JP3492581B2 - Transmission circuit for ultrasonic diagnostic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit used in an ultrasonic diagnostic apparatus and supplying a driving pulse to the ultrasonic transducer.

[0002]

2. Description of the Related Art An ultrasonic diagnostic apparatus applies a voltage to a vibrator made of a piezoelectric material, transmits an ultrasonic wave generated thereby to a subject, and based on the reflected wave, the inside of the subject is examined. get information. In recent years, some ultrasonic diagnostic apparatuses have been developed which utilize the fact that nonlinear ultrasonic waves are generated in a subject by the transmitted ultrasonic waves. In such an apparatus using non-linear vibration, the difference between the spectrum of the transmitted ultrasonic wave and the reception spectrum containing the harmonic component of the transmission frequency generated by the non-linear vibration is used for measuring the subject.

The harmonic component generated by the non-linear vibration is generally weak. Therefore, in order to perform a measurement with a good S / N ratio in an ultrasonic diagnostic apparatus that detects and utilizes the harmonic component in the received wave, it is necessary to suppress the harmonic component contained in the transmitted wave itself. In response to this request, it is effective to excite the vibrator by using a drive pulse whose voltage changes symmetrically on the positive voltage side and the negative voltage side. Conventionally, in order to obtain a positive / negative symmetrical drive pulse, as described in Japanese Patent Application Laid-Open No. 9-234202, two power sources of a positive voltage and a negative voltage are used, and the positive voltage and the negative voltage are switched by a switch. The configuration is adopted in which the output is switched alternately.

FIG. 5 is a schematic circuit diagram of a conventional transmission circuit for an ultrasonic diagnostic apparatus that generates positive and negative symmetrical drive pulses.
The conventional circuit includes a voltage control unit 2 that is a drive power supply that supplies a positive voltage and a voltage control unit 4 that is a drive voltage that supplies a negative voltage.
It has and. The voltage control unit 2 is supplied with a voltage "+ HV0" from the outside, and the output voltage is adjusted by the + HV control signal. Similarly, the voltage control unit 4 is supplied with a voltage "-HV0" from the outside, and the output voltage is adjusted by the -HV control signal. The voltage control units 2 and 4 are adjusted by these control signals so that the absolute values of the output voltages become equal to each other, thereby obtaining drive pulses of equal amplitude in both positive and negative directions. Between the output end 8 to the oscillator and the voltage control unit 2 is M
A switch 10 composed of an OSFET (Q8) is provided, and a MOS is provided between the output terminal 8 to the vibrator 6 and the voltage control unit 4.
The switches 12 each composed of the FET (Q7) are provided. The output terminal 8 is configured to be groundable by a switch 14 composed of a MOSFET (Q9).

During transmission, the switch 14 is turned off and the switches 10 and 12 are switched alternately. As a result, the output terminal 8 outputs a drive pulse that varies positively or negatively according to the output voltage of the voltage control units 2 and 4. By the way,
At the time of reception, the switch 14 is turned on and the output end 8 is grounded.

[0006]

The conventional transmission circuit for generating positive and negative symmetric drive pulses requires two drive power supplies. Therefore, there is a problem that the structure of the transmission circuit becomes complicated, the scale becomes large, and the manufacturing cost becomes high. In addition, in a conventional ultrasonic diagnostic apparatus that does not use nonlinear vibration, it is general to use a transmission circuit that outputs a driving pulse of one polarity, but by modifying this, ultrasonic diagnosis for nonlinear vibration is performed. When it is used as a device, there is a problem that it is difficult to modify it because it requires a new power source.
Furthermore, since the amplitude on the positive side and the amplitude on the negative side depend on the output voltage of each of the positive and negative power supplies, there is a problem that the positive / negative symmetry of the drive pulse is not always stable due to the fluctuation of the output voltage of the power supplies. Further, in order to obtain a positive / negative symmetrical drive pulse, it is necessary to adjust the output voltage of each positive and negative power source, which is complicated.

The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a transmission circuit which can obtain a stable positive / negative symmetrical drive pulse with a simpler structure.

[0008]

An ultrasonic diagnostic apparatus transmission circuit according to the present invention is a transmission circuit for supplying a driving pulse to an ultrasonic transducer connected to an output terminal, and a driving power source having a predetermined polarity. A first switch section that switches between a first on state in which the output terminal and the drive power supply are connected and a first off state in which the output terminal and a reference potential are connected, and the output terminal via a capacitor A second switch section connected to the second switch section for switching between a second on state in which the capacitor and the driving power source are connected and a second off state in which the capacitor and the reference potential are connected to each other; A first switch switching operation of controlling the second switch unit to switch the first switch unit from the first off state to the first on state and then to the first off state again; and the second switch. Switching the switch portion from the second on-state to the second OFF state, and has a switch control unit for alternating a second switch switching operation for switching back to the second ON state.

According to the present invention, positive and negative drive pulses are generated using a single drive power supply. The switch control unit switches the first switch unit from its off state to its on state and then to the off state again,
The output terminal of the transmission circuit is sequentially connected to the reference potential, the driving power supply, and the reference potential again through the first switch section.
Correspondingly, the voltage at the output terminal sequentially changes to the reference potential, the output voltage of the drive power supply, and the reference potential again, and a pulse having the same polarity as the drive power supply is output. On the other hand, the switch control unit switches the second switch unit from its ON state to its OFF state, and then switches it to the ON state again, so that the output end of the transmission circuit sequentially passes through the capacitor and the second switch unit to drive power supply. , Reference potential, and again connected to drive power supply. A capacitor is interposed between the second switch section and the output terminal, and the two are capacitively coupled. Therefore, the voltages of the driving power supply and the reference power supply to which the input of the second switch section is connected do not directly appear at the output end. In particular,
At the start of the series of operations of the second switch section,
The first switch section is in the off state. That is, at the start, the input of the second switch unit is connected to the drive power supply, the potential of the second switch unit side of the capacitor is set to the output voltage of the drive power supply, and the potential of the transmission circuit output end side of the capacitor is set. Is set to the reference potential via the first switch section. In this state, when the second switch section is turned off, the potential on the second switch section side of the capacitor fluctuates to the reference potential, so that the second end is capacitively coupled to the second end.
Potential fluctuations of the same polarity as the switch portion side and basically of the same width appear. Also, when the second switch section is returned to the ON state again, the output terminal has the same polarity as the second switch section side as the potential of the second switch section side of the capacitor is restored to the output voltage of the driving power supply. However, basically, the potential fluctuation of the same width appears. In this way, the potential of the output terminal changes in order of the reference potential, the output voltage of the driving power supply, and the reference potential according to the second switch switching operation,
A pulse having a polarity opposite to that of the pulse generated by the first switch switching operation and having the same absolute value of amplitude is output.
According to the present invention, by alternately performing the first switch switching operation and the second switch switching operation, a pulse swinging to the positive side with the reference potential as the center and a pulse swinging to the negative side with the same amplitude as that of the reference potential alternate. Is output from the output end to the vibrator.

In the ultrasonic diagnostic apparatus transmission circuit according to another aspect of the present invention, the switch control section performs the first switch switching operation and the second switch switching operation the same number of times each.

According to the present invention, the positive swing pulse and the negative swing pulse are alternately output by the same number, and positive and negative symmetrical drive pulses are obtained.

In the ultrasonic diagnostic apparatus transmission circuit according to another aspect of the present invention, the switch control unit equalizes a period of the first switch switching operation and a period of the second switch switching operation. To do.

According to the present invention, the width of the pulse oscillating on the positive side and the width of the pulse oscillating on the negative side are equal to each other, and a drive pulse having positive and negative symmetry with respect to the pulse width can be obtained.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, preferred embodiments of a transmission circuit according to the present invention will be described with reference to the drawings. Figure 1
FIG. 3 is a schematic block configuration diagram of an ultrasonic diagnostic apparatus using a transmission circuit according to the present invention. The device has a transmitter circuit 52 that drives a number of transducers included in the probe 50. The transmission circuit 52 includes a plurality of transmission drive circuits 54 corresponding to each transducer and a transmission control circuit 56 common to them. Each transmission drive circuit 54 has a transmission control circuit 56.
In response to an instruction from, the ultrasonic waves are transmitted from the transducers assigned to each. The transmission control circuit 56 includes the transmission drive circuit 54.
The opening and closing of the FET switch included in the transmission control circuit 54 controls the transmission drive circuit 54 to generate a pulse for driving the vibrator. Further, the transmission control circuit 56 controls the transmission delay amount of the ultrasonic wave between the transducers by adjusting the generation timing of the drive pulse between the transmission drive circuits 54, and the ultrasonic wave is moved to a desired position in the living body. It also has the function of focusing on.

On the other hand, at the time of reception, the reception signal from each transducer of the probe 50 is amplified by the preamplifier 60 and then input to the reception delay circuit 62. Reception delay circuit 6
2, the delay amount for the received signal can be variably set for each channel corresponding to each preamplifier 60. The delay amount is controlled by the reception delay control circuit 64, and the reception signals of the respective channels are delayed and then added to each other. The reception delay control circuit 64 is
The delay amount is adjusted so as to change the focus point in multiple steps in the depth direction with respect to one reception direction, and thereby dynamic focus is realized. The two-dimensional appearance of the cross section of the living body in the array direction can be observed by the images obtained by this scanning that changes the focus point in the depth direction and the scanning that changes the reception direction.

The added reception signal is input to the reception processing circuit 66. The reception processing circuit 66 performs processing such as detection of a harmonic component due to non-linear vibration in the subject. The reception data extracted by the reception processing circuit 66 from the reception signal is converted into an ADC (analog-to-digital converter) circuit 68.
Converted into digital signal by DSC (digital sc
an converter) 70. The DSC 70 stores, for example, received data for one screen obtained by electronic scanning, and outputs the accumulated data in an order according to the scanning method of the display device 72. In other words, since the scanning order of the electronic scanning of each point on the biological cross section by the probe 50 is generally different from the scanning order of the display device 72, the conversion between the two scanning methods is performed using the DSC 70. DAC (digital-to-a
nalog converter) 74 is a display device 72 from the DSC 70
The digital values sequentially read according to the scanning method of 1 are converted into analog image signals, and the display device 72 displays them as images.

The system control circuit 76 is a circuit for controlling the transmission control circuit 56, the reception delay control circuit 64, and the DSC 70.

The characteristic of this apparatus is the transmission circuit 52. FIG. 2 is a circuit diagram showing a schematic configuration of the transmission circuit 52. This figure shows the configuration of the transmission control circuit 56 and one transmission drive circuit 54 for simplification. A voltage controller 80 is provided as a driving power source. The voltage control unit 80
The voltage "+ HV0" is supplied from the external power supply, and the voltage "+ HV" according to the + HV control signal is generated and output. The voltage control unit 80 and the output end 82 of the transmission drive circuit 54 are connected in parallel by the two switch units 84 and 86.

The first switch section 84 is an FET switch (Q1) for turning on / off between the ground which is the reference potential and the output terminal 82, and an on / off switch between the voltage control section 80 and the output terminal 82. And an FET switch (Q2) for switching. As will be described later, the switching operation of the FET switches Q1 and Q2 of the switch unit 84 is performed in order to generate a positive voltage pulse at the output end 82. This switching operation is performed based on the control signal input from the transmission control circuit 56. The amplitude of this control signal is adjusted by the amplifier IC1, and Q1,
The gate potential of Q2 is controlled to switch ON / OFF of Q1 and Q2.

Here, Q1 is an n-channel MOSFET
, Whose gate is directly connected to the output of IC1. Further, a diode D1 is arranged between Q1 and the output end 82 to prevent a negative voltage pulse from being applied to Q1. On the other hand, Q2 is composed of a p-channel MOSFET, the gate of which is connected to the output of IC1 via the capacitor C1 and to the output of the voltage control unit 80 via the resistor R1. Q2 is configured to be in an off state when its gate voltage is the output voltage "+ HV" of the voltage controller 80.

From the transmission control circuit 56 to each switch section 84,
The control signal to 86 has a binarized voltage level of "High" level (hereinafter, H level) and "Low" level (hereinafter, L level). For example, TTL (Transistor
In Transistor Logic, the L level is set to 0V and the H level is set to 5V. Corresponding to the configuration of the switch section 84, during the period in which the positive voltage pulse is not generated at the output terminal 82, the H level is input from the transmission control circuit 56 to the IC1 and at the timing at which the positive voltage pulse is generated at the output terminal 82. Is input at L level.

Next, the output of the second switch section 86 is capacitively coupled to the output end 82 by the capacitor C2. The switch unit 86 has a reference potential of ground and a capacitor C2.
And an FET switch (Q3) for turning on / off the switch and a FET switch (Q4) for turning on / off the voltage control unit 80 and the capacitor C2. As will be described later, in order to generate a pulse of a negative voltage at the output end 82, the switching operation of the FET switches Q3 and Q4 of the switch section 86 is performed. This switching operation is performed based on the control signal input from the transmission control circuit 56, as in the switch section 84. The amplitude of this control signal is adjusted by the amplifier IC2, and the gate potentials of Q3 and Q4 are controlled to switch ON / OFF of Q3 and Q4.

Here, Q3 is an n-channel MOSFET
, Whose gate is directly connected to the output of IC2. On the other hand, Q4 is composed of p-channel MOSFET,
Its gate is connected to the output of IC2 via a capacitor C3, and a predetermined potential "VG" for turning on Q4 is applied via a resistor R2. A diode D2 is arranged between Q4 and the capacitor C2 to prevent a positive voltage pulse from being applied to Q4.

Corresponding to the configuration of the switch section 86, during the period in which the negative voltage pulse is not generated at the output terminal 82, the L level is input from the transmission control circuit 56 to the IC2 and the negative voltage pulse is generated at the output terminal 82. The H level is input at the timing.

The output end 82 is provided with a pair of diodes D3 and D4 connected in parallel in opposite directions. This is a structure for protecting the received signal from the output terminal 82 which is short-circuited to the ground via Q1. Since the received signal is a small signal, it can be isolated from Q1 by the junction potential difference of the diode.

Next, the operation of the transmission circuit 52 will be described. FIG. 3 is a time chart for explaining the control signal output from the transmission control circuit 56 and the voltage change of the drive pulse generated at the output end 82. Figure 3 (a)
Is a control signal SG1 input from the transmission control circuit 56 to the amplifier IC1, a control signal SG2 input to the amplifier IC2 from the transmission control circuit 56, and a control signal SG2 input to the amplifier IC2 from the transmission control circuit 56. The drive pulses that appear are shown respectively. Hereinafter, a time series will be described based on this figure.

Before the drive pulse is generated (time t <t
In 1), the control signal SG1 is at H level and the control signal SG2 is at L level. By setting SG1 to the H level, Q1 is controlled to be on and Q2 is controlled to be off. That is, the first switch portion 84 is in a state (first off state) in which the output end 82 and the ground, which is the reference potential, are connected. As a result, the potential of the output end 82 becomes 0V which is the ground potential. By the way, by setting SG2 to the L level, Q3 is controlled to the off state and Q4 is controlled to the on state. That is, the second switch unit 86 includes the capacitor C
2 and the output of the voltage control unit 80 are connected (second ON state).

When the control signal SG2 is changed to the H level at time t1, Q3 is changed to the ON state. Also IC2
The potential of the gate of Q4, which is capacitively coupled to, rises by "ΔV2" according to the fluctuation of the output voltage of IC2. Potential "V
G "can be set so that the p-channel FET Q4 is turned off at the potential" VG + ΔV2 ". By making such setting, Q4 changes to the off state at time t1. , The second switch portion 86
Is a state in which the capacitor C2 and the ground are connected (second
Change to the off state).

When the second switch section 86 transitions from the second ON state to the second OFF state, the potential of the capacitor C2 on the switch section 86 side changes from "+ HV" to 0V. As a result, the potential on the opposite side of the capacitor C2 is 0V.
To "-HV". At this time, since the diode D1 is in the reverse bias state, the change in the potential on the opposite side of the capacitor C2 is not absorbed by the ground via Q1. That is, at time t1, the potential of the output terminal 82 changes to "-HV".

When the control signal SG2 is returned to the L level again at the time t2, the potential of the output terminal 82 is also restored to 0V. Thus, in response to the pulse 100 of SG2, the negative voltage pulse 102 is generated at the output end 82.

When the control signal SG1 is changed to the L level at the time t3, Q1 is changed to the off state. Also IC1
The potential of the gate of Q2, which is capacitively coupled to, decreases by "ΔV1" in accordance with the fluctuation of the output voltage of IC1. Potential “Δ
V1 "is a p-channel FET at the potential" HV-ΔV1 "
Can be set to turn on. With this setting, Q2 changes to the on state at time t3. That is, the first switch unit 84
Changes to a state (first ON state) in which the output end 82 and the voltage control unit 80 are connected.

When the first switch section 84 transits from the first off state to the first on state, the potential of the output terminal 82 changes from 0V to "+ HV". At this time, the diode D2 is reverse-biased, which causes Q4
It is prevented that a positive pulse is applied to.

When the control signal SG1 is returned to the H level again at time t4, the potential of the output terminal 82 is also restored to 0V. Thus, the positive voltage pulse 106 is generated at the output end 82 in response to the pulse 104 of SG1.

FIG. 3 shows a case where the above-described operation of t = t1 to t4 is repeated at t = t5 to t8 to generate two positive and negative voltage pulses, but the number of positive and negative voltage pulses is set. Can be one set, or three or more sets. The positive and negative voltage pulses are output to the vibrator connected to the output end 82, and ultrasonic waves are generated and transmitted.

Actually, the pulse of SG1 and SG2
Pulse can be switched at substantially the same time.
That is, for example, the end timing t2 of the pulse 100 of SG2 and the start timing t3 of the pulse 104 of SG1 are set to t2≈t3, and the end timing t4 of the pulse 104 of SG1 and the start timing t5 of the pulse 108 of SG2 are set to t4≈t5. To be done. as a result,
As a drive pulse output from the transmission circuit 52 to the vibrator, as shown in FIG. 4, a positive voltage “+ HV” and a negative voltage “−H” are given.
It is possible to obtain a signal waveform that smoothly changes between V ″ and V ″.

According to the present transmission circuit 52, as described above, the drive pulse having the same amplitude on the positive side and the negative side and having the same symmetry that is swung by the same number of times on the positive side and the negative side is obtained, and the harmonics contained therein are obtained. Wave components are suppressed. Furthermore, by making the width of the positive voltage pulse equal to the width of the negative voltage pulse, the symmetry of the drive pulse is further improved, and the effect of further suppressing harmonic components can be obtained. This can be realized by making the pulse width of SG1 equal to the pulse width of SG2.

[0037]

According to the transmission circuit for an ultrasonic diagnostic apparatus of the present invention, it is possible to generate drive pulses oscillating in positive and negative symmetry with one drive power source, and there is an effect that the circuit configuration is simplified. Further, since the positive-side amplitude and the negative-side amplitude are determined by one drive power supply, the symmetry of the amplitude is stable, and the adjustment work to make them equal is unnecessary.

[Brief description of drawings]

FIG. 1 is a schematic block configuration diagram of an ultrasonic diagnostic apparatus using a transmission circuit according to the present invention.

FIG. 2 is a circuit diagram showing a schematic configuration of a transmission circuit according to the present invention.

FIG. 3 is a time chart for explaining a control signal output from a transmission control circuit and a voltage change of a drive pulse generated at an output end of the transmission circuit.

FIG. 4 is a schematic diagram showing a signal waveform of a drive pulse generated at an output end of a transmission circuit.

FIG. 5 is a schematic circuit diagram of a conventional ultrasonic diagnostic apparatus transmission circuit that generates positive and negative symmetrical drive pulses.

[Explanation of symbols]

50 probe, 52 transmission circuit, 54 transmission drive circuit, 56 transmission control circuit, 62 reception delay circuit, 64
Reception delay control circuit, 66 reception processing circuit, 80 voltage control section, 82 output terminal, 84, 86 switch section.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-231247 (JP, A) JP-A-7-336198 (JP, A) JP-A-9-234202 (JP, A) JP-A-9- 304512 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) A61B 8/00

Claims (3)

(57) [Claims] 1. A transmission circuit for supplying a drive pulse to an ultrasonic transducer connected to an output end, the drive power supply having a predetermined polarity, and a first ON state in which the output end and the drive power supply are connected. A first switch section for switching between a first off state in which the output terminal and a reference potential are connected, and a second switch section connected to the output terminal via a capacitor and connecting the capacitor and the driving power supply A second switch section that switches between an on state and a second off state in which the capacitor and the reference potential are connected to each other; and the first switch section and the second switch section are controlled so that the first switch section is A first switch switching operation of switching from a first off state to the first on state and again to the first off state, and switching the second switch section from the second on state to the second off state. ,
A switch control unit for alternately performing a second switch switching operation for switching to the second ON state again, and a transmission circuit for an ultrasonic diagnostic apparatus, comprising: 2. The ultrasonic diagnostic apparatus transmission circuit according to claim 1, wherein the switch control unit performs the first switch switching operation and the second switch switching operation the same number of times each. Transmission circuit for ultrasonic diagnostic equipment. 3. The ultrasonic diagnostic apparatus transmission circuit according to claim 1, wherein the switch control unit equalizes a period of the first switch switching operation and a period of the second switch switching operation. A transmission circuit for an ultrasonic diagnostic apparatus, characterized in that