JPH0123579Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an oscillator protection circuit used in ultrasonic cleaners, humidifiers, etc., which oscillates at a high frequency when in contact with liquid.

When the amount of liquid in contact with such an oscillator decreases, the load becomes light and the input becomes excessive, cooling becomes poor and the humidity of the oscillator increases significantly, resulting in destruction. This device was devised with the aim of creating a protection circuit that automatically stops the oscillator and prevents damage when the liquid level drops to a dangerous level. The device detects the voltage that is added to the oscillator, increases in a dangerous state, and is lower in a safe state, and inputs it into a differential amplifier to operate the oscillator normally in a safe state, but cuts off the oscillator from the power supply in a dangerous state. .

Next, this invention will be explained with reference to an example in which a circuit is illustrated.

In the drawing, 1 is an oscillator, 2 is a protection circuit, and 3
is a power supply unit for operating the protection circuit 2, which is connected to the power supply terminals 4 and 5 connected to the 100V AC oscillator power supply through a timer contact 6, a transformer 7 connected to the rectifier 8, and then an output terminal. 24V direct current to be applied to the protection circuit 2 is taken out from 9 and 10.
Output terminals 9 and 10 are A and B of protection circuit 2, respectively.
Connected to points. Output terminal 10 and point B are grounded.

The oscillator 1 is connected to power terminals 4 and 5 via a timer contact 6 provided for cleaning, humidification, etc. for a predetermined period of time, and a normally open relay contact 11a connected in series with the timer contact 6.
, and drives a vibrator 13 having a capacitor 12 connected in series. capacitor 1
Resistors 14 and 15 connected in series are connected in parallel to both ends of the transistor 2, and the middle thereof is connected to the base of a buffer transistor 16.
The emitter of transistor 6 passes through a rectifying diode 17 to the collector of transistor 18 and transistor 19.
connected to the base of 20 resistors, 2 capacitors
6 is for smoothing. The emitter of the transistor 19 and the emitter of the transistor 22 are grounded via a resistor 23, and both transistors 19, 2
2 constitute a differential amplifier. 24 is a Zener diode. Since the base of the transistor 25 is connected to the collector of the transistor 22, when the transistor 22 becomes conductive, the transistor 25 also becomes conductive, and furthermore, the transistor 26 is made conductive, causing current to flow through the relay 11, and contact 1 of the transistor 25 becomes conductive.
I am trying to close 1a.

The operation of the circuit configured in this way is as follows.

1 When the vibrator is in contact with a sufficient amount of liquid, connect terminals 4 and 4 to an AC 100V power source, start the timer, and close timer contact 6. Current flows to the primary coil of transformer 7, and the rectifier 8, a 24V DC voltage appears at output terminals 9 and 10, and this is the point A and B (ground) of the protection circuit 2.
added to.

In this state, the oscillator 1 is still not operating, so the voltage across the capacitor 12 is zero, the transistor 16 is not conducting, and the voltage v ₃ applied to the base of the transistor 19 is also zero. Therefore, in this state, the other transistor 22 that constitutes the differential amplifier together with the transistor 19 becomes conductive, which causes the transistor 25 and the transistor 26 to become conductive.
conducts, current flows through the relay 11 and closes the relay contact 11a, and 100V AC power is supplied to the oscillator 1 from the power terminals 4 and 5 to drive the vibrator 13.

2. When the liquid is insufficient or runs out When the liquid decreases under the above-mentioned operating conditions of the vibrator, cooling becomes poor and the load on the vibrator becomes lighter, causing more power to be supplied to the vibrator than necessary and causing the capacitor to overflow. The voltage across 12 increases. As a result, the voltage v ₂ between the resistors 27 and 28 connected in series with the Zener diode 24 increases, and the voltage v ₃ at the collector of the transistor 18 also increases. This progresses to the Zener voltage of the Zener diode 24.
When v ₃ > v ₁ with respect to v ₁ , transistor 19 becomes conductive and transistor 22 is cut off, so transistors 25 and 26 are cut off, current no longer flows through relay 11, and oscillator 1 stops. , transistor 18 conducts and transistor 1
9 is kept conductive. Even if the relationship of v ₃ >v ₁ disappears after that, the relationship of transistor 19 being turned on and transistor 22 being cut off is maintained.

In this way, the oscillator stops when the amount of liquid in contact with the vibrator decreases, so the oscillator is protected from the risk of destruction.

To restart the oscillator after replenishing the liquid and bringing it into a safe state, turn off the power applied to power supply terminals 4 and 5, and the effect of the above protection circuit will disappear. It is possible to perform safe operations under certain conditions.

As described above, the oscillator protection circuit of this invention automatically stops the oscillator and protects it from destruction when the liquid in an ultrasonic cleaner, humidifier, etc. runs low. It has great practical effects as a safe protection circuit.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing the oscillator protection circuit of this invention. 1: Oscillator, 2: Protection circuit, 3: Power supply, 4,
5: Power terminal, 6: Timer contact, 7: Transformer,
8: Rectifier, 9, 10: Output terminal, 11: Relay, 11a: Relay contact, 12: Capacitor, 1
3: Oscillator, 14, 15: Resistor, 16: Buffer transistor, 17: Rectifier diode, 1
8, 19: Transistor, 20: Resistor, 21: Capacitor, 22: Transistor, 23: Resistor, 2
4: Zener diode, 25: transistor,
26: Transistor, 27, 28: Resistor.

Claims (1)

[Scope of utility model registration request] 2 by detecting the increase in voltage applied to the capacitor 12 connected in series to the vibrator 13 driven by the oscillator 1.
In addition to the differential amplifier constituted by two transistors 19 and 22, this differential amplifier is connected to a relay 11 which, when the oscillator 1 is in a safe state, causes one transistor 22 to conduct due to the low voltage applied to the capacitor 12, thereby energizing the oscillator 1. A circuit that conducts current and, when the oscillator is in a dangerous state, causes another transistor 19 to conduct due to an increase in the voltage applied to the capacitor 12 to cut off the current in the relay 11, and maintains the conductive state of the other transistor 19 at this time. An oscillator protection circuit consisting of an attached oscillator.