Isolated high-frequency DC / DC converter

Abstract

The utility model discloses an isolation type high-frequency DC / DC converter, which comprises an upper half-bridge resonant converter, a lower half-bridge resonant converter, a first isolation transformer T1, a second isolation transformer T2 and a rectifying circuit, and is characterized in that the upper half-bridge resonant converter and the lower half-bridge resonant converter adopt a heterogeneous design; and only one of the first thyristor K1 and the second thyristor K2 is switched on at any moment t, so that the time division multiplexing control of the upper half-bridge resonant converter and the lower half-bridge resonant converter is realized, and the voltage gain range and the operation efficiency of the converter are improved.

Description

Technical Field

[0001] This utility model relates to the field of power electronics technology, and in particular to an isolated high-frequency DC / DC converter, which is mainly used to improve the voltage gain of a high-frequency DC / DC converter system. Background Technology

[0002] With the rapid development of power electronics technology, high-frequency isolated DC / DC converters are increasingly widely used in renewable energy, electric vehicle charging stations, communication equipment power supply and energy storage systems. The performance of such converters has an important impact on the efficiency, power density and stability of the entire system. Among the many converter topologies, resonant DC / DC converters have gradually become the mainstream choice for engineering applications due to their inherent soft-switching characteristics (zero voltage turn-on ZVS and zero current turn-off ZCS), high power density and low electromagnetic interference (EMI). However, existing resonant converters still face some challenges in topology design and operating performance, especially in terms of voltage gain range and efficiency optimization. The following two main technical problems exist: (1) Limited voltage gain range: The voltage gain of existing resonant converters, such as LLC resonant converters, is mainly determined by the resonant parameters and operating frequency. Although a certain gain adjustment can be achieved by changing the switching frequency, the frequency change will significantly affect the operating state of the resonant network, which may lead to the failure of the soft-switching characteristics. At the same time, when the load or input voltage changes significantly, the efficiency of traditional resonant converters usually decreases significantly when achieving wide voltage range adjustment. This limitation on the gain range greatly restricts the application capability of resonant converters under complex operating conditions, especially in scenarios requiring wide-range adjustment of output voltage, such as fast charging equipment for electric vehicles and distributed energy storage units. (2) Efficiency degradation over a wide voltage range: Resonant converters can achieve high efficiency near their resonant frequency, but when the gain requirement deviates from the design point, the converter's operating frequency needs to be significantly offset from the resonant frequency, leading to increased switching and conduction losses, thus reducing efficiency. In addition, traditionally symmetrically designed resonant converters are difficult to simultaneously achieve efficient operation under both light and heavy load conditions over a wide voltage range. Especially under heavy load conditions, the amplitude of the resonant current increases significantly, leading to increased thermal stress on lossy components in the circuit, thereby further reducing efficiency and system reliability.

[0003] Therefore, there is an urgent need for a new type of topology that can broaden the voltage gain range while ensuring that the system maintains high operating efficiency over a wide range. Utility Model Content

[0004] This utility model relates to an isolated high-frequency DC / DC converter, aiming to solve the problems of limited voltage gain range and difficulty in guaranteeing efficiency over a wide voltage range in existing resonant converters. Through the designed upper and lower half-bridge resonant converter topology, the output voltage range of the converter is extended, while simultaneously improving the reliability and efficiency of system operation. It mainly includes the following:

[0005] To achieve the above objectives, the technical solution provided by this utility model is as follows:

[0006] An isolated high-frequency DC / DC converter includes: a primary-side circuit, a first isolation transformer T1, a second isolation transformer T2, and a rectifier circuit. The primary-side circuit includes an upper half-bridge resonant converter and a lower half-bridge resonant converter. At any given time t, only one of the first thyristors K1 and the second thyristor K2 is turned on, thereby achieving time-division multiplexing control of the upper and lower half-bridge resonant converters.

[0007] Furthermore, the upper half-bridge resonant converter includes a first switch S1 and a second switch S2, a first resonant inductor L1, a first resonant capacitor C1, a first isolation transformer T1, and a first bidirectional thyristor K1; wherein, the drain of the first switch S1 is connected to the positive terminal of the primary side first power supply E1, and the source is sequentially connected to the primary winding of the first resonant inductor L1, the first resonant capacitor C1, and the first isolation transformer T1; one end of the first bidirectional thyristor K1 is connected to the primary side of the first isolation transformer T1, and the other end is connected to the negative terminal of the first power supply E1; the drain of the second switch S2 is connected to one end of the first resonant inductor L1, and the source is connected to the negative terminal of the first power supply E1.

[0008] Furthermore, the lower half-bridge resonant converter includes a third switch S3 and a fourth switch S4, a second resonant inductor L2, a second resonant capacitor C2, a second isolation transformer T2, and a second bidirectional thyristor K2; wherein, the drain of the second switch S2 is connected to the positive terminal of the primary side of the second power supply E2, and the source is sequentially connected to the primary winding of the second resonant inductor L2, the second resonant capacitor C2, and the second isolation transformer T2; one end of the second bidirectional thyristor K2 is connected to the primary side of the second isolation transformer T2, and the other end is connected to the negative terminal of the second power supply E2; the drain of the fourth switch S4 is connected to one end of the second resonant inductor L2, and the source is connected to the negative terminal of the second power supply E2.

[0009] Furthermore, the secondary sides of the first isolation transformer T1 and the second isolation transformer T2 are connected in parallel and connected to the AC side of the rectifier circuit. The rectifier circuit adopts a diode bridge rectifier structure, with an output capacitor Co and a load resistor R connected in parallel across its two ends. L The output capacitor Co is selected as a high-frequency, low-ESR capacitor, and the load resistor R L It is a variable resistor.

[0010] Furthermore, the upper half-bridge resonant converter and the lower half-bridge resonant converter adopt a heterogeneous design with different circuit parameters to extend the output voltage range of the converter, including the model of the MOSFET device and the parameters of the resonant inductor and resonant capacitor.

[0011] Furthermore, the primary windings of the first isolation transformer T1 and the second isolation transformer T2 are connected in series via the first thyristor K1 and the second thyristor K2, respectively.

[0012] Furthermore, the first bidirectional thyristor K1 and the second bidirectional thyristor K2 are provided with a current threshold I.

[0013] Furthermore, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 operate in soft-switching mode, adjusting the resonant parameters to achieve zero-voltage turn-on and zero-current turn-off operation.

[0014] Furthermore, the first isolation transformer T1 and the second isolation transformer T2 are high-frequency transformers.

[0015] This invention expands the output voltage range through a heterogeneous upper and lower half-bridge resonant converter, and achieves efficient operation over a wide voltage range through optimized adjustment of resonant parameters. The rectifier bridge and output capacitor design further improve system stability, while the thyristor protection mechanism enhances the system's dynamic response and safety.

[0016] The isolated high-frequency DC / DC converter according to the embodiments of the present invention has at least the following beneficial effects:

[0017] 1. By using the heterogeneous design of the upper half-bridge resonant converter and the lower half-bridge resonant converter in a time-division multiplexing mode, the output voltage range of the converter is significantly expanded to meet the needs of various complex application scenarios. In addition, the secondary circuit adopts a high-frequency, low-ESR output capacitor Co, which significantly reduces the output voltage ripple. At the same time, the high-efficiency rectification performance of the rectifier bridge ensures the stability of the output voltage and the stability of the system operation.

[0018] 2. The upper and lower half-bridge resonant converters are set with different resonant frequencies, ensuring that the switching devices operate in soft-switching mode. Zero-voltage turn-on and zero-current turn-off are achieved by adjusting the resonant parameters, effectively reducing switching losses and electromagnetic interference, and significantly improving system efficiency and stability. The bidirectional thyristors in the primary circuit have overcurrent protection and circuit breaker protection functions, which can quickly disconnect fault circuits under abnormal conditions, improving the safety and reliability of the system. Attached Figure Description

[0019] Figure 1This is a schematic diagram of the topology of an isolated high-frequency DC / DC converter;

[0020] Figure 2 This is a schematic diagram of the output gain of an isolated high-frequency DC / DC converter.

[0021] Figure 3 This is a schematic diagram of thyristor pulses in an isolated DC / DC converter. Detailed Implementation

[0022] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0023] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0024] In the description of this utility model, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0025] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0026] In the description of this utility model, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this utility model. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0027] This utility model relates to a high-efficiency and stable isolated high-frequency DC / DC converter, the structural design and working principle of which are detailed below:

[0028] Figure 1 This is a schematic diagram of the topology of an isolated high-frequency DC / DC converter. The converter includes a primary circuit, a first isolation transformer T1, a second isolation transformer T2, and a rectifier circuit. The primary circuit includes an upper half-bridge resonant converter and a lower half-bridge resonant converter. Only one of the first thyristors K1 and the second thyristor K2 is turned on at any given time t, realizing time-division multiplexing control of the upper and lower half-bridge resonant converters. The entire system achieves energy transfer through a resonant network and electrical isolation and voltage conversion functions through a high-frequency transformer.

[0029] The upper half-bridge resonant converter includes a first switch S1 and a second switch S2, a first resonant inductor L1, a first resonant capacitor C1, a first isolation transformer T1, and a first bidirectional thyristor K1. The drain of the first switch S1 is connected to the positive terminal of the primary side of the first power supply E1, and its source is sequentially connected to the primary winding of the first resonant inductor L1, the first resonant capacitor C1, and the first isolation transformer T1. One end of the first bidirectional thyristor K1 is connected to the primary side of the first isolation transformer T1, and the other end is connected to the negative terminal of the first power supply E1. The drain of the second switch S2 is connected to one end of the first resonant inductor L1, and its source is connected to the negative terminal of the first power supply E1. Its resonant frequency is fr1.

[0030] The lower half-bridge resonant converter includes a third switch S3 and a fourth switch S4, a second resonant inductor L2, a second resonant capacitor C2, a second isolation transformer T2, and a second bidirectional thyristor K2. The drain of the second switch S2 is connected to the positive terminal of the primary side of the second power supply E2, and its source is sequentially connected to the primary windings of the second resonant inductor L2, the second resonant capacitor C2, and the second isolation transformer T2. One end of the second bidirectional thyristor K2 is connected to the primary side of the second isolation transformer T2, and the other end is connected to the negative terminal of the second power supply E2. The drain of the fourth switch S4 is connected to one end of the second resonant inductor L2, and its source is connected to the negative terminal of the second power supply E2. Its resonant frequency is fr2.

[0031] The upper and lower half-bridge resonant converters couple the energy of the DC power supply to the rectifier circuit through the resonant cavity composed of their respective resonant inductors, resonant capacitors, and isolation transformers. In this process, soft switching of the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 in the input switching network can be achieved to reduce switching losses.

[0032] The secondary windings of the first isolation transformer T1 and the second isolation transformer T2 are connected in parallel and connected to the AC side of the rectifier circuit. The rectifier circuit adopts a diode bridge rectifier structure, with an output capacitor Co and a load resistor R connected in parallel across its two ends. L The output capacitor Co is a high-frequency, low-ESR capacitor used to filter out ripple and improve the stability of the output voltage. The load resistor R... L It is a variable resistor used for performance testing under different load conditions.

[0033] The upper and lower half-bridge resonant converters adopt a heterogeneous design with different circuit parameters to extend the output voltage range of the converter, including the model of the MOSFET device and the parameters of the resonant inductor and resonant capacitor.

[0034] The first isolation transformer T1 and the second isolation transformer T2 are high-frequency transformers. The primary side is connected in series with the first thyristor K1 and the second thyristor K2 respectively. The first bidirectional thyristor K1 and the second bidirectional thyristor K2 are set with a current threshold I. When the circuit operating current exceeds the current threshold I, the circuit is disconnected to realize the overcurrent protection function.

[0035] The first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 operate in soft-switching mode, adjusting the resonant parameters to achieve zero-voltage turn-on and zero-current turn-off operation.

[0036] The upper and lower half-bridge resonant converters employ a heterogeneous design, with different circuit parameters for the MOSFET device types, resonant inductors, and resonant capacitors, respectively. (See [link to relevant documentation]). Figure 2 This diagram illustrates the output gain of an isolated high-frequency DC / DC converter. Curve AB represents the gain curve of the upper half-bridge resonant converter, and curve BC represents the gain curve of the lower half-bridge resonant converter. Point A is the highest output voltage, point B is the critical voltage point for switching the operating modes of the two resonant converters, and point C is the lowest output voltage. It can be seen that the voltage gain is higher within the operating frequency offset range of fr1, and lower within the operating frequency offset range of fr2. Therefore, the operating modes of the upper and lower half-bridge resonant converters can be switched according to the converter's voltage gain range, achieving gain expansion of the converter to [specific parameters]. Figure 2 The shaded area in the diagram effectively improves the voltage gain range by setting the resonant cavity 1 and 2 to be time-division multiplexed, and ensures that the converter operates near the resonant frequency in both operating modes. This ensures that the switching transistors in the resonant network operate in soft-switching mode, reduces switching losses, and improves the converter's operating efficiency.

[0037] Figure 3This diagram illustrates the thyristor pulses of an isolated DC / DC converter. The switching of the operating modes of the upper and lower half-bridge resonant converters is controlled by turning the first thyristor K1 and the second thyristor K2 on and off. For example, when the output gain is high, resonant cavity 1 operates, with G1 = 1 and G2 = 0; when the output gain is low, resonant cavity 2 operates, with G1 = 0 and G2 = 1. In other embodiments of this invention, multiple voltage output gain thresholds can be set to further constrain the converter's operating modes.

[0038] Through the topology and parameter design of this converter, the resonant converter meets the requirement of obtaining a wide voltage gain range at a narrower switching frequency, reduces the design requirements of the transformer, and improves the efficiency and safety of the converter.

[0039] In other embodiments of this utility model, the output voltage range can also be adjusted by adjusting the parameter ranges of the first power supply E1 and the second power supply E2, thereby further increasing the range of input and output voltage variations.

[0040] In summary, the isolated high-frequency DC / DC converter adopted in this invention solves the problems of small voltage gain range and low operating efficiency when operating off-resonant frequency in the prior art by using a time-division multiplexing operation mode of the heterogeneously designed upper and lower half-bridge resonant converters.

[0041] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. An isolated high-frequency DC / DC converter, comprising: The primary circuit, a first isolation transformer T1, a second isolation transformer T2, and a rectifier circuit are characterized in that the primary circuit includes an upper half-bridge resonant converter and a lower half-bridge resonant converter, wherein only one of the first bidirectional thyristors K1 and the second bidirectional thyristor K2 is turned on at any given time t, realizing time-division multiplexing control of the upper and lower half-bridge resonant converters; the upper half-bridge resonant converter includes a first switch S1 and a second switch S2, a first resonant inductor L1, a first resonant capacitor C1, a first isolation transformer T1, and a first bidirectional thyristor K1; wherein the drain of the first switch S1 is connected to the positive terminal of the primary side first power supply E1, and the source is sequentially connected to the first resonant inductor L1, the first resonant capacitor C1, and the primary winding of the first isolation transformer T1; one end of the first bidirectional thyristor K1 is connected to the primary side of the first isolation transformer T1, and the other end is connected to the negative terminal of the first power supply E1; the drain of the second switch S2 is connected to one end of the first resonant inductor L1, and the source is connected to the negative terminal of the first power supply E1.

2. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The lower half-bridge resonant converter includes a third switch S3 and a fourth switch S4, a second resonant inductor L2, a second resonant capacitor C2, a second isolation transformer T2, and a second bidirectional thyristor K2. The drain of the second switch S2 is connected to the positive terminal of the primary side of the second power supply E2, and its source is sequentially connected to the primary windings of the second resonant inductor L2, the second resonant capacitor C2, and the second isolation transformer T2. One end of the second bidirectional thyristor K2 is connected to the primary side of the second isolation transformer T2, and the other end is connected to the negative terminal of the second power supply E2. The drain of the fourth switch S4 is connected to one end of the second resonant inductor L2, and its source is connected to the negative terminal of the second power supply E2.

3. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The secondary windings of the first isolation transformer T1 and the second isolation transformer T2 are connected in parallel and connected to the AC side of the rectifier circuit. The rectifier circuit adopts a diode bridge rectifier structure, with an output capacitor Co and a load resistor R connected in parallel across its two ends. L The output capacitor Co is selected as a high-frequency, low-ESR capacitor, and the load resistor R L It is a variable resistor.

4. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The upper and lower half-bridge resonant converters adopt a heterogeneous design with different circuit parameters to extend the output voltage range of the converter, including the model of the MOSFET device and the parameters of the resonant inductor and resonant capacitor.

5. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The primary windings of the first isolation transformer T1 and the second isolation transformer T2 are connected in series via the first bidirectional thyristor K1 and the second bidirectional thyristor K2, respectively.

6. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The first bidirectional thyristor K1 and the second bidirectional thyristor K2 are provided with a current threshold I.

7. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The first switch S1, the second switch S2, the third switch S3 and the fourth switch S4 operate in soft-switching mode, adjusting the resonant parameters to achieve zero-voltage turn-on and zero-current turn-off operation.

8. The isolated high-frequency DC / DC converter according to claim 1, characterized in that, The first isolation transformer T1 and the second isolation transformer T2 are high-frequency transformers.

Images