JPH04367655A - Pulser circuit for ultrasonic vibrator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit (pulsar circuit) for generating pulses for driving an ultrasonic transducer of an ultrasonic diagnostic apparatus or the like.

0002

2. Description of the Related Art Ultrasonic diagnostic apparatuses use various ultrasonic pulses depending on the mode of use. When photographing tomographic images, pulses with a small number of waves are used to increase resolution, and when photographing blood flow using the Doppler effect, pulses that last a relatively long time are used to achieve these purposes. Furthermore, the pulse generation period is also changed depending on various purposes. On the other hand, for health reasons, there are certain limits to the energy of ultrasonic waves injected into the human body, so when changing the wave number and generation period of ultrasonic pulses, the amplitude of the pulses must also be adjusted due to this total energy restriction. It needs to change.

In order to change the amplitude of the ultrasonic pulse, the voltage of the drive pulse signal applied to the ultrasonic transducer is changed. Since it is difficult to vary the drive voltage of the circuit that generates the pulse signal (pulsar circuit) for driving the ultrasonic transducer from the viewpoint of response speed, conventionally the ultrasonic transducer has been operated in multiple modes. (more precisely, to generate drive pulses of different voltages), as shown in FIG. 3(a), a dedicated pulser circuit P corresponding to each mode is used.
UL1 to PUL3 (three in FIG. 3, but any number may be used in reality) were prepared. Each pulser circuit PUL1~
PUL3 is connected to different power supply voltages VP1 to VP3, and connected to switches SW1 to SW1 depending on the mode of use.
It was connected to the ultrasonic transducer OSC by switching with SW3. Note that P1 to P3 are pulse signal inputs.

0004

[Problems to be Solved by the Invention] Since the voltage of the pulse that drives the ultrasonic transducer is as high as several V to 200 V, and the current is also approximately several A, the pulser circuit PU as shown in FIG.
If a changeover switch is to be provided on the output side of L1 to PUL3, a relay or a high voltage semiconductor switch must be used as the changeover switch. However, the repetition time of ultrasonic pulses is extremely short, ranging from tens to hundreds of microseconds.
Relays cannot follow such speeds. Further, high voltage semiconductor switches are expensive and have a problem of high on-resistance.

[0005] In order to avoid such problems, FIG. 3(b)
As shown in , the input P of the pulser circuits PUL1 to PUL3
It is conceivable to provide normal semiconductor switches SW1 to SW3 on the 1 to P3 sides. However, in this case, each pulser circuit PUL1 to PUL3 is on the output side (ultrasonic transducer OSC side)
Since they are connected to each other, when one selector switch (for example, SW1) is turned ON and the corresponding pulsar circuit PUL1 becomes operational, the other two pulsar circuits PUL2 and PUL3 switch to the pulsar circuit PUL1. load, and the waveform of the drive pulse is distorted. The present invention was made to solve these problems, and its purpose is to generate drive pulses with high speed and correct waveforms without using expensive high-voltage semiconductor switches. The object of the present invention is to provide a pulser circuit that can perform the following functions.

[0006]

[Means for Solving the Problems] The present invention, which has been made to solve the above problems, provides a pulser circuit comprising a plurality of unit pulser circuits connected in parallel to generate pulse signals for driving an ultrasonic transducer. In the circuit, (a) each unit pulser circuit is connected in series between a high-voltage side power supply and a low-voltage side power supply, and performs mutually opposite opening and closing operations in response to the same input signal.
(b) the output to the ultrasonic transducer is taken out from the connection point of both switch transistors; and (c) the output between both switch transistors and the output point. Each of them is characterized by having a forward diode.

[0007]

[Operation] Each unit pulsar circuit is connected in parallel to one output line (connected to one ultrasonic transducer), so when a certain unit pulsar circuit operates (i.e., the unit pulsar circuit When either the high-voltage side or low-voltage side switch transistor is turned on), voltage is applied to the low-voltage side or high-voltage side switch transistor of the other unit pulser circuit through its output line, and the switch transistor turns on. The parasitic capacitance of the transistor is charged. However, once charged, the diode between each switch transistor and the output line is in the opposite direction to discharge, which prevents the charged parasitic capacitance from discharging. Therefore, once the parasitic capacitance is charged, it is not further charged from the second time onwards, and when one unit pulser circuit operates, other unit pulser circuits do not serve as a load from the second pulse onwards.

[0008]

[Embodiment] An embodiment of the present invention will be explained with reference to FIGS. 1 and 2. The pulser circuit of this embodiment outputs a driving pulse Po to one ultrasonic transducer (not shown) among a large number of ultrasonic transducers constituting a probe of an ultrasonic diagnostic device. be. This pulser circuit is composed of three unit pulser circuits connected in parallel to the ultrasonic transducer. The three unit pulser circuits are connected to power supplies having different voltages, respectively, and output drive pulses Po of different modes to the ultrasonic transducer. Note that the number of unit pulser circuits may be two or four or more.

[0009] In each unit pulser circuit, a high voltage power supply VP1
High-side switch transistors Q11-Q13 and low-side switch transistors Q21-Q23 are connected in series between ~VP3 and ground (the above-mentioned low-voltage power supply). An output line Lout to the ultrasonic transducer is connected between the high-side and low-side switch transistors, so that all unit pulser circuits are connected in parallel to the ultrasonic transducer. Each switch transistor Q
Forward direction diodes DS11 to DS23 are connected between 11 to Q23 and the output line Lout.

The high-side switch transistors Q11 to Q13 and the low-side switch transistors Q21 to Q23 of each unit pulser circuit are FETs with opposite characteristics (in the example of FIG. 1, the high-side switch transistors Q11 to Q13
is p-channel type, low-side switch transistor Q
21 to Q23 are n-channel type), and input signals P1 to P1 to the gates of both switch transistors Q11 to Q23 are used.
Enter P3. Each switch transistor Q21-Q2
Diodes DK11 to DK23 and capacitors C11 to C23 drawn next to 3 are the respective switch transistors Q2.
1 to Q23 represent parasitic diodes and parasitic capacitances. When there are no input signals P1 to P3 (at zero potential), all switch transistors Q11 to Q23 are OFF.

Assume now that a pulse-like input signal P1 as shown in FIG. 2 is applied to the first pulser circuit. The first negative pulse a turns on the high-side switch transistor Q11 and turns off the low-side switch transistor Q21, so the potential of the output line Lout (
The output PO) becomes VP1. At this time, since the voltage VP1 is applied to the low-side switch transistor Q22 of the second pulser circuit and the low-side switch transistor Q23 of the third pulser circuit through the output line Lout, the parasitic capacitances C22 and C23 of both switch transistors Q22 and Q23 increase to the voltage VP1. (4th row in Figure 2). Therefore, the rise of the first output pulse PO is slightly deformed, as shown at the beginning of the second stage in FIG.

When the input signal P1 of the first pulser circuit changes to the positive side b, the high side switch transistor Q11
is OFF, and low-side switch transistor Q21 is OFF.
N, the potential of the output line Lout (output PO) is 0.
becomes. At this time, the high side switch transistor Q1 of the second pulser circuit and the third pulser circuit is passed through the output line Lout.
2. Since Q13 is connected to ground, the parasitic capacitances C12 and C13 of each switch transistor Q12 and Q13 are charged by the respective power supply voltages VP2 and VP3 (third stage in FIG. 2). Therefore, even at the first fall of the output pulse PO, the edge is slightly deformed (second stage in FIG. 2). At this time, the previously charged switch transistor Q
The charges charged in the parasitic capacitances C22 and C23 of Q22 and Q23 are not discharged by the respective diodes DS22 and DS23.

Next, when the input signal P1 of the first pulser circuit changes to the negative side c, since the parasitic capacitances C22 and C23 of the low-side switch transistors Q22 and Q23 of the second and third pulser circuits have already been charged, There is no further charging, and the second and third pulser circuits do not become a load on the first pulser circuit. Also, at this time, the parasitic capacitances C12 and C13 of the high-side switch transistors Q12 and Q13 of the second and third pulser circuits that were previously charged are as follows.
Discharge is blocked by diodes DS12 and DS13,
The charged charge is retained as is. Therefore, when the input signal of the first pulser circuit changes to the positive side d, the Q of the high side switch transistors of the second and third pulser circuits is
Similarly, the parasitic capacitances C12 and C13 of Q12 and Q13 are not charged and do not become a load on the first pulser circuit. That is, from the second wave of the input pulse P1 onwards, the switch transistors of the second and third pulser circuits do not become a load on the first pulser circuit, and the output signal PO is output in the correct form (2 in FIG. 2). step).

Note that when the power supply voltage of the first pulsar circuit is higher than the power supply voltage of the second and third pulsar circuits (VP1>
VP2, VP3), the high-side switch transistors Q12, Q13 of the second and third pulser circuits are protected from reverse voltage by diodes and parasitic diodes DK12, DK13 between each and the output line Lout.

[0015]

[Effects of the Invention] In the pulser circuit of the ultrasonic transducer according to the present invention, once the parasitic capacitance of the switch transistor of the pulser circuit other than the pulser circuit in the operating state is charged, each switch transistor and the output point are connected. Since a diode is connected between them, their discharge is prevented. Therefore, the switch transistor of the pulser circuit in the non-operating state is not charged any more, and the waveform of the pulse signal outputted from the pulser circuit in the operating state is not distorted after the second pulse. Also, set the selector switch to the input side (
Since it is provided on the low voltage side), there is no need to use an expensive high-voltage semiconductor switch, and it can output pulses much faster than a relay.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a pulser circuit of an ultrasonic diagnostic apparatus that is an embodiment of the present invention.

[Figure 2] Input pulse P1, output pulse PO, and parasitic capacitances C12, C13, C22, of the pulser circuit of the example
Voltages across C23 VC12, VC13, VC22, V
Graph showing changes in C23.

FIG. 3 is a circuit diagram showing an example of connection when a plurality of pulser circuits are connected to one ultrasonic transducer.

[Explanation of symbols]

VP1, VP2, VP3... Power supply voltage Q11, Q12, Q13, Q21, Q22, Q23... Switch transistor C11, C12, C13, C21, C22, C23... Parasitic capacitance DK11, DK12, DK13, DK21, DK
22, DK23...parasitic diode DS11, DS12, DS13, DS21, DS22,
DS23...Discharge prevention diodes P1, P2, P3...Input pulse signal Lout...Output line PO...Output (ultrasonic transducer drive) pulse signal PUL1,
PUL2, PUL3...Pulser circuit SW1, SW2, SW
3...Pulser circuit changeover switch OSC...Ultrasonic vibrator

Claims (1)

[Claims] Claim 1: In a pulser circuit comprising a plurality of unit pulser circuits connected in parallel to generate pulse signals for driving an ultrasonic transducer, each unit pulser circuit connects a high-voltage side power source and a low-voltage side power source. It is equipped with two switch transistors that are connected in series between each other and open and close in opposite directions in response to the same input signal, and the output to the ultrasonic transducer is taken out from the connection point between both switch transistors. A pulsar circuit for an ultrasonic transducer, further comprising a forward diode between both switch transistors and the output point.