DCDC topology and control method

Abstract

The invention provides a DCDC topology, a core component of an input end power circuit of the DCDC topology only comprises four switching tubes and a capacitor, and a transformer only comprises a primary winding. The embodiment of the invention further provides a control method which is matched with the DCDC topology to work. Through the configuration, on one hand, different control time sequences can be supported so as to meet the requirement of being compatible with wide-range input voltage, on the other hand, the structure is simple, the complexity of the system is reduced, the cost is reduced, the circuit efficiency is improved, and the probability of system faults is also reduced; the problem that a DCDC topology capable of meeting multiple design requirements is lacked in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of DCDC power supply, and in particular to a DCDC topology and a control method. Background Art

[0002] With the rapid development of the new energy vehicle industry, low-cost, high-reliability on-board power products have gradually gained popularity. In order to increase the charging power level, high-voltage batteries have gradually developed from 400V systems to 800V systems. Under normal circumstances, two sets of circuit parameters are designed for the 400V system (200-500V) and the 800V (500V-900V) system respectively, which can ensure that the on-board DCDC power supply (such as PFSB topology) works normally within the corresponding input voltage range. For the 800V system, when its battery voltage is <500V, how to ensure that the on-board DCDC power supply can work normally is also a problem that technicians in this field need to consider.

[0003] In the existing technology, in order to take into account the application conditions of 400V and 800V systems at the same time and improve the application range and reliability of vehicle-mounted DCDC power supplies, the solution ideas can be summarized as follows: 1) using a two-stage topology; 2) changing the transformer turns ratio.

[0004] Solutions using a two-level topology, such as Figure 1a or Figure 1b shown. Figure 1a The working principle of the DCDC topology shown is as follows: when the battery voltage is >500V, the first-stage Buck circuit reduces the input battery voltage to a voltage <500V, and then the second-stage traditional on-board DCDC topology (PSFB, phase-shift control mode) obtains the required voltage; when the battery voltage is <500V, the first-stage Buck switch SW is always on, and the battery voltage is directly transmitted to both ends of Cdc on the input side of PSFB.

[0005] You can also use Figure 1b In the structure shown, when the battery voltage is <500V, the first-stage Boost circuit increases the battery voltage to >500V, and then the second-stage traditional on-board DCDC adjusts the voltage; when the battery voltage is >500V, the first-stage Boost switch tube Su is always on, and the battery voltage is directly transmitted to both ends of Cdc on the input side of PSFB.

[0006] Change the transformer turns ratio scheme, such as Figure 1c or Figure 1d As shown in the patent CN101478243A, a wide input range switching power supply circuit is proposed. Figure 1cThis invention connects an additional set of transformer windings in parallel, and the two windings work in different input voltage ranges, that is, when the battery voltage is less than 500V, n301 and n303 are used to transform the voltage, and when the battery voltage is greater than 500V, n302 and n303 are used to transform the voltage, thereby ensuring that the circuit performance is good under a wide range of input conditions.

[0007] Another series transformer approach to solve the wide range of input voltage problems, such as Figure 1d When the input voltage is less than 500V, the switch tubes S405 and S406 are normally closed, and the input voltage Vin transfers energy to the output side through the transformer Tr401; when the input voltage is greater than 500V, the switch tubes S405 and S406 are normally turned off, and the n401 winding of the transformer Tr401 is connected in series with the n401 winding of the transformer Tr402, and together they transfer the energy of the input battery voltage to the output side.

[0008] Although the above methods can effectively achieve the working requirements of a wide range of input voltages, the following problems still exist: 1) The additional buck or boost circuit added to the two-stage topology not only increases the device cost, but also reduces the overall efficiency of the topology; 2) The use of a multi-transformer structure also increases the device cost and the complexity of the transformer design.

[0009] In other words, the existing technology lacks a DCDC topology that can simultaneously meet the requirements of compatibility with 400V platform batteries and 800V platform batteries and reduce structural complexity. Therefore, it is of great significance and necessity to study the wide-range input vehicle-mounted DCDC power supply, reduce the complexity of the DCDC topology and device cost on the basis of taking into account both 400V platform batteries and 800V platform batteries, and improve the compatibility and practicality of the vehicle-mounted DCDC power supply. Summary of the invention

[0010] The object of the present invention is to provide a DCDC topology and control method to simultaneously meet the requirements of compatibility with a wide range of input voltages and reduced structural complexity.

[0011] In order to solve the above technical problems, the present invention provides a DCDC topology, which includes an input power circuit and a transformer; the transformer includes a primary winding; the input power circuit includes a capacitor, an input positive electrode, an input negative electrode, a first switch tube, a second switch tube, a third switch tube and a fourth switch tube.

[0012] The input positive electrode, the first switch tube, the capacitor, the second switch tube and the input negative electrode are connected in sequence, the input positive electrode, the fourth switch tube, the third switch tube, the second switch tube and the input negative electrode are connected in sequence, the connection point between the first switch tube and the capacitor is connected to the first end of the primary winding, and the input negative electrode is connected to the second end of the primary winding.

[0013] Optionally, the DCDC topology switches between a first operating mode and a second operating mode based on a size of an input voltage; wherein the input voltage corresponding to the first operating mode is smaller than the input voltage corresponding to the second operating mode.

[0014] In the first working mode, the capacitor is used to work as an active clamping capacitor.

[0015] In the second working mode, the capacitor is first charged to 50%±5% of the input voltage and then used as an energy storage and release element to reduce the ratio of the output voltage to the input voltage of the input end power circuit.

[0016] Optionally, the DCDC topology includes an output power circuit, the transformer includes a secondary winding, and the output power circuit includes a fifth switch tube, an output positive electrode, and an output negative electrode.

[0017] Among them, the output positive electrode, the fifth switch tube, the secondary winding and the output negative electrode are connected in sequence, or the output positive electrode, the secondary winding, the fifth switch tube and the output negative electrode are connected in sequence.

[0018] An end of the secondary winding closer to the output negative pole and the first end of the primary winding are the same-named ends.

[0019] In order to solve the above technical problems, the present invention further provides a control method, which acts on the above DCDC topology, and the control method includes:

[0020] Based on the magnitude of the input voltage, it is determined whether the current working mode is the first working mode or the second working mode; wherein the input voltage corresponding to the first working mode is smaller than the input voltage corresponding to the second working mode.

[0021] If it is determined to be the first working mode, the output control signal drives the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to work according to a first control timing sequence, so that the capacitor works as an active clamping capacitor.

[0022] If it is determined to be the second working mode, the capacitor is first charged to 50%±5% of the input voltage, and then a control signal is output to drive the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to operate according to the second control timing, so that the capacitor works as an energy storage and release element to reduce the ratio of the output voltage to the input voltage of the input power circuit.

[0023] Optionally, in the first control timing, the third switch tube is constantly off, the fourth switch tube is constantly off, one cycle is divided into four time periods, and the state of the first switch tube in one cycle is: on, off, off, off; the state of the second switch tube in one cycle is: off, off, on, off.

[0024] The control method further includes: in the first control sequence, the state of the fifth switch tube in one cycle is: disconnected, switched from disconnected to connected, connected, and switched from connected to disconnected.

[0025] Optionally, in the second control timing, the first switch tube is constantly off, the fourth switch tube is constantly on, one cycle is divided into four time periods, and the state of the second switch tube in one cycle is: off, off, on, off; the state of the third switch tube in one cycle is: on, off, off, off, off.

[0026] The control method further includes: in the first control sequence, the state of the fifth switch tube in one cycle is: disconnected, switched from disconnected to connected, connected, and switched from connected to disconnected.

[0027] Optionally, the control method includes: when the input voltage is less than 500V, judging that the current working mode is the first working mode; when the input voltage is greater than 500V, judging that the current working mode is the second working mode.

[0028] Compared with the prior art, in a DCDC topology provided by the present invention, the input power circuit of the DCDC topology includes a capacitor, an input positive electrode, an input negative electrode, a first switch tube, a second switch tube, a third switch tube and a fourth switch tube. The input positive electrode, the first switch tube, the capacitor, the second switch tube and the input negative electrode are connected in sequence, the input positive electrode, the fourth switch tube, the third switch tube, the second switch tube and the input negative electrode are connected in sequence, the connection point between the first switch tube and the capacitor is connected to one end of the primary winding of the transformer, and the input negative electrode is connected to the other end of the primary winding. . A control method provided by the present invention works in conjunction with the above-mentioned DCDC topology. Such a configuration, on the one hand, can support different control timings to meet the requirements of compatibility with a wide range of input voltages, and on the other hand, the structure is simple, which reduces the complexity of the system, reduces costs, improves circuit efficiency, and reduces the probability of system failure, solving the problem of the lack of such a DCDC topology that can meet multiple design requirements in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Those skilled in the art will appreciate that the accompanying drawings are provided for a better understanding of the present invention and do not constitute any limitation on the scope of the present invention.

[0030] Figure 1a It is one of the DCDC topologies in the prior art;

[0031] Figure 1b It is the second DCDC topology in the prior art;

[0032] Figure 1c It is one of the three DCDC topologies in the prior art;

[0033] Figure 1d It is one of the four DCDC topologies in the prior art;

[0034] Figure 2 is a schematic diagram of a DCDC topology according to an embodiment of the present invention;

[0035] Figure 3 is a control timing diagram of an embodiment of the present invention in a first working mode;

[0036] Figure 4 This is a control timing diagram of an embodiment of the present invention in the second working mode.

[0037] In the attached figure:

[0038] 1-input power circuit; 2-transformer; 3-output power circuit. DETAILED DESCRIPTION

[0039] In order to make the purpose, advantages and features of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis of each drawing is different, and sometimes different scales are used.

[0040] As used in the present invention, the singular forms "one", "an" and "the" include plural objects, the term "or" is generally used to include the meaning of "and / or", the term "several" is generally used to include the meaning of "at least one", and the term "at least two" is generally used to include the meaning of "two or more". In addition, the terms "first", "second" and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "the proximal end" and "the distal end" generally refer to two corresponding parts, which include not only the endpoints, and the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral body; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. In addition, as used in the present invention, an element disposed on another element generally only indicates that there is a connection, coupling, cooperation or transmission relationship between the two elements, and the connection, coupling, cooperation or transmission between the two elements may be direct or indirect through an intermediate element, and cannot be understood as indicating or implying the spatial position relationship between the two elements, that is, one element may be in any orientation such as inside, outside, above, below or on one side of another element, unless otherwise clearly indicated in the content. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0041] The core idea of ​​the present invention is to provide a DCDC topology and control method to simultaneously meet the requirements of compatibility with a wide range of input voltages and reduced structural complexity.

[0042] The following description is given with reference to the accompanying drawings.

[0043] Please refer to Figure 2The present invention provides a DCDC topology, which is a vehicle-mounted DCDC topology. However, the design concept of this embodiment can also be applied to DCDC topologies in other scenarios. The DCDC topology includes an input power circuit 1, a transformer 2, and an output power circuit 3. The input power circuit includes four switch tubes, namely, a first switch tube S1, a second switch tube S2, a third switch tube S3, and a fourth switch tube S4. The transformer includes a primary winding n1 and a secondary winding n2. The number of the primary winding n1 is only one, thereby reducing the complexity of the system.

[0044] The input power circuit also includes a capacitor Cb, an input positive electrode and an input negative electrode, the input positive electrode, the first switch tube S1, the capacitor Cb, the second switch tube S2 and the input negative electrode are connected in sequence, the input positive electrode, the fourth switch tube S4, the third switch tube S3, the second switch tube S2 and the input negative electrode are connected in sequence, the connection point between the first switch tube S1 and the capacitor is connected to the first end of the primary winding, and the input negative electrode is connected to the second end of the primary winding. The resonant inductor Lr and the excitation inductor Lm can be set according to actual needs and are not specifically limited here.

[0045] It can be understood that the above-mentioned DCDC topology structure provides the necessary hardware foundation for working in two working modes with different principles, and can solve the problems existing in the prior art.

[0046] The output power circuit can be configured according to actual needs. In a preferred embodiment, the output power circuit includes a fifth switch tube S5, an output positive electrode and an output negative electrode; wherein the output positive electrode, the fifth switch tube S5, the secondary winding and the output negative electrode are connected in sequence (such as Figure 2 Alternatively, the output positive electrode, the secondary winding, the fifth switch tube S5 and the output negative electrode are connected in sequence (not shown). In the above two schemes, the end of the secondary winding closer to the output negative electrode and the first end of the primary winding are the same end.

[0047] The DCDC topology switches between a first working mode and a second working mode based on the magnitude of an input voltage Vin.

[0048] For example, when the input voltage is less than the critical voltage, the first working mode is used, and when the input voltage is greater than the critical voltage, the second working mode is used. In this embodiment, the critical voltage is 500V, and in other embodiments, it can also be set according to actual needs. In addition, the working mode can also be switched according to more complex logic. For example, the first critical voltage corresponding to switching from the first working mode to the second working mode is different from the second critical voltage corresponding to switching from the second working mode to the first working mode. In this embodiment, the input voltage corresponding to the first working mode is less than the input voltage corresponding to the second working mode.

[0049] The concept of a switch tube should be understood in a broad sense. For example, if two switch elements are connected according to the following logic, an external signal controls the first switch element, and the first switch element controls the second switch element, the two switch elements should be regarded as one switch tube. For another example, if two switch elements are connected in series, when the four combined states of the two switch elements actually only play a role in disconnecting a branch in the circuit, they should also be regarded as one switch tube. Other more complicated situations are not described here.

[0050] The output power circuit further includes an output filter capacitor Co, and the output filter capacitor Co is arranged between the output positive electrode and the output negative electrode.

[0051] The switch tubes S1 to S5 may be NMOS tubes as shown in the figure, or may be other electrical components or a combination of electrical components having a switch function.

[0052] When Vin<500V, the DCDC topology operates in the first working mode. When Vin>500V, the DCDC topology operates in the second working mode.

[0053] This embodiment further provides a control method, which is applied to the above-mentioned DCDC topology. The control method includes:

[0054] Based on the magnitude of the input voltage, it is determined whether the current working mode is the first working mode or the second working mode; the specific determination logic has been introduced in the previous text.

[0055] If it is determined to be the first working mode, the output control signal drives the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to work according to a first control timing sequence, so that the capacitor works as an active clamping capacitor.

[0056] If it is determined to be the second working mode, the capacitor is first charged to 50%±5% of the input voltage, and then a control signal is output to drive the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to operate according to the second control timing, so that the capacitor works as an energy storage and release element to reduce the ratio of the output voltage to the input voltage of the input power circuit.

[0057] Please refer to Figure 3 In the first working mode, the third switch tube S3 is always off, the fourth switch tube S4 is always off, and one cycle is divided into four time periods. The state of the first switch tube S1 in one cycle is: on, off, off, off; the state of the second switch tube S2 in one cycle is: off, off, on, off. The state of the fifth switch tube S5 in one cycle is: off, off switching to on, on, on switching to off.

[0058] Please refer to Figure 4 In the second working mode, the first switch tube S1 is constantly disconnected, the fourth switch tube S4 is constantly turned on, and one cycle is divided into four time periods. The states of the second switch tube S2 in one cycle are: disconnected, disconnected, turned on, and disconnected; the states of the third switch tube S3 in one cycle are: turned on, disconnected, disconnected, and disconnected. The states of the fifth switch tube S5 in one cycle are: disconnected, switched from disconnected to turned on, turned on, switched from turned on to disconnected. In the second working mode, the active clamping capacitor Cb is charged during the startup phase until the voltage on Cb is Vin / 2. Therefore, in steady state, when S3 is turned on, the voltage across the transformer Tr is Vin / 2. Similarly, when S2 is turned on, the voltage on Cb is used as the input voltage to provide energy to the transformer Tr.

[0059] It can be understood that in different embodiments, other forms of output power circuits can be set. In the first working mode and the second working mode, the switching tubes in other output power circuits can be adaptively set to open and close timing according to the theoretical direction of the induced current in the transformer.

[0060] In this embodiment, S3 and S4 cannot be combined into one switch element. Figure 2 If S4 is deleted from the circuit shown, the energy of Cb can be transferred through the diode in S3, so that energy cannot be stored or the energy storage effect is poor, and the entire circuit cannot work as expected.

[0061] The DCDC topology provided in this embodiment has the following beneficial effects:

[0062] 1) This solution can be used not only in 400V systems but also in 800V systems, thereby effectively increasing the use range of vehicle-mounted DCDC power supplies. Based on the same idea, by changing the electrical parameters of each component, it can also be applied to other wide-range input scenarios without any threshold.

[0063] 2) Compared with the two-stage topology and transformer solution, it has fewer components and reduces the cost of the overall vehicle DCDC power supply.

[0064] 3) Compared with the two-stage topology, there is no efficiency loss due to the additional circuit, and the overall efficiency is more advantageous.

[0065] In summary, this embodiment provides a DCDC topology, the core components of the input power circuit of which include only four switching tubes and a capacitor, and the transformer includes only one primary winding. This embodiment also provides a control method that works in conjunction with the above-mentioned DCDC topology. Such a configuration, on the one hand, can support different control timings to meet the requirements of compatibility with a wide range of input voltages, and on the other hand, the structure is simple, which reduces the complexity of the system, reduces costs, improves circuit efficiency, and reduces the probability of system failure, solving the problem of the lack of such a DCDC topology that can meet multiple design requirements in the prior art.

[0066] The above description is only a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A DCDC topology, characterized in that: The DCDC topology includes an input power circuit and a transformer; the transformer includes a primary winding; the input power circuit includes a capacitor, an input positive electrode, an input negative electrode, a first switch tube, a second switch tube, a third switch tube and a fourth switch tube; The input positive electrode, the first switch tube, the capacitor, the second switch tube and the input negative electrode are connected in sequence, the input positive electrode, the fourth switch tube, the third switch tube, the second switch tube and the input negative electrode are connected in sequence, the connection point between the first switch tube and the capacitor is connected to the first end of the primary winding, and the input negative electrode is connected to the second end of the primary winding.

2. The DCDC topology according to claim 1, characterized in that: The DCDC topology switches between the first working mode and the second working mode based on the input voltage; wherein the input voltage corresponding to the first working mode is less than the input voltage corresponding to the second working mode; In the first working mode, the capacitor is used to work as an active clamping capacitor; In the second working mode, the capacitor is first charged to 50%±5% of the input voltage and then used as an energy storage and release element to reduce the ratio of the output voltage to the input voltage of the input end power circuit.

3. The DCDC topology according to claim 1, characterized in that: The DCDC topology includes an output end power circuit, the transformer includes a secondary winding, and the output end power circuit includes a fifth switch tube, an output positive electrode and an output negative electrode; Wherein, the output positive electrode, the fifth switch tube, the secondary winding and the output negative electrode are connected in sequence, or the output positive electrode, the secondary winding, the fifth switch tube and the output negative electrode are connected in sequence; An end of the secondary winding closer to the output negative pole and the first end of the primary winding are the same-named ends.

4. A control method, characterized in that: Acting on the DCDC topology as claimed in claim 1, the control method comprises: Based on the magnitude of the input voltage, determining whether the current working mode is the first working mode or the second working mode; wherein the input voltage corresponding to the first working mode is smaller than the input voltage corresponding to the second working mode; If it is determined to be the first working mode, output a control signal to drive the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to work according to a first control timing sequence, so that the capacitor works as an active clamping capacitor; If it is determined to be the second working mode, the capacitor is first charged to 50%±5% of the input voltage, and then a control signal is output to drive the first switch tube, the second switch tube, the third switch tube and the fourth switch tube to operate according to the second control timing, so that the capacitor works as an energy storage and release element to reduce the ratio of the output voltage to the input voltage of the input power circuit.

5. The control method according to claim 4, characterized in that: In the first control timing, the third switch tube is constantly off, the fourth switch tube is constantly off, one cycle is divided into four time periods, and the state of the first switch tube in one cycle is: on, off, off, off; the state of the second switch tube in one cycle is: off, off, on, off.

6. The control method according to claim 5, characterized in that: The DCDC topology includes an output end power circuit, the transformer includes a secondary winding, and the output end power circuit includes a fifth switch tube, an output positive electrode and an output negative electrode; Wherein, the output positive electrode, the fifth switch tube, the secondary winding and the output negative electrode are connected in sequence, or the output positive electrode, the secondary winding, the fifth switch tube and the output negative electrode are connected in sequence; The control method further includes: in the first control sequence, the state of the fifth switch tube in one cycle is: disconnected, switched from disconnected to connected, connected, and switched from connected to disconnected.

7. The control method according to claim 4, characterized in that: In the second control timing, the first switch tube is constantly off, the fourth switch tube is constantly on, one cycle is divided into four time periods, and the state of the second switch tube in one cycle is: off, off, on, off; the state of the third switch tube in one cycle is: on, off, off, off, off.

8. The control method according to claim 7, characterized in that: The DCDC topology includes an output end power circuit, the transformer includes a secondary winding, and the output end power circuit includes a fifth switch tube, an output positive electrode and an output negative electrode; Wherein, the output positive electrode, the fifth switch tube, the secondary winding and the output negative electrode are connected in sequence, or the output positive electrode, the secondary winding, the fifth switch tube and the output negative electrode are connected in sequence; The control method further includes: in the second control sequence, the state of the fifth switch tube in one cycle is: disconnected, switched from disconnected to connected, connected, and switched from connected to disconnected.

9. The control method according to claim 4, characterized in that: The control method comprises: when the input voltage is less than 500V, determining that the current working mode is the first working mode; when the input voltage is greater than 500V, determining that the current working mode is the second working mode.

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