A DC-DC conversion circuit, DC-DC converter and charging module

Abstract

The present invention discloses a DC-DC conversion circuit, a DC-DC converter and a charging module. The present invention obtains a DC-DC conversion circuit with winding switching by adding multiple switch units to multiple secondary windings or multiple primary windings, and connects part of the secondary windings or part of the primary windings in series with the compensation inductor, thereby realizing compensation of the resonant inductor parameters, so that the resonant inductance and the resonant frequency of the DC-DC conversion circuit remain unchanged during winding switching, thereby effectively improving the conversion efficiency of the DC-DC conversion circuit with winding switching and the DC-DC converter.

Description

Technical Field

[0001] The present invention belongs to the technical field of power management, and in particular relates to a DC-DC conversion circuit, a DC-DC converter and a charging module. Background Art

[0002] LLC circuit (resonant conversion circuit) is a highly efficient DC-DC conversion circuit widely used in power management and conversion. In order to achieve higher conversion efficiency, the circuit that makes LLC circuit work at a fixed operating frequency is called DCX circuit. In order to reduce the size of the device and improve the conversion efficiency of the DCX circuit, the resonant inductance of the DCX circuit is usually designed to be relatively small, or the leakage inductance of the transformer is directly used as the resonant inductor to reduce the size of the device and improve the conversion efficiency.

[0003] In order to improve the gain, a winding switching function is added to the DCX circuit. Due to the limitation of the transformer winding structure, the leakage inductance of the transformer is difficult to be the same in different winding switching states. This change in leakage inductance has a great impact on the resonant frequency, which in turn affects the conversion efficiency of the DC-DC converter and hinders the DC-DC converter from achieving efficient conversion. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a DC-DC conversion circuit, a DC-DC converter and a charging module, aiming to solve the problem of low conversion efficiency of the DC-DC converter due to leakage inductance changes in the related art.

[0005] To solve the above technical problems, the present invention is implemented as follows: a DC-DC conversion circuit includes a transformer, a primary resonant conversion circuit and a secondary resonant conversion circuit;

[0006] The transformer comprises at least one primary winding and a plurality of secondary windings connected in series, wherein the primary winding is magnetically coupled with each of the secondary windings;

[0007] The primary resonant conversion circuit comprises a first rectifier-inverter unit and a first resonant circuit; the first rectifier-inverter unit is used to convert the received primary DC signal into a primary AC signal to the first end of the first resonant circuit, the second end of the first resonant circuit is electrically connected to the first end of the primary winding, and the second end of the primary winding is electrically connected to the first rectifier-inverter unit;

[0008] The secondary resonant conversion circuit includes at least one compensation inductor, a second rectifying and inverting unit, and a switching unit corresponding to the plurality of secondary windings one by one; each of the secondary windings is connected in series with the corresponding switching unit to form a corresponding branch, at least one of the branches is connected in series with a compensation inductor, and each of the branches is used to output a secondary AC signal to the second rectifying and inverting unit, and the second rectifying and inverting unit is used to convert the secondary AC signal into a secondary DC signal.

[0009] Furthermore, the number of the compensation inductors is less than the number of the secondary windings.

[0010] Furthermore, the transformer includes two secondary windings connected in series, the secondary resonant circuit includes a compensation inductor and two switch units corresponding to the two secondary windings one by one, the two secondary windings are connected in series with the corresponding switch units to form corresponding branches, and the compensation inductor is connected in series to one of the branches.

[0011] Furthermore, the secondary side resonant conversion circuit also includes a second resonant circuit, defining that the branches connected in series with the compensation inductor are all first branches, defining that the branches except the first branch among the multiple branches are all second branches, and the two ends of the second resonant circuit are connected in series between the second branch and the second rectifier inverter unit.

[0012] The present invention also provides a DC-DC conversion circuit, including a transformer, a primary-side resonant conversion circuit and a secondary-side resonant conversion circuit;

[0013] The transformer comprises a plurality of primary windings and a plurality of secondary windings, each of the primary windings being magnetically coupled with each of the secondary windings;

[0014] The primary resonant conversion circuit comprises a first rectifying and inverting unit, a first resonant circuit, at least one compensation inductor, and a switch unit corresponding to the plurality of primary windings one by one; each of the primary windings is connected in series with the corresponding switch unit to form a corresponding branch, each of the compensation inductors is connected in series with one of the branches, the first rectifying and inverting unit is used to convert the received primary DC signal into a primary AC signal to the first end of the first resonant circuit, the second end of the first resonant circuit is electrically connected to the first ends of the plurality of branches, and the second ends of the plurality of branches are electrically connected to the first rectifying and inverting unit;

[0015] The secondary resonant conversion circuit includes a second rectifier and inverter unit, and the plurality of secondary windings are used to output secondary AC signals to the second rectifier and inverter unit, and the second rectifier and inverter unit is used to convert the secondary AC signals into secondary DC signals.

[0016] Furthermore, the number of the compensating inductors is less than the number of the primary windings.

[0017] The present invention also provides a DC-DC converter, comprising the DC-DC conversion circuit as described above.

[0018] The present invention also provides a charging module, comprising the DC-DC converter as described above.

[0019] Compared with the prior art, the DC-DC conversion circuit, DC-DC converter and charging module in the present invention have the following beneficial effects: the present invention obtains a DC-DC conversion circuit with winding switching by adding multiple switch units to multiple secondary windings or multiple primary windings, and connects part of the secondary windings or part of the primary windings in series with the compensation inductor, thereby realizing compensation of the resonant inductor parameters, so that the resonant inductance and resonant frequency of the DC-DC conversion circuit remain unchanged during winding switching, thereby effectively improving the conversion efficiency of the DC-DC conversion circuit with winding switching and the DC-DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is an equivalent circuit diagram of a DC-DC conversion circuit in some embodiments of the present invention;

[0021] Figure 2 is an equivalent circuit diagram of a DC-DC conversion circuit in some embodiments of the present invention;

[0022] Figure 3 is an equivalent circuit diagram of a DC-DC conversion circuit in some embodiments of the present invention;

[0023] Figure 4 is an equivalent circuit diagram of a DC-DC conversion circuit in some embodiments of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0025] In the description of the present disclosure, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the feature. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0026] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0027] In addition, in order to better illustrate the present disclosure, numerous specific details are given in the following specific embodiments. It should be understood by those skilled in the art that the present disclosure can also be implemented without certain specific details, and the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present disclosure.

[0028] In order to meet the charging needs of various scenarios, charging module products have higher and higher requirements for output voltage range and conversion efficiency. For example, in the field of charging for new energy vehicles, the output voltage range of the first-generation charging module is divided into 200-500V and 200-750V. These two output voltage ranges are respectively for private cars equipped with low-voltage batteries and buses and buses equipped with low-voltage batteries. The conversion efficiency of the charging module is about 95% to 96%. With the increase in demand and the advancement of technology, the output voltage range of the second-generation charging module has been expanded to 200V to 1000V, which can meet most charging needs, and the charging efficiency has been continuously improved to 96% to 97%. However, due to the limitations of the circuit topology in terms of charging efficiency gain, the output end of the DC-DC conversion circuit in the charging module usually needs to be designed as series-parallel switching, transformer winding turns ratio switching, or a combination of the above two switching methods to achieve higher conversion gain.

[0029] However, due to the structural limitations of the transformer windings, the leakage inductance of the transformer cannot be the same when the windings are switched, which has a great impact on the resonant frequency of the DC-DC conversion circuit, greatly reducing the conversion efficiency of the DC-DC converter, and even destroying the software switch implementation conditions for the transformer winding switching, hindering the DC-DC converter from performing efficient conversion.

[0030] Therefore, the present invention provides a DC-DC conversion circuit, a DC-DC converter and a charging module, which can solve the problem of low conversion efficiency of the DC-DC conversion circuit with winding switching.

[0031] The DC-DC conversion circuit provided in this embodiment maintains the resonance parameters in different winding switching modes unchanged based on the compensation inductance. The DC-DC conversion circuit can be applied to various circuits including but not limited to LLC circuits, CLLC bidirectional conversion circuits, LLC circuits with mixed winding switching and series-parallel connection, three-phase resonant circuits, and the like.

[0032] In the first aspect of this embodiment, Figure 1 As shown, a DC-DC conversion circuit includes a transformer, a primary resonant conversion circuit and a secondary resonant conversion circuit;

[0033] The transformer comprises at least one primary winding and a plurality of secondary windings connected in series, wherein the primary winding is magnetically coupled to each of the secondary windings;

[0034] The primary resonant conversion circuit includes a first rectifier-inverter unit and a first resonant circuit; the first rectifier-inverter unit is used to convert the received primary DC signal into a primary AC signal to the first end of the first resonant circuit, the second end of the first resonant circuit is electrically connected to the first end of the primary winding, and the second end of the primary winding is electrically connected to the first rectifier-inverter unit;

[0035] The secondary resonant conversion circuit includes at least one compensation inductor, a second rectifier inverter unit, and switch units corresponding to multiple secondary windings one by one; each secondary winding is connected in series with the corresponding switch unit to form a corresponding branch, at least one branch is connected in series with a compensation inductor, and each branch is used to output a secondary AC signal to the second rectifier inverter unit, and the second rectifier inverter unit is used to convert the secondary AC signal into a secondary DC signal.

[0036] In this embodiment, a DC-DC conversion circuit with winding switching is obtained by adding multiple switching units to multiple secondary windings or multiple primary windings, and part of the secondary windings or part of the primary windings are connected in series with the compensation inductor to achieve compensation of the resonant inductance parameters, so that the resonant inductance and resonant frequency of the DC-DC conversion circuit remain unchanged during winding switching, effectively improving the conversion efficiency of the DC-DC conversion circuit with winding switching and the DC-DC converter.

[0037] Preferably, the first resonant circuit includes a first resonant inductor Lr and a first resonant capacitor Cr, and the first resonant inductor Lr, the first resonant capacitor Cr and the primary winding Np are connected in series.

[0038] Furthermore, the number of the compensation inductors is less than the number of the secondary windings.

[0039] Furthermore, the transformer includes two secondary windings connected in series, the secondary resonant circuit includes a compensation inductor and two switch units corresponding to the two secondary windings one by one, the two secondary windings are connected in series with the corresponding switch units to form corresponding branches, and the compensation inductor is connected in series to one branch.

[0040] Specifically, Figure 1 As shown, in the first embodiment, the transformer includes a first secondary winding Ns1 and a second secondary winding Ns2, the secondary resonant circuit includes a compensation inductor Lcp, and a first switch unit K1 and a second switch unit K2 corresponding to the first secondary winding Ns1 and the second secondary winding Ns2, respectively, and the compensation inductor Lcp is connected in series in a branch formed by the first secondary winding Ns1 and the first switch unit K1.

[0041] In the above embodiment, the working principle of the DC-DC conversion circuit is:

[0042] The DC-DC conversion circuit has two operating modes, namely a first operating mode and a second operating mode.

[0043] In the first working mode, the first switch unit K1 is closed, the second switch unit K2 is opened, the first secondary winding Ns1 and the second secondary winding Ns2 are connected in series, the first secondary winding Ns1 and the second secondary winding Ns2 serve together as the secondary winding of the transformer, and the transformer turns ratio In the first working mode, the primary leakage inductance of the corresponding transformer is Lk1.

[0044] In the second working mode, the first switch unit K1 is disconnected, the second switch unit K2 is closed, the first secondary winding Ns1 is not connected to the circuit, and the second secondary winding Ns2 serves as the secondary winding of the transformer. At this time, the transformer turns ratio In the second working mode, the primary leakage inductance of the corresponding transformer is Lk2. Usually, Lk2>Lk1.

[0045] It should be understood that the resonant frequency of the DC-DC converter circuit Where Lr is the resonant inductor. Compensation inductor Lcp = (Lk2-Lk1)*Nps1 2 .

[0046] In the first working mode, a compensation inductor is connected to the DC-DC conversion circuit, and the resonant inductor Lr is the sum of the primary leakage inductance Lk1 and the primary equivalent inductance of the compensation inductor Lcp, that is,

[0047] In the second working mode, no compensation inductor is connected to the DC-DC conversion circuit, and the resonant inductor Lr is the transformer leakage inductance, that is, Lr=Lk2.

[0048] Therefore, in the first working mode and the second working mode, the resonant inductance Lr remains unchanged, and when the secondary winding is switched, the resonant frequency of the DC-DC conversion circuit remains unchanged, both of which are In this way, the DC-DC conversion circuit achieves that the resonance parameters remain unchanged when multiple windings are switched, and thus the DC-DC conversion circuit can achieve high-efficiency conversion in the full range.

[0049] like Figure 2 As shown, in the second embodiment, the secondary side resonant conversion circuit also includes a second resonant circuit, and the branches connected in series with the compensation inductor are defined as the first branch, and the branches except the first branch in the multiple branches are defined as the second branch, and the two ends of the second resonant circuit are connected in series between each second branch and the second rectifier inverter unit.

[0050] Specifically, the second resonant circuit includes a second resonant inductor Lrs and a second resonant capacitor Crs, and the second secondary winding NS2, the second resonant inductor Lrs and the second resonant capacitor Crs are connected in series in sequence.

[0051] The working principle of the DC-DC conversion circuit of this embodiment is similar to that of the first embodiment, the only difference being that the DC-DC conversion circuit in this embodiment is a CLLC bidirectional conversion circuit, and thus the working principle of the second embodiment is not described in detail here.

[0052] like Figure 3 As shown, in the third embodiment, a DC-DC conversion circuit is provided, including a transformer, a primary resonant conversion circuit and a secondary resonant conversion circuit;

[0053] The transformer includes a plurality of primary windings and a plurality of secondary windings connected in series, each primary winding being magnetically coupled with each secondary winding;

[0054] The primary resonant conversion circuit includes a first rectifier-inverter unit, a first resonant circuit, at least one compensation inductor, and a switch unit corresponding to a plurality of primary windings one by one; each primary winding is connected in series with a corresponding switch unit to form a corresponding branch, each compensation inductor is connected in series to a branch, the first rectifier-inverter unit is used to convert a received primary DC signal into a primary AC signal to a first end of the first resonant circuit, the second end of the first resonant circuit is electrically connected to the first ends of the plurality of branches, and the second ends of the plurality of branches are electrically connected to the first rectifier-inverter unit;

[0055] The secondary resonant conversion circuit includes a second rectifier and inverter unit, and the multiple secondary windings are used to output secondary AC signals to the second rectifier and inverter unit, and the second rectifier and inverter unit is used to convert the secondary AC signals into secondary DC signals.

[0056] Furthermore, the number of compensation inductors is less than the number of primary windings.

[0057] This embodiment illustrates a DC-DC conversion circuit with a mixture of winding switching and series-parallel switching. Specifically, the primary resonant conversion circuit includes a first rectifier inverter unit, a first resonant circuit, a compensation inductor Lcp, a first switch unit K1, and a second switch unit K2; the transformer includes two primary windings and two secondary windings, each primary winding is connected in series with the first switch unit K1 and the second switch unit K2 to form a corresponding branch, and the compensation inductor Lcp is connected in series with the first switch unit K1;

[0058] The secondary resonant conversion circuit comprises two second rectifying and inverting units, and the two second rectifying and inverting units are respectively connected in parallel to the two secondary windings.

[0059] The third embodiment has a similar working principle to the first embodiment. Similarly, the DC-DC conversion circuit in the third embodiment includes two working modes. When one of the first switch unit K1 and the second switch unit K2 is closed, the other of the first switch unit K1 and the second switch unit K2 is disconnected, thereby realizing winding switching of the DC-DC conversion circuit. At the same time, the compensation inductor Lcp can realize compensation of the resonance parameters in the working mode in which the first switch unit K1 is closed. Because its working principle is similar to that of the first embodiment, it is not repeated here.

[0060] It can be understood that the DC-DC conversion circuit provided by the present invention can also be applied to a three-phase resonant circuit. Figure 4 In a fourth embodiment, the DC-DC conversion circuit includes a transformer, a primary resonant conversion circuit, and a secondary resonant conversion circuit;

[0061] The transformer includes a plurality of primary windings and a plurality of secondary windings, the primary windings are magnetically coupled with each secondary winding, and the plurality of secondary windings are connected in series in pairs to form a plurality of third secondary windings. Figure 4 As shown, the secondary winding N2 and the secondary winding N3 are connected in series to form a group of third secondary windings, and the transformer includes multiple groups of third secondary windings formed by the secondary windings N2 and N3 connected in series.

[0062] The primary resonant conversion circuit includes a first rectifier-inverter unit and a first resonant circuit corresponding to a plurality of primary windings one by one; the first rectifier-inverter unit is used to convert a received primary DC signal into a primary AC signal to a first end of the first resonant circuit, a second end of the first resonant circuit is electrically connected to a first end of the primary winding, and second ends of the primary windings are electrically connected;

[0063] The secondary resonant conversion circuit includes a compensation inductor corresponding to the third secondary winding, a second rectifier inverter unit and a plurality of switch units; in each third secondary winding, two secondary windings are connected in series with the corresponding switch unit to form a corresponding branch, and a compensation inductor is connected in series to one branch;

[0064] Define a branch with a compensation inductor connected in series among the multiple branches as a first branch, define branches other than the first branch among the multiple branches as second branches, connect multiple first branches in parallel, and connect multiple second branches in parallel;

[0065] Each branch is used to output a secondary side AC signal to the second rectifying and inverting unit, and the second rectifying and inverting unit is used to convert the secondary side AC signal into a secondary side DC signal.

[0066] It can be understood that the working principle of the DC-DC conversion circuit in the fourth embodiment is still similar to the working principle of the DC-DC conversion circuit in the first embodiment. Specifically, Figure 4As shown, the switch units K1 and K2 are closed or opened at the same time, and the switch units K3 and K4 are closed or opened at the same time. When the switch units K1 and K2 are closed, the switch units K3 and K4 are opened, and when the switch units K1 and K2 are opened, the switch units K3 and K4 are closed, so as to realize the winding switching of the DC-DC conversion circuit in this embodiment.

[0067] It should be noted that this embodiment is only a preferred embodiment, and the switch units in the first to fifth embodiments are not limited to the number and type shown in the figure, and those skilled in the art can select a suitable switch unit according to actual application requirements. In some embodiments, the switch unit can be a mechanical switch, a semiconductor switch, or a combination circuit consisting of at least one mechanical switch and at least one semiconductor switch in parallel. Those skilled in the art can select a suitable mechanical switch and semiconductor switch according to actual application requirements, such as: a single-pole single-throw switch can be selected for the mechanical switch, and a MOS or IGBT can be selected for the semiconductor switch.

[0068] In addition, in this embodiment, the secondary windings are used to output secondary AC signals to the second rectifier inverter unit, and the second rectifier inverter unit is used to convert the secondary AC signals into secondary DC signals. It can be understood that the above-mentioned multiple embodiments only provide a preferred solution of connecting multiple secondary windings in series, and multiple secondary windings can be connected in series or in parallel.

[0069] A second aspect of this embodiment provides a DC-DC converter, including the DC-DC conversion circuit as described above.

[0070] A third aspect of this embodiment further provides a charging module, comprising the DC-DC converter as described above.

[0071] The charging module includes at least one DC-DC converter, and multiple DC-DC converters can be connected in series or in parallel to form a charging module. In practical applications, multiple charging modules can also be combined in series or in parallel.

[0072] The second aspect and the third aspect of this embodiment have been described accordingly in the first part of this embodiment, correspond to other parts of this embodiment, and can produce similar technical effects, so they will not be repeated here.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A DC-DC conversion circuit, characterized in that: It includes a transformer, a primary-side resonant conversion circuit and a secondary-side resonant conversion circuit; The transformer comprises at least one primary winding and a plurality of secondary windings connected in series, wherein the primary winding is magnetically coupled with each of the secondary windings; The primary resonant conversion circuit comprises a first rectifier-inverter unit and a first resonant circuit; the first rectifier-inverter unit is used to convert the received primary DC signal into a primary AC signal to the first end of the first resonant circuit, the second end of the first resonant circuit is electrically connected to the first end of the primary winding, and the second end of the primary winding is electrically connected to the first rectifier-inverter unit; The secondary resonant conversion circuit includes at least one compensation inductor, a second rectifying and inverting unit, and a switching unit corresponding to the plurality of secondary windings one by one; each of the secondary windings is connected in series with the corresponding switching unit to form a corresponding branch, at least one of the branches is connected in series with a compensation inductor, and each of the branches is used to output a secondary AC signal to the second rectifying and inverting unit, and the second rectifying and inverting unit is used to convert the secondary AC signal into a secondary DC signal.

2. The DC-DC conversion circuit according to claim 1, characterized in that: The number of the compensation inductors is less than the number of the secondary windings.

3. The DC-DC conversion circuit according to claim 2, characterized in that: The transformer includes two secondary windings connected in series, the secondary resonant circuit includes a compensation inductor and two switch units corresponding to the two secondary windings one by one, the two secondary windings are connected in series with the corresponding switch units to form corresponding branches, and the compensation inductor is connected in series to one of the branches.

4. The DC-DC conversion circuit according to claim 1, characterized in that: The secondary side resonant conversion circuit also includes a second resonant circuit, which defines that the branches connected in series with the compensation inductor are all first branches, and that the branches except the first branch among the multiple branches are all second branches, and the two ends of the second resonant circuit are connected in series between the second branch and the second rectifier inverter unit.

5. A DC-DC conversion circuit, characterized in that: It includes a transformer, a primary-side resonant conversion circuit and a secondary-side resonant conversion circuit; The transformer comprises a plurality of primary windings and a plurality of secondary windings, each of the primary windings being magnetically coupled with each of the secondary windings; The primary resonant conversion circuit comprises a first rectifying and inverting unit, a first resonant circuit, at least one compensation inductor, and a switch unit corresponding to the plurality of primary windings one by one; each of the primary windings is connected in series with the corresponding switch unit to form a corresponding branch, each of the compensation inductors is connected in series with one of the branches, the first rectifying and inverting unit is used to convert the received primary DC signal into a primary AC signal to the first end of the first resonant circuit, the second end of the first resonant circuit is electrically connected to the first ends of the plurality of branches, and the second ends of the plurality of branches are electrically connected to the first rectifying and inverting unit; The secondary resonant conversion circuit includes a second rectifier and inverter unit, and the plurality of secondary windings are used to output secondary AC signals to the second rectifier and inverter unit, and the second rectifier and inverter unit is used to convert the secondary AC signals into secondary DC signals.

6. The DC-DC conversion circuit according to claim 5, characterized in that: The number of the compensation inductors is less than the number of the primary windings.

7. A DC-DC converter, characterized in that: The invention comprises the DC-DC conversion circuit as claimed in any one of claims 1 to 6.

8. A charging module, characterized in that: Comprising the DC-DC converter as claimed in claim 7.

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