JP3698988B2 - Carrier detection circuit and infrared remote control receiver - Google Patents

Description

に設定される。
【００６９】
図８は、うねりのある光ノイズに対する動作を説明するための波形図である。この図８（ａ）〜図８（ｄ）の各波形は、前述の図２（ａ）〜図２（ｄ）および図５（ａ）〜図５（ｄ）の各波形にそれぞれ対応している。図８（ｂ）で示すように、時刻ｔ１において出力信号Ｄｏｕｔがオンになると、前述のように定電流源６７による容量Ｃ１の放電電流Ｉ１がＩ１ｏｎに減少されているので、検波器３４の出力Ｄｅｔｔは緩やかに低下し、前記時刻ｔ３まで基準電圧Ｖｓを超えたままとなる。
【００７０】
このようにしてもまた、前記うねりに対する誤動作を防止することができるとともに、容量Ｃ１の放電電流Ｉ１を減少して、放電時間を長く設定することで前記うねりに対応しているので、キャリアが無い状態で前記出力Ｄｅｔｔが過剰に高くなってしまい、受信感度が低下して、本来の赤外線信号が受信できなくなってしまうような不具合を無くすこともできる。
【００７１】
本発明の実施の第４の形態について、図９および図１０に基づいて説明すれば、以下のとおりである。
【００７２】
図９は、本発明の実施の第４の形態のキャリア検出回路７０の電気的構成を示すブロック図である。このキャリア検出回路７０は、前述のキャリア検出回路３０，５０，６０に類似している。注目すべきは、このキャリア検出回路７０では、検波回路７１の検波器７４において、前記バンドパスフィルタ５の出力Ｓｉｇと前記キャリア検出レベルＤｅｔとの差分を増幅し、電圧出力する高速増幅器７６の入力オフセット電圧が、前記出力信号Ｄｏｕｔのオン時に増加されることである。
【００７３】
図１０は、前記高速増幅器７６の具体的構成を示す電気回路図である。この高速増幅器７６は、コンパレータ７２と、オフセット切換え回路７３とを備えて構成されている。コンパレータ７２は、前記キャリア検出レベルＤｅｔおよびバンドパスフィルタ５の出力Ｓｉｇがそれぞれベースに与えられる一対のトランジスタＱ２１，Ｑ２２と、前記トランジスタＱ２２のエミッタに接続される負荷抵抗Ｒ２１と、前記トランジスタＱ２１のエミッタおよび前記負荷抵抗Ｒ２１からトランジスタＱ２２のエミッタに電流を供給する定電流源７７と、前記トランジスタＱ２１，Ｑ２２のコレクタに接続され、相互に等しい面積でカレントミラー回路を構成するトランジスタＱ２３，Ｑ２４とを備えて構成される。トランジスタＱ２２とトランジスタＱ２４との接続点は、前記ダイオードＤ１への出力端となる。
【００７４】
前記定電流源７７は定電流２×Ｉ０３を供給しており、したがってトランジスタＱ２３，Ｑ２４を流れる電流は、共にＩ０３となる。ここで、Ｓｉｇ＞Ｄｅｔのとき、入力オフセットは、略Ｉ０３×Ｒ２１となる。
【００７５】
一方、オフセット切換え回路７３は、前記出力信号Ｄｏｕｔおよび基準電圧源７８からの予め定める基準電圧Ｖｒｅｆがそれぞれベースに与えられる一対のトランジスタＱ２５，Ｑ２６と、前記トランジスタＱ２５，Ｑ２６のエミッタに共通に電流を供給する定電流源７９と、前記トランジスタＱ２５，Ｑ２６のコレクタに接続され、相互に等しい面積でカレントミラー回路を構成するトランジスタＱ２７，Ｑ２８とを備えて構成される。トランジスタＱ２６とトランジスタＱ２８との接続点は、トランジスタＱ２２と負荷抵抗Ｒ２１との接続点と接続されている。
【００７６】
したがって、出力信号Ｄｏｕｔがオフの基準電圧Ｖｒｅｆよりも低い接地レベルであるときには、トランジスタＱ２５〜Ｑ２８はオフし、入力オフセットは前記Ｉ０３×Ｒ２１であるのに対して、出力信号Ｄｏｕｔがオンの基準電圧Ｖｒｅｆよりも高いハイレベルとなると、トランジスタＱ２５〜Ｑ２８はオンし、負荷抵抗Ｒ２１には定電流源７９による定電流Ｉ０４が流込み、入力オフセットは（Ｉ０３＋Ｉ０４）×Ｒ２１に増加する。
【００７７】
このように構成することによって、キャリアの有ることが検出されている出力信号Ｄｏｕｔのオン時には、出力Ｓｉｇのレベルを見掛上増加することで、前述と同様に、キャリア周波数よりも低いうねりに対して、キャリア周波数のパルス群の検出レベルを表す出力Ｄｅｔｔを基準電圧Ｖｓを超えたままで維持して、擬似的にパルス群を検出し続けている状態とし、所定時間後に積分出力Ｉｎｔを出力回路３３のスレッシュレベル以下として、出力信号Ｄｏｕｔを確実にオフ状態に復帰させ、誤動作を防止することができる。
【００７８】
また、出力Ｄｅｔｔを高く、すなわちキャリア検出レベルＤｅｔを高くして、感度を低下する点は、前述の各キャリア検出回路３０，５０，６０と同様であるけれども、直接に出力Ｄｅｔｔを操作しないので、感度が低下している時間を減少することもできる。
【００７９】
本発明の実施の第５の形態について、図１１および図１２に基づいて説明すれば、以下のとおりである。
【００８０】
図１１は、本発明の実施の第５の形態のキャリア検出回路８０の電気的構成を示すブロック図である。このキャリア検出回路８０は、前述のキャリア検出回路３０，５０，６０，７０に類似している。注目すべきは、このキャリア検出回路８０では、検波回路８１において、積分器８５の基準電圧源８８の基準電圧Ｖｓが、前記出力信号Ｄｏｕｔのオン時に低下されることである。
【００８１】
図１２は、前記基準電圧源８８の具体的構成を示す電気回路図である。この基準電圧源８８は、定電圧発生回路８２と、切換え回路８３と、出力バッファ回路８４とを備えて構成されている。定電圧発生回路８２は、トランジスタＱ３１〜Ｑ３６および抵抗Ｒ３１〜Ｒ３３から成り、抵抗Ｒ３１に定電流Ｉ０５を流し込み、Ｉ０５×Ｒ３１の定電圧を発生している。
【００８２】
一方、切換え回路８３は、前記出力信号Ｄｏｕｔおよび基準電圧源８６からの予め定める基準電圧Ｖｒｅｆがそれぞれベースに与えられる一対のトランジスタＱ３７，Ｑ３８と、前記トランジスタＱ３７，Ｑ３８のエミッタに共通に電流を供給する定電流源８７と、前記トランジスタＱ３７，Ｑ３８のコレクタに接続され、相互に等しい面積でカレントミラー回路を構成するトランジスタＱ３９，Ｑ４０とを備えて構成される。トランジスタＱ３７とトランジスタＱ３９との接続点は、前記トランジスタＱ３６と抵抗Ｒ３１との接続点に接続されている。
【００８３】
また、出力バッファ回路８４は、トランジスタＱ４１〜Ｑ４３、抵抗Ｒ３４および定電流源８９から成り、トランジスタＱ４１のベースが接続される前記トランジスタＱ３６と抵抗Ｒ３１との接続点の電圧、すなわち抵抗Ｒ３１の端子間電圧を、トランジスタＱ４３のベースから前記基準電圧Ｖｓとして出力する。
【００８４】
したがって、出力信号Ｄｏｕｔがオフの基準電圧Ｖｒｅｆよりも低い接地レベルであるときには、トランジスタＱ３７〜Ｑ４０はオンし、抵抗Ｒ３１には定電流源８７による定電流Ｉ０６も流れ込み、基準電圧Ｖｓは（Ｉ０５＋Ｉ０６）×Ｒ３１となっている。これに対して、出力信号Ｄｏｕｔがオンの基準電圧Ｖｒｅｆよりも高いハイレベルとなると、トランジスタＱ３７〜Ｑ４０はオフし、基準電圧Ｖｓは前記Ｉ０５×Ｒ３１に低下する。
【００８５】
このように構成することによって、キャリアの有ることが検出されている出力信号Ｄｏｕｔのオン時には、基準電圧Ｖｓを低下することで、前述と同様に、キャリア周波数よりも低いうねりに対して、キャリア周波数のパルス群の検出レベルを表す出力Ｄｅｔｔを該基準電圧Ｖｓを超えたままで維持して、擬似的にパルス群を検出し続けている状態とし、所定時間後に積分出力Ｉｎｔを出力回路３３のスレッシュレベル以下として、出力信号Ｄｏｕｔを確実にオフ状態に復帰させ、誤動作を防止することができる。
【００８６】
また、出力Ｄｅｔｔを操作するのではなく、基準電圧Ｖｓを操作することで、このような制御に伴う新たなノイズによる影響を少なくすることができ、前記誤動作に対する耐量を向上することができる。
【００８７】
本発明の実施の第６の形態について、図１３に基づいて説明すれば、以下のとおりである。
【００８８】
図１３は、本発明の実施の第６の形態の赤外線リモコンの受信機９１の電気的構成を示すブロック図である。この受信機９１では、赤外線信号はフォトダイオード９２で光電流信号Ｉｉｎに変換され、その光電流信号Ｉｉｎはアンプ９３において電流−電圧変換されるとともに、さらにアンプ９４で増幅された後、バンドパスフィルタ９５に入力される。バンドパスフィルタ９５ではキャリア周波数成分が抽出され、さらに検波回路９６において前記キャリア周波数成分からベースバンド周波数の送信コード成分が検波され、その検波出力が出力回路９７において予め定めるスレッシュレベルと比較されることで、キャリアの有無が判別されてデジタルのコード信号が復元され、前記出力回路９７から出力信号Ｄｏｕｔとして出力される。前記検波回路９６およびヒステリシスコンパレータから成る出力回路９７は、キャリア検出回路を構成する。
【００８９】
注目すべきは、この受信機９１では、前記フィードバックループ４２を介する出力回路９７からの出力信号Ｄｏｕｔは、アンプ９４またはバンドパスフィルタ９５の少なくとも一方に与えられ、前記出力信号Ｄｏｕｔがオンの期間は、それらのゲインが低下されることである。
【００９０】
このように構成することによって、キャリア周波数よりも低い周波数のうねりによってパルスレベルが変動しても、アンプ９４および／またはバンドパスフィルタ９５のゲイン低下によって、バンドパスフィルタ９５の出力Ｓｉｇはキャリア検出レベルＤｅｔ以下になる確率が高くなり、これによって検波回路９６の積分出力Ｉｎｔを出力回路９７のスレッシュレベル以下として、出力信号Ｄｏｕｔを確実にオフ状態に復帰させることができ、このようにしてもまた、キャリアの誤検出を防止することができる。
【００９１】
また、前記アンプ９４および／またはバンドパスフィルタ９５のゲイン低下は、所定の時定数を持って行われる。したがって、この時定数によって制御の応答を遅延させることで、出力信号Ｄｏｕｔの切換わりによるノイズの影響を低減することができ、誤動作発生の耐量を向上することができる。
【００９２】
さらにまた、アンプ９４のゲインを低下させる場合には、バンドパスフィルタ９５の中心周波数の変動やバンド幅の変動はなく、これに対してバンドパスフィルタ９５のゲインを低下させる場合には、キャリア検出回路の時定数による応答遅延を考慮する必要はなく、制御精度を向上することができる。
【００９３】
【発明の効果】
本発明のキャリア検出回路は、以上のように、検出すべきキャリア周波数のパルスを検波器で検出し、積分器でその出力が積分基準値以上である時間を積分することでキャリア周波数のパルスをグループで検出し、またその積分出力を前記検波器のキャリア検出レベルとして使用することで、積分容量を集積化可能な容量としても、高い応答性でキャリアの有無を検出するようにしたキャリア検出回路において、さらにレベル変更回路を設け、キャリアの有ることが検出されている期間は、検波器からの出力を、積分器における積分基準値に対して相対的に増加し、キャリア周波数よりも低い周波数のうねりによってパルスレベルが低下しても、キャリア周波数のパルス群の検出レベルを表す検波器からの出力は、キャリアを検出し続けている状態に維持する。
【００９４】
それゆえ、前記うねりによるキャリア検出レベルの低下を抑え、うねりによるパルスレベルが回復した後に確実にパルスレベルがキャリア検出レベル以下となるようにして、キャリアの誤検出を防止することができる。
【００９５】
また、本発明のキャリア検出回路では、以上のように、前記レベル変更回路は、キャリアの有る期間に、検波器からの出力を積分基準値よりも僅かに高い一定電圧に制限することで、該検波器からの出力を積分基準値に対して相対的に増加して、前記パルスレベルのうねりに対応する。
【００９６】
それゆえ、キャリアが無い状態で前記パルス群の検出レベルが過剰に高くなってしまい、本来の信号が送信されたときに、それを受信できなくなってしまうような不具合を無くすことができる。
【００９７】
さらにまた、本発明のキャリア検出回路では、以上のように、前記レベル変更回路は、キャリアの有る期間に、検波器の出力段における容量の放電電流を減少することで、該検波器からの出力を積分基準値に対して相対的に増加して、前記パルスレベルのうねりに対応する。
【００９８】
それゆえ、キャリアが無い状態で前記パルス群の検出レベルが過剰に高くなってしまい、本来の信号が送信されたときに、それを受信できなくなってしまうような不具合を無くすことができる。
【００９９】
また、本発明のキャリア検出回路では、以上のように、前記レベル変更回路は、キャリアの有る期間に、検波器への受信信号の入力オフセット電圧を増加することで、該検波器からの出力を積分基準値に対して相対的に増加して、前記パルスレベルのうねりに対応する。
【０１００】
それゆえ、直接に検波器からの出力を操作しないので、感度が低下している時間を減少することもできる。
【０１０１】
さらにまた、本発明のキャリア検出回路では、以上のように、前記レベル変更回路は、キャリアの有る期間に、積分器における積分基準値を低下することで、該検波器からの出力を積分基準値に対して相対的に増加して、前記パルスレベルのうねりに対応する。
【０１０２】
それゆえ、直接に検波器からの出力を操作しないので、制御に伴う新たなノイズによる影響を少なくすることができ、誤動作に対する耐量を向上することもできる。
【０１０３】
また、本発明の赤外線リモコン受信機は、以上のように、上記の何れかのキャリア検出回路を用いて、キャリアの有ることが検出されている期間は、検波器からの出力を積分器の積分基準値に対して相対的に増加する。
【０１０４】
それゆえ、うねりの有るノイズに対する受信機の誤動作を低減することができる。
【０１０５】
さらにまた、本発明の赤外線リモコン受信機は、以上のように、キャリア周波数のパルスをグループで検出することで、積分器においてキャリア検出レベルを出力する積分用の容量を集積化可能な容量とするようにした赤外線リモコン受信機において、ゲイン変更回路を設け、キャリアの有ることが検出されている期間は、アンプまたはバンドパスフィルタの少なくとも一方のゲインを低下する。
【０１０６】
それゆえ、キャリア周波数よりも低い周波数のうねりによってパルスレベルが変動しても、アンプまたはバンドパスフィルタの少なくとも一方のゲイン低下によって受信信号はキャリア検出レベル以下になる確率が高くなり、キャリアの誤検出を防止することができる。
【０１０７】
また、本発明の赤外線リモコン受信機では、以上のように、前記ゲイン変更回路は、ゲイン低下時に、時定数によって制御の応答を遅延させる。
【０１０８】
それゆえ、キャリアの有無の検出結果の切換わりによるノイズの影響を低減することができ、誤動作に対する耐量を向上することができる。
【図面の簡単な説明】
【図１】本発明の実施の第１の形態のキャリア検出回路の電気的構成を示すブロック図である。
【図２】図１で示すキャリア検出回路の動作を説明するための波形図である。
【図３】本発明の実施の第２の形態のキャリア検出回路の電気的構成を示すブロック図である。
【図４】図３で示すキャリア検出回路における電圧制限回路の一構成例を示す電気回路図である。
【図５】図３で示すキャリア検出回路の動作を説明するための波形図である。
【図６】本発明の実施の第３の形態のキャリア検出回路の電気的構成を示すブロック図である。
【図７】図６で示すキャリア検出回路における定電流源の一構成例を示す電気回路図である。
【図８】図６で示すキャリア検出回路の動作を説明するための波形図である。
【図９】本発明の実施の第４の形態のキャリア検出回路の電気的構成を示すブロック図である。
【図１０】図９で示すキャリア検出回路における高速増幅器の具体的構成を示す電気回路図である。
【図１１】本発明の実施の第５の形態のキャリア検出回路の電気的構成を示すブロック図である。
【図１２】図１１で示すキャリア検出回路における基準電圧源の具体的構成を示す電気回路図である。
【図１３】本発明の実施の第６の形態の赤外線リモコンの受信機の電気的構成を示すブロック図である。
【図１４】赤外線リモコンの受信機の一構成例を示すブロック図である。
【図１５】図１４の受信機における各部の波形図である。
【図１６】典型的な従来技術のキャリア検出回路の等価回路図である。
【図１７】図１６で示すキャリア検出回路の動作を説明するための波形図である。
【図１８】連続的な光ノイズが入力されている場合のキャリア検出回路の各部の波形を示す図である。
【図１９】うねりのある光ノイズが入力されている場合のキャリア検出回路の各部の波形を示す図である。
【図２０】赤外線リモコンの送信コード信号および受信コード信号を示す波形図である。
【符号の説明】
３０，５０，６０，７０，８０ キャリア検出回路
３１，６１，７１，８１ 検波回路
３２ 積分回路
３３ 出力回路
３４，６４，７４ 検波器
３５，８５ 積分器
３６ 高速増幅器
３７ 定電流源
３８，８６ 基準電圧源
３９，４０ アンプ
４１，５６，７７，７９，８７，８９ 定電流源
４２ フィードバックループ（レベル変更回路、ゲイン変更回路）
４３ トランジスタ（レベル変更回路）
５１ 電圧制限回路（レベル変更回路）
５２ 制限電圧発生回路
５４ スイッチ素子
５５ 基準電流源
６７ 定電流源（レベル変更回路）
６８，７８ 基準電流源
７６ 高速増幅器（レベル変更回路）
７２ コンパレータ
７３ オフセット切換え回路
８８ 基準電圧源（レベル変更回路）
８２ 定電圧発生回路
８３ 切換え回路
８４ 出力バッファ回路
９１ 受信機
９２ フォトダイオード
９３，９４ アンプ
９５ バンドパスフィルタ
９６ 検波回路
９７ 出力回路
Ｃ１，Ｃ２，Ｃ３ 容量
Ｄ１，Ｄ１０ ダイオード
Ｑ０〜Ｑ１０；Ｑ１１〜Ｑ１４；Ｑ２１〜Ｑ２８；Ｑ３１〜Ｑ４３トランジスタ
Ｒ１；Ｒ１１，Ｒ１２；Ｒ３１〜Ｒ３４ 抵抗
Ｒ２１ 負荷抵抗[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carrier detection circuit and an infrared remote control receiver that are preferably implemented as a demodulator of a signal including a carrier.
[0002]
[Prior art]
FIG. 14 is a block diagram showing a configuration example of the receiver 1 of the infrared remote controller, and FIG. 15 is a waveform diagram of each part in the general receiver 1. In the receiver 1, the infrared signal is converted into a photocurrent signal Iin as shown in FIG. 15A by the photodiode 2, and the photocurrent signal Iin is converted into a current-voltage by the amplifier 3, and further the amplifier 4. And then input to the band-pass filter 5. In the band-pass filter 5, a carrier frequency component is extracted as indicated by reference symbol α 1 in FIG. 15B, and further, in the detection circuit 6, from the carrier frequency component as indicated by reference symbol α 11 in FIG. 15C. The transmission code component of the baseband frequency is detected, and the detection output is compared with a predetermined threshold level indicated by reference numeral α12 in the output circuit 7, whereby the presence or absence of a carrier is determined and the digital code signal is restored. The output circuit 7 outputs the output signal Dout shown in FIG. An output circuit 7 comprising the detection circuit 6 and a hysteresis comparator constitutes a carrier detection circuit.
[0003]
FIG. 16 is an equivalent circuit diagram of a typical prior art carrier detection circuit 10. This carrier detection circuit 10 was previously proposed by the present applicant in Japanese Patent Application No. 2000-234926. The carrier detection circuit 10 includes a detection circuit 11, an integration circuit 12, and the hysteresis comparator 7. The detection circuit 11 generates a carrier detection level Det from the output Sig of the bandpass filter 5, and the integration circuit 12 The output Sig is compared with the carrier detection level Det, and the comparison result is integrated and supplied to the hysteresis comparator 7.
[0004]
It should be noted that in this carrier detection circuit 10, the detection circuit 11 detects pulses of the carrier frequency to be detected by the detector 13 as a group, integrates the time during which the pulse group exists by the integrator 14, and integrates the integration. The output is the carrier detection level Det. That is, the detector 13 is not used to directly generate the carrier detection level Det of the entire receiving system, but is used to generate the carrier detection level Det.
[0005]
The detector 13 amplifies the difference between the output Sig and the carrier detection level Det at a high speed capable of sufficiently responding to the carrier frequency and outputs a voltage, and the output of the high speed amplifier 15 Is provided with a diode d1 that rectifies the capacitor c1, a capacitor c1 that is charged with the output voltage of the high-speed amplifier 15 through the diode d1, and a constant current source 16 that discharges the capacitor c1 with a constant current i1. .
[0006]
The integrator 14 includes an amplifier 18 that outputs a current corresponding to a difference between a charging voltage of the capacitor c1, that is, an output Dett of the detector 13 and a predetermined reference voltage Vs from a reference voltage source 17, and the amplifier The capacitor c2 is charged with an output current of 18 and outputs the charging voltage as the carrier detection level Det.
[0007]
The integration circuit 12 includes a current output amplifier 19, a capacitor c3, and a constant current source 20 that discharges the capacitor c3 with a constant current i2, and outputs the output Sig of the bandpass filter 5 as a carrier. By comparing with the detection level Det and outputting a current corresponding to the comparison result to the capacitor c3, the carrier time is integrated and output as an integrated output Int.
[0008]
FIG. 17 is a waveform diagram for explaining the operation of the carrier detection circuit 10. When the high-speed amplifier 15 amplifies the difference between the output Sig of the bandpass filter 5 indicated by the reference symbol β1 in FIG. 17A and the carrier detection level Det indicated by the reference symbol β2, it is shown in FIG. 17B. As described above, in the period W1 in which the pulse of the carrier frequency is detected by the action of the diode d1, the capacitor c1 is charged, and the output Dett which is the detection level of the pulse group of the carrier frequency is high, and in the period W2 in which no pulse is detected. As a result, the output Dett is lowered by the discharge of the constant current source 16, and becomes zero level. Thus, the period W1 becomes a time in which a pulse group of the carrier frequency to be detected exists as described above, the integrator 14 integrates the period W1, and the integrated output shown in FIG. It becomes level Det.
[0009]
Here, the infrared signal is an ASK signal modulated with a predetermined carrier of about 30 to 60 kHz, and the capacity for outputting the carrier detection level Det is charged / discharged at the carrier frequency in the past. On the other hand, the time period W1, W2 is set to a sufficiently long time constant compared to the carrier frequency of about 100 msec, and the capacitance c2 for outputting the carrier detection level Det can be reduced to, for example, about 100 pF, and can be created in the integrated circuit. It is said.
[0010]
[Problems to be solved by the invention]
However, in the above-described conventional carrier detection circuit 10, noise is detected when the carrier detection level Det is reduced during the pause period for a code signal transmitted after a predetermined pause period. Therefore, since one transmission code of the infrared remote controller is about 50 msec, as described above, even if the carrier frequency pulse is detected in a group and the capacity c2 can be created in the integrated circuit, it is long. The discharge time constant is obtained.
[0011]
For this reason, although malfunction can be prevented for optical noise exceeding the discharge time constant, malfunction occurs for optical noise that periodically changes within the discharge time constant. There is a problem of end.
[0012]
FIG. 18 is a diagram showing waveforms at various parts when continuous optical noise is input from an inverter fluorescent lamp or the like substantially equal to the carrier frequency of the infrared signal. The output Dett shown in FIG. 18B is derived from the detector 13 by the output Sig of the bandpass filter 5 indicated by the reference symbol β11 in FIG. 18A, and when the reference voltage Vs is exceeded, in FIG. The carrier detection level Det indicated by the reference symbol β12 increases with a long time constant, and the integrated output Int indicated by the reference symbol β13 in FIG. 18C also increases. When the threshold level of the output circuit 7 indicated by reference symbol β14 is exceeded, the threshold level is lowered due to hysteresis, and the output signal Dout shown in FIG. 18D is also inverted, resulting in a malfunction.
[0013]
However, this malfunction occurs because the carrier detection level Det stops increasing near the peak of the output Sig of the bandpass filter 5, and in this state, the output becomes a low level due to the input offset of the amplifier 19, so that the constant current source When 20 discharges the capacitor c3 with the constant current i2 and the integrated output Int is reduced to be below the threshold level of the output circuit 7, normal operation can be restored.
[0014]
On the other hand, in reality, the light noise of the fluorescent lamp includes other frequency components such as a commercial frequency component of the power supply line, and swells with other frequency components occur. Malfunctions occur due to optical noise that periodically changes within a constant. FIG. 19 is a waveform diagram for explaining the operation against such undulating optical noise. The waveforms in FIGS. 19A to 19D correspond to the waveforms in FIGS. 18A to 18D, respectively.
[0015]
First, in the same manner as described above, the output Dett shown in FIG. 19B is derived from the detector 13 by the swell output Sig from the bandpass filter 5 indicated by the reference symbol β11a in FIG. When Vs is exceeded, the carrier detection level Det indicated by reference symbol β12a in FIG. 19A increases, and the integrated output Int indicated by reference symbol β13a in FIG. 19C also increases. When the threshold level of the output circuit 7 indicated by the reference symbol β14a is exceeded, the threshold level is lowered due to hysteresis, and the output signal Dout shown in FIG. 19D is also inverted to cause a malfunction.
[0016]
However, due to the undulation of the output Sig, the output Dett may become equal to or lower than the reference voltage Vs. As a result, the carrier detection level Det decreases, and the output Sig exceeds the carrier detection level Det again. Thus, the peak of the noise cannot be captured, and the integrated output Int is repeatedly increased and decreased at a constant level and does not fall below the threshold level that has been lowered due to the hysteresis. Therefore, the output signal Dout is not inverted, and the malfunction state Will continue.
[0017]
Here, FIG. 20A shows an example of the code signal transmitted, FIG. 20B shows the output signal Dout during normal operation, and FIG. 20C shows the malfunction state due to the wavy optical noise. The output signal Dout at. Since the noise is also roughly grasped by the wavy optical noise, if the level of the transmission signal itself is large to some extent, data can be restored as shown in FIG. However, in many code signals of remote controllers, a header which is a start code is added immediately before the data. If this header is not recognized as shown in FIG. 20C, the subsequent data is recognized. Cannot be performed, resulting in malfunction.
[0018]
An object of the present invention is to provide a carrier detection circuit and an infrared remote control receiver that can reduce malfunctions.
[0019]
[Means for Solving the Problems]
The carrier detection circuit according to the present invention detects a carrier frequency pulse to be detected in a carrier detection circuit that creates a carrier detection level based on a received signal and detects the presence or absence of a carrier using the carrier detection level. And an integrator for detecting a pulse of the carrier frequency in a group by integrating a time when an output from the detector is equal to or greater than a predetermined integration reference value, and outputting the integrated output as the carrier detection level And a period during which the presence of a carrier is detected includes a level changing circuit that relatively increases an output from the detector with respect to the integration reference value.
[0020]
According to said structure, a detector responds with respect to the noise superimposed on a carrier, and raises the carrier detection level produced by an integrator. On the other hand, in the integrator, a transistor that charges and discharges according to the presence or absence of the carrier in the integration capacitor that outputs the carrier detection level has a response to the frequency of the baseband component, not the carrier frequency. In other words, a margin for the response of the transistor can be ensured, and the charge / discharge current to the capacitor can be made very small.
[0021]
Thus, even if the capacity can be integrated, in the carrier detection circuit that detects the presence or absence of carriers with high responsiveness, a level change circuit is further provided, and the period during which the presence of carriers is detected is For example, as described in detail later, the output from the detector is increased relative to the integration reference value in the integrator.
[0022]
Therefore, even if the pulse level is lowered due to the swell of the frequency lower than the carrier frequency, the output from the detector indicating the detection level of the pulse group of the carrier frequency continues to detect the carrier, thereby causing the swell. A reduction in carrier detection level is suppressed, and after the pulse level due to waviness is restored, the pulse level is surely kept below the carrier detection level to prevent erroneous carrier detection.
[0023]
In this manner, the baseband component and the noise component are separated, and malfunctions with respect to wavy noise can be reduced, so that the baseband component can be accurately detected.
[0024]
In the carrier detection circuit of the present invention, the level changing circuit limits the output from the detector to a constant voltage slightly higher than the integration reference value during a period in which the carrier is present. The output from is increased relative to the integration reference value.
[0025]
According to the above configuration, in the period with the carrier, the output from the detector, which is the detection level of the pulse group, is limited to a constant voltage slightly higher than the integration reference voltage in the period without the pulse level. Corresponds to the swell.
[0026]
Accordingly, it is possible to eliminate such a problem that the detection level of the pulse group becomes excessively high in the absence of a carrier, and when the original signal is transmitted, it cannot be received.
[0027]
Furthermore, in the carrier detection circuit of the present invention, the level changing circuit reduces the discharge current of the capacitor in the output stage of the detector during a period in which the carrier is present, thereby integrating the output from the detector as an integration reference. It is characterized by increasing relative to the value.
[0028]
According to the above configuration, with respect to the capacity of the output stage of the detector whose output voltage represents the detection level of the pulse group, the discharge current is decreased in the period with the carrier than in the period without the carrier, and the discharge time. By setting a longer value, it corresponds to the undulation of the pulse level.
[0029]
Accordingly, it is possible to eliminate such a problem that the detection level of the pulse group becomes excessively high in the absence of a carrier, and when the original signal is transmitted, it cannot be received.
[0030]
In the carrier detection circuit of the present invention, the level changing circuit increases the input offset voltage of the received signal to the detector during a period in which the carrier is present, thereby converting the output from the detector into an integration reference value. Is relatively increased.
[0031]
According to the above configuration, by increasing the input offset voltage of the received signal to the detector, the signal level is apparently increased in the period with the carrier than in the period without the carrier, thereby causing the undulation of the pulse level. Corresponding to
[0032]
Therefore, since the output from the detector is not directly operated, the time during which the sensitivity is reduced can be reduced.
[0033]
Furthermore, in the carrier detection circuit of the present invention, the level changing circuit decreases the integration reference value in the integrator during a period in which the carrier is present, so that the output from the detector is compared with the integration reference value. It is characterized by a relative increase.
[0034]
According to the above configuration, by reducing the integration reference value of the integrator, the output level from the detector is apparently increased in the period with the carrier than in the period without the carrier, thereby causing the undulation of the pulse level. Corresponding to
[0035]
Therefore, since the output from the detector is not directly manipulated, the influence of new noise accompanying the control can be reduced, and the tolerance against malfunction can be improved.
[0036]
The infrared remote control receiver of the present invention is characterized by using any one of the carrier detection circuits described above.
[0037]
According to the above configuration, during the period in which the presence of the carrier is detected, the output from the detector is increased relative to the integration reference value of the integrator, and the receiver malfunctions due to swelled noise. Can be reduced.
[0038]
Furthermore, the infrared remote control receiver of the present invention inputs the received signal obtained by receiving the infrared signal to the bandpass filter through the amplifier, extracts the carrier frequency component to be detected, and then in the carrier detection circuit Detects the carrier frequency pulse, integrates the time when the detection result is equal to or greater than a predetermined integration reference value, detects the carrier frequency pulse in a group, and uses the integrated output as a carrier detection level to determine whether there is a carrier. In the infrared remote control receiver configured to detect a signal, a period during which the presence of a carrier is detected includes a gain changing circuit that lowers the gain of at least one of the amplifier and the band-pass filter.
[0039]
According to the above configuration, in the infrared remote control receiver capable of integrating the integration capacity for outputting the carrier detection level in the integrator, by detecting the carrier frequency pulse in groups, the gain can be integrated. During the period in which the change circuit is provided and the presence of the carrier is detected, the gain of at least one of the amplifier and the bandpass filter is reduced.
[0040]
Therefore, even if the pulse level fluctuates due to the swell of a frequency lower than the carrier frequency, the probability that the received signal will be lower than the carrier detection level due to a decrease in the gain of at least one of the amplifier or the bandpass filter increases, and erroneous carrier detection is performed. Can be prevented.
[0041]
In the infrared remote control receiver of the present invention, the gain changing circuit has a time constant when the gain is reduced.
[0042]
According to the above configuration, by delaying the control response by the time constant, it is possible to reduce the influence of noise due to switching of the detection result of the presence / absence of carriers, and to improve the tolerance against malfunction.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
The following describes the first embodiment of the present invention with reference to FIG. 1 and FIG.
[0044]
FIG. 1 is a block diagram showing an electrical configuration of a carrier detection circuit 30 according to the first embodiment of the present invention. The carrier detection circuit 30 generally includes a detection circuit 31, an integration circuit 32, and an output circuit 33. From the output Sig of the bandpass filter 5 shown in FIG. 14, the detection circuit 31 detects a carrier frequency pulse to be detected by the detector 34 as a group, and integrates the time in which the pulse group exists with an integrator 35. The output is the carrier detection level Det, the output circuit Sig is compared with the carrier detection level Det in the integration circuit 32, the comparison result is integrated, and then the output circuit 33 discriminates the level to create the output signal Dout. This is the same as the carrier detection circuit 10 shown in FIG.
[0045]
That is, the detector 34 amplifies the difference between the output Sig and the carrier detection level Det at a high speed capable of sufficiently responding to the carrier frequency and outputs a voltage, and the high speed amplifier 36. And a constant current source 37 for discharging the capacitor C1 with a constant current I1. The diode D1 rectifies the output of the capacitor C1, the capacitor C1 charged with the output voltage of the high-speed amplifier 36 through the diode D1. The peak hold operation of the output Sig is performed.
[0046]
The integrator 35 outputs an electric current corresponding to a difference between a charging voltage of the capacitor C1, that is, an output Dett of the detector 34, and a reference voltage Vs which is a predetermined integration reference value from a reference voltage source 38. 39 and a capacitor C2 that is charged with the output current of the amplifier 39 and outputs the charging voltage as the carrier detection level Det.
[0047]
The integrating circuit 32 includes a current output amplifier 40, a capacitor C3, and a constant current source 41 that discharges the capacitor C3 with a constant current I2, and outputs the output Sig of the bandpass filter 5 as a carrier. By comparing with the detection level Det and outputting a current corresponding to the comparison result to the capacitor C3, the time with a carrier is integrated and output as an integrated output Int. The output circuit 33 is composed of a hysteresis comparator, and generates a baseband frequency output signal Dout by discriminating the level of the integrated output Int from the integrating circuit 32.
[0048]
It should be noted that the carrier detection circuit 30 is provided with a feedback loop 42 that feeds back the output signal Dout from the output circuit 33 to the detector 34, and the transistor 43 to which the output signal Dout is given is provided with the feedback loop 42. When the output signal Dout is turned on, the charging voltage of the capacitor C1, which is the detection level of the pulse group, that is, the output Dett of the detector 34 is set to a predetermined constant voltage VC that is a substantially maximum value, thereby the carrier detection level Det. Increases, the sensitivity decreases, and the integrated output Int can be returned to the initial state.
[0049]
FIG. 2 is a waveform diagram for explaining the operation of the carrier detection circuit 30 configured as described above with respect to wavy optical noise. The output Dett shown in FIG. 2B is derived from the detector 34 by the output Sig of the bandpass filter 5 indicated by the reference symbol γ1 in FIG. 2A, and when the output Dett exceeds the reference voltage Vs, FIG. In FIG. 2A, the carrier detection level Det indicated by reference symbol γ2 increases with a long time constant, and the integrated output Int indicated by reference symbol γ3 in FIG. 2C also increases. When the threshold level of the output circuit 33 indicated by the reference symbol γ4 is exceeded at time t1, the threshold level is lowered due to hysteresis, and the output signal Dout shown in FIG. It becomes a state.
[0050]
However, in this state, since the output Dett of the detector 34 is set to the constant voltage VC by the transistor 43 as described above, even if the level of the output Sig shown in FIG. Dett remains above the reference voltage Vs, and the carrier detection level Det increases to a substantially maximum value. As a result, the integrated output Int decreases, and eventually becomes equal to or lower than the threshold level of the output circuit 33 at time t2, and the output signal Dout is inverted to OFF and returns to a normal state. When the output Dett becomes equal to or lower than the reference voltage Vs at time t3, the carrier detection level Det also starts to decrease.
[0051]
Although the above-described ON / OFF operation of the output signal Dout seems to be an oscillation phenomenon, since the time constant of the circuit is large as described above, the cycle is relatively long and the output signal Dout is in the OFF state. When the header of the transmission signal as shown by 20 (a) is received, the subsequent data can be received correctly without any problem as shown in FIG. 20 (b). Further, even when the on / off operation is repeated, the power consumption can be reduced as compared with the normal on state as shown in FIG. 19 (d). Since it does not occur when receiving a signal, there is no practical problem.
[0052]
In this way, when the output signal Dout in which the carrier is detected is turned on, the output Dett representing the detection level of the pulse group at the carrier frequency is used as the reference voltage Vs with respect to the swell lower than the carrier frequency of the output Sig. By maintaining a higher constant voltage VC and continuing to detect the pulse group in a pseudo manner, the output Sig level due to waviness is recovered, and the integrated output Int is set to be lower than the threshold level of the output circuit 33. The signal Dout can be reliably returned to the off state, and malfunction can be prevented. In this way, the code signal of the baseband frequency can be separated from the undulating noise and accurately detected.
[0053]
Here, for example, in Japanese Patent Laid-Open No. 6-188835, the current due to the shot noise depends on the square root of the current due to the incident light in order to remove the shot noise generated in the photodiode and passing through the band-pass filter. In consideration of this, the amplifier is configured to input to the amplifier through a matching circuit that squares the current caused by the incident light.
[0054]
However, any of the prior arts that consider such noise removal is handled by manipulating the input level to the amplifier, and the carrier is detected by normal envelope detection. In this regard, in the present invention and the above-mentioned Japanese Patent Application No. 2000-234926, the carrier detection level Det catches the peak of the disturbance light noise, that is, adapts to the level of the disturbance light noise and removes the noise component. Not only noise but also high noise removal ability can be exhibited.
[0055]
The following describes the second embodiment of the present invention with reference to FIGS.
[0056]
FIG. 3 is a block diagram showing an electrical configuration of the carrier detection circuit 50 according to the second embodiment of the present invention. The carrier detection circuit 50 is similar to the carrier detection circuit 30 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in the carrier detection circuit 50, the carrier detection circuit 30 described above maintains the output Dett of the detector 34 at a constant voltage VC when the output signal Dout is on, whereas the carrier detection circuit 50 uses the reference voltage Vs. Is limited to a slightly higher constant voltage Vc.
[0057]
For this reason, a voltage limiting circuit 51 that limits the output Dett to the voltage Vc is provided in association with the detector 34. The voltage limiting circuit 51 generally takes a reference voltage Vs from a reference voltage source 38, generates a voltage Vc slightly higher than the reference voltage Vs, and a feedback loop 42. The output signal Dout is applied to the line 53 from the capacitor C1 to the amplifier 39, and the output signal Dout provides the voltage Vc from the limit voltage generation circuit 52 in the on state, and the limit voltage generation circuit in the off state. And a switch element 54 that opens the line 52 from the line 53.
[0058]
FIG. 4 is an electric circuit diagram showing a configuration example of the voltage limiting circuit 51. The voltage limiting circuit 51 includes a reference current source 55 and transistors Q0 to Q3 constituting the switch element 54 by turning on / off the reference current I01 from the reference current source 55 in response to the output signal Dout. The resistor R1, the diode D10, the transistors Q4 to Q9 and the constant current source 56 that constitute the limit voltage generating circuit 52 that generates the voltage Vc, and the input transistor Q10 that takes in the output Data from the capacitor C1 are provided. It is configured.
[0059]
The transistor Q4 and the transistor Q5 form a pair, the base of the transistor Q4 is supplied with the reference voltage Vs, the emitter is connected to the collector of the transistor Q2 that supplies the reference current I01 through the resistor R1, and the collector is Grounded through transistor Q6. On the other hand, the base of the transistor Q5 is connected to the collector of the transistor Q3 supplying the reference current I01 and the emitter of the transistor Q9 paired with the input transistor Q10 via the diode D10, and to the ground via the transistor Q8. Is done. The base of the transistor Q5 is connected to a connection point between the input transistor Q10 connected in series between the power supply lines and the constant current source 56, and the base serves as an output terminal of the output Dett to the amplifier 39. Is connected to the collector of the transistor Q2, and the collector is grounded through the transistor Q6 and the transistor Q7 constituting a current mirror circuit.
[0060]
Therefore, when the output signal Dout is off, the transistors Q0 to Q3 are turned off and the transistors Q4 to Q9 do not operate, and the output Dett has a voltage reduced from the output Data of the capacitor C1 by the base-emitter voltage of the transistor Q10. The normal peak hold operation by the detector 34 is performed. On the other hand, when the output signal Dout is on, the transistors Q0 to Q3 are turned on to operate the transistors Q4 to Q9, and the output Dett is Vc (Vc = Vs + (I01 / 2) slightly higher than the reference voltage Vs. ) · R1) is limited to a constant voltage.
[0061]
FIG. 5 is a waveform diagram for explaining the operation against wavy optical noise. Each waveform in FIGS. 5A to 5D corresponds to each waveform in FIGS. 2A to 2D described above. As shown in FIG. 5B, when the output signal Dout is turned on at time t1, the output Dett is limited to a constant voltage of Vc.
[0062]
Even in this case, when the output signal Dout in which the presence of the carrier is detected is turned on, the output Dett representing the detection level of the pulse group of the carrier frequency is used as a reference with respect to the swell lower than the carrier frequency of the output Sig. The voltage Vs is maintained and the pulse group is continuously detected in a pseudo state, whereby the integrated output Int is set to the threshold level of the output circuit 33 or less after a predetermined time, and the output signal Dout is reliably turned off. To prevent the malfunction.
[0063]
Further, when the output signal Dout is turned on by the voltage limiting circuit 51, the output Dett, which is the detection level of the pulse group of the carrier frequency, is limited to a constant voltage Vc slightly higher than the reference voltage Vs, so that the output is performed in a state where there is no carrier. It is possible to eliminate the problem that Dett becomes excessively high, the reception sensitivity is lowered, and the original infrared signal cannot be received.
[0064]
The following describes the third embodiment of the present invention with reference to FIGS.
[0065]
FIG. 6 is a block diagram showing an electrical configuration of the carrier detection circuit 60 according to the third embodiment of the present invention. The carrier detection circuit 60 is similar to the carrier detection circuits 30 and 50 described above, and corresponding portions are denoted by the same reference numerals and description thereof is omitted. It should be noted that in this carrier detection circuit 60, the output signal Dout through the feedback loop 42 is supplied to the constant current source 67 of the detector 64 of the detection circuit 61, and the constant current source 67 has its constant current I1. Is a predetermined first current value I1off when the output signal Dout is in an off state, and decreases to a predetermined second current value I1on that is smaller than the I1off when the output signal Dout is in an on state.
[0066]
FIG. 7 is an electric circuit diagram showing a configuration example of the constant current source 67. The constant current source 67 includes a reference current source 68, four transistors Q11 to Q14, and two resistors R11 and R12. The reference current source 68, the transistor Q11, and the resistor R11 are interposed between the power supply lines in series with each other, and the base of the diode-connected transistor Q11 includes a transistor Q12 and a transistor that form a current mirror circuit. The base of Q13 is connected. The collector of the transistor Q13 is connected to the capacitor C1 to draw out the constant current I1, and the emitter is grounded via the resistor R12. On the other hand, the emitter of the transistor Q12 is also grounded via the resistor R12, and the collector of the transistor Q12 is connected to the high-level Vcc power line via the transistor Q14. The output signal Dout is supplied to the base of the transistor Q14 via the feedback loop 42.
[0067]
The emitter area ratio of the transistors Q11, Q12, and Q13 is 1: n: 1 (n> 1). Therefore, when the output signal Dout is off, the transistors Q14 and Q12 are off and the constant current is supplied. I1 is relatively large I1off, and when it is on, the transistors Q14 and Q12 are on, and the current from these transistors Q14 and Q12 flows into the resistor R12, so that the constant current I1 is relatively small. It becomes.
[0068]
The current values I1off and I1on are as follows: k is a Boltzmann constant, T is an absolute temperature, q is an elementary charge, and the current value of the reference current source 68 is I02.

Set to
[0069]
FIG. 8 is a waveform diagram for explaining the operation against wavy optical noise. The waveforms shown in FIGS. 8A to 8D correspond to the waveforms shown in FIGS. 2A to 2D and FIGS. 5A to 5D, respectively. Yes. As shown in FIG. 8B, when the output signal Dout is turned on at time t1, the discharge current I1 of the capacitor C1 by the constant current source 67 is reduced to I1on as described above, so the output of the detector 34 Dett gradually decreases and remains above the reference voltage Vs until time t3.
[0070]
Even in this case, it is possible to prevent malfunction due to the swell, and since the discharge current I1 of the capacitor C1 is reduced and the discharge time is set to be long, the swell is handled, so there is no carrier. In this state, the output Dett becomes excessively high, the reception sensitivity is lowered, and the problem that the original infrared signal cannot be received can be eliminated.
[0071]
The following describes the fourth embodiment of the present invention with reference to FIG. 9 and FIG.
[0072]
FIG. 9 is a block diagram showing an electrical configuration of the carrier detection circuit 70 according to the fourth embodiment of the present invention. The carrier detection circuit 70 is similar to the carrier detection circuits 30, 50, 60 described above. It should be noted that in this carrier detection circuit 70, the detector 74 of the detection circuit 71 amplifies the difference between the output Sig of the bandpass filter 5 and the carrier detection level Det, and inputs the voltage to the high speed amplifier 76 that outputs the voltage. The offset voltage is increased when the output signal Dout is turned on.
[0073]
FIG. 10 is an electric circuit diagram showing a specific configuration of the high-speed amplifier 76. The high-speed amplifier 76 includes a comparator 72 and an offset switching circuit 73. The comparator 72 includes a pair of transistors Q21 and Q22 to which the carrier detection level Det and the output Sig of the bandpass filter 5 are respectively applied to the base, a load resistor R21 connected to the emitter of the transistor Q22, and an emitter of the transistor Q21 And a constant current source 77 for supplying current from the load resistor R21 to the emitter of the transistor Q22, and transistors Q23 and Q24 connected to the collectors of the transistors Q21 and Q22 and forming a current mirror circuit with the same area. Configured. A connection point between the transistor Q22 and the transistor Q24 is an output terminal to the diode D1.
[0074]
The constant current source 77 supplies a constant current 2 × I03, so that the currents flowing through the transistors Q23 and Q24 are both I03. Here, when Sig> Det, the input offset is approximately I03 × R21.
[0075]
On the other hand, the offset switching circuit 73 supplies a current in common to the pair of transistors Q25 and Q26 to which the output signal Dout and the predetermined reference voltage Vref from the reference voltage source 78 are respectively applied to the base and the emitters of the transistors Q25 and Q26. A constant current source 79 to be supplied, and transistors Q27 and Q28 that are connected to the collectors of the transistors Q25 and Q26 and constitute a current mirror circuit with an equal area are configured. A connection point between the transistor Q26 and the transistor Q28 is connected to a connection point between the transistor Q22 and the load resistor R21.
[0076]
Therefore, when the output signal Dout is at a ground level lower than the off-reference voltage Vref, the transistors Q25 to Q28 are turned off, and the input offset is I03 × R21, whereas the output signal Dout is the on-reference voltage. When the level becomes higher than Vref, the transistors Q25 to Q28 are turned on, the constant current I04 from the constant current source 79 flows into the load resistor R21, and the input offset increases to (I03 + I04) × R21.
[0077]
With this configuration, when the output signal Dout in which the presence of carriers is detected is turned on, the level of the output Sig is apparently increased so that the swell lower than the carrier frequency can be prevented as described above. Thus, the output Dett representing the detection level of the pulse group at the carrier frequency is maintained while exceeding the reference voltage Vs so that the pulse group is continuously detected, and the integrated output Int is output to the output circuit 33 after a predetermined time. The output signal Dout can be reliably returned to the off state to prevent malfunction.
[0078]
Further, the point that the output Dett is increased, that is, the carrier detection level Det is increased to reduce the sensitivity is the same as that of each of the carrier detection circuits 30, 50, 60 described above, but the output Dett is not directly operated. The time during which the sensitivity is lowered can also be reduced.
[0079]
The following describes the fifth embodiment of the present invention with reference to FIG. 11 and FIG.
[0080]
FIG. 11 is a block diagram showing an electrical configuration of a carrier detection circuit 80 according to the fifth embodiment of the present invention. The carrier detection circuit 80 is similar to the carrier detection circuits 30, 50, 60, and 70 described above. It should be noted that in the carrier detection circuit 80, in the detection circuit 81, the reference voltage Vs of the reference voltage source 88 of the integrator 85 is lowered when the output signal Dout is turned on.
[0081]
FIG. 12 is an electric circuit diagram showing a specific configuration of the reference voltage source 88. The reference voltage source 88 includes a constant voltage generation circuit 82, a switching circuit 83, and an output buffer circuit 84. The constant voltage generation circuit 82 includes transistors Q31 to Q36 and resistors R31 to R33, and supplies a constant current I05 to the resistor R31 to generate a constant voltage of I05 × R31.
[0082]
On the other hand, the switching circuit 83 supplies current in common to a pair of transistors Q37 and Q38 to which the output signal Dout and a predetermined reference voltage Vref from the reference voltage source 86 are respectively applied to the base, and the emitters of the transistors Q37 and Q38. The constant current source 87 is connected to the collectors of the transistors Q37 and Q38, and the transistors Q39 and Q40 form a current mirror circuit with the same area. A connection point between the transistor Q37 and the transistor Q39 is connected to a connection point between the transistor Q36 and the resistor R31.
[0083]
The output buffer circuit 84 includes transistors Q41 to Q43, a resistor R34, and a constant current source 89. The output buffer circuit 84 is a voltage at the connection point between the transistor Q36 and the resistor R31 to which the base of the transistor Q41 is connected, that is, between the terminals of the resistor R31. A voltage is output from the base of the transistor Q43 as the reference voltage Vs.
[0084]
Therefore, when the output signal Dout is at a ground level lower than the off reference voltage Vref, the transistors Q37 to Q40 are turned on, the constant current I06 from the constant current source 87 flows into the resistor R31, and the reference voltage Vs is (I05 + I06). × R31. On the other hand, when the output signal Dout becomes a high level higher than the ON reference voltage Vref, the transistors Q37 to Q40 are turned OFF, and the reference voltage Vs is lowered to I05 × R31.
[0085]
With this configuration, when the output signal Dout in which the presence of a carrier is detected is turned on, the reference voltage Vs is reduced to reduce the carrier frequency against swells lower than the carrier frequency, as described above. The output Dett representing the detection level of the pulse group is maintained exceeding the reference voltage Vs so that the pulse group is continuously detected, and the integrated output Int is output to the threshold level of the output circuit 33 after a predetermined time. In the following, it is possible to reliably return the output signal Dout to the off state and prevent malfunction.
[0086]
Further, by manipulating the reference voltage Vs instead of manipulating the output Dett, it is possible to reduce the influence of new noise associated with such control, and to improve the tolerance against the malfunction.
[0087]
The following describes the sixth embodiment of the present invention with reference to FIG.
[0088]
FIG. 13 is a block diagram showing an electrical configuration of the receiver 91 of the infrared remote controller according to the sixth embodiment of the present invention. In this receiver 91, the infrared signal is converted into a photocurrent signal Iin by a photodiode 92, and the photocurrent signal Iin is converted from current to voltage by an amplifier 93 and further amplified by an amplifier 94, and then a bandpass filter. 95. A carrier frequency component is extracted by the band-pass filter 95, a transmission code component of a baseband frequency is detected from the carrier frequency component by the detection circuit 96, and the detection output is compared with a predetermined threshold level by the output circuit 97. Thus, the presence / absence of the carrier is determined, and the digital code signal is restored and output from the output circuit 97 as the output signal Dout. An output circuit 97 including the detection circuit 96 and a hysteresis comparator constitutes a carrier detection circuit.
[0089]
It should be noted that in this receiver 91, the output signal Dout from the output circuit 97 via the feedback loop 42 is supplied to at least one of the amplifier 94 or the bandpass filter 95, and the period during which the output signal Dout is on is That their gain is reduced.
[0090]
With this configuration, even if the pulse level fluctuates due to swell of a frequency lower than the carrier frequency, the output Sig of the bandpass filter 95 is reduced by the carrier detection level due to the gain reduction of the amplifier 94 and / or the bandpass filter 95 The probability of being equal to or lower than Det is increased, whereby the integrated output Int of the detection circuit 96 is set to be equal to or lower than the threshold level of the output circuit 97, and the output signal Dout can be reliably returned to the off state. Carrier detection errors can be prevented.
[0091]
Further, the gain reduction of the amplifier 94 and / or the band pass filter 95 is performed with a predetermined time constant. Therefore, by delaying the control response by this time constant, it is possible to reduce the influence of noise due to switching of the output signal Dout, and to improve the tolerance of malfunction occurrence.
[0092]
Furthermore, when the gain of the amplifier 94 is lowered, there is no fluctuation in the center frequency or bandwidth of the bandpass filter 95. On the other hand, when the gain of the bandpass filter 95 is lowered, carrier detection is performed. It is not necessary to consider the response delay due to the time constant of the circuit, and the control accuracy can be improved.
[0093]
【The invention's effect】
As described above, the carrier detection circuit of the present invention detects the carrier frequency pulse to be detected by the detector, and integrates the time when the output is equal to or greater than the integration reference value by the integrator, thereby generating the carrier frequency pulse. A carrier detection circuit that detects the presence or absence of a carrier with high responsiveness even if the integration capacity is a capacity that can be integrated by detecting the group and using the integrated output as the carrier detection level of the detector. In addition, a level change circuit is further provided, and during the period in which the presence of the carrier is detected, the output from the detector is increased relative to the integration reference value in the integrator, and the frequency of the carrier is lower than the carrier frequency. Even if the pulse level decreases due to undulation, the output from the detector that indicates the detection level of the pulse group at the carrier frequency continues to detect the carrier. To maintain the state.
[0094]
Therefore, it is possible to prevent the carrier detection level from being lowered by suppressing the decrease in the carrier detection level due to the swell and ensuring that the pulse level is equal to or lower than the carrier detection level after the pulse level due to the swell is restored.
[0095]
In the carrier detection circuit of the present invention, as described above, the level changing circuit limits the output from the detector to a constant voltage slightly higher than the integration reference value during a period in which the carrier exists, The output from the detector is increased relative to the integration reference value to accommodate the pulse level undulation.
[0096]
Therefore, it is possible to eliminate such a problem that the detection level of the pulse group becomes excessively high in the absence of a carrier, and when the original signal is transmitted, it cannot be received.
[0097]
Furthermore, in the carrier detection circuit of the present invention, as described above, the level change circuit reduces the discharge current of the capacitor in the output stage of the detector during a period in which there is a carrier, thereby outputting the output from the detector. Is increased relative to the integral reference value to correspond to the undulation of the pulse level.
[0098]
Therefore, it is possible to eliminate such a problem that the detection level of the pulse group becomes excessively high in the absence of a carrier, and when the original signal is transmitted, it cannot be received.
[0099]
Further, in the carrier detection circuit of the present invention, as described above, the level changing circuit increases the input offset voltage of the received signal to the detector during the period in which the carrier is present, thereby outputting the output from the detector. It increases relative to the integration reference value to correspond to the undulation of the pulse level.
[0100]
Therefore, since the output from the detector is not directly manipulated, the time during which the sensitivity is reduced can be reduced.
[0101]
Furthermore, in the carrier detection circuit of the present invention, as described above, the level changing circuit reduces the integration reference value in the integrator during the carrier period, thereby reducing the output from the detector to the integration reference value. Corresponding to the pulse level undulation.
[0102]
Therefore, since the output from the detector is not directly manipulated, the influence of new noise accompanying the control can be reduced, and the tolerance against malfunction can be improved.
[0103]
Further, as described above, the infrared remote control receiver of the present invention uses any of the carrier detection circuits described above, and outputs the output from the detector during the period during which the carrier is detected. Increases relative to the reference value.
[0104]
Therefore, the malfunction of the receiver with respect to the undulating noise can be reduced.
[0105]
Furthermore, as described above, the infrared remote control receiver according to the present invention detects the carrier frequency pulse in groups, thereby making the integration capacity for outputting the carrier detection level in the integrator a capacity that can be integrated. In the infrared remote control receiver configured as described above, a gain changing circuit is provided, and the gain of at least one of the amplifier and the band-pass filter is reduced during a period in which the presence of the carrier is detected.
[0106]
Therefore, even if the pulse level fluctuates due to the swell of a frequency lower than the carrier frequency, the probability that the received signal will be lower than the carrier detection level due to a decrease in the gain of at least one of the amplifier or the bandpass filter increases, and erroneous carrier detection Can be prevented.
[0107]
In the infrared remote control receiver of the present invention, as described above, the gain changing circuit delays a control response by a time constant when the gain is reduced.
[0108]
Therefore, it is possible to reduce the influence of noise due to switching of the detection result of the presence / absence of carriers, and to improve the tolerance against malfunction.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an electrical configuration of a carrier detection circuit according to a first embodiment of the present invention.
2 is a waveform diagram for explaining the operation of the carrier detection circuit shown in FIG. 1; FIG.
FIG. 3 is a block diagram showing an electrical configuration of a carrier detection circuit according to a second embodiment of the present invention.
4 is an electric circuit diagram showing a configuration example of a voltage limiting circuit in the carrier detection circuit shown in FIG. 3;
5 is a waveform diagram for explaining the operation of the carrier detection circuit shown in FIG. 3; FIG.
FIG. 6 is a block diagram showing an electrical configuration of a carrier detection circuit according to a third embodiment of the present invention.
7 is an electric circuit diagram showing a configuration example of a constant current source in the carrier detection circuit shown in FIG. 6;
8 is a waveform diagram for explaining the operation of the carrier detection circuit shown in FIG. 6;
FIG. 9 is a block diagram showing an electrical configuration of a carrier detection circuit according to a fourth embodiment of the present invention.
10 is an electric circuit diagram showing a specific configuration of a high-speed amplifier in the carrier detection circuit shown in FIG. 9;
FIG. 11 is a block diagram showing an electrical configuration of a carrier detection circuit according to a fifth embodiment of the present invention.
12 is an electric circuit diagram showing a specific configuration of a reference voltage source in the carrier detection circuit shown in FIG. 11. FIG.
FIG. 13 is a block diagram showing an electrical configuration of a receiver of an infrared remote controller according to a sixth embodiment of the present invention.
FIG. 14 is a block diagram illustrating a configuration example of a receiver of an infrared remote controller.
15 is a waveform diagram of each part in the receiver of FIG. 14;
FIG. 16 is an equivalent circuit diagram of a typical prior art carrier detection circuit.
17 is a waveform diagram for explaining the operation of the carrier detection circuit shown in FIG. 16;
FIG. 18 is a diagram illustrating waveforms at various parts of the carrier detection circuit when continuous optical noise is input.
FIG. 19 is a diagram showing waveforms at various parts of the carrier detection circuit when undulating optical noise is input.
FIG. 20 is a waveform diagram showing a transmission code signal and a reception code signal of the infrared remote controller.
[Explanation of symbols]
30, 50, 60, 70, 80 Carrier detection circuit
31, 61, 71, 81 Detection circuit
32 Integration circuit
33 Output circuit
34, 64, 74 detector
35,85 integrator
36 High-speed amplifier
37 Constant current source
38,86 Reference voltage source
39,40 amplifier
41, 56, 77, 79, 87, 89 Constant current source
42 Feedback loop (level change circuit, gain change circuit)
43 transistor (level change circuit)
51 Voltage limit circuit (level change circuit)
52 Limiting voltage generator
54 Switch element
55 Reference current source
67 Constant current source (level change circuit)
68, 78 Reference current source
76 High-speed amplifier (level change circuit)
72 Comparator
73 Offset switching circuit
88 Reference voltage source (level change circuit)
82 Constant voltage generator
83 Switching circuit
84 Output buffer circuit
91 Receiver
92 Photodiode
93,94 amplifier
95 Bandpass filter
96 Detection circuit
97 Output circuit
C1, C2, C3 capacity
D1, D10 diode
Q0 to Q10; Q11 to Q14; Q21 to Q28; Q31 to Q43 transistors
R1; R11, R12; R31 to R34 resistance
R21 load resistance

Claims (8)

An integration circuit that compares the input signal with the carrier detection level and integrates the comparison result;
A detection circuit that generates a carrier detection level from an input signal and outputs the carrier detection level; and
In a carrier detection circuit including an output circuit that discriminates the presence or absence of a carrier by level discrimination of the output of the integration circuit,
The detection circuit includes a detector and an integrator,
The detector amplifies a difference between the input signal and the carrier detection level at a high speed capable of sufficiently responding to a carrier frequency and outputs a voltage, and a diode for rectifying the output of the high speed amplifier And charging with the output voltage of the high-speed amplifier via the diode, and outputting the charging voltage to the integrator as the output of the detector, and discharging the first capacitor with a constant current. With a constant current source,
The integrator is charged with an amplifier that outputs a current corresponding to a difference between the output of the detector and a reference voltage that is a predetermined integration reference value from a reference voltage source, and the output current of the amplifier, and the charging A second capacitor for outputting a voltage as the carrier detection level to the integrating circuit and the high-speed amplifier;
Further, the carrier detection circuit is provided with a level changing circuit that makes the output from the detector higher than the integral reference value during a period in which the output circuit detects the presence of a carrier. A characteristic carrier detection circuit.   The level changing circuit limits the output from the detector to a constant voltage slightly higher than the integration reference value during a period in which the carrier is present, thereby reducing the output from the detector with respect to the integration reference value. 2. The carrier detection circuit according to claim 1, wherein the carrier detection circuit increases relatively. An integration circuit that compares the input signal with the carrier detection level and integrates the comparison result;
A detection circuit that generates a carrier detection level from an input signal and outputs the carrier detection level; and
In a carrier detection circuit including an output circuit that discriminates the presence or absence of a carrier by level discrimination of the output of the integration circuit,
The detection circuit includes a detector and an integrator,
The detector amplifies a difference between the input signal and the carrier detection level at a high speed capable of sufficiently responding to a carrier frequency and outputs a voltage, and a diode for rectifying the output of the high speed amplifier If, Rutotomoni is charged via the diode by the output voltage of the high-speed amplifier, a first capacitor to output the charging voltage to the integrator as the output of the detector, discharging the first capacitor with a constant current With a constant current source,
The integrator is charged with an amplifier that outputs a current corresponding to a difference between the output of the detector and a reference voltage that is a predetermined integration reference value from a reference voltage source, and the output current of the amplifier, and the charging A second capacitor for outputting a voltage as the carrier detection level to the integrating circuit and the high-speed amplifier;
Further, the carrier detection circuit is provided with a level changing circuit for reducing the discharge current of the constant current source during a period in which the presence of the carrier is detected by the output circuit compared to a period in which there is no carrier. Carrier detection circuit. An integration circuit that compares the input signal with the carrier detection level and integrates the comparison result;
A detection circuit that generates a carrier detection level from an input signal and outputs the carrier detection level; and
In a carrier detection circuit including an output circuit that discriminates the presence or absence of a carrier by level discrimination of the output of the integration circuit,
The detection circuit includes a detector and an integrator,
The detector amplifies a difference between the input signal and the carrier detection level at a high speed capable of sufficiently responding to a carrier frequency and outputs a voltage, and a diode for rectifying the output of the high speed amplifier And charging with the output voltage of the high-speed amplifier via the diode, and outputting the charging voltage to the integrator as the output of the detector, and discharging the first capacitor with a constant current. With a constant current source,
The integrator is charged with an amplifier that outputs a current corresponding to a difference between the output of the detector and a reference voltage that is a predetermined integration reference value from a reference voltage source, and the output current of the amplifier, and the charging A second capacitor for outputting a voltage as the carrier detection level to the integrating circuit and the high-speed amplifier;
Further, the carrier detection circuit is provided with a level changing circuit that increases the input offset voltage of the input signal to the detector during a period in which the presence of the carrier is detected by the output circuit, compared to a period in which there is no carrier. carrier detection circuit, characterized by that. An integration circuit that compares the input signal with the carrier detection level and integrates the comparison result;
A detection circuit that generates a carrier detection level from an input signal and outputs the carrier detection level; and
In a carrier detection circuit including an output circuit that discriminates the presence or absence of a carrier by level discrimination of the output of the integration circuit,
The detection circuit includes a detector and an integrator,
The detector amplifies a difference between the input signal and the carrier detection level at a high speed capable of sufficiently responding to a carrier frequency and outputs a voltage, and a diode for rectifying the output of the high speed amplifier And charging with the output voltage of the high-speed amplifier via the diode, and outputting the charging voltage to the integrator as the output of the detector, and discharging the first capacitor with a constant current. With a constant current source,
The integrator is charged with an amplifier that outputs a current corresponding to a difference between the output of the detector and a reference voltage that is a predetermined integration reference value from a reference voltage source, and the output current of the amplifier, and the charging A second capacitor for outputting a voltage as the carrier detection level to the integrating circuit and the high-speed amplifier;
Further, the carrier detection circuit is provided with a level changing circuit that lowers the integration reference value in the integrator during a period in which the presence of the carrier is detected by the output circuit than in a period in which the carrier is not present. A characteristic carrier detection circuit. An infrared remote control receiver comprising the carrier detection circuit according to any one of claims 1 to 5. A first amplifier for amplifying a received signal obtained by receiving an infrared signal;
A bandpass filter for extracting a carrier frequency component to be detected from the received signal amplified by the first amplifier;
A carrier detection circuit that detects the presence or absence of a carrier based on the carrier frequency component;
The carrier detection circuit compares the carrier frequency component as an input signal with a carrier detection level, and integrates the comparison result;
An output circuit for discriminating the presence or absence of a carrier by level discrimination of the output of the integration circuit;
An infrared remote control receiver including a detection circuit that generates a carrier detection level from an input signal and outputs the carrier detection level to the integration circuit,
The detection circuit includes a detector and an integrator,
The detector amplifies a difference between the input signal and the carrier detection level at a high speed capable of sufficiently responding to a carrier frequency and outputs a voltage, and a diode for rectifying the output of the high speed amplifier And charging with the output voltage of the high-speed amplifier via the diode, and outputting the charging voltage to the integrator as the output of the detector, and discharging the first capacitor with a constant current. With a constant current source,
The integrator is charged with a second amplifier that outputs a current corresponding to a difference between an output of the detector and a reference voltage that is a predetermined integral reference value from a reference voltage source, and an output current of the second amplifier. The integration circuit and the high-speed amplifier using the charging voltage as the carrier detection level With a second capacity to output to
Furthermore, the infrared remote control receiver is provided with a gain changing circuit that reduces the gain of at least one of the first amplifier or the band-pass filter during a period when the presence of the carrier is detected by the output circuit. An infrared remote control receiver characterized by that. 8. The infrared remote control receiver according to claim 7, wherein the gain changing circuit has a time constant when the gain is lowered, and delays a control response for reducing the gain.

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