Inductor devices – Coil or coil turn supports or spacers – Printed circuit-type coil
Reexamination Certificate
1999-05-21
2001-04-03
Mai, Anh (Department: 2832)
Inductor devices
Coil or coil turn supports or spacers
Printed circuit-type coil
C336S223000, C336S232000, C336S061000
Reexamination Certificate
active
06211767
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the power transformer and more particularly to planar transformers field and power transformer structures, which involves the power transformer and different magnetic elements.
2. Description of the Related Art
In order to comply with the height requirements for power transformers the conventional barrel transformer have been replaced by planar structures. The planar structures consists in staking up layers composed by dielectric sheet and copper spirals interconnected through pins penetrating through holes in the dielectric sheets. In application wherein compliance with safety agencies is required which demands that a high voltage level has to be sustain in between primary winding and secondary winding a bobbin
37
a
and
37
b
may be employed as depicted in FIG.
3
. In between he the dialectic layers such as
31
a
, there are spiral of copper material interconnected through interconnection holes such as 150, and interconnection pins. This method is labor intensive, requires a special bobbin and interconnection pins which are mechanical unreliable.
Another methodology is locating the winding within a multilayers PCB. Each layer of the multilayer PCB contains one or more spiral turns, which are interconnected using, metalized via. This method of construction is simple and reliable. It does not address the high power requirements. In order to process high current the copper thickness has to be high or the number of layers have to increased. Both solutions are very costly. The concept presented in this invention is combining the multilayer PCB construction for one of the transformer winding which process low current, with copper strips attached to the multilayer PCB using metalized holes for positioning and interconnection. The metalized via for positioning allow the use of soldering attachment. The multilayer PCB wherein the low current winding implemented offers the mechanical support for the secondary copper strips and the required insulation between the primary and secondary. Power connector may be further attached to the multilayer PCB for a better interface to the rest of the circuit. Another advantage of this technology is the fact that additional inductive elements can be implemented on the same multilayer PCB. Another advantage is the fact that multiple magnetic cores can be used on the same multilayer structure wherein the primary winding is embedded. These multiple transformer elements can have the primary in series or in parallel to ensure a uniform utilization of all the magnetic cores. Additional pads can be placed on the multilayer PCB to accommodate surface mounted components. Some of the layers of the multilayer PCB can be utilized for different function such as shielding or noise cancellation. In some of the embodiments of the invention the secondary winding can be also implemented in multilayer PCB technology. In this way we can have multiple turns for the secondary.
SUMMARY OF THE INVENTION
The main object of this invention is to provide a very versatile, modular, easy to manufacture, compact, low cost transformer, for all levels of power—low, medium, and high—applications
The present invention is a special transformer, which can be used in multiple applications, ranging from low power to high power supplies, converts etc. It features a low cost, modularity and versatility, easy manufacturing, small size, high performance and reliability. Its primary is built into the inner layers of a PCB, and may have multiple configurations, according to different number of turns, for different voltage and current ratios. The “inside the PCB” configuration, offers superior separation and insulation, thus the small dimensions and the increased reliability of the device. The turns on each layer make contact with the ones on the next layer, using vias. According to the desired voltage ratio, the user may use the appropriate PCB/primary package, with the number of turns required by the specific application. The primary may be contacted with simple cooper pads on the top and bottom side of the PCB, or with separate, special connectors. The PCB also has a central rectangular slot to accommodate the middle part of the magnetic core and holes for attachment pins, vias, and connectors. The insulation between the primary winding and the core and the secondary winding can be made in several ways. One way is to locate all the primary winding inside of the multilayers PCB and the interconnection vias located to the required distance from the core and the secondary winding, in order to comply with the safety agency. The thickness of the dielectric between magnetic core and the primary winding has to be chosen also for compliance with the safety agencies. Another method is to bury the primary winding and the interconnection via in between two layers of dielectric. The thickness of the dielectric is chosen for compliance with the safety agency.
The secondary is a separate set of copper strips, also configurable according to the application. It may have different widths, thickness, and number of turns. The user will pick the one, which is appropriate for his needs. The secondary strip is attached to the PCB using bent pins, which have either only a mechanical, or mechano-electrical function, and which insure a precise positioning guaranteeing the safe distance to the primary and primary vias. Each turn has two lateral pins on one end, and four pins, two and two in offset positions, on the other end, in the middle of the side of the PCB. Also close to the middle of the strip, there is an additional pin, in a sideways position, to mechanically keep that part of the strip fastened to the PCB. The middle pins will keep the secondary strip attached to the PCB, and at the same time will transport the current to the strip on the other side of the PCB, that is, to the other half of the secondary. The secondary loop on the other side is an identical copper trip, just flipped 180 degrees, and inserted in the free PCB holes. This design has the advantage of cutting costs of manufacturing two different strips. This strip will use the correspondent respective pins receive the current and will transport it to the other end, thus, creating a 2,4 or more turns secondary. For more than two turn, for example four, the secondary uses an insulator sheet between the first two turns, then the PCB acts as an insulator between the second and the third, then another insulator sheet between the third and the fourth turn. The connection of the first turn strip to the second turn strip is made with special bent fins and holder slots; also soldering will be applied to the fins area, to mechanically and electrically strengthen the area. The connection between the second and the third turn is done as for the two turns secondary, that is by the pad area and pins. the connection between the third and the fourth strip is again done by bent-over pins. A small notch in the second turn strip will permit the middle attachment pin to run into the PCB without shortening the first two turns. The same for the notch in the third-turn strip and the attachment pin of the fourth turn. The strips on the two sides of the PCB are symmetrical, each of them may be mounted on either side. They may have one or more turns. they may use separate connectors, or just holes for connection purposes. The magnetics may be the E+I type, or just the E+E type, and will use a rectangular slot in the PCB for mounting.
Another embodiment of the present invention uses a thin, double-sided PCB's for each two turns of the secondary. Each secondary PCB, has a copper turn on each side, holes to receive the connector ends, and vias to communicate the current from one turn to the other. The same symmetry exists between the secondary PCB on both sides of the main/primary PCB.
For applications where an additional resonant inductor or soft switching inductor is reguired in series or in parallel with the primary, the additional inductor element can be also constr
Mai Anh
Rompower Inc.
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