A high-voltage isolation transformer for a switching power supply and a method of manufacturing the same

Abstract

This invention discloses a switching power supply transformer and its manufacturing method. The transformer includes a magnetic core made of PC95 material, a leaded frame, and a primary winding N1, a shielding winding E1, an auxiliary power supply winding N2, a feedback winding N3, and a secondary winding N4 wound on it. Its innovation lies in: the auxiliary power supply winding N2 and the shielding winding E1 are wound synchronously in one layer, with the winding sequence as follows: primary winding N1, auxiliary power supply winding N2 and shielding winding E1 wound synchronously, feedback winding N3, and secondary winding N4; double-layer insulating tape with an overlap width of not less than 3mm is used to strengthen the insulation between the primary and secondary windings; all unnecessary leads are removed to ensure safe spacing; key leads are sleeved with polytetrafluoroethylene (PTFE) tubing; and the magnetic core center post is glued. The transformer of this invention optimizes the manufacturing process, saves material costs, has a reliable structure, high conversion efficiency, high insulation strength, can pass the 3.75kVAC withstand voltage test, and has good common-mode noise suppression, making it particularly suitable for switching power supplies requiring high safety and EMC certification.

Description

Technical Field

[0001] This invention relates to the field of electronic components technology, specifically to a high-voltage isolation transformer for switching power supplies and its manufacturing method. Background Technology

[0002] The switching power supply transformer is the core magnetic component in a switching power supply circuit, and its performance directly affects the power supply's conversion efficiency, power density, electromagnetic compatibility (EMC), and safety. As electronic devices place increasingly higher demands on power supplies, especially in applications requiring stringent safety certifications (such as UL certification), greater challenges are being placed on the transformer's insulation design, noise suppression, and structural reliability.

[0003] Traditional switching power supply transformers often suffer from the following shortcomings in winding technology, insulation treatment, and pin configuration: insufficient insulation strength between the primary and secondary windings, making it difficult to pass high withstand voltage tests; limited common-mode noise suppression; complex multi-layer winding structure, low winding efficiency, and poor consistency; and excessive pins may lead to insufficient electrical clearance and creepage distance, posing safety risks. Therefore, there is an urgent need for a switching power supply transformer design scheme that is structurally optimized, technologically reliable, and easily meets safety certification requirements. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a switching power supply transformer with a compact structure, reliable insulation performance, good electromagnetic compatibility, and standardized manufacturing process, as well as its manufacturing method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A high-voltage isolation transformer for switching power supplies, comprising: The magnetic core is made of PC95 soft magnetic ferrite material, which has the characteristics of low loss and high permeability at high frequencies. The frame, model AQT-2718(5+0), has first to fifth pins, as well as a first lead and a second lead on the frame; The primary winding N1 is made of 8 strands of stranded enameled wire with a diameter of 0.15mm. The starting end is connected to the third pin and the ending end is connected to the fourth pin. There are a total of 30 turns, which are evenly distributed in two layers. The shielding winding E1 is made of flat enameled wire with a width of 0.15 mm and a thickness of 3 mm. The starting end is connected to the second pin, and the ending end is a non-connection end. It has a total of 5 turns and is wound synchronously with the primary winding N2 to form a Faraday shielding layer. The auxiliary power supply winding N2 is made of 3 strands of enameled wire with a diameter of 0.15 mm. The starting end is connected to the first pin and the ending end is connected to the second pin, with a total of 5 turns. The feedback winding N3 uses triple-insulated wire with a diameter of 0.1 mm and a parallel structure of 75 strands × 2. The starting end is connected to the first lead on the bobbin, and the ending end is connected to the second lead. It has a total of 4 turns, and its lead wires are led out from the top of the bobbin. The secondary winding N4 is made of 8 strands of stranded enameled wire with a diameter of 0.15mm. The starting end is connected to the fourth pin and the ending end is connected to the fifth pin, for a total of 14 turns. Each winding is wrapped with at least two layers of UL-certified insulating tape between each other and between the winding and the magnetic core.

[0006] Furthermore, the leads of the feedback winding N3 and the auxiliary power supply winding N2 are fitted with polytetrafluoroethylene insulating sleeves to enhance the insulation strength and temperature resistance between the leads.

[0007] Furthermore, one end of the shielding winding E1 is connected to the primary side reference ground, while the other end is left floating or grounded through a Y capacitor, forming an effective common-mode noise discharge path and significantly improving the product's EMC performance.

[0008] Furthermore, the winding sequence of the windings on the skeleton is as follows: the primary winding N1 is wound in the innermost layer, the auxiliary power supply winding N2 and the shielding winding E1 are wound synchronously on it as the second layer, and then the feedback winding N3 and the secondary winding N4 are wound in sequence.

[0009] Furthermore, the insulation layer between the primary winding N1 and the secondary winding N4 is covered with two layers of UL-certified insulating tape in a reverse folding manner, with the overlap width of the reverse folds not less than 3mm, to meet the withstand voltage test requirements of up to 3.75kVAC.

[0010] Furthermore, the edge of the magnetic core near the first to fifth pins is covered with two layers of UL-certified insulating tape to cover the edge of the magnetic core near the first to fifth pins, preventing short circuits caused by burrs on the magnetic core; and the center post of the magnetic core is coated with fixing adhesive to prevent the magnetic core from loosening and causing abnormal noise.

[0011] Furthermore, after the termination end of the shielding winding E1 is led out, it is pressed onto the insulation layer on its own outer side to ensure that the end of the wire is firmly fixed and to avoid the risk of short circuit caused by lifting.

[0012] Furthermore, the fourth pin is trimmed to retain 1 / 3 of its original length, and all other pins not connected to any windings (such as NC pins) are completely removed to increase the physical spacing between pins.

[0013] Furthermore, after removing the pins with unconnected windings, the minimum electrical clearance between any two adjacent remaining pins is not less than 2.5 mm, and the minimum creepage distance is not less than 3.0 mm, which fully complies with the safety specifications for reinforced insulation.

[0014] The present invention also provides a method for manufacturing the above-mentioned switching power supply transformer, comprising the following steps: S1. Wind the primary winding N1 on the skeleton, and after winding, wrap at least two layers of UL certified insulating tape around the primary winding N1. S2. Simultaneously wind the auxiliary power supply winding N2 and the shielding winding E1 on the insulating tape, and after the winding is completed, cover it with at least one layer of UL certified insulating tape; S3. Wind the feedback winding N3 and the secondary winding N4 in sequence, and wrap each winding with at least one layer of UL-certified insulating tape after completion. S4. Polytetrafluoroethylene insulating sleeves are respectively fitted on the lead wires of the second pin, the third pin, the first lead and the second lead, and double-layer reverse-folded UL certified insulating tape is used to reinforce the insulation in the isolation area between the primary winding and the secondary winding. S5. Before assembling the magnetic core, trim the fourth pin to 1 / 3 of its original length and remove all pins not connected to the winding; S6. Assemble the magnetic core to the frame, wherein the edge of the magnetic core near the first to fifth pins is covered with two layers of UL-certified insulating tape, and the center post of the magnetic core is dotted with fixing adhesive.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. Excellent insulation and safety performance: Through the combined design of "multi-layer insulating tape wrapping", "reverse folding and overlapping wrapping (width ≥ 3mm)" and "removing excess pins and ensuring safe spacing", the insulation strength between the primary and secondary windings is significantly enhanced, ensuring that the product can easily pass the 3.75kVAC withstand voltage test and meet the stringent safety certification requirements.

[0016] 2. Excellent electromagnetic compatibility: By setting up an independent shielded winding E1 and connecting one end of it to the primary reference ground, common-mode noise between the primary and secondary windings is effectively suppressed, improving the EMC performance of the transformer.

[0017] 3. High reliability structure: The process details such as wrapping the magnetic core edge with tape to prevent leakage, fixing the center column with glue, and pressing the shielding winding wire ends improve the mechanical stability and environmental adaptability of the transformer.

[0018] 4. Standardized and efficient process: The clear winding sequence (N1→N2 and E1 are wound synchronously → N3→N4) and insulation steps standardize the manufacturing process, ensuring product consistency and yield, making it particularly suitable for large-scale production. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the structure of a switching power supply transformer according to an embodiment of the present invention. Figure 2 This is a schematic diagram of the winding sequence and insulation structure of a winding according to an embodiment of the present invention.

[0020] In the attached diagram, each label represents: 1. First pin, 2. Second pin, 3. Third pin, 4. Fourth pin, 5. Fifth pin, 6. Magnetic core, 7. Frame, 8. First lead-out terminal, 9. Second lead-out terminal, N1. Primary winding, E1. Shielding winding, N2. Auxiliary power supply winding, N3. Feedback winding, N4. Secondary winding, 10. Insulating tape, 11. Polytetrafluoroethylene sleeve. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0022] Reference Figure 1 and Figure 2 This embodiment provides a switching power supply transformer with model number WH075W-A 12V. The transformer includes a magnetic core 6 made of PC95 soft magnetic ferrite material and a frame 7 with model number AQT-2718 (5+0). The frame 7 has first to fifth pins (Pin1-Pin5, corresponding to 1-5 in the figure), and two first leads 8 and second leads 9 located at the top of the frame.

[0023] The specific winding process is as follows: The first step involves twisting eight strands of 0.15mm diameter enameled wire together to form the primary winding N1, starting from pin 3 and ending at pin 4, for a total of 30 turns, evenly distributed across two layers. After completion, cover with two layers of UL-certified insulating tape.

[0024] The second step involves simultaneously winding the auxiliary power supply winding N2 and the shielding winding E1 onto the insulation layer from the first step. N2 uses three strands of 0.15mm diameter enameled wire, wound 5 turns from pin 1 to pin 2. E1 uses a 0.15mm wide, 3mm thick flat enameled wire, wound 5 turns starting from pin 2, with the take-up end pressed onto insulating tape. Both are wound in the same layer. After completion, a layer of UL-certified insulating tape is applied.

[0025] The third step involves winding the feedback winding N3 onto the insulation layer from the second step. Using 0.1mm diameter, 75 strands x 2 in parallel triple-insulated wire, wind 4 turns from the first lead 8 to the second lead 9. After completion, cover with a layer of UL-certified insulating tape.

[0026] Fourth, on the insulation layer from step three, wind the secondary winding N4. Twist eight strands of 0.15mm diameter enameled wire together, starting from pin 4 and ending at pin 5, for a total of 14 turns. After completion, cover with two layers of UL-certified insulating tape.

[0027] Key process handling: In the insulation area between the primary winding N1 (and E1) and the secondary winding N4, two layers of UL-certified insulating tape 10 are used for reinforcement wrapping in a reverse folding manner (i.e., the tape is folded back on one side of the frame 7 and then wrapped around). The width of the overlapping part of the reverse folding is controlled to be 3.5mm to ensure sufficient insulation distance.

[0028] Polytetrafluoroethylene sleeves 11 are fitted onto the leads connected to the third pin 3 (Pin3), the second pin 2 (Pin2), the first lead 8, and the second lead 9, respectively. The sleeves of the auxiliary power supply winding N2 and the feedback winding N3 extend to the vicinity of the first pin 1 (Pin1) to provide sufficient insulation protection.

[0029] Before assembling the magnetic core 6, the fourth pin 4 (Pin 4) was trimmed to approximately 1 / 3 of its original length using a tool, and all redundant pins on the frame 7 that were not connected to any winding were completely removed from the root. Measurements showed that the minimum electrical clearance between adjacent active pins after processing was 2.8 mm, and the minimum creepage distance was 3.2 mm, meeting safety standards.

[0030] Assemble the magnetic core 6 into the wound frame 7. Wrap two layers of UL-certified insulating tape 10 around the edge of the magnetic core 6 near the pins, ensuring no part of the magnetic core 6 is exposed. Apply a suitable amount of fixing adhesive (such as silicone rubber) to the center post of the magnetic core 6 to enhance structural stability.

[0031] Finally, the model number “WH075W-A 12” is printed on the top of the transformer.

[0032] The transformer manufactured by the above method can withstand a 3.75kVAC withstand voltage test for 5 seconds between its primary winding N1 and secondary winding N4 without breakdown or flashover. The shielding winding E1 effectively reduces conducted common-mode noise. The overall structure is robust and reliable, fully meeting the target application and certification requirements.

[0033] Example 2: Different configurations and pin variations of the shielding winding Based on Example 1, this example provides another design variation.

[0034] The termination (non-connection) end of the shielding winding E1 can be connected to the ground reference point on the primary side via a 2200pF Y capacitor, instead of being left floating, to further optimize the common-mode noise suppression effect in a specific frequency band.

[0035] Furthermore, the fourth pin can also be cut to 40% of its original length (rather than precisely 1 / 3), as long as the minimum electrical clearance requirement is met after cutting. The overlap width of the folded insulating tape can be selected from any value between 3mm and 5mm to achieve good insulation performance.

[0036] The other parts of this embodiment are the same as those in Embodiment 1.

[0037] Example 3: Explanation of Equivalent Material Substitution and Winding Method This invention is not limited to the specific material specifications described in the embodiments. For example, the magnetic core can also be made of other soft magnetic ferrite materials (such as PC44) with similar magnetic properties; the polytetrafluoroethylene insulating sleeve can be replaced by other sleeve materials with equivalent high temperature resistance and high insulation performance.

[0038] Regarding the winding method, the "uniform distribution" and "centrally close winding" are only preferred methods to achieve winding regularity. Other winding arrangement methods well known to those skilled in the art can also be adopted without affecting electrical performance and insulation requirements.

[0039] The other parts of this embodiment are the same as those in Embodiment 1.

[0040] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-voltage isolation transformer for switching power supplies, characterized in that, include: The magnetic core is made of PC95 soft magnetic ferrite material; The frame has first to fifth pins, and a first lead-out terminal and a second lead-out terminal disposed on the frame; The primary winding N1 is made of 8 strands of stranded enameled wire with a diameter of 0.15mm. The starting end is connected to the third pin and the ending end is connected to the fourth pin, for a total of 30 turns. The shielding winding E1 is made of flat enameled wire with a width of 0.15 mm and a thickness of 3 mm. The starting end is connected to the second pin, and the ending end is a non-connection end. It has a total of 5 turns and is wound synchronously with the auxiliary power supply winding N2. The auxiliary power supply winding N2 is made of 3 strands of enameled wire with a diameter of 0.15 mm. The starting end is connected to the first pin and the ending end is connected to the second pin, with a total of 5 turns. The feedback winding N3 uses triple-insulated wire with a diameter of 0.1 mm and a parallel structure of 75 strands × 2. The starting end is connected to the first lead on the bobbin, and the ending end is connected to the second lead. It has a total of 4 turns, and its lead wires are led out from the top of the bobbin. The secondary winding N4 is made of 8 strands of stranded enameled wire with a diameter of 0.15mm. The starting end is connected to the fourth pin and the ending end is connected to the fifth pin, for a total of 14 turns. Each winding is wrapped with at least two layers of UL-certified insulating tape between each other and between the winding and the magnetic core.

2. The high-voltage isolation transformer according to claim 1, characterized in that: The lead wires of the feedback winding N3 and the auxiliary power supply winding N2 are fitted with polytetrafluoroethylene insulating sleeves.

3. The high-voltage isolation transformer according to claim 1, characterized in that: One end of the shielding winding E1 is connected to the primary side reference ground, and the other end is left floating or grounded through a Y capacitor to suppress common-mode noise.

4. The high-voltage isolation transformer according to claim 1, characterized in that, The winding sequence of the windings on the frame is as follows: the primary winding N1 is wound in the innermost layer, the auxiliary power supply winding N2 and the shielding winding E1 are wound synchronously on top of it as the second layer, and then the feedback winding N3 and the secondary winding N4 are wound in sequence.

5. The high-voltage isolation transformer according to claim 1, characterized in that: The insulating layer between the primary winding N1 and the secondary winding N4 is covered with two layers of UL-certified insulating tape wrapped in a reverse folding manner, with the overlap width of the reverse folds not less than 3mm.

6. The high-voltage isolation transformer according to claim 1, characterized in that: The magnetic core is covered with two layers of UL-certified insulating tape on the edge near the first to fifth pins; and the central column of the magnetic core is coated with fixing adhesive.

7. The high-voltage isolation transformer according to claim 1, characterized in that: The termination end of the shielding winding E1 is led out and pressed onto the insulating layer on its outer side.

8. The high-voltage isolation transformer according to claim 1, characterized in that: The fourth pin was cut to one-third of its original length, and the remaining pins that were not connected to any windings were completely removed.

9. The high-voltage isolation transformer according to claim 8, characterized in that: After removing pins with unconnected windings, the minimum electrical clearance between any two adjacent remaining pins shall not be less than 2.5 mm, and the minimum creepage distance shall not be less than 3.0 mm.

10. A method for manufacturing a switching power supply transformer as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Wind the primary winding N1 on the skeleton, and after winding, wrap at least two layers of UL certified insulating tape around the primary winding N1. S2. Simultaneously wind the auxiliary power supply winding N2 and the shielding winding E1 on the insulating tape, and after the winding is completed, cover it with at least one layer of UL certified insulating tape; S3. Wind the feedback winding N3 and the secondary winding N4 in sequence, and wrap each winding with at least one layer of UL-certified insulating tape after completion. S4. The leads of the second pin, the third pin, the first lead and the second lead are respectively covered with polytetrafluoroethylene insulating sleeves, and double-layer reverse-folded UL certified insulating tape is used to reinforce the insulation in the isolation area between the primary winding and the secondary winding. S5. Before assembling the magnetic core, trim the fourth pin to 1 / 3 of its original length and remove all pins not connected to the winding; S6. Assemble the magnetic core to the frame, wherein the edge of the magnetic core near the first to fifth pins is covered with two layers of UL-certified insulating tape, and the center post of the magnetic core is dotted with fixing adhesive.

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