JP2004053396A - Angular velocity sensor and car using it - Google Patents

Angular velocity sensor and car using it Download PDF

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Publication number
JP2004053396A
JP2004053396A JP2002210748A JP2002210748A JP2004053396A JP 2004053396 A JP2004053396 A JP 2004053396A JP 2002210748 A JP2002210748 A JP 2002210748A JP 2002210748 A JP2002210748 A JP 2002210748A JP 2004053396 A JP2004053396 A JP 2004053396A
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Prior art keywords
circuit
angular velocity
electrode
monitor
velocity sensor
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JP2002210748A
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Japanese (ja)
Inventor
Keisuke Kuroda
黒田　啓介
Toshiyuki Nozoe
野添　利幸
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an angular velocity sensor capable of obtaining output signal stable for source voltage fluctuation and a car using it. <P>SOLUTION: The sensor comprises a vibration element 2 having at least a drive electrode 3, a monitor electrode 4 and a detection electrode 5; a drive circuit 6 connected with the drive electrode 3 of the vibration element 2; a detection circuit 8 connected with the detection electrode 5 of the vibration element 2; a monitor circuit 7 connected with a monitor electrode 4 of the vibration element 2; and a vibration control circuit 10 in between the monitor circuit 7 and the drive circuit 6. With a constitution in that the gain of the detection circuit 8 is proportional to the source voltage 1 practically independently from the source voltage which supplies the drive circuit 6 and the monitor circuit 7 with a reference voltage of the vibration control circuit 10, stable output signal of the angular velocity sensor can be obtained even with fluctuation of the source voltage 1. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、角速度センサおよびそれを用いた自動車に関するものである。
【０００２】
【従来の技術】
図７は従来の角速度センサの一例を示す回路図である。
【０００３】
この角速度センサは、駆動電極３、モニタ電極４、検出電極５とを有する振動素子２と、この振動素子２の駆動電極３に接続した駆動回路６と、振動素子２の検出電極５に接続した検出回路８と、振動素子２のモニタ電極４に接続したモニタ回路７と、このモニタ回路７と駆動回路６の間に振動制御回路１０とを備え、この振動制御回路１０に入力する基準電圧は電源電圧１に比例する基準電圧回路１９より供給される。
【０００４】
一方、角速度センサの入力角速度に対する感度は、振動素子２の駆動速度、すなわち駆動振幅に比例する。上記の構成では、振動制御回路１０に入力する基準電圧が電源電圧１に比例するため、振動素子２の駆動振幅は電源電圧１に比例するよう制御される。従って角速度センサに角速度が入力されたとき、角速度に応じて検出電極５から検出回路８に入力される信号は電源電圧１に比例するが、検出回路８の利得は演算増幅器の入力抵抗と帰還抵抗との抵抗比によって決定されるため、電源電圧１には比例せずほぼ一定である。
【０００５】
【発明が解決しようとする課題】
しかしながら上記従来の構成では、例えば角速度センサの電源電圧１が自動車のバッテリーから供給されるブレーキシステムにおいては、同じくバッテリーから電源電圧１が供給されている自動車の前照灯などをオンした瞬間など、一時的にバッテリー電圧が低下するため、角速度センサに供給される電源電圧１も瞬間的に低下し、角速度センサの出力信号が不安定になるという課題があった。
【０００６】
すなわち、振動制御回路１０の基準電圧が電源電圧１の低下に追従して低下し、その低下した基準電圧に対して再び振動の制御がかかり、振動素子２の駆動振幅は低下する。このとき、基準電圧の低下に応じた駆動振幅が収束するまでの応答時間の遅れにより、一時的に振動素子２の駆動振幅は電源電圧１に比例せず不安定となる。この間に角速度センサに角速度が入力されると、入力角速度に対する感度は不安定となり、例えばブレーキシステムでマイコン等を用いてセンサ信号出力のＡ／Ｄ変換を行う場合においては、同じくバッテリーから供給されているマイコンの電源電圧１の低下、すなわちＡ／Ｄ変換の基準電圧の低下に対し、誤った出力レベルが読み込まれてしまうことになる。
【０００７】
本発明は上記課題を解決するもので、電源電圧１の変動に対しても安定した出力信号を得ることができる角速度センサおよびそれを用いた自動車を提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記目的を達成するために、本発明は以下の構成を有する。
【０００９】
本発明の請求項１に記載の発明は、少なくとも駆動電極、モニタ電極、検出電極とを有する振動素子と、この振動素子の駆動電極に接続した駆動回路と、前記振動素子の検出電極に接続した検出回路と、前記振動素子のモニタ電極に接続したモニタ回路と、前記モニタ回路と駆動回路の間に振動制御回路を備え、この振動制御回路の基準電圧を前記駆動回路とモニタ回路に供給する電圧電源とは実質的に独立して前記検出回路の利得が電源電圧に比例するようにした構成により、電源電圧が変動した場合においても振動制御回路の基準電圧は追従して変動しないため、振動素子の駆動振幅は安定状態を保ち、そして検出回路の利得が電源電圧に比例するよう設定されているため、入力角速度に対するセンサの感度はトータルでは電源電圧に比例することになり、安定した角速度センサの出力信号を得ることができる。
【００１０】
本発明の請求項２に記載の発明は、振動制御回路の基準電圧をバンドギャップ型基準電圧源回路から供給した構成であり、請求項１記載の発明と同様の作用を有する。
【００１１】
本発明の請求項３に記載の発明は、ＭＯＳトランジスタ抵抗を入力抵抗または帰還抵抗に用いた演算増幅器を備えた検出回路の構成であり、請求項１記載の発明と同様の作用を有する。
【００１２】
本発明の請求項４に記載の発明は、車体を支える複数のタイヤに設けたブレーキシステムにおいて請求項１〜３に記載の角速度センサのいずれか１つを備えた自動車であり、電源が変動した場合においても安定した角速度センサの出力信号を得ることができると共に角速度センサによって検出した角速度情報に対応した適切な制御を行うことができる。
【００１３】
本発明の請求項５に記載の発明は、車体に備えられた少なくとも１つの座席に設置されるエアバッグシステムにおいて請求項１〜３に記載の角速度センサのいずれか１つを備えた自動車であり、電源が変動した場合においても安定した角速度センサの出力信号を得ることができると共に角速度センサによって検出した角速度情報に対応した適切な制御を行うことができる。
【００１４】
【発明の実施の形態】
以下、本発明の一実施の形態について図を参照しながら説明する。
【００１５】
図１は本発明の一実施の形態における角速度センサの回路図である。１は電源電圧、２は角速度を検出する振動素子、３は振動素子２に形成した駆動電極、４は振動素子２に形成したモニタ電極、５は振動素子２に形成した検出電極である。６は駆動電極３に接続した駆動回路、７はモニタ電極４に接続したモニタ回路、８は検出電極５に接続した検出回路、９は検出回路８に接続した角速度センサの出力端子である。
【００１６】
１０はモニタ回路７と駆動回路６の間に介在される振動制御回路である。１１は第１の電圧供給回路であり、振動制御回路１０に電源電圧１から実質的に独立した第１の基準電圧３２を供給する。
【００１７】
１７はバンドギャップ型基準電圧源回路であり、図２にその回路構成を示す。バンドギャップ型基準電圧源回路１７は、温度特性に優れ、かつ電源電圧１に実質的に独立した高精度な基準電圧約１．２Ｖを出力する。なおバンドギャップ型基準電圧源回路１７は周知のため、ここでは回路構成および動作についての説明を省略する。
【００１８】
１８は増幅回路であり、バンドギャップ型基準電圧源回路１７の出力電圧が入力される。増幅回路１８は入力信号を増幅し、振動制御回路１０に電源電圧１と接地電圧の中点近傍の電圧（例えば２．５Ｖ）である第１の基準電圧３２を供給する。
【００１９】
図３に電源電圧１の変動時の角速度センサの出力波形図を示す。従来技術の角速度センサはトランジェントが発生しているのに比べて本発明の角速度センサは電源電圧１が低下した場合においても、振動制御回路１０の基準電圧である第１の基準電圧３２は安定であるため、駆動振幅が収束するまでの応答時間の遅れも発生しない。ゆえに振動素子２の駆動振幅は安定であり、入力角速度に対して安定した感度を得ることができる。
【００２０】
また、１２は検出回路８に備えられた演算増幅器であり、その入力抵抗としてのＭＯＳトランジスタ抵抗２１、その帰還抵抗としての第１の抵抗２０、および第２の基準電圧３３より構成される。第２の基準電圧３３は第２の電圧供給回路１３より供給される。ＭＯＳトランジスタ抵抗２１のゲートは接地電位に接続され、ソースは演算増幅器１２の反転入力端子および第１の抵抗２０に接続され、ドレインは入力端子となる。第１の抵抗２０はＭＯＳトランジスタ抵抗２１および演算増幅器１２の出力端子との間に接続される。第２の基準電圧３３は演算増幅器１２の非反転入力端子に供給される。ここではＭＯＳトランジスタ抵抗を入力抵抗に用いたが帰還抵抗に用いても同様である。
【００２１】
図４に第２の電圧供給回路１３の一実施の形態の回路図を示す。１４は出力端子と反転入力端子を接続したボルテージフォロワ型バッファ、１５はダイオード接続されたＭＯＳトランジスタ、１６は定電流源である。バッファ１４の非反転入力端子には電源電圧１の中点電位が入力され、またＭＯＳトランジスタ１５と定電流源１６との接続点の電圧を第２の基準電圧３３に供給する。
【００２２】
このとき第２の基準電圧３３をＶｒｅｆ２とすると、電源電圧１をＶｃｃ、ＭＯＳトランジスタ１５のしきい値電圧をＶｔとして次式で表される。
【００２３】
【数１】

Figure 2004053396
【００２４】
また、ＭＯＳトランジスタ抵抗２１をＲｔとすると、次式で表される。
【００２５】
【数２】
Figure 2004053396
【００２６】
ここで、μ０はチャネル表面移動度、Ｃｏｘはゲート酸化膜の単位容量、Ｗはトランジスタの実効ゲート幅、Ｌはトランジスタの実効ゲート長さ、Ｖｇｓはトランジスタのゲート−ソース間電圧、Ｖｔはしきい値電圧を表す。
【００２７】
ＭＯＳトランジスタ抵抗２１のソース電位は、演算増幅器１２のイマジナリティ・ショートにより第２の基準電圧３３となるので、
【００２８】
【数３】
Figure 2004053396
【００２９】
となる。よって（数１）から（数３）より、
【００３０】
【数４】
Figure 2004053396
【００３１】
となる。ここでμ０、Ｃｏｘ、Ｗ、Ｌは電源電圧１に対して独立であるので、ＭＯＳトランジスタ抵抗２１は電源電圧１に反比例する。
【００３２】
また、演算増幅器１２の利得をＡｖとすると、第１の抵抗２０をＲｆｂとして次式で表される。
【００３３】
【数５】
Figure 2004053396
【００３４】
よって、（数４）、（数５）より、
【００３５】
【数６】
Figure 2004053396
【００３６】
となり、演算増幅器１２の利得Ａｖは電源電圧１に比例する。
【００３７】
よって、検出回路８の利得は電源電圧１に比例するので、入力角速度に対するセンサの感度はトータルでは電源電圧１に比例することになり、マイコン等を用いてセンサ信号出力のＡ／Ｄ変換を行う場合においても、電源電圧１の低下、すなわちＡ／Ｄ変換の基準電圧の低下に対してセンサ感度のレシオメトリック特性は確保され、誤った出力レベルが読み込まれることが回避できる。
【００３８】
図５は角速度センサを自動車のブレーキシステムに用いたブロック図である。２２は車体、２３は車体２２を支えた複数のタイヤ、２４はタイヤ２３に設けたブレーキシステム、２５はブレーキシステム２４を制御する第１のマイコン、２６はマイコン２５に検出出力を供給する角速度センサ、２７は車体２２に備えられた前照灯、２８はブレーキシステム２４、角速度センサ２６および前照灯２７に電源電圧１を供給するバッテリーである。本構成をとることにより、電源電圧１の変動に対しても安定な角速度センサによって検出した角速度情報に対応し、ブレーキシステムで適切な制御が行えるものとなる。
【００３９】
また、図６に角速度センサを自動車のエアバッグシステムに用いたブロック図を示す。２９は車体に設置された少なくとも１つの座席、３０は座席２９付近に設置されるエアバッグシステム、３１はエアバッグシステム３０を制御する第２のマイコンである。エアバッグシステム３０、角速度センサ２６および前照灯２７にはバッテリー２８より電源が供給される。本構成をとることにより、電源電圧１の変動に対しても安定な角速度センサによって検出した角速度情報に対応し、エアバッグシステムで適切な制御が行えるものとなる。
【００４０】
【発明の効果】
以上のように本発明によれば、センサに供給される電源電圧が変動した場合においても、振動素子の駆動振幅を安定させることができ、安定なセンサ信号出力を得ることができる。特に、駆動振幅が収束までの応答時間の遅れが大きくなる負荷容量の大きな振動素子を駆動する場合などにおいては、その効果が顕著である。
【図面の簡単な説明】
【図１】本発明の一実施の形態における角速度センサの回路図
【図２】バンドギャップ型基準電圧源回路の一例を示す回路図
【図３】（ａ），（ｂ）電源電圧変動時の角速度センサの出力波形図
【図４】第２の電圧供給回路の一例を示す回路図
【図５】角速度センサを自動車のブレーキシステムに用いたブロック図
【図６】角速度センサを自動車のエアバッグシステムに用いたブロック図
【図７】従来の角速度センサの一例を示す回路図
【符号の説明】
１　電源電圧
２　振動素子
３　駆動電極
４　モニタ電極
５　検出電極
６　駆動回路
７　モニタ回路
８　検出回路
９　センサ出力端子
１０　振動制御回路
１１　第１の電圧供給回路
１２　演算増幅器
１３　第２の電圧供給回路
１４　バッファ
１５　ＭＯＳトランジスタ
１６　定電流源
１７　バンドギャップ型基準電圧源回路
１８　増幅回路
１９　電源電圧に比例する基準電圧回路
２０　第１の抵抗
２１　ＭＯＳトランジスタ抵抗
２２　車体
２３　タイヤ
２４　ブレーキシステム
２５　第１のマイコン
２６　角速度センサ
２７　前照灯
２８　バッテリー
２９　座席
３０　エアバッグシステム
３１　第２のマイコン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an angular velocity sensor and an automobile using the same.
[0002]
[Prior art]
FIG. 7 is a circuit diagram showing an example of a conventional angular velocity sensor.
[0003]
This angular velocity sensor was connected to a vibration element 2 having a drive electrode 3, a monitor electrode 4, and a detection electrode 5, a drive circuit 6 connected to the drive electrode 3 of the vibration element 2, and a detection electrode 5 of the vibration element 2. A detection circuit 8, a monitor circuit 7 connected to the monitor electrode 4 of the vibration element 2, and a vibration control circuit 10 between the monitor circuit 7 and the drive circuit 6 are provided. The reference voltage input to the vibration control circuit 10 is It is supplied from a reference voltage circuit 19 proportional to the power supply voltage 1.
[0004]
On the other hand, the sensitivity of the angular velocity sensor to the input angular velocity is proportional to the driving speed of the vibration element 2, that is, the driving amplitude. In the above configuration, since the reference voltage input to the vibration control circuit 10 is proportional to the power supply voltage 1, the drive amplitude of the vibration element 2 is controlled to be proportional to the power supply voltage 1. Therefore, when the angular velocity is input to the angular velocity sensor, the signal input from the detection electrode 5 to the detection circuit 8 according to the angular velocity is proportional to the power supply voltage 1, but the gain of the detection circuit 8 is determined by the input resistance and the feedback resistance of the operational amplifier. Is substantially constant without being proportional to the power supply voltage 1.
[0005]
[Problems to be solved by the invention]
However, in the above-described conventional configuration, for example, in a brake system in which the power supply voltage 1 of the angular velocity sensor is supplied from the battery of the vehicle, for example, at the moment when the headlight of the vehicle also supplied with the power supply voltage 1 from the battery is turned on. Since the battery voltage temporarily decreases, the power supply voltage 1 supplied to the angular velocity sensor also instantaneously decreases, and the output signal of the angular velocity sensor becomes unstable.
[0006]
That is, the reference voltage of the vibration control circuit 10 decreases following the decrease of the power supply voltage 1, and the reduced reference voltage is subjected to vibration control again, so that the drive amplitude of the vibration element 2 decreases. At this time, the drive amplitude of the vibrating element 2 is temporarily made unstable in proportion to the power supply voltage 1 due to a delay in response time until the drive amplitude corresponding to the decrease in the reference voltage converges. If an angular velocity is input to the angular velocity sensor during this time, the sensitivity to the input angular velocity becomes unstable. For example, when performing A / D conversion of a sensor signal output using a microcomputer or the like in a brake system, the sensor signal is also supplied from a battery. In response to a decrease in the power supply voltage 1 of the microcomputer, ie, a decrease in the reference voltage for A / D conversion, an erroneous output level is read.
[0007]
An object of the present invention is to provide an angular velocity sensor capable of obtaining a stable output signal even when the power supply voltage 1 fluctuates, and an automobile using the same.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configurations.
[0009]
The invention according to claim 1 of the present invention connects a vibration element having at least a drive electrode, a monitor electrode, and a detection electrode, a drive circuit connected to the drive electrode of the vibration element, and a detection electrode of the vibration element. A detection circuit, a monitor circuit connected to a monitor electrode of the vibrating element, and a vibration control circuit between the monitor circuit and the drive circuit, wherein a reference voltage of the vibration control circuit is supplied to the drive circuit and the monitor circuit. With a configuration in which the gain of the detection circuit is proportional to the power supply voltage substantially independently of the power supply, the reference voltage of the vibration control circuit does not fluctuate even when the power supply voltage fluctuates. Since the drive amplitude of the sensor is set to be stable and the gain of the detection circuit is set to be proportional to the power supply voltage, the sensitivity of the sensor to the input angular velocity is totally smaller than the power supply voltage. Will be, it is possible to obtain an output signal of a stable angular velocity sensor.
[0010]
The invention according to claim 2 of the present invention has a configuration in which the reference voltage of the vibration control circuit is supplied from a band gap type reference voltage source circuit, and has the same operation as the invention according to claim 1.
[0011]
The invention according to claim 3 of the present invention is a configuration of a detection circuit including an operational amplifier using a MOS transistor resistor as an input resistor or a feedback resistor, and has the same operation as the invention according to claim 1.
[0012]
According to a fourth aspect of the present invention, there is provided an automobile including any one of the angular velocity sensors according to the first to third aspects in a brake system provided on a plurality of tires supporting a vehicle body, wherein a power supply is changed. In this case, a stable output signal of the angular velocity sensor can be obtained, and appropriate control corresponding to the angular velocity information detected by the angular velocity sensor can be performed.
[0013]
According to a fifth aspect of the present invention, there is provided an automobile having at least one of the angular velocity sensors according to the first to third aspects in an airbag system installed in at least one seat provided on a vehicle body. In addition, even when the power supply fluctuates, a stable output signal of the angular velocity sensor can be obtained, and appropriate control corresponding to the angular velocity information detected by the angular velocity sensor can be performed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a circuit diagram of an angular velocity sensor according to one embodiment of the present invention. 1 is a power supply voltage, 2 is a vibration element for detecting angular velocity, 3 is a drive electrode formed on the vibration element 2, 4 is a monitor electrode formed on the vibration element 2, and 5 is a detection electrode formed on the vibration element 2. 6 is a drive circuit connected to the drive electrode 3, 7 is a monitor circuit connected to the monitor electrode 4, 8 is a detection circuit connected to the detection electrode 5, and 9 is an output terminal of the angular velocity sensor connected to the detection circuit 8.
[0016]
Reference numeral 10 denotes a vibration control circuit interposed between the monitor circuit 7 and the drive circuit 6. A first voltage supply circuit 11 supplies a first reference voltage 32 substantially independent of the power supply voltage 1 to the vibration control circuit 10.
[0017]
Reference numeral 17 denotes a band gap type reference voltage source circuit, and FIG. 2 shows a circuit configuration thereof. The bandgap reference voltage source circuit 17 outputs a high-precision reference voltage of about 1.2 V which is excellent in temperature characteristics and substantially independent of the power supply voltage 1. Since the bandgap reference voltage source circuit 17 is well known, the description of the circuit configuration and operation is omitted here.
[0018]
Reference numeral 18 denotes an amplifier circuit, to which an output voltage of the bandgap reference voltage source circuit 17 is input. The amplification circuit 18 amplifies the input signal and supplies the vibration control circuit 10 with the first reference voltage 32 which is a voltage (for example, 2.5 V) near the midpoint between the power supply voltage 1 and the ground voltage.
[0019]
FIG. 3 shows an output waveform diagram of the angular velocity sensor when the power supply voltage 1 changes. The angular velocity sensor of the prior art generates a transient, whereas the angular velocity sensor of the present invention has a stable first reference voltage 32, which is the reference voltage of the vibration control circuit 10, even when the power supply voltage 1 decreases. Therefore, there is no delay in the response time until the drive amplitude converges. Therefore, the driving amplitude of the vibration element 2 is stable, and stable sensitivity to the input angular velocity can be obtained.
[0020]
Reference numeral 12 denotes an operational amplifier provided in the detection circuit 8 and includes an MOS transistor resistor 21 as an input resistor thereof, a first resistor 20 as a feedback resistor thereof, and a second reference voltage 33. The second reference voltage 33 is supplied from the second voltage supply circuit 13. The gate of the MOS transistor resistor 21 is connected to the ground potential, the source is connected to the inverting input terminal of the operational amplifier 12 and the first resistor 20, and the drain is the input terminal. The first resistor 20 is connected between the MOS transistor resistor 21 and the output terminal of the operational amplifier 12. The second reference voltage 33 is supplied to a non-inverting input terminal of the operational amplifier 12. Here, the MOS transistor resistance is used for the input resistance, but the same applies when the MOS transistor resistance is used for the feedback resistance.
[0021]
FIG. 4 shows a circuit diagram of an embodiment of the second voltage supply circuit 13. Reference numeral 14 denotes a voltage follower type buffer connecting the output terminal and the inverting input terminal, reference numeral 15 denotes a diode-connected MOS transistor, and reference numeral 16 denotes a constant current source. The midpoint potential of the power supply voltage 1 is input to the non-inverting input terminal of the buffer 14, and the voltage at the connection point between the MOS transistor 15 and the constant current source 16 is supplied to the second reference voltage 33.
[0022]
The time when the second reference voltage 33 and V ref2, the source voltage 1 V cc, is represented by the following formula the threshold voltage of the MOS transistor 15 as V t.
[0023]
(Equation 1)
Figure 2004053396
[0024]
If the MOS transistor resistance 21 is Rt , it is expressed by the following equation.
[0025]
(Equation 2)
Figure 2004053396
[0026]
Here, μ 0 is the channel surface mobility, C ox is the unit capacitance of the gate oxide film, W is the effective gate width of the transistor, L is the effective gate length of the transistor, V gs is the gate-source voltage of the transistor, V is t represents a threshold voltage.
[0027]
Since the source potential of the MOS transistor resistor 21 becomes the second reference voltage 33 due to the imaginary short-circuit of the operational amplifier 12,
[0028]
[Equation 3]
Figure 2004053396
[0029]
It becomes. Therefore, from (Equation 1) to (Equation 3),
[0030]
(Equation 4)
Figure 2004053396
[0031]
It becomes. Here, since μ 0 , C ox , W, and L are independent of the power supply voltage 1, the MOS transistor resistance 21 is inversely proportional to the power supply voltage 1.
[0032]
Further, when the gain of the operational amplifier 12 and A v, represented by the following formula a first resistor 20 as R fb.
[0033]
(Equation 5)
Figure 2004053396
[0034]
Therefore, from (Equation 4) and (Equation 5),
[0035]
(Equation 6)
Figure 2004053396
[0036]
Next, the gain A v of the operational amplifier 12 is proportional to the power supply voltage 1.
[0037]
Accordingly, since the gain of the detection circuit 8 is proportional to the power supply voltage 1, the sensitivity of the sensor to the input angular velocity is totally proportional to the power supply voltage 1, and A / D conversion of the sensor signal output is performed using a microcomputer or the like. Also in this case, the ratiometric characteristic of the sensor sensitivity is secured against a decrease in the power supply voltage 1, that is, a decrease in the reference voltage for A / D conversion, and reading of an incorrect output level can be avoided.
[0038]
FIG. 5 is a block diagram in which the angular velocity sensor is used in a brake system of an automobile. 22 is a vehicle body, 23 is a plurality of tires supporting the vehicle body 22, 24 is a brake system provided on the tire 23, 25 is a first microcomputer that controls the brake system 24, 26 is an angular velocity sensor that supplies a detection output to the microcomputer 25 And 27, a headlight provided on the vehicle body 22, and 28, a battery for supplying a power supply voltage 1 to the brake system 24, the angular velocity sensor 26, and the headlight 27. With this configuration, the brake system can appropriately control the angular velocity information detected by the angular velocity sensor that is stable even when the power supply voltage 1 fluctuates.
[0039]
FIG. 6 is a block diagram in which the angular velocity sensor is used in an airbag system of an automobile. 29 is at least one seat installed on the vehicle body, 30 is an airbag system installed near the seat 29, and 31 is a second microcomputer for controlling the airbag system 30. Power is supplied from a battery 28 to the airbag system 30, the angular velocity sensor 26, and the headlight 27. With this configuration, the airbag system can appropriately control the angular velocity information detected by the angular velocity sensor that is stable even when the power supply voltage 1 fluctuates.
[0040]
【The invention's effect】
As described above, according to the present invention, even when the power supply voltage supplied to the sensor fluctuates, the driving amplitude of the vibrating element can be stabilized, and a stable sensor signal output can be obtained. In particular, when driving a vibrating element having a large load capacity, in which the response time delay until the drive amplitude converges becomes large, the effect is remarkable.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of an angular velocity sensor according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing an example of a bandgap type reference voltage source circuit. FIGS. FIG. 4 is a circuit diagram showing an example of a second voltage supply circuit. FIG. 5 is a block diagram in which the angular velocity sensor is used in a brake system of an automobile. FIG. 7 is a circuit diagram showing an example of a conventional angular velocity sensor.
REFERENCE SIGNS LIST 1 power supply voltage 2 vibrating element 3 drive electrode 4 monitor electrode 5 detection electrode 6 drive circuit 7 monitor circuit 8 detection circuit 9 sensor output terminal 10 vibration control circuit 11 first voltage supply circuit 12 operational amplifier 13 second voltage supply circuit 14 Buffer 15 MOS transistor 16 Constant current source 17 Bandgap type reference voltage source circuit 18 Amplifying circuit 19 Reference voltage circuit 20 proportional to power supply voltage 20 First resistor 21 MOS transistor resistor 22 Body 23 Tire 24 Brake system 25 First microcomputer 26 Angular velocity sensor 27 Headlight 28 Battery 29 Seat 30 Airbag system 31 Second microcomputer

Claims (5)

少なくとも駆動電極、モニタ電極、検出電極とを有する振動素子と、この振動素子の駆動電極に接続した駆動回路と、前記振動素子の検出電極に接続した検出回路と、前記振動素子のモニタ電極に接続したモニタ回路と、前記モニタ回路と駆動回路の間に振動制御回路を備え、この振動制御回路の基準電圧を前記駆動回路とモニタ回路に供給する電圧電源とは実質的に独立して前記検出回路の利得が電源電圧に比例するようにした角速度センサ。A vibration element having at least a drive electrode, a monitor electrode, and a detection electrode; a drive circuit connected to the drive electrode of the vibration element; a detection circuit connected to the detection electrode of the vibration element; and a monitor circuit connected to the monitor electrode of the vibration element A monitor circuit, and a vibration control circuit provided between the monitor circuit and the drive circuit. A voltage power supply for supplying a reference voltage of the vibration control circuit to the drive circuit and the monitor circuit is substantially independent of the detection circuit. Angular velocity sensor whose gain is proportional to the power supply voltage. 振動制御回路の基準電圧をバンドギャップ型基準電圧源回路より供給した請求項１記載の角速度センサ。2. The angular velocity sensor according to claim 1, wherein the reference voltage of the vibration control circuit is supplied from a band gap type reference voltage source circuit. ＭＯＳトランジスタ抵抗を入力抵抗または帰還抵抗に用いた演算増幅器を備えた検出回路からなる請求項１に記載の角速度センサ。2. The angular velocity sensor according to claim 1, comprising a detection circuit including an operational amplifier using a MOS transistor resistance as an input resistance or a feedback resistance. 車体を支える複数のタイヤに設けたブレーキシステムにおいて請求項１〜３に記載の角速度センサのいずれか１つを備えた自動車。An automobile provided with any one of the angular velocity sensors according to any one of claims 1 to 3, in a brake system provided on a plurality of tires supporting a vehicle body. 車体に備えられた少なくとも１つの座席に設置されるエアバッグシステムにおいて請求項１〜３に記載の角速度センサのいずれか１つを備えた自動車。An automobile equipped with any one of the angular velocity sensors according to any one of claims 1 to 3, in an airbag system installed in at least one seat provided on a vehicle body.
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