JPS61134817A - Temperature controlling device - Google Patents

Abstract

PURPOSE:To reduce an overshoot phenomenon of a heating means by obtaining a saw tooth reference voltage by an oscillating circuit. CONSTITUTION:A temperature controlling device is constituted of a transistor (TR) Q1 connected to a constant-voltage power source E through a switch 1, a heater 2 a thermister 4 for detecting a temperature in a tank 3, a conparator 5, and an oscillating circuit 6 for generating saw tooth reference voltage. In this state, when the switch 1 is turned on, the conparator 5 compares a reference voltage from the oscillating circuit 6 with a temperature detecting voltage from the thermistor 4,and controls conduction to the heater by bringing the TR Q1 to on-and-off control. Said referecne voltage has a saw tooth waveform, therefore, even after having reached a set temperature, the heater 2 executes turning-on and turning-off frequency, and the temperature in the tank 3 is kept constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a temperature control device that maintains the temperature inside the tank at a predetermined temperature by, for example, disposing a heater in the tank and controlling the heater. be.

[Conventional technology]

A conventional temperature control device of this type is one shown in FIG. 6, for example. This shows a case where the temperature of the air in one tank is controlled. In the figure, an EFi constant voltage power supply is connected in series with a heater 2 via a switch 1 and a transistor Q. . This heater 2
A thermistor 4 for detecting the temperature of the air is installed in the tank 3 in which the air is placed. One terminal of the thermistor 4 is connected to the negative terminal of the power source ε, and the other terminal is connected to the inverting (c) input terminal of the comparator 5. Further, a series circuit of resistors R1 and R3 is connected in parallel with the power supply E, and the connection point of the resistors R, , R, is connected to the non-inverting (A) input terminal of the comparator 5. The output terminal of the heater 5 is connected to the pace of the transistor Q through the resistor R, and controls the heater 2 (QN-
OFF) is performed. R and In2 are resistors connected between the inverting input terminal and output terminal of the comparator 5 and the positive side of the power supply E, respectively.

In the temperature control device having the circuit configuration as described above, the temperature of the air in the tank 3 is increased by the heater 2, and this temperature is detected by the L thermistor 4, and feedback control is performed. First, when the switch 1 is turned on, a voltage obtained by dividing the voltage of the electric current *E by the resistors R and R7 is applied to the non-inverting input terminal of the comparator 5. This voltage becomes a constant reference voltage and becomes a set value for the temperature of the air in the tank 3, which is the controlled object. On the other hand, the temperature of the air in tank 3 is determined by thermistor 4.
At this time, the thermistor 4 is detected according to the temperature.
resistance value changes. As a result, a detection voltage corresponding to the temperature of the air in the tank 3 is applied to the inverting input terminal of the comparator 5.

Here, the comparator 5 controls the heater 2 by comparing the reference voltage and the detected voltage. That is, when the voltage at the inverting input terminal of the comparator 5 is higher than the voltage at the non-inverting input terminal, that is, when the actual temperature of the air in the tank 3 is lower than the set temperature of the air, the m cover of the comparator 5 is L”
(Low level) Toner transistor Q1 is ONL and heater 2 is ON. This heater 2 is turned on and the tank 3
When the temperature of the air inside increases, the resistance value of the thermistor 4 decreases, and the voltage at the inverting input terminal of the comparator 5 decreases. Then, when the voltage becomes lower than the temperature set value (voltage at the non-inverting input terminal), the output of the comparator 5 becomes 'H.
” (high level) and transistor Q becomes 0FFL.
,, the heater 2 is turned off.

Next, the temperature of the air in the tank 3 is assimilated with the temperature of the air around the tank 3 and gradually decreases, and when it becomes lower than the set temperature again, the heater 2 is turned on and the temperature of the air in the tank 3 rises again. . In this way, the heater 2 is 0N-O near the set temperature.
By repeating FF, the temperature of the air in the tank 3 is kept constant. FIG. 7 is a graph showing the relationship between the temperature ff) of the air in the tank 3 and time (1) and the timing of turning on and off the heater 2. As mentioned above, when switch 1 is turned on at time t1, heater 2 is turned on,
The temperature of the air in the tank 3 rises to the set value T. At the time t when this set temperature is reached, the heater 2 is turned off.
Since the temperature of the heater 2 itself does not drop rapidly, the air in the eye tank 3 is heated for a while and the temperature further rises. Because of this overshoot phenomenon, the temperature of the air in the tank 3 does not suddenly fall below the set value even when the heater 2 is turned off, but becomes lower than the set value after time t has elapsed. In this way, heater 2 is turned on.

By repeating OFF, the temperature of the air in the tank 3 is maintained at the set value.

[Problem that the invention seeks to solve]

In the above-mentioned temperature control device, since the heater 2 is controlled by comparing the detected voltage corresponding to the actual temperature with a fixed reference voltage, there is a large overshoot due to residual heat of the heater 2, and the stable There was a problem that temperature control was not possible.

The present invention has been made by focusing on the problems of the conventional devices, and aims to provide a temperature control device that can reduce overshoot and perform stable temperature control.

[Means for solving problems]

The temperature control device of the present invention includes a means for detecting the temperature of a controlled object and converting it into a voltage, an oscillation circuit for generating a sawtooth reference voltage, and a means for comparing the converted detected voltage and the reference voltage. A comparator for controlling the means for heating is provided.

[For production]

The comparator compares the detected voltage with the reference voltage to control the heating means. At this time, since the reference voltage has a sawtooth waveform,
The temperature gradually approaches the set temperature, and even after reaching the set temperature limit, the heating means is frequently turned on and off, thereby making it possible to reduce the overshoot phenomenon.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 is a diagram showing the circuit configuration, and is a diagram showing the circuit configuration of the conventional fifth
Portions corresponding to those in the figures are denoted by the same reference numerals and redundant detailed explanations will be omitted. In the figure, Ql is a transistor connected to a constant voltage power supply E via switch 1, 2 is a heater as a heating means, and 4 is air in tank 3 (controlled object).
Thermistor 5 serves as a conversion means for detecting the temperature of It is connected to the pace of transistor Q through resistor R1. Reference numeral 6 denotes an oscillation circuit that generates the aforementioned sawtooth waveform reference voltage, and its output terminal is connected to the non-inverting input terminal of the comparator 5.

Next, the operation will be explained.

When the switch 1 is turned on, a sawtooth reference voltage from the oscillation circuit 6 is applied to the non-inverting input terminal of the comparator 5. In addition, the resistance value of the thermistor 4 changes depending on the temperature of the air in the tank 3, and the inverting input terminal of the comparator 5 is connected to the tank 3.
Detection according to the temperature of the air inside! IE is given. The comparator 5 then controls the heater 2 by comparing the reference voltage and the detected voltage.

When switch 1 is turned on, the temperature of the air in tank 3 is lower than the set value, so the detection voltage at the inverting input terminal of regulator 5 is higher than the reference voltage at the non-inverting input terminal. Therefore, the output of the comparator 5 is "L". Therefore, the base current flows through the transistor Q, turning it on, and the heater 2 is energized.

When current flows through the heater 2 and the temperature of the air in the tank 3 increases, the resistance value of the thermistor 4 decreases, and the detected voltage at the inverting input terminal of the comparator 5 decreases. When this detection voltage becomes lower than the sawtooth reference voltage input to the non-inverting input terminal, the output of the comparator 5 becomes IH'', the transistor Q1 is turned off, and the power supply to the heater 2 is cut off. When the temperature of the air in the tank 3 becomes lower than the set value, the heater 2 is energized and the temperature of the air in the tank 3 rises again.

In this way, the heater 2 is repeatedly turned on and off,
The temperature of the air inside tank 3 is kept constant. At this time, the reference voltage from the oscillation circuit 6, which serves as the temperature set value, has a sawtooth waveform, so when raising the temperature of the air in the tank 3, the heater 2 is turned on while the off time is gradually increasing. , OFF is repeated.

As a result, the temperature of the air in the tank 3 gradually increases and approaches the set temperature. Further, even after the set temperature is reached, the heater 2 is frequently switched on and off to keep the temperature of the air in the tank 3 constant. FIG. 2 shows the relationship between the ON/OFF timing of the heater 2 and the voltage waveforms at both input terminals of the comparator 5. In FIG. In the figure, ←) is the detected voltage waveform of the inverting input terminal, and ←) is the reference voltage waveform of the non-inverting input terminal. As described above, when switch 1 is turned on at time t1, heater 2 is turned on and the detected voltage is reduced. Then, when the set temperature is reached at time t, the heater 2 is turned OFF'F, and is thereafter turned ON.

Repeat OFF. Here, since the reference voltage is in a sawtooth waveform, the heater 2 is repeatedly turned on and off while the off time becomes longer, and is turned on even after reaching the set temperature.
, OFF switching is performed frequently. Therefore, the overshoot is reduced, and as shown in FIG. 3, the temperature of the air in the tank 3 can be brought closer to the set value T.
Stable temperature control can be performed.

FIG. 4 is a circuit diagram showing a specific example of the oscillation circuit 6 that generates the above-mentioned sawtooth wave voltage. This circuit is designed to obtain a sawtooth output voltage by charging and discharging a capacitor C.A series circuit of a resistor 6.7 is connected in parallel with a power supply E, and a transistor Q (NPN) is connected in parallel with a resistor T. It is connected.

The connection point (PI) of resistor 6.7 is PNP) transistor Q
, this transistor Q.

The collector of is connected to the base of transistor Qt. Capacitor C is connected to a power supply E and a series circuit of resistors 8, 9 and 10, and the connection point of resistors 9 and 10 (Pg
) is connected to the emitter of transistor Q. Also, the connection point between resistors R3 and R9 is connected to the N
PN) is connected to the base of transistor Q4, and this transistor Q.

The emitter of is connected to the output terminal P via a resistor R11, and a resistor Rtt is connected in series with the resistor R11.

Note that the value of the resistor 7 is greater than the value of the resistor 10.

When the switch 1 is turned on, the transistor Q is turned on and the capacitor C is charged (because if the value of the resistor 7>the value of the resistor 10, the potential of P>pt). When the collector current of transistor Q3 flows, this collector current is the base current of transistor Q, so transistor Q! is turned on and collector current flows.

While the potential of P is higher than the potential of P, the operation is as described above, but when capacitor C is sufficiently charged and the potential of P2 becomes the same as the potential of P, transistor Q.

and Q are both turned off, and the charge stored in capacitor C is discharged. Then, when the capacitor C is discharged, the potential of P becomes higher than the potential of P again, so the transistors Q are turned on and the capacitor C is charged.

FIG. 5 is a diagram showing the voltage waveform (c) of Pl and the voltage waveform of P. In this way, since the capacitor C repeats charging and discharging, the voltage output from the transistor Q4 is ONI, and the voltage output from the resistor R11 and R1! It has a sawtooth wave shape divided by , and is input to the comparator 5 as a reference voltage.

Although one embodiment of the present invention has been described above, the present invention can be applied to other devices such as electric kotatsu, panel heaters, hair dryers, etc., which particularly control the temperature by setting it to a value higher than room temperature.

〔Effect of the invention〕

As explained above, according to the present invention, the sawtooth wave-like reference voltage is obtained by the oscillation circuit, so the overshoot of the heating means is reduced, and the heating means is frequently controlled even after the set temperature is reached. Therefore, there is an effect that stable temperature control is possible.

[Brief explanation of drawings]

Fig. 1 is a circuit configuration diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing the control timing of the heater shown in Fig. 1 and the voltage waveform of the large input terminal of the comparator, and Fig. 3 is a diagram showing the air in the tank. 4 is a circuit diagram showing a specific example of the oscillation circuit shown in FIG. 1. FIG. 5 is a diagram showing the voltage waveforms of Pi and P in FIG. 4. The figure is a circuit configuration diagram showing a conventional example, and FIG. 7 is a diagram showing the control timing of the heater shown in FIG. 6 and the temperature status of the air in the tank. 2・・・・・・・・・Heater
1゜4...Thermistor 5...Comparator 6...Oscillation circuit Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] a conversion means that detects the temperature of the controlled object and converts it into voltage;
A temperature control device comprising: an oscillation circuit that generates a sawtooth wave-like reference voltage; and a comparator that compares the voltage values of the converted voltage and the reference voltage to control a heating means for a controlled object. .