JPH0230046B2 - KANETSUKIKINOSEIGYOKAIRO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a control circuit for a heating device that cuts off electricity to a heater after a predetermined period of time by utilizing the capacitor charging time of a CR integration circuit consisting of a capacitor and a resistor connected to an AC power source. . Prior Art Figure 1 shows a conventional example of a control circuit for heating equipment using a CR integral circuit. In FIG. 1, reference numeral 1 denotes an AC power source, to which a heater 14 is connected via a power switch 2. In FIG. The CR integration circuit 3 connected in parallel with this heater 14 is
It consists of a series circuit of a diode 4, a resistor 5, and a capacitor 6, and the switch 2 is closed (the switch 2 is kept closed by a latch mechanism, etc.)
Then, the capacitor 6 is charged with the power supply voltage and with half waves. Further, a reference voltage circuit 7 is connected in parallel with the heater 14, and includes a diode 20 and a resistor 2.
1 and a capacitor 8 to convert the AC power supply 1 into a DC power supply, and a constant voltage diode 9 connected to both ends of the capacitor 8 makes the current constant. The voltage of the constant voltage diode 9 is divided by resistors 10 and 11 to generate a reference voltage. This resistance 1
This is a comparator that compares the reference voltage at the connection point of 0 and 11 with the voltage of the capacitor 6 of the CR integration circuit 3.
Equipped with PUT12. The cathode terminal 13 of this PUT 12 is outputted to the gate of a thyristor 16 that controls the energization of the solenoid 15. The solenoid 15 operates to open the switch 2. In this configuration, when the switch 2 is closed, the voltage of the capacitor 6 of the CR integration circuit 3 gradually increases, and when it reaches the reference voltage, as described above.
PUT 12 is turned on, discharges the charge stored in capacitor 6, and a pulse output is obtained at cathode terminal 13. This output turns on the thyristor 16 and current flows through the solenoid 15, which opens the switch 2. That is, the time for energizing the heater 14 is controlled by the time for charging the capacitor 6. In this conventional example, the reference voltage is regulated by the voltage regulator diode 9, so as the power supply voltage increases, the charging speed of the capacitor 6 becomes faster, and the time it takes for the voltage of the capacitor 6 to reach the reference voltage becomes faster. , Therefore, the time it takes for PUT 12 to turn on becomes shorter. Conversely, when the power supply voltage decreases, the time it takes for the PUT 12 to turn on becomes longer. The rate of these changes is calculated by directly adding the fluctuation of the power supply voltage to the CR integration circuit 3, so the relationship between the fluctuation rate of the power supply voltage and the fluctuation rate of the time period is the second one.
As shown in the figure, there is a nearly inversely proportional relationship. Second
In the figure, a conventional circuit was prototyped in a laboratory, and the experimental results are shown by solid lines. According to the experimental results, when the power supply voltage is changed by -15% from 100V, the time from turning on switch 2 to stopping energization of heater 14 is +18.7%, and when the power supply voltage is changed by +15%, Its time period changes by -15.2%. Problems to be Solved by the Invention However, when this conventional example is applied to a heating device such as a toaster oven, the finish of the cooked food becomes
Since it is determined by the total amount of heat given to the food, it is inversely proportional to the power supply voltage, so even if you change the time limit for energizing the heater 14, it cannot be compensated sufficiently. There was a problem in that the browning color varied considerably due to fluctuations in the power supply voltage. That is, at an input W ₀ at a power supply voltage of 100V,
Assuming that it is possible to bake bread to a predetermined brown color by applying electricity to the heater 14 for t ₀ seconds, the total amount of heat at that time is W ₀ t ₀ =V ² ₀ t ₀ /R (R is the resistance value of the heater 14 ) becomes. This total amount of heat W ₀ t ₀ is determined by the power supply voltage V
If you want to obtain the obtained result even if it fluctuates, calculate the fluctuation rate of the energization time t to the heater 14 at that time, and you will get V ² ₀ t ₀ /R=V ² t/R ∴t/t ₀ =V ² ₀ /V ² =(1/V/V ₀ ) ² , and the calculation results are shown in the table below.

[Table] If this is illustrated, it will look like the dotted line in Figure 2. Therefore, in order to perform total heat correction,
Heater 1 is approximately twice as high as the power supply voltage fluctuation rate.
It is necessary to provide a change rate over the time of energization to 4, and there was a problem that the conventional inverse proportional correction using a simple CR integration circuit 3 could not sufficiently keep the browning of the bread constant. SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to make it possible to largely correct the heater energization time due to fluctuations in power supply voltage, and to perform optimal heater energization control in a heating device. Means for Solving the Problems In order to achieve the above object, the present invention includes a heater 14 connected to an AC power source via a switch 2;
Constant voltage element 1 connected in parallel to this heater 14
8, a series circuit of a CR integrating circuit 3 consisting of a resistor 5, a diode 4, and a capacitor, and a comparator 12 for comparing the charging voltage of the capacitor 6 in the CR integrating circuit 3 with the reference voltage of the reference voltage circuit 7, The constant voltage element 18 prevents voltage application to the CR integrating circuit 3 when the AC power supply voltage is below a certain voltage, and when the constant voltage is reached, applies a voltage obtained by subtracting the constant voltage from the AC power supply voltage to the CR integrating circuit 3. The comparator 12 is configured to change the switch 2 from the closed state to the open state and control the energization time of the heater 14 when the charging voltage of the capacitor 6 in the CR integration circuit 3 becomes equal to or higher than the reference voltage. . Effects According to the above configuration, when a fluctuation occurs in the AC power supply voltage and, for example, the voltage decreases, the constant voltage element 18 applies a voltage obtained by subtracting a constant voltage from the AC power supply voltage to the CR integrating circuit 3. The charging speed of the capacitor 6 of the CR integration circuit 3 is determined by the constant voltage element 18.
This makes it possible to reduce the amount of electricity compared to the case where the heater is not provided, and to extend the energization time of the heater. In addition, constant voltage element 18
prevents the voltage application to the CR integration circuit 3 until a constant voltage is reached, so the voltage application time to the CR integration circuit 3 is also shorter than when the constant voltage element 18 is not provided, and therefore the capacitor of the CR integration circuit 3 The charging speed is further reduced, and the energization time of the heater can be significantly extended. Examples The present invention solves the above problems, and the following:
An embodiment of the present invention will be described based on FIGS. 3 to 5. FIG. 3 shows a control circuit for a toaster oven. In the figure, parts that are the same as those in FIG. 1 are given the same numbers, and detailed explanations will be omitted. Third
In the figure, 18 is a constant voltage diode which is a constant voltage element, and 19 and 22 are respective resistors. The constant voltage diode 18 prevents voltage application to the CR integration circuit 3 when the AC power supply voltage is below a certain voltage,
When the constant voltage is reached, a voltage obtained by subtracting the constant voltage from the AC power supply voltage is applied to the CR integration circuit 3. Note that the voltage changing means may be other than a constant voltage diode, and may be any circuit as long as it can perform the above operation. Further, the collector of the transistor 17 is connected to the constant voltage diode 9 in the reference voltage circuit 7.
The base of this transistor 17 is connected to a resistor 11 that generates a reference voltage. In the above configuration, when the power switch 2 is closed (once closed, it is maintained in the closed state by a latch mechanism, etc.), the CR integration circuit 3 and the reference voltage circuit 7 are connected to the half-wave circuit shown in FIG. 4 by the diodes 4 and 20. will be input. However, since the voltage regulator diode 18 is connected in front of these circuits 3 and 7, when the voltage of the AC power source 1 is lower than the Zener voltage Vz, it does not flow into the circuits 3 and 7. The voltage at the anode terminal (the voltage across the series connection of resistors 19 and 20) is zero. Then, as the voltage of the AC power supply 1 gradually increases as shown in FIG. 4 and becomes equal to or higher than Vz, the voltage regulator diode 18 becomes conductive.
As shown in FIG. 5, a voltage obtained by subtracting the Zener voltage Vz of the voltage regulator diode 18 from the power supply voltage is applied to the circuits 3 and 7. That is, when the voltage of the AC power supply 1 becomes equal to or higher than the Zener voltage Vz, the voltage regulator diode 18 becomes conductive. However, in this conductive state, the Zener voltage Vz is always generated in the voltage regulator diode 18, so that the circuit 3, 7, in a region where the voltage of the AC power supply 1 is higher than the Zener voltage Vz, this Zener voltage Vz
A voltage dropped by that amount is applied, resulting in a waveform shown in FIG. Next, when the voltage shown in FIG. 5 is applied to the reference voltage circuit 7, current flows through the resistors 10 and 11, and the transistor 17 is turned on. Therefore, the current flowing through the constant voltage diode 9 flows to the transistor 17 side and does not flow to the gate of the thyristor 16, so that the thyristor 16 remains off. The voltage regulator diode 9 connects the thyristor 1 immediately after the power switch 2 is turned on.
It functions to prevent erroneous ignition of capacitor 6 and to maintain a constant voltage across both ends of capacitor 8. On the other hand, the voltage shown in FIG. 5 is also applied to the CR integration circuit 3, and current flows to charge the capacitor 6.
Then, charging of capacitor 6 progresses and PUT1
2, the anode voltage A is the gate voltage (reference voltage) G
When it goes higher, PUT12 turns on. At this time, the gate G and cathode K of PUT12 are in a shorted state, so the current that had previously flowed into the base of transistor 17 via resistor 11 is now
It is bypassed by PUT 12, so transistor 17 is turned off. Then, the current that had been flowing from the constant voltage diode 9 to the transistor 17 flows into the gate of the thyristor 16, turning the thyristor 16 on. Then, solenoid 15
A current flows through the switch, operating the plunger, releasing the mechanical hold on the power switch 2, and opening the switch. Then, the power supply to the heater 14 is stopped. Note that a constant voltage diode 18 that cuts off the power supply voltage
By appropriately selecting the voltage, fluctuations in the power supply voltage can be amplified and applied to the CR integration circuit 3. As a result, the rate of change in the energization time to the heater 14 with respect to the rate of change in the power supply voltage can be arbitrarily set without changing the time constant of the CR integration circuit 3. Next, the relationship between the power supply voltage and the charging time of the CR integration circuit 3 will be explained with reference to FIG. The voltage applied via the constant voltage diode 18 varies depending on the half-wave voltage (half-wave voltage of the AC power supply voltage) shown in FIG. That is, when a high voltage such as A in FIG. 4 is applied, the voltage A in FIG. 5 is applied to the CR integration circuit 3, and when a normal voltage such as B in FIG. When the voltage B in FIG. 5 is applied to the CR integration circuit 3, and the low voltage C in FIG. 4 is further applied, the voltage C in FIG. 5 is applied to the CR integration circuit 3. The voltages of A, B, and C in Figure 5 are A>B>C
As is clear from the relationship, the charging speed of the capacitors of the CR integrating circuit 3 is faster in the order of A, B, and C. Further, the time for applying voltage to the CR integrating circuit 3 has the relationship t _A > t _B > t _C , and the higher the voltage, the longer the voltage application time and the faster the capacitor charging speed of the CR integrating circuit 3 becomes. Yotsute CR
In each case of A, B, and C, due to the synergistic effect of the magnitude of the voltage applied to the integrating circuit 3 and the duration of the applied voltage,
The charging speed to the CR integration circuit 3 can be changed greatly. FIG. 6 shows data obtained by measuring an embodiment of the present invention in a laboratory, in which the voltage of the constant voltage diode 18 was variously changed, and the relationship between the power supply voltage and the time limit (the time period during which the heater 14 was energized) was measured. It is something. It can be seen that the rate of change can be increased by increasing the voltage of the constant voltage diode 18 in the order of the broken line, the two-dot chain line, and the one-dot chain line in the figure. Note that the solid line in the figure shows the case where the conventional constant voltage diode 18 is not used. As mentioned above, when correcting the total heat amount of the heater 14 due to fluctuations in the power supply voltage, it is appropriate to have a rate of change as shown in the dotted line in Figure 2, and as a result of experiments, we have found that The voltage of the constant voltage diode 18 for obtaining the rate of change was 43V. Even with this constant, as a result of bread roasting experiments,
Good results were obtained in that the baked color hardly changed despite variations in the power supply voltage. Regarding the roasting of bread, since there is heat dissipation from the oven and transmission loss to the bread, it seems better to set the rate of change somewhat larger than the calculated rate of change. Effects of the Invention As is clear from the above embodiments, according to the present invention, since the CR integrating circuit is connected to the AC power supply via the voltage changing means, both the applied voltage and the applied voltage time of the CR integrating circuit can be changed. It can be changed in response to AC power supply voltage fluctuations, and the charging speed of the CR integration circuit can be changed significantly in response to AC power supply voltage fluctuations, making it possible to correct the energization time to the heater to be optimal for the heating equipment. .

[Brief explanation of drawings]

Figure 1 is a conventional CR timer circuit diagram, Figure 2 is a characteristic diagram showing the relationship between the power supply voltage and time limit in the conventional example, and the calculated value of the relationship between the power supply voltage and time limit required when performing total heat correction. The figure is a circuit diagram showing one embodiment of the present invention, Figures 4 and 5 are voltage waveform diagrams for explaining the circuit operations of the conventional and present invention, and Figure 6 is the power supply voltage of the CR timer circuit according to the present invention. FIG. 3 is an actually measured characteristic diagram showing the relationship between the time limit and the time limit. 1... AC power supply, 2... Power switch, 3...
CR integration circuit, 7...Reference voltage circuit, 12...
PUT, 18... Constant voltage diode.

Claims (1)

[Claims] 1 A series circuit of a heater 14 connected to an AC power source via a switch 2, a constant voltage element 18, a resistor 5, a diode 4, and a capacitor 6, which are connected in parallel to the heater 14, and a CR integrating circuit 3.
Charging capacitor 6 in this CR integration circuit 3
and a comparator 12 for comparing the charging voltage of the reference voltage circuit 7 with the reference voltage of the reference voltage circuit 7.
The voltage application to the integrator circuit 3 is blocked, and when a certain voltage is reached, a voltage obtained by subtracting a certain voltage from the AC power supply voltage is applied to the CR integrator circuit 3. A control circuit for a heating device that changes the switch 2 from a closed state to an open state when the charging voltage of the heater 14 becomes equal to or higher than a reference voltage, and controls the energization time of the heater 14.