CN114597994A - Equalizing circuit, charging circuit and vehicle-mounted charger - Google Patents
Equalizing circuit, charging circuit and vehicle-mounted charger Download PDFInfo
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- CN114597994A CN114597994A CN202210206395.5A CN202210206395A CN114597994A CN 114597994 A CN114597994 A CN 114597994A CN 202210206395 A CN202210206395 A CN 202210206395A CN 114597994 A CN114597994 A CN 114597994A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L53/00—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
- B60L53/20—Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles characterised by converters located in the vehicle
- B60L53/22—Constructional details or arrangements of charging converters specially adapted for charging electric vehicles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
- B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
- B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
- B60L58/18—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries of two or more battery modules
- B60L58/22—Balancing the charge of battery modules
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
- H02J7/0014—Circuits for equalisation of charge between batteries
- H02J7/0019—Circuits for equalisation of charge between batteries using switched or multiplexed charge circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2207/00—Indexing scheme relating to details of circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
- H02J2207/20—Charging or discharging characterised by the power electronics converter
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T90/00—Enabling technologies or technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02T90/10—Technologies relating to charging of electric vehicles
- Y02T90/14—Plug-in electric vehicles
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Transportation (AREA)
- Mechanical Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Sustainable Energy (AREA)
- Charge And Discharge Circuits For Batteries Or The Like (AREA)
Abstract
The invention discloses an equalizing circuit, a charging circuit and a vehicle-mounted charger. The equalizing circuit comprises an energy storage circuit, N switching circuits and a control circuit, wherein the input ends of the N switching circuits are correspondingly connected with the N battery modules one by one, and the output ends of the N switching circuits are connected with the energy storage circuit; the control circuit is respectively connected with the controlled ends of the N switch circuits and controls the switch circuits corresponding to the two adjacent battery modules to be alternately started so as to control the two adjacent battery modules to alternately charge and discharge the energy storage circuit; therefore, the voltage balance between the two battery modules is realized, and the voltage balance between the battery modules is realized.
Description
Technical Field
The invention relates to the technical field of power supplies, in particular to an equalizing circuit, a charging circuit and a vehicle-mounted charger.
Background
With the rapid development of electric automobiles, the requirements on power batteries of the electric automobiles are higher and higher, and the electric automobiles are safe, reliable and high in energy density. The whole battery pack of the electric vehicle generally comprises a plurality of battery modules.
Due to the difference of the characteristics of the batteries of the whole vehicle, the unbalance degree of the batteries is increased along with the prolonging of the service time in use, namely the unbalance degree between the battery modules is increased, so that the capacity of the whole battery pack is greatly reduced, and the risk in the aspect of safety is brought.
Disclosure of Invention
The invention mainly aims to provide an equalization circuit, aiming at realizing equalization among battery modules.
In order to achieve the above object, the present invention provides an equalizing circuit for equalizing N battery modules connected in series, including:
a tank circuit;
the N switching circuits are provided with input ends, output ends and controlled ends, the input ends of the N switching circuits are correspondingly connected with the N battery modules one by one, and the output ends of the N switching circuits are connected with the energy storage circuit;
the control circuit is used for controlling the switch circuits corresponding to the two adjacent battery modules to be alternately started so as to control the two adjacent battery modules to alternately charge and discharge the energy storage circuit;
wherein N is greater than or equal to 2.
In an embodiment, the control circuit is configured to sequentially control the switch circuits corresponding to two adjacent battery modules to be turned on alternately, so as to sequentially balance the N battery modules connected in series.
In an embodiment, the control circuit is an oscillator, and the oscillator is configured to oscillate to generate at least two mutually inverted PWM signals, so as to control the switching circuits corresponding to two adjacent battery modules to be alternately turned on;
or, the control circuit is a microcontroller, and the microcontroller is configured to output at least two mutually inverted PWM signals to control the switching circuits corresponding to the two adjacent battery modules to be alternately turned on.
In one embodiment, the duty cycle of the PWM signal is 50%.
The invention also provides a charging circuit comprising the equalizing circuit.
In one embodiment, the charging circuit is provided with a charging mode and an equalization mode; two adjacent battery modules are defined as a first battery module and a second battery module, and the second electrode of the first battery module is connected with the first electrode of the second battery module; the charging circuit includes:
the input end of the first switch circuit is connected with the first electrode of the first battery module, and the output end of the first switch circuit is connected with the first end of the energy storage circuit;
the input end of the second switch circuit is connected with the second end of the energy storage circuit, and the output end of the second switch circuit is connected with the second electrode of the second battery module;
the input end of the function change-over switch is connected with the second end of the energy storage circuit, and the output end of the function change-over switch is connected with the common end of the first battery module and the second battery module;
the function switch is used for being conducted when the charging circuit works in an equalization mode, so that the first switch circuit, the second switch circuit and the energy storage circuit form an equalization circuit; and the circuit is cut off when the charging circuit works and in a charging mode, so that the first switch circuit and the second switch circuit form a secondary side bridge arm of the charging circuit.
In an embodiment, the controlling the switching circuits corresponding to two adjacent battery modules to be alternately turned on specifically includes:
controlling the frequency of the alternative opening of the switch circuits corresponding to the two adjacent battery modules to be a first preset frequency;
when the bus voltage reaches a preset voltage value, controlling the frequency of the alternate turning-on of the switch circuits corresponding to two adjacent battery modules to be reduced step by step until the frequency of the alternate turning-on of the switch circuits corresponding to two adjacent battery modules is a second preset frequency; the first preset frequency is greater than the second preset frequency.
In an embodiment, the controlling the switching circuits corresponding to two adjacent battery modules to be alternately turned on specifically includes:
controlling the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started to be a first preset frequency, and after the first preset time is continued, controlling the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started to be gradually reduced until the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started is a second preset frequency; the first preset frequency is greater than the second preset frequency.
In one embodiment, the charging circuit comprises a primary side bridge arm, a resonant cavity and a secondary side bridge arm which are connected in sequence;
the energy storage circuit is a secondary winding of a transformer in the resonant cavity.
The invention further provides a vehicle-mounted charger which comprises the equalizing circuit or the charging circuit.
According to the technical scheme, the N switch circuits are controlled through the control circuit, so that the switch circuits corresponding to the two adjacent battery modules are controlled to be alternately started, the two adjacent battery modules are controlled to alternately charge and discharge the energy storage circuit, the voltages of the two battery modules are finally balanced, and the service life of the battery module is effectively prolonged.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a block diagram of an embodiment of an equalizer circuit according to the present invention;
FIG. 2 is a circuit diagram of an equalizing circuit according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of a charging circuit according to an embodiment of the present invention;
FIG. 4 is a waveform diagram of a key node of a charging circuit according to an embodiment of the present invention.
The reference numbers illustrate:
the implementation, functional features and advantages of the present invention will be further described with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In addition, descriptions such as "first", "second", etc. in the present invention are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The invention provides an equalizing circuit which is used for equalizing N battery modules which are sequentially connected in series. The method can be applied to full-bridge converters such as LLC, CLLC, CLLLC and PSFB.
Referring to fig. 1, in an embodiment of the present invention, the equalizing circuit includes
A tank circuit 10;
the N switching circuits are provided with input ends, output ends and controlled ends, the input ends of the N switching circuits are correspondingly connected with the N battery modules one by one, and the output ends of the N switching circuits are connected with the energy storage circuit 10;
the control circuit is respectively connected with the controlled ends of the N switch circuits, and is used for controlling the switch circuits corresponding to the two adjacent battery modules to be alternately started so as to control the two adjacent battery modules to alternately charge and discharge the energy storage circuit 10;
wherein N is greater than or equal to 2.
The energy storage circuit 10 may include an inductor, a capacitor, or other energy storage elements.
Any one or more of the N switching circuits may include one or more combinations of switching devices such as a transistor, a MOS transistor, or an IGBT.
The control circuit (not shown in the figures) may be a controller, an oscillator, or other circuits capable of generating a PWM signal, which is not limited herein, as long as the output PWM signal is satisfied to control the on and off of the switching circuit, wherein the duty ratio of the PWM signal is 50%.
The controlling of the two adjacent battery modules to alternately charge and discharge the energy storage circuit 10 may mean that one of the switch circuits corresponding to the two adjacent battery modules is used to control the corresponding battery module to discharge the energy storage circuit 10, and the other is used to control the corresponding battery module to charge the energy storage circuit 10. For example, in fig. 1, two adjacent battery modules are a first battery module BT1 and a second battery module BT2, respectively, and the initial value of the voltage V _ BT1 of the first battery module BT1 is greater than the initial value of the voltage V _ BT2 of the second battery module BT2, for example, the first switch circuit K1 controls the first battery module BT1 to discharge the energy storage circuit 1010 periodically, and the second switch circuit K2 controls the second battery module BT2 to charge the energy storage circuit 1010 periodically.
As the first battery module BT1 and the second battery module BT2 charge and discharge the energy storage circuit 1010, the voltage V _ BT1 of the first battery module BT1 is gradually decreased, the voltage V _ BT2 of the second battery module BT2 is gradually increased, and finally, the voltage equalization between the first battery module BT1 and the second battery module BT2 is realized. It is understood that, when N is greater than 2, that is, the number of battery modules exceeds two, after the voltage between the first battery module BT1 and the second battery module BT2 is equalized, the voltage between the other two battery modules, for example, the second battery module BT2 and the third electronic module BT3 (not shown in the figure) may be equalized, and finally, the voltage equalization between two of the N battery modules is performed, so that the voltage equalization between the N battery modules is performed.
According to the technical scheme, the N switch circuits are controlled through the control circuit, so that the switch circuits corresponding to the two adjacent battery modules are controlled to be alternately started, the two adjacent battery modules are further controlled to alternately charge and discharge the energy storage circuit 10, the voltages of the two battery modules are finally balanced, and the service life of the battery module is effectively prolonged.
For example, referring to fig. 2, an explanation is made with respect to two adjacent first and second battery modules BT1 and BT2, and their corresponding first and second switch circuits K1 and K2. The energy storage circuit 10 includes a first inductor L1, the first switch circuit K1 includes a first switch tube Q1, and the second switch circuit K2 includes a second switch tube Q2. The control signals of the first switching tube Q1 and the second switching tube Q2 are two mutually-inverted PWM signals with a duty ratio of 50%, for example, refer to PWM1 and PWM2 of fig. 4. The explanation is still given taking an example in which the initial value of the voltage V _ BT1 of the first battery module BT1 is greater than the initial value of the voltage V _ BT2 of the second battery module BT 2.
When the first switching tube Q1 is turned on, the second switching tube Q2 is turned off, and the first battery module BT1 charges the first inductor L1; when the second switching tube Q2 is turned on, the first switching tube Q1 is turned off, the first inductor L1 discharges the battery module BT2, and the first inductor is alternately charged and discharged by controlling the first switching tube Q1 and the second switching tube Q2 to be alternately turned on for multiple times, so that the voltage V _ BT1 of the first battery module BT1 and the voltage V _ BT2 of the second battery module BT2 are balanced.
In an embodiment, the control circuit is configured to sequentially control the switch circuits corresponding to two adjacent battery modules to be turned on alternately, so as to sequentially balance the N battery modules connected in series.
Referring to fig. 1, first battery modules BT1 to nth battery modules BTn are sequentially connected in series, and after voltage equalization between first battery module BT1 and second battery module BT2 is achieved, voltage equalization between second battery module BT2 and third battery module BT3 is performed until voltage equalization between N-1 battery module BTn-1 and nth battery module BTn is performed, and equalization of N battery modules is achieved by continuously equalizing two adjacent battery modules between the N battery modules.
In an embodiment, the control circuit is an oscillator, and the oscillator is configured to oscillate to generate at least two mutually inverted PWM signals, so as to control the switching circuits corresponding to two adjacent battery modules to be alternately turned on;
referring to fig. 1, the present embodiment generates control signals of a first switching circuit K1 and a second switching circuit K2, i.e., two mutually inverted PWM signals, such as PWM1 and PWM2 shown in fig. 4, by using an oscillator control circuit. The control logic is simple, when the equalizing circuit of the embodiment is applied to the charging circuit or other circuits, controller resources of the charging circuit or other circuits applying the equalizing circuit are not occupied, and further the charging circuit or other circuits applying the equalizing circuit are not required to be adjusted.
In an embodiment, the control circuit is a microcontroller, and the microcontroller is configured to output at least two mutually inverted PWM signals to control the switching circuits corresponding to the two adjacent battery modules to be alternately turned on.
In this embodiment, the microcontroller may be a microcontroller that is independently configured, and may be further directly applicable to a charging circuit or other circuits that have been designed after the test.
The microcontroller can also be a charging circuit applying the equalizing circuit or a controller in other circuits, so that the equalization can be realized only by adjusting software control programs of the charging circuit applying the equalizing circuit or the controllers in other circuits, and the increase of devices can be reduced. In addition, in this embodiment, the charging circuit or the controller in another circuit to which the equalizing circuit is applied is configured to output at least two mutually inverted PWM signals, and only the PWM signals need to be output in an open loop without a feedback signal, and the equalizing circuit may also be directly applied to the charging circuit or another circuit that has been already designed, and the resource occupation of the charging circuit or the controller in another circuit to which the equalizing circuit is applied is reduced.
In an embodiment, the present invention further includes a charging circuit, which includes the above equalizing circuit; the specific structure of the charging circuit refers to the above embodiments, and since the charging circuit adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.
It should be noted that the entire Battery pack of the electric vehicle generally includes a plurality of Battery modules, each Battery module is formed by combining a single Battery cell in series and parallel to balance the Battery cells in the Battery module, which is generally completed by a Battery Management System (BMS), and the balance power is generally varied from several watts to several tens of watts. The power required for balancing the battery modules is relatively large, generally from hundreds of watts to tens of kilowatts, so that more powerful energy conversion equipment needs to be designed, and a better heat dissipation assembly is used for completing the balancing, which undoubtedly increases the volume and heat dissipation requirements of the BMS.
This embodiment is through setting up equalizer circuit on charging circuit, and this equalizer circuit can carry out voltage balance to battery module at the time quantum that charging circuit does not carry out the battery module and charge, make full use of's charging circuit self radiator unit to when not increasing BMS's volume and heat dissipation demand, realized voltage balance between the battery module, had very big practical value.
Referring to fig. 3, in one embodiment, the charging circuit has a charging mode and an equalization mode; two adjacent battery modules are defined as a first battery module BT1 and a second battery module BT2, the second electrode of the first battery module BT1 is connected with the first electrode of the second battery module BT 2; the charging circuit includes:
a first switch circuit K1, an input terminal of the first switch circuit K1 being connected to the first electrode of the first battery module BT1, an output terminal of the first switch circuit K1 being connected to the first terminal of the energy storage circuit 10;
a second switch circuit K2, an input terminal of the second switch circuit K2 is connected to the second terminal of the energy storage circuit 10, and an output terminal of the second switch circuit K2 is connected to the second electrode of the second battery module BT 2;
a function switcher 20, an input terminal of the function switcher 20 being connected to the second terminal of the energy storage circuit 10, and an output terminal of the function switcher 20 being connected to a common terminal of the first battery module BT1 and the second battery module BT 2;
the function switch 20 is configured to be turned on when the charging circuit operates in an equalization mode, so that the first switch circuit K1, the second switch circuit K2 and the energy storage circuit 10 form an equalization circuit; and the circuit is turned off when the charging circuit works and in a charging mode, so that the first switch circuit K1 and the second switch circuit K2 form a secondary side bridge arm of the charging circuit.
In this embodiment, the first electrode of the battery module may be a positive electrode, and the second electrode may be a negative electrode. The charging circuit comprises a primary side bridge arm, a resonant cavity and a secondary side bridge arm which are connected in sequence.
The primary bridge arm may include a third switching tube Q3, a fourth switching tube Q4, a fifth switching tube Q5, and a sixth switching tube Q6, the resonant cavity may include a resonant cavity composed of a secondary resonant capacitor Cs, a primary resonant capacitor Cr, and a primary resonant inductor Lr, the secondary bridge arm may include a seventh switching tube Q7, an eighth switching tube Q8, a ninth switching tube Q9, and a tenth switching tube Q10, and specific connection relationships among the primary bridge arm, the resonant cavity, and the secondary bridge arm refer to fig. 3, which is not described herein again. In addition, the input end of the primary side bridge arm is connected with a bus capacitor C1, and the output end of the secondary side bridge arm is connected with an output capacitor C2.
The first switch circuit K1 and the second switch circuit K2 may correspond to the seventh switch tube Q7 and the eighth switch tube Q8 in the secondary arm, or the first switch circuit K1 and the second switch circuit K2 may correspond to the ninth switch tube Q9 and the tenth switch tube Q10 in the secondary arm. The function switch 20 may be one or more of a transistor, a MOS transistor, an IGBT, or a relay.
When the battery modules need to be charged, the controller of the charging circuit can control the function switch 20 to be turned off, and the charging circuit converts the energy in the direct current bus Vbus and outputs the converted energy to charge the N battery modules which are sequentially connected in series.
When the voltage of the battery module needs to be equalized, the controller of the charging circuit may control the function switch 20 to be turned on, and the secondary winding of the transformer T1 in the resonant cavity is used as the energy storage circuit 10. At this time, voltage balance between the first battery module BT1 and the second battery module BT2 can be realized only by outputting two mutually opposite PWM signals to the first switch circuit K1 and the second switch circuit K2. In the embodiment, the secondary side bridge arm in the charging circuit is multiplexed, so that the equalizing circuit can be added on the basis of the charging circuit only by adding the function change-over switch 20, for example, by adding one relay.
In addition, it is easy to understand that the whole vehicle battery pack of the electric vehicle generally comprises 2 battery modules, and two switching tubes of one secondary bridge arm are directly multiplexed in sequence, so that voltage equalization can be performed on the 2 battery modules, and when the whole vehicle battery pack of the electric vehicle comprises more than 2 battery modules, only the switching tubes with corresponding quantity need to be added, which is not described herein again.
The following explains the principle of the charging circuit in the present embodiment,
assume that the initial value of the voltage V _ BT1 of the first battery module BT1 is greater than the initial value of the voltage V _ BT2 of the second battery module BT 2; the first switch circuit K1 and the second switch circuit K2 may correspond to the ninth switch tube Q9 and the tenth switch tube Q10 in the secondary bridge arm, and the control signals of the first switch circuit K1 and the second switch circuit K2 are two PWM signals PWM1 and PWM2 with a duty ratio D of 50% and a frequency f of 150kHz, where PWM1 is a control signal of the first switch circuit K1, and PWM is a control signal of the second switch current.
In the first half period of the PWM signal, the ninth switching tube Q9 is turned on, the tenth switching tube Q10Q8 is turned off, the first battery module BT1 charges the secondary winding of the transformer T1, in the second half period of the PWM signal, the ninth switching tube Q9Q7 is turned off, the tenth switching tube Q10 is turned on, and the secondary winding of the transformer T1 charges the second battery module BT 2.
In the process that the first battery module BT1 charges the secondary winding of the transformer T1, energy is transferred to the primary winding of the transformer T1 in a coupling mode of the primary winding and the secondary winding of the transformer T1, the bus capacitor C1 is charged, and meanwhile, due to the fact that charging and discharging voltages of the secondary winding are not equal (V _ BT1> V _ BT2), charging currents of a positive half period and a secondary half period of the primary winding are not equal, a direct current bias voltage Vcr is generated on the primary resonant capacitor, and the positive half period and the negative half period of the voltage superposed on the secondary winding of the transformer T1 are exactly equal after the direct current bias voltage Vcr is converted through the primary turn ratio and the secondary turn ratio of the transformer T1. Since the positive and negative half-cycle times are equal, the voltage-second balance of the positive and negative half-cycles is maintained in the secondary winding, and iL is the current of the secondary winding of the transformer T1, see fig. 4. Therefore, the secondary winding of the transformer T1 is selected to serve as the energy storage circuit 10, so that the technical effect that the magnetic core of the transformer T1 is not saturated even if the equalizing circuit works for a long time can be achieved, and the problem of magnetic core saturation of the energy storage circuit 10 caused by the fact that the charging voltage of the energy storage circuit 10 is greater than the discharging voltage is effectively solved.
Specifically, the equalization circuit steady state expression is as follows:
Vcr/N＝V_BT1-(V_BT1+V_BT2)/2
or: Vcr/N ═ V _ BT1+ V _ BT2)/2-V _ BT2
Wherein, Vcr is the DC bias voltage on the primary resonant capacitor Cr, and N is the primary and secondary turns ratio of the transformer T1. With particular reference to fig. 4, as the equalizing operation continues, the voltage V _ BT1 of the first battery module BT1 gradually decreases, the voltage V _ BT2 of the second battery module BT1 gradually increases, the difference between the voltage V _ BT1 of the first battery module BT1 and the voltage V _ BT2 of the battery module BT1 becomes smaller and smaller, and thus the second dc bias voltage Vcr also gradually decreases until the voltage V _ BT1 of the first battery module BT1 is equal to the voltage V _ BT2 of the second battery module BT 1. Meanwhile, the direct current bias voltage Vcr is equal to zero, and only alternating current voltage which changes along with the period is left on Cr.
In an embodiment, the controlling the switching circuits corresponding to two adjacent battery modules to be alternately turned on specifically includes:
controlling the frequency of the alternate opening of the switch circuits corresponding to the two adjacent battery modules to be a first preset frequency;
after the bus voltage reaches a preset voltage value, controlling the frequency of the alternate turning-on of the switch circuits corresponding to two adjacent battery modules to be reduced step by step until the frequency of the alternate turning-on of the switch circuits corresponding to two adjacent battery modules is a second preset frequency; the first preset frequency is greater than the second preset frequency.
The preset voltage value may be a stable voltage value of the bus voltage. The preset voltage value may be set to 150 volts, for example, when the charging circuit is applied to an on-board charger. The second predetermined frequency may be an operating frequency of the equalization circuit, specifically selected according to an operating power of the equalization circuit, for example 150 HZ. The first preset frequency may be 2 to three times the operating frequency of the equalization circuit, for example 400 HZ.
It can be understood that, in this embodiment, by controlling the frequency of the alternate turn-on of the switch circuits corresponding to two adjacent battery modules to be the first preset frequency, the problem that the magnetic core of the transformer T1 is saturated due to the excessive bus current when the equalizing circuit is started can be avoided.
Specifically, at the moment of starting the equalization circuit, the primary winding, the primary resonant inductor Lr, the primary resonant capacitor, and the bus capacitor C1 form a loop, and at this time, the voltage of the bus capacitor C1 is zero, which is equivalent to a short circuit state. Therefore, at the start of the equalization circuit, the charging current coupled to the bus capacitor C1 through the transformer T1 will be large, which in turn will cause the core of the transformer T1 to saturate.
The specific formula is as follows: l di/dt ═ Vbat
Namely: l Imax/DT-Vbat
Namely: imax (Vbat DT/L)
Wherein, L is inductance of the secondary winding of the transformer T1, Vbat is charging voltage for charging the secondary winding of the transformer by the battery module, D and T are duty ratio and period of the control signal of the first switch circuit K1, Imax is maximum current value of the secondary winding of the transformer T1, and i is current of the secondary winding of the transformer T1. It is understood that D is 0.5, Vbat may be the average voltage of the first battery module and the second battery module, and is also a constant value, so Imax is proportional to T. Therefore, the present embodiment increases the frequency (reciprocal of the period T) when the equalizing circuit is started, can reduce Imax when the equalizing circuit is started, and solves the problem that the charging current of the transformer T1 coupled to the bus capacitor C1 is relatively large due to the short circuit caused by the zero voltage of the bus capacitor C1, which leads to saturation of the magnetic core of the transformer T1.
In addition, in this embodiment, a suitable second preset frequency is selected, so that the magnitude of the equalizing power of the equalizing circuit can be effectively adjusted, specifically as follows:
L*di/dt＝Vbat；Vbat＝(V_BT1+V_BT2)/2；di＝Vbat*dt/L
wherein, L is inductance of a secondary winding of the transformer T1, V _ BT1 and V _ BT2 are voltage values of the first battery module and the second battery module respectively, and two sides of the above formula are respectively integrated with time from 0 to T/2;
the following formula is obtained: imax ═ Vbat DT/L;
at this time, the equalizing power of the equalizing circuit:
p _ balance ═ Vbat ═ Imax ═ 1/2 ═ Vbat ═ DT/L ═ 1/2;
as can be seen from the above, the equalizing power can be controlled by controlling T, i.e., controlling the operating frequency f. Therefore, the embodiment can effectively adjust the equalizing power of the equalizing circuit by adjusting the operating frequency of the equalizing circuit.
Referring to fig. 3, in an embodiment, the controlling the switch circuits corresponding to two adjacent battery modules to be alternately turned on specifically includes:
controlling the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started to be a first preset frequency, and after the first preset time is continued, controlling the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started to be gradually reduced until the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started is a second preset frequency; the first preset frequency is greater than the second preset frequency.
The first preset time may be set according to an actual test result, for example, set to 300 milliseconds.
In this embodiment, the frequency of the alternate turn-on of the switch circuits corresponding to the two adjacent battery modules is controlled to be a first preset frequency, and after the first preset time is continued. The default bus voltage reaches a preset voltage value. Therefore, the control circuit of the equalizing circuit does not need to monitor the bus voltage, and only needs to adjust the frequency of the two paths of output PWM signals in opposite phase to each other when the timing reaches the first preset time in an open-loop manner, so that the resource occupation of the controller of the charging circuit is effectively reduced.
The invention also provides a vehicle-mounted charger which comprises the equalizing circuit or the charging circuit; the specific structure of the equalizing circuit or the charging circuit refers to the above embodiments, and since the charging circuit adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.
The above description is only an alternative embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. An equalizing circuit for equalizing a plurality of N battery modules connected in series, comprising:
a tank circuit;
the N switching circuits are provided with input ends, output ends and controlled ends, the input ends of the N switching circuits are correspondingly connected with the N battery modules one by one, and the output ends of the N switching circuits are connected with the energy storage circuit;
the control circuit is used for controlling the switch circuits corresponding to the two adjacent battery modules to be alternately started so as to control the two adjacent battery modules to alternately charge and discharge the energy storage circuit;
wherein N is greater than or equal to 2.
2. The equalizing circuit according to claim 1, wherein the control circuit is configured to sequentially control the switching circuits corresponding to two adjacent battery modules to be turned on alternately so as to sequentially equalize the N battery modules connected in series.
3. The equalizing circuit according to claim 1, wherein the control circuit is an oscillator, and the oscillator is configured to oscillate and generate at least two mutually inverted PWM signals to control the switching circuits corresponding to two adjacent battery modules to be alternately turned on;
or, the control circuit is a microcontroller, and the microcontroller is configured to output at least two mutually inverted PWM signals to control the switching circuits corresponding to the two adjacent battery modules to be alternately turned on.
4. The equalizing circuit of claim 3, wherein the duty cycle of the PWM signal is 50%.
5. A charging circuit comprising an equalizing circuit as claimed in any one of claims 1 to 4.
6. The charging circuit of claim 5, wherein the charging circuit is provided with a charging mode and an equalization mode; two adjacent battery modules are defined as a first battery module and a second battery module, and the second electrode of the first battery module is connected with the first electrode of the second battery module; the charging circuit includes:
the input end of the first switch circuit is connected with the first electrode of the first battery module, and the output end of the first switch circuit is connected with the first end of the energy storage circuit;
the input end of the second switch circuit is connected with the second end of the energy storage circuit, and the output end of the second switch circuit is connected with the second electrode of the second battery module;
the input end of the function change-over switch is connected with the second end of the energy storage circuit, and the output end of the function change-over switch is connected with the common end of the first battery module and the second battery module;
the function switch is used for being conducted when the charging circuit works in an equalization mode, so that the first switch circuit, the second switch circuit and the energy storage circuit form an equalization circuit; and the circuit is cut off when the charging circuit works and in a charging mode, so that the first switch circuit and the second switch circuit form a secondary side bridge arm of the charging circuit.
7. The equalizing circuit according to claim 5, wherein said controlling the switching circuits corresponding to two adjacent battery modules to be alternately turned on is specifically:
controlling the frequency of the alternative opening of the switch circuits corresponding to the two adjacent battery modules to be a first preset frequency;
when the bus voltage reaches a preset voltage value, controlling the frequency of the alternate turning-on of the switch circuits corresponding to two adjacent battery modules to be reduced step by step until the frequency of the alternate turning-on of the switch circuits corresponding to two adjacent battery modules is a second preset frequency; the first preset frequency is greater than the second preset frequency.
8. The equalizing circuit according to claim 5, wherein the controlling of the switching circuits corresponding to two adjacent battery modules to be alternately turned on is specifically:
controlling the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started to be a first preset frequency, and after the first preset time is continued, controlling the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started to be gradually reduced until the frequency of the switch circuits corresponding to the two adjacent battery modules to be alternately started is a second preset frequency; the first preset frequency is greater than the second preset frequency.
9. The charging circuit of claim 7, wherein the charging circuit comprises a primary side bridge arm, a resonant cavity, and a secondary side bridge arm connected in sequence;
the energy storage circuit is a secondary winding of a transformer in the resonant cavity.
10. A vehicle-mounted charger, characterized in that the vehicle-mounted charger comprises an equalizing circuit according to any one of claims 1 to 4, or a charging circuit according to any one of claims 5 to 9.
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| CN202210206395.5A CN114597994A (en) | 2022-03-03 | 2022-03-03 | Equalizing circuit, charging circuit and vehicle-mounted charger |
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| CN202210206395.5A CN114597994A (en) | 2022-03-03 | 2022-03-03 | Equalizing circuit, charging circuit and vehicle-mounted charger |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118182212A (en) * | 2024-05-10 | 2024-06-14 | 宜宾宜行汽车科技有限公司 | Charging pile energy control method and system |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118182212A (en) * | 2024-05-10 | 2024-06-14 | 宜宾宜行汽车科技有限公司 | Charging pile energy control method and system |
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