JPH0642729B2 - Brightness control circuit - Google Patents
Brightness control circuitInfo
- Publication number
- JPH0642729B2 JPH0642729B2 JP62308069A JP30806987A JPH0642729B2 JP H0642729 B2 JPH0642729 B2 JP H0642729B2 JP 62308069 A JP62308069 A JP 62308069A JP 30806987 A JP30806987 A JP 30806987A JP H0642729 B2 JPH0642729 B2 JP H0642729B2
- Authority
- JP
- Japan
- Prior art keywords
- resistor
- beam current
- mode
- control circuit
- capacitor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Landscapes
- Television Receiver Circuits (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 この発明は、オーバースキヤンモードと、アンダースキ
ヤンモードとに切換可能な陰極線管装置の輝度制御回路
に関する。TECHNICAL FIELD The present invention relates to a brightness control circuit for a cathode ray tube device capable of switching between an overscan mode and an underscan mode.
第２図は従来の通常使用されているビーム電流制限回路
を備えた輝度制御回路のブロツク回路図であり、(1)は
水平偏向回路、(2)はフライバツクトランス、(2a)の２
次巻線、(3)は高圧整流ダイオード、(4)は陰極線管、
(5)は電源、(6)はコンデンサ、(10)はビーム電流検出用
の抵抗、(11)はビーム電流制限回路である。FIG. 2 is a block circuit diagram of a conventional brightness control circuit equipped with a commonly used beam current limiting circuit. (1) is a horizontal deflection circuit, (2) is a flyback transformer, and (2a) is 2
Next winding, (3) high voltage rectifier diode, (4) cathode ray tube,
(5) is a power source, (6) is a capacitor, (10) is a beam current detection resistor, and (11) is a beam current limiting circuit.
次に動作について説明する。水平出力回路(1)の動作に
より、フライバツクトランス(2)に発生したフライバツ
クパルスを、２次巻線(2a)に接続された高圧整流ダイオ
ード(3)により陰極線管(4)に直流高圧を供給している。
電源(5)は、水平出力回路(1)，ビーム電流制限回路(1
1)，および抵抗(10)に接続され、抵抗(13)の他端は、コ
ンデンサ(6)および２次巻線(2a)の一端に接続されてお
り、２次巻線(2a)に流れる電流、すなわちビーム電流i3
は電源(5)より抵抗(10)を通して流れる。これにより抵
抗(10)に電圧降下が生じ、コンデンサ(6)の両端には、
電流i3の大きさにより発生する電圧値が変化する。すな
わち、ビーム電流i3が零の時、抵抗(10)による電圧降下
は生じないため、コンデンサ(6)の両端の電圧は電源(5)
と同じ電圧が発生し、ビーム電流i3が流れると抵抗値×
ビーム電流値の電圧降下が生じ、コンデンサ(6)の両端
電圧が降下する。この降下ビーム電流制限回路(11)は、
コンデンサ(6)の端子電圧が一定値以下とならないよう
にビーム電流i3を制御する。Next, the operation will be described. Due to the operation of the horizontal output circuit (1), the flyback pulse generated in the flyback transformer (2) is supplied to the cathode ray tube (4) by the high voltage rectifier diode (3) connected to the secondary winding (2a). Is being supplied.
The power supply (5) consists of a horizontal output circuit (1) and a beam current limiting circuit (1
1) and the resistor (10), the other end of the resistor (13) is connected to the capacitor (6) and one end of the secondary winding (2a), and flows to the secondary winding (2a). Current, i.e. beam current i 3
Flows from the power supply (5) through the resistor (10). This causes a voltage drop across the resistor (10), across the capacitor (6),
The generated voltage value changes depending on the magnitude of the current i 3 . That is, when the beam current i 3 is zero, no voltage drop occurs due to the resistor (10), so the voltage across the capacitor (6) is equal to the power source (5).
When the beam current i 3 flows when the same voltage is generated, the resistance value ×
A voltage drop of the beam current value occurs, and the voltage across the capacitor (6) drops. This falling beam current limiting circuit (11)
The beam current i 3 is controlled so that the terminal voltage of the capacitor (6) does not fall below a certain value.
従来の輝度制御回路は以上のように構成されているの
で、陰極線管(4)の表示面に映出されるラスタの大きさ
を変えた場合でも、ビーム電流i3は同じである。このた
め、オーバースキヤンモードにしてラスタを表示面より
大きくした場合と、アンダースキヤンモードにしてラス
タを表示面より小さくした場合とでは、アンダースキヤ
ンモードにした場合のラスタの輝度が高くなる。したが
つて、いずれか一方のスキヤンモードで最適輝度に調整
していても、スキヤンモードを切り換えるたびに輝度を
再調整する必要があつた。Since the conventional brightness control circuit is configured as described above, the beam current i 3 is the same even when the size of the raster projected on the display surface of the cathode ray tube (4) is changed. Therefore, the brightness of the raster becomes higher in the underscan mode when the raster is made larger than the display surface in the overscan mode and when the raster is made smaller than the display surface in the underscan mode. Therefore, even if one of the scan mode is adjusted to the optimum brightness, it is necessary to readjust the brightness each time the scan mode is switched.
この発明は上記のような問題点を解消するためになされ
たもので、スキヤンモードを切り換えた場合でもラスタ
の輝度変化の少ない輝度制御回路を得ることを目的とす
る。The present invention has been made in order to solve the above problems, and an object thereof is to obtain a brightness control circuit in which the brightness change of the raster is small even when the scan mode is switched.
この発明に係る輝度制御回路は、フライバツクトランス
の２次巻線と電源との間に直列に接続されている第１の
抵抗と、この抵抗と上記電源に並列に接続されているコ
ンデンサと、上記第１の抵抗に並列に接続されているト
ランジスタと第２の抵抗との直列体を備え、オーバース
キヤン時には上記トランジスタをＯＮにし、アンダース
キヤン時にはＯＦＦにするように制御する点を特徴とす
る。A brightness control circuit according to the present invention includes a first resistor connected in series between a secondary winding of a flyback transformer and a power supply, and a capacitor connected in parallel to this resistance and the power supply. It is characterized in that a series body of a transistor and a second resistor connected in parallel to the first resistor is provided, and the transistor is controlled to be turned on at the time of overscan and turned off at the time of underscan.
この発明によるトランジスタは、オーバースキヤン時に
ＯＮとなつてビーム電流検出抵抗の値を小さくし、アン
ダースキヤンモード時にはＯＦＦになつて大きくする。
このため、コンデンサの端子電圧が一定となるようにビ
ーム電流をビーム電流制限回路によつて制御すると、ビ
ーム電流値はオーバースキヤンモード時よりアンダース
キヤンモード時の方が小さくなり、第１，第２の抵抗の
値を適当な値に選定することによりラスタの輝度が一定
となる。The transistor according to the present invention is turned on during overscan to reduce the value of the beam current detection resistance, and turned off during underscan mode to increase it.
Therefore, if the beam current is controlled by the beam current limiting circuit so that the terminal voltage of the capacitor becomes constant, the beam current value becomes smaller in the underscan mode than in the overscan mode. The brightness of the raster becomes constant by selecting an appropriate value for the resistance of.
以下この発明の一実施例を説明する。第１図において、
第２図と同一符号はそれぞれ同一、または相当部分を示
しており、(7)は抵抗、(8)はトランジスタ、(9)はベー
ス抵抗で、抵抗(7)とトランジスタ(8)とは直列に接続さ
れ、ビーム電流検出用の抵抗(10)と並列に接続されてい
る。(12)はスキヤンモード信号の入力端子で、オーバー
スキヤンモード時にはトランジスタ(8)をＯＮにし、ア
ンダースキヤンモード時にはＯＦＦにする二値信号が入
力される。An embodiment of the present invention will be described below. In FIG.
The same reference numerals as in FIG. 2 indicate the same or corresponding parts, respectively. (7) is a resistor, (8) is a transistor, (9) is a base resistor, and the resistor (7) and the transistor (8) are in series. And is connected in parallel with the beam current detection resistor (10). Reference numeral (12) is a scan mode signal input terminal. A binary signal for turning on the transistor (8) in the over scan mode and turning it off in the under scan mode is input.
以下この発明の動作を詳細に説明する。オーバースキヤ
ンモード時には、スキヤンモード信号はＨとなり、トラ
ンジスタ(8)はＯＮになつて抵抗(7)と抵抗(10)とは並列
に接続され、ビーム電流検出抵抗値は小さくなる。ま
た、アンダースキヤンモード時には、トランジスタ(8)
はＯＦＦになつて、ビーム電流検出抵抗値は大きくな
る。ビーム電流制限回路(11)はコンデンサ(6)の両端の
電圧が一定値以下とならないように制御しているので、
ビーム電流検出抵抗値が小さくなるとビーム電流最大値
が大きくなり、抵抗値が大きくなるとビーム電流最大値
は小さくなる。したがつて、抵抗(10)の値を、アンダー
スキヤンモード時に最適輝度となるように選定し、抵抗
(7)の値をオーバースキヤンモード時に同じ輝度となる
値に選定すれば、オーバースキヤンモード時と、アンダ
ースキヤンモード時のラスタの輝度は同一となる。The operation of the present invention will be described in detail below. In the over scan mode, the scan mode signal becomes H, the transistor (8) is turned on, the resistor (7) and the resistor (10) are connected in parallel, and the beam current detection resistance value becomes small. In the under scan mode, the transistor (8)
Becomes OFF, the beam current detection resistance value increases. The beam current limiting circuit (11) controls the voltage across the capacitor (6) so that it does not drop below a certain value.
The beam current maximum value increases as the beam current detection resistance value decreases, and the beam current maximum value decreases as the resistance value increases. Therefore, the value of the resistor (10) is selected so as to obtain the optimum brightness in the underscan mode, and
If the value of (7) is selected to have the same luminance in the overscan mode, the luminance of the raster in the overscan mode and the raster in the underscan mode are the same.
以上のように、この発明によれば、ビーム電流検出抵抗
の値をオーバースキヤンモード時とアンダースキヤンモ
ード時とで切り換えるように構成したので同一映像受像
時に、オーバースキヤンモードとアンダースキヤンモー
ドに切り換えてもラスタの輝度は変わらないので、スキ
ヤンモード切換時の輝度再調整が不要となる効果が得ら
れる。As described above, according to the present invention, since the value of the beam current detection resistance is switched between the overscan mode and the underscan mode, the overscan mode and the underscan mode can be switched when the same image is received. However, since the brightness of the raster does not change, it is possible to obtain the effect that the readjustment of the brightness when switching the scan mode becomes unnecessary.
第１図はこの発明の一実施例の回路図、第２図は従来の
輝度制御回路を示す図である。 (2a)…フライバツクトランス２次巻線、(4)…陰極線
管、(5)…電源、(6)…コンデンサ、(7),(9),(10)…抵
抗、(8)…トランジスタ、(11)…ビーム電流制限回路、
(12)…スキヤンモード信号入力端子。 なお、各図中、同一符号は同一、または相当部分を示
す。FIG. 1 is a circuit diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing a conventional brightness control circuit. (2a) ... Flyback transformer secondary winding, (4) ... Cathode ray tube, (5) ... Power supply, (6) ... Capacitor, (7), (9), (10) ... Resistor, (8) ... Transistor , (11) ... Beam current limiting circuit,
(12)… Skiyan mode signal input terminal. In each figure, the same reference numerals indicate the same or corresponding parts.
Claims (1)
の間に直列に挿入されている第１の抵抗と、この抵抗お
よび上記電源と並列に接続されているコンデンサと、上
記第１の抵抗と並列に接続されているトランジスタと第
２の抵抗の直列体と、上記コンデンサの端子電圧が一定
値となるように上記フライバツクトランスの２次巻線を
流れるビーム電流を制御するビーム電流制限回路と、上
記トランジスタをオーバースキヤン時にはＯＮとし、か
つ、アンダースキヤン時にはＯＦＦとする制御手段とを
備えた輝度制御回路。1. A first resistor inserted in series between a secondary winding of a flyback transformer and a power source, a capacitor connected in parallel with the resistor and the power source, and the first resistor. Beam current limit for controlling the beam current flowing through the secondary winding of the flyback transformer so that the terminal voltage of the capacitor and the series connection of the transistor and the second resistor connected in parallel with the resistor have a constant value. A brightness control circuit comprising a circuit and a control means for turning on the transistor during overscan and turning off during underscan.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62308069A JPH0642729B2 (en) | 1987-12-03 | 1987-12-03 | Brightness control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62308069A JPH0642729B2 (en) | 1987-12-03 | 1987-12-03 | Brightness control circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH01147974A JPH01147974A (en) | 1989-06-09 |
| JPH0642729B2 true JPH0642729B2 (en) | 1994-06-01 |
Family
ID=17976506
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62308069A Expired - Lifetime JPH0642729B2 (en) | 1987-12-03 | 1987-12-03 | Brightness control circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0642729B2 (en) |
-
1987
- 1987-12-03 JP JP62308069A patent/JPH0642729B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH01147974A (en) | 1989-06-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term | ||
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20080601 Year of fee payment: 14 |