JPS604625Y2 - Oscillation circuit for ultrasonic atomizer - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an oscillation circuit for an ultrasonic atomizer, and particularly to an excessive starting current prevention device.

Conventionally, in oscillation circuits for automatic ultrasonic atomizers, a Colpitts-type oscillation circuit using an ultrasonic oscillator (crystal oscillator) has been used to stabilize the oscillation frequency, as shown in Figure 1. However, in a configuration in which an ultrasonic transducer is placed at the bottom of a container filled with a liquid such as water in contact with the liquid, as shown in Figure 2, the liquid surface (for example, the water surface) is a flat surface. Furthermore, when oscillation is started, most of the emitted ultrasonic waves are reflected back to the vibrator 1, and as a result, the element impedance decreases significantly due to the piezoelectric effect, and a large current flows, posing the risk of destroying the element.

That is, when oscillation starts, the radiated sound waves cannot penetrate the water surface and most of them return to the vibrator 1.

Therefore, the impedance of the resonator 1 decreases from a fraction to a tenth, and a large current flows through the resonator 1, which also increases the base current of the transistor 2, which further increases the current due to positive feedback. .

As a result, as shown in Figure 4a, a large current flows at the time of startup, and continues until the water surface rises and atomization begins.
There was a risk that it would be destroyed.

At this time, the potential at point B in FIG. 1 becomes as shown in FIG. 4, with a peak due to reflection during startup and during steady state.

The purpose of the present invention is to suppress excessive current caused by reflected waves during startup and steady state using a simple circuit.

An embodiment of the present invention will be described below with reference to FIG.

Note that functional parts that are the same as those in the conventional configuration described above will be described using the same numbers.

In the figure, 3 is the power supply, 4 is the power switch, 5, 6, 7
．． 8 is a resistor for applying bias to transistor 2;
9 is a diode whose anode is connected to the vibrator 1 and its cathode is connected to the connection point of resistors 5 and 6; 10 is a capacitor which is connected in parallel with the resistors 6 and 7 and constitutes a limiter circuit together with the diode 9; 11 and 12 are respectively A stabilizing resistor is connected to the base and emitter of the transistor 2, 13 is a load resistor, and 14.15 is a capacitor connected between the base and emitter of the transistor 2 and the collector and emitter.

In the above configuration, when the switch 4 is turned on and oscillation is started, the potential at point A rises due to the capacitor 10 from the switch on as shown in FIG. 4C.

At this time, the bias potential at point B similarly rises, but since the oscillation amplitude is due to the diode 9, it is clipped in the positive direction by the width of the bias potential difference between point B and point A.

Therefore, at startup, this width is small and gradually increases until it becomes steady, so no overcurrent occurs at startup.

This situation is shown in Figures 4d and e. d is the voltage at point B,
It is clipped together with the peak at startup and the whisker-like peak at reflection.

As a result, the starting current is suppressed as shown in e, and the life of the vibrator 1 is guaranteed.

As described above, according to the present invention, a limiter circuit including a capacitor provided in the bias circuit of this transistor and a diode that sets the voltage of this capacitor to a clip level is connected to a transistor constituting a Colpitts type oscillator circuit. This allows the oscillation to start, i.e.
We achieved two points: by making the clip level sufficiently low at the start of atomization, and by lowering the bias to start the oscillation slowly. It has practical value, such as being able to prevent damage to the vibrator even though it is subject to sound wave reflections, as well as improving the temperature dependence of the oscillation amplitude and the voltage dependence of the oscillation amplitude. It is a great thing.

[Brief explanation of the drawing]

°Figure 1 is a circuit diagram of a conventional oscillation circuit for an ultrasonic atomizer.
Fig. 2 is an explanatory diagram showing the operating state, Fig. 3 is a circuit diagram showing an embodiment of the oscillation circuit for an ultrasonic atomizer of the present invention, and Fig. 4 shows waveforms of various parts of the conventional circuit and the circuit of the present invention. FIG. 1... Ultrasonic vibrator, 2... Transistor, 9... Diode, 10... Capacitor.

Claims (1)

[Scope of utility model registration request] An ultrasonic atomizer comprising an ultrasonic vibrator disposed at the bottom of a container filled with liquid in contact with the liquid, the transistor constituting a Colpitts-type oscillation circuit including the ultrasonic vibrator; Ultrasonic atomization characterized by connecting a limiter circuit comprising a capacitor provided in a bias circuit and a diode that sets the voltage of this capacitor to a clip level, and setting the base voltage of the transistor to be low at the time of activation. Oscillation circuit for equipment.