SU1226280A1 - Device for exciting piezotransducers - Google Patents

Abstract

The invention relates to non-destructive testing and can be used: V / / used in ultrasonic defect detectors, ultrasound velocity meters, etc. The purpose of the invention is the extension of functionality due to the use of low-voltage power sources combined with inductance and self-induction emf to excite the piezoelectric element. A device for exciting a piezoelectric transducer contains an inductance connected between a blocking generator and a power source, which makes it possible to obtain a high-voltage pulse with a self-induction EMF for energizing the piezoelectric converter, several tens of times the voltage of the power source. 1 il. with S (L

Description

b

l-j

and

where p

ten

fS

20

15

1225280

The invention relates to a non-breaking current control and can be applied in ultrasonic defect-detectors, ultra-sound velocity meters, and the like.

The purpose of the invention is to expand the functional capabilities by using low-voltage power sources in conjunction with inductance and self-induction EMF to excite a piezoelectric transducer. . The drawing shows a circuit diagram of the device.

The VT transistor, the blocking transformer Tr, the capacitor G1, the diode D2, and the resistance R1 form a blocking generator in the autogeneration mode. The inductance L is connected in series with the blocking generator and the power source U, is damped by the R2-D1 chain, and the power source is shunted by the capacitor C2. The piezoelectric transducer P is connected either parallel to the blocking-generator transistor, or in the position P parallel to the inductance L.

During the generation of a pulse by a blocking generator, the current through the inductance L increases to a value that depends on the duration of the pulse of the blocking generator and the resistance of the circuit L-Tp-VT. Here the transistor of the blocking generator closes, interrupting the current through inductance. This moment is fundamental to the operation of the circuit. The amplitude of the excitation pulse on the piezoelectric transducer, as well as the steepness of the leading front of this pulse, depends on how quickly the transistor closes. Therefore, as a key transistor, it is necessary to set one that holds the maximum required current, is high-frequency, provides speed, and also withstands a high voltage, to which the piezoelectric transducer is charged during a charge from the EMF of self-induction that occurs when the current through the inductance breaks . In this case, the magnitude of the voltage up to which the piezotransducer is charged is determined from the condition of the transition of the magnetic field energy of inductance L, according to which at the moment of breaking of flow

thirty

The current is connected to the power supply f of the coil chain for this friction. A maxistor is made for a voltage greater than a character; a character is longer than a circuit. For an hour, the sound capacity is related to several

When you go through the device, the voltages are

Before time, if you are already running the generator. Into p conversion length

Prev 55 you D1, R destroy equals anyone with

35

40

45

50

, in electric field transformer: .2 .. g

W ™ I p

hO 2

W,

 2

and 3

OK

B-,

where p

S

0

five

0

the characteristic resistance of the circuit formed by the inductance and capacitance of the circuit along which the capacitance charge is charged, Ohm.

The current in the circuit at the moment of rupture reaches its maximum value, determined by the voltage of the power source and the active resistance f of the inductance-collector winding of the blocking transformer - collector junction of the transistor, while the transistor is in saturation. This resistance can be made small to ensure the maximum current through the transistor. It follows that the voltage U on the piezoelectric transducer is greater than the voltage of the power source CDd by as many times as the characteristic resistance p is greater than the active resistance of the TOKai circuit through the inductance. For frequencies used in ultrasonic technology and the usual values of piezo transducer capacitance, this ratio can be achieved several hundred times.

When using the proposed device, a high-voltage power source or a voltage converter is not required, the calculated value of the amplitude of the excitation is easily obtained.

The proposed device is also a synchronizer, since the blocking generator operates in self-oscillating mode. If external synchronization is more necessary, then a blocking oscillator with external synchronization is used, starting it on the basis of clock pulses. As a result, the piezo-g converter is excited by a pulse of half a period.

The proposed damping elements 5 D1, R2 improve the pulse shape by destroying the tail, and R 2 must be equal to half the characteristic resistance. Turn on piezo 5

0

five

0

the converter shown by the dotted line changes the polarity of the excitation pulse relative to the upper plate.

Claims (1)

Claims An apparatus for driving piezoelectric transducers, comprising: source 1226,280 Power nickname and blocking generator, characterized in that, in order to expand its functionality, it is equipped with an inductive; between the power supply and the blocking generator.