CN113002303A - Pre-charging circuit and pre-charging method, bidirectional direct current converter and electric automobile - Google Patents

Pre-charging circuit and pre-charging method, bidirectional direct current converter and electric automobile Download PDF

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CN113002303A
CN113002303A CN201911320544.5A CN201911320544A CN113002303A CN 113002303 A CN113002303 A CN 113002303A CN 201911320544 A CN201911320544 A CN 201911320544A CN 113002303 A CN113002303 A CN 113002303A
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charging
voltage
converter
current
bidirectional
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CN113002303B (en
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甘宜洋
王小昆
崔永生
王伟
梁东
沙孟轲
张哲亮
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United Automotive Electronic Systems Co Ltd
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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
    • B60L3/00—Electric devices on electrically-propelled vehicles for safety purposes; Monitoring operating variables, e.g. speed, deceleration or energy consumption
    • B60L3/0023—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train
    • B60L3/003—Detecting, eliminating, remedying or compensating for drive train abnormalities, e.g. failures within the drive train relating to inverters
    • 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
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

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  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Power Engineering (AREA)
  • Transportation (AREA)
  • Mechanical Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention provides a pre-charging circuit, a pre-charging method, a bidirectional direct current converter and an electric automobile. The pre-charging circuit adopts a double ring of a current ring and a voltage ring to modulate the charging current in the pre-charging process, can reduce or avoid surge current, can solve the problem of relative lag existing in the process of only responding to current fluctuation through voltage, and improves the precision of output voltage. The pre-charging method utilizes the pre-charging circuit to pre-charge and adds a charging diagnosis stage before rapid charging, so that abnormal working conditions such as load short circuit and the like can be diagnosed, risks can be identified in advance, and the charging time can be controlled well. The bidirectional direct current converter comprises the pre-charging circuit, so that the capacitor, particularly the parasitic capacitor on the high-voltage side, in the bidirectional direct current converter is pre-charged before direct current conversion, and the stability and the control accuracy of the charging current and the output voltage are improved. The electric automobile comprises the bidirectional direct current converter.

Description

Pre-charging circuit and pre-charging method, bidirectional direct current converter and electric automobile
Technical Field
The invention relates to the field of circuits, in particular to a pre-charging circuit, a pre-charging method, a bidirectional direct current converter and an electric automobile.
Background
In order to respond to the national call of energy conservation and emission reduction, the energy utilization rate of the automobile is improved, and CO is reduced2On the basis of the traditional automobile, the hybrid electric automobile solves the problem of CO starting of the traditional automobile by arranging a high-voltage grade battery (such as a 48V battery) and a motor and the like2Excessive emission, high energy consumption and the like. The battery placed in the hybrid electric vehicle can be used for energy recovery and power-assisted starting, and the energy conversion of the high-voltage grade battery and the low-voltage grade battery (such as a 12V battery) realizes high-efficiency energy utilization. Generally, energy transfer between a 48V battery and a 12V battery requires a DC-to-DC (or bidirectional DC) converter. Fig. 1 is a schematic diagram of the operation of a bidirectional dc converter. In the motor system, because a large parasitic capacitor C (usually in the mF level) is included, in the initial working stage of the converter, if the relay switch is directly turned on under the condition that no voltage exists on the capacitor, surge current is generated, so that the capacitor in the motor system needs to be pre-charged first to prevent related devices from being damaged.
Chinese patent application CN107294366A discloses a pre-charging circuit implemented based on a mirror current source and a flyback circuit by controlling the voltage U between the base and emitter of a triodebeThe current limitation is realized, the corresponding resistance can be adjusted to obtain the corresponding current value, and meanwhile, negative feedback is introduced to adjust the change of the output current. Although negative feedback is introduced to adjust the output current change, the voltage is utilized to respond to the current change more slowly on one hand, and the base electrode voltage U and the emitter electrode voltage U of the triode are influenced by individual difference and temperature on the other handbeIs not a fixed value, and causes load disturbance, heavy load and load when current changesWhen short circuit occurs, the scheme has no quick dynamic response capability and low control voltage precision.
In summary, the bidirectional dc pre-charging circuit scheme in the prior art still has the problems of low voltage control accuracy and large influence of operating temperature.
Disclosure of Invention
The invention provides a pre-charging circuit of a bidirectional direct current converter, which can realize the accurate control of charging current and charging voltage and effectively solve the problems of low voltage control accuracy and large influence of working temperature. The invention further provides a pre-charging method of the bidirectional direct current converter by using the pre-charging circuit, a bidirectional direct current converter and an electric vehicle comprising the bidirectional direct current converter.
According to a first aspect of the present invention, a pre-charging circuit of a bidirectional dc converter is provided, configured to pre-charge a capacitor in the bidirectional dc converter before dc conversion is performed, where the pre-charging circuit includes a main circuit module, a current sampling module, a current loop control module, a voltage feedback module, and a voltage loop control module. The main circuit module is used for providing a charging current for the capacitor; the current sampling module is used for sampling the charging current of the capacitor; the current loop control module is electrically connected with the current sampling module and is used for modulating the charging current by using a current loop; the voltage feedback module is used for acquiring the voltage on the capacitor; and the voltage ring control module is electrically connected with the voltage feedback module and is used for modulating the charging current by using a voltage ring.
Optionally, the pre-charge circuit further includes a PWM control module and a driving module, the PWM control module is configured to adjust a PWM duty ratio according to outputs of the current loop control module and the voltage loop control module, and the driving module is configured to control a switching element in the main circuit module according to a signal of the PWM duty ratio to adjust the magnitude of the charging current.
Optionally, the switching element is a safety protection switch of the bidirectional dc converter.
Optionally, the current loop control module and the voltage loop control module modulate the average value or the peak value of the charging current.
According to a second aspect of the present invention, there is provided a pre-charging method for a bidirectional dc converter, the pre-charging method is used to pre-charge a capacitor in the bidirectional dc converter before dc conversion is performed, and the pre-charging method includes a charging diagnosis step, wherein the pre-charging circuit is used to pre-charge the capacitor in the bidirectional dc converter with a first charging current, and detect whether a voltage across the capacitor reaches a threshold voltage within a preset time, if the voltage does not reach the threshold voltage, the operating condition of the bidirectional dc converter is diagnosed, and if the threshold voltage is reached, the pre-charging circuit is used to pre-charge the capacitor in the bidirectional dc converter with a second charging current until a set voltage is reached, and the second charging current is greater than the first charging current.
According to a third aspect of the present invention, there is provided a bidirectional dc converter for performing dc conversion between a first power supply and a second power supply, negative electrodes of the first power supply and the second power supply being grounded, the bidirectional dc converter comprising a first capacitor, a second capacitor, a conversion circuit, a safety protection switch, and the above-mentioned precharge circuit; the first capacitor is connected between a port of the first power supply and ground; the second capacitor is connected between a port of the second power supply and ground; the conversion circuit is configured between the first power supply and the second power supply; the safety protection switch is connected with the first port; the pre-charging circuit is used for pre-charging the first capacitor and the second capacitor before direct current conversion.
Optionally, the first power supply is a low-voltage power supply, the second power supply is a high-voltage power supply, and the second capacitor is a high-voltage side parasitic capacitor.
Optionally, the voltage feedback module of the pre-charge circuit is electrically connected to the other end of the second capacitor outside the ground end to obtain the voltage on the second capacitor.
Optionally, the low-voltage power supply is a 12V power supply system, and the high-voltage power supply is a 48V or 400V power supply system.
Optionally, the main circuit module of the pre-charge circuit includes a first sampling resistor, a diode, a first power inductor, and the safety protection switch, wherein the first sampling resistor, the first power inductor, and the safety protection switch are connected in series to the other end of the first capacitor outside the ground terminal, the current sampling module is electrically connected to the first sampling resistor, and the diode is connected between a node between the first power inductor and the safety protection switch and the ground.
Optionally, when the bidirectional dc converter performs dc conversion, the first power inductor is used as an EMC filter inductor.
Optionally, when the bidirectional dc converter performs dc conversion, a current loop control module of the pre-charge circuit is applied to perform current control, overload protection or short-circuit protection.
Optionally, the conversion circuit includes a synchronous rectification circuit.
According to a third aspect of the present invention, there is provided an electric vehicle equipped with the above-described bidirectional dc converter.
The invention provides a pre-charging circuit of a bidirectional direct current converter, which comprises a main circuit module, a current sampling module, a current loop control module, a voltage feedback module and a voltage loop control module, namely, a double loop formed by a current loop and a voltage loop is adopted to modulate pre-charged charging current, and the pre-charging circuit has the following technical effects: firstly, the pre-charging problem of capacitor voltage in the bidirectional direct current converter can be effectively realized, the surge current is reduced, and the service life of the system is prolonged; secondly, by utilizing a current-voltage double closed-loop system, the problem of relative lag existing in the process of responding to current fluctuation only through voltage can be solved, the precision of output voltage is improved, meanwhile, the problem of load jump can be effectively solved, and the stability of the output voltage is ensured; and thirdly, the pre-charging circuit can effectively reduce the voltage fluctuation in the charging process by utilizing double-loop control, so that the voltage control precision is higher, the influence of temperature factors is smaller, and the applicable environment temperature is wider.
The pre-charging method of the bidirectional direct current converter comprises a charging diagnosis step, wherein a capacitor in the bidirectional direct current converter is pre-charged by using the pre-charging circuit with a small first charging current, whether the voltage on the capacitor reaches a threshold voltage or not is detected within a preset time, if the voltage does not reach the threshold voltage, the working condition of the bidirectional direct current converter is diagnosed, and if the voltage reaches the threshold voltage, the capacitor in the bidirectional direct current converter is pre-charged by using a large second charging current until a set voltage is obtained. The pre-charging method divides the pre-charging process into a charging diagnosis stage and a quick charging stage, on one hand, abnormal working conditions such as load short circuit and the like can be diagnosed in the charging diagnosis stage, the phenomena such as abnormal working of each element and the like in the pre-charging process are avoided, risks are identified in advance, and on the other hand, the charging time can be controlled well, and the charging efficiency can be improved.
The bidirectional direct current converter provided by the invention comprises the pre-charging circuit to pre-charge the first capacitor and the second capacitor before direct current conversion, so that the stability and the control accuracy of charging current and output voltage can be improved. The safety protection switch of the bidirectional direct current converter can be used in the pre-charging circuit to adjust the magnitude of the charging current, the power inductor of the pre-charging circuit can be used as an EMC filter inductor of the bidirectional direct current converter during direct current conversion, and a current loop control module of the pre-charging circuit can be used for current control, overload or short circuit protection when the bidirectional direct current converter performs direct current conversion, so that the function multiplexing of various element circuits can be realized, the circuit structure can be simplified, and the cost can be saved.
The present invention provides an electric vehicle in which the above-described bidirectional dc converter is provided, and thus has the same or similar advantages as the bidirectional dc converter of the present invention.
Drawings
Fig. 1 is a schematic diagram of the operation of a bidirectional dc converter.
Fig. 2 is a schematic diagram of the operation of a constant current source charging circuit.
Fig. 3 is a schematic block diagram of a precharge circuit of the bidirectional dc converter of the embodiment of the present invention.
FIG. 4 is a diagram illustrating a pre-charging process using the pre-charging method according to the embodiment of the present invention.
Fig. 5 is a topology structural diagram of a bidirectional dc converter according to an embodiment of the present invention.
Description of the drawings:
100-a precharge circuit; 110-main circuit module; 120-a current sampling module; 130-current loop control module; 140-a voltage feedback module; 150-voltage loop control module; 160-PWM control module; 170-a driving module; 200-synchronous rectification circuit.
Detailed Description
As described in the background art, the bidirectional dc pre-charge circuit in the prior art still has the problems of low voltage control accuracy and large influence of temperature variation. In order to overcome the problems, the invention provides a pre-charging circuit and a pre-charging method of a bidirectional direct current converter, the bidirectional direct current converter and an electric vehicle. The invention is described in further detail below with reference to the figures and specific examples. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
Fig. 2 is a schematic diagram of the operation of a constant current source charging circuit. Referring to fig. 2, the constant current source can be implemented in various ways, and the charging concepts are substantially consistent, that is, the corresponding output voltage can be obtained by integrating the charging current with respect to time, as shown in equation (1):
Figure BDA0002327026820000051
wherein iC(t) is the charging current, C is also used to refer to the capacitance of the capacitor C, uC(t) is the charging on the capacitor CPressure, t is time.
For a constant current source, iC(t) is a constant value I, the charging curve is a straight line with a variable t and a slope I/C, as shown in equation (2):
Figure BDA0002327026820000052
in this embodiment, the pre-charging circuit of the bidirectional dc converter is used to pre-charge the capacitor in the bidirectional dc converter before dc conversion is performed, so as to avoid the problem that the capacitor is easy to generate surge current during direct dc conversion.
Fig. 3 is a schematic block diagram of a precharge circuit of the bidirectional dc converter of the embodiment of the present invention. Referring to fig. 3, in the present embodiment, a pre-charge circuit is used to pre-charge a capacitor in a bidirectional dc converter before performing dc conversion, and the pre-charge circuit 100 includes a main circuit module 110, a current sampling module 120, a current loop control module 130, a voltage feedback module 140, and a voltage loop control module 150. The main circuit module 110 is used for providing a charging current to the capacitor; the current sampling module 120 is configured to sample a charging current of the capacitor; the current loop control module 130 is electrically connected to the current sampling module, and is configured to modulate the charging current by using a current loop; the voltage feedback module 140 is configured to obtain a voltage across the capacitor; the voltage loop control module 150 is electrically connected to the voltage feedback module 140, and is configured to modulate the charging current by using a voltage loop.
In the pre-charging circuit 100, the current loop control module 130, the main circuit module 110, and the current sampling module 120 may form a current closed loop system to perform inner loop control, so as to ensure that the output current (i.e., the charging current) of the pre-charging circuit is charged according to a set current value, and may respond to current changes more quickly, adjust the current, and reduce voltage fluctuation during charging, and in addition, in the process of establishing the voltage on the capacitor, the voltage feedback module 140 and the voltage loop control module 150 form outer loop control, so as to control the voltage fluctuation possibly caused by load disturbance, ensure the precision of the output voltage, and control the charging time, so as to enable the charging voltage on the capacitor to reach a preset value. According to the embodiment, the double rings formed by the current ring and the voltage ring are utilized for pre-charging control, the problem of response lag can be solved compared with a single voltage loop, the dynamic response is faster, constant-current charging is realized, the charging time is controlled, the voltage fluctuation in the charging process is reduced, and therefore the voltage control precision is higher. The current loop (as inner loop control) constructed by the current loop control module 130 and the voltage loop (as outer loop control) constructed by the current loop control module 150 in this embodiment may adopt a disclosed circuit structure and calculation method, and, by selecting an applicable dual-loop control, a calculation period of the current loop is shorter than a calculation period of the voltage loop, that is, a dynamic response of the current loop is faster than that of the voltage loop, so that a problem of load jump (such as heavy load, load short circuit, and the like) can be effectively solved, and stability of an output voltage of the precharge circuit is ensured. The pre-charging circuit can be used as a BUCK constant current control circuit, wherein the voltage loop is used for enabling the charging voltage to gradually reach a set value, the current loop is used for realizing constant current control, and a current error calculated by the current loop control module and a current error calculated by the voltage loop control module can be finally used for adjusting the PWM duty ratio so as to realize accurate control of the charging current and the output voltage.
Further, the pre-charge circuit 100 may further include a PWM control module 160 and a driving module 170, the PWM control module 160 is configured to adjust a PWM duty ratio according to outputs of the current loop control module and the voltage loop control module, and the driving module 170 is configured to control a switching element in the main circuit module 110 according to the PWM duty ratio to adjust the magnitude of the charge current. By opening or closing the switching element, the charging current output by the main circuit module 110 may be increased or decreased, so that an error between a sampling value and a set value of the charging current may be reduced, and stable output of the current may be achieved.
The switching element in the main circuit module 110 is, for example, an NMOS transistor, and when it is necessary to increase the charging current and prolong the on-time of the switching element, the driving module 170 may output a high level to the gate of the NMOS transistor, and when it is necessary to decrease the charging current, the off-time of the switching element may be prolonged, and the driving module 170 may output a low level to the gate of the NMOS fet. The switching element is not limited to the MOS tube, but can be various controllable switching devices such as a triode, a thyristor and the like.
Specifically, the modulation of the current loop control module 130 and the voltage loop control module 150 may be an average value or a peak value of the charging current, that is, the pre-charging circuit 100 may implement the output of the constant current source based on a BUCK average current control strategy, or implement the output of the constant current source based on a BUCK peak current control. The precharge circuit 100 may be used in various topologies with bidirectional dc conversion functionality as desired. In this embodiment, the current loop control module 130 is used for current control during the pre-charging process, and can also be used for other functions, such as current control and overload or short-circuit protection, when the bidirectional dc converter performs normal dc conversion, that is, the current loop control module 130 can perform current control during the pre-charging process, and also perform current control protection during the dc conversion, thereby having the effect of function multiplexing. In addition, the switch element in the main circuit module 110 in the pre-charge circuit 100 may adopt a safety protection switch of a bidirectional dc converter, that is, the safety protection switch of the bidirectional dc converter may be used as a safety protection during dc conversion, and may also be used as a switch element for adjusting a charging current during pre-charging a capacitor, in addition, the main circuit module 110 may include a power inductor for modulating a current, and the power inductor may be an EMC filter inductor used by the bidirectional dc converter during dc conversion, that is, the switch element and the power inductor may also be functionally multiplexed, which is helpful to simplify a circuit structure and reduce cost.
The precharge circuit 100 may be implemented by using a hardware circuit, however, all (or a part of) them may also be implemented by software, for example, by using a software program to cooperate with a device or apparatus. For example, the current loop control module 130 and the voltage loop control module 150 may be implemented by hardware circuits and/or by a program stored on a storage medium. The hardware circuitry may include one or more computers, hardware, devices, etc. having means for implementing the inner loop control and the outer loop control processes. When implemented by a computer program provided on a storage medium, the computer program may be a program for executing each step in a computer, a program for forming a computer function as each tool, or a program for causing a computer to realize each of the above-described inner loop control and outer loop control. The storage medium may include a hard disk, a Random Access Memory (RAM), an external storage medium, a storage device via a communication line, a register in a Central Processing Unit (CPU), or the like. Whether implemented in software or hardware, the details of which are not repeated in this specification since those skilled in the electronic and software arts can implement them.
The embodiment also comprises a pre-charging method of the bidirectional direct current converter. FIG. 4 is a diagram illustrating a pre-charging process using the pre-charging method according to the embodiment of the present invention. Wherein the abscissa t is the charging time and the ordinate VOIs the output voltage (i.e., the charge voltage on the capacitor). Referring to fig. 4, the precharge method of the present embodiment is used to precharge a capacitor in the bidirectional dc converter before performing dc conversion, in which the precharge circuit 100 described above is used to control a charging current and an output voltage. The precharge method divides the precharge process into a charge diagnostic phase (period1) and a rapid charge phase (period 2). Specifically, the charging diagnosis step is performed in a charging diagnosis stage, and during the charging diagnosis step, the capacitor in the bidirectional dc converter is pre-charged by the pre-charging circuit 100 with a first charging current, where the first charging current is smaller to slow down the charging speed, and if the charging diagnosis step is performed within a preset time T01Internal, not charged to threshold voltage U01If the voltage of the bidirectional dc converter is not equal to the predetermined voltage, the operation of the bidirectional dc converter is not immediately performed, and the operation of the bidirectional dc converter needs to be diagnosed. If atPreset time T01The output voltage can reach the threshold voltage U01Then, a fast charging phase may be entered, in which the capacitor in the bidirectional dc converter is pre-charged with the second charging current by using the pre-charging circuit 100 (time T)02) Until reaching the set voltage U of the capacitor02. The charging current used for the rapid charging may be larger than the charging diagnosis period, i.e., the second charging current is larger than the first charging current. Threshold voltage U on capacitor01And a set voltage U02The setting can be carried out according to the specific situation of the bidirectional direct current converter.
The pre-charging method of the embodiment can accurately control the output current and voltage by adopting the pre-charging circuit 100, effectively solve the problem of load jump, ensure the stability of the output voltage, improve the precision of the output voltage, and has small influence of temperature factors and wider application environment temperature range. By utilizing the pre-charging method, abnormal working conditions such as load short circuit and the like can be diagnosed in time, the phenomena of abnormal working of a switching element and the like in the pre-charging process are avoided, and risks are identified in advance. The pre-charging method can control the precision of the charging current and the output voltage and can also control the charging time. Through the pre-charging, the problem of pre-charging the voltage of a capacitor (especially a large capacitor) in the bidirectional direct current converter can be effectively solved, the surge current is reduced, and the service life of the system is prolonged.
The present embodiment also includes a bi-directional dc converter. Fig. 5 is a topology structural diagram of a bidirectional dc converter according to an embodiment of the present invention. Referring to fig. 5, the bidirectional dc converter is used for dc conversion between a first power source (e.g. 12V battery) and a second power source (e.g. 48V battery), the negative electrodes of the first power source and the second power source are grounded, the bidirectional dc converter further includes a first capacitor C1, a second capacitor C2, a conversion circuit, a safety protection switch Q1, and the pre-charge circuit 100, the first capacitor C1 is connected between the port of the first power source and ground, the second capacitor C2 is connected between the port of the second power source and ground, the conversion circuit is disposed between the first power source and the second power source, the safety protection switch Q1 is connected to the first port, and the pre-charge circuit 100 is used for pre-charging the first capacitor C1 and the second capacitor C2 before dc conversion.
Specifically, the first power supply may be a low voltage power supply, such as a 12V power supply system, and the second power supply may be a high voltage power supply, such as a 48V or 400V power supply system. Further, the second capacitor C2 provided between the port of the second power supply and the ground may be a high-side parasitic capacitor. The first capacitor C1 may be an internal capacitor of the bidirectional dc converter.
In this embodiment, the main circuit module 110 of the pre-charge circuit 100 includes a first sampling resistor shunt1, a diode D1, a first power inductor L1, and the safety protection switch Q1, wherein the safety protection switch Q1 of the bidirectional dc converter is multiplexed and used as a switching element for current regulation in the pre-charge circuit 100. As shown in fig. 5, the first sampling resistor shunt1, the first power inductor L1, and the safety protection switch Q1 are connected in series to the other end of the first capacitor C1, the current sampling module 120 is electrically connected to the first sampling resistor shunt1, and the diode D1 is connected between a node between the first power inductor L1 and the safety protection switch Q1 and ground. Specifically, the anode of the diode D1 is connected to the node between the first switching element Q1 and the first power inductor L1, and the cathode of the diode D1 is grounded. The voltage feedback module 140 of the pre-charge circuit 100 is electrically connected to the other end of the second capacitor C2 outside the ground end to obtain the voltage on the second capacitor C2. In another embodiment, the first capacitor C1 and the second capacitor C2 are charged in segments, and the voltage feedback module 140 may also be electrically connected to the other end of the first capacitor C1 outside the ground end to obtain the voltage on the first capacitor C1 and form a voltage loop control through the voltage loop control module 150.
In this embodiment, when the bidirectional dc converter performs dc conversion, the first power inductor L1 in the main circuit module 110 of the pre-charge circuit 100 may perform EMC filtering as an EMC filter inductor. Furthermore, when the bidirectional dc converter performs dc conversion, the current loop function of the current loop control module 130 in the pre-charge circuit 100 can also be applied to respond to current variation and perform control, such as current control, overload or short-circuit protection.
The conversion circuit is disposed between the first power supply and the second power supply, and is configured to convert a bidirectional direct current, and in this embodiment, the conversion circuit includes a synchronous rectification circuit 200. In the bidirectional dc converter, the synchronous rectification circuit 200 may be provided in more than one way, for example, in some high power applications, multiple synchronous rectification circuits may be arranged in parallel and staggered. The internal capacitor C1 is disposed between the node between the synchronous rectification circuit 200 and the pre-charge circuit 100 and the ground.
In the bidirectional dc converter of this embodiment, the synchronous rectification circuit 200 may include a second EMC filter inductor L2, a third switching element Q3 and a fourth switching element Q4, wherein a first end of the second EMC filter inductor L2 is connected to the second capacitor C1, a first end of the third switching element Q3 is connected to a second end of the second EMC filter inductor L2, a second end of the third switching element Q3 is grounded, a first end of the fourth switching element Q4 is connected to a node between the second EMC filter inductor L2 and the third switching element Q3, and a second end of the fourth switching element Q4 is connected to a port of the high voltage power supply. The third switching element Q3 and the fourth switching element Q4 may be MOS field effect transistors or switching elements such as transistors and thyristors. In the bidirectional dc converter of this embodiment, a second sampling resistor shunt2 may be disposed between the second end of the fourth switching element Q4 and the high-voltage connection terminal, and a relay switch may be disposed between the high-voltage port and the high-voltage power supply.
As can be seen from the foregoing description, the capacitors (including the first capacitor C1 and the second capacitor C2 in the present embodiment) in the bidirectional dc converter are precharged by the precharge circuit 100 before the bidirectional dc converter performs dc conversion, so as to reduce or avoid the inrush current. In the pre-charging process, the current sampling module 120 samples the charging current, the voltage feedback module 140 can obtain the current voltage of the capacitor, and the voltage feedback module 140 can also be used to determine whether the voltage on the capacitor reaches a preset value. The current loop control module 130 and the voltage loop control module 150 perform dual-loop control on the charging current and the charging voltage, so as to control the charging current provided by the main circuit module 110 to be a constant value, and during the pre-charging process, the pre-charging circuit 100 can be regarded as a constant current source, so that the charging current is stable.
Referring to fig. 5, as an example, the dual-loop control of the precharge circuit 100 may employ the following procedure. The voltage feedback module 140 is connected to the high-voltage side parasitic capacitor C2 to obtain a voltage feedback thereon, and then transmits the voltage feedback to the voltage loop control module 150, the voltage loop control module 150 performs power adjustment according to the feedback voltage and transmits a current output to the current loop control module 120, and the current loop control module 120 receives the sampling current of the current sampling module 120 and the current output by the voltage loop control module 150, and stabilizes the charging current through a current closed-loop system. The current loop control module 130 includes, for example, a PID regulator, the current loop control module 130 outputs assignment to the PWM control module 160 through the PID regulator, the PWM control module 160 may include a PWM modulator, the PWM modulator adjusts the PWM frequency according to the assignment and outputs a PWM duty signal, and the driving module 170 controls the on-off state of the switching element according to the digital pulse of the PWM duty signal, so that the sampled charging current (actual current) approaches the set charging current value, that is, the effect of constant current source output can be achieved.
The bidirectional direct current converter of the embodiment can prevent the generation of surge current during the operation of the converter by pre-charging the high-voltage side parasitic capacitor C2 and the internal capacitor C1, and damages related devices, and during the pre-charging process, the pre-charging circuit 100 of the embodiment is adopted to perform double-loop control on the pre-charging process, so that the bidirectional direct current converter can quickly respond to various current changes caused by load disturbance, heavy load, load short circuit and the like, adjust current, control charging time, reduce voltage fluctuation in the charging process, ensure the precision of output voltage, and enable the charging voltage on the charging capacitor to reach a preset value. Moreover, the output voltage and current are controlled by the pre-charging circuit 100, and the influence of the working temperature is small, so that the application environment temperature of the bidirectional direct current converter is wide.
The procedure of precharging the bidirectional dc converter shown in fig. 5 by using the precharge circuit 100 of the present embodiment can be referred to fig. 4, specifically, in the power-up stage of the bidirectional dc converter, the internal capacitor C1 and the high-voltage side parasitic capacitor C2 are charged by the precharge circuit 100. In the charging process, on one hand, the first sampling resistor shunt1, the current sampling circuit 120 and the current loop control module 130 form a current closed loop system to perform inner loop control to ensure that the constant current source charges according to a set current value and has a faster dynamic response, and on the other hand, in the process of gradually establishing the voltages of the internal capacitor C1 and the high-voltage side parasitic capacitor C2, the voltage feedback module 140 and the voltage loop control module 150 of the pre-charging circuit 100 form outer loop control to ensure the accuracy of the output voltage, so that the voltages of the internal capacitor C1 and the high-voltage side parasitic capacitor C2 reach a set value. The bidirectional DC converter adopts the pre-charging circuit 100 to pre-charge the first capacitor and the second capacitor before DC conversion, so that on one hand, the precision of charging current and output voltage can be improved, and on the other hand, the voltage U between the base electrode and the emitter electrode of the triode is controlled compared with the prior artbeThe pre-charging circuit 100 of this embodiment is less affected by the operating temperature, so that the applicable temperature range of the applied bidirectional dc converter is wider, and on the other hand, the circuit used when the pre-charging circuit 100 and the bidirectional dc converter perform dc conversion can be multiplexed by a plurality of elements, so that the capacitor voltage pre-charging can be realized with less cost. The bidirectional direct current converter can be used in vehicles such as hybrid electric vehicles and electric vehicles, and can also be used in other devices needing direct current conversion.
The embodiment further comprises an electric vehicle, wherein the electric vehicle can be a hybrid electric vehicle or a pure electric vehicle, and the bidirectional direct current converter is included in the electric vehicle. The bidirectional direct current converter can be particularly used for bidirectional direct current conversion between a 48V battery system and a 12V battery system or between a 400V battery system and a 12V battery system in an electric automobile.
It should be noted that the present specification is described in a progressive manner, and the following description focuses on differences from the preceding description, and the same and similar parts may be referred to each other.
The above description is only for the purpose of describing the preferred embodiments of the present invention and is not intended to limit the scope of the claims of the present invention, and any person skilled in the art can make possible the variations and modifications of the technical solutions of the present invention using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention, and therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention belong to the protection scope of the technical solutions of the present invention.

Claims (14)

1. A pre-charge circuit for a bi-directional dc converter for pre-charging a capacitor in the bi-directional dc converter prior to dc conversion, the pre-charge circuit comprising:
the main circuit module is used for providing a charging current for the capacitor;
the current sampling module is used for sampling the charging current of the capacitor;
the current loop control module is electrically connected with the current sampling module and is used for modulating the charging current by utilizing a current loop;
the voltage feedback module is used for acquiring the voltage on the capacitor; and
and the voltage ring control module is electrically connected with the voltage feedback module and is used for modulating the charging current by utilizing a voltage ring.
2. The precharge circuit as claimed in claim 1, further comprising:
the PWM control module is used for adjusting the PWM duty ratio according to the output of the current loop control module and the voltage loop control module; and
and the driving module is used for controlling a switching element in the main circuit module according to the PWM duty ratio signal so as to adjust the magnitude of the charging current.
3. The precharge circuit as claimed in claim 2, wherein said switching element is a safety protection switch of said bidirectional dc converter.
4. The precharge circuit as claimed in claim 1, wherein the current loop control block and the voltage loop control block modulate whether an average value or a peak value of the charging current.
5. A pre-charging method for a bidirectional dc converter, for pre-charging a capacitor in the bidirectional dc converter before dc conversion, comprising a charging diagnosis step, wherein the pre-charging circuit according to any one of claims 1 to 4 is used to pre-charge the capacitor in the bidirectional dc converter with a first charging current, and detect whether the voltage on the capacitor reaches a threshold voltage within a preset time, if the voltage does not reach the threshold voltage, the operating condition of the bidirectional dc converter is diagnosed, and if the voltage reaches the threshold voltage, the pre-charging circuit according to any one of claims 1 to 4 is used to pre-charge the capacitor in the bidirectional dc converter with a second charging current until a set voltage is reached, and the second charging current is greater than the first charging current.
6. A bi-directional dc converter for converting dc between a first power source and a second power source, the cathodes of the first and second power sources being connected to ground, the bi-directional dc converter comprising:
a first capacitor connected between a port of the first power supply and ground;
a second capacitor connected between a port of the second power supply and ground;
a conversion circuit configured between the first power supply and the second power supply;
the safety protection switch is connected with the first port; and
a pre-charge circuit as claimed in any one of claims 1 to 4, the pre-charge circuit being arranged to pre-charge the first and second capacitors prior to DC conversion.
7. The bidirectional dc converter of claim 6 wherein said first power source is a low voltage power source, said second power source is a high voltage power source, and said second capacitor is a high side parasitic capacitor.
8. The bi-directional dc converter of claim 7, wherein the voltage feedback module of the pre-charge circuit is electrically connected to the other end of the second capacitor outside the ground terminal to obtain the voltage on the second capacitor.
9. The bidirectional dc converter of claim 7 wherein said low voltage power supply is a 12V power supply system and said high voltage power supply is a 48V or 400V power supply system.
10. The bidirectional dc converter according to claim 6, wherein the main circuit module of the pre-charge circuit comprises a first sampling resistor, a diode, a first power inductor, and the safety protection switch, wherein the first sampling resistor, the first power inductor, and the safety protection switch are connected in series to the other end of the first capacitor outside the ground terminal, the current sampling module is electrically connected to the first sampling resistor, and the diode is connected between a node between the first power inductor and the safety protection switch and ground.
11. The bidirectional dc converter of claim 6 wherein said first power inductor acts as an EMC filter inductor when said bidirectional dc converter is performing dc conversion.
12. The bidirectional dc converter according to claim 6, wherein a current loop control module of the pre-charge circuit is used for current control, overload or short-circuit protection when the bidirectional dc converter performs dc conversion.
13. The bidirectional dc converter of claim 6 wherein said conversion circuit includes a synchronous rectification circuit.
14. An electric vehicle, characterized in that it is equipped with a bidirectional dc converter according to any one of claims 6 to 13.
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