JP2532793Y2 - Bridge type sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention aims at avoiding a decrease in reliability due to disconnection in a sensor having a bridge configuration, and connects a first series bridge element and a second series bridge element to a power supply and a ground. In a bridge-type sensor that is connected in parallel between them and generates first and second outputs from an intermediate connection point of each series bridge element, each series bridge element is configured to be connected to a power supply and ground by independent wiring. In addition, each series bridge element is connected to the power supply and the earth by independent wiring, and the same potential side ends of each series bridge element are directly connected by the wiring in the bridge, respectively. The practicality is improved by inserting a small resistor into the wiring in the bridge that connects.

[Industrial applications]

The present invention relates to a bridge type sensor having improved reliability against disconnection.

[Conventional technology]

There are various types of sensors for converting a physical quantity into an electrical quantity, but in many cases, a sensor having a bridge configuration is used in terms of stability against temperature.

As shown in FIG. 2, the bridge type sensor has a first series bridge element Ra, Rb and a second series bridge element Rc, Rd connected in parallel between a power supply Vcc and a ground GND. First and second outputs A1 and A2 are generated from the intermediate connection point. Since the outputs A1 and A2 of the sensor 1 are floating above the reference level (GND), it is necessary to obtain the difference (A1-A2) between the two by the differential amplifier 2 in order to extract the original signal.

The bridge type sensor 1 does not function properly if even one of the elements Ra to Rd is damaged (open or short).
This is monitored by the window comparator 3. That is, when one of the bridge elements is shorted or opened, one of the outputs A1 and A2 becomes Vcc or GND, so the differential amplifier 2
Output is abnormally large and conversely small. Therefore, the window comparator 3 sets two thresholds, large and small, which can be determined to be normal, and outputs a diagnosis output indicating normal if the differential output is within the range and abnormal if the differential output is out of the range.

[Problems to be solved by the invention]

However, even if the bridge elements Ra to Rd are normal, Vcc
Or, if the wiring (generally a bonding wire) connected to GND is broken, a defect occurs in which the sensor output looks normal but does not actually function as a sensor. In other words, when the Vcc side is disconnected, both A1 and A2 are set to GND.
Both 1 and A2 become Vcc, and are included in the normal range as the differential output (A1-A2). However, in this case, even if the value of the bridge element changes, the output does not change, so that the function as a sensor is completely lost.

The present invention is intended to improve the reliability against such disconnection.

[Means for solving the problem]

The present invention provides a bridge type sensor in which a first series bridge element and a second series bridge element are connected in parallel between a power supply and a ground, and first and second outputs are generated from an intermediate connection point of each series bridge element. In the first, connecting each series bridge element to the power supply and the earth by independent wiring is the first.
The feature is.

The second feature is that each series bridge element is connected to the power supply and the ground by independent wiring, and the same potential side end of each series bridge element is directly connected to the inside of the bridge, respectively. A third feature is that a minute resistor is inserted into the wiring in the bridge connecting the same potential side ends.

[Action]

According to the first feature of the present invention, if one of the wires on the power supply side (similarly on the ground side) is broken, a large difference occurs in the output, so that a sensor abnormality can be detected. Therefore, it is possible to avoid a decrease in reliability of use without knowing the sensor abnormality.

According to the second feature of the present invention, even if one of the wires on the power supply side (same for the ground side) is broken, the connection is maintained by the other wire. Can be avoided, and the reliability is improved.

A third feature of the present invention is that the continuity check of each wiring, which is impossible by the second feature, is enabled by using a small resistor. Therefore, only a perfect non-defective product can be shipped by this wiring check, and even if one of the wires is broken during use, no sensor failure occurs, and the reliability is the highest.

〔Example〕

FIG. 1 is an equivalent circuit diagram showing a different embodiment of the present invention.
(1) to (3) are first to third methods corresponding to the first to third features, respectively.

In the first method, the first series bridge elements Ra and Rb are connected to a power supply Vcc via a wiring B11 and are connected to the ground GND via a wiring B12. The second series bridge element Rc, Rd is connected to another wiring B
Connect to power supply Vcc at 21 and ground GN at another wiring B22.
Connected to D.

As a specific structure, the bridge elements Ra to Rd are, for example, diffusion resistors formed on a semiconductor substrate. The connection between the elements is made by a diffusion layer or a conductive pattern of the substrate, and a pad P is used for connection between the substrate and the outside. Vcc and GND are outside the substrate, and the wirings B11, B12, B21, and B22 are all bonding wires.

The second method is the same as the first method, except that the ends of the first series bridge elements Rc, Rb and the second series bridge elements Rc, Rd on the same potential side are directly connected by the in-bridge wirings C1, C2, respectively. The Vcc side is connected by independent wirings B11 and B21, and the GND side is connected by independent wirings B12 and B22. Wiring C in bridge
1, C2 is a diffusion layer or a conductive pattern of the substrate, not a bonding wire.

In the third method, minute resistors r1 and r2 are inserted in the middle of the in-bridge wires C1 and C2. The value of the minute resistance r is as small as about 1/100 to 1 / 10,000 of the bridge element R, and is realized as a diffusion resistance of the substrate.

If all the wirings are normally connected, the outputs A1 and A2 of the first to third systems have exactly the same value.

On the other hand, if one wire, for example, B11 is disconnected, the first
In this method, the output A1 is fixed to GND. At this time, the output of the second method is the same as that in the normal mode, but the output of the third method changes by the voltage drop due to the minute resistance r1. This change is an offset, but there is no problem that the value cannot be ignored in measurement.
Even if it cannot be ignored, there is no problem because appropriate offset correction is a temporary one. The same applies to other wirings.

In the first and third methods, the disconnection check of the wiring B can be performed based on the presence or absence of conduction between the pads P at both ends. In the second method, since the disconnection of one of the wirings is masked by the other wiring by the wiring C in the bridge, it is not possible to determine the presence or absence of the disconnection of one of the wirings by the continuity check.

FIG. 3 shows a specific example of the sensor signal processing circuit. The differential amplifier 2 uses two-stage operational amplifiers G1 and G2, and inputs its output to a DC cut unit 4 using a capacitor C and an operational amplifier G3, and also branches and inputs to the above-described window comparator 3. The normal abnormality of the sensor 1 can be checked by turning on the transistor TR by a diagnosis input (off during normal operation) and forcibly grounding one sensor output A1.

That is, the window comparator 3 shown in FIG.
Comparator 3 using _two thresholds Vr ₁ and Vr ₂
The outputs V ₀ = A1−A2 of the differential amplifier 2 are monitored at ₁ and 32, and Vr ₁ <V ₀
<Normal if Vr _2, put out an abnormal output otherwise.
In this case, the input V ₀ If the sensor output A1 is accustomed to 0V is Vr ₁ <V ₀
<Vr ₂ , so that if the window comparator 3 outputs an abnormal output at this time, the diagnosis function is normal.

[Effect of the invention]

As described above, according to the present invention, it is possible to avoid a decrease in reliability due to disconnection of the bridge type sensor. That is, according to the first feature of the present invention, if one of the wirings on the power supply side and the ground side is broken, a large difference occurs in the output, so that the sensor abnormality can be detected. Therefore, it is possible to avoid a decrease in reliability of use without knowing the sensor abnormality. The second of the present invention
According to the feature, even if one of the wirings on the power supply side and the ground side is disconnected, the connection state is maintained by the other wiring. Therefore, it is possible to prevent the sensor from being abnormal due to the disconnection of one of the wirings, and the reliability is improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a sensor signal processing circuit, FIG. 3 is a detailed diagram of FIG. 2, and FIG. 4 is a configuration diagram of a window comparator. In the figure, Ra to Rd are bridge elements, A1 and A2 are output terminals, B11 and B21.
Is a power line, B12 and B22 are ground lines, C1 and C2 are wires in a bridge, and r1 and r2 are minute resistors.

Claims (2)

(57) [Scope of request for utility model registration] A first series bridge element (Ra, Rb) and a second series bridge element;
Are connected in parallel between the power supply (Vcc) and the ground (GND), and the first and second outputs from the intermediate connection points (A ₁ , A ₂ ) of each series bridge element. Wherein the first series bridge element and the second series bridge element are formed independently, and each series bridge element is individually connected to a power supply and a ground. Bridge type sensor. 2. A first series bridge element (Ra, Rb) and a second series bridge element.
Are connected in parallel between the power supply (Vcc) and the ground (GND), and the first and second outputs from the intermediate connection points (A ₁ , A ₂ ) of each series bridge element. In the bridge-type sensor, the power supply side and the ground side of each series bridge element are connected directly to the same potential side end by the in-bridge wiring (C), respectively.
A bridge-type sensor, wherein each of the first series bridge element and the second series bridge element is connected to a power source and a ground via independent wiring.