JPH0486113A - Agc circuit - Google Patents
Agc circuitInfo
- Publication number
- JPH0486113A JPH0486113A JP20201890A JP20201890A JPH0486113A JP H0486113 A JPH0486113 A JP H0486113A JP 20201890 A JP20201890 A JP 20201890A JP 20201890 A JP20201890 A JP 20201890A JP H0486113 A JPH0486113 A JP H0486113A
- Authority
- JP
- Japan
- Prior art keywords
- gain amplifier
- variable gain
- variable
- level
- circuit
- 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.)
- Granted
Links
- 230000007423 decrease Effects 0.000 claims abstract description 7
- 238000001514 detection method Methods 0.000 claims description 15
- 230000003247 decreasing effect Effects 0.000 abstract description 7
- 238000010586 diagram Methods 0.000 description 8
- 230000005236 sound signal Effects 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 2
Landscapes
- Control Of Amplification And Gain Control (AREA)
Abstract
Description
【発明の詳細な説明】
（イ）産業上の利用分野
本発明は、音声信号のレベル調整やテレビジョン受像機
のコントラスト調整など利用者が調整可能な可変利得増
幅器を備えたＡＧＣ回路に関するものである。DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an AGC circuit equipped with a variable gain amplifier that can be adjusted by the user, such as adjusting the level of an audio signal or adjusting the contrast of a television receiver. be.
（ロ）従来の技術
スピーカから放音諮れる音声信号やテレビジョン受ｌｌ
機の画像のコントラストなど聴取者や視聴者の好みに
応じて信号のレベル調整を行ないたいものがある。その
ようなものは、一般に利用者によって利得が変化させら
れる可変利得増幅器によって構成され、過大出力を防止
する為のＡＧＣ（自動利得制御）ループを備えている。(b) Audio signals and television reception that can be emitted from conventional technology speakers
There are times when it is desired to adjust the signal level according to the listener's or viewer's preferences, such as the contrast of the image of the device. Such devices generally consist of variable gain amplifiers whose gain can be varied by the user, and are equipped with an AGC (automatic gain control) loop to prevent excessive output.
第２図は、その様なＡＧＣ回路を示すもので、可変利得
増幅器（１）と、該可変利得増幅器（１）の利得を使用
者の好みによって変化させる為の制御電圧を発生する可
変抵抗（２）と、前記可変利得増幅器（１）の出力信号
のレベル検波を行なうレベル検波回路（３）と、該レベ
ル検波回路（３）の検波出力信号と基準電源（４）の基
準電圧との比較を行なう比較器（５）とから構成される
装置
第２図において、入力端子（６）には音声信号や映像信
号などの入力信号が加わり、可変利得増幅器（１）で増
幅されて出力端子（７）に得られる。可変抵抗（２）が
変化させられると、可変利得増幅器（１）の利得が変化
するので、入出力信号の関係は、第３＠Ｊの如く変化す
る。可変利得増幅器（１）の出力信号は、レベル検波回
路（３）で検波きれて比較器（５）に印加跡れるが、比
較器（５〉の基準電Ｒ（４）の値は、比較的高い値（Ｖ
、）に設定されている。その為、前記出力信号のレベル
が第３図の如くｖ。Figure 2 shows such an AGC circuit, which includes a variable gain amplifier (1) and a variable resistor (1) that generates a control voltage to change the gain of the variable gain amplifier (1) according to the user's preference. 2), a level detection circuit (3) that performs level detection of the output signal of the variable gain amplifier (1), and a comparison between the detected output signal of the level detection circuit (3) and the reference voltage of the reference power supply (4). In FIG. 2, an input signal such as an audio signal or a video signal is applied to the input terminal (6), amplified by the variable gain amplifier (1), and output to the output terminal ( 7). When the variable resistor (2) is changed, the gain of the variable gain amplifier (1) changes, so the relationship between input and output signals changes as shown in the third @J. The output signal of the variable gain amplifier (1) is detected by the level detection circuit (3) and applied to the comparator (5), but the value of the reference voltage R (4) of the comparator (5>) is relatively small. High value (V
, ) is set. Therefore, the level of the output signal becomes v as shown in FIG.
以下の場合には、比較器（５）は可変利得増幅器（１）
に対して何ら制御を行なわない。そして、前記出力信号
のレベルが■。以上となると、比較器（５）は可変利得
増幅器（１）の利得を前記出力信号のレベルに応じて低
下させるので、出力信号のレベルは、第３図の如く一定
値（Ｖ、）にリミットきれる。In the following cases, the comparator (5) is a variable gain amplifier (1)
There is no control over the Then, the level of the output signal is ■. In this case, the comparator (5) reduces the gain of the variable gain amplifier (1) according to the level of the output signal, so the level of the output signal is limited to a constant value (V, ) as shown in Figure 3. I can do it.
従って、第２図の回路によれば、利用者の好みに応じて
信号のレベル調整を行なえるとともに、過大な出力の発
生を自動的に防止することが出来る。Therefore, according to the circuit shown in FIG. 2, it is possible to adjust the signal level according to the user's preference, and it is also possible to automatically prevent the generation of excessive output.
（ハ）発明が解決しようとする課題
しかしながら、第２図の回路では、可変抵抗（２）に基
づき発生する制御電圧と基準電源（４）の電圧とが互い
に無関係に設定されている為、次のような問題が生じる
。商業放送では番組とコマーシャルとで音声信号の変調
度が全体的に異なることがあり、コマーシャルの間に音
声信号のレベルが大きくなる場合がある。そのような状
況で、放送を静かな音量で聞くとする。静かな音量とは
、第２図の可変利得増幅器（１）の利得を下げた場合の
ことで、例えば第３図のＡの状態とする。今、第３図の
入力信号Ｖ、のレベルで番組を聴取していたとする。そ
して、コマーシャルの時間となり、入力信号のレベルが
増加したとすると、その入力信号は、リニアに増幅され
て出力きれてしまい、■、のレベルになるまで全く制限
されず、そのまま出力きれてしまう。この場合の両者の
音量の違いは、相対的に激しいものとなり、聴取者に対
して不快となる。ここで、聴取者がコマーシャルの音が
大きいとして、第２図の可変抵抗（２〉を調整して可変
利得増幅器（１）の利得を第３図のＢの如く低下許せた
とする。すると、確かにコマーシャルの音量は、低下さ
せられるが、今度は本来の番組に戻ると、番組の音量も
低下してしまい、極端な場合には聞えないレベルになっ
てしまう、という問題がある。(c) Problems to be Solved by the Invention However, in the circuit shown in FIG. 2, the control voltage generated based on the variable resistor (2) and the voltage of the reference power supply (4) are set independently of each other, so The following problems arise. In commercial broadcasting, the degree of modulation of the audio signal may differ overall between programs and commercials, and the level of the audio signal may increase during commercials. In such a situation, suppose you listen to a broadcast at a quiet volume. Quiet sound volume refers to the case where the gain of the variable gain amplifier (1) in FIG. 2 is lowered, for example, the state shown in A in FIG. 3. Assume that you are currently listening to a program at the level of the input signal V shown in FIG. Then, when it comes time for a commercial and the level of the input signal increases, the input signal is linearly amplified and cannot be outputted, and is not restricted at all until it reaches the level (3), and is outputted as is. In this case, the difference in volume between the two is relatively large, making the listener uncomfortable. Now, suppose that the listener is able to adjust the variable resistor (2> in Figure 2 and allow the gain of the variable gain amplifier (1) to drop as shown in B in Figure 3) because the commercial sound is loud. The volume of commercials is lowered, but when the program returns to the original program, the volume of the program also decreases, and in extreme cases, the problem is that it becomes inaudible.
（ニ）課題を解決するための手段
本発明は、上述の点に鑑み成されたもので、入力信号を
増幅する可変利得増幅器と、該可変利得増幅器の利得を
変化きせるための制御手段と、前記可変利得増幅器の出
力信号のレベル検波を行なうレベル検波回路と、該レベ
ル検波回路の検波出力信号と基準電源の基準電圧とを比
較し、その比較出力に応じて前記可変利得増幅器の利得
を制御する比較器と、前記制御手段の出力信号に応じて
前記比較器の基準電源の値を変化させるレベル調整回路
と、から成ることを特徴とする。(d) Means for Solving the Problems The present invention has been made in view of the above points, and includes a variable gain amplifier for amplifying an input signal, a control means for changing the gain of the variable gain amplifier, a level detection circuit that performs level detection of the output signal of the variable gain amplifier; and a level detection circuit that compares the detection output signal of the level detection circuit with a reference voltage of a reference power supply, and controls the gain of the variable gain amplifier according to the comparison output. and a level adjustment circuit that changes the value of the reference power source of the comparator in accordance with the output signal of the control means.
（ネ）作用
本発明に依れば、可変利得増幅器の利得を太きくした場
合には比較器の基準を源の値も大きくし、前記可変利得
増幅器のリミッタレベルを大きくしている。又、前記可
変利得増幅器の利得を低下した場合には、前記比較器の
基準電源の値をノ」１さくしている。(f) Effect According to the present invention, when the gain of the variable gain amplifier is increased, the reference value of the comparator is also increased, and the limiter level of the variable gain amplifier is increased. Further, when the gain of the variable gain amplifier is lowered, the value of the reference power source of the comparator is reduced by 1.
（へ）実施例
第１図は、本発明の一実施例を示す回路図で、（８）は
可変抵抗（２）からの制御電圧に応じて比較器（５）の
可変基準電源（９）の値を変化させるレベル調整回路で
ある。(v) Embodiment Figure 1 is a circuit diagram showing an embodiment of the present invention. This is a level adjustment circuit that changes the value of .
尚、第１図において、第２図と同一の回路素子について
は同一の符号を付し、説明を省略する。In FIG. 1, circuit elements that are the same as those in FIG. 2 are denoted by the same reference numerals, and explanations thereof will be omitted.
第１図において、可変抵抗（２）がある値に設定きれて
おり、可変利得増幅器（１）の利得が第４図の実線Ａの
如き特性であるとする。この際、可変抵抗（２）から発
生する制御電圧に応じてレベル調整回路（８）は、可変
基準電源（９〉の値をｖｏに設定している。この状態か
ら、使用者が可変抵抗（２）の値を変化させ、制御電圧
の値を低下させて可変利得増幅器（１）の利得を低下許
せたとする。すると、レベル調整回路（８）は、前記制
御電圧が低下したことを検出し、可変基準を源（９）の
値を低下きせる。可変基準電源（９）の値が低下すれば
、可変利得増幅器（１）におけるリミッタレベル（ＡＧ
Ｃ動作の開始レベル）が小さくなる。その為、この状態
における可変利得増幅器（１）の入出力関係は、第４図
の実線Ｂの如くなる。以降、可変抵抗（２）を変化させ
、発生する制御電圧の値を低下きせると、それに応じて
可変基準電源（９）の値も低下するので、可変利得増幅
器（１）の入出力関係は、第４図のＣ及びＤの如くなる
。この様に、可変利得増幅器〈１）の利得を低下させれ
ば、可変利得増幅器（１）のリミッタレベルも同時に低
下するので、静かな音量で聴取者が聞いている最中に大
きな音量に変化したとしても、大なる音量の信号は、可
変利得増幅器（１）でリミットきれることになる。In FIG. 1, it is assumed that the variable resistor (2) has been set to a certain value, and the gain of the variable gain amplifier (1) has a characteristic as shown by the solid line A in FIG. At this time, the level adjustment circuit (8) sets the value of the variable reference power supply (9) to vo according to the control voltage generated from the variable resistor (2). Suppose that the gain of the variable gain amplifier (1) is allowed to decrease by changing the value of 2) and lowering the value of the control voltage.Then, the level adjustment circuit (8) detects that the control voltage has decreased. , lowers the value of the variable reference source (9).If the value of the variable reference power source (9) decreases, the limiter level (AG) in the variable gain amplifier (1) decreases.
C operation start level) becomes smaller. Therefore, the input/output relationship of the variable gain amplifier (1) in this state is as shown by the solid line B in FIG. 4. After that, when the variable resistor (2) is changed to lower the value of the generated control voltage, the value of the variable reference power supply (9) will also decrease accordingly, so the input/output relationship of the variable gain amplifier (1) will be as follows. It will look like C and D in Figure 4. In this way, if the gain of the variable gain amplifier (1) is lowered, the limiter level of the variable gain amplifier (1) will also be lowered at the same time, so while the listener is listening at a quiet volume, the volume will change to a loud one. Even so, a signal with a large volume will be limited by the variable gain amplifier (1).
第１図の実施例では、入力信号が音声信号の場合につい
て説明したが、入力信号が映像信号でコントラスト調整
を視聴者が行なう場合の利点は、次の様になる。視聴者
が画像をソフトな感じで見たく、コントラストが小さく
なるようにする場合、可変利得増幅器（１）の利得を低
下きせる。この状態で、可変利得増幅器（１）のリミッ
タレベルが高い値で固定のままであるとすると、映像信
号中にホワイトピークノイズがあっても該ノイズをその
まま出力してしまい、画面に局部的に大きなコントラス
トの箇所が生じてしまう。それに対して、前記リミッタ
レベルが低下すれば、前記ノイズはリミットされるので
目立たなくなり、画像の雰囲気を乱すことは無い。In the embodiment shown in FIG. 1, the case where the input signal is an audio signal has been described, but the advantages when the input signal is a video signal and the contrast adjustment is performed by the viewer are as follows. If the viewer wants to see the image with a soft feel and the contrast is small, the gain of the variable gain amplifier (1) is lowered. In this state, if the limiter level of the variable gain amplifier (1) remains fixed at a high value, even if there is white peak noise in the video signal, the noise will be output as is, causing localized noise on the screen. Areas with large contrasts will occur. On the other hand, if the limiter level is lowered, the noise is limited and becomes less noticeable and does not disturb the atmosphere of the image.
第５図は、マイクロコンピュータ（１０）からのデジタ
ル信号による制御を行なう場合の本発明の実施例を示す
もので、マイクロコンピュータ（１０）から可変利得増
幅器（１）の利得を制御する為のデジタル信号が発生し
、Ｄ／Ａ（デジタルアナログ）変換回路（１１）に印加
きれる。Ｄ／Ａ変換回路（１１）は、前記デジタル信号
に応じて、可変利得増幅器（１）の利得制御用のアナロ
グ信号を作成する。該アナログ信号は、レベル調整回路
（８）に印加きれ、更に可変基準電源（９）を制御する
為の信号に変換きれて可変基準電源（９）に印加される
。FIG. 5 shows an embodiment of the present invention in which control is performed using a digital signal from a microcomputer (10). A signal is generated and applied to the D/A (digital-to-analog) conversion circuit (11). The D/A conversion circuit (11) creates an analog signal for gain control of the variable gain amplifier (1) according to the digital signal. The analog signal is applied to the level adjustment circuit (8), further converted into a signal for controlling the variable reference power source (9), and applied to the variable reference power source (9).
一方、Ｄ／Ａ変換回路（１１）の出力信号は、比較器（
５）の出力信号と、混合回路（１２〉で混合きれて可変
利得増幅器（１）に印加される。尚、Ｄ／Ａ変換回路（
１１〉と比較器（５）で、可変利得増幅器（１）を独立
に制御しても良い。On the other hand, the output signal of the D/A conversion circuit (11) is transmitted to the comparator (
The output signal of the D/A conversion circuit (12) is mixed with the output signal of the D/A conversion circuit (12) and applied to the variable gain amplifier (1).
11> and the comparator (5) may independently control the variable gain amplifier (1).
（ト）発明の効果
以上述べた如く、本発明に依れば利用者の好みに応じて
、出力信号のレベル調整が行なえると共に、微小なレベ
ルの信号を出力させている場合には、該信号に対して過
大な出力信号の発生を自動的に防止することが出来るＡ
ＧＣ回路を提供することが出来る。(G) Effects of the Invention As described above, according to the present invention, the level of the output signal can be adjusted according to the user's preference, and when a minute level signal is output, the level of the output signal can be adjusted according to the user's preference. A that can automatically prevent the generation of an output signal that is excessive compared to the signal.
A GC circuit can be provided.
第１図は、本発明の一実施例を示す回路図、第２図は、
従来のＡＧＣ回路を示す回路図、第３図は第２図の説明
に供する為の特性図、第４図は第１図の説明に供する為
の特性図、及び第５図は第１図の別の実施例を示す回路
図である。
（１）・・・可変利得増幅器、 （２）・・・可変抵抗
、（３）・・・レベル検波回路、 （５）・・・比較器
、 （８）・・・レベル調整回路、 （９）・・・可変
基準電源。FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
A circuit diagram showing a conventional AGC circuit, FIG. 3 is a characteristic diagram for explaining FIG. 2, FIG. 4 is a characteristic diagram for explaining FIG. 1, and FIG. 5 is a characteristic diagram for explaining FIG. FIG. 3 is a circuit diagram showing another example. (1)...Variable gain amplifier, (2)...Variable resistor, (3)...Level detection circuit, (5)...Comparator, (8)...Level adjustment circuit, (9 )...Variable reference power supply.
Claims (2)
得増幅器の利得を変化させるための制御手段と、 前記可変利得増幅器の出力信号のレベル検波を行なうレ
ベル検波回路と、 該レベル検波回路の検波出力信号と基準電源の基準電圧
とを比較し、その比較出力に応じて前記可変利得増幅器
の利得を制御する比較器と、前記制御手段の出力信号に
応じて前記比較器の基準電源の値を変化させるレベル調
整回路と、から成ることを特徴とするＡＧＣ回路。(1) A variable gain amplifier that amplifies an input signal, a control means for changing the gain of the variable gain amplifier, a level detection circuit that performs level detection of the output signal of the variable gain amplifier, and a level detection circuit that performs level detection of the output signal of the variable gain amplifier. a comparator that compares the detection output signal with a reference voltage of a reference power source and controls the gain of the variable gain amplifier according to the comparison output; and a value of the reference power source of the comparator according to the output signal of the control means. An AGC circuit comprising: a level adjustment circuit for changing the level of the AGC circuit;
の低下に応じて前記比較器の基準電源の値を低下させる
ことを特徴とするＡＧＣ回路。(2) The AGC circuit is characterized in that the level adjustment circuit lowers the value of the reference power source of the comparator in accordance with a decrease in the output signal of the control means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2202018A JPH0732339B2 (en) | 1990-07-30 | 1990-07-30 | AGC circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2202018A JPH0732339B2 (en) | 1990-07-30 | 1990-07-30 | AGC circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0486113A true JPH0486113A (en) | 1992-03-18 |
| JPH0732339B2 JPH0732339B2 (en) | 1995-04-10 |
Family
ID=16450562
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2202018A Expired - Fee Related JPH0732339B2 (en) | 1990-07-30 | 1990-07-30 | AGC circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0732339B2 (en) |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0265515A (en) * | 1988-08-31 | 1990-03-06 | Nec Corp | Level control circuit |
-
1990
- 1990-07-30 JP JP2202018A patent/JPH0732339B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0265515A (en) * | 1988-08-31 | 1990-03-06 | Nec Corp | Level control circuit |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0732339B2 (en) | 1995-04-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |