JPS627565B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control device using a heat-sensitive thyristor.

FIG. 1 is a circuit diagram of a temperature control device using a conventional heat-sensitive thyristor. In the figure, an AC power supply 1, a heater 2, and a triax 3 that controls the AC power supplied to the heater 2 are connected in series, and the _T2 terminal and gate G of the triax 3 are connected by rectifier diodes 31, 32, 33, and 34. The auxiliary thyristor 6 for triggering the triax 3 and the heat-sensitive thyristor 4 for detecting the ambient temperature are connected to the AC input of the diode bridge constructed in parallel with the output of the diode bridge through current limiting resistors 22 and 21, respectively. Connecting. Furthermore, when a voltage is applied between the anode of the heat-sensitive thyristor 4 and the gate of the auxiliary thyristor 6, the voltage phase advances when the heat-sensitive thyristor 4 is off, and a voltage equal to or higher than a predetermined voltage (Zener voltage) is applied to the gate of the auxiliary thyristor 6. A Zener diode 5 for supplying the heat is connected so that the heat-sensitive thyristor side becomes the anode. A resistor 8 for temperature setting and a capacitor 9 for preventing malfunction of the heat-sensitive thyristor due to noise are connected between the anode and gate of the heat-sensitive thyristor 4. Note that the resistors 23 and 7 connected between the gate and _T1 terminal of the triac 3 and between the gate and cathode of the auxiliary thyristor 6 are for preventing malfunction.

For example, consider the case where the conventional technology is applied to a thermostatic chamber. When the current temperature is lower than a predetermined temperature, the heat-sensitive thyristor 4 is in an off state, so a full-wave rectified voltage waveform is applied between the anode and cathode of the auxiliary thyristor 6, and is also applied to the gate. However, in the phase of zero voltage, that is, when the full-wave rectified voltage is below the Zener voltage, no voltage is applied to the gate of the auxiliary thyristor 6, but the phase advances.
When the applied voltage becomes equal to or higher than the Zener voltage, a current flows through the gate of the auxiliary thyristor 6, the auxiliary thyristor 6 is turned on, and the triac 3 is triggered. Therefore, power continues to be supplied to the heater 2.

When the temperature rises to a predetermined temperature or higher, the heat-sensitive thyristor 4 is turned on and the gate cathode of the auxiliary thyristor 6 is bypassed, so no current flows through the gate. Therefore, the auxiliary thyristor 6 is turned on, and since no current flows through the gate of the triax 3, power is no longer supplied to the heater 2, and the temperature inside the thermostatic oven drops.

Next, when the temperature drops below a predetermined temperature, the heat-sensitive thyristor 4 is turned off again, and power is supplied to the heater 2. The temperature setting can be adjusted by means of a resistor 8.

However, in the conventional circuit shown in Fig. 1, the switching elements such as the auxiliary thyristor 6 and the heat-sensitive thyristor 4 are connected to the output side of the diode bridge and are floating from the ground line of the AC power supply 1, resulting in surge voltage and noise voltage. However, it has the disadvantage of being prone to false triggers. For example, if a stray capacitance exists between the gate and ground of the heat-sensitive thyristor 4, a current flows to the ground through the anode of the heat-sensitive thyristor 4 and the gate stray capacitance, causing the heat-sensitive thyristor 4 to malfunction. When the temperature rises and the heat-sensitive thyristor 4 is about to switch, it may operate asymmetrically and be on only for half a wave.

In addition, the following is a second drawback. In the circuit shown in Figure 1, the triax 3 is not triggered at the zero phase of the AC power supply voltage, but is triggered when the zener voltage of the zener diode 5 is reached, resulting in a slightly phase-controlled state and harmonics. This occurs and becomes radio noise. For this reason,
In reality, a filter not shown in FIG. 1 is required in the radio wave circuit.

The present invention has been made in order to eliminate the first drawback of the above-mentioned conventional ones.The heat-sensitive thyristor is set at the same potential as the main line of the AC power supply, and when the tri-ac is triggered in a negative cycle, it is always triggered in the next positive half cycle. Trigger with . By employing a so-called dependent trigger system, the purpose of this invention is to reduce malfunctions due to external noise and surge voltage, and to provide a temperature control device without half-wave operation.

FIG. 2 is a circuit diagram of a temperature control device that is an embodiment of the present invention. In FIG. 2, AC power supply 1,
A triax 3 and a heater 2 are connected in series, a first series body of a heat-sensitive thyristor (heat-sensitive switching element) 4 and a resistor 21 for detecting the temperature of the thermostatic oven is connected in parallel with the AC power supply 1; an auxiliary thyristor (first semiconductor switching element) 6 for triggering the triax 3; a capacitor 11 for auxiliary triggering of the triax 3;
A second series body of a resistor 13 and a rectifier diode 17 for charging the capacitor 11 is connected in parallel with the AC power supply 1.

On the other hand, when a voltage higher than a predetermined voltage (Zener voltage) is applied between the gate of the auxiliary thyristor 6 and the anode of the heat-sensitive thyristor 4, the phase of the voltage advances when the heat-sensitive thyristor 4 is off, and the gate current flows to the gate of the auxiliary thyristor 6. A Zener diode 5 for supplying is connected so that the heat-sensitive thyristor 4 side becomes a cathode.

Furthermore, the collector of the transistor (second semiconductor switching element) 12 used as a switching element for performing the dependent trigger of the triax 3 is connected to the capacitor 11 through a rectifier diode 18.
and the rectifier diode 17, and the emitter of the transistor 12 is connected to the AC power supply 1 and the heater 2.
Transistor 1
At the base of 2, when the phase of the power supply voltage is reversed, the transistor 12 is turned on instantaneously, and the TRIAT 3 is activated.
It is connected to another AC power supply terminal through a resistor 14 so that current flows through the gate of the AC power supply terminal. Also, the gate of triac 3 is connected to capacitor 11 through resistor 15.
and the anode of the auxiliary thyristor 6.

Note that the diode 16 connected in reverse between the base and emitter of the transistor 12 is connected to the transistor 12.
This is a diode to prevent voltage breakdown. Further, when the ratio between the resistor 7 and the resistor 21 is not very large, a rectifier diode is connected in series with the resistor 21 to prevent voltage breakdown of the heat-sensitive thyristor 4. Other symbols are the same as those explained in FIG. The operation of the present invention will be explained based on FIG. First, let us consider the case where the temperature of the constant temperature bath is lower than a predetermined temperature. Since the heat-sensitive thyristor 4 is in the off state during the negative half cycle period of the AC power supply 1, when the phase of the power supply voltage advances from zero and becomes higher than the Zener voltage of the Zener diode 5, the resistance 21 is removed from the AC power supply 1. , a gate current flows through the Zener diode 5 to the gate of the auxiliary thyristor 6. Therefore, the auxiliary thyristor 6 is turned on, and the gate current flows to the triax 3 in the loop of AC power supply ₁ → heater 2 → T1 terminal of triax 3 → gate → resistor 15 → auxiliary thyristor 6 → AC power supply 1, and triax 3 is turned on. state. Therefore, electric power is supplied to the heater 2. During this negative half cycle, capacitor 11 is charged to the polarity shown through resistor 13 and rectifier diode 17. Next, when the power supply voltage is reversed and shifts to a positive half cycle period, current flows through the resistor 14 to the base of the transistor 12, and the transistor 12 is turned on. Therefore, the charge in the capacitor 11 is transferred to the capacitor 11 → rectifier diode 18 → transistor 12 → heater 2 → _T1 terminal of triac 3 → gate → resistor 15 → capacitor 11, and the gate current flows to triac 3, resulting in a positive half cycle. Triack 3 is triggered at the beginning of , and following the negative half cycle,
Even in the positive half cycle, the triac 3 is turned on and power is supplied from the AC power source 1 to the heater 2.
In this way, when the temperature is low, the heat-sensitive thyristor 4 is in the off state, so the heater 2 continues to heat and the temperature rises.

Next, when the temperature rises and exceeds a predetermined value,
Since the heat-sensitive thyristor 4 is turned on and the gate of the auxiliary thyristor 6 is short-circuited, the auxiliary thyristor 6 is not turned on.

Therefore, since the triator 3 is not triggered, it is not turned on, and no power is supplied to the heater 2. If the auxiliary thyristor 6 and the triax 3 are off, the capacitor 11 will not be charged during the negative half cycle, so even if the transistor 12 is turned on during the next positive half cycle, the triax 3 will have no gate current. Therefore, no power is supplied to the heater 2. In this way, when the temperature is high, no power is supplied to the heater 2 during both positive and negative cycle periods.

Next, when the temperature falls below the predetermined value again, the heat-sensitive thyristor 4 is turned off again and power is supplied to the heater 2.

As described above, the triax 3 is repeatedly turned on and off, and the temperature is maintained at a predetermined value.

FIG. 3 shows another embodiment of the invention. FIG. 3 shows a simplified method of charging and discharging the capacitor 11 shown in FIG. capacitor 11
is charged by rectifier diode 16 and transistor 12
through the base collector and resistor 13,
Discharge occurs through the rectifier diode 19 and the transistor 12. The other operations are exactly the same as those shown in FIG.

Next, in the circuit shown in FIG. 2, if a reverse blocking thyristor is connected in place of the transistor 12 and the rectifier diode 18, and the gate of this reverse blocking thyristor is connected to the resistor 14 in place of the base of the transistor 12, the same operation can be obtained. It will be done.

Furthermore, although the auxiliary thyristor 6 is used as the first semiconductor switching element in FIGS. 2 and 3,
A similar operation can be obtained by replacing it with a transistor. Further, instead of the heat-sensitive thyristor 4, a heat-sensitive switching element such as a thermal reed relay may be used. Further, in the above embodiment, a lamp may be provided in parallel with the heater 2 in order to know the heating state of the heater 2, and in this case, good monitoring without flickering of the lamp can be performed.

Although the present invention has been described using a constant temperature bath as an example, the temperature detected by the heat-sensitive thyristor may be any of air, a hot plate, a wall surface, and liquid temperature such as water temperature and oil temperature.

In the explanation of FIG. 2, one heat-sensitive thyristor 4 is used, but if a large number of temperature detection points are required, a plurality of heat-sensitive thyristors 4 may be provided, and they may be arranged in parallel or in series depending on the purpose.

Furthermore, although the present invention has been described as a temperature control device using a heater as a load, it can also be applied to a temperature alarm device and the like. For example, if an AC buzzer or a lamp is combined as a load, the temperature will rise and when the temperature suddenly reaches a precipitous temperature, an alarm can be issued by sounding a buzzer or lighting a lamp.

Furthermore, when a fan is combined as a load, when the temperature exceeds a predetermined temperature, the fan starts rotating and provides ventilation, and the fan rotates according to the indoor temperature.
It can also be applied to fan units (living masters, etc.) that adjust indoor temperature, air conditioners, etc.

As explained above, this invention is constructed by connecting a heat-sensitive switching element in parallel to an AC power supply, so that the terminals of the heat-sensitive switching element do not come off the line of the AC power supply, and therefore, external noise and surge voltage are reduced. Since malfunction caused by the heater is prevented and the heater operates stably, and since the first and second semiconductor switching elements and the capacitor are configured to supply gate current to the triax, a full-wave current always flows through the heater. This has the effect of preventing the phenomenon of temporary half-wave conduction during the ON/OFF transition of the triax, and furthermore, by using a semiconductor switching element as the switching element that supplies the gate current to the triax, errors due to self-heating can be reduced. This has practical effects such as being able to reduce the size of the capacitor and making the size of the capacitor smaller.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional temperature control device, Fig. 2 is a circuit diagram showing a temperature control device which is an embodiment of the present invention, and Fig. 3 is a circuit diagram showing another embodiment of the present invention. be. In the figure, 1 is an AC power supply, 2 is a heater, 3 is a triac, 4 is a heat-sensitive thyristor, 5 is a Zener diode, 6 is a thyristor, 11 is a capacitor, 1
2 is a transistor. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. An AC power supply, a load means supplied with power from the AC power supply and for raising the temperature, a triax for controlling power supplied to the load means by turning on and off, and a triax for the AC power supply. are connected in parallel through a resistor, and detect the temperature generated from the load means, and turn on when the temperature exceeds a predetermined temperature, and turn off when the temperature drops below a predetermined temperature.
a first semiconductor switching element that is turned on when the heat-sensitive switching element is off during a negative half cycle of the AC power source and supplies a gate current to the triax; means for applying a signal to a control terminal of the first semiconductor switching element when the switching element is off; and means for applying a signal to a control terminal of the first semiconductor switching element when the switching element is turned off; a capacitor that supplies a gate current to the triax by charging when the alternating current source reaches a positive half cycle and discharging when the alternating current power supply enters a positive half cycle;
When the AC power source reverses to a positive half cycle,
A temperature control device comprising a second semiconductor switching element for discharging the charge in the capacitor and supplying current to the gate of the triac. 2. Claim 1, wherein the first semiconductor switching element is composed of a thyristor.
Temperature control device as described in section. 3. The temperature control device according to claim 1, wherein the first semiconductor switching element is composed of a transistor. 4. Claim 1, characterized in that the second semiconductor switching element is constituted by a thyristor.
Temperature control device as described in section. 5. The temperature control device according to claim 1, wherein the second semiconductor switching element is composed of a transistor.