JPS6023014Y2 - Ultrasonic atomizer - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an ultrasonic atomization device that atomizes liquid such as water, and provides a circuit that protects an output transistor that excites a vibrator from surge voltage.

FIG. 1 shows a conventional embodiment of this type, in which 1 is an AC power source such as a commercial power source, 2 is a power switch, 3 is a power transformer, and 4 is a diode bridge for obtaining DC power from the AC power source 1. and is connected to the secondary side of the power transformer 3.

A parallel circuit of a capacitor 6 and a choke coil 7, a transistor 8, and a choke coil 9 are connected to the diode bridge 4.
The capacitor 5 is connected in series with the capacitor 4, and the capacitor 5 is connected in parallel with the capacitor 4.

10.12 is the above capacitor 5, 6, choke coil 7
．． 9 a capacitor connected to each terminal of the transistor 8 to form a high frequency generation circuit together with the transistor 8; 11 a capacitor 10 and the transistor 8;
13 is a resistor for applying a DC bias to the base of the transistor 8; 14 is a resistor connected between the bases of the transistor 8;
, 15 is a diode and a variable resistor for adjusting the DC bias current of the transistor 8, and 16 is a switch such as a reed switch that is used when the float floating in the atomizing liquid falls below a set level. It is connected between the base of transistor 8 and the negative terminal of the DC power supply.

If you close the power switch 2 in a circuit configured like this,
The vibrator 11 is supplied with high frequency power and atomizes liquid such as water.

Since the vibrator 11 is thermally destroyed when the atomizing liquid is depleted, a reed switch 16 is provided that will act as a stop when the float is lowered, and the transistor 8 is opened to switch off the high frequency power to the vibrator 11. The supply was cut off to protect the vibrator 11 from being destroyed.

However, in such a case, only a small amount of current flows through the secondary side of the power transformer 3 via the resistor 13 and the switch 16, resulting in a nearly no-load state.

In such a state, if you open and close the power switch 2,
Since the excitation current flowing through the power transformer 3 is intermittent, a large surge voltage is generated in the power transformer 3 at the moment the power switch 2 is opened, which causes damage to the PN junction consisting of the collector and base of the transistor 8. There was a drawback.

Therefore, conventionally, it has been essential to connect a surge absorber constituted by a semiconductor or a series circuit of a resistor and a capacitor in parallel with the power transformer 3 in order to protect against such surge voltage.

However, in order to reliably absorb surge voltage with these absorbers, it is necessary to take into account the margin for surge withstand capacity and use a semiconductor absorber for relatively high power or a large capacitor for high withstand voltage. It was also disadvantageous.

This invention was made to solve these drawbacks, and it is possible to provide a circuit that protects the transistor 8 from surge voltage without using an expensive and large semiconductor or resistive capacitor absorber.

FIG. 2 is a circuit diagram showing a specific embodiment of this invention, and hereinafter, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

In FIG. 2, 17 is a resistor connected in series with the resistor 13, and its resistance value is selected as shown in the following equation.

R□7×IoBR-maX≧■BE-oN
... (1) However, R17: Resistance value of resistor 17 IoI3R-maX: Maximum allowable reverse current between the collector and base of transistor 8 vBo-Ou Threshold voltage of transistor 8 Also, switch 16 is connected to resistor 13.17. The configuration is such that it is connected between the point and the negative terminal of the DC power supply.

In such a configuration, if a surge voltage higher than the withstand voltage of the transistor 8 is generated in the transformer 3 by opening and closing the power switch 2, from the secondary side of the transformer 3,
Capacitor 6, parallel circuit of choke coil 7, collector of transistor 8, base of transistor 8, resistor 17, switch 1
A current flows along the path shown by the broken line 6, and a voltage is generated in the resistor 17 with the polarity shown.

When this voltage reaches the threshold voltage of transistor 8, transistor 8 automatically starts excitation operation.

That is, when a surge voltage higher than the withstand voltage of the transformer 8 occurs in the power transformer 3, the surge energy is automatically consumed in the excitation circuit.

In this case, according to the condition of equation (1) above, the transistor 8 starts excitation operation before reaching the maximum allowable reverse current between its collector and base and absorbs the surge energy, thus preventing the transistor 8 from being destroyed by the surge voltage. It is possible.

FIG. 3 shows another embodiment of this invention in which a diode 18 is connected in parallel with the resistor 17 in FIG. 2, so that the DC base bias current of the transistor 8 normally flows through the diode 18. This circuit diagram has the advantage that not only the same effects as the embodiment shown in FIG. 2 can be obtained, but also the allowable design range of the resistor 13 can be expanded.

FIG. 4 is a circuit diagram showing still another embodiment of this invention in which a resistor 17 is connected between the base of the transistor 8 and the cathode of the diode 14, and the same effect as the above embodiment can be obtained. it is obvious.

As described above, this invention has the advantage of absorbing surge energy using extremely simple means without using large and expensive capacitors or surge absorbers, and preventing the transistor 8 from being destroyed by surge voltage.

Further, it goes without saying that the surge voltage is not limited to that generated from the power transformer 3, but the same effect can be obtained for surges external to the AC power supply 1.

Further, in FIG. 4, it goes without saying that a diode 18 may be connected in parallel to the resistor 17 as in FIG. 3.

Note that the excitation circuit for the vibrator 11 is not limited to the one shown in the embodiment of this invention, but may be used regardless of the circuit configuration as long as the transistor 8 excites the vibrator 11 and atomizes the liquid. It is clear that the technique of this invention is applicable.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a conventional embodiment, and FIGS.
The figure is a circuit diagram showing a specific embodiment of this invention. In the figure, the same reference numerals indicate the same or equivalent parts, 8 is a transistor, 11 is a vibrator, 17 is a resistor, and 18 is a diode.

Claims (1)

[Scope of utility model registration request] A device that includes an excitation circuit composed of a transistor and a vibrator excited by the excitation circuit, and supplies high-frequency power to the vibrator to atomize the liquid, wherein a resistor is connected from the base of the transistor. Alternatively, an ultrasonic atomizer characterized in that a circuit leading to an emitter is configured through a parallel circuit of a resistor and a diode, and a switch that opens and closes depending on the increase and decrease of liquid.