DC / DC converter isolation device

Abstract

The utility model relates to electrical engineering and can be used in secondary power sources to ensure their reliability by increasing the insulation level. The technical result is achieved by a DC / DC converter insulation device consisting of a multilayer printed circuit board with the functional elements of the converter, characterized in that the DC / DC energy conversion element is a planar transformer with primary and secondary windings. The distance between the primary and secondary windings of the planar transformer is 0.076-0.2 mm. Moreover, there are no copper conductors on the outer layers of the multilayer printed circuit board at the core installation location. The conductors on the surface of the multilayer printed circuit board are provided with gaps and covered with an insulating film, and the elements acting as insulators between galvanically unconnected conductors are designed taking into account the permissible voltage during the breakdown voltage test.The technical result of the utility model consists in increasing the reliability of DC / DC converters during long-term operation due to the use of a component isolation device in the converters.

Description

[0001] The utility model relates to electrical engineering and can be used in secondary power supplies to ensure their reliability by increasing the insulation level.

[0002] Transformer and optoelectronic isolation methods are known in the technical field for DC / DC converters. Their use ensures galvanic isolation between the converter's input and output, preventing direct current flow between circuits and improving electrical safety.

[0003] A DC-DC converter with capacitor insulation (RU Patent No. 2653701, published May 14, 2018) is known. The prototype is characterized by the beginning of the transformer's secondary winding being connected to the negative output of the converter, and the end of the transformer's secondary winding being connected to the anode of a rectifier diode. This ensures the required level of insulation between the transformer and capacitors.

[0004] The common drawbacks of the above-mentioned isolation options for DC / DC converters include low reliability due to the use of localized isolation in individual circuit elements. To ensure long-term, reliable operation of the device, it is necessary to improve the isolation level over a wide range.

[0005] The technical result of the utility model consists in increasing the reliability of DC / DC converters during long-term operation due to the use of a component isolation device in the converters.

[0006] The use of this utility model is driven by the need to ensure a high degree of insulation for converters under changing operating conditions. Climate change (humidity >90% and low atmospheric pressure), pollution, large amounts of dust in the air, damage to the printed circuit board, etc., negatively impact the durability of the products, increasing the likelihood of breakdown and short circuit.

[0007] The technical result is achieved by a DC / DC converter insulation device that is a multilayer printed circuit board with the functional elements of the converter, characterized in that the element for converting direct energy into direct energy is a planar transformer with primary and secondary windings, the distance between the primary and secondary windings of the planar transformer is 0.076 mm - 0.2 mm, and on the outer layers of the multilayer printed circuit board at the location of the core installation there are no copper conductors; the conductors on the surface of the multilayer printed circuit board are made with gaps and covered with an insulating film, and the elements that act as insulators between galvanically unconnected conductors are made taking into account the permissible voltage during the breakdown voltage test.

[0008] The essence of the proposed utility model is explained by drawings, where Fig. 1 shows an example of the implementation of a DC / DC isolation device (section of a multilayer printed circuit board).

[0009] In Fig. 1 the following designations are used:

[0010] 1 - multilayer printed circuit board;

[0011] 2 - planar transformer;

[0012] 3 - functional elements of the converter (filters, rectifier diodes, etc.)

[0013] 4 - copper conductors.

[0014] The DC / DC converter isolation device is a multilayer printed circuit board 1 on which the functional elements of the converter are installed, including a planar transformer 2, connected to each other by copper conductors 4.

[0015] The element that transmits energy across the galvanic barrier is a planar transformer with primary and secondary windings. The advantages of using a planar transformer over a conventional transformer include its small size, superior thermal characteristics, and repeatability.

[0016] The production of wound products is performed manually (wire is wound onto a core). Thanks to the use of planar transformer manufacturing technology, the insulation voltage in the insulating layers (prepregs and cores) between the windings reaches up to 5 kV, while the insulation thickness (cores and prepregs) is 0.2 mm. Manufacturing a wound product with similar characteristics is difficult due to the thickness of the wire (requiring increased insulation thickness), which entails an increase in the overall dimensions, or the impossibility of manually achieving the required number of turns.

[0017] The distance between the primary and secondary windings of the planar transformer is maintained in the range of 0.076-0.2 mm. This gap is determined by the need to ensure maximum product reliability and is verified through calculations. Therefore, using a smaller gap (<0.076 mm) increases the risk of breakdown, as such a gap will not be able to ensure dielectric strength between the windings of the planar transformer. Furthermore, if the gap exceeds the maximum value (>0.2 mm), the transformer's inductance decreases, which entails a deterioration in its reliability (monitoring this parameter is important to ensure product compliance with technical requirements and its overall performance).

[0018] The absence of copper conductors on the outer layers of a multilayer printed circuit board (PCB) under the planar transformer core eliminates the risk of short circuits, as the transformer core material is a conductor. The protective solder mask used in multilayer PCBs is not an insulator, and using air as a dielectric is impractical due to its low thermal conductivity and electrical strength. The presence of a dielectric in this case is essential to ensure the functionality of the multilayer PCB. Cores or prepreg are used as such, thus concealing the copper conductors from the outer layer.

[0019] To prevent the risk of electrical breakdown in air and to ensure product operability, the conductors on the surface of the multilayer printed circuit board are provided with gaps and covered with an insulating film. Breakdown can occur through air, between conductors, between exposed contact pads, or between exposed pads and the housing. As an additional measure to ensure protection against breakdown, film can be applied to the transformer core and / or part of the housing. The combined use of a gap and a special insulating film (e.g., Kapton) is sufficient to ensure resistance to breakdown voltage in multilayer printed circuit boards.

[0020] Elements acting as insulators between galvanically unconnected conductors (capacitors) are designed to withstand the permissible voltage during breakdown voltage testing. Regardless of the nominal voltage passing through the insulation, the insulation is always selected based on the permissible breakdown voltage (with a margin). This prevents short circuits within the module at the input / output of the device in the event of an emergency.

[0021] All the features of the utility model are structurally inextricably linked within the framework of a single product, namely a DC / DC converter, which is a multilayer printed circuit board with a planar transformer and the functional elements of the converter.

[0022] The insulation characteristics of modules (DC / DC converters) using the proposed technical solution were tested using a UPU-10M universal breakdown tester and a GPT-79603 electrical safety testing system. Both systems can supply either AC (50 Hz) or DC voltage. Breakdown tests were performed at 1000-1500 V (depending on the application point) for 1 minute. Considering that each subsequent test cycle reduces the insulation lifespan, multiple tests showed that even with an insulation surge (5 kV), the module incorporating the proposed technical solution remains operational (using the example of a DC / DC module with an input / output voltage of 15 / 27 V).

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