DC / DC bidirectional charging circuit and charger

Abstract

The invention relates to the technical field of direct current charging, in particular to a DC / DC bidirectional charging circuit and a charger, and the DC / DC bidirectional charging circuit comprises a power port, a super capacitor port, a capacitor C1, a pre-charging module and a power module. The power module comprises a low-voltage end, a high-voltage end and a Boost / Buck conversion circuit; the DC / DC bidirectional charger comprises the above DC / DC bidirectional charging circuit. According to the invention, the power module comprises the Boost / Buck conversion circuit, Boost conversion or Buck conversion can be selectively carried out, according to Boost / Buck function selection, four functions of step-down pre-charging, step-down charging, step-up pre-charging and step-up charging are integrated in one Boost / Buck conversion circuit, and compared with the prior art, the use number of IGBTs and the control process are reduced.

Description

Technical Field

[0001] The present application belongs to the field of direct current charging technology, and in particular relates to a DC / DC bidirectional charging circuit and a charger. Background Art

[0002] Existing two-stage conversion DC / DC unidirectional charging circuit, such as Figure 1 As shown, two DC / DC power conversion modules are used, one DC / DC Buck circuit and the other symmetrical three-level DC / DC Boost circuit. Only unidirectional charging is possible, and the charging process is completed by the combination of the two circuits.

[0003] When the lithium battery charges the supercapacitor and the voltage across the supercapacitor is lower than the voltage across the lithium battery, the Buck circuit is used for step-down charging; when the voltage across the supercapacitor is higher than the voltage across the lithium battery, the Boost circuit is used for step-up charging.

[0004] Existing chargers use a large number of IGBTs and diodes, resulting in high device costs. This large number of IGBTs also complicates control. Furthermore, IGBTs incur conduction and switching losses when turning on and off, resulting in high overall losses in bidirectional chargers and low charging efficiency. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present application proposes a DC / DC bidirectional charging circuit and a charger.

[0006] A DC / DC bidirectional charging circuit includes: a power port, a supercapacitor port, a capacitor C1, a pre-charge module, and a power module; wherein, The power module includes a low-voltage end, a high-voltage end, and a Boost / Buck conversion circuit; The power port is connected in sequence to the pre-charge module and the high-voltage end of the power module to form a step-down pre-charging circuit; the power port is connected in sequence to the high-voltage end of the power module, the Boost / Buck conversion circuit, the low-voltage end of the power module and the supercapacitor port to form a step-down charging circuit; the power port is connected in sequence to the pre-charge module and the capacitor C1 to form a boost pre-charging circuit; the power port is connected in sequence to the capacitor C1, the low-voltage end of the power module, the Boost / Buck conversion circuit, the high-voltage end of the power module and the supercapacitor port to form a boost charging circuit.

[0007] Furthermore, the pre-charging module includes a resistor R1 and a resistor R2, wherein one end of the resistor R1 is connected to the positive electrode of the power port, and one end of the resistor R2 is connected to the negative electrode of the power port.

[0008] Furthermore, in the step-down pre-charging circuit, the positive pole of the power port is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the positive pole of the high-voltage end of the power module, and a relay K3 is also connected in series between the resistor R1 and the positive pole of the high-voltage end of the power module; the negative pole of the power port is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the negative pole of the high-voltage end of the power module, and a relay K4 is also connected in series between the resistor R2 and the negative pole of the high-voltage end of the power module.

[0009] Furthermore, in the boost pre-charging circuit, the positive electrode of the power port is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the capacitor C1, and a relay K1 is connected in series between the resistor R1 and the capacitor C1. The negative electrode of the power port is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the other end of the capacitor C1, and a relay K2 is connected in series between the resistor R2 and the capacitor C1.

[0010] Furthermore, the Boost / Buck conversion circuit includes two inductors, four IGBT modules and two capacitors, wherein the two inductors are L1 and L2, the four IGBT modules are VT1, VT2, VT3 and VT4, and the two capacitors are Cd1 and Cd2, wherein the emitter of VT1 is connected to the collector of VT2, the emitter of VT2 is connected to the collector of VT3, the emitter of VT3 is connected to the collector of VT4, the collector of VT1 is simultaneously connected to the positive electrode of capacitor Cd1 and the positive electrode of the high-voltage end, the emitter of VT4 is simultaneously connected to the negative electrode of capacitor Cd2 and the negative electrode of the high-voltage end, one end of the inductor L1 is connected to the positive electrode of the low-voltage end, the other end of the inductor L1 is connected to the emitter of VT1, one end of the inductor L2 is connected to the negative electrode of the low-voltage end, the other end of the inductor L2 is connected to the collector of VT4, and the negative electrode of capacitor Cd1 is simultaneously connected to the emitter of VT2 and the positive electrode of Cd2; Furthermore, in the boost charging circuit, the connection between the power supply port and the low voltage end of the power module is controlled by the contactor KM1, and the connection between the high voltage end of the power module and the supercapacitor port is controlled by the contactor KM3.

[0011] Furthermore, in the step-down charging circuit, the connection between the power supply port and the high voltage end of the power module is controlled by the contactor KM2, and the connection between the low voltage end of the power module and the supercapacitor port is controlled by the contactor KM4.

[0012] Furthermore, it also includes: a protection circuit, which includes a fuse FU1 installed at the positive pole of the power port and a fuse FU2 installed at the negative pole of the power port.

[0013] A DC / DC bidirectional charger comprises: the DC / DC bidirectional charging circuit described above.

[0014] The technical effects and advantages of this application are: In this application, the power module includes a Boost / Buck conversion circuit, which can choose to perform Boost conversion or Buck conversion. According to the function selection of Boost / Buck, this application combines the four functions of buck pre-charging, buck charging, boost pre-charging, and boost charging into one Boost / Buck conversion circuit. Compared with the existing technology, the number of IGBTs used and the control process are reduced.

[0015] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures indicated in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a circuit diagram of a DC / DC unidirectional charging circuit in the prior art; Figure 2 A circuit diagram of a DC / DC bidirectional charging circuit for this application; Figure 3 This is the system topology diagram of the process of charging and discharging pulse loads using a DC / DC bidirectional charger for lithium batteries and supercapacitors in this application. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0018] In addition, in the invention, the terms "first", "second" and other similar words are not intended to imply any order, quantity and importance, but are merely used to distinguish different elements. The terms "upper", "lower", "left", "right" and other similar words are merely positional relationships in the drawings.

[0019] An embodiment of the present application provides a DC / DC bidirectional charging circuit, comprising: a power port, a supercapacitor port, a pre-charge module, and a power module; wherein the power module comprises a low-voltage end, a high-voltage end, and a Boost / Buck conversion circuit; the power port is sequentially connected to the pre-charge module and the high-voltage end of the power module to form a step-down pre-charging circuit; the power port is sequentially connected to the high-voltage end of the power module, the Boost / Buck conversion circuit, the low-voltage end of the power module, and the supercapacitor port to form a step-down charging circuit; the power port is sequentially connected to the pre-charge module and capacitor C1 to form a boost pre-charging circuit; the power port is sequentially connected to capacitor C1, the low-voltage end of the power module, the Boost / Buck conversion circuit, the high-voltage end of the power module, and the supercapacitor port to form a boost charging circuit.

[0020] In this way, the Boost / Buck conversion circuit can choose to perform Boost conversion or Buck conversion. According to the function selection of Boost / Buck, this application combines the four functions of buck pre-charging, buck charging, boost pre-charging, and boost charging into one Boost / Buck conversion circuit. Compared with the existing technology, it reduces the number of IGBTs used and the control process.

[0021] Specifically, like Figure 2 As shown, the pre-charge module is composed of a resistor R1 and a resistor R2, wherein one end of the resistor R1 is connected to the positive electrode (B+) of the power port, and one end of the resistor R2 is connected to the negative electrode (B-) of the power port; Thus, in the step-down pre-charging circuit, B+ is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the relay K3 and the positive high-voltage terminal of the power module in sequence, and B- is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the relay K4 and the negative high-voltage terminal of the power module in sequence; In the boost pre-charge circuit, B+ is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the relay K1 and one end of the capacitor C1 in sequence, and B- is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the relay K2 and the other end of the capacitor C1 in sequence.

[0022] In one embodiment of the present application, the Boost / Buck conversion circuit includes two inductors (inductor L1, inductor L2), four IGBT modules (VT1, VT2, VT3, VT4) and two capacitors (capacitor Cd1, capacitor Cd2), wherein the emitter of VT1 is connected to the collector of VT2, the emitter of VT2 is connected to the collector of VT3, the emitter of VT3 is connected to the collector of VT4, the collector of VT1 is simultaneously connected to the positive electrode of capacitor Cd1 and the positive electrode of the high-voltage end, the emitter of VT4 is simultaneously connected to the negative electrode of capacitor Cd2 and the negative electrode of the high-voltage end, one end of the inductor L1 is connected to the positive electrode of the low-voltage end, the other end of the inductor L1 is connected to the emitter of VT1, one end of the inductor L2 is connected to the negative electrode of the low-voltage end, the other end of the inductor L2 is connected to the collector of VT4, and the negative electrode of capacitor Cd1 is simultaneously connected to the emitter of VT2 and the positive electrode of Cd2; Thus, in the boost charging circuit, B+ is connected to the contactor KM1 and the positive electrode of the low-voltage end in sequence, the positive electrode of the high-voltage end is connected to the contactor KM3 and the positive electrode of the supercapacitor port in sequence, B- is connected to the contactor KM1 and the negative electrode of the low-voltage end in sequence, the negative electrode of the high-voltage end is connected to the contactor KM3 and the negative electrode of the supercapacitor port in sequence, and the capacitor C1 is located between the contactor KM1 and the power module; In the step-down charging circuit, B+ is connected to contactor KM2 and the positive pole of the high-voltage end in sequence, the positive pole of the low-voltage end is connected to contactor KM4 and the positive pole of the supercapacitor port in sequence, B- is connected to contactor KM2 and the negative pole of the high-voltage end in sequence, and the negative pole of the low-voltage end is connected to contactor KM4 and the negative pole of the supercapacitor port in sequence.

[0023] In one embodiment of the present application, a DC / DC bidirectional charging circuit further includes: a protection circuit, the protection circuit including a fuse FU1 installed at B+ and a fuse FU2 installed at B-.

[0024] In one embodiment of the present application, the power port is connected to a lithium battery with a voltage level of 1000V, and the supercapacitor port is connected to a supercapacitor with a voltage level of 0-2200V. The working process of the DC / DC bidirectional charging circuit is as follows: When a lithium battery charges a supercapacitor, the input side is the lithium battery and the output side is the supercapacitor. The charging process is divided into two stages; Phase 1: At the initial stage of charging, the voltage across the supercapacitor is between 0 and 1000V. Relays K3 and K4 are closed, and the lithium battery begins to discharge. The current passes through resistors R1, R2, and relays K3 and K4 to the high-voltage end of the power module, pre-charging capacitors Cd1 and Cd2. After the pre-charging is completed, relays K3 and K4 are disconnected, and contactors KM2 and KM4 are closed. The charging current flows from the lithium battery through contactor KM2 and is input from the high-voltage end of the power module. After the DC / DC Buck converter of the power module, it is output from the low-voltage end of the power module and then flows through contactor KM4 to the supercapacitor side. This process is the lithium battery stepping down and charging the supercapacitor. Phase 2: When the voltage across the supercapacitor is between 1000V and 2200V, contactors KM2 and KM4 are disconnected, and relays K1 and K2 are closed. The lithium battery begins to discharge, and the current pre-charges capacitor C1 through resistors R1, R2, and relays K1 and K2. After the pre-charging is completed, relays K1 and K2 are disconnected, and contactors KM1 and KM3 are closed. The charging current flows from the lithium battery through contactor KM1 and is input from the low-voltage end of the power module. After the DC / DC Boost conversion of the power module, it is output from the high-voltage end of the power module and then flows to the supercapacitor side through contactor KM3. This process is the lithium battery boosting and charging the supercapacitor.

[0025] When the supercapacitor charges the lithium battery in the reverse direction, the input side is the supercapacitor and the output side is the lithium battery. The charging process is also divided into two stages.

[0026] Phase 1: At the initial stage of charging, the voltage across the supercapacitor is between 1000 and 2200V, which is higher than the voltage across the lithium battery. Relays K3 and K4 are closed, and the lithium battery begins to discharge. The current passes through resistors R1, R2, and relays K3 and K4 to the high-voltage end of the power module to pre-charge capacitors Cd1 and Cd2. After the pre-charging is completed, relays K3 and K4 are disconnected, and contactors KM3 and KM1 are closed. The charging current flows from the supercapacitor through contactor KM3 and is input from the high-voltage end of the power module. After the DC / DC Buck converter of the power module, it is output from the low-voltage end of the power module and then flows to the lithium battery side through contactor KM1. This process is the supercapacitor stepping down and charging the lithium battery.

[0027] Phase 2: When the voltage across the supercapacitor is between 0 and 1000 V, which is lower than the voltage across the lithium battery, contactors KM3 and KM1 are disconnected, and relays K1 and K2 are closed. The lithium battery begins to discharge, and the current passes through resistors R1, R2, and relays K1 and K2 to the low-voltage end of the power module to pre-charge capacitor C1. After the pre-charging is completed, relays K1 and K2 are disconnected, and contactors KM4 and KM2 are closed. The charging current flows from the supercapacitor through contactor KM4 and flows into the low-voltage end of the power module. After the DC / DC Boost conversion of the power module, it is output from the high-voltage end of the power module and then flows to the lithium battery side through contactor KM2. This process is the supercapacitor boosting and charging the lithium battery.

[0028] Based on the DC / DC bidirectional charging circuit described above, an embodiment of the present application further provides a DC / DC bidirectional charger, comprising: the DC / DC bidirectional charging circuit described above.

[0029] Based on the above DC / DC bidirectional charging circuit, the lithium battery and supercapacitor charge and discharge the pulse load through the DC / DC bidirectional charger. Figure 3 As shown, the supercapacitor is connected to the lithium battery through the bidirectional charger of this application. The lithium battery and supercapacitor realize the controllable discharge of the lithium battery and supercapacitor through the DC / DC bidirectional charging circuit, and realize the controllable charging of the supercapacitor and other functions at the same time, completing the hybrid energy storage of the two and achieving the perfect combination of high energy density and high power density. The lithium battery charges the supercapacitor through the charging module. When the supercapacitor is fully charged, the supercapacitor supplies power to the pulse load, meeting the high peak power requirement of the pulse load.

[0030] For the specific limitations of the DC / DC bidirectional charger, please refer to the limitations of the DC / DC bidirectional charging circuit above, which will not be repeated here.

[0031] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A DC / DC bidirectional charging circuit, characterized in that: include: Power port, supercapacitor port, capacitor C1, pre-charge module, power module; among them, The power module includes a low-voltage end, a high-voltage end, and a Boost / Buck conversion circuit; The power port is connected in sequence to the pre-charge module and the high-voltage end of the power module to form a step-down pre-charging circuit; the power port is connected in sequence to the high-voltage end of the power module, the Boost / Buck conversion circuit, the low-voltage end of the power module and the supercapacitor port to form a step-down charging circuit; the power port is connected in sequence to the pre-charge module and the capacitor C1 to form a boost pre-charging circuit; the power port is connected in sequence to the capacitor C1, the low-voltage end of the power module, the Boost / Buck conversion circuit, the high-voltage end of the power module and the supercapacitor port to form a boost charging circuit.

2. A DC / DC bidirectional charging circuit according to claim 1, characterized in that: The pre-charge module includes a resistor R1 and a resistor R2, wherein one end of the resistor R1 is connected to the positive electrode of the power port, and one end of the resistor R2 is connected to the negative electrode of the power port.

3. A DC / DC bidirectional charging circuit according to claim 2, characterized in that: In the step-down pre-charging circuit, the positive electrode of the power port is connected to one end of the resistor R1, the other end of the resistor R1 is connected to the positive electrode of the high-voltage end of the power module, and a relay K3 is connected in series between the resistor R1 and the positive electrode of the high-voltage end of the power module; the negative electrode of the power port is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the negative electrode of the high-voltage end of the power module, and a relay K4 is connected in series between the resistor R2 and the negative electrode of the high-voltage end of the power module.

4. A DC / DC bidirectional charging circuit according to claim 2, characterized in that: In the boost pre-charge circuit, the positive electrode of the power port is connected to one end of the resistor R1, the other end of the resistor R1 is connected to one end of the capacitor C1, and a relay K1 is connected in series between the resistor R1 and the capacitor C1. The negative electrode of the power port is connected to one end of the resistor R2, the other end of the resistor R2 is connected to the other end of the capacitor C1, and a relay K2 is connected in series between the resistor R2 and the capacitor C1.

5. The DC / DC bidirectional charging circuit according to claim 1, characterized in that: The Boost / Buck conversion circuit includes two inductors, four IGBT modules and two capacitors, wherein the two inductors are L1 and L2, the four IGBT modules are VT1, VT2, VT3 and VT4, and the two capacitors are Cd1 and Cd2, wherein the emitter of VT1 is connected to the collector of VT2, the emitter of VT2 is connected to the collector of VT3, the emitter of VT3 is connected to the collector of VT4, the collector of VT1 is simultaneously connected to the positive electrode of capacitor Cd1 and the positive electrode of the high-voltage end, the emitter of VT4 is simultaneously connected to the negative electrode of capacitor Cd2 and the negative electrode of the high-voltage end, one end of the inductor L1 is connected to the positive electrode of the low-voltage end, the other end of the inductor L1 is connected to the emitter of VT1, one end of the inductor L2 is connected to the negative electrode of the low-voltage end, the other end of the inductor L2 is connected to the collector of VT4, and the negative electrode of capacitor Cd1 is simultaneously connected to the emitter of VT2 and the positive electrode of Cd2.

6. The DC / DC bidirectional charging circuit according to claim 1, characterized in that: In the boost charging circuit, the connection between the power supply port and the low voltage end of the power module is controlled by the contactor KM1, and the connection between the high voltage end of the power module and the supercapacitor port is controlled by the contactor KM3.

7. The DC / DC bidirectional charging circuit according to claim 1, characterized in that: In the step-down charging circuit, the connection between the power supply port and the high voltage end of the power module is controlled by the contactor KM2, and the connection between the low voltage end of the power module and the supercapacitor port is controlled by the contactor KM4.

8. The DC / DC bidirectional charging circuit according to claim 1, characterized in that: Also includes: A protection circuit includes a fuse FU1 installed at the positive pole of the power port and a fuse FU2 installed at the negative pole of the power port.

9. A DC / DC bidirectional charger, characterized in that: include: A DC / DC bidirectional charging circuit according to any one of claims 1 to 8.

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