JPH0219905Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to an alarm device that makes a sound to notify when an abnormal load (fork, spoon, etc.) is placed on an induction heating cooker.

Configuration of conventional examples and their problems Conventional induction heating cookers do not need to heat small metal objects, such as spoons or forks, for example, and if heated, people will get burnt if they touch the small metal objects. Therefore, it is necessary to detect in some way that the load is a small object.
Therefore, induction heating cookers detect whether the load is a small metal object by causing the inverter to oscillate and passing current through the load. At that time, the small load generates heat due to the current flowing through the load, but if the detection time is too long, the small load will generate enough heat to burn people, so it is better to make the detection time as short as possible. On the other hand, the load is not necessarily a small item, and it is necessary to detect that the load changes from a small item to a normal pot. Therefore, by periodically oscillating the inverter, it is necessary to detect that the object has changed from a small object to a pot, and at that time, it is necessary to keep the power on at all times. Even though the power is on, if the load on the induction heating cooker is a small item, it is not normal, so it is necessary to notify the user through a notification or the like.

Therefore, intermittent pulses are used to periodically determine whether the load is appropriate or not, and the abnormality notification sound is made to be a discontinuous sound (for example, a peep sound) that is less harsh than a continuous sound (for example, a beep sound).

Hereinafter, a conventional notification device will be explained with reference to FIGS. 5 and 6.

The intermittent pulse is applied to a capacitor 51, the other end of the capacitor 51 is connected to the cathode of a diode 52, and the anode is connected to a one-shot multi-circuit 53.
The output terminal F of the one-shot multi circuit 53, which is connected to the input terminal G of the
An oscillation circuit 54 having a CR time constant is connected to the other end of a capacitor 55 having a CR time constant, and the output of the oscillation circuit is connected to a sounding body 56 .

The operation of the above configuration will be explained based on FIG. 6. When an intermittent pulse is input to the E terminal in FIG. A differential pulse is generated, but the diode 52
Therefore, only the negative pulse is output to the G terminal. The output terminal F of the one-shot multi-circuit 53 goes high and remains high for a time determined by the one-shot multi-circuit 53. The time determined by this one-shot multi-circuit 53 is set to half the period of the intermittent pulse. Then, the output terminal F of the one-shot multi-circuit 53 converts the on-off ratio into an intermittent pulse of 1:1 without changing the period of the intermittent pulse whose on-off ratio is significantly different from 1:1. . The output terminal F of this one-shot multi-circuit 53 is connected to an oscillation circuit 54 having a CR time constant that determines the frequency of the sounding body.
Since it is connected to the other end of the CR time constant capacitor 55, when the output terminal F is low, the oscillation circuit 5
The output of No. 4 becomes low and oscillation is suppressed, so that no oscillation waveform is applied to the sounding body and no sound is produced. Further, when the output terminal F is high, an oscillation waveform is outputted to the output terminal H of the oscillation circuit 54, and the oscillation waveform is applied to the sounding body, producing a sound. In this way, by repeating the on/off ratio of the output terminal F at a ratio of 1:1 (duty: 50%), the sounding body oscillates a discontinuous sound.

The reason why the one-shot multi-circuit 53 is provided is that the on-time of the intermittent pulse is generally
This is because the pulse is not enough to operate the oscillation circuit 54, so it is converted into a pulse (on/off ratio of about 1:1) having a sufficient on time for the operation of the oscillation circuit 54.

In this way, conventionally, when detecting intermittent pulses and generating discontinuous sound, one-shot multi-circuit 5 is used.
Two oscillation circuits, an oscillation circuit 3 and an oscillation circuit 54, were required.

Purpose of the invention In this invention, we focus on the oscillation circuit that determines the period of the intermittent pulse and the frequency of the sounding body that has a CR time constant circuit, and change the period of the intermittent pulse whose on/off ratio is far from 1:1. without any
It is an object of the present invention to provide a simple and inexpensive notification device without using a one-shot multi-circuit, which is a circuit that converts an on-off ratio into a 1:1 intermittent pulse.

Structure of the invention The alarm device of the invention connects a capacitor and the cathode of a diode to a switching element that switches using intermittent pulses with an on/off ratio far different from 1:1, and the anode of this diode is connected to a CR time constant circuit. It is connected to one end of a capacitor of an oscillation circuit that determines the frequency of the sounding body, and the sounding body is connected to the output of this oscillation circuit to generate discontinuous sound.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, 1 is a transistor which is a switching element. An intermittent pulse is applied to the base of this transistor 1, and a capacitor 2 and the cathode of a diode 3 are connected to the collector of the transistor 1, which is a switching element. is connected to one end of the comparator 9 of an oscillation circuit 12 having a GR time constant circuit formed by a capacitor 4 and resistors 7 and 11, and a sounding body 10 made of a piezoelectric buzzer is connected to the output of this oscillation circuit 12. . The + terminal of comparator 9 is connected to resistors 5, 6, and 8, and resistor 5
The other end of the resistor 6 is connected to the high voltage side of DC, the other end of the resistor 6 is connected to the ground, and the other end of the resistor 8 is connected to the output of the comparator 9, thereby setting a reference potential of the oscillation circuit 12.

In the above configuration, the base B of transistor 1
When the intermittent pulse shown in FIG. 3 is applied to , transistor 1 is ON during the rectangular pulse, so capacitor 4 of the CR time constant circuit of oscillation circuit 12 passes through diode 3 and transistor 1, and capacitor 2 passes through transistor 1. It is discharged through 1.
When the rectangular pulse of the intermittent pulse disappears, the capacitor 4 is charged through the resistors 7 and 11, and the capacitor 2 is charged through the resistors 7 and 11 and the diode 3. When the potential of capacitor 4 rises to the potential set by resistors 5 and 6 (A in Figure 2), the output of comparator 9 becomes Low, and capacitor 4 is discharged from the output of resistor 7 and comparator 9. 2 remains charged due to diode 3 without being discharged. Now, when capacitor 4 discharges and drops to the potential set by resistors 5, 6, and 8 (b in Figure 2), the output of comparator 9 becomes
The signal becomes High, and the capacitor 4 is charged again through the resistors 7 and 11, and this process is repeated until the output of the comparator 9 generates a rectangular wave as shown in FIG. After a while (after an interval of intermittent pulses), a rectangular pulse is also applied to the base of transistor 1. Then, transistor 1 turns on, the voltage of capacitor 4 is discharged by diode 3 and transistor 1, capacitor 2 is discharged by transistor 1, and the potential becomes almost the same as that of the ground, the output of comparator 9 remains High, and sounding element 10 Don't notify. When the rectangular pulse applied to the base of transistor 1 disappears, capacitor 2 is charged through resistors 7 and 11 and diode 3, and capacitor 4 is charged through resistors 11 and 7, reaching the potential set by resistors 5 and 6. Then, the device oscillates and makes a notification repeatedly as described above. In this way, the capacitor 2 , 4 and the time constants of the resistors 7 and 11 to make the sounding element 10 sound (charging from the potential in Figure 2 B to the potential in Figure 2 A),
The capacitor 4 is charged by the time constant of the capacitor 4 and the resistors 7 and 11, and a continuation notification sound is generated.

A specific example of the present invention is a small object detection alarm circuit for an induction heating cooker. Induction heating cookers are equipped with a small object detection circuit that detects small object loads and stops oscillation. While detecting small objects, intermittent pulses are generated that are repeated at intervals of about 1 second to 1.5 seconds, which is the time required for reliable detection. If the duty of the notification period of the notification sound circuit of the present invention is set to 50% by using the interval of the intermittent pulse, the interval of the intermittent pulse becomes 1.
When the time is 0.5 seconds, the sound is repeated for 0.5 seconds, then stopped for 0.5 seconds, and a discontinuous sound (piyo-piyo sound) is generated.While the intermittent pulse is occurring, it is considered that the small object detection alarm sound circuit is configured. will be done.

Effects of the invention According to the alarm device of the present invention, conventionally two oscillation circuits were required to generate intermittent notification sounds, but by using the interval of intermittent pulses, one oscillation circuit can generate intermittent notification sounds. It can generate sound, the circuit can be made simple and inexpensive, and its effects are great.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of an alarm device showing an embodiment of the present invention, Fig. 2 is a voltage waveform diagram of the capacitor of the CR time constant circuit in the oscillation circuit, and Fig. 3 is an intermittent pulse applied to the base of the transistor. 4 is a voltage waveform diagram of a sounding body, FIG. 5 is a circuit diagram of a conventional notification device, and FIG. 6 is a voltage waveform diagram of various parts of the same device. 1...transistor (switching element), 2
... Capacitor, 3 ... Diode, 12 ... Oscillation circuit, 10 ... Sounding body.

Claims (1)

[Scope of utility model registration request] A capacitor and a diode cathode are connected to a switching element that switches using intermittent pulses with an on/off ratio far different from 1:1, and the anode of this diode has a CR time constant circuit to determine the frequency of the sounding body. An alarm device that is connected to one end of the capacitor of an oscillation circuit, and a sounding element is connected to the output of this oscillation circuit to generate a discontinuous sound.