JP2009297128A - Ultrasonic diagnostic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic diagnostic apparatus equipped with a transmission circuit for reducing static power consumption without causing a drooping phenomenon. <P>SOLUTION: A transmission signal corresponding to diagnostic application is amplified by a first amplifier 10 and the output of the first amplifier is amplified by a second amplifier 11 to drive an oscillator of an ultrasonic probe. The second amplifier 11 is a mutually complementary source grounded amplifier composed of two sets of metal oxide semiconductor field effect transmitters (MOSFETs) including a P-channel MOSFET 12 and an N-channel MOSFET 13 operated with direct-current power supplies ±HV of positive or negative polarity for the central level of the output voltage. A parallel connector with idling current suppressing resistances 15 and 18 and capacitors 14 and 17 which high-frequencially ground sources S of the two sets of MOSFETs is connected with zener diodes 16 and 19 inversely parallel between the amplifier and the direct-current power supplies ±HV to compose a voltage limiter circuit. The voltage of the capacitors 14 and 17 is limited to a prescribed value or lower by the voltage limiter circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic diagnostic apparatus mainly used for medical purposes, and more particularly to a technique for preventing drooping of a transmission circuit for driving an ultrasonic transducer and reducing power consumption.

  A medical ultrasonic diagnostic apparatus irradiates a subject with ultrasonic waves from an ultrasonic probe and reconstructs a tomographic image of the subject based on an echo signal received through the ultrasonic probe The reconstructed tomographic image is displayed on a display device for diagnosis.

  In such an ultrasonic diagnostic apparatus, a high voltage pulse is used to drive the probe, and an arbitrary transmission signal can be amplified in a transmission circuit that generates the high voltage pulse. As described above, Patent Document 1 discloses a complementary source grounded amplifier in which a P channel and an N channel high breakdown voltage field effect transistor (MOSFET) are combined.

Japanese Unexamined Patent Publication No. 2006-122449

In recent years, in the ultrasonic diagnostic apparatus, in addition to the popularization of the portable type, the number of channels has been increasing in order to improve the image quality, and thus low power consumption has become an important issue.
For this reason, as shown in FIG. 3 of Patent Document 1, using a switching circuit that turns on / off the gate bias voltage V1 of the MOSFET, the gate bias voltage in a state where there is no input of the first stage amplifier circuit, so-called idling state Methods such as turning off V1 and increasing the resistances 17 and 18 to suppress idling current are used.

However, the means for turning on / off the gate bias voltage V1 is difficult to operate at high speed due to the time constants of the resistor 21 and the decoupling capacitors 19 and 20.
Therefore, there is a limit to increasing the repetition frequency of the pulse wave.

In addition, the transmission circuit of Patent Document 1 is not devised to provide a high gain by grounding the source terminal of the MOSFET at a high frequency when an AC signal is input.
For this purpose, it is conceivable to connect a high-frequency grounding capacitor in parallel with the resistors 17 and 18 for suppressing the DC idling current.

  However, if the high-frequency grounding capacitor is provided and the resistors 17 and 18 are made high in order to reduce the idling current, the time constant of the resistors 17 and 18 and the high-frequency grounding capacitor becomes large, and the circuit operates at a high repetition frequency. When this is performed or when operated with a continuous wave, a droop phenomenon in which the output amplitude is attenuated significantly occurs.

  As a result, since the source potential of the MOSFET rises excessively, the MOSFET is difficult to turn on and a desired output cannot be obtained.

  In order to solve this problem, the resistance values of the resistors 17 and 18 must be reduced, so that the idling current increases, resulting in an increase in power consumption.

  Accordingly, an object of the present invention is to provide an ultrasonic diagnostic apparatus including a transmission circuit that reduces static power consumption without causing a droop phenomenon.

  The above object is achieved by the following means. That is, an ultrasonic diagnostic apparatus including a transmission circuit that generates a pulse wave or a continuous wave for driving a transducer of an ultrasonic probe by amplifying a transmission signal corresponding to a diagnostic application set by an operation unit The transmission circuit includes a first amplifier that amplifies the transmission signal, and a positive polarity and a negative polarity with respect to a center level of an output signal for amplifying the output of the first amplifier. A second amplifier that operates with a direct current power source, and the second amplifier includes a complementary source grounded amplifier composed of two sets of P-channel and N-channel MOSFETs, and each of the two sets of MOSFETs. A parallel connection body of a resistor and a capacitor connected between a source and the DC power supply of positive polarity and negative polarity, and the resistance is reduced only when the voltage of the capacitor of the parallel connection body rises above a predetermined value. It is provided with a resistance variable means that becomes a resistance.

  The resistance variable means is voltage limiter means for limiting the voltage of the capacitor of the parallel connection body to a predetermined value or less, and is specifically as follows.

  (1) A Zener diode, which is a constant voltage diode, is connected in parallel with the capacitor to have a reverse bias polarity, and the voltage of the capacitor is limited to be equal to or less than the Zener voltage of the Zener diode.

  (2) Discharging means connected in parallel with the capacitor for discharging the voltage of the capacitor below a predetermined value, the discharging means short-circuit the capacitor when the voltage of the capacitor reaches a predetermined value It is a switch to do. This switch is preferably a transistor because the circuit is simple.

  Furthermore, in order to prevent the output DC voltage level from deviating significantly from 0V, the impedance between the output terminal of the second amplifier and the ground is low impedance for the DC signal and high impedance for the AC signal. Connect the impedance.

  Furthermore, in order to reduce the harmonic component of the output voltage, AC negative feedback means for AC negative feedback of the output voltage of the second amplifier to the first amplifier is provided.

  By providing resistance variable means for preventing a rise in source potential of the MOSFET and reducing idling current in a complementary source grounded amplifier composed of two sets of MOSFETs of P channel and N channel, ultrasonic waves The transmission voltage applied to the transducer of the probe can be kept constant without being attenuated over time. As a result, it is possible to achieve both reduction of idling current and prevention of droop phenomenon, and an ultrasonic diagnostic apparatus capable of reducing power consumption even when the number of channels is increased for high image quality can be provided.

  Hereinafter, preferred embodiments of an ultrasonic diagnostic apparatus of the present invention will be described in detail with reference to the accompanying drawings.

  Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment of the present invention, and the repetitive description thereof will be omitted.

  FIG. 1 is an overall configuration diagram of an ultrasonic diagnostic apparatus according to the present invention. The ultrasonic diagnostic apparatus 1 includes a control panel 2 for setting an operation signal corresponding to a diagnostic application, a control unit 3 for controlling the entire apparatus according to the operation signal, and a transmission signal output from the control unit 3. A transmission circuit 4 for amplifying the signal, a probe 5 for applying an output voltage of the transmission circuit 4 to generate an ultrasonic wave and irradiating the subject, and detecting an echo signal from the subject, A receiving circuit 6 that receives an echo signal detected by the probe 5, an ultrasonic image forming unit 7 that processes an echo signal received by the receiving circuit 6 to form an ultrasonic image, and this image configuration And a display unit 8 for displaying an ultrasound image, a diagnosis result, and the like configured by the unit 7.

  An embodiment of the transmission circuit according to the feature of the present invention of the ultrasonic diagnostic apparatus configured as described above will be described in detail.

First Embodiment
FIG. 2 is a first embodiment of the transmission circuit 4 used in the ultrasonic diagnostic apparatus of the present invention. As shown in FIG. 2, the transmission circuit 4 includes a first amplifier 10 composed of an operational amplifier that amplifies the transmission signal (a) from the control unit 3, a positive polarity DC power source + HV, and a negative polarity. And a complementary source grounded amplifier 11 that is a second amplifier that combines a P-channel and an N-channel MOSFET that operate with a direct current power source -HV of the same polarity.

The second amplifier 11 connects the drains D of the P-channel PMOSFET 12 and the N-channel NMOSFET 13 in series, and a capacitor 14 is connected between the positive polarity DC power source + HV and the source S of the PMOSFET 12. A parallel connection body of resistors 15 is connected, and a Zener diode 16 which is a constant voltage diode is connected in reverse parallel to the parallel connection body. Similarly, a parallel connection body of a capacitor 17 and a resistor 18 is connected between the negative polarity DC power supply -HV and the source S of the NMOSFET 13, and a Zener diode 19 is connected in reverse parallel to this parallel connection body.
The anti-parallel means that the cathode of the Zener diode 16 is connected to the DC power source + HV, the anode is connected to the source S of the PMOSFET 12, the cathode of the Zener diode 19 is connected to the source S of the PMOSFET 12, and the anode is connected to the DC power source -HV. Means to be connected.

  Then, one end of decoupling capacitors 20 and 21 for cutting a DC voltage component is connected to the output terminal of the first amplifier 10, and the other ends of these decoupling capacitors are connected to the gates G of the PMOSFET 12 and the NMOSFET 13, respectively. Connect to.

  Bias voltages Vb1 and Vb2 of the PMOSFET 12 and NMOSFET 13 are for applying a bias voltage to the respective gates G of the PMOSFET 12 and NMOSFET 13, and are applied to the gate G via resistors 22 and 23.

  The resistors 15 and 18 are for suppressing an idling current that is a current that flows through the PMOSFET 12 and the NMOSFET 13 due to the bias voltages Vb1 and Vb2 when there is no input to the first amplifier, that is, in a so-called idling state. . Since the direct current idling current always flows even when there is no input to the first amplifier as described above, it becomes a static current consumption. Therefore, the resistors 15 and 18 are used from the viewpoint of low power consumption. Need to have high resistance.

  The capacitors 14 and 17 are provided for grounding the source S of the PMOSFET 12 and the NMOSFET 13 at a high frequency when an AC signal is input to the gate G of the PMOSFET 12 and the NMOSFET 13 to make the second amplifier 11 a high gain amplifier. It is.

  In general, the threshold voltage which is the minimum conduction voltage of the PMOSFET 12 and the NMOSFET 13 is different, and this causes a difference in the idling current of both MOSFETs. Therefore, the difference current is passed through the resistor 24, and the output DC voltage level is changed from 0V. I try not to make a big difference.

  The zener diodes 16 and 19 are for preventing a droop phenomenon in which the output voltage (the voltage across the resistor 24) output from the output terminal attenuates with time. Here, the droop phenomenon seen when operating at a high repetition frequency without providing the Zener diodes 16 and 19 will be described with reference to FIGS.

  On the NMOSFET 13 side in FIG. 2, the idling current flows between the source S and the drain D of the NMOSFET 13 in a manner superimposed on the output current of the first amplifier 10 because the output voltage (b ) Is in the positive half cycle.

During this half cycle period, a current flowing between the source S and the drain D of the NMOSFET 13 flows in the capacitor 17 for grounding the source S of the NMOSFET 13 at a high frequency, so that charges are accumulated. As a result, the voltage across the capacitor 17 rises and the potential of the source S rises.
The charge accumulated in the capacitor 17 in this way is connected to the source S of the NMOSFET 13 when the input signal to the first amplifier 10 is in the negative half cycle or when the input to the first amplifier is not input. It is discharged through the resistor 18.

  As described above, the resistor 18 connected to the source S of the NMOSFET 13 has a function of suppressing the idling current and a function of discharging the charge accumulated in the capacitor 17.

  However, if the resistor 18 is made high to reduce power consumption, the time constant of the discharge becomes long, so that when the repetition frequency is high or when a continuous wave is transmitted, it is accumulated in the capacitor 17. The charge is not fully removed.

  Therefore, the voltage across the capacitor 17 continues to rise every time such a current flows between the source S and drain D of the NMOSFET 13. As a result, since the potential of the source S rises excessively, the NMOSFET 13 becomes difficult to conduct, and a droop phenomenon occurs in which the amplitude of the output voltage decays with time as shown in FIG. . A similar droop phenomenon also occurs on the PMOSFET 12 side.

  Such a droop phenomenon in which the output voltage attenuates can be prevented by setting the voltages of the capacitors 14 and 17 for grounding the sources of the PMOSFET 12 and the NMOSFET 13 at a high frequency to a predetermined value or less.

  That is, the resistors 15 and 18 for reducing the idling current may be set to a low resistance only when the voltage of the capacitors 14 and 17 rises above a certain voltage (resistance variable means). The Zener diodes 16 and 19 are provided to prevent the droop phenomenon by setting the voltage of the capacitors 14 and 17 to a predetermined value or less (voltage limiter means) and prevent the droop phenomenon by operating as follows. Is done.

  In FIG. 2, the Zener voltages of the Zener diodes 16 and 19 are voltages applied across the capacitors 14 and 17 connected to the sources S of the PMOSFET 12 and the NMOSFET 13 in the absence of an input signal to the first amplifier 10. That is, it is set to a value slightly higher than the voltage obtained by subtracting the threshold voltages of the PMOSFET 12 and the NMOSFET 13 from the bias voltages Vb1 and Vb2.

  Thus, by setting the Zener voltage of the Zener diodes 16 and 19, the Zener diodes 16 and 19 are in a high resistance state when the input signal to the first amplifier 10 is not input.

  Next, it will be described that the droop phenomenon can be prevented by setting the Zener voltage as described above.

  As described above, on the NMOSFET 13 side in FIG. 2, the idling current flows between the source S and the drain D of the NMOSFET 13 so as to be superimposed on the output current of the first amplifier 10. The output voltage (b) is in the positive half cycle. Charge is accumulated in the capacitor 17 during this half-cycle period.

  The charge accumulated in this way continues to accumulate almost without being discharged when the resistor 18 connected to the source S is high resistance, but the voltage across the capacitor 17 becomes equal to or higher than the zener voltage. In this case, since the operating resistance of the Zener diode 19 is low, the charge accumulated in the capacitor 17 is discharged through this. Therefore, the voltage across the capacitor 17 does not rise above the Zener voltage. Then, after the electric charge accumulated in the capacitor 17 is discharged and the voltage across the capacitor 17 becomes equal to or lower than the Zener voltage, the Zener diode 19 becomes a high resistance state again, and the idling current is suppressed.

  Like the NMOSFET 13 side, the Zener diode 16 on the PMOSFET 12 side operates, and the voltage across the capacitor 14 does not rise above the Zener voltage, and after the voltage across the capacitor 14 falls below the Zener voltage, The Zener diode 19 is again in a high resistance state, and the idling current is suppressed.

  As described above, according to the transmission circuit according to the first embodiment, by selecting the Zener diodes 16 and 19 having an appropriate Zener voltage, it is possible to prevent the potentials of the sources S of the PMOSFET 12 and the NMOSFET 13 from rising. Without causing the droop phenomenon, the resistances 15 and 18 for suppressing the idling current can be increased to reduce the idling current, which is a static current consumption.

  Next, the operation of the ultrasonic diagnostic apparatus of the present invention using the transmission circuit 4 of FIG. 2 will be described.

  (1) When the sine wave input signal shown in (a) of FIG. 2 is input from the control unit 3 to the first amplifier 10 by the operation signal set in the control panel 2 of FIG. 1, the first amplifier 10 10 outputs the alternating voltage (b) obtained by amplifying the input signal.

  (2) When the alternating voltage of (b) is applied to the gates G of the PMOSFET 12 and the NMOSFET 13, the PMOSFET 12 and the NMOSFET 13 are turned on and off.

  (3) That is, during the period of the positive half cycle of the alternating voltage of (b) above, the PMOSFET 12 becomes non-conductive and the NMOSFET 13 becomes conductive and current flows. During this non-conducting period of the PMOSFET 12, the Zener diode 16 operates so as to discharge the voltage of the capacitor 14 so that the voltage of the capacitor 14 for grounding the source S of the PMOSFET 12 at a high frequency is below a predetermined value.

  (4) During the period of the negative half cycle of the alternating voltage of (b) above, the PMOSFET 12 is conductive and current flows, and the NMOSFET 13 is nonconductive and no current flows. During this non-conducting period of the NMOSFET 13, the Zener diode 19 operates so as to discharge the voltage of the capacitor 17 so that the voltage of the capacitor 17 for grounding the source S of the NMOSFET 13 at a high frequency becomes below a predetermined value.

  (5) The second amplifier 11 operates as in (3) and (4) above, and the drain currents of the PMOSFET 12 and NMOSFET 13 are as shown in (c) and (d), respectively. The voltage to be applied is a voltage proportional to the input voltage as shown in (e).

  (6) The output voltage of the transmission circuit 4 is applied to a transducer (not shown) of the probe 5 to generate an ultrasonic wave from the probe 5 to irradiate the subject, and from the subject The echo signal is detected, and the detection circuit 6 receives this detection signal.

  (7) The echo signal received by the receiving circuit 6 is processed by the ultrasonic image construction unit 7 to form an ultrasonic image, and the constructed ultrasonic image and information related to the image are displayed on the display unit 8. Displayed on the screen for diagnosis.

  (8) In the idling state where the voltage of the capacitors 14 and 17 is equal to or lower than the Zener voltage and there is no input to the first amplifier 10, the resistors 15 and 18 become high resistance and the idling current is small. Become.

  In the transmission circuit according to the first embodiment, it is possible to prevent the potential of the source S of the PMOSFET 12 and the NMOSFET 13 from rising by selecting the Zener diodes 16 and 19 having an appropriate Zener voltage, thereby causing a droop phenomenon. In addition, the resistances 15 and 18 for suppressing the idling current can be increased to reduce the idling current, which is a static current consumption.

  As described above, the ultrasonic diagnostic apparatus using the transmission circuit according to the first embodiment does not attenuate the transmission voltage applied to the transducer of the ultrasonic probe even if time passes. Therefore, it is possible to achieve both reduction of idling current and prevention of droop phenomenon. This makes it possible to reduce power consumption even if the number of channels is increased for higher image quality.

<< Second Embodiment >>
FIG. 4 is a second embodiment of the transmission circuit 4 used in the ultrasonic diagnostic apparatus of the present invention. The transmission circuit 4 is different from the voltage limiter circuit for limiting the voltages of the capacitors 14 and 17 for grounding the sources S of the PMOSFET 12 and the NMOSFET 13 of the second embodiment shown in FIG. Since the rest is the same, only the configuration of the limiter circuit and the operation of the transmission circuit using the limiter circuit will be described here.

  In FIG. 4, a parallel connection of resistors 31 and 32 and a capacitor 14 connected in series is connected between a positive polarity DC power source + HV and the source S of the PMOSFET 12, and in parallel with this parallel connection, As shown in the figure, a PNP transistor 33 which is a switching element is connected. The resistor 31 is connected between the emitter E and the base B of the transistor 33, and the other resistor 32 is connected between the base B and the collector C of the transistor 33. Similarly, a parallel connection body of resistors 34 and 35 and a capacitor 17 connected in series is connected between the negative polarity DC power supply -HV and the source S of the NMOSFET 13, and in parallel with this parallel connection body, As illustrated, an NPN transistor 36, which is a switching element, is connected. The resistor 34 is connected between the collector C and the base B of the transistor 36, and the other resistor 35 is connected between the base B and the emitter E of the transistor 36.

  In the voltage limiter circuit configured as described above, the resistor 31 and the resistor 32 connected in series correspond to the resistor 15 of the first embodiment of FIG. 2, and the resistor 34 and the resistor 35 connected in series are: This corresponds to the resistor 18 of the first embodiment of FIG.

  The ratio of the resistors 31 and 32 and the ratio of the resistors 34 and 35 are determined so that the transistors 33 and 36 are non-conductive in the absence of an input signal to the first amplifier 10, that is, the voltage between the base B and the emitter E is Set to a value that is less than or equal to the threshold voltage Vbe.

  Next, an operation for preventing the droop phenomenon by setting the resistance values of the resistors 31, 32, 34, and 35 as described above will be described.

  On the NMOSFET 13 side in FIG. 2, the idling current flows between the source S and the drain D of the NMOSFET 13 in a manner superimposed on the output current of the first amplifier 10 because the output voltage (b) of the first amplifier 10 Is in the positive half cycle. Charge is accumulated in the capacitor 17 during this half-cycle period.

  The charges accumulated in this way continue to accumulate with almost no discharge in the state where the resistors 34 and 35 connected to the source S remain high resistance, but the voltage applied to the resistor 35 When the threshold voltage Vbe of the transistor 36 is exceeded, the transistor 36 becomes conductive and has a low resistance, so that the charge accumulated in the capacitor 17 is discharged via the transistor 36 (discharge means).

  Therefore, the voltage across the capacitor 17 does not rise above a certain value determined by the threshold voltage Vbe of the transistor 36 and the ratio of the resistors 34 and 35. After the charge accumulated in the capacitor 17 is discharged and the voltage across the capacitor 17 falls below a certain value determined by the threshold voltage Vbe of the transistor 36 and the ratio of the resistors 34 and 35, the transistor 36 again becomes high. It becomes a state of resistance and the idling current is suppressed.

  Similarly to the NMOSFET 13 side, the transistor 33 on the PMOSFET 12 side operates, and the voltage across the capacitor 14 does not rise above a certain value determined by the threshold voltage Vbe of the transistor 33 and the ratio of the resistors 31 and 32. After the voltage between both ends of 14 becomes equal to or less than a certain value determined by the threshold voltage Vbe of the transistor 33 and the ratio of the resistors 31 and 32, the transistor 33 becomes a high resistance state again, and the idling current is suppressed.

  As described above, according to the transmission circuit according to the second embodiment, by operating the transistor as the discharge unit, it is possible to prevent the potential of the source S of the PMOSFET 12 and the NMOSFET 13 from rising, thereby causing the droop phenomenon. Without increasing the resistances of the resistors 31, 32, 34, and 35, it is possible to reduce the idling current, which is a static current consumption.

  In the ultrasonic diagnostic apparatus using the transmission circuit according to the second embodiment, the transmission voltage applied to the transducer of the ultrasonic probe can be made constant without being attenuated over time. Therefore, it is possible to reduce the idling current and prevent the droop phenomenon. As a result, it is possible to obtain the same effect as that of the first embodiment, which can reduce the power consumption even when the number of channels is increased to improve the image quality.

<< Third Embodiment >>
The first embodiment and the second embodiment are examples of circuits in which the first amplifier and the second amplifier are simply connected in multiple stages, but the present invention uses the output voltage of the second amplifier as the output voltage. The present invention can also be applied to a circuit that performs negative feedback to the first amplifier.

  FIG. 5 shows a transmission circuit according to a third embodiment in which the output voltage of the second amplifier in the first embodiment is subjected to AC negative feedback to the first amplifier. The transmission circuit 4 is a circuit having the same configuration as that of the first embodiment except for the first amplifier 10 ′ subjected to AC negative feedback.

  In FIG. 5, the first amplifier 10 ′ includes an operational amplifier 40, a resistor 41 connected between the input terminal of the operational amplifier 40 and the ground, an output terminal of the operational amplifier 40, and − The resistor 42 is connected between the input terminals. The resistors 41 and 42 apply a local negative feedback to the operational amplifier 40 to increase the bandwidth.

  Further, a resistor 43 is connected to the + input terminal of the operational amplifier 40, and a resistor 44 and a capacitor 45 connected in series between the output terminal of the second amplifier 11 and the + input terminal of the operational amplifier 40 are provided. Then, the resistor 44 and the capacitor 45 are used to negatively feed back the output voltage of the second amplifier 11 to the operational amplifier 40.

  Note that + LV and −LV are DC power supplies of the operational amplifier 40.

  With this configuration, the droop phenomenon is prevented by the operation of the voltage limiter circuit in the same manner as in the first embodiment, and distortion is generated in the source-grounded amplifier circuit that is the second amplifier that easily generates distortion. The first wideband / high gain amplifier 10 ′ can compensate for this. As a result, a power transmission circuit that can reduce power consumption without causing a droop phenomenon and reduce harmonic components contained in the output voltage can be provided.

<< Fourth Embodiment >>
FIG. 6 shows a transmission circuit according to the fourth embodiment in which the output voltage of the second amplifier in the second embodiment is subjected to AC negative feedback to the first amplifier.

  The transmission circuit 4 is a circuit having the same configuration as that of the second embodiment except for the first amplifier 10 ′ subjected to AC negative feedback.

  In FIG. 6, a first amplifier 10 ′ is an amplifier that has a wide band by applying local negative feedback having the same circuit configuration as that of the first amplifier in the third embodiment. As a result, the output voltage is negatively AC fed back, resulting in a low distortion amplifier as a whole.

  With this configuration, the droop phenomenon is prevented by operating the voltage limiter circuit in the same manner as in the second embodiment, and in the second amplifier that is likely to generate distortion, as in the third embodiment. A certain common-source amplifier circuit can be compensated by the first broadband / high gain amplifier 10 'so that distortion does not occur. As a result, a power transmission circuit that can reduce power consumption without causing a droop phenomenon and reduce harmonic components contained in the output voltage can be provided.

  As mentioned above, although various embodiment was described about this invention, this invention is not limited to these embodiment, In the range which does not deviate from the summary of this invention, it can change variously as follows.

  (1) The limiter circuit for preventing the droop phenomenon is not limited to the above embodiment, but limits the voltages of the capacitors 14 and 17 for grounding the sources S of the PMOSFET 12 and the NMOSFET 13 to a predetermined value or less. Any limiter circuit may be used.

  (2) Although the source grounded MOSFET is used for the second amplifier, the present invention is not limited to this, and a complementary amplifier using a transistor or another semiconductor may be used.

  (3) Furthermore, the DC power supplies + HV and -HV of the above embodiment do not have to have the same positive and negative voltages, and have a positive polarity and a negative polarity with respect to the center level of the output voltage of the second amplifier. A DC power supply may be used.

  (4) Since the droop phenomenon can be prevented by using the transmission circuit of the above embodiment, continuous waves can be transmitted with the same circuit configuration. Therefore, the present invention can be applied to both pulse wave and continuous wave transmission circuits.

1 is an overall configuration diagram of an ultrasonic diagnostic apparatus according to the present invention. 1 is a transmission circuit diagram of a first embodiment used in an ultrasonic diagnostic apparatus according to the present invention. The figure for demonstrating the droop phenomenon. FIG. 6 is a transmission circuit diagram of a second embodiment used in the ultrasonic diagnostic apparatus according to the present invention. FIG. 6 is a transmission circuit diagram of a third embodiment used in the ultrasonic diagnostic apparatus according to the present invention. FIG. 6 is a transmission circuit diagram of a fourth embodiment used in the ultrasonic diagnostic apparatus according to the present invention.

Explanation of symbols

  1 Ultrasonic diagnostic device, 2 Control panel, 3 Control unit, 4 Transmitter circuit, 5 Ultrasonic probe, 6 Receiver circuit, 7 Ultrasound image component, 8 Display unit, 10, 10 'First amplifier 11, 11 '2nd amplifier, 12 P-channel MOSFET, 13 N-channel MOSFET, 14, 17 High frequency grounding capacitor, 15, 18 Idling current suppression resistor, 16, 19 Zener diode, 20, 21 Decoupling capacitor, 31, 32, 34, 35 Idling current suppression resistor, 33 PNP transistor, 36 NPN transistor

Claims (8)

  An ultrasonic diagnostic apparatus including a transmission circuit that generates a pulse wave or a continuous wave for driving a transducer of an ultrasonic probe by amplifying a transmission signal corresponding to a diagnostic application set by an operation means. The transmission circuit includes a first amplifier that amplifies the transmission signal and a direct current having a positive polarity and a negative polarity with respect to a center level of an output signal for amplifying the output of the first amplifier. A second amplifier operating from a power source, the second amplifier comprising a complementary source grounded amplifier composed of two sets of P-channel and N-channel MOSFETs, and each source of the two sets of MOSFETs, A parallel connection body of a resistor and a capacitor connected between the positive polarity and negative polarity DC power supplies, and the resistance is low resistance only when the voltage of the capacitor of the parallel connection body rises to a predetermined value or more. Variable resistance means comprising Ultrasonic diagnostic apparatus characterized by.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the resistance variable unit includes a voltage limiter unit that limits a voltage of the capacitor of the parallel connection body to a predetermined value or less.   The ultrasonic diagnostic apparatus according to claim 2, wherein the voltage limiter unit includes a constant voltage diode connected in a reverse bias in parallel with the capacitor.   3. The ultrasonic diagnostic apparatus according to claim 2, wherein the voltage limiter means includes discharge means connected in parallel with the capacitor for discharging the voltage of the capacitor to a predetermined value or less.   The ultrasonic diagnostic apparatus according to claim 4, wherein the discharging unit is a switch that operates to short-circuit the capacitor when the voltage of the capacitor reaches a predetermined value.   The ultrasonic diagnostic apparatus according to claim 5, wherein the switch is a transistor.   Furthermore, the impedance which becomes low impedance with respect to a DC signal and becomes high impedance with respect to an AC signal is connected between the output terminal of the second amplifier and the ground. The ultrasonic diagnostic apparatus of any one of Claims.   The ultrasonic diagnostic apparatus according to claim 1, further comprising AC negative feedback means for AC negative feedback of the output voltage of the second amplifier to the first amplifier. .

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