JPS6348320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic pulse generator used for transmitting ultrasonic pulses in, for example, a fish finder or an ultrasonic measuring device.

For example, in a conventional ultrasonic pulse transmitter used in a fish finder, as shown in FIG. It oscillates during the pulse width of the envelope, and the oscillation output is amplified by the amplifier circuit 13, and the amplified output is sent to the drive circuit 1.
Drive 4. This drive circuit 14 is configured as a push-pull amplifier, and the amplifier 13 and the push-pull amplifier 14 are coupled by a transformer 15, the middle point of the secondary side of the transformer 15 is grounded, and the output from both ends of the secondary side Transistors 16 and 17 are driven in a push-pull manner.
A tuning circuit 18 tuned to the carrier wave of the ultrasonic pulse is connected between the collectors of the transistors 16 and 17, and the primary side of a transformer 19 is used as the coil of the tuning circuit 18. A midpoint of the transformer 19 is connected to a power supply terminal 21.

The transmission output circuit 22 includes a plurality of transistors 2
3, 24, and 25 are connected in parallel, and the same number of transistors 26, 27, and 28 are connected in parallel, and their input sides are connected to both ends of the secondary side of the transformer 19 through resistors, respectively.
The middle point of the secondary side of 9 is grounded. The emitters of these two sets of parallel transistors are grounded, the primary side of the transformer 29 is connected between the respective collectors, the midpoint of the primary side of the transformer 29 is connected to the power supply terminal 31, and the transmission/reception is carried out between both ends of the secondary side. Wave device 32 is connected.

In this way, in the conventional ultrasonic pulse transmitter, the sine wave signal from the oscillation circuit 12 is processed as a sine wave and applied to the output push-pull amplifier circuit. The carrier wave of this ultrasonic pulse is, for example, 10K
Since the frequency is relatively high, about Hz to 200KHz, and the output level is quite large, the output transformer 19 of the drive circuit 14 and the transformer 15 on the input side thereof also use large, expensive transformers with relatively large power capacities. The need arose.

Furthermore, in the drive circuit 14, the tuning frequency of the tuning circuit 18 matches the ultrasonic carrier frequency, so if the radiated ultrasonic frequency differs, it is necessary to replace the transformer 19 in order to use it efficiently.

Furthermore, the AC signal is processed, and the amplifier circuit 13,
In the drive circuit 14, these active elements are always operating every half cycle, and in the output push-pull amplifier circuit 22, these transistors are also operating every half cycle, so that they can be used as transistors for high power applications. I needed to use one.

Conventionally, in order to adjust the level of the ultrasonic pulse output, a group of resistors 33 and a switch 3 are installed between the coil and the transducer 32 on the secondary side of the output transformer 29.
4 and the resistor is selectively inserted. That is, the output of the transducer 32 is adjusted by inserting and removing a resistor at the portion of the highest output.
For this reason, it is necessary to use high-power resistors 33 and changeover switches 34, which makes them more expensive.

The object of this invention is to transmit ultrasonic pulses that can be driven efficiently without using an expensive transformer, can change the output with a relatively small amount of power, and can be constructed at low cost. The goal is to provide equipment.

According to the present invention, two pulse trains having the same period but different in phase by 180 degrees are generated, and these two pulse trains are respectively supplied to two input sides of an output push-pull amplifier circuit through a variable voltage dividing circuit. A transducer is connected to the output transformer of the push-pull amplifier circuit. In this way, the input side of the push-pull amplifier circuit on the output side is processed with pulses, and the drive to the push-pull amplifier circuit is also performed with pulses, so the drive time for each transistor is short, and transistors with low power capacity can be used accordingly. Furthermore, since no transformer is used in the drive circuit, it can be constructed at low cost, and there is no need to replace the transformer even if the ultrasonic carrier frequency is changed. Further, the output level is adjusted by a variable voltage dividing circuit, and since this variable voltage dividing circuit is provided on the drive circuit side, it is a relatively low power part and can be constructed at low cost.

Next, an embodiment of the ultrasonic pulse transmitter according to the present invention will be described with reference to FIG. In FIG. 2, parts corresponding to those in FIG. 1 are shown with the same reference numerals, but in the present invention, two pulse trains having a phase difference of 180 degrees are generated by a pulse generating circuit. For example, an oscillation circuit 35 that oscillates at a frequency twice the carrier frequency of the ultrasonic pulse to be generated.
is provided, and this oscillation circuit 35 is driven by a start signal from the input terminal 11 during the envelope of the ultrasonic pulse. As a result, a sine wave signal as shown in FIG. 3A is obtained, and this sine wave signal is waveform-shaped by the waveform shaping circuit 36 and converted into a duty 1 square wave signal as shown in FIG. 3B. The output of this waveform shaping circuit 36 is a toggle type flip-flop 37.
and its Q and output are each NAND
The signal is supplied to gates 38 and 39. On the other hand, the output of the waveform shaping circuit 36 is the monostable multivibrator 4
1 and operates at the rising edge of a pulse whose waveform is shaped as shown in FIG. 3C, and a pulse having a pulse width τ is output. The output of this monostable multi-pile vibrator 41 is the NAND gate 38,
39. Yotsute NAND gate 38,
39, as shown in Figure 3 D and E, respectively.
Two pulse trains are obtained that are 180 degrees out of phase and have the same period as the carrier wave period of the transmitted ultrasonic pulse.

The outputs of these NAND gates 38 and 39 are input to push-pull amplifiers 42 and 43, respectively, each having an NPN type transistor and a PNP type transistor connected in a single-ended manner. The respective outputs of the single ended push-pull amplifiers 42 and 43 are input to variable voltage dividing circuits 44 and 45, respectively. The variable voltage divider circuits 44 and 45 have, for example, switches 46 and 47, respectively, and a plurality of resistors switched and connected by the switches between the push-pull amplifiers 42 and 43 and the two input sides of the output push-pull amplifier circuit 22. Resistors 48 and 49 are respectively connected between the base input side of the transistor of the push-pull amplifier circuit 22 and the ground.

Therefore, the resistors selectively inserted by the switches 46 and 47 and the resistors 48 and 49 are used to create a single-ended push-pull amplifier, that is, the amplitudes of the two series of pulses are adjusted appropriately, and the output push-pull amplifier is created. It will be input to the bases of each of the two sets of transistors in the circuit 22. A transducer 32 is connected to the secondary side of the output transformer 29 without using a resistor for level adjustment.

Therefore, the amplified output pulses shown in FIGS. Transistors 23, 24, 25 and 2
6, 27, and 28 are driven alternately. The output is transmitted through the transformer 29 to the transducer 32 which is driven alternately in the normal phase and in the opposite phase to obtain a sinusoidal output as shown in FIG. 3H and radiate ultrasonic pulses.

Both ends of the secondary side of the output transformer 29 are connected to both ends of a transmission/reception switching circuit 53 via capacitors 51 and 52, and also to a reception input transformer 54. The secondary side of the reception input transformer 54 is the reception circuit 5
Connected to 5. The transmission pulse short-circuits the diode of the transmission/reception switching circuit 53, and a tuning circuit is formed by the output transformer 29 and capacitors 51 and 52. At the time of reception, the transmission/reception switching circuit 53 is open, the capacitors 51 and 52 constitute a series tuned circuit with the primary side of the input transformer 54, and the received signal of the transducer 32 is supplied to the reception circuit 55.

As described above, according to the ultrasonic pulse transmitter according to the present invention, the drive circuit for the output push-pull amplifier circuit 22 does not use the transformer 19 or the transformer 15 as described in FIG. It can be constructed in a compact size, and there is no need to replace the transformer when changing the ultrasonic carrier frequency.

Furthermore, the level of the output ultrasonic pulse can be adjusted by switching the switches 46 and 47 of the variable voltage divider circuits 44 and 45. Since the power level is lower than that in the case where the power level is lower than that in the case where the power level is lowered, the resistors and switches used as the variable voltage dividing circuits 44 and 45 may be of a lower power level.

By switching and connecting resistors in the variable voltage dividing circuits 44 and 45, the ultrasonic pulse level can be changed significantly. In order to finely change the level of the ultrasonic pulse, the output pulse width τ of the monostable multivibrator 41 may be adjusted by adjusting the variable resistor 51 in its time constant circuit. If an attempt is made to adjust the output level using only this pulse width τ, the pulse width may become too small when the level is reduced to a certain extent, making it difficult to operate reliably. However, in the present invention, there is no such fear because variable voltage dividing circuits 44 and 45 are used.

If the performance of the output transistors 23 to 28 is relatively poor and the charge accumulation time between their bases and emitters is relatively long, taking this into account and reducing the width τ of the drive pulse accordingly, these transistors will not generate unnecessary heat. It is possible to drive the transistor only for an effective period of time without fear of causing damage, that is, to drive the transistor in pulses with the minimum necessary amount to the extent that the desired power can be supplied to the transducer 32.

Since a plurality of output transistors 23 to 28 are connected in parallel, the input impedance becomes considerably small, but the output impedance can be sufficiently lowered by the single-ended push-pull amplifier circuits 42 and 43.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing a conventional ultrasonic pulse transmitter, Fig. 2 is a connection diagram showing an example of an ultrasonic pulse transmitter according to the present invention, and Fig. 3 is a waveform diagram used to explain its operation. be. 11: Input terminal, 22: Output push-pull amplifier circuit, 29: Output transformer, 32: Ultrasonic transducer, 35: Oscillator circuit, 36: Waveform shaping circuit, 3
7: toggle type flip-flop, 41: monostable multivibrator, 42, 43: single-ended push-pull amplifier circuit, 44, 45: variable voltage divider circuit.

Claims (1)

[Scope of Claims] 1. An ultrasonic pulse transmitter that amplifies the generated pulses using a push-pull amplifier circuit, converts the generated pulses into ultrasonic waves, and transmits them, which comprises: a. Output of two pulse trains of the same period with a phase difference of 180 degrees; b) a first resistor to which the outputs of the two pulse trains are respectively supplied, and a second resistor connected in series to the first resistor; (c) voltage dividing means for voltage-dividing each output of the two pulse trains using a voltage circuit; and (c) amplifying means for amplifying each divided voltage output obtained by the second resistor by applying it to each input of the push-pull amplifier circuit. , d an output changing means for changing the magnitude of the output of the amplification by changing the ratio of the first resistor and the second resistor. . 2. The ultrasonic pulse transmitter according to claim 1, wherein the first
2. An ultrasonic pulse transmitting device characterized in that the ratio between the resistor and the second resistor is changed only by changing the value of the first resistor.