JPH0581720U - Semiconductor sensor failure detection device - Google Patents
Semiconductor sensor failure detection deviceInfo
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- JPH0581720U JPH0581720U JP1877092U JP1877092U JPH0581720U JP H0581720 U JPH0581720 U JP H0581720U JP 1877092 U JP1877092 U JP 1877092U JP 1877092 U JP1877092 U JP 1877092U JP H0581720 U JPH0581720 U JP H0581720U
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- semiconductor sensor
- failure
- voltage
- failure detection
- resistor
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Abstract
(57)【要約】
【目的】 故障内容によらず、歪ゲージの短絡や断線を
確実に検出する。
【構成】 ブリッジ接続された歪ゲージＲ１〜Ｒ４から
なる半導体センサ１に、故障検出用抵抗ｒを並列接続
し、故障検出用抵抗ｒと半導体センサ１の並列接続回路
１２を定電流駆動して故障検出用抵抗ｒの両端にかかる
電圧（ｖ１−ｖ２）を検出し、この電圧があらかじめ設
定した一定範囲を外れたときに、半導体センサ１の故障
を報知することにより、１又は２以上の歪ゲージＲ１〜
Ｒ４が断線又は短絡したときに生ずる半導体センサ１の
合成抵抗の変化を、故障内容によらず故障検出用抵抗ｒ
の両端にかかる電圧（ｖ１−ｖ２）の変化をもって確実
に検出する。
(57) [Summary] [Purpose] Regardless of the nature of the failure, a strain gauge short circuit or disconnection can be reliably detected. [Construction] A failure detecting resistor r is connected in parallel to a semiconductor sensor 1 composed of strain gauges R1 to R4 connected in a bridge, and a failure is caused by driving a parallel connection circuit 12 of the failure detecting resistor r and the semiconductor sensor 1 with a constant current. One or two or more strain gauges are detected by detecting the voltage (v1-v2) applied to both ends of the detection resistor r and notifying the failure of the semiconductor sensor 1 when this voltage is out of a preset constant range. R1
The change in the combined resistance of the semiconductor sensor 1 that occurs when R4 is disconnected or short-circuited is determined by the failure detection resistance r regardless of the failure content.
The change of the voltage (v1-v2) applied to both ends of is surely detected.
Description
【０００１】[0001]
この考案は、故障内容によらず、歪ゲージの短絡や断線が確実に検出できるよ うにした半導体センサの故障検出装置。 This invention is a semiconductor sensor failure detection device that can reliably detect a short circuit or disconnection of a strain gauge regardless of the failure content.
【０００２】[0002]
車両衝突時にエアバッグを展開して乗員を保護するエアバッグ装置は、車両に 加わる衝撃の大きさを検出するため、図２に示したように、衝撃に比例する加速 度の変化を検出する半導体センサを用いている。半導体センサ１は、ピエゾ抵抗 効果により外力の大きさに応じて抵抗値が変化する４個の歪ゲージＲ１，Ｒ２， Ｒ３，Ｒ４を、互いに直列の歪ゲージＲ１とＲ２及びＲ３とＲ４を並列接続した もので、ブリッジ接続された歪ゲージＲ１〜Ｒ４に定電圧源２から一定電圧Ｖｃ を印加し、歪ゲージＲ１とＲ２の接続点Ｐ１２と歪ゲージＲ３とＲ４の接続点Ｐ ３４の電位差ΔＶから、加速度の大きさを検出する構成とされている。外力の作 用していないときの歪ゲージＲ１〜Ｒ４の抵抗値はいずれもＲであるが、加速度 を受けて対角位置の歪ゲージＲ１，Ｒ３の抵抗値が仮にＲ＋ΔＲに変化したとき に、残る対角位置の歪ゲージＲ２，Ｒ４の抵抗値はＲ−ΔＲに変化する。このた め、半導体センサ１自体の合成抵抗はＲに保たれたまま、接続点Ｐ１２，Ｐ３４ に抵抗変化ΔＲすなわち加速度の大きさに応じたΔＲＶｃ／Ｒなる電位差が生じ 、衝撃の大きさが判明する。 An airbag device that protects an occupant by deploying an airbag in the event of a vehicle collision detects the magnitude of the impact applied to the vehicle. Therefore, as shown in FIG. 2, a semiconductor that detects changes in acceleration proportional to the impact. It uses a sensor. The semiconductor sensor 1 includes four strain gauges R1, R2, R3 and R4 whose resistance values change according to the magnitude of an external force due to the piezoresistive effect, and strain gauges R1 and R2 and R3 and R4 which are connected in series to each other are connected in parallel. Then, a constant voltage Vc is applied from the constant voltage source 2 to the strain gauges R1 to R4 connected in a bridge, and the potential difference ΔV between the connection point P12 of the strain gauges R1 and R2 and the connection point P34 of the strain gauges R3 and R4 is calculated. , Is configured to detect the magnitude of acceleration. The resistance values of the strain gauges R1 to R4 when no external force is applied are all R, but when the resistance values of the strain gauges R1 and R3 at diagonal positions change to R + ΔR due to acceleration, The resistance values of the remaining strain gauges R2 and R4 at diagonal positions change to R-ΔR. Therefore, while the combined resistance of the semiconductor sensor 1 itself is kept at R, a resistance change ΔR, that is, a potential difference ΔRVc / R corresponding to the magnitude of acceleration occurs at the connection points P12 and P34, and the magnitude of impact is determined. To do.
【０００３】 ところで、こうした４個の歪ゲージＲ１〜Ｒ４をブリッジ接続した半導体セン サ１は、歪ゲージＲ１，Ｒ２，Ｒ３，Ｒ４が１個でも短絡したり或いは断線した りした場合に、加速度センサとしての役目がまったく果たせなくなるため、この 種の故障は特に厳重に監視する必要がある。そこで、従来は歪ゲージＲ１とＲ２ の接続点Ｐ１２及び歪ゲージＲ３とＲ４の接続点Ｐ３４にそれぞれ電圧監視用の ウインドウコンパレータ３，４を接続し、各接続点Ｐ１２，Ｐ３４の電圧をウイ ンドウコンパレータ３，４にそれぞれ設定した上下の基準電圧Ｖａ，Ｖｂと比較 し、仮に接続点Ｐ１２，Ｐ３４のいずれか一方でも上下の基準電圧Ｖａ，Ｖｂに 挟まれる一定の電圧範囲Ｖｂ〜Ｖａから逸脱したときに、故障報知回路５がラン プ或いはブザー等を動作させて故障発生を報知するよう構成してあった。By the way, the semiconductor sensor 1 in which the four strain gauges R1 to R4 are bridge-connected has an acceleration sensor when even one of the strain gauges R1, R2, R3 and R4 is short-circuited or disconnected. This kind of failure needs to be closely monitored, as it can no longer serve its purpose. Therefore, conventionally, voltage comparator window comparators 3 and 4 are connected to the connection point P12 of the strain gauges R1 and R2 and the connection point P34 of the strain gauges R3 and R4, respectively, and the voltages at the connection points P12 and P34 are connected to the window comparator. Compared with the upper and lower reference voltages Va and Vb set to 3 and 4, respectively, and if any one of the connection points P12 and P34 deviates from the constant voltage range Vb to Va sandwiched between the upper and lower reference voltages Va and Vb. In addition, the failure notification circuit 5 is configured to notify the occurrence of a failure by operating a lamp or a buzzer.
【０００４】[0004]
上記従来の半導体センサの故障検出装置６は、仮に歪ゲージＲ１だけが短絡し た場合は、接続点Ｐ１２の電圧がＶｃに跳ね上がることで、また歪ゲージＲ１だ けが断線した場合には、接続点Ｐ１２の電位が零に落ち込むことで、いずれもウ インドウコンパレータ３による異常検知が行われる。同様にまた、歪ゲージＲ２ だけが短絡した場合は、接続点Ｐ１２の電圧が零に落ち込むことで、また歪ゲー ジＲ２だけが断線した場合には、接続点Ｐ１２の電圧がＶｃに跳ね上がることで 、いずれもウインドウコンパレータ３による異常検知が可能である。さらにまた 、対角位置にある歪ゲージＲ１とＲ４或いはＲ２とＲ３が同時に短絡或いは断線 した場合も、同様にウインドウコンパレータ３と４による異常検知が行われる。 しかし、互いに直列の歪ゲージＲ１とＲ２又はＲ３とＲ４が同時に断線した場合 は、接続点Ｐ１２又はＰ３４の電位が不定と化すため、ウインドウコンパレータ ３，４による異常検知ができないことがあり、従って故障監視に万全を期すこと ができず、さらにまた互いに直列の歪ゲージＲ１とＲ２又はＲ３とＲ４が同時に 短絡した場合には、定電圧源２が短絡した歪ゲージＲ１とＲ２又はＲ３とＲ４を 介して直接接地されてしまうため、無負荷に近い状態で定電圧源２から電流が流 れ続ける結果、定電圧源２自体にも悪影響が及ぶといった課題を抱えていた。 In the conventional semiconductor sensor failure detection device 6 described above, if only the strain gauge R1 is short-circuited, the voltage at the connection point P12 jumps up to Vc, and if only the strain gauge R1 is disconnected, the connection point is broken. When the potential of P12 drops to zero, the window comparator 3 detects an abnormality in both cases. Similarly, when only the strain gauge R2 is short-circuited, the voltage at the connection point P12 drops to zero, and when only the strain gauge R2 is disconnected, the voltage at the connection point P12 jumps to Vc. In any case, the window comparator 3 can detect an abnormality. Furthermore, even when the strain gauges R1 and R4 or R2 and R3 in diagonal positions are short-circuited or disconnected at the same time, the window comparators 3 and 4 similarly detect an abnormality. However, if the strain gauges R1 and R2 or R3 and R4 in series are disconnected at the same time, the potential at the connection point P12 or P34 becomes indefinite, and the window comparators 3 and 4 may not be able to detect an abnormality, thus causing a failure. If the strain gauges R1 and R2 or R3 and R4 in series with each other are short-circuited at the same time, the constant voltage source 2 is short-circuited through the strain gauges R1 and R2 or R3 and R4. As a result, the constant voltage source 2 continues to flow current in a state of almost no load because it is directly grounded, and the constant voltage source 2 itself is adversely affected.
【０００５】[0005]
この考案は、上記課題を解決したものであり、ブリッジ接続された歪ゲージか らなる半導体センサと、この半導体センサに並列接続した故障検出用抵抗と、こ の故障検出用抵抗と前記半導体センサの並列接続回路を定電流駆動する定電流源 と、前記故障検出用抵抗の両端にかかる電圧を検出し、該電圧があらかじめ設定 した一定範囲を外れたときに、前記半導体センサの故障を報知する故障検出手段 とを具備することを第１の特徴とするものである。 This invention solves the above-mentioned problems, and includes a semiconductor sensor including a strain gauge connected in a bridge, a failure detection resistor connected in parallel to the semiconductor sensor, the failure detection resistor and the semiconductor sensor. A constant current source that drives a parallel connection circuit at a constant current, and a voltage that is applied to both ends of the failure detection resistor, and when the voltage is outside a preset range, a failure that notifies the failure of the semiconductor sensor. The first characteristic is to include a detecting means.
【０００６】 また、この考案は、前記定電流源を、前記並列接続回路を接地する接地抵抗と 、この接地抵抗と前記並列接続回路の接続点に反転入力端子が接続され、定電圧 源が非反転入力端子に接続され、出力端子に前記並列接続回路が接続された演算 増幅器から構成したことを第２の特徴としており、さらに前記故障検出手段を、 前記故障検出用抵抗の両端に接続した一対のボルテージフォロワと、これら一対 のボルテージフォロワの出力を差動増幅する差動増幅器と、この差動増幅器の出 力を前記一定の範囲を規定する上下の閾値を基準に比較分別するウインドウコン パレータと、このウインドウコンパレータの出力を受けて前記半導体センサの故 障を報知する警報回路から構成したことを第３の特徴とするものである。Further, the present invention is characterized in that the constant current source is connected to a grounding resistor for grounding the parallel connection circuit, an inverting input terminal is connected to a connection point of the grounding resistance and the parallel connection circuit, and a constant voltage source is not connected. The second feature is that the operational amplifier is connected to the inverting input terminal and the parallel connection circuit is connected to the output terminal, and the fault detecting means is further connected to both ends of the fault detecting resistor. Voltage follower, a differential amplifier that differentially amplifies the output of the pair of voltage followers, and a window comparator that separates and separates the output of this differential amplifier based on the upper and lower thresholds that define the certain range. A third feature is that it is composed of an alarm circuit which receives the output of the window comparator and notifies the failure of the semiconductor sensor.
【０００７】[0007]
この考案は、ブリッジ接続された歪ゲージからなる半導体センサに、故障検出 用抵抗を並列接続し、故障検出用抵抗と半導体センサの並列接続回路を定電流駆 動して故障検出用抵抗の両端にかかる電圧を検出し、この電圧があらかじめ設定 した一定範囲を外れたときに、半導体センサの故障を報知することにより、故障 内容によらず歪ゲージの短絡或いは断線を確実に検出する。 In this invention, a semiconductor sensor consisting of a strain gauge connected in a bridge is connected in parallel with a failure detection resistor, and a parallel connection circuit of the failure detection resistor and the semiconductor sensor is driven with a constant current to connect both ends of the failure detection resistor. By detecting such a voltage and notifying the failure of the semiconductor sensor when the voltage goes out of a predetermined range, it is possible to reliably detect a short circuit or disconnection of the strain gauge regardless of the failure content.
【０００８】[0008]
以下、この考案の実施例について、図１を参照して説明する。図１は、この考 案の半導体センサの故障検出装置の一実施例を示す回路構成図である。 An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a circuit configuration diagram showing an embodiment of a failure detection device for a semiconductor sensor according to the present invention.
【０００９】 図１に示す半導体センサの故障検出装置１１は、ブリッジ接続された歪ゲージ Ｒ１，Ｒ２，Ｒ３，Ｒ４からなる半導体センサ１に故障検出用抵抗ｒを並列接続 し、故障検出用抵抗ｒと半導体センサ１の並列接続回路１２を定電流駆動して故 障検出用抵抗ｒの両端にかかる電圧ｒＩを検出し、この電圧があらかじめ設定し た一定範囲を外れたときに、半導体センサ１の故障を報知する構成としてある。 故障検出用抵抗ｒと半導体センサ１の並列接続回路１２に定電流Ｉを供給する定 電流源１３は、並列接続回路１２を接地する接地抵抗Ｒ５と演算増幅器１４から 構成してある。演算増幅器１４は、反転入力端子に接地抵抗Ｒ５と並列接続回路 １２の接続点が接続され、非反転入力端子に定電圧源１５が接続される。さらに 、出力端子には並列接続回路１２が接続され、並列接続回路１２と接地抵抗Ｒ５ の接続点の電位は定電圧源１５の出力電圧Ｖｃに固定される。また、故障検出用 抵抗ｒの両端には、高入力インピーダンスバッファである一対のボルテージフォ ロワ１６，１７が接続してあり、これら一対のボルテージフォロワ１６，１７と 、その出力を差動増幅する差動増幅器１８、そして差動増幅器１８の出力を前記 一定の範囲を規定する上下の閾値を基準に比較分別するウインドウコンパレータ １９及びウインドウコンパレータ１９の出力を受けて半導体センサ１の故障を報 知する警報回路２０をもって、故障検出手段を構成してある。In a semiconductor sensor failure detection device 11 shown in FIG. 1, a failure detection resistor r is connected in parallel to a semiconductor sensor 1 composed of strain gauges R1, R2, R3, and R4 connected in a bridge. The parallel connection circuit 12 of the semiconductor sensor 1 and the semiconductor sensor 1 is driven at a constant current to detect the voltage rI applied to both ends of the failure detection resistor r, and when the voltage deviates from a preset constant range, the semiconductor sensor 1 It is configured to notify a failure. The constant current source 13 for supplying the constant current I to the parallel detecting circuit r of the failure detecting resistor r and the semiconductor sensor 1 is composed of a grounding resistor R5 for grounding the parallel connecting circuit 12 and an operational amplifier 14. The operational amplifier 14 has an inverting input terminal connected to the connection point of the ground resistor R5 and the parallel connection circuit 12, and a non-inverting input terminal connected to the constant voltage source 15. Further, the parallel connection circuit 12 is connected to the output terminal, and the potential at the connection point between the parallel connection circuit 12 and the ground resistance R5 is fixed to the output voltage Vc of the constant voltage source 15. Further, a pair of voltage followers 16 and 17 which are high input impedance buffers are connected to both ends of the failure detection resistor r, and the pair of voltage followers 16 and 17 and a difference for differentially amplifying the output thereof. A window comparator 19 for comparing and discriminating the outputs of the dynamic amplifier 18 and the differential amplifier 18 based on the upper and lower thresholds defining the constant range, and an alarm for receiving the output of the window comparator 19 and notifying the failure of the semiconductor sensor 1. The circuit 20 constitutes a failure detecting means.
【００１０】 ところで、ブリッジ接続された４個の歪ゲージＲ１〜Ｒ４からなる半導体セン サ１は、従来のように定電圧駆動せず、定電流により駆動される。すなわち、演 算増幅器１４の非反転入力端子には、抵抗Ｒａ，Ｒｂにより分割された一定電圧 ＶｃがコンデンサＣによりバックアップされた形で印加されており、反転入力端 子が非反転入力端子に仮想短絡されるため、並列接続回路１２と接地抵抗Ｒ５の 接続点は、電圧Ｖｃに固定される。このため、接地抵抗Ｒ５に流れ込む電流Ｉは Ｖｃ／Ｒ５（＝一定）であり、この電流Ｉが半導体センサ１と故障検出用抵抗ｒ によって分流されることになる。また、個々の歪ゲージＲ１〜Ｒ４の抵抗値Ｒを 合成して得られる半導体センサ１の合成抵抗値はＲであるが、ここでは故障検出 用抵抗ｒの抵抗値もＲに設定してあるため、半導体センサ１と故障検出用抵抗ｒ を流れる電流は、ともにＩ／２となる。By the way, the semiconductor sensor 1 including the four strain gauges R1 to R4 connected in a bridge is driven by a constant current instead of being driven by a constant voltage as in the conventional case. That is, a constant voltage Vc divided by the resistors Ra and Rb is applied to the non-inverting input terminal of the operational amplifier 14 in a form backed up by the capacitor C, and the inverting input terminal is virtually connected to the non-inverting input terminal. Since it is short-circuited, the connection point between the parallel connection circuit 12 and the ground resistance R5 is fixed to the voltage Vc. Therefore, the current I flowing into the ground resistance R5 is Vc / R5 (= constant), and this current I is shunted by the semiconductor sensor 1 and the failure detection resistance r. Further, the combined resistance value of the semiconductor sensor 1 obtained by combining the resistance values R of the individual strain gauges R1 to R4 is R, but since the resistance value of the failure detection resistor r is also set to R here. The currents flowing through the semiconductor sensor 1 and the failure detection resistor r 2 are both I / 2.
【００１１】 一方、故障検出用抵抗ｒの両端は、ボルテージフォロワ１６，１７を介して差 動増幅器１８に接続してあるが、ボルテージフォロワ１６，１７は、核となる演 算増幅器１６ａ，１７ａの出力端子を反転入力端子に直結してあるため、非反転 入力端子に印加された入力電圧は増幅度１で増幅され、そのまま出力電圧として 取り出される。演算増幅器１６ａ，１７ａの入力インピーダンスは非常に大きい ため、その非反転入力端子に電流Ｉの一部がリークすることはなく、従ってボル テージフォロワ１６，１７を接続したことで前述の定電流駆動の前提が崩れるこ とはない。一方のボルテージフォロワ１６の出力端子は、入力抵抗ｒ１を介して 差動増幅器１８の非反転入力端子に接続してあり、非反転入力端子は抵抗ｒ２を 介して接地してある。また、他方のボルテージフォロワ１７の出力端子は、入力 抵抗ｒ３を介して差動増幅器１８の反転入力端子に接続してあり、反転入力端子 には帰還抵抗ｒ４を介して出力端子が接続してある。差動増幅器１８の非反転入 力端子と反転入力端子は仮想短絡されているため、両入力端子の印加電圧は等し く、このため ｒ２ｖ１／（ｒ１＋ｒ２）＝（ｒ３ｖ３＋ｒ４ｖ２）／（ｒ３＋ｒ４） が成立する。そこで、ｒ１＝ｒ３＝Ｒｓ，ｒ２＝ｒ４＝Ｒｆなる条件を設定する ことで、 ｖ３＝（ｖ１−ｖ２）Ｒｓ／Ｒｆ となる。すなわち、故障検出用抵抗ｒの両端にかかる電圧ｒＩ（＝ｖ１−ｖ２） は、差動増幅器１８においてゲインＲｓ／Ｒｆで増幅されることになる。On the other hand, both ends of the failure detection resistor r are connected to a differential amplifier 18 via voltage followers 16 and 17, but the voltage followers 16 and 17 are the cores of the operational amplifiers 16a and 17a. Since the output terminal is directly connected to the inverting input terminal, the input voltage applied to the non-inverting input terminal is amplified by the amplification factor of 1 and taken out as it is as the output voltage. Since the input impedances of the operational amplifiers 16a and 17a are very large, part of the current I does not leak to their non-inverting input terminals. Therefore, by connecting the voltage followers 16 and 17, the constant current drive described above can be achieved. The premise is not broken. The output terminal of one voltage follower 16 is connected to the non-inverting input terminal of the differential amplifier 18 via the input resistor r1, and the non-inverting input terminal is grounded via the resistor r2. The output terminal of the other voltage follower 17 is connected to the inverting input terminal of the differential amplifier 18 via the input resistor r3, and the inverting input terminal is connected to the output terminal via the feedback resistor r4. .. Since the non-inverting input terminal and the inverting input terminal of the differential amplifier 18 are virtually short-circuited, the voltages applied to both input terminals are not equal, and therefore r2v1 / (r1 + r2) = (r3v3 + r4v2) / (r3 + r4) holds. To do. Therefore, by setting the condition that r1 = r3 = Rs and r2 = r4 = Rf, v3 = (v1-v2) Rs / Rf. That is, the voltage rI (= v1-v2) applied to both ends of the failure detection resistor r is amplified by the gain Rs / Rf in the differential amplifier 18.
【００１２】 差動増幅器１８の出力電圧ｖ３は、一対の電圧比較器１９ａ，１９ｂを並列接 続したウインドウコンパレータ１９に供給され、上下の閾値Ｅａ，Ｅｂに挟まれ た領域にあるかどうかが判定される。上限検知用の電圧比較器１９ａが比較基準 とする閾値Ｅａは、抵抗ｒ５，ｒ６により電源電圧を分割して与えられ、また下 限検知用の電圧比較器１９ｂが比較基準とする閾値Ｅｂは、電源電圧を抵抗ｒ７ ，ｒ８により分割して与えられる。ただし、閾値Ｅａ，Ｅｂについては、 Ｅｂ（ ０．４５ｒＩＲｓ／Ｒｆ）＜Ｅａ（ ０．５５ｒＩＲｓ／Ｒｆ） なる関係が設定される。このため、差動増幅器１８の出力ｖ３が上下の閾値Ｅａ とＥｂの間に挟まれている場合、すなわち Ｅｂ＜ｖ３＜Ｅａ であれば、電圧比較器の出力１９ａ，１９ｂの出力はともにハイレベルである。 ウインドウコンパレータ１９に続く警報回路２０は、プルアップ抵抗ｒ９とシュ ミットトリガ回路２０ａ及び警報ランプ２０ｂから構成され、電圧比較器１９ａ ，１９ｂの出力端子はプルアップ抵抗ｒ９により直流電源に吊り上げられた状態 でシュミットトリガ回路２０ａの入力端子に接続される。このため、電圧比較器 １９ａ，１９ｂの出力がともにハイレベルであるときは、シュミットトリガ回路 ２０ａの出力もハイレベルとなり、シュミットトリガ回路２０ａと直流電源の間 に接続された警報ランプ２０ａは、消灯して異常がないことを示している。The output voltage v3 of the differential amplifier 18 is supplied to a window comparator 19 in which a pair of voltage comparators 19a and 19b are connected in parallel, and it is determined whether or not it is in a region between upper and lower threshold values Ea and Eb. To be done. The threshold Ea used as the comparison reference by the upper limit detection voltage comparator 19a is given by dividing the power supply voltage by the resistors r5 and r6, and the threshold Eb used as the comparison reference by the lower limit detection voltage comparator 19b is The power supply voltage is given by being divided by resistors r7 and r8. However, for the threshold values Ea and Eb, the relationship of Eb (0.45rIRs / Rf) <Ea (0.55rIRs / Rf) is set. Therefore, if the output v3 of the differential amplifier 18 is sandwiched between the upper and lower thresholds Ea and Eb, that is, if Eb <v3 <Ea, the outputs of the voltage comparator outputs 19a and 19b are both high level. Is. The alarm circuit 20 following the window comparator 19 is composed of a pull-up resistor r9, a Schmitt trigger circuit 20a and an alarm lamp 20b. The output terminals of the voltage comparators 19a and 19b are suspended by the DC power supply by the pull-up resistor r9. It is connected to the input terminal of the Schmitt trigger circuit 20a. Therefore, when the outputs of the voltage comparators 19a and 19b are both at the high level, the output of the Schmitt trigger circuit 20a also goes to the high level, and the alarm lamp 20a connected between the Schmitt trigger circuit 20a and the DC power source is turned off. It shows that there is no abnormality.
【００１３】 ここで、仮に歪ゲージＲ１〜Ｒ２のいずれか１個が短絡した場合、半導体セン サ１の合成抵抗は２Ｒ／３に低下し、故障検出用抵抗ｒに流れる電流は正常時の Ｉ／２から２Ｉ／５に低下する。このため、ウインドウコンパレータ１９内の下 限検知用の電圧比較器１９ｂの出力がロウレベルに反転し、シュミットトリガ回 路２０ａの出力端子もロウレベルに切り替わる。その結果、警報ランプ２０ｂに 電源電流が流れ、警報ランプ２０ｂが点灯することで故障発生が警告される。ま た、歪ゲージＲ１〜Ｒ４のいずれか１個が断線した場合は、半導体センサ１の合 成抵抗は２Ｒに増大し、故障検出用抵抗ｒに流れる電流は正常時のＩ／２から２ Ｉ／３に増大する。このため、ウインドウコンパレータ１９内の上限検知用の電 圧比較器１９ａの出力がロウレベルに反転し、シュミットトリガ回路２０ａの出 力端子もロウレベルに切り替わる。その結果、警報ランプ２０ｂに電源電流が流 れ、点灯した警報ランプ２０ｂにより故障発生が警告される。Here, if any one of the strain gauges R1 to R2 is short-circuited, the combined resistance of the semiconductor sensor 1 decreases to 2R / 3, and the current flowing through the failure detection resistance r is I / 2 to 2I / 5. Therefore, the output of the voltage comparator 19b for detecting the lower limit in the window comparator 19 is inverted to the low level, and the output terminal of the Schmitt trigger circuit 20a is also switched to the low level. As a result, a power supply current flows through the alarm lamp 20b, and the alarm lamp 20b is turned on to warn that a failure has occurred. Further, when any one of the strain gauges R1 to R4 is disconnected, the synthetic resistance of the semiconductor sensor 1 increases to 2R, and the current flowing through the failure detection resistance r is from I / 2 to 2I in the normal state. Increase to / 3. Therefore, the output of the voltage comparator 19a for detecting the upper limit in the window comparator 19 is inverted to the low level, and the output terminal of the Schmitt trigger circuit 20a is also switched to the low level. As a result, a power supply current flows through the alarm lamp 20b, and the lit alarm lamp 20b warns that a failure has occurred.
【００１４】 さらに、仮に歪ゲージＲ１とＲ２或いはＲ２とＲ３がともに短絡した場合、半 導体センサ１の合成抵抗は零となるため、故障検出用抵抗ｒには電流が流れず、 ウインドウコンパレータ１９内の下限検知用の電圧比較器１９ｂの出力がロウレ ベルに反転する。その結果、シュミットトリガ回路２０ａの出力端子もロウレベ ルに切り替わり、警報ランプ２０ｂが点灯して故障発生が警告される。また、歪 ゲージＲ１とＲ２又はＲ３とＲ４がともに断線した場合、半導体センサ１の合成 抵抗は２Ｒに増大する。その結果、故障検出用抵抗ｒに流れる電流は、正常時の Ｉ／２から２Ｉ／３に増大し、前記と同様、点灯した警報ランプ２０ａにより故 障発生が警告される。Further, if the strain gauges R1 and R2 or R2 and R3 are short-circuited together, the combined resistance of the semiconductor sensor 1 becomes zero, so that no current flows through the failure detection resistance r, and the inside of the window comparator 19 is closed. The output of the voltage comparator 19b for detecting the lower limit of is inverted to low level. As a result, the output terminal of the Schmitt trigger circuit 20a is also switched to the low level, the alarm lamp 20b is turned on, and the occurrence of a failure is warned. When the strain gauges R1 and R2 or R3 and R4 are both disconnected, the combined resistance of the semiconductor sensor 1 increases to 2R. As a result, the current flowing through the failure detecting resistor r increases from I / 2 in the normal state to 2I / 3, and similarly to the above, the lit alarm lamp 20a warns the occurrence of the failure.
【００１５】 さらにまた、対角位置の歪ゲージＲ１とＲ４（又はＲ２とＲ３）がともに短絡 した場合は、半導体センサ１の合成抵抗はＲ／２に低下する。このため、故障検 出用抵抗ｒに流れる電流は、正常時のＩ／２からＩ／３に低下する。その結果、 ウインドウコンパレータ１９内の下限検知用の電圧比較器１９ａの出力がロウレ ベルに反転し、点灯した警報ランプ２０ａにより故障発生が警告される。また、 対角位置の歪ゲージＲ１とＲ４又はＲ２とＲ３がともに断線した場合は、半導体 センサ１の合成抵抗は無限大となり、そこに電流は流れなくなる。このため、故 障検出用抵抗ｒに流れる電流は正常時のＩ／２からＩに増大し、ウインドウコン パレータ１９内の上限検知用の電圧比較器１９ａの出力がロウレベルに反転する ことで、警報ランプ２０ａが点灯する。Furthermore, when the strain gauges R1 and R4 (or R2 and R3) at the diagonal positions are both short-circuited, the combined resistance of the semiconductor sensor 1 decreases to R / 2. Therefore, the current flowing through the failure detection resistor r drops from I / 2 in the normal state to I / 3. As a result, the output of the voltage comparator 19a for detecting the lower limit in the window comparator 19 is inverted to a low level, and the lit alarm lamp 20a warns that a failure has occurred. If the strain gauges R1 and R4 or R2 and R3 in the diagonal position are both disconnected, the combined resistance of the semiconductor sensor 1 becomes infinite and no current flows there. For this reason, the current flowing through the failure detection resistor r increases from I / 2 in the normal state to I, and the output of the upper limit detection voltage comparator 19a in the window comparator 19 is inverted to a low level to generate an alarm. The lamp 20a lights up.
【００１６】 このように、半導体センサの故障検出装置１１は、ブリッジ接続された歪ゲー ジＲ１〜Ｒ４からなる半導体センサ１の合成抵抗がセンサ入力に拘わらず一定で あり、しかも故障検出用抵抗ｒと半導体センサ１の並列接続回路１２には常に一 定の電流Ｉが供給されるため、１又は２以上の歪ゲージＲ１〜Ｒ４が断線又は短 絡したときに生ずる半導体センサ１の合成抵抗の変化を、故障検出用抵抗ｒを流 れる電流の変化、すなわち故障検出用抵抗ｒの両端にかかる電圧（ｖ１−ｖ２） の変化をもって確実に検出することができ、故障内容によって診断に迷いが生ず る従来の定電圧駆動方式と異なり、歪ゲージＲ１〜Ｒ４の短絡も断線も、故障箇 所の数に無関係に常に確実に検出することができ、これにより半導体センサ１の 故障が重大な事故に結び付きかねないエアバッグ装置等に適用することで、事故 発生に至る危険な芽を早期に排除することができる。As described above, in the semiconductor sensor failure detection device 11, the combined resistance of the semiconductor sensor 1 composed of the bridge-connected strain gauges R1 to R4 is constant regardless of the sensor input, and the failure detection resistance r. Since the constant current I is always supplied to the parallel connection circuit 12 of the semiconductor sensor 1 and the semiconductor sensor 1, the change in the combined resistance of the semiconductor sensor 1 caused when one or more strain gauges R1 to R4 are disconnected or short-circuited. Can be reliably detected by the change in the current flowing through the failure detection resistor r, that is, the change in the voltage (v1-v2) applied to both ends of the failure detection resistor r. Unlike the conventional constant voltage driving method, the strain gauges R1 to R4 can always detect the short circuit and the disconnection without fail regardless of the number of failure points. By applying it to an airbag device that may lead to a serious accident, dangerous buds leading to an accident can be eliminated at an early stage.
【００１７】 また、定電流源１３に用いた演算増幅器１４は、反転入力端子と非反転入力端 子が仮想短絡状態にあるため、並列接続回路１２とその接地抵抗Ｒ５の接続点を 、非反転入力端子に接続した定電圧源１５と同電圧Ｖｃに保つことができ、これ により故障検出用抵抗ｒと半導体センサ１の並列接続回路１２に流れる電流Ｉを 、定電圧源１５の電圧Ｖｃを接地抵抗Ｒ５の抵抗値で除して得られる電流値Ｖｃ ／Ｒ５に固定することができ、並列接続回路１２を安定した電流で定電流駆動す ることができる。Further, since the inverting input terminal and the non-inverting input terminal of the operational amplifier 14 used for the constant current source 13 are in a virtual short circuit state, the connection point of the parallel connection circuit 12 and its ground resistance R5 is non-inverting. It is possible to keep the same voltage Vc as the constant voltage source 15 connected to the input terminal, whereby the current I flowing in the parallel connection circuit 12 of the failure detection resistor r and the semiconductor sensor 1 and the voltage Vc of the constant voltage source 15 are grounded. The current value Vc / R5 obtained by dividing by the resistance value of the resistor R5 can be fixed, and the parallel connection circuit 12 can be driven at a constant current with a stable current.
【００１８】 さらにまた、故障検出用抵抗ｒの両端に高入力インピーダンスバッファとして ボルテージフォロワ１６，１７が接続してあるため、電流漏洩はほぼ完全に無視 することができ、定電流駆動方式を採用する上で重要な鍵となる故障検出用抵抗 ｒと半導体センサ１の並列接続回路１２からの漏洩電流は一切案ずる必要がなく 、さらに一対のボルテージフォロワ１６，１７の出力を差動増幅器１８により差 動増幅した上でウインドウコンパレータ１９にて比較分別するため、ウインドウ コンパレータ１９における分別精度はきわめて高く、従って故障検出用抵抗ｒを 流れる電流の変化を、故障検出用抵抗ｒの両端にかかる電圧の変化として、正確 かつ確実に検出することができる。Furthermore, since the voltage followers 16 and 17 are connected as high input impedance buffers to both ends of the failure detection resistor r, current leakage can be almost completely ignored, and a constant current drive system is adopted. It is not necessary to consider the leakage current from the parallel connection circuit 12 of the failure detection resistor r and the semiconductor sensor 1, which is an important key above, and the output of the pair of voltage followers 16 and 17 is driven by the differential amplifier 18. Since the window comparator 19 amplifies and then performs comparison and classification, the classification accuracy in the window comparator 19 is extremely high. Therefore, the change in the current flowing through the failure detection resistor r is regarded as the change in the voltage applied across the failure detection resistor r. It can be detected accurately and surely.
【００１９】[0019]
以上説明したように、この考案は、ブリッジ接続された歪ゲージからなる半導 体センサに、故障検出用抵抗を並列接続し、故障検出用抵抗と半導体センサの並 列接続回路を定電流駆動して故障検出用抵抗の両端にかかる電圧を検出し、この 電圧があらかじめ設定した一定範囲を外れたときに、半導体センサの故障を報知 する構成としたから、ブリッジ接続された歪ゲージからなる半導体センサの合成 抵抗がセンサ入力に拘わらず一定であり、しかも故障検出用抵抗と半導体センサ の並列接続回路には常に一定の電流が供給されるため、１又は２以上の歪ゲージ が断線又は短絡したときに生ずる半導体センサの合成抵抗の変化を、故障検出用 抵抗を流れる電流の変化、すなわち故障検出用抵抗の両端にかかる電圧の変化を もって確実に検出することができ、故障内容によって診断に迷いが生ずる従来の 定電圧駆動方式と異なり、歪ゲージの短絡であろうが断線であろうが、また故障 箇所が１箇所であろうが複数であろうが、常に確実に検出することができ、これ により半導体センサの故障が重大な事故に結び付きかねない装置類に適用するこ とで、事故発生に至る危険な芽を早期に排除することができる等の優れた効果を 奏する。 As described above, the present invention has a fault detection resistor connected in parallel to a semiconductor sensor composed of bridge-connected strain gauges, and a parallel connection circuit of the fault detection resistor and the semiconductor sensor is driven by a constant current. The voltage applied to both ends of the failure detection resistor is detected, and when the voltage goes out of a preset fixed range, a failure of the semiconductor sensor is notified.Therefore, a semiconductor sensor consisting of a bridge-connected strain gauge is used. The combined resistance is constant regardless of the sensor input, and a constant current is always supplied to the parallel connection circuit of the failure detection resistance and the semiconductor sensor. Therefore, when one or more strain gauges are disconnected or short-circuited. The change in the combined resistance of the semiconductor sensor caused by the change in the current is surely detected by the change in the current flowing through the failure detection resistor, that is, the change in the voltage across the failure detection resistor. Different from the conventional constant voltage drive system in which the diagnosis is unclear depending on the type of failure, there may be a short circuit or disconnection of the strain gauge, and there may be one failure point or multiple failures. However, by applying it to devices where failure of a semiconductor sensor may lead to a serious accident, dangerous buds leading to an accident can be eliminated at an early stage, etc. The excellent effect of.
【００２０】 また、この考案は、定電流源を、並列接続回路を接地する接地抵抗と、この接 地抵抗と前記並列接続回路の接続点に反転入力端子が接続され、定電圧源が非反 転入力端子に接続され、出力端子に前記並列接続回路が接続された演算増幅器か ら構成したことにより、ゲインの大きな演算増幅器では反転入力端子と非反転入 力端子が仮想短絡状態にあるため、並列接続抵抗とその接地抵抗の接続点を、非 反転入力端子に接続した定電圧源と同電圧に保つことができ、これにより故障検 出用抵抗と半導体センサの並列接続回路を流れる電流を、定電圧源の電圧を接地 抵抗の抵抗値で除算して得られる電流値に固定することができ、並列接続回路を 安定した電流で定電流駆動することができる等の効果を奏する。Further, according to the invention, a constant current source is connected to a grounding resistance for grounding a parallel connection circuit, an inverting input terminal is connected to a connection point of the ground resistance and the parallel connection circuit, and the constant voltage source is not inverted. Since it is composed of an operational amplifier connected to the input terminal and the parallel connection circuit to the output terminal, the inverting input terminal and the non-inverting input terminal are in a virtual short-circuit state in an operational amplifier with a large gain. The connection point between the parallel connection resistance and its ground resistance can be maintained at the same voltage as the constant voltage source connected to the non-inverting input terminal, which allows the current flowing in the parallel connection circuit between the failure detection resistance and the semiconductor sensor to be It is possible to fix the current value obtained by dividing the voltage of the constant voltage source by the resistance value of the ground resistance, and to drive the parallel connection circuit with a constant current at a constant current.
【００２１】 さらにまた、この考案は、故障検出手段を、故障検出用抵抗の両端に接続した 一対のボルテージフォロワと、これら一対のボルテージフォロワの出力を差動増 幅する差動増幅器と、この差動増幅器の出力を前記一定の範囲を規定する上下の 閾値を基準に比較分別するウインドウコンパレータと、このウインドウコンパレ ータの出力を受けて半導体センサの故障を報知する警報回路から構成したので、 定電流駆動方式を採用する上で重要な鍵となる故障検出用抵抗と半導体センサの 並列接続回路からの漏洩電流が故障検出精度に与える影響に懸念が及ぶとも、故 障検出用抵抗の両端に高入力インピーダンスバッファとしてボルテージフォロワ が接続してあるため、電流漏洩はほぼ完全に無視することができ、故障検出精度 にはなんらの障害ともならず、さらに一対のボルテージフォロワの出力を差動増 幅器により差動増幅した上でウインドウコンパレータにて比較分別するため、ウ インドウコンパレータにおける分別精度はきわめて高く、従って故障検出用抵抗 を流れる電流の変化を、故障検出用抵抗の両端にかかる電圧の変化として、正確 かつ確実に検出することができる等の効果を奏する。[0021] Furthermore, the present invention has a pair of voltage followers in which the failure detecting means is connected to both ends of the failure detecting resistor, a differential amplifier which differentially increases the outputs of the pair of voltage followers, and a difference between the pair of voltage followers. It consists of a window comparator that compares and separates the output of the dynamic amplifier based on the upper and lower thresholds that define the fixed range, and an alarm circuit that receives the output of this window comparator and notifies the failure of the semiconductor sensor. There is concern about the influence of leakage current from the parallel connection circuit of the semiconductor sensor and the fault detection resistor, which is an important key in adopting the current drive method, on the fault detection accuracy. Since a voltage follower is connected as an input impedance buffer, current leakage can be almost completely ignored, and fault detection accuracy is improved. Does not cause any trouble, and the outputs of the pair of voltage followers are differentially amplified by the differential amplifier and then compared and sorted by the window comparator, so the sorting accuracy in the window comparator is extremely high, and therefore the fault detection is performed. This has the effect of being able to accurately and reliably detect a change in the current flowing through the application resistance as a change in the voltage applied across the failure detection resistance.
【図１】この考案の半導体センサの故障検出装置の一実
施例を示す回路構成図である。FIG. 1 is a circuit configuration diagram showing an embodiment of a semiconductor sensor failure detection device of the present invention.
【図２】従来の半導体センサの故障検出装置の一例を示
す回路構成図である。FIG. 2 is a circuit configuration diagram showing an example of a conventional semiconductor sensor failure detection device.
Ｒ１〜Ｒ４ 歪ゲージ ｒ 故障検出用抵抗 １１ 半導体センサの故障検出装置 １２ 並列接続回路 １３ 定電流源 １６，１７ 故障検出手段（ボルテージフォロワ） １８ 故障検出手段（差動増幅器） １９ 故障検出手段（ウインドウコンパレータ） ２０ 故障検出手段（警報回路） R1 to R4 Strain gauge r Failure detection resistor 11 Semiconductor sensor failure detection device 12 Parallel connection circuit 13 Constant current source 16 and 17 Failure detection means (voltage follower) 18 Failure detection means (differential amplifier) 19 Failure detection means (window) Comparator) 20 Failure detection means (alarm circuit)
Claims (3)
導体センサと、この半導体センサに並列接続した故障検
出用抵抗と、この故障検出用抵抗と前記半導体センサの
並列接続回路を定電流駆動する定電流源と、前記故障検
出用抵抗の両端にかかる電圧を検出し、該電圧があらか
じめ設定した一定範囲を外れたときに、前記半導体セン
サの故障を報知する故障検出手段とを具備することを特
徴とする半導体センサの故障検出装置。1. A semiconductor sensor comprising a strain gauge connected in a bridge, a fault detection resistor connected in parallel to the semiconductor sensor, and a constant current for driving a parallel connection circuit of the fault detection resistor and the semiconductor sensor with a constant current. And a failure detecting means for detecting a voltage applied to both ends of the failure detecting resistor and notifying a failure of the semiconductor sensor when the voltage is out of a preset constant range. Semiconductor sensor failure detection device.
地する接地抵抗と、この接地抵抗と前記並列接続回路の
接続点に反転入力端子が接続され、定電圧源が非反転入
力端子に接続され、出力端子に前記並列接続回路が接続
された演算増幅器からなることを特徴とする請求項１記
載の半導体センサの故障検出装置。2. The constant current source has a grounding resistance for grounding the parallel connection circuit, an inverting input terminal connected to a connection point between the grounding resistance and the parallel connection circuit, and a constant voltage source connected to a non-inverting input terminal. 2. The failure detection device for a semiconductor sensor according to claim 1, further comprising an operational amplifier connected to the output terminal and connected in parallel to the output terminal.
抗の両端に接続した一対のボルテージフォロワと、これ
ら一対のボルテージフォロワの出力を差動増幅する差動
増幅器と、この差動増幅器の出力を前記一定の範囲を規
定する上下の閾値を基準に比較分別するウインドウコン
パレータと、このウインドウコンパレータの出力を受け
て前記半導体センサの故障を報知する警報回路からなる
ことを特徴とする請求項１記載の半導体センサの故障検
出装置。3. The fault detecting means includes a pair of voltage followers connected to both ends of the fault detecting resistor, a differential amplifier for differentially amplifying outputs of the pair of voltage followers, and an output of the differential amplifier. 2. A window comparator for comparing and discriminating between the above and below based on upper and lower threshold values defining the certain range, and an alarm circuit for receiving an output of the window comparator and notifying a failure of the semiconductor sensor. Semiconductor sensor failure detection device.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1877092U JP2560811Y2 (en) | 1992-03-31 | 1992-03-31 | Failure detection device for semiconductor sensor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1877092U JP2560811Y2 (en) | 1992-03-31 | 1992-03-31 | Failure detection device for semiconductor sensor |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0581720U true JPH0581720U (en) | 1993-11-05 |
| JP2560811Y2 JP2560811Y2 (en) | 1998-01-26 |
Family
ID=11980872
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1877092U Expired - Lifetime JP2560811Y2 (en) | 1992-03-31 | 1992-03-31 | Failure detection device for semiconductor sensor |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2560811Y2 (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001183165A (en) * | 1999-10-13 | 2001-07-06 | Denso Corp | Sensor abnormality detecting circuit and physical quantity detecting device |
| JP2007139667A (en) * | 2005-11-21 | 2007-06-07 | Fujitsu Ltd | Sensor detecting device and sensor |
| JP2012047636A (en) * | 2010-08-27 | 2012-03-08 | Nitto Seiko Co Ltd | Disconnection detection apparatus for bridge sensor |
| JP2013217756A (en) * | 2012-04-09 | 2013-10-24 | Hitachi Ltd | Displacement measuring sensor node, and displacement amount measuring method by displacement measuring sensor node |
| WO2014069193A1 (en) * | 2012-11-02 | 2014-05-08 | 日立オートモティブシステムズ株式会社 | Thermal flow meter |
-
1992
- 1992-03-31 JP JP1877092U patent/JP2560811Y2/en not_active Expired - Lifetime
Cited By (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001183165A (en) * | 1999-10-13 | 2001-07-06 | Denso Corp | Sensor abnormality detecting circuit and physical quantity detecting device |
| JP4617545B2 (en) * | 1999-10-13 | 2011-01-26 | 株式会社デンソー | Sensor abnormality detection circuit and physical quantity detection device |
| JP2007139667A (en) * | 2005-11-21 | 2007-06-07 | Fujitsu Ltd | Sensor detecting device and sensor |
| EP1795903A2 (en) | 2005-11-21 | 2007-06-13 | Fujitsu Ltd. | Apparatus for detecting the failure of a sensor |
| US7271595B2 (en) | 2005-11-21 | 2007-09-18 | Fujitsu Limited | Sensor detection apparatus and sensor |
| JP2012047636A (en) * | 2010-08-27 | 2012-03-08 | Nitto Seiko Co Ltd | Disconnection detection apparatus for bridge sensor |
| JP2013217756A (en) * | 2012-04-09 | 2013-10-24 | Hitachi Ltd | Displacement measuring sensor node, and displacement amount measuring method by displacement measuring sensor node |
| WO2014069193A1 (en) * | 2012-11-02 | 2014-05-08 | 日立オートモティブシステムズ株式会社 | Thermal flow meter |
| JP2014092414A (en) * | 2012-11-02 | 2014-05-19 | Hitachi Automotive Systems Ltd | Thermal-type flowmeter |
| US10508942B2 (en) | 2012-11-02 | 2019-12-17 | Hitachi Automotive Systems, Ltd. | Thermal flow meter |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2560811Y2 (en) | 1998-01-26 |
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