JP3240925B2 - Receiving circuit of proximity sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving circuit of a proximity sensor using ultrasonic waves or the like.

[0002]

2. Description of the Related Art Devices equipped with proximity sensors include FA robots and golf carts used in golf courses. They transmit an ultrasonic wave, a sound wave, an electromagnetic wave, or the like, hit an obstacle or the like, and detect the distance to the obstacle or the like by receiving the reflected ultrasonic wave, the sound wave, the electromagnetic wave, or the like.

Conventionally, a circuit for receiving an ultrasonic wave as shown in FIG. 3 is used. A sensor 14 for receiving a reflected wave 13 transmitted back to an object, and a fixed gain amplifier 1 for amplifying a signal obtained by converting the converted signal into an electric signal
0, a fixed resistor 11 and a reception sensitivity control unit. The receiving sensitivity control unit includes a variable amplifying resistor 3 for changing the value according to the detection distance of the object, a switch 4 of the variable amplifying resistor 3, and a switch control circuit 6 for controlling the switch 4.

[0004] For example, a proximity sensor used in a golf cart generally transmits ultrasonic waves, and converts the time from when the ultrasonic waves hit an object to when the reflected wave is received into a distance to a distance. The magnitude of the reflected wave changes extremely according to the change in the distance to the object. Therefore, the amplified output of the fixed gain amplifier 10 is saturated at a short distance due to a large reflected wave, and a significant shortage of a gain occurs at a long distance. Therefore, it is necessary to change the amplification degree in accordance with the distance to be detected, and to stabilize the amplification output of the fixed gain amplifier 10. The reception sensitivity control section is for stabilizing the output of the fixed gain amplifier 10.

[0005]

However, the conventional receiving sensitivity control section needs to increase the number of parts as the strict control is performed. The reason is that if strict control is required of the reception sensitivity control unit, it is inevitably necessary to make the stepwise control of the resistance value of the reception sensitivity control unit with respect to the detection distance in FIG. 4 fine and increase the number of stages in FIG. Because there is. Then, it is necessary to increase the numbers of the variable amplifying resistors 3 and the switches 4 in FIG. 3 and make the switch control circuit 6 perform complicated control.

An object of the present invention is to provide a proximity sensor receiving circuit which can stabilize an input voltage value to a fixed gain amplifier with a simple circuit configuration.

[0007]

In order to solve the above-mentioned problems, a receiving circuit of a proximity sensor according to the present invention receives a reflected wave 13 transmitted back to an object and returns the signal to the size of the reflected wave. A sensor 14 having a function of converting the AC voltage into a value proportional to the AC voltage, a fixed capacitor 8 that is provided with a predetermined capacitance reactance value from the AC voltage, and a reverse voltage circuit that outputs a voltage value that is inversely proportional to the AC voltage. 7 and a varicap diode 9 connected to the reverse voltage circuit 7
And a fixed gain amplifier 10.

[0008] The receiving circuit having the above-described configuration includes a receiving sensitivity control section,
The varicap diode 9 and the reverse voltage circuit 7 for the detection distance in FIG. 1 are used. The relationship between the reverse voltage and the impedance of the varicap diode 9 is as shown in FIG. By utilizing such an exponential change characteristic of the impedance of the varicap diode 9, the input voltage value to the fixed gain amplifier 10 can be stabilized. By optimizing the circuit configuration in this way, it is possible to obtain a stable output characteristic of the fixed gain amplifier 10.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a receiving circuit of the proximity sensor according to the present invention. First, when the reflected wave 13 transmitted to the object and returned is received by the ultrasonic sensor 14, the sensor 14 converts it into an AC voltage. The reverse voltage circuit 7 outputs a voltage value that is inversely proportional to the AC voltage.
This circuit 7 is connected to the cathode side of the varicap diode 9 to form an adding circuit. Since the diode 9 has characteristics as shown in FIG. 2, the reverse voltage circuit 7 sets the impedance value of the varicap diode 9 when the reflected wave detected by the sensor 14 is large (the AC voltage is large). When the detected reflected wave is small (the AC voltage is small), the circuit is configured to add and control the inversely proportional voltage value to the varicap diode 9 so as to increase the impedance value.

When the AC voltage is output from the sensor 14, it flows into the fixed capacitor 8. At this time, the fixed capacitor 8 can be converted to a certain capacitance reactance by the general formula 1 / ωc, and the AC voltage also flows into the varicap diode 9. At this time, since the varicap diode 9 has characteristics as shown in FIG. 2, when the distance between the object and the receiving circuit of the proximity sensor 14 is short,
The AC voltage converted by the sensor 14 is large, so that the reverse voltage circuit 7 operates to reduce the reverse voltage applied to the cathode side of the varicap diode 9, thereby reducing the impedance of the varicap diode 9. At this time, a large amount of the AC pressure flows in the direction of arrow a in FIG. 1, so that the fixed gain amplifier 10 can obtain a stable output without saturating the amplified output.

When the distance between the object and the receiving circuit of the proximity sensor is long, the AC voltage converted by the sensor 14 is small. Therefore, the reverse voltage circuit 7 operates to apply a reverse voltage applied to the cathode side of the varicap diode 9. By increasing the direction voltage, the impedance of the varicap diode 9 also increases.
In the fixed gain amplifier 10, a stable output can be obtained without causing a gain shortage. For the above reason, even if the distance between the object and the receiving circuit of the proximity sensor changes, the output of the fixed gain amplifier 10 can obtain a stable value with respect to the change of the detection distance.

The fixed resistor and the amplifying resistor shown in FIG. 1 are designed to have an appropriate resistance value in consideration of the balance in the device on which the receiving circuit of the proximity sensor is mounted and the overall circuit configuration.

The receiving circuit of the proximity sensor according to the present invention has a simple circuit configuration as compared with the related art, so that the yield of products can be improved. Further, the conventional proximity sensor receiving circuit having the movable portion of the switch 4 does not have long-term stability of the product, but has a configuration having no movable portion like the circuit configuration of the present invention. This stabilizes the performance of the product for a long time.

[0014]

According to the present invention, there is provided a proximity sensor receiving circuit capable of stabilizing the output characteristics of a fixed gain amplifier regardless of the distance between an object and the proximity sensor receiving circuit with a simple circuit configuration. We were able to. In addition, the number of components of the proximity sensor receiving circuit can be reduced as compared with the related art, and the proximity sensor receiving circuit having no moving part can be configured, so that the product yield and long-term stability can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a receiving circuit of a proximity sensor according to the present invention.

FIG. 2 is a diagram showing a relationship between a reverse voltage and a change in impedance of a varicap diode which is a component of a receiving circuit of the proximity sensor according to the present invention.

FIG. 3 is a schematic diagram of a receiving circuit of a conventional proximity sensor.

FIG. 4 is a diagram illustrating a resistance value of a reception sensitivity control unit with respect to a change in a detection distance of a conventional proximity sensor.

[Explanation of symbols]

7 is a reverse voltage circuit, 8 is a fixed capacitor, 9 is a varicap diode, 10 is a fixed gain amplifier, 13 is a reflected wave from an object, and 14 is a sensor.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S ^7/ 52-7/64 H03G 3/20-3/34

Claims (1)

(57) [Claims] 1. A sensor (14) and a fixed capacitor (8).
And a reverse voltage circuit (7), a varicap diode (9), and a fixed gain amplifier (10). The sensor (14) transmits a reflected wave to an object and returns (13). And converts the signal into an AC voltage having a value proportional to the magnitude of the reflected wave. The fixed capacitor (8) is provided with a predetermined capacitance reactance value from the AC voltage. Wherein the reverse voltage circuit (7) outputs a voltage value that is inversely proportional to the AC voltage, and the sensor (14) has one output terminal via the fixed capacitor (8). The fixed gain amplifier (10) is connected to one input terminal and the other output terminal is grounded. The cathode of the varicap diode (9) is the sensor (14) and the fixed capacitor ( ), The anode side is grounded, the reverse voltage circuit (7) is connected to the cathode side of the varicap diode (9) to form an addition circuit, and the fixed gain amplifier ( 10) The other input terminal is grounded via a resistor, and the reverse voltage circuit (7) is configured to detect the impedance value of the varicap diode (9) when the reflected wave detected by the sensor (14) is large. So as to increase the impedance value when the reflected wave is small,
A receiving circuit for a proximity sensor, wherein a circuit is configured to add and control the inversely proportional voltage value to the varicap diode (9).