Direct current conversion circuit

Abstract

The utility model belongs to the technical field of direct-current conversion circuits, and provides a direct-current conversion circuit, which comprises two direct-current conversion primary side branches, two direct-current conversion secondary side branches and two transformers, and is characterized in that a voltage input end of the first direct-current conversion primary side branch is used for being connected with an anode of a direct-current voltage source, and a voltage output end of the second direct-current conversion secondary side branch is used for being connected with a cathode of the direct-current voltage source; the voltage conversion end is connected with the primary side of the first high-frequency isolation transformer, the voltage output end is connected with one voltage input end of the second direct-current conversion primary side branch, the voltage conversion end of the second direct-current conversion primary side branch is connected with the primary side of the second high-frequency isolation transformer, and the other voltage input end is used for being connected with the negative electrode of the direct-current voltage source. The secondary side of the second high-frequency isolation transformer is connected with a second direct-current conversion secondary side branch, the secondary side of the first high-frequency isolation transformer is connected with a first direct-current conversion secondary side branch, and two output ends of the direct-current conversion circuit are obtained after the second direct-current conversion secondary side branch and the first direct-current conversion secondary side branch are connected in parallel; the output module is used for outputting output voltage corresponding to the direct-current voltage source.

Description

Technical Field

[0001] The utility model relates to the technical field of DC conversion circuits, and particularly relates to a DC conversion circuit. Background Art

[0002] Currently, if it is necessary to implement the DC conversion (DC / DC) function of an input DC voltage of 1500Vdc, due to the voltage withstand limitation of electronic switching devices themselves, the NPC (or ANPC) three-level circuit topology needs to be adopted. The NPC (or ANPC) three-level circuit has disadvantages such as complex control and high cost (a large number of core devices IGBTs are used).

[0003] In the common NPC (or ANPC) three-level circuit topology, the number of IGBTs used is at least 12. Therefore, not only is the hardware input cost relatively high, but 12 IGBTs need to be separately logically controlled, so the control is also relatively complex. Summary of the Utility Model

[0004] The purpose of the utility model is to provide a DC conversion circuit with a simple structure and fewer IGBTs used, and it is not necessary to set separate control logics for each IGBT, and it can achieve an input DC voltage of 1500Vdc.

[0005] To solve its technical problems, the utility model adopts the following technical solutions:

[0006] A DC conversion circuit includes:

[0007] A first DC conversion primary branch, a first DC conversion secondary branch, a second DC conversion primary branch, a second DC conversion secondary branch, a first high-frequency isolation transformer, and a second high-frequency isolation transformer;

[0008] The voltage input end of the first DC conversion primary branch is used to connect the positive pole of a DC voltage source. The voltage conversion end of the first DC conversion primary branch is connected to the primary side of the first high-frequency isolation transformer. The voltage output end of the first DC conversion primary branch is connected to a voltage input end of the second DC conversion primary branch. The voltage conversion end of the second DC conversion primary branch is connected to the primary side of the second high-frequency isolation transformer. The other voltage input end of the second DC conversion primary branch is used to connect the negative pole of the DC voltage source;

[0009] The secondary side of the second high-frequency isolation transformer is connected to the second DC conversion secondary branch. The secondary side of the first high-frequency isolation transformer is connected to the first DC conversion secondary branch. The second DC conversion secondary branch and the first DC conversion secondary branch are connected in parallel to obtain two output ends of the DC conversion circuit, which are used to output an output voltage corresponding to the DC voltage source.

[0010] As a further optimization, the first DC conversion primary branch includes a first capacitor, a third capacitor, a first IGBT, a second IGBT, a third IGBT, and a fourth IGBT;

[0011] One end of the first capacitor serves as the voltage input terminal of the first DC conversion primary branch, and the other end serves as the voltage output terminal of the first DC conversion primary branch. The collector of the first IGBT and the collector of the third IGBT are both connected to one end of the first capacitor. The emitter of the first IGBT is connected to the collector of the second IGBT, and the emitter of the third IGBT is connected to the collector of the fourth IGBT. The emitters of the second IGBT and the fourth IGBT are both connected to the other end of the first capacitor. The emitter of the second IGBT serves as the voltage output terminal of the first DC conversion primary branch. One end of the third capacitor is connected to the emitter of the first IGBT, and the other end serves as a voltage conversion terminal of the first DC conversion primary branch and is connected to one end of the primary side of the first high-frequency isolation transformer. The emitter of the third IGBT serves as the other voltage conversion terminal of the first DC conversion primary branch, and the emitter of the third IGBT is connected to the other end of the primary side of the first high-frequency isolation transformer.

[0012] As a further optimization, the second DC conversion primary branch includes a second capacitor, a fifth IGBT, a sixth IGBT, a seventh IGBT, an eighth IGBT, and a fourth capacitor;

[0013] One end of the second capacitor serves as a voltage input terminal of the second DC conversion primary branch and is connected to the emitter of the second IGBT. The collector of the fifth IGBT and the collector of the seventh IGBT are both connected to one end of the second capacitor. The emitter of the fifth IGBT is connected to the collector of the sixth IGBT, and the emitter of the seventh IGBT is connected to the collector of the eighth IGBT. The emitters of the sixth IGBT and the eighth IGBT are both connected to the other end of the second capacitor. The other end of the second capacitor serves as the other voltage input terminal of the second DC conversion primary branch and is used to connect to the negative pole of the DC voltage source. One end of the fourth capacitor is connected to the emitter of the fifth IGBT, and the other end serves as a voltage conversion terminal of the second DC conversion primary branch and is connected to one end of the primary side of the second high-frequency isolation transformer. The emitter of the seventh IGBT serves as the other voltage conversion terminal of the second DC conversion primary branch, and the emitter of the seventh IGBT is connected to the other end of the primary side of the second high-frequency isolation transformer.

[0014] As a further optimization, the second DC conversion secondary branch includes a fifth diode, a sixth diode, a seventh diode, an eighth diode, and a second inductor;

[0015] One end of the secondary side of the second high-frequency isolation transformer is respectively connected to the anode of the fifth diode and the cathode of the sixth diode, and the other end is respectively connected to the anode of the seventh diode and the cathode of the eighth diode. The cathodes of the fifth diode and the seventh diode are both connected to one end of the second inductor, and the other end of the second inductor serves as a parallel connection end to the secondary side branch of the first DC conversion. The anodes of the sixth diode and the eighth diode are connected and serve as another parallel connection end to the secondary side branch of the first DC conversion.

[0016] As a further optimization, the secondary side branch of the first DC conversion includes a first diode, a second diode, a third diode, a fourth diode, a first inductor, and a fifth capacitor;

[0017] One end of the secondary side of the first high-frequency isolation transformer is respectively connected to the anode of the first diode and the cathode of the second diode, and the other end is respectively connected to the anode of the third diode and the cathode of the fourth diode. The cathodes of the first diode and the third diode are both connected to one end of the first inductor, the other end of the first inductor is connected to a parallel connection end, the anodes of the second diode and the fourth diode are connected to another parallel connection end, one parallel connection end is connected to one end of the fifth capacitor, and the other parallel connection end is connected to the other end of the fifth capacitor. The two ends of the fifth capacitor serve as the two output ends of the DC conversion branch.

[0018] The beneficial effects of the present utility model are as follows: Through the above-mentioned DC conversion circuit, the input of 1500Vdc can be completed through two DC conversion primary side branches, two DC conversion secondary side branches, and two high-frequency isolation transformers, and it is not necessary to set separate control logics for each IGBT. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the circuit composition structure of a DC conversion circuit in an embodiment of the present utility model.

[0020] Among them, 101 is the primary branch of the first DC conversion, 102 is the secondary branch of the first DC conversion, 103 is the primary branch of the second DC conversion, 104 is the secondary branch of the second DC conversion, EUS+ is the positive pole of the DC voltage source, EUS- is the negative pole of the DC voltage source, C1 is the first capacitor, C2 is the second capacitor, C3 is the third capacitor, C4 is the fourth capacitor, C5 is the fifth capacitor, L1 is the first inductor, L2 is the second inductor, T1 is the first high-frequency isolation transformer, T2 is the second high-frequency isolation transformer, IGBT1 is the first IGBT, IGBT2 is the second IGBT, IGBT3 is the third IGBT, IGBT4 is the fourth IGBT, IGBT5 is the fifth IGBT, IGBT6 is the sixth IGBT, IGBT7 is the seventh IGBT, IGBT8 is the eighth IGBT, Vout+ is the positive output terminal of the DC conversion circuit, and Vout- is the negative output terminal of the DC conversion circuit. Specific embodiments

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are some, but not all, of the embodiments of the present utility model. Usually, the components of the embodiments of the present utility model described and illustrated herein can be arranged and designed in various different configurations. Embodiment

[0022] What this embodiment provides is a DC conversion circuit. The schematic diagram of its circuit composition structure is shown in Figure 1 , among which, the circuit includes:

[0023] The primary branch 101 of the first DC conversion, the secondary branch 102 of the first DC conversion, the primary branch 103 of the second DC conversion, the secondary branch 104 of the second DC conversion, the first high-frequency isolation transformer T1, and the second high-frequency isolation transformer T2;

[0024] The voltage input terminal of the primary branch 101 of the first DC conversion is used to connect the positive pole EUS+ of the DC voltage source. The voltage conversion terminal of the primary branch 101 of the first DC conversion is connected to the primary side of the first high-frequency isolation transformer T1. The voltage output terminal of the primary branch 101 of the first DC conversion is connected to a voltage input terminal of the primary branch 103 of the second DC conversion. The voltage conversion terminal of the primary branch 103 of the second DC conversion is connected to the primary side of the second high-frequency isolation transformer T2. The other voltage input terminal of the primary branch 103 of the second DC conversion is used to connect the negative pole EUS- of the DC voltage source;

[0025] The secondary side of the second high-frequency isolation transformer T2 is connected to the second DC conversion secondary branch 104, and the secondary side of the first high-frequency isolation transformer T1 is connected to the first DC conversion secondary branch 102. After the second DC conversion secondary branch 104 and the first DC conversion secondary branch 102 are connected in parallel, two output terminals of the DC conversion circuit are obtained, namely the positive output terminal Vout+ and the negative output terminal Vout-, which are used to output the output voltage corresponding to the DC voltage source.

[0026] In this embodiment, for the first DC conversion primary branch 101 and the second DC conversion primary branch 103, they can respectively share two 750Vdc in 1500Vdc. When 1500Vdc is input as the DC voltage source, after the 750Vdc voltage drop of the first DC conversion primary branch 101, the remaining 750Vdc is input to the second DC conversion primary branch 103. The first DC conversion secondary branch 102 transforms the voltage of the first DC conversion primary branch 101 through the first high-frequency isolation transformer T1, and the second DC conversion secondary branch 104 transforms the voltage of the second DC conversion primary branch 103 through the second high-frequency isolation transformer T2. Finally, the two DC conversion secondary branches are connected in parallel as the output of the entire DC conversion circuit, thereby realizing the DC conversion of two 750Vdc respectively.

[0027] It should be noted that only eight IGBTs are used in this embodiment, namely the first IGBT, the second IGBT, the third IGBT, the fourth IGBT, the fifth IGBT, the sixth IGBT, the seventh IGBT, and the eighth IGBT, which are respectively represented as IGBT1, IGBT2, IGBT3, IGBT4, IGBT5, IGBT6, IGBT7, and IGBT8. In the following description of the specific circuit in this embodiment, IGBT1 is used to represent the first IGBT, and the representation methods of the remaining IGBTs are similar.

[0028] Specifically, the first DC conversion primary branch 101 may include a first capacitor C1, a third capacitor C3, IGBT1, GBT2, IGBT3, and IGBT4;

[0029] One end of the first capacitor C1 serves as the voltage input terminal of the first DC conversion primary branch 101, and the other end serves as the voltage output terminal of the first DC conversion primary branch 101. The collectors of IGBT1 and IGBT3 are both connected to one end of the first capacitor C1. The emitter of IGBT1 is connected to the collector of IGBT2, the emitter of IGBT3 is connected to the collector of IGBT4, and the emitters of IGBT2 and IGBT4 are both connected to the other end of the first capacitor C1. The emitter of IGBT2 serves as the voltage output terminal of the first DC conversion primary branch 101. One end of the third capacitor C3 is connected to the emitter of IGBT1, and the other end serves as a voltage conversion terminal of the first DC conversion primary branch 101, connecting to one end of the primary side of the first high-frequency isolation transformer T1. The emitter of IGBT3 serves as another voltage conversion terminal of the first DC conversion primary branch 101, and the emitter of IGBT3 is connected to the other end of the primary side of the first high-frequency isolation transformer T1.

[0030] It should be noted that the second DC conversion primary branch 103 may include a second capacitor C2, IGBT5, IGBT6, IGBT7, IGBT8, and a fourth capacitor C4;

[0031] One end of the second capacitor C2 serves as a voltage input terminal of the second DC conversion primary branch 103, connecting to the emitter of IGBT2. The collectors of IGBT5 and IGBT7 are both connected to one end of the second capacitor C2. The emitter of IGBT5 is connected to the collector of IGBT6, the emitter of IGBT7 is connected to the collector of IGBT8, and the emitters of IGBT6 and IGBT8 are both connected to the other end of the second capacitor C2. The other end of the second capacitor C2 serves as another voltage input terminal of the second DC conversion primary branch 103, for connecting to the negative pole of the DC voltage source. One end of the fourth capacitor C4 is connected to the emitter of IGBT5, and the other end serves as a voltage conversion terminal of the second DC conversion primary branch 103, connecting to one end of the primary side of the second high-frequency isolation transformer T2. The emitter of IGBT7 serves as another voltage conversion terminal of the second DC conversion primary branch 103, and the emitter of IGBT7 is connected to the other end of the primary side of the second high-frequency isolation transformer T2.

[0032] In this embodiment, the second DC conversion secondary branch 104 may include a fifth diode D5, a sixth diode D6, a seventh diode D7, an eighth diode D8, and a second inductor L2;

[0033] One end of the secondary side of the second high-frequency isolation transformer T2 is respectively connected to the anode of the fifth diode D5 and the cathode of the sixth diode D6, and the other end is respectively connected to the anode of the seventh diode D7 and the cathode of the eighth diode D8. The cathodes of the fifth diode D5 and the seventh diode D7 are both connected to one end of the second inductor L2. The other end of the second inductor L2 serves as a parallel connection end connected to the secondary side branch 102 of the first DC conversion. The anodes of the sixth diode D6 and the eighth diode D8 are connected and serve as another parallel connection end connected to the secondary side branch 102 of the first DC conversion.

[0034] In this embodiment, the secondary side branch of the first DC conversion may include a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a first inductor L1, and a fifth capacitor C5.

[0035] One end of the secondary side of the first high-frequency isolation transformer T1 is respectively connected to the anode of the first diode D1 and the cathode of the second diode D2, and the other end is respectively connected to the anode of the third diode D3 and the cathode of the fourth diode D4. The cathodes of the first diode D1 and the third diode D3 are both connected to one end of the first inductor L1. The other end of the first inductor L1 is connected to a parallel connection end. The anodes of the second diode D2 and the fourth diode D4 are connected to another parallel connection end. One parallel connection end is connected to one end of the fifth capacitor C5, and the other parallel connection end is connected to the other end of the fifth capacitor C5. Both ends of the fifth capacitor C5 serve as the two output ends of the DC conversion branch.

[0036] In the actual application process, when controlling IGBT1 and IGBT4 to conduct simultaneously and IGBT2 and IGBT3 to turn off simultaneously, the input of the primary side of the high-frequency isolation transformer T1 is a positive voltage, and the output of the secondary side is also a positive voltage, which is a positive voltage after passing through the fast recovery diodes D1 and D4; when controlling IGBT1 and IGBT4 to turn off simultaneously and IGBT2 and IGBT3 to conduct simultaneously, the input of the primary side of the high-frequency isolation transformer T1 is a negative voltage, and the output of the secondary side is also a negative voltage, which is a positive voltage after passing through the fast recovery diodes D2 and D3; when controlling IGBT1, IGBT2, IGBT3, and IGBT4 to turn off simultaneously, the input of the primary side of the high-frequency isolation transformer T1 is 0, and the output of the secondary side is also 0; finally, through the filter inductor L1 and the capacitor C5, the pulsed DC voltage is filtered to form a smooth DC voltage.

[0037] Here, when IGBT5 and IGBT8 are turned on simultaneously and IGBT6 and IGBT7 are turned off simultaneously, the input of the primary side of the high-frequency isolation transformer T2 is a positive voltage, and the output of the secondary side is also a positive voltage. After passing through the fast-recovery diodes D5 and D8, it is a positive voltage. When IGBT5 and IGBT8 are turned off simultaneously and IGBT6 and IGBT7 are turned on simultaneously, the input of the primary side of the high-frequency isolation transformer T2 is a negative voltage, and the output of the secondary side is also a negative voltage. After passing through the fast-recovery diodes D6 and D7, it is a positive voltage. When IGBT5, IGBT6, IGBT7, and IGBT8 are turned off simultaneously, the input of the primary side of the high-frequency isolation transformer T2 is 0, and the output of the secondary side is also 0. Finally, through the filter inductor L2 and the capacitor C5, the pulsed DC voltage is filtered to form a smooth DC voltage.

[0038] Among them, IGBT1 and IGBT5, IGBT2 and IGBT6, IGBT3 and IGBT7, IGBT4 and IGBT8 are controlled synchronously to maintain the voltage balance of the bus support capacitors C1 and C2. Therefore, only 4 groups of drive pulses are required to control 8 IGBTs.

[0039] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A DC conversion circuit, characterized in that, Comprising: A first DC conversion primary branch, a first DC conversion secondary branch, a second DC conversion primary branch, a second DC conversion secondary branch, a first high-frequency isolation transformer, and a second high-frequency isolation transformer; The voltage input end of the first DC conversion primary branch is used to connect to the positive pole of a DC voltage source. The voltage conversion end of the first DC conversion primary branch is connected to the primary side of the first high-frequency isolation transformer. The voltage output end of the first DC conversion primary branch is connected to a voltage input end of the second DC conversion primary branch. The voltage conversion end of the second DC conversion primary branch is connected to the primary side of the second high-frequency isolation transformer. The other voltage input end of the second DC conversion primary branch is used to connect to the negative pole of the DC voltage source; The secondary side of the second high-frequency isolation transformer is connected to the second DC conversion secondary branch. The secondary side of the first high-frequency isolation transformer is connected to the first DC conversion secondary branch. The second DC conversion secondary branch and the first DC conversion secondary branch are connected in parallel to obtain two output ends of the DC conversion circuit, which are used to output an output voltage corresponding to the DC voltage source.

2. The DC conversion circuit according to claim 1, characterized in that, The first DC conversion primary branch includes a first capacitor, a third capacitor, a first IGBT, a second IGBT, a third IGBT, and a fourth IGBT; One end of the first capacitor serves as the voltage input end of the first DC conversion primary branch, and the other end serves as the voltage output end of the first DC conversion primary branch. The collectors of the first IGBT and the third IGBT are both connected to one end of the first capacitor. The emitter of the first IGBT is connected to the collector of the second IGBT. The emitter of the third IGBT is connected to the collector of the fourth IGBT. The emitters of the second IGBT and the fourth IGBT are both connected to the other end of the first capacitor. The emitter of the second IGBT serves as the voltage output end of the first DC conversion primary branch. One end of the third capacitor is connected to the emitter of the first IGBT, and the other end serves as a voltage conversion end of the first DC conversion primary branch, connecting to one end of the primary side of the first high-frequency isolation transformer. The emitter of the third IGBT serves as the other voltage conversion end of the first DC conversion primary branch, and the emitter of the third IGBT is connected to the other end of the primary side of the first high-frequency isolation transformer.

3. The DC conversion circuit according to claim 2, characterized in that, The second DC conversion primary branch includes a second capacitor, a fifth IGBT, a sixth IGBT, a seventh IGBT, an eighth IGBT, and a fourth capacitor; One end of the second capacitor serves as a voltage input terminal of the primary branch of the second DC conversion, connecting to the emitter of the second IGBT. The collectors of the fifth IGBT and the seventh IGBT are both connected to one end of the second capacitor. The emitter of the fifth IGBT is connected to the collector of the sixth IGBT. The emitter of the seventh IGBT is connected to the collector of the eighth IGBT. The emitters of the sixth IGBT and the eighth IGBT are both connected to the other end of the second capacitor. The other end of the second capacitor serves as another voltage input terminal of the primary branch of the second DC conversion, for connecting to the negative pole of the DC voltage source. One end of the fourth capacitor is connected to the emitter of the fifth IGBT, and the other end serves as a voltage conversion terminal of the primary branch of the second DC conversion, connecting to one end of the primary side of the second high-frequency isolation transformer. The emitter of the seventh IGBT serves as another voltage conversion terminal of the primary branch of the second DC conversion, and the emitter of the seventh IGBT is connected to the other end of the primary side of the second high-frequency isolation transformer.

4. A DC conversion circuit according to claim 3, wherein, The secondary branch of the second DC conversion includes a fifth diode, a sixth diode, a seventh diode, an eighth diode, and a second inductor; One end of the secondary side of the second high-frequency isolation transformer is respectively connected to the anode of the fifth diode and the cathode of the sixth diode, and the other end is respectively connected to the anode of the seventh diode and the cathode of the eighth diode. The cathodes of the fifth diode and the seventh diode are both connected to one end of the second inductor. The other end of the second inductor serves as a parallel connection end for connecting to the secondary branch of the first DC conversion. The anodes of the sixth diode and the eighth diode are connected, and serve as another parallel connection end for connecting to the secondary branch of the first DC conversion.

5. A DC conversion circuit according to claim 4, characterized in that, The secondary branch of the first DC conversion includes a first diode, a second diode, a third diode, a fourth diode, a first inductor, and a fifth capacitor; One end of the secondary side of the first high-frequency isolation transformer is respectively connected to the anode of the first diode and the cathode of the second diode, and the other end is respectively connected to the anode of the third diode and the cathode of the fourth diode. The cathodes of the first diode and the third diode are both connected to one end of the first inductor. The other end of the first inductor is connected to a parallel connection end. The anodes of the second diode and the fourth diode are connected to another parallel connection end. One parallel connection end is connected to one end of the fifth capacitor, and the other parallel connection end is connected to the other end of the fifth capacitor. The two ends of the fifth capacitor serve as the two output terminals of the DC conversion branch.

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