Matsushita Electric Industrial Co., Ltd.

Matsushita Electronics Corporation

Yukio Uchida

Tomoaki Iwamoto

Katsuyo Iwasaki

Mitsuya Masuda

Tomohiro Sakata

Two closed-loop coils are respectively set at the top or the bottom of a cathode ray tube. These two closed-loop coils serves in a pair as a cancel coil. Each closed-loop coil is positioned so as to make an interlinkage with the magnetic field leakage that escapes from the deflection yoke, a part of the closed-loop coil running almost in parallel to the top or bottom edge of an effective display region of a front panel.

Cathode ray tube device that reduces magnetic field leakage

A vertical linearity correction circuit including diodes and resistors is provided in a vertical deflection circuit, and a vertical deflection voltage applied to a vertical deflection yoke is corrected so as to follow a change in input impedance of the vertical deflection yoke. As a result, the vertical deflection speed in the vicinity of the central part of the image plane of the color picture tube is prevented from decreasing.

Vertical deflection circuit

A vertical deflection circuit for a color picture tube apparatus, which reduces a white horizontal belt-like area that appears near vertical center of a color picture tube screen, caused by the operation of a convergence correction circuit using switching characteristics of a diode. The circuit comprises a vertical deflection yoke and a vertical linearity correction circuit connected to the vertical deflection yoke. The vertical deflection yoke has a vertical deflection coil, a convergence correction circuit using a diode as a switch, and a vertical coma aberration correction coil. An impedance of the vertical linearity correction circuit varies within a range where a vertical deflection current is in the vicinity of 0 A so as to reduce an impedance of the vertical deflection circuit.

Vertical deflection circuit and color picture tube apparatus

A dynamic focus circuit enables ideal focusing characteristics to be obtained across the entire screen of a wide-angled cathode ray tube, by generating a dynamic focus voltage having a flat-bottomed waveform through the addition of a simple circuit to a conventional analog circuit. If an S-shaping voltage method is used, the voltage of a signal induced in a secondary coil of a step-up transformer for raising the voltage of a parabolic waveform signal having a horizontal deflection period switches the gain for converting the parabolic waveform signal to a dynamic focus voltage, according to whether the induced voltage exceeds a specified reference value. If the induced voltage does not exceed the specified reference value, the parabolic waveform signal is converted to the dynamic focus voltage at a gain of less than one. If a DAF (Dynamic Focus) signal generating IC is used, a gain control voltage for controlling a gain of the parabolic waveform signal generated by the DAF signal generating IC is altered so that the gain is smaller than one at the approximate midpoint of a horizontal deflection period, and increases as it moves out to the edges of the screen.

Dynamic focus circuit suitable for use in a wide-angled cathode ray tube

A display unit that enables reduction in number of additional parts, decrease in leakage magnetic field in a VLF band generated from the display unit in all directions at low cost, and suppression of the leakage magnetic field to the specified value or less according to MPR-II Standard with tolerance is provided. The display unit comprises a cathode-ray tube having a neck portion, a deflection yoke 2 that is mounted at a predetermined position on a periphery of the neck portion, and a driving circuit 3 that has a coil 4 and drives the deflection yoke 2. The driving circuit 3 (the coil 4) is provided at such a position and in such a direction that a magnetic field E.sub.2 generated from the driving circuit 3 (the coil 4) cancels out a leakage magnetic field generated E.sub.1 from the deflection yoke 2 substantially at the position in front of and 50 cm away from the center of a face panel of the cathode-ray tube.

Growing community of inventors

Ibaraki, Japan

Yukio Uchida