, and the LTC3300-1 chip at the previous stage of the daisy chain is U2;

the voltage equalization circuit comprises a diode D14 with a cathode connected with a pin 30 of U2 and an anode connected with a pin 27 of U2, a capacitor C33 and a capacitor C34 with one ends connected with the cathode of the diode D14 and the other ends connected with the anode of the diode D14 after being connected in parallel, a zener diode D15 with a cathode connected with a pin 32 of U2 and an anode connected with a pin 27 of U2, a resistor R32 connected with a pin 32 of U2, a MOS tube Q6 with a gate connected with the other end of the resistor R32, a resistor R6 with one end connected with a pin 31 of U2 and the other end connected with a source of the MOS tube Q6, a capacitor C6 with one end connected with a pin 31 of U6 and the other end connected with a pin 27 of U6, a resistor R6 with one end connected with a source of the MOS tube Q6 and the other end connected with a pin 27 of U6 after being connected in series, and a capacitor C6 with a drain of the MOS tube Q6 and a drain of the cathode of the MOS tube Q6 connected with a drain of the resistor R6 and a drain of the cathode of the MOS tube Q6 after being connected in series connection with the cathode of the resistor R6, A zener diode D16 having an anode connected to the source of the MOS transistor Q6, a transformer T1 having a dotted terminal of a primary winding connected to the 30 pin of U2 and a dotted terminal connected to the drain of the MOS transistor, a capacitor C41 and a resistor R37 having a dotted terminal connected to the dotted terminal of the secondary winding of the transformer T1 and the other end connected to the dotted terminal of the secondary winding of the transformer T1 after being connected in series, a MOS transistor Q7 having a drain connected to the dotted terminal of the secondary winding of the transformer T1, a zener diode D17 having a cathode connected to the drain of the MOS transistor Q7 and an anode connected to the source of the MOS transistor Q7, a capacitor C44 and a capacitor C46 having a drain connected to the dotted terminal 39 of U2 and the other end connected to the pin 39 of U1 after being connected in parallel, a resistor 686r 9 having one end connected to the 7 pin of U2 and the other end connected to the gate of the MOS transistor Q7, a resistor R8653 having one end connected to the pin 8 pin of U2 and the other end connected to the source of the MOS transistor Q56, and a resistor R8653 connected to the pin 8439, A resistor R38 with the other end connected with the source electrode of the MOS transistor Q7, and a capacitor C43 with one end connected with the 8 pins of U2 and the other end connected with the 39 pins of U1.

2. The PIC single-chip microcomputer-based bidirectional active balancing electric vehicle battery monitoring system as claimed in claim 1, wherein the lithium battery monitoring module employs an LTC6811-1 chip U3.

3. The PIC single-chip microcomputer-based bidirectional active balancing electric vehicle battery monitoring system of claim 1, wherein the isolated communication module employs an isolated communication interface LTC6820 chip U4.

4. The PIC singlechip-based bidirectional active balancing electric vehicle battery monitoring system as claimed in claim 3, wherein the control module comprises a PIC18LF27K40 chip U5, a resistor R36 and a crystal oscillator Y1, which are connected in parallel and have one end connected with the 9 pin of U5 and the other end connected with the 10 pin of U5, a capacitor C38 having one end connected with the 9 pin of U5 and the other end grounded, a capacitor C40 having one end connected with the 10 pin of U5 and the other end grounded, a diode D18 having an anode connected with the 16 pin of U5, a resistor R41 having one end connected with the cathode of the diode D18 and the other end grounded, a diode D20 having an anode connected with the 17 pin of U5, a resistor R44 having one end connected with the cathode of the diode D20 and the other end grounded, a diode D19 having a cathode connected with the pin of U5, a triode Q8 having an emitter connected with the anode of the diode D19 and an emitter connected with the emitter of the Q8, The resistor R45 is connected with the cathode of the diode D19 at the other end, the resistor R46 is connected with the base of the triode Q8 at one end and the cathode of the diode D19 at the other end, the resistor R47 is connected with the collector of the triode Q8 at one end and the cathode of the diode D19 at the other end, the switch S1 and the capacitor C52 are connected in parallel, one end of the switch S1 is connected with the anode of the diode D19 and the other end of the switch S1 is grounded, the pin 7 of the U5 is connected with the pin 5 of the U4, the pin 14 of the U5 is connected with the pin 4 of the U4, the pin 15 of the U5 is connected with the pin 3 of the U4, and the pin 18 of the U5 is connected with the pin 2 of the U4.

5. The PIC singlechip-based bidirectional active balancing electric vehicle battery monitoring system as claimed in claim 4, wherein the current detection module comprises an AD7400A chip U6 and an RS722 chip U7, a capacitor C57 with one end connected to pin 1 of U6 and the other end grounded, a capacitor C60 with one end connected to pin 2 of U6 and the other end connected to pin 3 of U6, a resistor R75, a resistor R77 and a resistor R79 connected in series and connected in parallel with a capacitor C60, a capacitor C58 with one end connected to pin 14 of U6 and the other end connected to pin 16 of U6, a capacitor C7 with one end connected to pin 3 of U7 and the other end grounded, a capacitor C7 and a resistor R7 connected in series and with one end connected to pin 1 of U7 and the other end connected to pin 3 of U7, a resistor R7 with one end connected between the capacitor C7 and the resistor R7 and the other end connected to pin 11 of U7, and a resistor R7 connected to pin 1 of U7 and the other end connected to pin 7, after the series connection, one end of the capacitor C61 and the resistor R74 is connected with a pin 1 of the U7, the other end of the capacitor C61 and the resistor R74 is connected with a pin 7 of the U7, one end of the resistor R81 is connected with a pin 6 of the U7, one end of the resistor R76 is connected between the capacitor C61 and the resistor R74, the other end of the resistor R76 is connected with a pin 5 of the U7, one end of the capacitor C64 is connected with the pin 5 of the U7, the other end of the capacitor C4642 is connected with the pin 8 of the U7, the other end of the capacitor C59 is connected with the ground, the pin 7 of the U7 is connected with a pin 24 of the U5, the pin 8 of the U7 and a pin 14 of the U6 are both loaded with 5V voltage, one end of the resistor R77 and the resistor R79 are connected with the ground, and the resistor R77 and the resistor R75 are connected with the equalizing module.

6. The control method of the PIC single-chip microcomputer-based bidirectional active balancing electric vehicle battery monitoring system is characterized by comprising the following steps of:

7. The control method of the PIC single-chip microcomputer-based bidirectional active balancing electric vehicle battery monitoring system is characterized by comprising the following steps of: