JPH0327870B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for transmitting and receiving ultrasonic waves by selectively exciting each element of an ultrasonic probe formed by arranging piezoelectric elements. In particular, it relates to a switch circuit for selecting piezoelectric elements.

[Conventional technology]

One-dimensionally arranged piezoelectric elements T _o (where n
= 1...L), M piezoelectric elements (hereinafter abbreviated as elements) from T _k to _{T K+M-1} are used to send out ultrasonic waves, and the reflected signals from the object are transmitted to the same element group. An ultrasonic imaging device that performs a reception operation by sequentially changing K is described in, for example, Japanese Patent Laid-Open No. 8557/1983.

[Problems to be solved by the invention] In such conventional ultrasound imaging devices,
A large number of switches are required to switch the high-voltage signals of about 200 volts used during wave transmission, and their control is also extremely difficult. Therefore, the present invention
To provide a piezoelectric element switching switch that is easy to control and has a simple configuration.

[Means and actions for solving problems]

The present invention is characterized in that a semiconductor element represented by a diode is used as the switch element, and a signal starting with a polarity corresponding to the forward direction of the element is applied to the input side of the switch element. According to such a configuration, selection and non-selection can be easily controlled by the bias voltage, and an alternating current waveform can be passed by utilizing the reverse recovery characteristics of the diode.

〔Example〕

Next, the general structure of the present invention will be explained with reference to FIG. Note that the figure shows a case where M=5 as an example.

A high voltage switch S _o is arranged for each of L elements T ₁ to T _L , and N elements (N≧2) adjacent to each other are arranged.
A control line C _n is placed to control the switches simultaneously. This control line C _{n Co} (n=(m-1)N+1, (m
-1)N+2,...mN) will be controlled simultaneously. Next, switch S ₁ combined in this way
~ Connect the output terminal a _o (where n=b+BR) of S _L to the common signal line G _b . Here, B is an integer greater than or equal to 0, and R is the total number of signal lines and is an integer greater than or equal to M+N-1. Also, b is an integer from 1 to R, and b
The maximum value of +BR becomes the total number L of piezoelectric elements.

In such a configuration, a switch connection signal is applied from the control circuit H to the control line C _n , and the control line C n including at least one of each of the simultaneously connected switches S _K to S _K+M-1 is connected to the control line C _n . All are driven simultaneously (FIG. 1 shows a state in which control lines C ₂ , C ₃ , and C ₄ are driven and switches S ₆ to _{S 10} are connected).

The selective driving operation of the piezoelectric element according to the configuration described above will be explained again using an example configuration in which L=20, M=5, and N=3. In Fig. 2, k is the transmission/reception number, and the transmission time t _k is the sound wave propagation time t _p (
200 μsec), there is a relationship t _k k·t _p .
Further, the total number of signal lines R is R≧7 because of the relationship R≧M+N-1, and FIG. 2 explains the case where R=7. Here, the x mark corresponds to the opening of the switch S _o by the control line C _n , and the ○ mark corresponds to the element number used simultaneously as one group.

As can be understood from the figure, by adopting such a configuration, the signal line G _b has the transmitting/receiving number k
The elements shown in FIG. 3 are connected to the elements corresponding to the numbers shown in FIG. Therefore, by using a commutator with a rotating head and a slip ring shown in Fig. 4, the signal line _Gb can be used cyclically, and M final output terminals can be connected.
Connections between H _o and the desired elements are made as shown in FIG. Further, it is also possible to directly connect the R number of wave transmitting signal sources to the signal line G _b without using such a commutator.

FIG. 6 shows a specific example of the configuration of the switch portion configured to perform the above operations. In the same figure, N=4, R=
8, and from the relationship M≦R−N+1, a configuration in which M=5 or less is shown.

In the above explanation, the structure in which the number R of signal lines is minimized has been explained, but by increasing the number of signal lines by one and making R≧M+N, the control of the control line C _n , that is, the switching operation, can be performed by t _p This allows more time to be given and reduces noise generation in the device. Also,
If R=iN (i is an integer greater than or equal to 2), the control line C _n
This becomes even simpler because the control circuit of the controller can take advantage of this relationship.

FIG. 7a shows a control circuit for supplying a signal to a switch section configured using such a diode. In this circuit, the signal voltage applied to the signal line G _b is in the negative direction, as shown in figure b.
That is, it starts with a direction of change that matches the polarity of the diode used as a switch. Any configuration can be used as long as the drive system emits a signal starting in such a direction of change. In addition, at the final stage of the control circuit H, for example, a high voltage control circuit shown in FIG. 8 is used, and when turning on the switch, the control line C _n is
-V when applying V _B (1V) and turning OFF
By applying (-200V), the switch can be opened and closed. Note that it is also possible to modify the basic circuit shown in FIG. 6 as shown in FIG. 9. Furthermore, it is also possible to change the polarities of the diode, control line C _n , and signal line G _b .

〔Effect of the invention〕

In this way, in the present invention, a semiconductor element represented by a diode is used as a switch, and by matching the polarity of the semiconductor element and the direction of change in voltage of the signal line _Gb as in the embodiment, the reverse recovery characteristics of the diode can be improved. This makes it possible to perform effective driving with an AC waveform using .

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of the basic configuration of the present invention, Fig. 2 is an explanatory diagram showing an example of operation when five piezoelectric elements are used simultaneously, and Fig. 3 is a correspondence between signal line numbers and piezoelectric element numbers. Figure 4 is a schematic cross-sectional view showing an example of a commutator that connects the signal line and the final output line, Figure 5 is the temporal change in the correspondence between the final output terminal and the piezoelectric element number. 6 is a circuit diagram showing a specific configuration example of a switch part using a diode, FIG. 7 is a circuit diagram showing an example configuration of a switch drive circuit, and FIG. 8 is a circuit diagram showing a configuration example of a switch drive circuit. FIG. 9 is a circuit diagram showing another example of the configuration of the switch portion shown in FIG. 6. FIG. T ₁ , T ₂ , ~ _{T L} ... piezoelectric element, S ₁ , S ₂ , ~S _L ...
...Switch, G ₁ , G ₂ , ~G _R ... Signal line.

Claims (1)

[Claims] 1 In a piezoelectric element switching switch circuit that selectively applies a drive signal to a plurality of piezoelectric elements constituting an ultrasonic probe, the characteristics of the diodes connected between the drive signal generation means and the plurality of piezoelectric elements are determined. 1. A switch circuit for switching a piezoelectric element, comprising a semiconductor element having a piezoelectric element, wherein the polarity of the semiconductor element matches the direction in which a signal generated by the drive signal generating means starts changing.