Matsushita Electric Industrial Co., Ltd.

Hiroki Kinugawa

Hiroshi Ando

Masahiko Sasada

Yoshinori Ishikawa

Hitoshi Adachi

Nobuo Taketani

Minoru Miyata

Hiroyasu Shimaoka

Tsuneo Matsukura

Yoichi Kanegami

An output circuit includes: a power supply unit; an output MIS transistor connected to the power supply unit; a reference MIS transistor that is connected to the power supply unit and is invariably in ON state; a current supply unit for generating a reference voltage Vref; an output terminal through which a current is supplied to a load circuit; a comparator; a logic circuit; and a control circuit for carrying out the ON/OFF control of the output MIS transistor. Comparison is made between the reference voltage Vref and output terminal voltage Vout by utilizing the ON-state resistances of the output and reference MIS transistors, thus detecting the magnitude of an output current. If the output current exceeds the target value, the output MIS transistor is turned OFF, thereby protecting it from an excessive current.

Output circuit

A primary color video output circuit for limiting an input video signal. The circuit includes a clipping circuit, a reference voltage generating circuit and an amplifier. The clipping circuit limits the level of the input video signal based on a reference voltage generated by the reference voltage generating circuit. The amplifier is then used to amplify the clipped video signal.

Primary color video signal output circuit

The object of the present invention is to easily compensate automatic brightness limiting performance and automatic contrast limiting performance even if a picture is displayed with a different aspect ratio and to prevent deterioration of picture quality such as gradation and sharpness. A picture display apparatus includes (1) an automatic brightness limiter (ABL) circuit including a comparison circuit for varying an EHT compensation starting point, an ABL gain control circuit for varying a slope of the EHT characteristic versus the APL, an ABL comparison voltage generator, a DAC for adjusting an ABL compensation starting point and a DAC for adjusting an ABL gain and (2) an automatic contrast limiter (ACL) circuit including another comparison circuit for varying an EHT compensation starting point, an ACL gain control circuit for varying a slope of the EHT characteristic versus the APL, an ACL comparison voltage generator, a DAC for adjusting an ACL compensation starting point and a DAC for adjusting an ACL gain.

Automatic brightness limiter automatic control circuit, contrast limiter

Control circuits for the cut-off and drive control of video equipment. A first control device includes a cut-off control circuit and drive control circuit for use in conventional modes. A second control device includes a cut-off control circuit for mode switching and a drive control circuit for mode switching, independent of the first control device. The cut-off and drive adjustments made for every mode switching operation are unnecessary, and the mode switching based on off set data is possible.

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Kusatsu, Japan

Hiroki Kinugawa