Hitachi, Ltd.

Tsuneo Fujikura

Takeo Yamada

Masanori Ogino

Miyuki Ikeda

Takahiko Fujiwara

Toshiyuki Kimoto

Yoshihiro Arakawa

Etsuhiro Nakagiri

Yuji Shinagawa

A cathode ray tube display in which a signal for detection of a cathode current is inserted into a part of the vertical blanking period of the video signal to be displayed, a cathode current corresponding to the signal for detection is detected, and a cathode voltage or a grid voltage is negative feedback controlled so that the detected cathode current becomes constant, thereby stabilizing the cathode current. The display has a local overscan circuit for executing a vertical scan on the screen with a width larger than a predetermined scan width only at a timing of the cathode current detecting signal inserted for a vertical blanking period, and even in the case where an underscan system to scan by a width smaller than a predetermined display screen width is used as a scan system of the screen display. The invention prevents a harmful visible display image by the cathode current detecting signal appears on the screen.

Cathode ray tube display

A video output circuit of a wide bandwidth comprises a bridged-T-type circuit, a first inductor connected in series to the bridged-T-type circuit, and a shunt circuit connected in series to the bridged-T-type circuit and including a second inductor and a first resistor connected in parallel with each other. The bridged-T-type circuit, the first inductor and the shunt circuit cooperate to constitute together with a plurality of stray capacitors a low-pass filter whose order is at least 4 and whose merit index is at least 3.

Video output circuit with wide bandwidth and low power consumption for

In a grid drive-type CRT display apparatus, the impedance of a second grid voltage supply circuit is made a high impedance and a low-frequency band rejecting streaking interference caused by the high impedance is compensated by low-frequency range emphasizing circuit means. The low-frequency range emphasizing circuit means compensates for the low-frequency range rejection characteristic which is an adverse effect of the high impedance to the second grid and this results in an improvement in the high-frequency transmission characteristic. Also, there is the effect of improving the frequency bandwidth and reducing the consumption of power.

Grid-drive type display apparatus

A convergence correction circuit according to the present invention has a phased locked loop including a programmable counter. The programmable counter has programmable count start and end points. The output of the programmable counter is supplied to a memory storing convergence distortion correcting data therein. As the horizontal screen size is increased, a value closer to the lower limit 0 of the start point as compared with that taken when the horizontal size is small is set as the count start point of the programmable counter, and a value closer to the upper limit (2.sup.7 -1) of the end point as compared with that taken when the horizontal size is small is set as the count end point. In accordance with the horizontal screen size, the count start and end points of the programmable counter are changed. Correct convergence correction is performed even if the horizontal screen size is changed.

Growing community of inventors

Yokohama, Japan

Tsuneo Fujikura