Ultra-wideband isolation transformer

Abstract

The application discloses an ultra-wideband isolation transformer, which comprises a magnetic core, a primary winding and a secondary winding, the primary winding is a tap double-winding structure composed of series connection of a first wire and a second wire, the secondary winding is a tap double-winding structure composed of series connection of a third wire and a fourth wire, the primary winding and the secondary winding are twisted into a double-twisted wire, the turn ratio of the double-twisted wire is 1:1, the coupling coefficient is close to 1, and the double-twisted wire is wound on the magnetic core. The application can obviously reduce the insertion loss of the transformer, the transformer is no longer limited to 3dB bandwidth limitation, and provides an implementation basis that the full-band loss of 0.1MHz-300MHz is lower than 0.6dB. Meanwhile, the application also has an inter-stage withstand voltage higher than 800V, and the reliability of the product is improved. Meanwhile, the application has expansibility, the high end of the working frequency band can be further widened to a use frequency higher than 6GHz. The processing method is simple, the structural consistency is relatively strong, and the processing and manufacturing cost is effectively reduced.

Description

Technical Field

[0001] This invention relates to a transformer structure, and more particularly to an ultra-wideband isolation transformer. Background Technology

[0002] Ultra-wideband isolation transformers are widely used in power conversion and signal isolation circuits of various power levels. They primarily function as isolation, voltage transformation, impedance transformation, chip driving, and waveform distortion suppression. Characterized by wide operating frequency, good performance consistency, and small size, they are indispensable magnetic components in RF and IF circuits and power supplies. Applicable to various equipment platforms, they are key components affecting the overall system size and performance.

[0003] The typical applications of ultra-wideband isolation transformers are as follows: (1) The first is used for broadband balun transformation, which can isolate DC, perform balanced-unbalanced transformation, and port impedance matching. It can effectively reduce the influence of noise and crosstalk on differential signals and improve signal transmission efficiency. It is often used in push-pull circuits of RF power amplifier modules, transceiver antenna systems, and communication systems. (2) The second is used as a pulse signal transformer. In order to improve the reliability and stability of the entire system, the current centralized power supply system is far from meeting the requirements. Distributed power supply has become the mainstream solution. In modern phased array radar systems, each T / R component is equipped with an independent power supply, which will inevitably increase the volume and weight of the entire system. At the same time, due to the increase in the number of power supplies, the requirements for stability and reliability are also very high. In order to reduce the weight and size of the equipment, modern electronic equipment generally uses high-frequency switching power supplies. The core component for energy conversion in switching power supplies is undoubtedly the broadband isolation transformer. The weight, volume, and working stability and reliability of the broadband isolation transformer play a crucial role in the entire power supply system. (3) The third is used as a power transformer. In some power supplies, broadband isolation transformers are required to boost the voltage of transceiver chips to drive them and simultaneously isolate the voltage, protecting the power supply in critical equipment. Using broadband isolation transformers can effectively improve the reliability and efficiency of power supply to equipment.

[0004] However, with the development of electronic information technology, the demand for ultra-wideband isolation transformers is also increasing. Ultra-wideband isolation transformers should ensure the following two requirements: (1) wide bandwidth and low power consumption; (2) high isolation. The first requirement is that ultra-wideband isolation transformers not only have a wide operating frequency, but also sufficiently low insertion loss within the frequency band. The high and low frequency electrical performance design of broadband isolation transformers is mutually restrictive and has a high design difficulty. The second requirement is that ultra-wideband isolation transformers have sufficiently high isolation voltage. To achieve this goal, the traditional design method is to use isolation winding design for transformers, including random winding, layered flat winding, segmented layered winding, etc. These winding methods all have the problems of small coupling coefficient and large leakage inductance, resulting in large transformer losses.

[0005] To better illustrate the shortcomings of the prior art, we refer to the accompanying drawings in the specification. Figure 1 , Figure 2 For example: Figure 1 This paper presents a common broadband isolation transformer circuit—a lumped-parameter isolation winding structure transformer, comprising a primary coil, a rectangular magnetic core, and a secondary coil. Both the primary and secondary coils are constructed using enameled wire through random winding, layered flat winding, or segmented layered winding. The rectangular magnetic core is made of soft magnetic ferrite material. This transformer primarily relies on magnetic field coupling to achieve a high interstage isolation voltage. A drawback of this structure is that, under actual operating conditions, due to the physical structure of the windings, magnetic flux is generated when voltage and current travel from the primary winding to the secondary winding via the magnetic field. Since magnetic field flow follows the path of least electromagnetic resistance, not all the magnetic flux generated by the primary winding passes through the secondary winding. This leakage flux leads to transformer energy loss and leakage inductance, such as… Figure 2 As shown, this results in a narrower transformer bandwidth, reduced efficiency, and increased losses.

[0006] Therefore, designing a low-loss, high-isolation ultra-wideband isolation transformer within a wide bandwidth is of great significance. Summary of the Invention

[0007] The purpose of this invention is to provide an ultra-wideband isolation transformer that solves the above-mentioned problems and features wide bandwidth, low loss, and high isolation.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an ultra-wideband isolation transformer, comprising a magnetic core, a primary winding, and a secondary winding, wherein the primary winding is a tapped double winding structure composed of a first conductor and a second conductor connected in series, including a tapped end P1 located in the middle and two tail ends P2 and P3; the secondary winding is a tapped double winding structure composed of a third conductor and a fourth conductor connected in series, including a tapped end P4 located in the middle and two tail ends P5 and P6;

[0009] The primary and secondary windings are twisted into a twisted pair with a turns ratio of 1:1 and a coupling coefficient of 0.9-0.99.

[0010] The twisted pair is wound around the magnetic core, with the tapped end in the middle and the tail end at both ends; the length of the twisted pair is less than λ / 4; λ is the wavelength of the transmitted signal.

[0011] Preferably, the magnetic core is made of soft magnetic ferrite with a wide temperature range and low loss.

[0012] Preferably, the first conductor, the second conductor, the third conductor, and the fourth conductor are all insulated conductors.

[0013] In this invention, both the primary and secondary windings adopt a tapped double winding structure composed of two insulated wires connected in series. The primary and secondary windings are then twisted to form a twisted pair, which has a stable characteristic impedance. The twist of the twisted double wires that make up the primary and secondary windings is large enough to make the coupling coefficient close to 1. At this time, the primary and secondary winding structure with the maximum coupling coefficient can be obtained, which also avoids the disadvantage that the transmission line transformer cannot isolate the primary and secondary voltages.

[0014] The primary winding consists of a tapped double winding structure formed by the first and second conductors connected in series, with P1, P2, and P3 constituting the primary winding of the transformer. The secondary winding consists of a tapped double winding structure formed by the third and fourth conductors connected in series, with pins P4, P5, and P6 constituting the secondary winding of the transformer. The turns ratio between the primary and secondary windings is 1:1 to achieve a 1:1 impedance ratio, i.e., impedance matching. This tapped double winding structure ensures that the transformer meets the electrical performance requirements at both the 0.1MHz low-frequency end and the 300MHz high-frequency end, while also ensuring product miniaturization, low distortion, and balance when used for unbalanced-to-balanced transformation.

[0015] There is electric field coupling between the primary and secondary windings. This coupling is induced by the coupling capacitance between the two wires, resulting in a voltage signal. The length of the twisted twin wires must be less than λ / 4. The strength of the coupling signal between the two wires in the transmission line is frequency-dependent; the higher the frequency, the stronger the coupling. Therefore, it is necessary to ensure the coupling coefficient at the low-frequency end. The low-frequency electrical performance of the transformer is determined by its inductance. The larger the inductance, the lower the operating frequency. A larger inductance can be achieved by appropriately increasing the number of winding turns.

[0016] Compared with the prior art, the advantages of the present invention are as follows:

[0017] (1) The technical solution of the present invention is to provide an ultra-wideband isolation transformer structure based on the transmission line transformer principle. Compared with the traditional isolation winding structure, this structure can significantly reduce the transformer insertion loss, so that the transformer is no longer limited to the 3dB bandwidth limitation, and provides a basis for realizing a full-band loss of less than 0.6dB from 0.1MHz to 300MHz. At the same time, it also has an inter-stage withstand voltage of more than 800V, which improves the reliability of the product.

[0018] (2) The ultra-wideband isolation transformer based on the transmission line transformer principle has more functions and expandability. The transformer has interstage withstand voltage isolation function. It is designed by the characteristic impedance of the transmission line and is matched with the impedance of the primary and secondary ports. Its high-end operating frequency band will be further widened, reaching the operating frequency above 6GHz, and broadband unbalanced-balanced conversion is realized.

[0019] (3) The processing method of the present invention is simple and the structure is highly consistent, which effectively reduces the processing and manufacturing cost. Attached Figure Description

[0020] Figure 1 This is a structural diagram of a broadband isolation transformer in the prior art;

[0021] Figure 2 for Figure 1 Schematic diagram of magnetic flux and leakage flux of a structural transformer;

[0022] Figure 3 This is a schematic diagram of the structure of the present invention;

[0023] Figure 4 This is a schematic diagram of the isolation transformer with tapped double twisted wire in this invention.

[0024] Figure 5 This is a schematic diagram of the double-twisted wire in this invention;

[0025] Figure 6 This is a schematic diagram of the magnetic core structure;

[0026] Figure 7 This is a diagram showing the insertion loss curve of the present invention;

[0027] Figure 8 This is a schematic diagram of Example 3.

[0028] In the diagram: 1. Primary coil; 2. Secondary coil; 3. Rectangular magnetic core; 4. Leakage flux; 5. Magnetic flux linkage between the two coils; 6. First conductor; 7. Second conductor; 8. Third conductor; 9. Fourth conductor; 10. Magnetic core; 11. Twisted pair; 12. Primary winding; 13. Secondary winding. Detailed Implementation

[0029] The invention will now be further described with reference to the accompanying drawings.

[0030] Example 1: See Figure 1 and Figure 2 A common broadband isolation transformer circuit—a lumped-parameter isolation winding structure transformer—comprises a primary coil 1, a rectangular magnetic core 3, and a secondary coil 2. Both the primary coil 1 and the secondary coil 2 are constructed using enameled wire through random winding, layered flat winding, or segmented layered winding. The rectangular magnetic core 3 is made of soft magnetic ferrite material. This transformer primarily relies on magnetic field coupling to achieve a high interstage isolation voltage. In actual operation, due to the physical structure of the winding coils, when voltage and current travel from the primary coil 1 to the secondary coil 2 via the magnetic field, a magnetic flux is generated, such as... Figure 2 The magnetic flux linkage 5 between the two coils is shown. Magnetic field flow follows the path of least electromagnetic resistance; the magnetic flux generated by the primary coil 1 does not entirely pass through the secondary coil 2. The magnetic flux that does not pass through the secondary coil 2, i.e., leakage flux 4, leads to transformer energy loss and leakage inductance, such as... Figure 2 As shown, this results in a narrower transformer bandwidth, reduced efficiency, and increased losses.

[0031] Example 2: See Figures 3-7 An ultra-wideband isolation transformer includes a magnetic core 10, a primary winding 12, and a secondary winding 13. The primary winding 12 is a tapped double winding structure composed of a first conductor 6 and a second conductor 7 connected in series, including a tapped end P1 located in the middle and two tail ends P2 and P3. The secondary winding 13 is a tapped double winding structure composed of a third conductor 8 and a fourth conductor 9 connected in series, including a tapped end P4 located in the middle and two tail ends P5 and P6.

[0032] The primary winding 12 and the secondary winding 13 are twisted into a twisted pair 11 with a turns ratio of 1:1 and a coupling coefficient of 0.9-0.99.

[0033] The twisted pair 11 is wound around the magnetic core 10, with the tapped end located in the middle and the tail end located at both ends; the length of the twisted pair 11 is less than λ / 4; where λ is the wavelength of the transmitted signal.

[0034] In this embodiment: the magnetic core 10 is made of soft magnetic ferrite with a wide temperature range and low loss. The first wire 6, the second wire 7, the third wire 8, and the fourth wire 9 are all insulated wires.

[0035] Both the primary winding 12 and the secondary winding 13 are transmission lines with stable characteristic impedance, consisting of two conductors. When the primary winding 12 and the secondary winding 13 are twisted into a twisted pair 11, the twist of the twisted pair 11 needs to be sufficiently large, with a coupling coefficient close to 1. In this invention, the coupling coefficient is 0.9-0.99.

[0036] To better illustrate the technical effects of the product of this invention, we tested the actual object using a vector network analyzer under normal temperature conditions, and obtained the following results. Figure 7 , Figure 7 This is an insertion loss curve plotted after testing the product of this invention using a vector network analyzer under normal temperature conditions. The starting frequency during testing was 0.1MHz, and the cutoff frequency was 300MHz. As can be seen from the graph, the insertion loss of the product of this invention is less than 0.6dB at 0.1MHz and less than 0.29dB at 300MHz, which is significantly lower than the total loss of 3.6dB for similar products, effectively improving the efficiency of RF signal transmission.

[0037] Example 3: The product of this invention, an ultra-wideband isolation transformer based on the transmission line transformer principle, possesses more functions and expandability. See [link to relevant documentation]. Figure 8 If withstand voltage isolation is not a consideration in practical applications, the welding method of the transformer can be changed to transform it into a traditional unbalanced-to-balanced RF transformer. Simultaneously, the characteristic impedance of the transmission line can be adjusted by controlling the twist of the transmission line and the diameter of the selected wire, matching it with the impedances of the primary and secondary ports. This further widens the high end of its operating frequency band, reaching frequencies above 6GHz, and achieves broadband unbalanced-to-balanced conversion.

[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An ultra-wideband isolation transformer comprising a magnetic core (10), a primary winding (12) and a secondary winding (13), characterized in that: The primary winding (12) is a tapped double winding structure composed of the first wire (6) and the second wire (7) in series, including a tapping end P1 in the middle and two tail ends P2 and P3; the secondary winding (13) is a tapped double winding structure composed of the third wire (8) and the fourth wire (9) in series, including a tapping end P4 in the middle and two tail ends P5 and P6; The primary winding (12) and the secondary winding (13) are twisted into a double twisted wire (11), the turn ratio of which is 1:1, and the coupling coefficient is 0.9-0.99; The double twisted wire (11) is wound on a magnetic core (10), the tapping end is in the middle, and the tail ends are at both ends; the length of the double twisted wire (11) is less than λ / 4; λ is the wavelength of the transmission signal. The magnetic core (10) is made of a wide-temperature low-loss soft magnetic ferrite.

2. The ultra-wideband isolation transformer of claim 1, wherein: The first wire (6), the second wire (7), the third wire (8) and the fourth wire (9) are all insulated wires.

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