JPS6316130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a selection circuit that selects and drives a transducer array of an ultrasonic probe used in connection with an ultrasonic diagnostic apparatus.

A conventional ultrasonic transducer selection circuit of this type is shown in FIG. Each vibrator in the vibrator array is selectively driven by a selection circuit having the same configuration.
The figure shows only one channel selection circuit therein as a representative example. In Figure 1, _Q1 is a switching transistor that is turned on or off by the selection signal _IN1 , and has a resistor _R1 at its collector.
A high voltage +Vcc (60V) is supplied through the terminal, and its emitter is connected to the common line. On the other hand, a resonator TR having a resistor _R2 connected in series is connected in parallel between the collector and emitter of the transistor _Q1 . As the vibrator TR, a lead titanate zirconate piezoelectric ceramic or the like is used. Furthermore, a diode _D1 is connected to this resonator TR, and a signal source S is connected to this diode _D1 via a capacitor _C1 .
A driving pulse P is applied to the biasing DC power supply V ₁ (+5V) via a resistor R ₃ . In such a configuration, the selection signal
When IN ₁ is LOW, transistor Q ₁ is turned off and diode D ₁ is reverse biased and turned off. In a balanced state, the potential at one end A of the vibrator TR becomes equal to the high voltage Vcc. Therefore, the drive pulse P
is given, it does not appear at point A, and this oscillator
TR is never excited. On the other hand, the selection signal
When IN ₁ becomes HIGH, Q ₁ becomes ON, so D ₁ becomes ON due to the 5V bias voltage of DC power supply V ₁ , and the drive pulse P appears as it is at point A, allowing the vibrator TR to be excited. Select signal like this
By controlling IN ₁ , the vibrator TR can be selected and driven.

However, when IN ₁ is HIGH and Q ₁ is ON,
Resistor R ₁ has a large current Ic (R ₁ = 30KΩ and Ic =
2mA) and the power consumption of the high voltage source is too large. Power consumption can be reduced by increasing the resistance _R1 , but since Vcc is a high voltage, it is necessary to have an extremely large resistance value. However, if a high resistance value is used, the rise time from 0V to Vcc at point A when IN ₁ is set to LOW becomes extremely long. Normal resistance R ₁ is 30KΩ, R ₂ is
Since the capacitance of the resonator TR is 2KΩ and 500PF, the rise time is approximately 15 μs. However, if _R1 is made to have a high resistance, the rise time becomes longer and a problem arises in that high-speed switching drive of the resonator cannot be realized.

It is an object of the present invention to eliminate such drawbacks and to
An object of the present invention is to provide an ultrasonic transducer selection circuit that can reduce current consumption of a power source.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 2 is a block diagram of essential parts showing an embodiment of the ultrasonic transducer selection circuit according to the present invention. Second
In the figure, the same parts as in FIG. 1 are given the same reference numerals, and the explanation thereof will be omitted. Q ₂ is a second transistor, D ₂ is a diode, Q ₃ is a multi-base transistor, and CM is a current mirror constant current circuit. The multi-base transistor _Q3 is formed by connecting the bases of N PNP transistors _Q31 to _Q3N having the same characteristics in common. A high voltage +Vcc is commonly applied to the emitters of the transistors _Q3 , and the collector of the transistor _Q31 is connected to the base of the second transistor _Q2 . The collector of the transistor _Q2 is supplied with the high voltage Vcc, and its emitter is connected to the collector of the first transistor _Q1 via a diode _D2 and to one end of the resonator TR via a resistor _R4 . It is connected to the. These transistors Q ₃₁ , Q ₂ ,
The components consisting of Q ₁ , diodes D ₂ , D ₁ and resistor R ₄ constitute a 1-channel selection circuit.
Although the same circuits are connected to the other transistors Q ₃₂ , Q ₃₃ to _{Q 3N} of the multi-base transistor Q ₃ , these circuits are omitted in the figure to avoid complexity. The constant current circuit CM is a conventionally known constant current circuit in which a DC voltage of +5V is applied to the collector of a diode-connected transistor _Q6 via a resistor _R6 , and its base is connected to the base of the transistor _Q6 . The transistor _Q5 is connected to the common line through the resistor _R5 and the emitter of the transistor _Q6 . The collector of this transistor _Q5 is connected to the collector of a diode-connected PNP transistor _Q4 . Further, this transistor _Q4 has a high voltage Vcc applied to its emitter, and its base is connected to the base of the multi-base transistor _Q3 . In such a constant current circuit CM, the current I ₄ flowing through the transistor Q ₄ is
This is a constant current that satisfies the relationship of the following equation determined by Q ₅ , Q ₆ , the current I ₅ flowing through the resistor R ₅ and the resistor R ₆ .
In this case, transistors Q ₅ and Q ₆ have substantially the same characteristics.

kT/qlnI ₅ /I ₄ =R ₅・I _4where , k is Boltzmann's coefficient T is absolute temperature (〓) q is electron charge ln is natural logarithm symbol The operation of the present invention in this configuration is as follows. explain. When the selection signal IN ₁ is changed from LOW to HIGH, the operation is as follows. Transistor Q ₁ is ON
Therefore, the charge stored in the resonator TR becomes the resistance
Discharge via R ₄ , diode D ₂ and transistor Q ₁ . In this case, transistor Q ₂ is a diode D ₂ , so its emitter potential is higher than its base.
It is in the OFF state. Therefore transistor Q ₃₁
The collector current of all flows directly to the common line through _Q1 without flowing into the base of _Q2 .
In this state, the potential at point A is about 1V due to diode D ₂ and transistor Q ₁ , so diode D ₁ is in the ON state, and pulse P from signal source S appears at point A to drive the resonator TR. Can be done. In this case, the Vcc current I ₃ flowing through the transistor Q ₁ is equal to the current I ₄ flowing through the transistor Q ₄ , for example, R ₅ = 2KΩ, R ₆ =
If it is 10KΩ, it is about 40μA. Next, select the transducer of the other channel, and change the selection signal IN ₁ from HIGH to
I will explain the operation when it goes to LOW. Transistor Q ₁ is turned off, so the current I ₃ of transistor Q ₃₁ flows into the base of transistor Q ₂ and h _FE (Q ₂
current amplification factor) is multiplied by the oscillator through the resistor R ₄
Flows into TR. In this case, diode D ₂ becomes reverse biased, so I ₃ does not bypass transistor Q ₂ and flow into resonator TR. When the resonator TR is charged and has almost the same potential as the base of the transistor Q ₂ (approximately +Vcc voltage), the diode D ₁
is in the OFF state, and the drive pulse P emitted from the signal source S does not appear at point A. In this case, the rise time t from 0V at point A to Vcc voltage is h _FE =
50, I ₃ = 40 μA, and the capacitance C of the resonator TR is 500 PF, then from the relationship h _FE・I ₃・t=C・Vcc, t=15 μs, which is about the same as the rise time in the conventional circuit or slightly faster. It's summery.

As explained above, according to the present invention, the current from the Vcc current flowing through the multi-base transistor _Q3 is sufficiently small, and although the resonator charging current is approximately the same as in the conventional selection circuit, the Vcc power supply It is possible to realize an ultrasonic transducer selection circuit whose overall current consumption can be reduced as a result.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts showing an example of a conventional ultrasonic transducer selection circuit, and FIG. 2 is a block diagram of main parts showing an embodiment of an ultrasonic transducer selection circuit according to the present invention. R ₁ to _{R 6} …Resistor, Q ₁ , Q ₂ , Q ₄ to _{Q 6} … Transistor, Q ₃ … Multibase transistor, Q ₃₁ to
Q _3N ...PNP transistor, TR...resonator, D ₁ , D ₂
...diode, V ₁ ...DC power supply.

Claims (1)

[Claims] Equipped with a multi-base transistor consisting of 1N PNP transistors and a current mirror constant current circuit that makes the current related to the base current of this multi-base transistor a constant current,
For each of N oscillators, the above PNP is always
A second transistor _Q2 that is turned on by the collector current of the transistor and this second transistor
A high voltage is applied through the resistor _R4 connected to the emitter of _Q2 , and when driving, the first transistor _Q1 inserted and connected between the collector of the PNP transistor and the common line is turned on, and the collector of the PNP transistor is turned on. A current is passed directly to the common line to turn off the second transistor _Q2 , and the resistor _R4 is connected between the emitter of the second transistor _Q2 and the collector of the first transistor _Q1 . An ultrasonic transducer selection circuit configured to discharge charges stored in a transducer via a diode _D2 and a first transistor _Q1 .