JPH048387Y2 - - Google Patents

Description

[Detailed explanation of the invention] "Industrial application field" This invention can detect objects or measure distances by transmitting wave pulses such as radio waves or sound waves and receiving the reflected waves. The present invention relates to a wave detection device, and particularly to a wave detection device capable of changing the transmission period of wave pulses.

``Prior art'' In this type of wave detection device, when detecting a long distance, the transmission period of the wave pulse is lengthened and the transmission power (power) is increased, that is, the pulse width is lengthened. On the other hand, when detecting short distances, the wave pulse transmission cycle is shortened to obtain the detection signal quickly, and the pulse width is narrowed to prevent the transmission power from increasing. Ta.

In addition, in the past, in order to change the transmission power according to the transmission period of the wave pulse, in addition to controlling the pulse width, it was also possible to control the amplitude of the pulse, that is, the longer the period, the larger the amplitude. Proposed.

``Problem that the invention aims to solve'' However, in ultrasonic detection devices, there is a limit to how short the pulse width can be due to the characteristics of the ultrasonic transducer, and the standards also limit the pulse width to a certain value or more. It had been. However, there are increasing demands for short-distance detection, and there are cases where it is necessary to quickly obtain information obtained from short-distance detection one after another.In such cases, it is recommended to shorten the pulse width. However, in order to shorten the transmission wave repetition period, the transmission power becomes large, which increases the load on the power supply circuit of the transmission circuit, and there is also the risk of destroying the transmission transistor and the like. Similarly, when controlling the pulse amplitude, the amplitude control becomes transiently excessive, and the circuit elements of the transmitting circuit may be destroyed.

The object of this invention is to provide a wave detection device that can automatically reduce the transmission power when the transmission repetition period becomes short, thereby reducing the burden on the transmission circuit and its power supply circuit.

"Means for Solving the Problem" According to this invention, a period-compatible voltage generating means is provided which generates a lower voltage as the period of the transmission pulse becomes shorter, and the output voltage of the period-compatible voltage generating means and the transmitting high voltage are The voltage of the capacitor is compared with the voltage of the transmission high-voltage capacitor in a comparison circuit, and if the voltage of the transmission high-voltage capacitor becomes higher, charging suppression means is provided to stop charging the transmission high-voltage capacitor or to sufficiently slow down the charging. ing.

"Embodiment" A case will be described below in which an embodiment of the wave detection device according to this invention is applied to an ultrasonic detection device.
In FIG. 1, a clock from a clock generator 11 is frequency-divided by a frequency divider 12 to produce pulse signals of various transmission periods and supplied to a selector 13. A signal indicating the detection range set from the range setting device 14 is input to the selector 13, and a periodic pulse having a signal with a period corresponding to this signal is selected from the selector 13. The periodic pulse is supplied to a transmission pulse width generation circuit 15. The transmission pulse width generation circuit 15 consists of a plurality of monostable multivibrators with different time constants, and these monostable multivibrators are driven by input pulses and output pulses with various pulse widths at the same repetition period as the input periodic pulse. do.

These pulses with a plurality of pulse widths are selected by the selector 16.
The one corresponding to the range set in is selected. In other words, the longer the selector 16 corresponds to the set range, the longer the cycle is.
and a transmission pulse with a wide pulse width is selected and input to the modulation circuit 17, the ultrasonic frequency is keyed modulated by the pulse, and the modulated output is amplified by the transmission amplifier 18 and sent to the ultrasonic transducer 19.
The ultrasonic pulse is transmitted. The reflected wave of the transmitted ultrasonic pulse is guided from the transducer 19 to the receiver 21, where it is amplified and detected and supplied to the processing and display device 22, where the necessary processing is performed and the detected information is in the desired state. Is displayed.

In this invention, period-corresponding voltage generating means 23 is provided which corresponds to the transmission pulse period and generates a lower voltage as the period becomes shorter. For example, the period corresponding voltage generation means 23 receives a periodic pulse from the selector 13 and converts it into a constant width pulse in a pulse generation circuit 24, and the constant width pulse is inputted to an integral control circuit 25, and the input pulse has a short period. so that the integration becomes slower and the output voltage becomes lower.
In other words, the shorter the period, the lower the voltage generated.

The output of this period-corresponding voltage generating means 23 is supplied to a comparison circuit 26 and compared with the voltage of a transmission high-voltage capacitor (not shown in the diagram) inside the transmission amplifier 18, and if the voltage of the transmission high-voltage capacitor is higher, The output of the comparison circuit 26 stops or suppresses charging of the transmission high voltage capacitor.

FIG. 2 shows a specific example of the cycle-compatible voltage generating means 23 and the charging suppressing means. That is, for example, a high voltage power supply terminal 31 of 200V is connected through a resistor 32 and further through a transistor 33 to an output terminal 34, and the output terminal 34 is connected to a load 30 including a transducer. Further, this output terminal 34 is grounded through a transmission high voltage capacitor 35, the transmission output terminal 34 is further grounded through a series circuit of resistors 36 and 37, and the voltage dividing point of the resistors 36 and 37 is connected to the non-inverting input of the comparison circuit 26. connected to the end.

A pulse of constant width from the pulse generation circuit 24 is sent from a terminal 38 to a transistor 39 of the integral control circuit 25.
The emitter of the transistor 39 is grounded, and the collector is connected to the non-inverting input terminal of the comparison circuit 26 through a Zener diode 42 and a resistor 43 as required. Further, for example, a low voltage power supply terminal 44 of plus 12V is connected to one end of a capacitor 47 through an FET 45 and a resistor 46, and the other end of the capacitor 47 is grounded. A connection point 55 between the resistor 43 and the capacitor 47 is connected to a non-inverting input terminal of the comparison circuit 26. FET4 at the connection point 55
5 gates are connected. The output side of the comparison circuit 26 is connected to the base of a transistor 48, and the collector of the transistor 48 is connected to the base of the transistor 33 through a resistor 49. The high voltage power supply terminal 31 is connected to the base of a transistor 33 through a diode 51 and a resistor 52. Furthermore, the base of transistor 33 is grounded through resistor 53.

The periodic pulse with period T ₀ shown in FIG. 3A selected by the selector 13 in FIG.
As shown in FIG. 3B, a pulse having the same period as the transmission pulse is outputted, with a constant width ₁ that coincides with the rise of the periodic pulse and is wider than this. In the integral control circuit 25, the capacitor 47 is charged with a constant current through the FET 45, and when the pulse shown in FIG. The charge in the capacitor 47 is discharged by a certain amount. When the discharge ends
The capacitor 47 is charged with a constant current through the FET 45, and therefore the voltage at the non-inverting input terminal of the comparator circuit 26 has a pulse width as shown in FIG. 3C.
The voltage drops during T ₁ and then gradually increases with constant charging speed.

On the other hand, the electric charge in the transmission high voltage capacitor 35 is discharged by the transmission pulse, and the pulse is transmitted as shown in FIG. 3D, and the voltage of the transmission high voltage capacitor 35 decreases due to the discharge as shown in FIG. , the voltage at the inverting input terminal of the comparator circuit 26 decreases and the voltage at the non-inverting input terminal increases, and the output of the comparator circuit 26 becomes the third
As shown in FIG. F, the level becomes high, so the transistor 48 is turned on and the base potential of the transistor 33 is lowered, the transistor 33 is turned on, and the transmission high voltage capacitor 35 is charged with a constant current. Due to this charging, the voltage of the transmission high voltage capacitor 35 gradually increases as shown in FIG. 3E. As the voltage of the capacitor 35 increases, a voltage obtained by dividing the voltage is applied to the comparator circuit 26.
Comparator circuit 2 becomes higher than the voltage at the non-inverting input terminal of
The output of 6 is inverted to a low level as shown in FIG. 3F. Therefore, transistor 48 is turned off,
Therefore, the transistor 33 is turned off or only a small amount of current flows, and the voltage of the transmission high voltage capacitor 35 is maintained at a constant voltage _V1 .

Because of this operation, when the transmission period T ₀ becomes shorter, the period in which the transistor 39 is turned on becomes shorter, and therefore the discharge of a certain amount of the capacitor 47 becomes faster, and the rate at which the charging voltage of this capacitor 47 increases is reduced. However, the average voltage of the capacitor 47 becomes lower as the transmission period T ₀ becomes shorter. Therefore, when the voltage of the transmission high-voltage capacitor 35 is low, the output of the comparator circuit 26 becomes low level, and the transistor 48 is turned off at an early stage after pulse transmission, and charging of the transmission high-voltage capacitor 35 is stopped or suppressed. In other words, the charging period for the transmission high-voltage capacitor 35 is shortened, and the voltage of this capacitor 35 is suppressed to a low state. Therefore, the transmission power can be reduced even if the width of the transmission pulse is not narrowed that much.

On the other hand, when the transmission period T ₀ is long, the transmission high-voltage capacitor 35 is sufficiently charged, and therefore the transmission power becomes large. In this case, even if the transmission power is large, the load on the transmission power supply circuit and the transmission transistor is not so large because the repetition period T ₀ is long. If the transmission period T ₀ is shortened, the transmission power will be reduced simply by shortening it, and the pulse width can be set to a predetermined value or more, and there is no burden on the power supply circuit and there is less burden on the transmission circuit.

Note that the Zener diode 42 prevents the voltage of the capacitor 48 from dropping below a predetermined value. As shown in Fig. 4, the cycle-compatible voltage generation means uses the setting range from the range setting device 14.
Alternatively, the ROM 61 may be read out, the read output of the ROM 61 may be converted into an analog signal by the DA converter 62, and the analog signal may be supplied to the comparison circuit 26. This idea can be applied not only to ultrasonic detection devices but also to radars, etc.

``Effects of the invention'' As described above, the wave detection device according to the invention can reduce the transmission power as the transmission period becomes shorter without reducing the transmission wave pulse width below a predetermined value. As a result, the average transmission power can be lowered, reducing the burden on the power supply circuit and reducing the burden on the transmission circuit.
It is possible to obtain information quickly over short detection distances.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example in which this invention is applied to an ultrasonic detection device, Fig. 2 is a connection diagram showing a specific example of its main parts, and Fig. 3 is a time chart for explaining its operation. FIG. 4 is a block diagram showing another example of the period-corresponding voltage generating means.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A device capable of repeatedly transmitting wave pulses, receiving the reflected waves to obtain a detection signal, and changing the transmission cycle of the wave pulses, and capable of transmitting high voltage. A capacitor is charged through a charging circuit, and each time a wave pulse is transmitted, the charge in the transmission high-voltage capacitor is discharged to transmit a wave pulse. In a wave detection device configured to reduce the amplitude of the wave pulse, a period corresponding voltage generating means generates a lower voltage as the transmission period of the wave pulse is shorter, and a voltage generated by the period corresponding voltage generating means and the transmitting high voltage. a comparison circuit that compares the voltage of the capacitor with the voltage of the transmission high voltage capacitor, and when the voltage of the transmission high voltage capacitor becomes higher, the output of the comparison circuit stops supplying current to charge the transmission high voltage capacitor;
Or a wave detection device comprising charge suppression means for reducing the charge current to a sufficiently small value. (2) The period-compatible voltage generation means includes a pulse generation circuit that generates a constant width pulse having the same period as the transmission period of the wave pulse, a second capacitor, and charging the second capacitor with a constant current. a constant current circuit connected in parallel with the second capacitor, and a switch element that is turned on by the constant width pulse and discharges the charge of the second capacitor by a fixed amount; 2. The wave detection device according to claim 1, wherein the output voltage of the period-corresponding voltage generating means is a voltage of .