JPH053270Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a matching circuit inserted between an ultrasonic transducer using a piezoelectric element and a driving amplifier for driving the ultrasonic transducer.

Generally, ultrasonic cleaners and the like are known as devices that utilize ultrasonic waves. The frequencies traditionally used for these ultrasound devices are 18KHz to 50K
Hz, and using an ultrasonic cleaner as an example, it was difficult to remove minute dirt. Therefore, ultrasonic cleaners using frequencies of about 100 KHz to 1 MHz have recently been used.

However, in order to increase the output of the ultrasonic transducer, it is necessary to increase the output of the driving amplifier placed between the ultrasonic transducer and the oscillator for vibrating the ultrasonic transducer. As a result, this driving amplifier becomes larger or more complicated, resulting in a problem that it becomes more expensive.

Therefore, an object of the present invention is to provide a matching circuit that can increase the output of an ultrasonic transducer without increasing the output of a driving amplifier.

According to the present invention, a matching circuit is inserted between an ultrasonic transducer using a piezoelectric element and a driving amplifier for driving the ultrasonic transducer, and the matching circuit is connected to an input terminal and an output terminal. an ultrasonic transducer and a driving ultrasonic transducer, comprising: a capacitor, an inductor, and a primary winding of the transformer connected in series between the input terminals, and a secondary winding of the transformer connected between the output terminals; A matching circuit with the amplifier is obtained.

The present invention will be explained below with reference to the drawings.

Referring to FIG. 1, as shown, the matching circuit according to the present invention includes a pair of input terminals 1 and a pair of output terminals 2. A capacitor 4 and an inductor 5 are connected in series to the input terminal 1 in the upper part of the figure.
It forms a series circuit. The primary winding of a transformer with a winding ratio of 1:n is connected to terminal 3 of this series circuit, and the output terminal 2 of the secondary winding of the transformer is connected to terminal 3 of the series circuit.
An ultrasonic transducer 7 using a piezoelectric element is connected to. Note that the above-mentioned driving amplifier (not shown) is connected to the input terminal 1.

According to the inventor's experiments, the ultrasonic transducer 7 has an equivalent circuit as shown in FIG. 2a when the frequency of the driving amplifier is 18 KHz to 50 KHz. That is, a circuit is formed in which an inductance 71 and a resistor 72 are connected in series, and a capacitance 73 is connected in parallel. Also, the frequency of the driving amplifier is 100KHz.
It has been found that when the frequency reaches ~1 MHz, the equivalent circuit of the ultrasonic transducer 7 becomes a circuit in which an inductance 74 is connected in series to the equivalent circuit shown in FIG. 2a, as shown in FIG. 2b.

Therefore, by configuring the matching circuit as shown in Figure 1, the frequency of the driving amplifier can be adjusted.
When the frequency is 100KHz to 1MHz, the capacitance (C _M ) of capacitor 4 is the inductance 74 (L _d )
, and the capacitance 73 (C _d ) is canceled by the inductance (L _M ) of the inductor 5 and the inductance (T _M ) of the transformer 6,
The ultrasonic transducer and the matching circuit according to the present invention are coupled by a matching circuit transformer 6.

Here, C _M = 9100 pF, L _M = 11.7 μH, a transformer turns ratio of 8:4, a matching circuit, and a diameter of 40
An experiment was conducted using an ultrasonic vibrator with C _d = 85 μF and a drive amplifier frequency of 450 KHz, in which 16 cylindrical piezoelectric materials of 3 mm in diameter and 3 mm in height were sandwiched between two metal plates. When comparing the cases with and without a matching circuit, the gain increased by 15 to 20 dB.

As explained above, if the matching circuit according to the present invention is used, the gain of the ultrasonic transducer increases.
If the same gain is to be obtained, the output of the drive amplifier can be reduced and the size can be reduced. Also,
The matching circuit according to the present invention is inexpensive because it has a small number of elements.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a matching circuit according to the present invention,
FIGS. 2a and 2b are circuit diagrams showing equivalent circuits when ultrasonic transducers are used at different frequencies. 1...Input terminal, 2...Output terminal, 3...Terminal, 4...Capacitor, 5...Inductor, 6...
...Transformer, 7...Ultrasonic vibrator.

Claims (1)

[Scope of utility model registration request] A matching circuit inserted between an ultrasonic vibrator using a piezoelectric element and a driving amplifier for driving the ultrasonic vibrator at a driving frequency of 100 KHz to 1 MHz, and comprising an input end and an output end. , a matching between an ultrasonic transducer and a driving amplifier, in which a capacitor, an inductor, and a primary winding of a transformer are connected in series between the input terminals, and a secondary winding of the transformer is connected between the output terminals. circuit.