Direct current converter and control method thereof

Abstract

The invention discloses a direct-current converter and a control method thereof, and relates to the field of power, the direct-current converter comprises a transformer, N inverter circuits and M rectifier circuits, a first transformer winding corresponding to each inverter circuit and a second transformer winding corresponding to each rectifier circuit are coupled on the same magnetic loop, the advantage that a cellular circuit can use a low-voltage device to reduce loss and improve switching frequency is maintained, and efficient and high-power-density energy conversion can be achieved. Meanwhile, a resonant impedance which is connected in series on a circuit between the second side of the inverter circuit and the first winding of the transformer and / or a circuit between the first side of the rectifier circuit and the second winding of the transformer is additionally arranged, and an inductive impedance is additionally arranged in a resonant cavity of the direct current converter. Therefore, the voltage gain range of the direct-current converter is expanded, the direct-current converter can realize the functions of voltage regulation and voltage stabilization, the output voltage of the direct-current converter can be flexibly regulated and controlled, and the application scene of the direct-current converter is expanded.

Description

Technical Field

[0001] The present invention relates to the field of electric power, and in particular to a direct current converter and a control method thereof. Background Art

[0002] In the fields of server power supply, direct current / direct current (DC / DC) converters are widely used. In order to reduce the device loss in high-voltage application scenarios, the current DC / DC converter can replace the traditional high-voltage devices by connecting low-voltage cell circuits in series composed of low-voltage devices. Any low-voltage cell circuit includes a bus capacitor, an inverter circuit or a rectifier circuit. Specifically, the input voltage of the DC / DC converter is shared by multiple bus capacitors connected in series on the input side. At the same time, an inverter circuit is connected after each bus capacitor, and the output side of the inverter circuit is connected to the input side of the rectifier circuit through a transformer. At the same time, the transformers of each low-voltage cell circuit are coupled to the same magnetic circuit, and each winding of the transformer shares the same magnetic flux, thereby achieving voltage balancing between each cell circuit. Therefore, the DC / DC converter in high-voltage application scenarios is realized by connecting low-voltage devices in series, so that the DC / DC converter has a lower on-resistance and can reduce the equivalent junction capacitance. Therefore, while reducing the conduction loss, it can push up the switching frequency of the converter, and realize the energy conversion of the converter with high efficiency and high power density. However, the current DC / DC converter composed of low-voltage cellular circuits cannot achieve output voltage regulation and voltage stabilization, and it is difficult to flexibly control the output voltage. Summary of the invention

[0003] The purpose of the present invention is to provide a DC converter and a control method thereof, by which an additional inductive impedance is added to the resonant cavity of the DC converter, thereby expanding the voltage gain range of the DC converter, enabling the DC converter to achieve voltage regulation and voltage stabilization functions, and flexibly regulating its own output voltage, thereby expanding the application scenarios of the DC converter.

[0004] To solve the above technical problems, the present invention provides a DC converter, comprising a transformer, N inverter circuits and M rectifier circuits, where N is a positive integer greater than 1 and M is a positive integer;

[0005] The transformer comprises N transformer first windings connected to N inverter circuits in one-to-one correspondence and M transformer second windings connected to M rectifier circuits in one-to-one correspondence, the first sides of the N inverter circuits are connected to each other as the first side of the DC converter, the second sides are connected in parallel with the corresponding transformer first windings, the first sides of the rectifier circuits are connected in parallel with the corresponding transformer second windings, and the second sides of the M rectifier circuits are connected to each other as the second side of the DC converter; all the transformer first windings and all the transformer second windings are coupled to the same magnetic circuit; wherein the first sides of the N inverter circuits and / or the second sides of the M rectifier circuits are connected in series with each other;

[0006] A resonant impedance is connected in series in the circuit between the second side of the inverter circuit and the first winding of the transformer and / or in the circuit between the first side of the rectifier circuit and the second winding of the transformer, and the inductive reactance of the resonant impedance is greater than the inductive reactance of the leakage inductance of the first winding of the transformer, and greater than the inductive reactance of the leakage inductance of the second winding of the transformer.

[0007] Optionally, the resonant impedance is a first inductor, a first end of the first inductor is connected to a first end of the second side of the inverter circuit, and a second end of the first inductor is connected to a first end of the first winding of the transformer.

[0008] Optionally, the N first inductors of the N inverter circuits are N inductor coils in the same coupled inductor.

[0009] Optionally, the resonant impedance includes:

[0010] A second inductor and a first capacitor are connected in series, wherein a first end of a circuit formed by connecting the second inductor and the first capacitor in series is connected to a first end of a second side of the inverter circuit, and a second end is connected to a first end of a first winding of the transformer.

[0011] Optionally, the resonant impedance includes:

[0012] a third inductor, a first end of which is connected to a first end of the second side of the inverter circuit;

[0013] A second capacitor, a first end of which is connected to a second end of the second inductor;

[0014] A fourth inductor has a first end connected to the second end of the second capacitor and the first end of the first winding of the transformer, and a second end connected to the second end of the second side of the inverter circuit and the second end of the first winding of the transformer.

[0015] Optionally, the resonant impedance includes:

[0016] a fifth inductor, a first end of which is connected to a first end of the second side of the inverter circuit;

[0017] a third capacitor, a first end of which is connected to the second end of the fifth inductor;

[0018] Sixth inductor;

[0019] A fourth capacitor has a first end connected to the second end of the third capacitor and the first end of the sixth inductor respectively, and a second end connected to the second end of the sixth inductor and the second end of the first winding of the transformer respectively.

[0020] Optionally, the first end of the first side of the first inverter circuit serves as the first end of the first side of the DC converter, the second end of the first side of the i-th inverter circuit is connected to the first end of the first side of the i+1-th inverter circuit, and the second end of the first side of the N-th inverter circuit serves as the second end of the first side of the DC converter; the first ends of the second sides of the M rectifier circuits are connected to each other and serve as the first end of the second side of the DC converter, and the second ends of the second sides of the M rectifier circuits are connected to each other and serve as the second end of the second side of the DC converter; i is a positive integer, and i<N. In order to solve the above technical problems, the present invention also provides a control method for a DC converter, which is applied to the DC converter as described above, and the control method for the DC converter includes:

[0021] Determining a current output voltage and a required voltage of the DC converter;

[0022] The control parameters of the switch tube in the DC converter are adjusted to control the output voltage of the DC converter to reach the required voltage.

[0023] Optionally, adjusting the control parameters of the switch tube in the DC converter includes:

[0024] Adjust the switching frequency and / or duty cycle of the switch tube in the DC converter.

[0025] Optionally, adjusting the control parameters of the switch tube in the DC converter includes:

[0026] Adjust the conduction timing of several switch tubes in the inverter circuit of the DC converter and / or the conduction timing of several switch tubes in the rectifier circuit.

[0027] The present invention provides a direct current converter and a control method thereof, comprising a transformer, N inverter circuits and M rectifier circuits, wherein the first winding of the transformer corresponding to each inverter circuit and the second winding of the transformer corresponding to each rectifier circuit are coupled to the same magnetic circuit, which can effectively realize the voltage balancing between the N inverter circuits, so that when a low-voltage cellular circuit composed of low-voltage devices is used to replace a high-voltage device, the advantage of the cellular circuit that can use low-voltage devices to reduce losses and increase switching frequency is maintained, which helps to realize energy conversion with high efficiency and high power density. At the same time, a resonant impedance is added to the circuit connected in series between the second side of the inverter circuit and the first winding of the transformer and / or the first side of the rectifier circuit and the second winding of the transformer, and an additional inductive impedance is added to the resonant cavity of the direct current converter, thereby realizing the expansion of the voltage gain range of the direct current converter, so that the direct current converter can realize the functions of voltage regulation and voltage stabilization, can flexibly regulate its own output voltage, and expand the application scenario of the direct current converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A schematic structural diagram of a DC converter provided by the present invention;

[0030] Figure 2 A schematic structural diagram of another DC converter provided by the present invention;

[0031] Figure 3 A schematic diagram of the structure of a first inverter circuit provided by the present invention;

[0032] Figure 4 A schematic diagram of the structure of a second inverter circuit provided by the present invention;

[0033] Figure 5 A schematic diagram of the structure of a first rectifier circuit provided by the present invention;

[0034] Figure 6 A schematic diagram of the structure of a second rectifier circuit provided by the present invention;

[0035] Figure 7 A schematic structural diagram of a third rectifier circuit provided by the present invention;

[0036] Figure 8 A schematic diagram of the construction method of the first resonant impedance provided by the present invention;

[0037] Fig. 9 A schematic diagram of a coupling mode of resonant impedances in a first N inverter circuit provided by the present invention;

[0038] Fig.10 A schematic diagram of a second resonant impedance structure provided by the present invention;

[0039] Fig.11 A schematic diagram of a coupling mode of resonant impedances in a second N inverter circuit provided by the present invention;

[0040] Fig.12 A schematic diagram of a third type of resonant impedance structure provided by the present invention;

[0041] Fig.13 A schematic diagram of a coupling mode of resonant impedances in a third N inverter circuit provided by the present invention;

[0042] Fig.14 A schematic diagram of the structure of a DC converter composed of a cellular LLC circuit provided by the present invention;

[0043] Fig.15 A schematic diagram of signal waveforms of a DC converter formed by a cellular LLC circuit provided by the present invention;

[0044] Fig.16 A schematic diagram of a fourth type of resonant impedance structure provided by the present invention;

[0045] Fig.17 A schematic diagram of the structure of a DC converter using an ISOP type circuit provided by the present invention;

[0046] Fig.18 A schematic diagram of the structure of a DC converter using an IPOS type circuit provided by the present invention;

[0047] Fig.19 A schematic diagram of the structure of a DC converter using an auxiliary winding to achieve cellular circuit coupling provided by the present invention;

[0048] Fig. 20 A schematic diagram of the structure of a cellular DAB circuit provided by the present invention;

[0049] Fig.21 A waveform diagram of a control signal and an output signal of a phase shift control method provided by the present invention. DETAILED DESCRIPTION

[0050] The core of the present invention is to provide a DC converter and a control method thereof, by adding an additional inductive impedance in the resonant cavity of the DC converter, thereby expanding the voltage gain range of the DC converter, enabling the DC converter to achieve voltage regulation and voltage stabilization functions, and to flexibly adjust its own output voltage, thereby expanding the application scenarios of the DC converter.

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of a DC converter provided by the present invention; To solve the above technical problems, the present invention provides a DC converter, including a transformer, N inverter circuits and M rectifier circuits, N is a positive integer greater than 1, and M is a positive integer;

[0053] The transformer comprises N transformer first windings connected to the N inverter circuits in one-to-one correspondence and M transformer second windings connected to the M rectifier circuits in one-to-one correspondence, the first sides of the N inverter circuits are connected to each other as the first side of the DC converter, the second sides are connected in parallel with the corresponding transformer first windings, the first sides of the rectifier circuits are connected in parallel with the corresponding transformer second windings, and the second sides of the M rectifier circuits are connected to each other as the second side of the DC converter; all transformer first windings and all transformer second windings are coupled to the same magnetic circuit; wherein the first sides of the N inverter circuits and / or the second sides of the M rectifier circuits are connected in series with each other;

[0054] A resonant impedance Z is connected in series in the circuit between the second side of the inverter circuit Inv and the first winding of the transformer and / or in the circuit between the first side of the rectifier circuit Rec and the second winding of the transformer, and the inductive reactance of the resonant impedance Z is greater than the inductive reactance of the leakage inductance of the first winding of the transformer, and greater than the inductive reactance of the leakage inductance of the second winding of the transformer.

[0055] It should be noted that the DC converter will be used in fields such as server power supply or electric vehicle charging, and the output end is connected to the battery or chip of the device to supply power to various types of loads. At this time, the DC converter usually needs to have the ability to adjust and stabilize the voltage, that is, the DC converter needs to have a certain voltage gain range. Taking this requirement of the DC converter into consideration, when designing the cellular circuit, the present application adds an additional resonant impedance Z that can provide inductive impedance in its resonant cavity, forming a new topology, and increases the inductance value of the resonant cavity by increasing the resonant impedance Z, and then combines specific control methods such as frequency conversion, phase shifting or duty cycle variation to achieve the expansion of the gain of the cellular circuit, and then achieve voltage regulation and voltage stabilization, so that the cellular circuit topology has the ability to stabilize the voltage, thereby effectively expanding the application scenarios of the cellular circuit.

[0056] It can be understood that the entire DC converter is still mainly implemented in the form of a cellular circuit. In general, the first sides of the N inverter circuits are connected in series to form the first side of the DC converter, that is, the first end of the first side of the first inverter circuit serves as the first end of the first side of the DC converter, the second end of the first side of the i-th inverter circuit is connected to the first end of the first side of the i+1-th inverter circuit, and the second end of the first side of the N-th inverter circuit serves as the second end of the first side of the DC converter; the second sides of the M rectifier circuits are connected in series to form the second side of the DC converter, and the first end of the second side of the first rectifier circuit serves as the second end of the DC converter. The first end of the second side of the j-th rectifier circuit is connected to the first end of the second side of the j+1-th rectifier circuit, and the second end of the second side of the N-th rectifier circuit serves as the second end of the first side of the DC converter; the first side or the second side of the DC converter can be used as the input end of the DC converter, and the corresponding other side serves as the output end of the DC converter, the first winding of the transformer or the second winding of the transformer corresponding to the input end serves as the primary winding of the transformer, and the first winding of the transformer or the second winding of the transformer corresponding to the output end serves as the secondary winding of the transformer. The present application is mainly described with the first side of the DC converter as the input end of the DC converter. The present application is mainly applied to the circuit topology in which multiple low-voltage cell circuits are connected in series to replace high-voltage devices. The input side of the DC converter is connected to the input power supply Vin, and the output end is used to output the converted voltage Vout, which can be connected to various loads. The first sides of the N inverter circuits Inv are connected in series to share the input power supply, and the second sides of the M rectifier circuits Rec are connected in series to share the output voltage. At least one side of the first side of the N inverter circuits and the second side of the M rectifier circuits is connected in series, thereby maintaining the topology of replacing high-voltage devices with low-voltage cell circuits composed of low-voltage devices, so that the entire DC converter can still use low-voltage devices to reduce losses and increase switching frequency, which helps the converter to achieve efficient and high-power density energy conversion, and ensures the efficient and high-power density power conversion of the DC converter. At the same time, the first winding of each transformer and the second winding of the transformer are coupled to the same magnetic circuit, and the voltage balancing between each cell can still be achieved through the magnetic coupling of the transformer, without the need for additional voltage balancing or current balancing control.

[0057] It should be noted that there are multiple options for implementing the same magnetic circuit, and this application does not make any special restrictions here. It is possible that only one magnetic core is set in the transformer, and all the first windings of the transformer and the second windings of the transformer are coupled to the magnetic circuit formed by the same magnetic core, thereby realizing a magnetic circuit. It is also possible that multiple mutually coupled magnetic cores are set in the transformer to realize a magnetic circuit. It is not difficult to understand that the first side of the DC converter will be connected to the DC input power supply, and the inverter circuit Inv is used to convert this DC power into AC power. After passing through the corresponding first winding of the transformer and the second winding of the transformer in the transformer, the rectifier circuit Rec converts this AC power into DC power, thereby realizing the entire DC / DC conversion; the specific types and implementation methods of the inverter circuit Inv and the rectifier circuit Rec are not particularly limited in this application. The circuit topology of each inverter circuit Inv and the rectifier circuit Rec is preferably consistent. In order to facilitate voltage balancing, the first side of the inverter circuit Inv can be provided with a first bus capacitor connected in parallel between the two ends of its first side, and the second side of the rectifier circuit Rec can also be provided with a second bus capacitor connected in parallel between the two ends of its second side. The output side of the DC converter can also be provided with a load resistor connected in parallel between the two output ends.

[0058] It should be noted that the voltage gain range of the DC converter is usually related to the inductance value in the resonant cavity. Therefore, in order to achieve voltage regulation and voltage stabilization of the DC converter, the resonant impedance Z needs to provide a sufficiently large inductance value to increase the voltage gain range of the DC converter. Therefore, the resonant impedance Z needs to include inductive reactance. At the same time, in order to avoid the influence of the leakage inductance of the transformer, that is, the leakage inductance of the first winding of the transformer or the leakage inductance of the second winding of the transformer on the voltage regulation and voltage stabilization control, when setting the resonant impedance Z, it is necessary to set the inductive reactance of the resonant impedance Z to be greater than the inductive reactance of the leakage inductance of the first winding of the transformer, and greater than the inductive reactance of the leakage inductance of the second winding of the transformer, that is, the inductive reactance of the resonant impedance Z is greater than the leakage inductance of the transformer, and it is generally set to dozens of times or more of the leakage inductance of the transformer, for example, it can be 100 times. The resonant impedance Z can be set only on the circuit between the second side of the inverter circuit Inv and the first winding of the transformer or on the circuit between the first side of the rectifier circuit Rec and the second winding of the transformer, or can be set on the circuit between the second side of the inverter circuit Inv and the first winding of the transformer and on the circuit between the first side of the rectifier circuit Rec and the second winding of the transformer at the same time. The resonant impedance can be set in all inverter circuits or rectifier circuits, and the present application does not make any special restrictions here. A preferred embodiment is that each inverter circuit or rectifier circuit adopts the same method to realize the resonant impedance, ensure the consistency of each cell, and improve the accuracy and reliability of the output voltage of the entire DC converter.

[0059] As a specific embodiment, please refer to Figure 2 , Figure 2A schematic diagram of the structure of another DC converter provided by the present invention; the structure of the DC converter composed of the cellular circuit is as follows Figure 2 As shown, the primary side includes N inverter cells connected in series, which share the input DC side voltage together. The secondary side is M rectifier cells connected in series, which share the output voltage together. The inverter cells use low-voltage tubes to reduce conduction losses, so N is a positive integer not less than 2. The rectifier side can use switching tubes for synchronous rectification to reduce conduction losses, or simply use high-voltage diodes to simplify the circuit, so M is a positive integer.

[0060] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of the first inverter circuit provided by the present invention; please refer to Figure 4 , Figure 4 This is a schematic diagram of the structure of the second inverter circuit provided by the present invention; please refer to Figure 5 , Figure 5 This is a schematic diagram of the structure of the first rectifier circuit provided by the present invention; please refer to Figure 6 , Figure 6 This is a schematic diagram of the structure of the second rectifier circuit provided by the present invention; please refer to Figure 7 , Figure 7 A schematic diagram of the structure of the third rectifier circuit provided by the present invention; wherein the resonant impedance Z includes a primary resonant impedance Z connected in series between the second side of the inverter circuit Inv and the first winding of the transformer p and the secondary resonant impedance Z in series with the circuit between the first side of the rectifier circuit Rec and the second winding of the transformer s The inverter cell includes the first bus capacitor, the inverter circuit Inv composed of the switch tube, and the additional primary resonant impedance Z p And the first winding of the transformer; the inverter circuit Inv can be implemented by a full-bridge or half-bridge inverter structure, or by a multi-level inverter structure, such as Figure 3 and Figure 4 As shown, Figure 3 It is a realization method of an inverter circuit Inv using a full-bridge structure. Figure 4 is a realization method of the inverter circuit Inv using a half-bridge structure; the primary side resonant impedance Z p It can be realized by using a single inductor impedance, or by constructing a series resonance or a multi-element resonant circuit. The rectifier cell includes the transformer's second winding, an additional secondary resonant impedance Z s , a rectifier circuit Rec composed of a switch tube and a second bus capacitor; the rectifier circuit Rec can be implemented by a full-bridge rectifier or a voltage-doubler rectifier structure, or by a center-tap rectifier, such as Figure 5 , Figure 6 and Figure 7 As shown, Figure 5A method for implementing a rectifier circuit Rec using a voltage doubler rectifier structure is shown in FIG. Figure 6 A method for implementing a rectifier circuit Rec using full-bridge rectification is shown in FIG. Figure 7 is a realization method of the rectifier circuit Rec using center-tap rectification; the secondary resonant impedance Z s Similar to the setting method of the primary side resonant impedance, it can be implemented by using a single inductor impedance, or by constructing a series resonance or a multi-element resonant circuit.

[0061] The present invention provides a DC converter, including a transformer, N inverter circuits and M rectifier circuits, wherein the first winding of the transformer corresponding to each inverter circuit and the second winding of the transformer corresponding to each rectifier circuit are coupled to the same magnetic circuit, which can effectively realize the voltage balancing between the N inverter circuits, so that when a low-voltage cellular circuit composed of low-voltage devices is used to replace a high-voltage device, the advantage of the cellular circuit that can use low-voltage devices to reduce losses and increase switching frequency is maintained, which helps to achieve high-efficiency and high-power density energy conversion. At the same time, a resonant impedance Z is added to the circuit between the second side of the inverter circuit Inv and the first winding of the transformer and / or the first side of the rectifier circuit Rec and the second winding of the transformer in series, and an additional inductive impedance is added to the resonant cavity of the DC converter, thereby realizing the expansion of the voltage gain range of the DC converter, so that the DC converter can realize the functions of voltage regulation and voltage stabilization, can flexibly regulate its own output voltage, and expand the application scenario of the DC converter.

[0062] Based on the above embodiments:

[0063] Please refer to Figure 8 , Figure 8 A schematic diagram of the construction method of the first resonant impedance provided by the present invention; as an optional embodiment, the resonant impedance Z is a first inductor, the first end of the first inductor is connected to the first end of the second side of the inverter circuit Inv, and the second end is connected to the first end of the first winding of the transformer.

[0064] It is understandable that there are multiple implementation methods for the construction of the resonant impedance Z. Specifically, a single inductor impedance can be used for implementation. Taking the primary resonant impedance as an example, a first inductor can be directly set in series between the first end of the second side of the inverter circuit Inv and the first end of the corresponding transformer first winding to realize the primary resonant impedance, and only this primary resonant impedance is set as the resonant impedance in the entire DC converter. The secondary resonant impedance can also be set similarly, and a first inductor is set in series between the first end of the second winding of the transformer and the first end of the first side of the rectifier circuit Rec to realize the secondary resonant impedance. The specific type and implementation method of the first inductor are not particularly limited in this application.

[0065] Specifically, a series inductor can be used to realize the resonant impedance. The component itself has low cost, small size, simple structure and is easy to realize, which is conducive to the simple realization of the inverter cell and the entire DC converter.

[0066] Please refer to Fig. 9 , Fig. 9 A schematic diagram of the coupling mode of the resonant impedances in the first N inverter circuits provided by the present invention; as an optional embodiment, the N first inductors of the N inverter circuits are N inductor coils in the same coupled inductor.

[0067] It should be noted that if N inverter circuits all use inductors to construct resonant impedance, or if there are multiple inverter circuits that use inductors to construct resonant impedance, multiple inductors can be implemented in the form of coupled inductors. The coupled inductor includes multiple inductor coils, each of which serves as the first inductor of each inverter circuit and is connected in series in the circuit between the second side of the inverter circuit Inv and the first winding of the transformer, that is, the first inductors of multiple inverter circuits can be implemented by a coupled inductor composed of multiple inductors coupled to each other. If there are multiple rectifier circuits among the M rectifier circuits that use inductors to construct resonant impedance, multiple inductors can also be implemented in a similar manner by using coupled inductors, which will not be described in detail in this application. The specific type and implementation method of the coupled inductor are not particularly limited in this application, and the specific number of inductors can also be selected and set according to the actual application of the DC converter. The coupled inductor is not only applicable to the case where the resonant impedance Z is realized by a single first inductor. As long as an inductor device is used to construct the resonant impedance Z in the resonant cavity, multiple inductors can be realized by multi-cell intracellular mutual coupling.

[0068] Specifically, when the resonant impedance Z is implemented using an inductor device, the multiple inductor devices corresponding to the multiple inverter circuits or the multiple rectifier circuits can be implemented using multiple inductor coils coupled to each other in the same coupled inductor, further reducing the number of devices required to construct the resonant cavity, simplifying the construction method of the resonant cavity, and achieving a simpler construction of the resonant impedance Z. The process consistency of the resonant cavities corresponding to the various inverter circuits or rectifier circuits is higher, which is conducive to improving the accuracy of voltage regulation and voltage stabilization control, and the circuit integration is higher, which is conducive to the simple implementation of the entire DC converter.

[0069] Please refer to Fig.10 , Fig.10 This is a schematic diagram of the construction method of the second resonant impedance provided by the present invention; please refer to Fig.11 , Fig.11 A schematic diagram of the coupling mode of the resonant impedances in the second N inverter circuits provided by the present invention; as an optional embodiment, the resonant impedance Z includes:

[0070] The second inductor and the first capacitor are connected in series, and the first end of the circuit formed by the second inductor and the first capacitor being connected in series is connected to the first end of the second side of the inverter circuit, and the second end is connected to the first end of the first winding of the transformer.

[0071] As a specific embodiment, the first end of the second inductor is connected to the first end of the second side of the inverter circuit Inv; the first end of the first capacitor is connected to the second end of the second inductor, and the second end is connected to the first end of the first winding of the transformer.

[0072] It is understandable that there are many ways to implement the construction of the resonant impedance Z. Specifically, it can be implemented by using an LC series structure composed of a second inductor and a first capacitor connected in series. Taking the primary resonant impedance as an example, a group of second inductors and first capacitors connected in series can be directly set in series between the first end of the second side of the inverter circuit Inv and the first end of the corresponding first winding of the transformer to realize the primary resonant impedance. The secondary resonant impedance can also be set in a similar way. A group of second inductors and first capacitors connected in series can be set in series between the first end of the second winding of the transformer and the first end of the first side of the rectifier circuit Rec to realize the secondary resonant impedance. The specific type and implementation method of the second inductor and the first capacitor are not particularly limited in this application. When multiple inverter circuits or rectifier circuits use the second inductor and the first capacitor to realize the resonant impedance, such as Fig.11 As shown, the multiple second inductors can also be implemented in the form of multiple inductor coils in the same coupled inductor.

[0073] Specifically, an LC series structure can be used to achieve resonant impedance. The components themselves are low-cost, small in size, and simple in construction, easy to implement, and are conducive to the simple implementation of the entire DC converter. Adding capacitor devices to the resonant impedance Z to facilitate the adjustment of the circuit's resonance point can also further reduce energy losses in the circuit, avoid high-frequency ripples generated when the switch tube is turned on and off, and improve power quality.

[0074] Please refer to Fig.12 , Fig.12 This is a schematic diagram of the construction method of the third resonant impedance provided by the present invention; please refer to Fig.13 , Fig.13 A schematic diagram of a coupling mode of resonant impedances in a third N inverter circuit provided by the present invention; as an optional embodiment, the resonant impedance Z includes:

[0075] a third inductor, a first end of which is connected to a first end of a second side of the inverter circuit Inv;

[0076] A second capacitor, a first end of which is connected to a second end of the second inductor;

[0077] The fourth inductor has a first end connected to the second end of the second capacitor and the first end of the first winding of the transformer, and a second end connected to the second end of the second side of the inverter circuit Inv and the second end of the first winding of the transformer.

[0078] It is not difficult to understand that there are many ways to implement the construction of the resonant impedance Z. Specifically, it can be implemented by using an LLC structure composed of a third inductor, a fourth inductor and a second capacitor. Taking the primary resonant impedance as an example, a group of third inductors and second capacitors connected in series can be directly set in series between the first end of the second side of the inverter circuit Inv and the first end of the corresponding first winding of the transformer, and the fourth inductor is connected in parallel at both ends of the first winding of the transformer to realize the primary resonant impedance. The third inductor and the second capacitor only need to be connected in series, and are not limited to the structure in which the third inductor is connected to the inverter circuit Inv. The secondary resonant impedance can also be set similarly, and a group of third inductors and second capacitors are set in series between the first end of the second winding of the transformer and the first end of the first side of the rectifier circuit Rec, and the fourth inductor is connected in parallel at both ends of the second winding of the transformer to realize the secondary resonant impedance. The specific types and implementation methods of the third inductor, the second capacitor and the fourth inductor are not particularly limited in this application. When multiple inverter circuits or rectifier circuits adopt the LLC structure to realize the resonant impedance, such as Fig.13 As shown, the plurality of third inductors and / or the plurality of fourth inductors may also be implemented in the form of a plurality of inductor coils in the same coupled inductor.

[0079] As a specific embodiment, please refer to Fig.14 , Fig.14 A schematic diagram of the structure of a DC converter composed of a cellular LLC circuit provided by the present invention; please refer to Fig.15 , Fig.15 A schematic diagram of a signal waveform of a DC converter composed of a cellular LLC circuit provided by the present invention; According to the construction method of the resonant cavity topology provided in this embodiment, a cellular LLC circuit with a coupled resonant inductor can be constructed, and its topology is as follows Fig.14 As shown. The N inverter circuits all use LLC topology to construct the resonant cavity, and the third inductor is implemented by N inductor coils L11, L12 to L1N of the same coupled inductor. The inverter circuit Inv is implemented by series-connected switch tubes Q11 and Q12, and the rectifier circuit Rec is implemented by series-connected switch tubes Q21 and Q22. At the same time, in conjunction with the structure of the rectifier circuit Rec, the second bus capacitor is formed by series-connected capacitors C13 and C14.

[0080] by Fig.14 Take the cellular DCDC circuit with coupled resonant inductor as an example. Fig.15Schematic diagram of waveforms of various signals in the DC converter, VgsH is the driving signal of the switch tube Q11, VgsL is the driving signal of the switch tube Q12, VdsH is the driving signal of the switch tube Q21, VdsL is the driving signal of the switch tube Q22, i pn is the current flowing through the inductor L1N in the inverter circuit, i Lm_p is the current flowing through the inductor Lm in the inverter circuit, i sm is the current flowing through the second winding of the transformer. It can be seen that there is good consistency between multiple cells, which can effectively achieve voltage balancing between cells, and the switch tubes have consistent soft switching characteristics.

[0081] Specifically, an LLC structure can be used to achieve resonant impedance. The components themselves are low-cost, small in size, and simple in construction, easy to implement, and are conducive to the simple implementation of the entire DC converter. The LLC structure can further ensure the soft switching characteristics of the switching tube, improve the overall efficiency of the circuit, and ensure good output characteristics of the converter, which is conducive to the realization of a DC converter with high power density.

[0082] Please refer to Fig.16 , Fig.16 This is a schematic diagram of a fourth resonant impedance configuration provided by the present invention; as an optional embodiment, the resonant impedance Z includes:

[0083] a fifth inductor, a first end of which is connected to a first end of a second side of the inverter circuit Inv;

[0084] a third capacitor, a first end of which is connected to the second end of the fifth inductor;

[0085] Sixth inductor;

[0086] The fourth capacitor has a first end connected to the second end of the third capacitor and the first end of the sixth inductor respectively, and a second end connected to the second end of the sixth inductor and the second end of the first winding of the transformer respectively.

[0087] It is understandable that there are multiple implementation methods for the construction of the resonant impedance Z. Specifically, it can be implemented by using an LLCC structure composed of a fifth inductor, a third capacitor, a sixth inductor and a fourth capacitor. The fifth inductor and the third capacitor are connected in series to form a subcircuit, and the sixth inductor and the fourth capacitor are connected in parallel to form another subcircuit. Both subcircuits are connected in series to corresponding positions to form the resonant impedance Z. Taking the primary side resonant impedance as an example, a group of fifth inductors and third capacitors connected in series can be directly set in series between the first end of the second side of the inverter circuit Inv and the first end of the corresponding first winding of the transformer, and a group of sixth inductors and fourth capacitors connected in parallel can be connected in series to realize the primary side resonant impedance. Among them, the fifth inductor and the third capacitor only need to be connected in series, and are not limited to the structure in which the fifth inductor is connected to the inverter circuit Inv. The secondary side resonant impedance can also be set in a similar manner, and a group of fifth inductors and third capacitors connected in series are set in series between the first end of the second winding of the transformer and the first end of the first side of the rectifier circuit Rec, and a group of sixth inductors and fourth capacitors connected in parallel are connected in series to realize the secondary side resonant impedance. The present application does not specifically limit the specific types and implementation methods of the fifth inductor, the third capacitor, the sixth inductor, and the fourth capacitor. When multiple inverter circuits or rectifier circuits use LLCC structures to implement resonant impedance, multiple fifth inductors and / or multiple sixth inductors can also be implemented using multiple inductor coils in the same coupled inductor.

[0088] Specifically, the LLCC structure can be used to achieve resonant impedance. The components themselves are low-cost, small in size, and simple in construction, easy to implement, which is conducive to the simple implementation of the entire DC converter; the LLCC structure can further expand the voltage regulation range of the DC converter, so that it can meet more diverse voltage regulation and voltage stabilization requirements.

[0089] Please refer to Fig.17 , Fig.17 A schematic diagram of the structure of a DC converter using an ISOP type circuit provided by the present invention; please refer to Fig.18 , Fig.18 A schematic structural diagram of a DC converter using an IPOS type circuit provided by the present invention; as an optional embodiment, the first end of the first side of the first inverter circuit serves as the first end of the first side of the DC converter, the second end of the first side of the i-th inverter circuit is connected to the first end of the first side of the i+1-th inverter circuit, and the second end of the first side of the N-th inverter circuit serves as the second end of the first side of the DC converter; the first ends of the second sides of the M rectifier circuits are connected to each other and serve as the first end of the second side of the DC converter, and the second ends of the second sides of the M rectifier circuits are connected to each other and serve as the second end of the second side of the DC converter; i is a positive integer, and i<N.

[0090] It is understandable that when N inverter circuits and M rectifier circuits are used to implement a DC converter, the inverter circuits or rectifier circuits can not only be connected in series, but also the power of the DC converter can be expanded by connecting the modules in series and in parallel. Specifically, it can be an ISOP (input series output parallel) type circuit in which the input side of the DC converter is connected in series and the output side is connected in parallel, or an IPOS (input parallel output series) type circuit in which the input side of the DC converter is connected in parallel and the output side is connected in series.

[0091] As a specific embodiment, taking the first side of the DC converter as the input side as an example, Fig.17 The figure shows the topological structure of the DC converter when it is implemented using an ISOP circuit. Fig.18 The topological structure shown is when the DC converter is implemented using an IPOS type circuit. Alternatively, the IPOS type DC converter can be implemented by controlling the ISOP type circuit to run in reverse.

[0092] Furthermore, there are also multiple coupling modes for the transformer in the DC converter to achieve voltage balancing between each cell. The first winding of the transformer corresponding to the inverter circuit Inv and the second winding of the transformer corresponding to the rectifier circuit Rec can be directly coupled through the same magnetic core. Alternatively, multiple transformers can be set in the converter, and voltage balancing can be achieved between different transformers by leading out additional auxiliary windings on the magnetic core. Please refer to Fig.19 , Fig.19 A schematic diagram of the structure of a DC converter using an auxiliary winding to achieve cellular circuit coupling provided by the present invention; Fig.19 The figure shows a schematic diagram of auxiliary winding setting by setting an independent transformer for the Nth cell circuit. The auxiliary winding can be set on the primary side or the secondary side of the transformer, or multiple auxiliary windings can be set. The coupling of the auxiliary windings ensures that the magnetic flux on multiple magnetic cores is consistent, thereby achieving voltage balancing.

[0093] Specifically, there are also multiple options for connecting multiple inverter circuits and rectifier circuits in a DC converter. The ISOP structure or the IPOS structure can be used to achieve the connection between multiple inverter circuits and rectifier circuits. The ISOP structure can withstand higher input voltages, and the IPOS structure can meet the needs of greater power input, thereby effectively expanding the scope of application of the DC converter and improving the flexibility of the DC converter.

[0094] In order to solve the above technical problems, the present invention further provides a control method of a DC converter, which is applied to the DC converter as described above. The control method of the DC converter comprises:

[0095] Determining a current output voltage and a required voltage of the DC converter;

[0096] The control parameters of the switch tube in the DC converter are adjusted to control the output voltage of the DC converter to reach the required voltage.

[0097] It is not difficult to understand that the voltage regulation and voltage stabilization control of the DC converter needs to be implemented in conjunction with the corresponding control method. At the same time, the applicable control methods are also different for the construction methods of different resonant impedances.

[0098] As an optional embodiment, adjusting the control parameters of the switch tube in the DC converter includes:

[0099] Adjust the switching frequency and / or duty cycle of the switch tube in the DC converter.

[0100] The voltage regulation and voltage stabilization of the DC converter can be specifically implemented in a frequency modulation manner. The output voltage can be adjusted by adjusting the switching frequency of the switch tube in the DC converter. In particular, when the resonant impedance is implemented in an inductor plus capacitor manner, the switching frequency of the switch tube has the best control effect on the output voltage of the DC converter. The control module can control the DC converter to work near the resonance point by adjusting the switching frequency of the switch tube in the DC converter, that is, the switching frequency of the switch tube is basically consistent with the resonant frequency of the resonant cavity. At this time, the gain is maximum and the output voltage is high. When the switching frequency is greater than the resonant frequency, that is, when working in an over-resonant state, as the switching frequency increases, the gain of the converter decreases and the output voltage decreases. When the switching frequency is less than the resonant frequency, that is, when working in an under-resonant state, as the switching frequency decreases, the gain also decreases, and the output voltage also decreases. By changing the switching frequency, the gain of the converter can be adjusted, thereby achieving the regulation of the output voltage. The specific type of the control module and the control method of the switch tube are not particularly limited in this application. The switching frequencies of the switches in the inverter circuit and the rectifier circuit can be adjusted at the same time, or only the switching frequencies of the switches in the inverter circuit or the rectifier circuit can be adjusted.

[0101] Specifically, when the resonant impedance is realized by both inductance and capacitance, the resonant state of the DC converter has a greater impact on the output voltage. Therefore, adjusting the resonant state of the DC converter by adjusting the switching frequency of the switching tube and thus adjusting the output voltage control method of the DC converter can achieve the best voltage regulation and voltage stabilization control.

[0102] Please refer to Fig. 20 , Fig. 20 A schematic diagram of the structure of a cellular DAB circuit provided by the present invention;

[0103] It is understandable that when the resonant impedance is realized by only a single inductor device and no capacitor device is added, the resonant capacitance in the resonant cavity is considered to be infinite and the resonance point of the circuit is infinitely small. Therefore, the DC converter generally operates at a state far higher than the resonance point. At this time, the switching frequency has a poor control effect on the output voltage of the DC converter. The output voltage can be adjusted and stabilized by a variable duty cycle. The application does not make any special restrictions on the specific type of control module and the control method of the switch tube. The duty cycle of the switch tube in the inverter circuit and the rectifier circuit can be adjusted at the same time, or only the duty cycle of the switch tube in the inverter circuit or the rectifier circuit can be adjusted. Fig. 20 As shown, when the resonant impedance is realized by using a single first inductor, a cellular DAB (dual active bridge) circuit is formed.

[0104] Specifically, when the DC converter operates away from the resonance point, the duty cycle can be changed to adjust the conduction time of the switch tube to adjust the energy storage time of the transformer, thereby adjusting the output voltage.

[0105] Please refer to Fig.21 , Fig.21 A waveform diagram of a control signal and an output signal of a phase shift control method provided by the present invention; as an optional embodiment, adjusting the control parameters of the switch tube in the DC converter includes:

[0106] Adjust the conduction timing of several switch tubes in the inverter circuit of the DC converter and / or the conduction timing of several switch tubes in the rectifier circuit.

[0107] It is not difficult to understand that when the resonant impedance is realized by only a single inductor device without adding a capacitor, a cellular DAB circuit will be formed to realize the DC converter. At this time, the control module can also use a phase shift control method to adjust the output voltage of the DC converter. The phase shift control method is to control the opening time between different bridge arms to shift the phase by a certain angle to control the output voltage. The specific type of the control module and the control method of the switch tube are not particularly limited in this application. The conduction timing of the switch tube in the inverter circuit and the rectifier circuit can be adjusted at the same time, or only the conduction timing of the switch tube in the inverter circuit or the rectifier circuit can be adjusted.

[0108] As a specific embodiment, a phase shift control method is implemented as follows: Fig.21As shown, s11 is the driving signal of the switch tube Q31 on the first bridge arm of the inverter circuit, s12 is the driving signal of the switch tube Q32 on the first bridge arm of the inverter circuit, s13 is the driving signal of the switch tube Q33 on the second bridge arm of the inverter circuit, s14 is the driving signal of the switch tube Q34 on the second bridge arm of the inverter circuit, s21 is the driving signal of the switch tube Q41 on the first bridge arm of the rectifier circuit, s22 is the driving signal of the switch tube Q42 on the first bridge arm of the rectifier circuit, s23 is the driving signal of the switch tube Q43 on the second bridge arm of the rectifier circuit, and s24 is the driving signal of the switch tube Q44 on the second bridge arm of the rectifier circuit. Fig.21 The shadow shown is the time period when the corresponding marked driving signal is at a high level, that is, the time period when the corresponding switch tube is turned on. When the two switch tubes on the second bridge arm of the inverter circuit are turned on, there is a certain phase offset between their turn-on time and the turn-on time of the two switch tubes on the first bridge arm of the inverter circuit. When the two switch tubes on the second bridge arm of the rectifier circuit are turned on, there is a certain phase offset between their turn-on time and the turn-on time of the two switch tubes on the first bridge arm of the rectifier circuit. At the same time, the output voltage v Mp and the output current i p It will also change with the phase shift, thereby achieving the regulation of the output voltage of the DC converter. The signals between the N inverter circuits have good consistency, which can effectively achieve voltage balancing between cells.

[0109] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0110] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A DC converter, characterized in that: It includes a transformer, N inverter circuits and M rectifier circuits, where N is a positive integer greater than 1 and M is a positive integer; The transformer comprises N transformer first windings connected to N inverter circuits in one-to-one correspondence and M transformer second windings connected to M rectifier circuits in one-to-one correspondence, the first sides of the N inverter circuits are connected to each other as the first side of the DC converter, the second sides are connected in parallel with the corresponding transformer first windings, the first sides of the rectifier circuits are connected in parallel with the corresponding transformer second windings, and the second sides of the M rectifier circuits are connected to each other as the second side of the DC converter; all the transformer first windings and all the transformer second windings are coupled to the same magnetic circuit; wherein the first sides of the N inverter circuits and / or the second sides of the M rectifier circuits are connected in series with each other; A resonant impedance is connected in series in the circuit between the second side of the inverter circuit and the first winding of the transformer and / or in the circuit between the first side of the rectifier circuit and the second winding of the transformer, and the inductive reactance of the resonant impedance is greater than the inductive reactance of the leakage inductance of the first winding of the transformer, and greater than the inductive reactance of the leakage inductance of the second winding of the transformer.

2. The DC converter according to claim 1, characterized in that: The resonant impedance is a first inductor, a first end of the first inductor is connected to a first end of the second side of the inverter circuit, and a second end of the first inductor is connected to a first end of the first winding of the transformer.

3. The DC converter according to claim 2, characterized in that: The N first inductors of the N inverter circuits are N inductor coils in the same coupled inductor.

4. The DC converter according to claim 1, characterized in that: The resonant impedance includes: A second inductor and a first capacitor are connected in series, wherein a first end of a circuit formed by connecting the second inductor and the first capacitor in series is connected to a first end of a second side of the inverter circuit, and a second end is connected to a first end of a first winding of the transformer.

5. The DC converter according to claim 1, characterized in that: The resonant impedance includes: a third inductor, a first end of which is connected to a first end of the second side of the inverter circuit; A second capacitor, a first end of which is connected to a second end of the second inductor; A fourth inductor has a first end connected to the second end of the second capacitor and the first end of the first winding of the transformer, and a second end connected to the second end of the second side of the inverter circuit and the second end of the first winding of the transformer.

6. The DC converter according to claim 1, characterized in that: The resonant impedance includes: a fifth inductor, a first end of which is connected to a first end of the second side of the inverter circuit; a third capacitor, a first end of which is connected to the second end of the fifth inductor; Sixth inductor; A fourth capacitor has a first end connected to the second end of the third capacitor and the first end of the sixth inductor respectively, and a second end connected to the second end of the sixth inductor and the second end of the first winding of the transformer respectively.

7. The DC converter according to claim 1, characterized in that: The first end of the first side of the first inverter circuit serves as the first end of the first side of the DC converter, the second end of the first side of the i-th inverter circuit is connected to the first end of the first side of the i+1-th inverter circuit, and the second end of the first side of the N-th inverter circuit serves as the second end of the first side of the DC converter; the first ends of the second sides of the M rectifier circuits are connected to each other and serve as the first end of the second side of the DC converter, and the second ends of the second sides of the M rectifier circuits are connected to each other and serve as the second end of the second side of the DC converter; i is a positive integer, and i<N.

8. A control method for a DC converter, characterized in that: Applied to the DC converter according to any one of claims 1 to 7, the control method of the DC converter comprises: Determining a current output voltage and a required voltage of the DC converter; The control parameters of the switch tube in the DC converter are adjusted to control the output voltage of the DC converter to reach the required voltage.

9. The control method of the DC converter according to claim 8, characterized in that: Adjusting the control parameters of the switch tube in the DC converter includes: Adjust the switching frequency and / or duty cycle of the switch tube in the DC converter.

10. The control method of the DC converter according to claim 8, characterized in that: Adjusting the control parameters of the switch tube in the DC converter includes: Adjust the conduction timing of several switch tubes in the inverter circuit of the DC converter and / or the conduction timing of several switch tubes in the rectifier circuit.

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