JPH06341977A - Ultrasonic transmission circuit - Google Patents

Abstract

PURPOSE:To reduce consumed electric power in an ultrasonic transmission circuit which amplifies a transmission signal generated synchronously with a transmission synchronous signal through an amplifying element and outputs it to an ultrasonic piezoelectric transducer. CONSTITUTION:A transmission circuit 11 has a wideband power amplifier 12 which amplifies a transmission signal from a terminal 13 and outputs it from a terminal 16 to an ultrasonic piezoelectric transducer SU. The source voltage of the amplifier 12 is applied through a capacitor C when a switch SW is turned on. The switch SW is rept turned onduring a term from a fixed time before the front edge of a transmission synchronous signal to the rear edge of the said signal by a control signal which rises a fixed time before the front edge of the transmission synchronous signal and falls clown at the time of coinciding with the rear edge of the said signal. Thus, the wideband power amplifier 12 is actuated for only both a term when the transmission signal is input and a fixed time just before it, and separated from a power source terminal 15 except the above terms.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic wave transmission circuit, and more particularly to an ultrasonic wave transmission circuit for amplifying and outputting a transmission signal for exciting an ultrasonic transducer.

[0002]

2. Description of the Related Art An ultrasonic flaw detector having a structure as shown in FIG. 8 is known as an ultrasonic measuring device. In this ultrasonic flaw detector, an ultrasonic wave oscillator in the probe 2 is excited by the output transmission pulse of the transmission circuit 1 to generate an ultrasonic wave, and the ultrasonic wave is made incident on the measured material 4. This incident ultrasonic wave is applied to the measured material 4
The light is reflected by inner flaws and inner and outer surfaces, received by the probe 2, and further converted into an electric signal (reflected echo signal). The reflected echo signal is amplified to a required level by the reception amplification circuit 3 and then output to a measurement circuit (not shown) in the subsequent stage.
The ultrasonic flaw detector uses the amplitude of this reflected echo signal and the time from the time when the ultrasonic wave is transmitted to the time when the ultrasonic wave is received.
The size and depth of the internal flaws, the dimensions of the material 4 to be measured, and the physical properties are measured.

In such an ultrasonic flaw detector, the transmission circuit (that is, the ultrasonic transmission circuit) 1 is conventionally configured, for example, as shown in FIG. In the figure, switching NPN
The transistor Q _a has an emitter grounded and a collector connected to a power supply terminal via _a charging resistor R _a , while being connected to a cathode of a diode D via a circuit portion including _a charging / discharging capacitor C _a and a resistor R _b. It is connected. The anode of the diode D is grounded via a variable resistance R _c for damping, and is also connected to the ultrasonic transducer SU in the probe 2 via a terminal 6. The diode D has a high impedance during reception and prevents the influence of the transmission circuit 1 from affecting the reception amplification circuit 3.

In the transmission circuit having the above structure, a pulse (transmission synchronization signal) having a constant period is input to the base of the transistor Q _a . While the input pulse is at the low level, the transistor Q _a is off and the capacitor C _a is charged by the power supply voltage via the resistor R _a . When the input pulse goes high in this state, the transistor Q
_{After a} is turned on and the charge accumulated in the capacitor C _a is instantly discharged through the transistor Q _a ,
Since current is supplied through a resistor R _b to the capacitor C _a, the terminal voltage of the resistor R _b is gradually rises toward 0V direction.

Since the above-mentioned input pulse becomes high level for a short time and then becomes low level again, the transistor Q _a is
Will be off again. Then, the capacitor C _a is charged initiated by the power supply voltage from the time the Q _a is turned off, since the current flowing through the resistor R _b according to the charging of the capacitor C _a is gradually reduced, the terminal of the resistor R _b The voltage gradually decreases in the 0V direction. Thereafter, the same operation as above is repeated.

As a result, _a negative pulse that rises according to the discharge time constant determined by the respective values of the capacitor C _a and the resistor R _b is generated at both ends of the resistor R _b from the time when the input pulse becomes high level, and the input pulse is input. From the time when the pulse becomes low level, _a positive polarity pulse that falls according to the charging time constant determined by the capacitor C _a and the values of the resistors R _a and R _b is generated.

The positive polarity pulse is blocked by the diode D, but the negative polarity pulse biases the diode D in the forward direction to turn it on. Therefore, the negative polarity pulse passes through the diode D to the ultrasonic transducer SU. It is applied as a transmission pulse and excites it.

Therefore, in the conventional ultrasonic transmission circuit, the transistor Q _a is turned on only when transmitting, and at other times, the capacitor C _a is only charged, so that the power consumption is extremely small. We have realized a compact, lightweight, low power consumption ultrasonic flaw detector.

However, in recent years, when performing ultrasonic flaw detection on a material to be measured with a large attenuation of ultrasonic waves (for example, a material to be tested having coarser crystal grains than ordinary steel such as stainless steel and cast steel), In the conventional ultrasonic wave transmission circuit, the frequency component of the transmission pulse has a wide band, and therefore flaw detection cannot be performed with a sufficient S / N ratio. Therefore, conventionally, it has been attempted to detect a flaw by controlling the transmission frequency and the frequency (wave number) of the ultrasonic transducer. Further, it has been attempted conventionally to perform flaw detection according to the purpose by changing the waveform of the transmission signal to change the frequency component and energy.

[0010]

However, in the conventional ultrasonic transmission circuit which controls the transmission frequency, the wave number of the ultrasonic transducer, and the transmission waveform as described above, a wide band large power amplifier is required. However, this wide band high power amplifier requires waveform fidelity. Therefore, the operating point of the amplification element is set to class A or class AB, the power consumption is large, and the heat dissipation mechanism is large. For this reason, in the above-mentioned conventional circuit, the ultrasonic flaw detector is large in size, and both the mass and the power consumption are large, so that there is a problem in transportation to the site where the ultrasonic flaw detection is desired.

If a power source is not available at the site, it is necessary to operate with a battery. However, since the conventional circuit consumes a large amount of power, it cannot operate for a long time and requires a large battery. Further, the conventional ultrasonic transmission circuit needs to have a component capable of withstanding the generation of heat by a large amount of power, and needs a heat dissipation mechanism, resulting in a high manufacturing cost.

An object of the present invention is to provide an ultrasonic transmission circuit which can supply power only when the amplifier for amplifying a transmission signal is operating and can reduce current consumption.

Another object of the present invention is to reduce the power capacity of the wide band power amplifier, to eliminate the need for a heat dissipation mechanism, and to make the ultrasonic flaw detector small, lightweight and inexpensive. Another object of the present invention is to provide an ultrasonic transmission circuit that can be configured as described above.

[0014]

In order to achieve the above object, an ultrasonic transmission circuit of the present invention amplifies a transmission signal generated in synchronization with a transmission synchronization signal with an amplifying element and outputs it to an ultrasonic transducer. In the ultrasonic transmission circuit, provided is means for synchronizing the transmission synchronization signal with a unit for activating the amplification element during a period from immediately before the front edge of the transmission synchronization signal to a certain time immediately before the rear edge of the transmission synchronization signal. It has a different structure.

[0015]

Since the ultrasonic transmission circuit of the present invention is provided with means for turning on the power supply to the amplifying element during a period from immediately before the fixed edge of the transmission synchronization signal to a fixed edge of the transmission synchronization signal, the transmission synchronization signal is provided. The voltage necessary for the operation is input to the amplifying element in the transmission circuit immediately after a certain time from the leading edge of the signal.

Immediately after the power is turned on, a transient phenomenon occurs due to a time constant element such as a capacitor inside the transmission circuit, but it becomes active within a predetermined time. In the present invention,
Since the power is turned on for a certain period of time, which is longer than this predetermined time, immediately before the leading edge of the transmission synchronization signal is input, it is generated in the active amplifying element in synchronization with the leading edge of the transmission synchronization signal. The transmitted signal is input and amplified normally.
At the same time as the end of the transmission, which is the trailing edge of the transmission synchronization signal, the power input to the amplification element is cut off, so that the transmission circuit including the amplification element is put into an operation stop state.

Therefore, according to the present invention, the amplifying element in the transmission circuit operates intermittently in synchronization with the transmission synchronization signal. Therefore, compared with the conventional transmission circuit in which the power is always turned on and is always in operation, It is possible to reduce current consumption.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the ultrasonic transmission circuit according to the present invention. In the figure, the transmission circuit 11 has a wide band power amplifier 12, a switch SW and a capacitor C. The broadband power amplifier 12 is configured such that the power supply voltage is applied from the power supply terminal 15 via the switch SW. The switch SW is a circuit that is switched by a control signal applied via the terminal 14, one end of which is connected to the power supply voltage input terminal of the broadband power amplifier 12, and the other end of which is the power supply terminal 15 and the non-grounded side of the capacitor C. It is connected to the terminal. The capacitor C is set to a large capacitance value and inputs a large amount of power to the wide band power amplifier 12.

Next, the operation of this embodiment will be described.
Based on the transmission synchronization signal of the constant cycle T shown in FIG. 2C, the transmission circuit 11 changes from the input time t _{2 of the} leading edge (here, rising edge) of the transmission synchronization signal to the trailing edge (here, falling edge). During the period until the input time t ₃ , the transmission signal shown in FIG. 2D is received at the terminal 13 from the oscillation circuit not shown in FIG. 1 and input to the wide band power amplifier 12.

Here, the control signal shown in FIG. 2 (A), which rises just before a fixed time from the leading edge of the transmission synchronizing signal and falls at the same time as the trailing edge of the transmitting synchronizing signal, is transmitted through the terminal 14. Is applied to the switch SW to control the switching. The switch SW is turned on during a high level period of the control signal, that is, from a time point t _{1 which} is a predetermined time before the leading edge of the transmission synchronization signal to a time point t ₃ which is a trailing edge of the transmission synchronization signal, and the capacitor C The power supply voltage charged in the above is applied to the broadband power amplifier 12.

As a result, the bias voltage of the amplification element in the wide band power amplifier 12 gradually rises according to the time constant of the time constant element such as the capacitor in the wide band power amplifier 12 as shown in FIG. Later, a predetermined voltage is reached, that is, the voltage at which the wideband power amplifier 12 operates steadily, which causes the wideband power amplifier 12 to enter an active steady state.

Since the rising edge of the control signal is set so that the leading edge of the transmission synchronizing signal is input immediately after the wide band power amplifier 12 is brought into the active steady state, FIG.
The transmission signal shown in (D) is input to the wideband power amplifier 12 immediately after the active steady state. Then, the individual transmission signals are output to the output terminal 16 after being normally power-amplified here.
Is applied to the ultrasonic transducer SU in the probe via the, and this is excited to generate ultrasonic waves. This ultrasonic wave is incident on the material to be measured.

When the input of the transmission signal is completed at time t _3, at the same time, the control signal becomes low level as shown in FIG. 2A, and the switch SW is turned off. As a result, the application of the power supply voltage to the broadband power amplifier 12 is cut off, and the bias voltage of the internal amplifying element of the broadband power amplifier 12 falls as shown in FIG. Hereinafter, the above operation is repeated in synchronization with the transmission synchronization signal.

As described above, in the present embodiment, the power supply voltage to the wide band power amplifier 12 is intermittently input by the control signal synchronized with the transmission synchronizing signal, and the wide band power amplifier is transmitted only during transmission and for a certain time immediately before it. In order to operate 12,
It is possible to reduce power consumption more than ever before.

The effect of reducing the power consumption will be further described. Now, the operating current consumption of the broadband power amplifier 12 is I _p , the transmission repetition period is T, and the transmission operation time is T _w.
Then, the average current consumption I _av is expressed by the following equation. I _av = I _p × T _w / T (1) Further, the relationship between them is as shown in FIG.

A typical operating state is a transmission frequency of 5M.
Hz, transmission wavenumber two waves, a certain time before transmission (= t ₂ -t ₁₎
10 μs (thus, the transmission operation time T _w is 10.4 μ
s), assuming that the transmission repetition period T is 1 ms, the operating voltage and efficiency of the wide band power amplifier 12 are 100 V and 50%, and the transmission power is 100 W, the consumption current I _p is expressed by the following equation. I _p = (transmission power) / {(operating voltage) × (efficiency)} (2) From this equation, the consumption current I _p is 2A. Substituting these numerical values into the equation (1), the average current consumption I _av becomes 2
It becomes 0.8 mA. Therefore, it is possible to obtain a power saving effect of about 1/100 as compared with the operating current consumption of 2 A of the conventional circuit which is always operating.

Next, the transmitter circuit 11 and the circuit on the input side thereof will be described in more detail. FIG. 4 is a specific circuit diagram of the first embodiment of the ultrasonic transmission circuit of the present invention, and FIG. 5 is a block diagram of a circuit on the input side of the transmission circuit 11. 5, parts that are the same as the parts shown in FIG. 1 are given the same reference numerals, and descriptions thereof will be omitted.

The transmitter circuit 11 shown in FIG. 5 comprises the wideband power amplifier 12 shown in FIG. First, the circuit on the input side of the transmission circuit 11 will be described with reference to the block diagram of FIG. 5 and the time chart of FIG.

In FIG. 5, reference numeral 21 is a flip-flop, which receives the synchronization signal shown in FIG. 6 (A) at its set terminal S and is set at the rising edge thereof. With this setting, the high-level control signal shown in FIG. 6B extracted from the Q output terminal of the flip-flop 21 (see FIG.
(Same as (A)) is input to the on-delay circuit 22, and after a certain period of time TD from its rising, FIG.
It is delayed to stand up as shown in. This fixed time TD is the same as the time from the time t ₁ to t _{2 in} FIG. 2 described above, and the transistors Q1 and Q2 in FIG.
Is set to a value much larger than the time required to enter active steady state.

The output signal of the on-delay circuit 22 is
It is input to the control oscillation circuit 23, and the control oscillation circuit 23 oscillates only during the high level period. The control oscillation circuit 23 oscillates and outputs a sine wave having a predetermined frequency by this oscillation operation, and outputs the sine wave to the transmission circuit 11 and the wave number control circuit 24, respectively. The wave number control circuit 24 is a circuit that sets the wave number of a transmission signal that excites the ultrasonic transducer SU, and includes a counter or the like. The wave number control circuit 24 outputs an oscillation stop signal as shown in FIG. 6E when the sine wave having the set wave number has been input. This oscillation stop signal has a pulse width set to a value sufficient to reset the flip-flop 21 by the time constant in the wave number control circuit 24, and is applied to the reset terminal R of the flip-flop 21 to set it. Reset.

When the flip-flop 21 is reset, its Q output terminal becomes low level as shown in FIG. 6 (B), so that the output signal of the on-delay circuit 22 also becomes as shown in FIG. 6 (C). It becomes a low level, and the oscillation operation of the control oscillation circuit 23 stops. When the oscillation operation of the control oscillation circuit 23 is stopped, the output of the sine wave extracted from the control oscillation circuit 23 is stopped, as shown in FIG. Q of the flip-flop 21 shown in FIG.
The output signal is also sent to the transmission circuit 11 by the control signal (see FIG. 2).
(Same as (A)).

The output signal of the on-delay circuit 22 shown in FIG. 6C is the transmission synchronization signal shown in FIG. 2C, and the output signal of the control oscillation circuit 23 shown in FIG. It is the transmission signal shown in FIG. In this way, the control oscillation circuit 23 synchronizes with the input transmission synchronization signal and shows the wave number set by the wave number control circuit 24 in FIG.
The sine wave shown in (D) is oscillated. This sine wave is supplied to the transmission circuit 11 as a transmission signal, power-amplified here, and then output to the ultrasonic transducer in the probe.

Next, the first embodiment of the specific circuit configuration of the transmission circuit 11 will be described with reference to FIG. In FIG. 4, the primary winding of the transformer T1 is connected to the terminals 13 and 13 ', one end of the secondary winding is connected to the base of the NPN transistor Q1, and the other end is connected to the base of the NPN transistor Q2. There is. The emitters of the transistors Q1 and Q2 are grounded, and the collectors thereof are connected to the respective ends of the primary winding of the transformer T2. An ultrasonic transducer SU is provided on the secondary winding side of the transformer T2.
Are connected. The transformers T1 and T2 and the transistors Q1 and Q2 form a push-pull amplifier circuit that forms the wideband power amplifier 12.

The center tap of the transformer T1 is
It is grounded via a parallel circuit of a resistor R1 and a capacitor C1, and is also connected to a center tap of a transformer T2 and a capacitor C2 via a resistor R2.
The resistors R1 and R2 are transistors Q that are amplification elements.
1 and Q2 are bias resistors for setting operating points of class A or class AB. The capacitors C1 and C2 are bypass capacitors that bypass high frequency components.

The common connection point of the center tap of the transformer T2, the resistor R2 and the capacitor C2 is connected to the power supply terminal 15 via the collector and emitter of the PNP transistor Q3.
It is connected to the. The emitter of the transistor Q3 is grounded via a capacitor C3 having a large capacitance value for supplying a large amount of power when the broadband power amplifier 12 operates. Also, the base of the transistor Q3 is a resistor R
3 is connected to the emitter of the NPN transistor Q4 via a resistor R4. The base of the transistor Q4 is supplied with a negative power supply voltage via the resistor R5 and connected to the terminal 14 via a parallel circuit of the resistor R6 and the capacitor C4. These transistors Q3 and Q4, resistors R3 to R6,
The capacitor C4 constitutes the switch SW.

Next, the operation of this embodiment will be described.
First, when the control signal shown in FIGS. 2A and 6B is applied to the base of the transistor Q4 via the terminal 14 and the parallel circuit of the resistor R6 and the capacitor C4,
The transistor Q4 is turned on during the high level of the control signal, and the base-emitter of the transistor Q3 is forward biased by this, so that Q3 is also turned on.
Then, the terminal voltage (positive power supply voltage) of the capacitor C3 charged by the power supply voltage from the power supply terminal 15 is output to the capacitors C1 and C2 via the emitter and collector of the transistor Q3.

As a result, the capacitors C1 and C2 are charged with a time constant determined by their capacitance value and the bias resistors R1 and R2, and the charging is completed within a fixed time.
Broadband power amplifier 12 is in the active steady state. After this,
The transmission signals shown in FIGS. 2D and 6D, which are synchronized with the transmission synchronization signals shown in FIGS. 2C and 6C, are transferred to the transistors Q1 and Q2 via the transformer T1.
Is inputted to the base of the ultrasonic wave transducer SU, is amplified in power to have a large amplitude, and is outputted to the ultrasonic transducer SU via the transformer T2.

At the same time as the input of the transmission signal disappears, as described above, the control signal becomes low level, so that the transistor Q4 is turned off, which causes the transistor Q3.
Will also be off. When the transistor Q3 is turned off, the broadband power amplifier 12 is disconnected from the power supply terminal 15,
It will be stopped.

As described above, according to the present embodiment, the broadband power amplifier 12 is operated only in the period which is longer than the period in which the transmission signal is input by a predetermined time TD in synchronization with the transmission synchronization signal, and other periods. Since the power supply terminal is disconnected from the power supply terminal, the power consumption can be significantly reduced as compared with the conventional one, and therefore the power capacity of the wideband power amplifier 12 can be made extremely small, and the wideband power amplifier can be used. The element to be used has only to withstand pulse, and an element with low electric power can be used. From the above, according to the present embodiment, since the power capacity including the power source can be reduced, the heat radiation mechanism can be eliminated, and the ultrasonic flaw detector can be made smaller and cheaper than the conventional one. be able to.

Next, a second embodiment of the ultrasonic transmission circuit 11 will be described with reference to the concrete circuit diagram of FIG. In the figure,
The same components as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 7, the NPN transistor Q5 is a switching transistor whose collector has a resistor R
1, R2, bypass capacitor C1 and transformer T1
Connected to the common connection point of the center tap of the primary winding of
Further, its base is connected to the input terminal of negative voltage −V through the resistor R7 together with its emitter, while P
It is connected to the collector of the NP transistor Q6. The base of the transistor Q6 is connected to the power supply terminal 15 together with the emitter thereof via the resistor R8, and is connected to the control signal input terminal 14 via the resistor R9. Transistor Q6 is base biased by resistors R8 and R9 by a positive power supply voltage from power supply terminal 15. These transistors Q5 and Q6, resistor R7
~ R9 constitutes the switch SW.

Next, the operation of this embodiment will be described.
In the present embodiment, the high-level control signal is input to the input terminal 14 from a certain time before the time when the burst-shaped transmission signal is input to the terminals 13 and 13 ′ until the transmission signal is interrupted. Therefore, the transistor Q6 is turned off, which also turns off the transistor Q5. As a result, the positive power supply voltage from the power supply terminal 15 is divided by the resistors R1 and R2 and applied as a bias voltage to the bases of the transistors Q1 and Q2, so that the transistors Q1 and Q2 are in the operating state, For a long time, the wideband power amplifier 12 is in an operating state and is in a state where it can amplify the input transmission signal.

Then, at the same time that the transmission signal is interrupted, a low-level (voltage 0V) control signal is input to the input terminal 14, so that the transistor Q6 is turned on, which causes the transistor Q5 to be positive from the power supply terminal 15. The base-emitter is forward biased by the power supply voltage and turned on. This causes transistors Q1 and Q2 to
Since the base-emitter of the transistor is reverse-biased to the negative voltage -V caused by the emitter and collector of the transistor Q5, the transistors Q1 and Q2 are forcibly cut off and the wide band power amplifier 12 operates. It will be stopped. According to this embodiment, the switch SW
A device with a small power capacity can be used as.

The present invention is not limited to the above-mentioned embodiments, but it goes without saying that other switching elements such as thyristors can be used instead of the transistors Q3 to Q5 in the switch SW.

[0045]

As described above, according to the ultrasonic transmission circuit of the present invention, the power is always turned on by intermittently operating the amplification element in the transmission circuit in synchronization with the transmission synchronization signal. It is possible to reduce current consumption as compared with the conventional transmission circuit in the operating state. Therefore, compared with the conventional circuit, the power capacity of the wide band power amplifier in the transmission circuit can be made extremely small, and the heat dissipation mechanism can be eliminated. Therefore, the ultrasonic flaw detector can be made smaller, cheaper, and lighter in weight than conventional ones.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of an ultrasonic transmission circuit of the present invention.

FIG. 2 is a time chart of an example of the present invention.

FIG. 3 is an explanatory diagram of power consumption according to the present invention.

FIG. 4 is a specific circuit diagram of the first embodiment of the ultrasonic transmission circuit of the present invention.

FIG. 5 is a block diagram of an embodiment of an input side circuit of a transmission circuit.

FIG. 6 is a time chart for explaining the operation of FIG.

FIG. 7 is a specific circuit diagram of a second embodiment of the ultrasonic transmission circuit of the present invention.

FIG. 8 is a configuration diagram of an example of an ultrasonic measurement device.

FIG. 9 is a circuit diagram of an example of a conventional ultrasonic transmission circuit.

[Explanation of symbols]

 11 ... Transmission circuit 12 ... Wideband power amplifier 13 ... Transmission signal input terminal 14 ... Control signal input terminal 15 ... Power supply terminal 16 ... Transmission signal output terminal 23 ... Control oscillation circuit 24 ... Wave number control circuit Q1, Q2 ... NPN transistor for amplification Q3 , Q6 ... PNP transistor for switching Q4, Q5 ... NPN transistor for switching T1, T2 ... Transformer R1, R2 ... Resistors for bias C1, C2, C5 ... Bypass capacitor C3 ... Capacitor for power supply SU ... Ultrasonic transducer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Izumi Sato 2-16-46 Minami Kamata, Ota-ku, Tokyo Within Tokimec Co., Ltd.

Claims (1)

[Claims] 1. An ultrasonic transmission circuit for amplifying a transmission signal generated in synchronization with a transmission synchronization signal by an amplifying element, outputting the amplified signal to an ultrasonic transducer, and exciting the ultrasonic transducer to generate an ultrasonic wave. In the above, there is provided means for synchronizing the transmission synchronization signal, and for activating the amplification element for a period from immediately before a certain time from the leading edge time of the transmission synchronization signal to the trailing edge time of the transmission synchronization signal. An ultrasonic transmission circuit characterized by: