U.S. Philips Corporation

Koninklijke Philips Corporation N.v.

Eelco G Visser

Mark Thomas Johnson

Holger Joachim Moench

Carsten Deppe

Xaver Riederer

Johannes P Damen

Johannes H Tobben

Arjan Noordermeer

Piet F Bongers

Doeko Stoppels

Paul N Faase

Nicolaas Hubertina Gerardus Reijnders

Stephanus A Mulder

Martinus J M De Graaf

Marijke M Severin

Martinus Jm De Graaf

The invention relates to a method of representing a video image based on a video signal by means of a projector which comprises an image display device and a high-pressure gas discharge lamp, which lamp is supplied with a square-wave alternating current (I, I) on which a current pulse (P, P, P, P) is superimposed before each phase reversal. According to the invention, the alternating current (I, I) is superimposed with a second current pulse (P, P, P, P, P, P) of the same polarity. A simple attunement of the alternating current frequency to the image frequency without image artifacts is made possible by the second pulses (P, P, P, P, P, P).

Method of representing a video image by means of a projector

A description is given of a method of manufacturing an inductive element for SMD applications. This method comprises the following steps: a) providing a number of predominantly parallel electroconductive wires in the mould of an injection-molding device, b) circumferentially providing a part of the wires with a synthetic resin by injection molding, in such a manner that the ends of the wires remain free, c) providing an envelope of a soft-magnetic material around the circumferentially injection molded part of the wires, and d) reshaping the ends of the wires. In accordance with the invention, the method is characterized in that the parts of the wires to be circumferentially injection molded are fixed inside the mold during the injection molding process. It has been found that inductive elements of the type manufactured in accordance with the inventive method generate, in operation, optimally homogeneous magnetic fields. Also the risk of electric short-circuits proves to be small.

Inductive element

A method of manufacturing an inductive element for SMD applications comprises the following steps: a) providing a number of predominantly parallel electroconductive wires in the mould of an injection-moulding device, b) circumferentially providing a part of the wires with a synthetic resin by injection moulding, in such a manner that the ends of the wires remain free, c) providing an envelope of a soft-magnetic material around the circumferentially injection moulded part of the wires, and d) reshaping the ends of the wires. The parts of the wires to be circumferentially injection moulded are fixed inside the mould during the injection moulding process. The element generates optimally homogeneous magnetic fields. Also the risk of electric short-circuits is small.

An inductive device comprises a soft magnetic core which consists of two E-shaped core halves (1), each of which comprises three parallel limbs (5, 7) which are interconnected by a yoke (9). The core halves (1) are arranged against one another by way of the free ends of the limbs (5, 7), a coil former (3) being provided around the central limbs (7). The outer limbs (5) extend between an upper boundary plane (25) and lower boundary plane (27), which planes extend parallel to the longitudinal directions of the limbs (5, 7) and the yokes (9), the distance between said planes being determined by the height (x) of the outer limbs (5) which is greater than the height (y) of the central limbs (7). The lower boundary of the central limb (7) is situated above or below the boundary plane (27) a distance such that the symmetry plane (31) of the central limbs (7) which extends parallel to the boundary planes (25, 27), is situated halfway between the upper boundary plane (25) and a plane (33) which extends parallel to the boundary planes and is from 0.1 to 1 mm above the lower boundary of the coil former (3). A winding (29) provided on the coil former (3) occupies exactly the space between the upper side of the outer limits (5) and the lower side, thus minimizing the height of the device. Such device may be, for example, a transformer or a choke coil.

Inductive device

The invention relates to a sintered transformer core of MnZn-ferrite material, the initial permeability of which ranges between 10 and 1000. Said transformer cores preferably have an average particle size which ranges between 0.05 and 2.0 .mu.m. The transformer cores according to the invention exhibit surprisingly low overall losses when operating in the frequency range of 2 MHz and higher. Such transformer cores can be very advantageously used in transformers operated in said frequency range, such as SMPS transformers.

Sintered transformer core of MnZn-ferrite and a transformer comprising

A magnetic head (1) having a (monocrystalline) core (2) of a magnetizable material which provides a substantially closed path for magnetic flux (B) in write/read operations of the magnetic head (1). In order to provide a magnetic head which has an improved signal-to-noise ratio in particular in the frequency range from 0.5-10 MHz, the magnetizable material of the core (2) shows essentially a uniaxial magnetic anisotropy having an easy axis of magnetization which is transverse to the plane of the path for the magnetic flux. Said orientation of the easy axis of magnetization is produced in one embodiment by coating the faces of the core which are parallel to the path for the magnetic flux with layers of non-magnetizable material which exert a (tensile or compressive) stress in said planes.

Magnetic head

Magnetic head for a magnetic recording and playback apparatus includes a core of a Mn--Zn-ferrous ferrite having a very high saturation magnetization. The Mn--Zn-ferrous ferrite has a composition (not counting optional substitutions) according to the formula

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Eindhoven, Netherlands

Eelco G Visser