JP2690072B2 - Energization display device in temperature control circuit - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current-carrying display device in a temperature control circuit for heating equipment, electric heating equipment and the like. 2. Description of the Related Art Conventionally, in an energization display device in a temperature control circuit for controlling a heater to set a desired temperature, as shown in FIG. 4, there is only a display device 5 which is displayed at the same time when a power switch 3 is turned on. There were many things. Alternatively, as shown in FIG. 5, if the resistance value of the setting volume 18 is increased, the resistance is increased.
The voltage V _A divided by 16 and the resistor 17 and the setting volume 18
In comparison with the voltage V _B divided by the resistor 19 and the voltage V _A > V _B , the transistor 21 turns on and the LED2
2 lights up. In other words, temperature control is started from the setting position of the setting volume 18, LED22 lights up at the same time as the start,
There was an energization display circuit in which the LED 22 also lights up to the highest position of the setting volume 18. However, in such a configuration, it is difficult to know whether or not the temperature has reached the set temperature, and since it is not known whether or not this temperature is the set temperature, it is difficult to change the temperature to a desired temperature. Had the problem. Means for Solving the Problems The temperature control circuit of the present invention solves the above problems by
A switching element, a heater that is connected to the switching element in series and that heats a controlled object, a display device that displays an energization state to the heater that is connected in parallel with the heater, and a control circuit that controls ON / OFF of the switching element. Has and
The control circuit continuously connects the switching element when the difference voltage between the temperature detection signal of the controlled object and the temperature setting signal is large.
When it is turned on and the difference voltage is within the proportional control region, the ON time of the switching element in one cycle is decreased in proportion to the difference voltage, and the decrease time is increased by the decrease time. Is. Action The present invention has the above-mentioned configuration, and the ON / OFF state of the heater can be visually recognized by the display device connected in parallel to the heater, and when the temperature of the controlled object is extremely low with respect to the set temperature, Large difference voltage, continuous switching on
However, the heater is energized continuously, and the LED lights up and remains off. Then, when the temperature of the controlled object gradually rises and the difference from the set temperature becomes smaller, the difference voltage also becomes smaller, and when it enters the proportional control area, the switching element and the heater are turned off for a short period in a certain cycle. Then, when the differential voltage further decreases, the OFF ratio of the switching element and the heater increases, and when the set temperature is reached, it does not increase. On the other hand, the display device connected in parallel with the heater also turns on from the continuous lighting state at a fixed cycle, and the OFF rate increases during that fixed cycle and does not increase when the set temperature is reached. . Therefore, it can be seen visually that the temperature has reached the set temperature. Therefore, if the set temperature once set is not the desired temperature, the set temperature can be immediately changed again to obtain the desired temperature. Embodiment FIG. 1 is a circuit diagram showing an embodiment of the present invention. Reference numeral 31 is a power supply, and 32 is a power switch. 33 is a bidirectional power control element (switching element), and 34 is a heater.
36 is an LED (display device) for displaying electricity, 37 is a diode for protection against voltage of the LED 36 for displaying electricity, 38 is a current control resistor, and these are connected in parallel to the heater. 39 is a half-wave rectifier diode, 40 is a smoothing capacitor, 41 is a zero-cross pulse generation IC (control circuit), and the pulse output terminal 413 is used only when the inverting input terminal 411 has a higher potential than the non-inverting input terminal 412. Generates a negative zero-cross pulse. The thermistor 42 (temperature detection signal) for detecting the temperature of the hot water (controlled body) heated by the heater 34 has a low resistance value as the hot water temperature rises, and the potential Va rises. Further, the hot water temperature is set by the volume 43 (temperature setting signal), and when the volume 43 is rotated, the resistance value of the volume 43 decreases and the potential Vb rises. The operational amplifier 44 amplifies the potential difference (difference potential) between Va and Vb, and the output Vo (difference potential) is Vo = Vb + α (Va-Vb) when the resistor 45 and the resistor 46 are R46.
(Α = 1 + R46 / R45), and the non-inverting input terminal 412
Is input to On the other hand, reference numeral 47 denotes a triangular wave generating circuit (control circuit), which outputs a triangular wave from the output V481 of the operational amplifier 48 and inputs it to the zero cross pulse generating IC 41 and the inverting input terminal 411. FIG. 2 shows the potential relationship between the triangular wave V ₄₈₁ and the output Vo (V _{412 a to} V ₄₁₂ d) and the timing of zero cross pulse generation (heater ON). When the hot water temperature is lower than the set temperature, V2 in Fig. 2
Becomes the position shown in 12d, since at this time the heater 34 is V _481> V ₄₁₂ d, the pulse output terminal 413 of the zero-cross pulse generating IC 41, about synchronized with the zero crossing of the source voltage 1
A negative zero-cross pulse having a voltage of about 8 V is generated with a width of 00 μsec and is input to the gate 331 of the bidirectional power control element 33, the bidirectional power control element 33 is turned on, and the heater 34 is turned on. It is continuously energized. Then, when the hot water temperature rises, the resistance value of the thermistor 42 decreases, the potential of Va rises, and the output Vo becomes V _{412 in} FIG.
Move to proportional control area as shown by b or V ₄₁₂ c.
As shown in FIG. 2, the heater 34 is energized only when V ₄₈₁ > V ₄₁₂ b, V ₄₁₂ c. Therefore, the heater 34
The energization display LED 36 connected in parallel with the
ON only when the heater 34 is energized in the cycle of ₄₈₁ (about 1 second)
I do. That is, when the differential voltage is in the proportional control region, duty control for controlling the energization rate to the heater 34 is performed in a constant cycle in proportion to the differential voltage. When the hot water temperature is much higher than the set temperature, Vo becomes V ₄₁₂ a in Fig. 2 and V
₄₈₁ <V ₄₁₂ a, and the heater 34 remains off. FIG. 3 is an external view of an electric shower in one embodiment. 49 is a power supply display LED, and 43 is a temperature setting volume. 50 is a water valve, 51 is a temperature setting display, and 52 is a head. 36 is the energizing LED. In the above configuration, when the hot water temperature is lower than the set temperature, the energization LED 36 remains lit, and when the hot water temperature gradually approaches the set temperature, the energization display LED 36 is intermittent during the cycle of the triangular wave V _481. The ON-OFF ratio will not change when it reaches almost the set temperature.
The user knows that the set temperature has been reached. Then, when the set temperature is still low or conversely high, the setting can be changed to immediately change the hot water temperature to a desired one. Further, when the set temperature is raised, the set temperature may not be reached even if the capacity of the heater 34 is maximized. In this case, the energization display LED 36 is still lit and the capacity of the heater 34 is not changed. This is a limit and has the effect of informing the user that the temperature will not rise any further. EFFECTS OF THE INVENTION As described above, the difference voltage between the voltage from the temperature detection circuit of the controlled object and the voltage from the temperature setting circuit is obtained, and when the difference voltage is large, the switching element is continuously connected.
When the differential voltage is turned on and the differential voltage is in the proportional control region, the ON time of the switching element in a constant cycle is decreased in proportion to the differential voltage, and the OFF time is increased by the decrease. Then, connect a heater in series with the switching element,
Since the configuration is such that the energization display element is connected in parallel with the heater, the transition state to the set temperature can be seen at a glance.Furthermore, when the set temperature is reached, the blinking rate of the energization display element changes, and it remains constant. Now that you know it, you can understand it intuitively. Therefore, if the temperature once set is still insufficient, the temperature can be changed immediately and the desired temperature can be set again.
In addition, when the heat capacity of the controlled object is large and the desired temperature is not reached even when the heater is fully energized, the energization display element remains lit, and it can be seen that the temperature does not rise any further, which makes it very easy to use. effective.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall circuit diagram of an embodiment of the present invention, FIG. 2 is a timing chart of temperature control, and FIG. 3 is an external view of a main body of the embodiment, FIGS. The figure shows a conventional circuit diagram. 33 ... Bidirectional power control element (switching element), 34
...... Heater, 36 ...... LED for current display (display device), 41 ...
… Zero cross pulse generation IC (control circuit), 42… Thermistor (temperature detection signal), 43… Temperature setting volume (temperature setting signal), 47… Triangular wave generation circuit (control circuit).

Claims (1)

(57) [Claims] A switching element, a heater connected in series with the switching element to heat a controlled object, a display device for displaying an energization state to the heater connected in parallel with the heater, and a control for ON-OFF controlling the switching element And a control circuit, wherein the control circuit continuously turns on the switching element when the difference voltage between the temperature detection signal of the controlled object and the temperature setting signal is large, and the difference voltage is proportionally controlled. An energization display device in a temperature control circuit configured to decrease the ON time of the switching element in one cycle in proportion to the difference voltage and increase the OFF time by the decrease within the range.