JP2010022761A - Ultrasonic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic imaging apparatus capable of suppressing the loss of power generated when the output voltage of electric signals for driving a piezoelectric element is changed. <P>SOLUTION: Since diodes D7 and D8 and resistances R7 and R8 connected to intermediate driving voltage ±HVL as a power saving means are connected to an output line 1 of a multi-level pulsar 33, the steady consumption of electric currents generated by the multi-level pulsar 33 is eliminated. As a result, the power consumption can be suppressed low, and heat generation in the multi-level pulsar 33 can be reduced. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic imaging apparatus including a transmission unit that generates an electric signal for driving a piezoelectric element.

  In recent years, in an ultrasonic imaging apparatus, a burst waveform including a plurality of identical waveforms is used as an electric signal for driving a piezoelectric element that generates ultrasonic waves (see Patent Document 1). This burst waveform has a frequency of about 3 to 10 MHz that matches the resonance frequency of the piezoelectric element, and has an amplitude voltage of around 100V. Since the number of simultaneously driven piezoelectric elements is several tens of channels, and the ultrasonic imaging apparatus is characterized by being compact, the transmitter that generates these burst waveforms is A simple configuration is preferable.

As a transmission unit having a simple configuration that generates a burst waveform, there is a multi-level pulser in which push-pull circuits having different power supply voltages are connected in parallel. This multi-level pulsar can easily generate a burst waveform composed of a pseudo sine wave that approximates a sine wave by switching the output voltage stepwise by turning on and off the push-pull circuit.
JP 2000-005169 A (page 1, FIG. 7)

  However, according to the above-described background art, power loss occurs when the output voltage is switched in a stepwise manner. That is, when the output voltage of the multi-level pulser is switched, charging / discharging of the charge charged in the piezoelectric element having capacitive electric characteristics occurs. This charging / discharging occurs with the grounding resistance connected in parallel to the capacitive piezoelectric element, and causes power loss.

  In particular, this power loss causes heat generation, and cannot be ignored for an ultrasonic imaging apparatus that performs multi-channel driving.

  The present invention has been made in order to solve the above-described problems caused by the background art, and an ultrasonic wave capable of suppressing power loss generated when switching the output voltage of an electric signal for driving a piezoelectric element to a low level. An object is to provide an imaging device.

  In order to solve the above-described problems and achieve the object, an ultrasonic imaging apparatus according to a first aspect of the invention is an ultrasonic imaging apparatus that supplies a predetermined voltage to a piezoelectric element and transmits ultrasonic waves. A pulsar having an output line connected to the piezoelectric element and a plurality of push-pull circuits connected to the output line, and having a plurality of power supply voltages having different sizes in the plurality of push-pull circuits. A first rectifying element that includes a power supply unit that supplies power, and wherein at least one of the plurality of push-pull circuits prevents reverse current from flowing through a complementary transistor included in the push-pull circuit. The pulser further includes power saving means including a second rectifying element and a resistor, and the second rectifying element constituting the power saving means and Serial resistance is characterized by connecting the output line to the power supply voltage supplied to the push-pull circuit having a first rectifier element.

  In the invention according to the first aspect, the pulsar connects the power supply voltage supplied to the push-pull circuit having the first rectifier element and the output line by the power saving means including the rectifier element and the resistor.

  The ultrasonic imaging apparatus according to the invention of the second aspect is the ultrasonic imaging apparatus according to the first aspect, wherein the power supply unit is output to the push-pull circuit. A voltage is generated.

  In the invention of the second aspect, a voltage waveform that vibrates positively and negatively about the ground potential is generated.

  An ultrasonic imaging apparatus according to a third aspect of the invention is the ultrasonic imaging apparatus according to the second aspect, wherein the pulser has a ground circuit for turning on / off the connection between the output line and the ground terminal. It is characterized by providing.

  In the invention of the third aspect, when the output part of any push-pull circuit is in a floating state, the output line is set to the ground potential.

  The ultrasonic imaging apparatus according to the invention of the fourth aspect is the ultrasonic imaging apparatus according to any one of the first to third aspects, wherein the power saving means connects the output line to the power supply. It is characterized in that it is connected to at least one power supply voltage that is not the maximum among the plurality of power supply voltages output by the unit.

  In the invention according to the fourth aspect, power consumption is reduced when the voltage of the electric signal shifts from the maximum drive voltage at the maximum to a voltage not at the maximum.

  The ultrasonic imaging apparatus according to the fifth aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to fourth aspects, wherein the power saving means divides the power supply voltage. A voltage dividing means connected to the output line is provided.

  In the fifth aspect of the invention, the magnitude of the voltage connected to the output line is made smaller than the magnitude of the power supply voltage to change the voltage of the electric signal at high speed.

  The ultrasonic imaging apparatus according to the invention of the sixth aspect is the ultrasonic imaging apparatus according to any one of the first to fifth aspects, wherein the ultrasonic imaging apparatus is configured by the plurality of push-pull circuits. And a pulsar control unit that operates the plurality of push-pull circuits so that a pseudo sine wave that approximates a rectangular wave or a sine wave is output to an output line.

  In the invention of the sixth aspect, a burst waveform of a rectangular wave or a pseudo sine wave is generated by a control signal from the pulsar control unit.

  The ultrasonic imaging apparatus according to the seventh aspect of the invention is the ultrasonic imaging apparatus according to any one of the first to sixth aspects, wherein the pulser includes the power saving means, Connection switching means for switching between connection and disconnection with a power supply voltage supplied to a push-pull circuit having a rectifying element is provided.

  In the seventh aspect of the invention, the power saving means is enabled or disabled by the connection switching means.

  The ultrasonic imaging apparatus according to the invention of the eighth aspect is the ultrasonic imaging apparatus according to the seventh aspect, wherein the connection switching means is configured to save the power when the electrical signal is a rectangular wave. Is connected to the power supply voltage having the maximum magnitude among the plurality of power supply voltages, or is not connected to any of the plurality of power supply voltages.

  In the invention according to the eighth aspect, the connection switching means makes the power saving means in an ineffective state when the electric signal is a rectangular wave.

  The ultrasonic imaging apparatus according to the ninth aspect of the invention is the ultrasonic imaging apparatus according to the seventh aspect, wherein the connection switching means is configured to output the output line when the electrical signal is a pseudo sine wave. Is connected to at least one of the plurality of power supply voltages having a maximum magnitude.

  In the ninth aspect of the invention, the connection switching means is brought into an effective state in which the power saving means operates when the electrical signal is a pseudo sine wave.

  According to the present invention, power consumption can be kept low because consumption of a steady current generated by a pulser that generates a pseudo sine wave is eliminated, and thus heat generation can be reduced.

  The best mode for carrying out an ultrasonic imaging apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that the present invention is not limited thereby.

(Embodiment 1)
First, the overall configuration of the ultrasonic imaging apparatus 100 according to the first embodiment will be described. FIG. 1 is a block diagram showing the overall configuration of the ultrasonic imaging apparatus 100 according to the first embodiment. The ultrasonic imaging apparatus 100 includes an ultrasonic probe 10, an image acquisition unit 102, an image memory unit 104, an image display control unit 105, a display unit 106, an input unit 107, and a control unit 108.

  The ultrasonic probe 10 incorporates a piezoelectric element array and transmits and receives ultrasonic waves. The ultrasonic probe 10 that is in close contact with the surface of the subject 2 irradiates the imaging section with ultrasonic waves, and uses ultrasonic echoes (echo) reflected from the inside of the subject 2 as time-series sound rays. Receive. The ultrasonic probe 10 performs electronic scanning while sequentially switching the irradiation direction of ultrasonic waves.

  The image acquisition unit 102 generates an electric signal for driving the piezoelectric element array of the ultrasonic probe, and performs a B-mode process or a Doppler process from the electric signal received by the piezoelectric element array. Information or Doppler image information is formed. Detailed functions of the image acquisition unit 102 will be described later.

  The image memory unit 104 includes a large-capacity memory, and stores two-dimensional tomographic image information, cine image information that is time-varying two-dimensional tomographic image information, and the like.

  The image display control unit 105 performs display frame rate conversion of the B-mode image information generated by the B-mode process and the blood flow image information generated by the Doppler process, and controls the shape and position of the image display. Do.

  The display unit 106 includes a CRT (Cathode Ray Tube), an LCD (Liquid Crystal Display), or the like, and displays a B-mode image or a blood flow image.

  The input unit 107 includes a keyboard or the like, and operation information is input by an operator. The input unit 107 receives, for example, operation information for selecting display in B mode or display of Doppler processing, operation information for setting a Doppler imaging region for performing Doppler processing, and the like.

  The control unit 108 controls the operation of each unit of the ultrasonic imaging apparatus including the above-described ultrasonic probe based on the operation information input from the input unit 107 and a program (program) and data (data) stored in advance.

  FIG. 2 is a block diagram illustrating a configuration of the image acquisition unit 102. The image acquisition unit 102 includes a transmission beamformer 21, a transmission unit 22, a reception unit 23, a reception beamformer 24, a B-mode processing unit 25, and a Doppler processing unit 26. Based on the information from the control unit 108, the transmission beamformer 21 generates a drive signal having a predetermined delay time so as to perform electronic focusing at the focal depth position.

  The transmission unit 22 forms a burst waveform that drives the piezoelectric element of the ultrasonic probe 10 based on the drive signal from the transmission beamformer 21. The transmitter 22 will be described in detail later.

  The receiving unit 23 performs first-stage amplification of the electrical signal received by the piezoelectric element of the ultrasonic probe 10. The reception beamformer 24 performs delay addition by adding a predetermined delay time similar to that at the time of transmission to the electrical signal received by the reception unit 23 to form an electrical signal on the sound ray.

  The B-mode processing unit 25 performs processing such as logarithmic conversion and filter processing on the electrical signal on the sound ray subjected to the delay addition to form a B-mode image. The Doppler processing unit 26 performs quadrature detection, filter processing, and the like on the electrical signal on the sound ray subjected to delay addition, and displays blood flow information in the subject 2 as frequency spectrum information or CFM (Color Flow Mapping) information. To do.

  FIG. 3 is a block diagram illustrating a configuration of the transmission unit 22. The transmission unit 22 includes a pulsar power supply unit 31, a pulsar control unit 32, and a plurality of multi-level pulsars 33. The pulsar control unit 32 causes the multi-level pulsar 33 to generate a pseudo sine wave based on the drive signal from the transmission beamformer 21. The control signal generated by the pulsar control unit 32 and causing the multilevel pulsar 33 to generate a pseudo sine wave will be described later.

  The pulsar power supply unit 31 is a high-voltage power supply unit configured using a switching regulator or the like. The pulsar power supply unit 31 has positive and negative maximum drive voltages + HVH and −HVH corresponding to the maximum amplitude of the generated pseudo sine wave, and positive and negative intermediate drive voltages + HVL and −VH having approximately half the maximum drive voltage ± HVH. Generate HVL.

  The multi-level pulsar 33 generates a pseudo sine wave based on the control signal from the pulsar control unit 32. FIG. 4 is a circuit diagram showing a configuration of the multilevel pulsar 33. The multi-level pulsar 33 includes an output line (line) 1 connected to the piezoelectric element 11, transistors Q1 to Q6, diodes D1 to D8, D30 and D40, resistors R1 to R4, R7 and R8, and a capacitor. (Capacitor) including C1-C4.

  The transistors Q1 to Q6 include Q1, Q3, and Q5 using a P-channel FET (Field Effect Transistor) and Q2, Q4, and Q6 using an N-channel FET.

  The transistors Q1 and Q2 constitute one push-pull circuit, and the connection between the positive and negative power supply voltage ± HVH, which is the maximum drive voltage connected to the source terminals of Q1 and Q2, and the output line 1 is connected to the transistor Q1. And Q2 on / off control. An electric signal for turning on and off the transistors Q1 and Q2 is formed by the pulsar control unit 32, and is input to the gate terminals of Q1 and Q2 via capacitors C1 and C2 that perform AC coupling. Resistors R1 and R2 and protection diodes D1 and D2 are connected between the gate terminals of the transistors Q1 and Q2 and the source terminal to determine the operating potential of the gate terminal and to perform overvoltage protection. The drain terminals of the transistors Q1 and Q2 are connected to each other and form an output part of the push-pull circuit. This output unit is connected to the output line 1.

  Transistors Q3 and Q4 constitute a push-pull circuit, and connection between positive and negative power supply voltage ± HVL, which is an intermediate drive voltage connected to the source terminals of Q3 and Q4, and output line 1 is determined by turning transistors Q3 and Q4 on and off. Control. An electric signal for turning on and off the transistors Q3 and Q4 is formed by the pulsar control unit 32, and is input to the gate terminals of Q3 and Q4 via capacitors C3 and C4 that perform AC coupling. Resistors R3 and R4 and protective diodes D3 and D4 are connected between the gate terminals of the transistors Q3 and Q4 and the source terminal, thereby determining the operating potential of the gate terminal and overvoltage protection.

  The drain terminals of the transistors Q3 and Q4 are connected to each other via diodes D30 and D40 which are first rectifier elements, and this connection portion forms an output portion of the push-pull circuit. This output unit is connected to the output line 1. In the diode D30, when the voltage of the output line 1 becomes higher than the voltage + HVL of the source terminal of the transistor Q3, a reverse current that flows toward the supply side of the voltage + HVL (the pulsar power supply unit 31 side) flows to the transistor Q3. To prevent. The diode D40 prevents reverse current flowing toward the output line 1 from flowing into the transistor Q4 when the voltage of the output line 1 becomes lower than the voltage −HVL of the source terminal of the transistor Q4.

  Transistors Q5 and Q6 form a ground circuit that controls connection between the ground terminal and output line 1 by turning on and off transistors Q5 and Q6. A control signal for turning on and off the transistors Q5 and Q6, which are ground circuits, is formed by the pulser controller 32.

  A diode D7 and a resistor R7, which are second rectifier elements, are connected in series between the power supply voltage + HVL and the output line 1. The diode D7 is arranged in such a direction that current flows when the voltage of the output line 1 becomes higher than the power supply voltage + HVL. The diode D8 and the resistor R8, which are the second rectifier elements, are connected in series between the power supply voltage -HVL and the output line 1. The diode D8 is arranged in a direction in which a current flows when the voltage of the output line 1 becomes lower than the power supply voltage -HVL. In the present invention, the diode D7 and the resistor R7, and the diode D8 and the resistor R8 constitute power saving means for connecting the output line to the power supply voltage supplied to the push-pull circuit having the first rectifying element. Will be described in detail later.

  Control signals from the pulser control unit 32 for the transistors Q1 to Q6 of the multilevel pulser 33 are represented by DVPH, DVNH, DVPL, DVNL, CPP and CPN, respectively. In these character strings, DV is an abbreviation for Drive, N is an N channel, P is a P channel, H is a maximum drive voltage HVH, and L is an intermediate drive voltage HVL.

  Next, the operation of the multilevel pulsar 33 will be described with reference to FIGS. FIG. 5 is a diagram illustrating a time change of a control signal for driving the transistors Q1 to Q6 of the multilevel pulsar 33 and a pseudo sine wave to be output. The horizontal axis represents the time axis, and the vertical axis represents the voltage. Note that the diagrams shown in FIGS. 5A and 5B have a common time axis.

  Here, the control signals DVPL, DVPH, and CPP of Q3, Q1, and Q5 using the P-channel FET are L level, which is a low voltage level, the transistor is turned on, and the voltage is high. At a certain H level, the transistor is turned off. Further, the control signals DVNL, DVNH, and CPN of Q2, Q4, and Q6 using the N-channel FET are at the L level that is a low voltage level, the transistor is turned off, and at the H level that is the high voltage level. The transistor is turned on.

  In FIG. 5A, first, the control signal DVPL is set to L level, and the transistor Q3 is turned on (step 1). At this timing, the intermediate drive voltage + HVL is output as the output voltage as shown in step 1 of FIG.

  Thereafter, the control signal DVPL is set to H level, the transistor Q3 is turned off, and simultaneously, the control signal DVPH is set to L level, and the transistor Q1 is turned on (step 2). At this timing, the maximum drive voltage + HVH is output as the output voltage as shown in Step 2 of FIG.

  Thereafter, the control signal DVPH is set to H level, the transistor Q1 is turned off, and at the same time, the control signal DVPL is set to L level, and the transistor Q3 is turned on (step 3). At this timing, as shown in step 3 of FIG. 5B, the intermediate drive voltage + HVL is output as the output voltage.

  Thereafter, the control signal DVPL is set to H level, the transistor Q3 is turned off, and simultaneously, the control signal CPN is set to H level, and the transistor Q6 is turned on (step 4). At this timing, the ground potential is output as the output voltage as shown in step 4 of FIG.

  Thereafter, CPN of the control signal is set to L level, the transistor Q6 is turned off, and simultaneously, DVNL of the control signal is set to H level, and the transistor Q4 is turned on (step 5). At this timing, as shown in step 5 of FIG. 5B, the negative intermediate drive voltage −HVL is output as the output voltage.

  Thereafter, the control signal DVNL is set to L level, the transistor Q4 is turned off, and simultaneously, the control signal DVNH is set to H level to turn on the transistor Q2 (step 6). At this timing, the negative maximum drive voltage -HVH is output as the output voltage as shown in step 6 of FIG.

  Thereafter, the control signal DVNH is set to the L level, and the transistor Q2 is turned off. At the same time, the control signal DVNL is set to the H level, and the transistor Q4 is turned on (step 7). At this timing, as shown in step 7 of FIG. 5B, the negative intermediate drive voltage −HVL is output as the output voltage.

  Thereafter, the control signal DVNL is set to L level, the transistor Q4 is turned off, and simultaneously, the control signal CPP is set to L level, and the transistor Q5 is turned on (step 8). At this timing, the ground potential is output as the output voltage as shown in step 8 of FIG.

  By the above operation, a one-wavelength pseudo sine wave is formed. Thereafter, the operations of Steps 1 to 8 are repeated to form a burst waveform having a predetermined number of pseudo sine waves.

  FIG. 6 is an explanatory diagram schematically showing a state of the circuit in which the transistor Q1 is turned off and the transistor Q3 is turned on in Step 3. In this figure, the transistors Q1 to Q4 are shown as simplified on / off switches, and the transistors Q5 and Q6 forming the ground circuit are not shown. 7A is an explanatory diagram showing an enlarged voltage waveform output to the output line 1 in steps 2 to 4, and FIG. 7B is a current magnitude of the resistor R7 in steps 2 to 4. It is explanatory drawing which shows this. Incidentally, in FIGS. 7A and 7B, the horizontal axis is the same time axis.

  In step 2, the highest drive voltage + HVH is output to the output line 1. In this state, the piezoelectric element 11 that is a capacitive load is charged with a charge corresponding to the applied voltage of + HVH. Incidentally, in Step 2, a current flowing from the output line 1 to the power source of the intermediate drive voltage + HVL flows through the resistor R7.

  Thereafter, as shown in FIG. 6, the transistor Q3 is turned on simultaneously with the turning off of the transistor Q1. At this time, the electric charge charged in the piezoelectric element 11 maintains the + HVH voltage in the output line 1 and the diode D30 is turned off. On the other hand, the diode D7, which is a power saving unit, is turned on by applying a forward voltage. In this state, the electric charge having a potential of + HVH charged in the piezoelectric element 11 passes through the diode D7 and the resistor R7 and is discharged to the power source of the intermediate driving voltage + HVL. At this time, the potential of the output line 1 exhibits a transient response having a predetermined time constant, and a transient current flows through the output line 1. The time during which this transient current occurs is shown in FIGS. 7A and 7B as the transient time T1 when shifting from step 2 to step 3. The resistance R7 is set to a value of about 50 to 150Ω.

  Thereafter, the voltage of the output line 1 decreases from + HVH due to the discharge of the charge accumulated in the piezoelectric element 11, and becomes a voltage of + HVL. At this time, the diode D7 is turned off, while the diode D30 is turned on. While the transistor Q3 is in the ON state, the output line 1 is maintained at the intermediate drive voltage + HVL. In the output voltage waveform of FIG. 7A, a voltage of + HVL is output to the output line 1 until the transition to step 4 after the transition time T1 has elapsed in step 3.

  Also, when the process proceeds from step 6 to step 7, the same thing occurs, although the voltage polarity is different, and the voltage of the output line 1 shifts from the negative maximum drive voltage -HVH to the negative intermediate drive voltage -HVL. When this occurs, the diode D8 is turned on, flows through the resistor R8 and the diode D8, generates a forward current toward the piezoelectric element 11, and the charge charged in the piezoelectric element 11 is discharged during the transient time.

  The power consumed by the multilevel pulsar 33 is smaller than that of the multilevel pulsar 43 having the configuration described below, for example. FIG. 8 is an explanatory diagram similar to FIG. 6, showing a simplified configuration of the multilevel pulsar 43. The transistors Q1 to Q4, the diodes D30 and D40, the power supply voltages ± HVH and ± HVL, the transistors Q5 and Q6 which are ground circuits (not shown), and the output line 1 of the multilevel pulsar 43 are the same as the multilevel pulsar 33. The diodes D7 and D8 and the resistors R7 and R8, which are power saving means of the multilevel pulsar 33, are replaced with a resistor R44 that connects the output line 1 and the ground terminal in the multilevel pulsar 43, and the configuration is simplified. Here, the resistance R44 has a magnitude of about 100 to 300Ω, and has a larger value than the resistances R7 and R8.

  Here, in step 2, the highest drive voltage + HVH is output to the output line 1 as in FIG. In this state, the piezoelectric element 11 that is a capacitive load is charged with a charge corresponding to the applied voltage of + HVH.

  Thereafter, as shown in FIG. 8, the transistor Q3 is turned on simultaneously with the transistor Q1 being turned off. At this time, the electric charge charged in the piezoelectric element 11 maintains the + HVH voltage in the output line 1 and the diode D30 is turned off. In this state, the electric charge charged in the piezoelectric element 11 passes through the resistor R44, a current flows to the ground terminal, and a transient current having a predetermined time constant is generated.

  FIG. 9 is an explanatory diagram showing the operation when the multi-level pulsar 43 is used. In FIG. 9A, the horizontal axis is a time axis that changes from step 2 to step 4, and the vertical axis is a voltage axis that shows a change in the output voltage of the multilevel pulsar 43. FIG. 9B has a time axis similar to that in FIG. 9A, and shows the change in the current flowing through the resistor R44 on the vertical axis. The time during which the transient current flowing through the resistor R44 occurs is illustrated as the transient time T2 when the process proceeds from step 2 to step 3 in the voltage waveform of FIG. 9A. The resistor R44 is set to a value of about 100 to 300Ω.

  Thereafter, the voltage of the output line 1 decreases from + HVH due to the discharge of the charge accumulated in the piezoelectric element 11, and becomes a voltage of + HVL. Here, the diode D30 is turned on, and the output line 1 is maintained at the intermediate drive voltage + HVL while the transistor Q3 is in the on state. In the voltage waveform of FIG. 9A, a voltage of + HVL is output to the output line 1 until the transition to Step 4 after the transition time T2 has elapsed in Step 3. During this time, a current + HVL / R44 flows through the resistor R44.

  Here, the power consumption of the multi-level pulsar 43 is a large value compared to the power consumption of the multi-level pulsar 33 including the diodes D7 and D8 and the resistors R7 and R8 that constitute the power saving means. That is, in the multi-level pulser 43, a current that constantly flows through the resistor R44 is generated during a period in which the output voltage in steps 1 to 8 is not 0V. This current increases the power consumption of the multi-level pulsar 43 using the resistor R44. On the other hand, in the multi-level pulsar 33 according to the first embodiment, power consumption does not occur except for the steady current in steps 2 and 6 and the discharge of the electric charge charged in the piezoelectric element 11 generated in steps 3 and 7.

  As described above, in the first embodiment, the multi-level pulsar 33 has the diodes D7 and D8 and the resistors R7 and R8 connected to the intermediate drive voltage ± HVL, which constitutes a power saving means. It is possible to eliminate the current consumed by the current. Thereby, power consumption can be suppressed low, and the heat generation of the multilevel pulsar 33 can be reduced.

  In the first embodiment, the multilevel pulsar 33 is not provided with a resistor for connecting the output line 1 and the ground terminal. However, a separate resistor may be provided. In this case, the resistance value is set to 500Ω or more, which is larger than the resistance R44 of the multilevel pulsar 43. As a result, it is possible to configure a multilevel pulser in which an increase in power consumption is reduced as compared with the multilevel pulser 43 having a simple configuration.

(Embodiment 2)
By the way, in the first embodiment, the diodes D7 and D8 and the resistors R7 and R8 of the power saving means are connected to the intermediate drive voltage ± HVL. However, when the rectangular wave is used as the drive voltage waveform of the piezoelectric element 11 In some cases, the power saving means increases the power consumption. Therefore, in the second embodiment, in order to prevent an increase in power consumption when the drive voltage waveform of the piezoelectric element 11 uses a rectangular wave, the multi-level pulser 33 is connected to the intermediate drive voltage ± HVL by the power saving means. The power saving means may include connection switching means for switching between the intermediate drive voltage ± HVL and the non-connected state. This connection switching means switches the connection destination of the power saving means between ± HVH and ± HVL, or connects the power saving means to ± HVH and connects to both ± HVH and ± HVL. Switch between not connected and not connected.

  The connection switching means will be specifically described. FIG. 10 is a block diagram showing the configuration of the multilevel pulsar 53 according to the second embodiment. The multilevel pulsar 53 corresponds to the multilevel pulsar 33 shown in FIG. 6 and is the same as the multilevel pulsar 33 except for the switches 57 and 58 which are connection switching means. The description of the part is omitted.

  The switch 57 selects the output of the pulsar power supply unit 31 connected to the resistor R7 as either the maximum drive voltage + HVH or the intermediate drive voltage + HVL, or the resistor R7 is connected to the maximum drive voltage + HVH. , A connection switching means for selecting one of the states in which the resistor R7 is not connected to any power supply voltage. The switch 57 is configured using a relay or the like. When a rectangular wave is used as the driving voltage waveform of the piezoelectric element 11 according to an instruction from the control unit 108, the switch 57 is connected to the maximum driving voltage + HVH or the maximum driving voltage + When the pseudo sine wave is used as the drive voltage waveform of the piezoelectric element 11 without being connected to either the HVH or the intermediate drive voltage −HVL, it is connected to the intermediate drive voltage + HVL. In the same manner as the switch 57, the switch 58 selects either the maximum drive voltage -HVH or the intermediate drive voltage -HVL as the power source connected to the resistor R8, or the resistor R8 is connected to the maximum drive voltage -HVH. Connection switching means for selecting one of the connected state and the state in which the resistor R8 is not connected to any power supply voltage.

  When the switches 57 and 58 are connected to the intermediate drive voltage ± HVL and the pseudo sine wave is used as the waveform of the piezoelectric element 11, the multilevel pulsar 53 performs the same operation as in the first embodiment. In the multi-level pulser 53, when the switches 57 and 58 are connected to the maximum drive voltage ± HVH and a rectangular wave is used as the waveform of the piezoelectric element 11, the diodes D7 and D8 always have a reverse bias voltage. Applied and turned off. Similarly, when the multilevel pulsar 53 uses a rectangular wave as the waveform of the piezoelectric element 11, the switches 57 and 58 may not be connected to any power supply voltage. Therefore, when a rectangular wave is used as the waveform of the piezoelectric element 11, the power saving means does not cause current to flow through the resistors R7 and R8, and does not cause power consumption.

  When a rectangular wave is used as the drive voltage waveform of the piezoelectric element 11, only the push-pull circuit including the transistors Q1 and Q2 operates (the transistors Q3 and Q4 are in the off state). In this case, a voltage of ± HVH is output to the output line 1. Here, if the diodes D7 and D8 and the resistors R7 and R8, which are power saving means, are connected to the intermediate drive voltage ± HVL, the diodes D7 and D8 are alternately turned on to consume power. Occurs.

  As described above, in the second embodiment, when the rectangular wave is generated by the switches 57 and 58 as the connection switching means, the power saving means is not operated and the pseudo sine wave is generated. In this case, the power saving means can be put into an operating state to reduce power consumption.

(Embodiment 3)
By the way, in Embodiment 1 described above, the diode D7 of the power saving means causes a current to flow during the transient time T1 in step 3, and power is consumed by the resistor R7. Thus, power consumption can be reduced. Therefore, in the third embodiment, the case where the power supply voltage connected to the power saving unit is reduced by the voltage dividing unit to shorten the transient time, thereby reducing the power consumption will be shown.

  FIG. 11 is a block diagram showing the configuration of the multilevel pulsar 63 according to the third embodiment. The multi-level pulsar 63 corresponds to the multi-level pulsar 33 shown in FIG. 6, and is exactly the same as the multi-level pulsar 33 except for the level shift circuits 60 and 61 that are voltage dividing means. Description of parts other than the level shift circuits 60 and 61 is omitted.

  The level shift circuit 60 is connected between the resistor R7 and the intermediate drive voltage + HVL which is the output of the pulsar power supply unit 31, and is a voltage dividing means for making the voltage supplied to the resistor R7 lower than the intermediate drive voltage + HVL. . Level shift circuit 60 includes a transistor Q5 and resistors R10 and R11. Resistors R10 and R11 divide intermediate drive voltage + HVL. For example, R10 is 20 kΩ and R11 is 80 kΩ, and outputs 80% of the intermediate drive voltage + HVL.

  The transistor Q5 is a driver that supplies the voltage divided by the resistors R10 and R11 to the resistor R7 and the diode D7, which are power-saving means. For example, a PNP-type bipolar transistor is used. .

  The level shift circuit 61 is connected between the resistor R8 and the intermediate drive voltage -HVL that is the output of the pulsar power supply unit 31, and voltage dividing means for making the voltage supplied to the resistor R8 higher than the intermediate drive voltage -HVL. It is. Level shift circuit 61 includes transistor Q6 and resistors R10 and R11, and performs exactly the same operation as level shift circuit 60.

  FIG. 12 is an explanatory diagram showing the operation of the level shift circuit 60 which is a voltage dividing means. FIG. 12 shows the output voltage and transient response of the output line 1 during the transition from step 2 to step 3 in which the transistor Q1 is turned off and the transistor Q3 is turned on, similarly to the operation of the multilevel pulser 33 shown in FIG. Is shown.

  The transient response 90 is a transient response indicated by the multilevel pulsar 63 having the level shift circuit 60 which is a voltage dividing means. The transient response 90 has a time constant determined by the capacitance C of the piezoelectric element 11 and the resistor R7, and is exponential from the output voltage + HVH to the voltage of 0.8 × HVL that is the output of the level shift circuit 60. To decrease. The transient response 91 is a transient response exhibited by the multilevel pulser 33 that does not have the level shift circuit 60. The transient response 91 is a time constant determined by the capacitance of the piezoelectric element 11 and the resistor R7, and decreases transiently from the output voltage + HVH to the voltage + HVL.

  Transient responses 90 and 91 have the same transient time T1. Therefore, the transient response 90 having a large voltage change reaches the voltage + HVL earlier than the transient response 91, and the switching speed is increased. On the other hand, since the transient response 91 has a smaller gradient as the output voltage approaches + HVL, the transient time T1 for reaching the voltage + HVL becomes longer.

  Further, in the transient response 90, since the current flows through the resistor R7 only when the output voltage is between + HVH and + HVL, the current consumption can be reduced as the time interval is shortened. Note that the level shift circuit 61 increases the speed of the transient response in the same manner as the transition from step 6 to step 7.

  As described above, in the third embodiment, the power supply voltage connected to the diodes D7 and D8 and the resistors R7 and R8 as power saving means is divided by the level shift circuits 60 and 61 as voltage dividing means. Since it is small, the transient response from step 2 to step 3 can be performed at high speed, and power consumption can be reduced by this increase in speed.

  Although the present invention has been described above by the embodiment, the present invention is not limited to this, and the circuit diagram showing the configuration of the multilevel pulsar 33 shown in FIG. 4 is the gist of the present invention. It can be changed as appropriate without changing the range.

It is a block diagram which shows the whole structure of an ultrasonic imaging device. FIG. 3 is a block diagram illustrating a configuration of an image acquisition unit according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration of a transmission unit according to the first exemplary embodiment. 1 is a circuit diagram showing a configuration of a multilevel pulser according to a first exemplary embodiment; FIG. 6 is an explanatory diagram showing an overall output operation of the multilevel pulser according to the first exemplary embodiment. FIG. 6 is an explanatory diagram showing a circuit operation of the multilevel pulser according to the first exemplary embodiment. FIG. 6 is an explanatory diagram showing changes in output voltage and current of the multilevel pulser according to the first exemplary embodiment. It is explanatory drawing which shows the structure and operation | movement of a multilevel pulser of a simple structure. It is explanatory drawing which shows the operation | movement and the change of an electric current when the output voltage of the multilevel pulser of a simple structure is switched. FIG. 5 is a circuit diagram showing a configuration of a multi-level pulser according to a second exemplary embodiment. It is a circuit diagram which shows the structure of the multilevel pulsar concerning Embodiment 3. FIG. It is explanatory drawing which shows the transient response of the multilevel pulsar concerning Embodiment 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Output line 2 Test object 10 Ultrasonic probe 11 Piezoelectric element 21 Transmission beam former 22 Transmission part 23 Reception part 24 Reception beam former 25 B mode processing part 26 Doppler processing part 31 Pulsar power supply part 32 Pulsar control parts 33, 43, 53, 63 Multi-level pulser 57, 58 Switch 60, 61 Level shift circuit 90, 91 Transient response 100 Ultrasonic imaging device 102 Image acquisition unit 104 Image memory unit 105 Image display control unit 106 Display unit 107 Input unit 108 Control units C1 to C3 Capacitors
D1-4, D7, D8, D30, D40 Diode
Q1-Q6 transistors
R1-R4, R7, R8, R10, R11, R44 resistors

Claims (9)

An ultrasonic imaging apparatus that transmits ultrasonic waves by supplying a predetermined voltage to a piezoelectric element,
A pulsar having an output line connected to the piezoelectric element and a plurality of push-pull circuits connected to the output line and supplying a plurality of power supply voltages having different sizes to the plurality of push-pull circuits. Power supply
Among the plurality of push-pull circuits, at least one of the push-pull circuits includes a first rectifying element that prevents a reverse current from flowing through a complementary transistor that constitutes the push-pull circuit,
Furthermore, the pulsar has power saving means including a second rectifying element and a resistor, and the second rectifying element and the resistor constituting the power saving means have the first rectifying element. An ultrasonic imaging apparatus, wherein the output line is connected to a power supply voltage supplied to a push-pull circuit.   The ultrasonic imaging apparatus according to claim 1, wherein the power supply unit generates positive and negative power supply voltages that are output to the push-pull circuit and are equal in magnitude.   The ultrasonic imaging apparatus according to claim 2, wherein the pulser includes a ground circuit that turns on / off a connection between the output line and a ground terminal.   The power saving means connects the output line to at least one of power supply voltages not having the maximum value among a plurality of power supply voltages output from the power supply unit. The ultrasonic imaging apparatus of any one of Claims.   5. The ultrasonic imaging apparatus according to claim 1, wherein the power saving unit includes a voltage dividing unit that divides the power supply voltage and connects the divided power supply voltage to the output line. 6.   The ultrasonic imaging apparatus includes a pulsar control unit that operates the plurality of push-pull circuits so that a pseudo sine wave that approximates a rectangular wave or a sine wave is output to an output line by the plurality of push-pull circuits. The ultrasonic imaging apparatus according to claim 1, wherein:   7. The pulsar comprises connection switching means for switching between connection and disconnection of the power saving means and a power supply voltage supplied to a push-pull circuit having the first rectifying element. The ultrasonic imaging apparatus according to any one of the above.   When the electrical signal is a rectangular wave, the connection switching means connects the power saving means to a power supply voltage having a maximum size among the plurality of power supply voltages, or any of the plurality of power supply voltages. The ultrasonic imaging apparatus according to claim 7, wherein the ultrasonic imaging apparatus is not connected.   The connection switching means connects the output line to at least one of the plurality of power supply voltages that is not the largest among the plurality of power supply voltages when the electrical signal is a pseudo sine wave. Item 8. The ultrasonic imaging apparatus according to Item 7.

Images