Transformer

Abstract

A transformer includes a frame and a plurality of coils wound on the frame, wherein the plurality of coils includes: a first primary coil; a second primary coil located above the first primary coil and electrically connected to the first primary coil; a secondary coil located between the first primary coil and the second primary coil; a first auxiliary coil located above the second primary coil; and a second auxiliary coil located above the first auxiliary coil and electrically connected to the first auxiliary coil, wherein the first auxiliary coil has more turns than the second auxiliary coil.

Description

Technical Field

[0001] The present application relates to a transformer, and more particularly to a flyback transformer with an auxiliary winding. Prior Art

[0002] Fast charging is a common requirement in today's consumer electronics. Gallium nitride (GaN) materials, due to their wide bandgap and high saturation rate, are well-suited for high-power and high-frequency chargers. Therefore, designing transformers that operate at high frequencies while maintaining a balanced output efficiency and temperature performance has become a key concern in the industry. Summary of the Invention

[0003] The present application provides a transformer that can balance output efficiency and temperature during high frequency operation.

[0004] The present application provides a transformer comprising a frame; and a plurality of coils wound on the frame, wherein the plurality of coils comprise: a first primary coil; a second primary coil located above the first primary coil and electrically connected to the first primary coil; a secondary coil located between the first primary coil and the second primary coil; a first auxiliary coil located above the second primary coil; and a second auxiliary coil located above the first auxiliary coil and electrically connected to the first auxiliary coil, wherein the number of turns of the first auxiliary coil is greater than that of the second auxiliary coil. Simple diagram description

[0005] FIG1 is a schematic diagram of a flyback transformer according to an embodiment of the present application. FIG. 2 is a schematic diagram illustrating the winding arrangement of multiple coils according to an embodiment of the present application. FIG3 is a schematic diagram of an isolated flyback converter according to an embodiment of the present application. Implementation Method

[0006] Certain terms are used throughout this specification and the following claims to refer to specific components. A person skilled in the art will understand that hardware manufacturers may use different terms to refer to the same component. This specification and the following claims do not distinguish components by name, but rather by their functional differences. Throughout this specification and the following claims, the term "including" is an open-ended term and should be interpreted as meaning "including, but not limited to." Furthermore, the term "coupled" is intended to encompass any direct and indirect electrical connection. Therefore, if a first device is described as being coupled to a second device, this means that the first device may be directly electrically connected to the second device or indirectly electrically connected to the second device through other devices or connections.

[0007] Please refer to Figure 1, which is a schematic diagram of a flyback transformer T1 according to an embodiment of the present application. The flyback transformer T1 comprises a bobbin 10 and multiple coils wound on the bobbin 10. The multiple coils include a first primary coil N1, a secondary coil N2, a second primary coil N3, a first auxiliary coil N4, and a second auxiliary coil N5. The first primary coil N1 is the bottom layer, while the second primary coil N3 is located above and electrically connected to the first primary coil N1. The secondary coil N2 is located between the first and second primary coils N1 and N3. The first auxiliary coil N4 is located above the second primary coil N3, and the second auxiliary coil N5 is located above and electrically connected to the first auxiliary coil N4. Furthermore, insulating layers (Tape1, Tape2, Tape3, and Tape4) are wound between the coils, and an insulating layer (Tape5) is wound above the second auxiliary coil N5. In one embodiment, the insulating layers Tape 1, Tape 2, Tape 3, Tape 4, and Tape 5 can be made of, but are not limited to, tape, resin, or insulating paper. In one embodiment, the thickness of the insulating layer Tape 5 is at least twice the thickness of the insulating layers Tape 1, Tape 2, Tape 3, and Tape 4. In other words, the insulating layer Tape 5 can be composed of more layers of tape than the other insulating layers to ensure sufficient insulation at the outermost layer of the flyback transformer T1. The insulating layer utilizes a closed winding method to conceal the aforementioned coils, preventing exposure of the wires.

[0008] In another embodiment, the flyback transformer T1 may further include a first shielding layer and a second shielding layer, wherein the first shielding layer is located between the first primary winding N1 and the secondary winding N2, and the second shielding layer is located between the second primary winding N3 and the secondary winding N2. In another embodiment, an insulating layer is also provided between the first and second shielding layers and the first primary winding N1, the secondary winding N2, and the second primary winding N3. The first and second shielding layers are not shown in FIG. 1, but in Table 1 below, the first shielding layer is designated E1 and the second shielding layer is designated E2.

[0009] Please refer to Figure 2, which is a schematic diagram illustrating the winding arrangement of multiple coils of a flyback transformer T1 according to a first embodiment of the present application. The first primary coil N1 is wound starting at pin 5 of the flyback transformer T1 and terminates at position X (typically the top of the transformer or any unoccupied pin). The second primary coil N3 is wound starting at position X and terminates at pin 6. Thus, the winding directions of the first and second primary coils N1 and N3 are identical. Similarly, the winding direction of the secondary coil N2 is wound starting at pin 7 of the flyback transformer T1 and terminates at pin 8. The winding direction of the first auxiliary coil N4 is wound starting at pin 2 of the flyback transformer T1 and terminates at pin 3. The winding direction of the second auxiliary coil N5 is wound starting at pin 3 of the flyback transformer T1 and terminates at pin 4. In one embodiment, a first shielding layer and a second shielding layer are respectively provided between the first primary winding N1 and the secondary winding N2, and between the second primary winding N3 and the secondary winding N2. The first and second shielding layers are wound from a floating connection and terminate at pin 4. The first and second shielding layers reduce electromagnetic interference (EMI) between the primary and secondary sides of the flyback transformer T1.

[0010] Please refer to Figure 3, which is a schematic diagram of an isolated flyback converter 1 according to an embodiment of this application. The isolated flyback converter 1 includes a switching transistor Q1, a flyback transformer T1, a diode D1, an input capacitor Cin, and an output capacitor Cout. Specifically, by determining an input voltage Vin and an output voltage Vout, the isolated flyback converter 1 can operate in a steady-state mode.

[0011] In one embodiment, the switching transistor Q1 in the isolated flyback converter 1 can be a high-power transistor, a high-voltage transistor, or a high-frequency transistor made of III-V compound materials. Furthermore, for high-power and high-frequency applications, the switching transistor Q1 can be a gallium nitride high electron mobility transistor (GaN-HEMT). GaN materials are suitable for high-power and high-frequency applications due to their wide bandgap and high saturation rate. In one embodiment, the switching transistor Q1 utilizes an enhancement-mode GaN-HEMT. In another embodiment, the switching transistor Q1 utilizes an enhancement-mode metal oxide semiconductor field effect transistor (E-mode MOSFET) combined with a depletion-mode GaN-HEMT. The flyback transformer T1 includes the flyback transformer disclosed in any of the above embodiments. In one embodiment, to balance output efficiency and temperature at high frequencies for high-power and high-frequency applications, the isolated flyback converter 1 employs an auxiliary winding in the flyback transformer T1. When the isolated flyback converter 1 needs to output different voltages to different systems, the primary-side supply voltage needs to be adjusted. This can be achieved by adjusting the number of turns of the first auxiliary winding N4 and the second auxiliary winding N5 to accommodate the different supply voltages.

[0012] Specifically, the winding arrangement of the multiple coils in the embodiments of the present application can refer to the following rules, allowing the isolated flyback converter 1 to maintain a balanced output efficiency and temperature during high-frequency operation. In one embodiment, the number of turns of the second primary coil N3 is different from the number of turns of the first primary coil N1. In another embodiment, the sum of the number of turns of the first primary coil N1 and the number of turns of the second primary coil N3 can be 4 to 8 times the number of turns of the secondary coil N2. In one embodiment, the number of turns of the secondary coil N2 can be less than the number of turns of the first primary coil N1 and the number of turns of the second primary coil N3. The number of turns of the first auxiliary coil N4 can be at least 3 times greater than the number of turns of the second auxiliary coil N5. The number of turns of the first shielding layer E1 and the second shielding layer E2 can be greater than at least one of the number of turns of the first primary coil N1, the number of turns of the second primary coil N3, and the number of turns of the secondary coil N2. The wire diameters of the first shielding layer E1 and the second shielding layer E2 can be smaller than the wire diameters of the first primary coil N1, the second primary coil N3, and the secondary coil N2. In one embodiment, the strand counts of these coils can be the same or different. The coils can be made of polyamide enameled copper wire (UEW) stranded wire, Litz wire, or TIW triple-insulated single-core wire. These coils can be made of the same or different materials.

[0013] For example, please refer to Table 1, which shows an embodiment of the winding arrangement of multiple coils in the present application. For example, the first primary coil N1 has its two ends coupled to pin 5 and position X, respectively; one end of the first shield layer E1 is coupled to pin 4, and the other end is floating. Because the flyback transformer T1 of the present application operates in high-frequency applications, for example, operating at a frequency of 200k-250kHz, with an input voltage of 90Vac-265Vac, it supports a single output voltage of 20-24V and offers a variety of output specifications: 5V@3A, 9V@3A, 12V@3A, 15V@3A, 20V@3.25A, etc. The number of strands (P) in the first primary coil N1 and the second primary coil N3 can range from 1 to 50, adjusted according to system wattage and operating requirements. For example, a 12-strand (12P) polyamide enameled copper wire (UEW) stranded with a Litz wire (LITZ) with a wire diameter of 0.05-0.5mm, such as 0.12mm, can be wound with 15 and 14 turns, respectively. The secondary coil N2 can be wound with 80-strand (80P) triple-insulated wire (TIW) with a wire diameter of 0.1mm, with 5 turns. In this way, the winding arrangement of the first primary coil N1 and the second primary coil N3 adheres to the following rules: the number of turns of the second primary coil N3 is different from the number of turns of the first primary coil N1, the sum of the number of turns of the first primary coil N1 and the second primary coil N3 is 4-8 times the number of turns of the secondary coil N2, and the number of turns of the secondary coil N2 is less than the number of turns of the first primary coil N1 and the second primary coil N3. This reduces the skin effect of the flyback transformer T1 when operating at high frequencies. The winding methods of other coils in Table 1 below also comply with the above rules and will not be repeated here. Table 1 Coil endpoint Wire Number of laps insulation layer N1 5-X LITZ(UEW) 0.12mm*12P 15 1st floor E1 ---4 UEW 0.13mm*2p 28 1st floor N2 7-8 TIW-M 0.1mm*80p 5 2nd-3rd floor E2 ---4 UEW 0.13mm*2p 28 1st floor N3 X-6 LITZ(UEW) 0.12mm*12P 14 1st floor N4 2-3 UEW 0.23mm*1p 15 1st floor N5 3-4 UEW 0.23mm*1p 4 2nd floor

[0014] In summary, the winding method of multiple coils in the flyback transformer of the present application complies with multiple rules, which can enable the isolated flyback converter to operate at high frequency in compliance with safety regulations and fast charging protocols (Power Delivery), while taking into account output efficiency and temperature. The above description is only a preferred embodiment of the present application. All equivalent changes and modifications made according to the scope of the patent application of the present application should fall within the scope of the present application.

[0015] 1: Isolated flyback converter 2, 3, 4, 5, 6, 7, 8: pins, endpoints X: position, endpoint 10: Skeleton D1: diode Q1: Switching transistor Cin: input capacitance Cout: output capacitance N1: First primary coil N2: Secondary coil N3: Second primary coil N4: First auxiliary coil N5: Second auxiliary coil T1: Flyback transformer Tape1, Tape2, Tape3, Tape4, Tape5: Insulation layer

Claims

1. A transformer comprising: a frame; and a plurality of coils wound on the frame, wherein the plurality of coils comprises: a first primary coil; a second primary coil located on the first primary coil and electrically connected to the first primary coil; a secondary coil located between the first primary coil and the second primary coil; a first auxiliary coil located on the second primary coil; and a second auxiliary coil located on the first auxiliary coil and electrically connected to the first auxiliary coil, wherein the number of turns of the first auxiliary coil is greater than the number of turns of the second auxiliary coil.

2. The transformer as claimed in claim 1, further comprising: a first shielding layer and a second shielding layer, wherein the first shielding layer is located between the first primary coil and the secondary coil, and the second shielding layer is located between the second primary coil and the secondary coil.

3. The transformer as claimed in claim 2, wherein the wire diameters of the first shielding layer and the second shielding layer are smaller than the wire diameters of the first primary coil, the second primary coil, and the secondary coil.

4. The transformer as claimed in claim 2, wherein the number of turns of the first shielding layer and the number of turns of the second shielding layer are greater than at least one of the number of turns of the first primary coil, the number of turns of the second primary coil, and the number of turns of the secondary coil.

5. The transformer as claimed in claim 1, wherein the number of turns of the first auxiliary coil is at least three times the number of turns of the second auxiliary coil.

6. The transformer as claimed in claim 1, wherein the number of turns of the secondary coil is less than the number of turns of the first primary coil and the number of turns of the second primary coil.

7. The transformer as claimed in claim 1, wherein the second primary coil is wound in the same direction as the first primary coil.

8. The transformer as claimed in claim 1, wherein the number of turns of the second primary coil is different from the number of turns of the first primary coil.

9. The transformer as claimed in claim 1, wherein the sum of the number of turns of the first primary coil and the number of turns of the second primary coil is 4 to 8 times the number of turns of the secondary coil.

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