Inductor devices – Coil and core
Reexamination Certificate
1997-11-04
2001-06-26
Gellner, Michael L. (Department: 2832)
Inductor devices
Coil and core
C336S206000, C336S083000
Reexamination Certificate
active
06252487
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to planar magnetic components, and more particularly relates to such components which include a core and a planar winding structure, such as planar inductors and transformers.
Planar magnetic components, particularly those characterized by relatively high leakage flux, such as inductors and some transformers designed to have built-in inductance, are useful in power electronics applications in which space is limited, for example, electronic lamp ballasts and switched-mode power supplies.
Conventional planar magnetic components have winding structures which consist of a stack of layers each containing part of the total winding structure, insulating layers usually consisting of a flexible, non-conducting, low permittivity, high temperature resistant polymer to prevent electrical contact between the turns in adjacent layers, and a contacting structure that permits electrical contact between turns in adjacent layers where needed. The winding structures are usually made by etching or stamping or sometimes by folding. Contacts are usually made by soldering or via plating.
An improved planar magnetic component with planar winding structure which is compact, in which the winding layers are readily interconnected, and which can be readily connected to external circuitry, is described and claimed in co-pending U.S. patent application Ser. No. 08/874,171 (Attorney docket number PHA 23,256) filed Jun. 13, 1997, and assigned to the present assignee. The density of the planar winding structure results in a relatively low thermal resistance, compensating somewhat for the lower surface area available for heat transfer.
Winding losses occur in all such magnetic components. In general, winding losses are due to the interaction of the winding current with a local magnetic field, due largely to leakage flux from the windings and to stray fields near the gaps in the core. The leakage flux, defined as the magnetic flux not present in either the core or the gaps, is relatively high in inductors as well as in some transformers, which are designed to have built-in inductance, such as those sometimes used in switched mode power supplies and lamp ballasts.
In such high-leakage flux applications, there is a need to reduce the winding losses, while at the same time preserving or even enhancing the advantages of the known planar magnetic components.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide a high-leakage-flux planar magnetic component with reduced winding losses in the winding structure.
It is another object of the invention to provide such a magnetic component which is compact.
It is another object of the invention to provide such a magnetic component in which the winding layers are readily interconnected.
It is another object of the invention to provide such a planar magnetic component which can be readily connected to external circuitry.
In accordance with the invention, a high-leakage-flux magnetic component, comprising a core and a planar winding structure, is characterized in that the winding structure comprises inner and outer planar windings oriented substantially transverse to the plane of winding structure, the inner winding being wholly inside and concentric to the outer winding.
As used herein, the term “winding window” is meant to refer to the opening in the core which accommodates the winding structure, as seen in a cross section of the core taken transverse to the plane of the winding structure.
In such a winding structure in which the core has one or more gaps which are generally coplanar with the plane of the winding, for example, the core is divided into core components having facing planar surfaces separated from one another, the plane of the winding turns substantially coincides with the path of the leakage flux across the winding window. Eddy current losses are thereby minimized, resulting in considerably lower winding losses.
Moreover, with such a transverse orientation of the windings, it is possible to form the winding structure by winding a flat conductor into a coil, enabling a very compact structure having a high density and mechanical rigidity.
Such a structure has several advantages over the stacked structures of the prior art. For example, the high density of such a structure enables a high fill factor of the conductor, which also contributes to lower winding losses. The high density also reduces the thermal resistivity of the winding. In addition, such structures can be pinned or soldered directly to a circuit board, thereby reducing the thermal resistivity between the structure and the board.
In addition, such a structure may be fabricated using conventional wire winding techniques, with no interconnections between layers being required. With such advantages, even smaller core sizes are possible.
Accordingly, a preferred embodiment of the invention comprises such a planar magnetic component in which the winding structure comprises such a wound flat conductor.
In accordance with another embodiment of the invention, the thickness of the conductive turns of the winding is no more than three times, and preferably no more than two times, the current skin depth at the operating frequency of the device. For copper, the skin depth at room temperature (in cm) is given by
Δ
=
6.57
1
/
f
where f is the operating frequency in Hz. Typical operating frequencies of 50 kHz, 250 kHz and 1 MHZ correspond to skin depths of about 0.29 mm, 0.13 mm and 0.065 mm, respectively.
REFERENCES:
patent: 2064771 (1936-12-01), Vogt
patent: 3210705 (1965-10-01), Lockie
patent: 3223923 (1965-12-01), Howell
patent: 3609613 (1971-09-01), Horn et al.
patent: 3662461 (1972-05-01), Lake et al.
patent: 4021764 (1977-05-01), Winn
patent: 4135173 (1979-01-01), Philp
patent: 4400226 (1983-08-01), Horrigan
patent: 4507640 (1985-03-01), Rich, III et al.
patent: 4516104 (1985-05-01), McDermott
patent: 4583068 (1986-04-01), Dickens et al.
patent: 4630013 (1986-12-01), Takada
patent: 4675638 (1987-06-01), Szabo
patent: 5296830 (1994-03-01), Tamada et al.
patent: 5710745 (1998-01-01), Getreuer
patent: 5726615 (1998-03-01), Bloom
patent: 5767760 (1998-06-01), Mollie et al.
patent: 24 09 881 (1975-09-01), None
patent: 572857 (1975-07-01), None
Azevedo Jose
Wolf Ronald M.
Faller F. Bruce
Gellner Michael L.
Mai Anh
Philips Electronics North America Corporation
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