JPH0353297Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial technical field) The invention relates to a temperature control device.
Specifically, an electric blanket or the like includes a heating element, a heat-sensitive element in which a heat-sensitive layer having a negative impedance temperature characteristic is interposed between two conductors, and a control rectifying element that controls energization to the heating element. This invention relates to a temperature control device for use in electric carpets.

(Prior art) Conventionally, as the heat-sensitive layer of the heat-sensitive body of such a temperature control device, an organic semiconductor made by adding an antistatic agent to vinyl chloride has been used so that the temperature coefficient of impedance is negative. . However, when a voltage containing a DC component is applied to this heat-sensitive layer, impedance changes over time due to the polarization effect of the dielectric, so the circuit is configured to apply an AC voltage with equal positive and negative energy to the heat-sensitive layer. There must be. In addition, if the circuit breaks down for some reason, an overheat prevention circuit is installed to prevent fire or burnout. The circuit must be constructed in a fail-safe manner to immediately stop energizing the heating element.

Therefore, the conventional method is to connect a series circuit consisting of a temperature setting resistor, a conductor of a heat sensitive body, and a heater for heating a temperature fuse to an AC power supply, and connect a bidirectional pulse generating element and a pulse transformer between the conductors of the heat sensitive body. A common phase control method is to connect a series circuit consisting of a primary winding and control the conduction angle of the thyristor using bidirectional pulses appearing in the secondary winding of the pulse transformer. This is fail-safe against disconnection by connecting each circuit component in series to form a pulse generating circuit. Furthermore, a neon discharge tube having bidirectional symmetrical characteristics is used as the pulse generating element, so that no direct current voltage is applied to the heat sensitive layer.

(The problem that the invention aims to solve) However, this has the following drawbacks. First, pulses in both positive and negative directions are generated on the secondary side of the pulse transformer and applied between the gate and cathode of the thyristor, so if a positive pulse of sufficient voltage is applied to the gate to trigger the thyristor, If the voltage of the negative pulse exceeds the reverse breakdown voltage between the gate and card of the thyristor, and if the voltage of the negative pulse falls below this reverse breakdown voltage, the voltage of the positive pulse will be insufficient. Therefore, a thyristor with a small gate trigger current must be selected and used. Second, since the lighting start voltage and pulse generation voltage of neon discharge tubes vary widely, neon discharge tubes also require selection. Thirdly, since it uses phase control, it takes time for the temperature to rise, causing problems such as radio wave interference.

The present invention was developed in view of the above-mentioned circumstances, and its purpose is to operate in a fail-safe manner against equipment failures, prevent aging of the heat sensitive element, and provide a sufficiently large gate trigger current to the control rectifier. In addition, the capacitor in the circuit has a small capacitance, making it easy to integrate the circuit, and has low temperature ripple and excellent constant temperature characteristics. To provide temperature control equipment.

[Structure of the invention] (Means for solving the problem) The temperature control device of the invention includes a heating element and a control rectifier connected in series between AC power supply terminals, and a control rectifying element configured to receive heat from the heating element. A voltage dividing resistor and the heat sensitive body are connected in series between the provided heat sensitive body having negative impedance temperature characteristics and the AC power supply terminal, and the voltage between the AC power supply terminals is adjusted according to the temperature of the heat sensitive body. A temperature detection circuit that outputs a divided AC voltage, a phase advance circuit that advances the phase of the AC voltage of this temperature detection circuit to obtain a phase advance detection voltage, and a gate trigger current that is supplied to the gate of the control rectifier. is provided between the ignition circuit and the AC power supply terminals so as to have opposite polarities to each other, and is in a conductive state during a period in which a predetermined breakover voltage is exceeded during one half-wave period and the other half-wave period of the AC power supply voltage. two constant voltage diodes which become non-conductive in a period below the breakover voltage and output a changing voltage near the zero cross point of the AC power supply voltage, and are connected in parallel to these constant voltage diodes via diodes. a constant voltage circuit which is equipped with a smoothing capacitor and outputs a constant voltage substantially equal to the breakover voltage over the full wave period of the AC power supply voltage, and the output voltage of the constant voltage circuit is divided and is used as a reference A voltage dividing circuit for setting a voltage, a rectified output voltage obtained by full-wave rectification of the output voltage of the voltage regulator diode, and an output voltage of the voltage dividing circuit are provided to perform a switching operation, and the alternating current power supply voltage a switching circuit that outputs the reference setting voltage to the reference setting voltage output point near the zero crossing point of the switching circuit, and outputs an output voltage substantially equal to the output voltage of the constant voltage circuit to the reference setting voltage output point during other periods; , a comparison circuit that compares the reference voltage output to the reference setting voltage output point and the phase advance detection voltage and outputs a signal for activating the ignition circuit when the latter is larger than the former. It is characterized by its structure.

(Function) According to the temperature control device of the present invention, the switching circuit performs switching operation by being supplied with the rectified output voltage obtained by full-wave rectification of the output voltage of the two voltage regulator diodes and the output voltage of the voltage dividing circuit. Then, in the vicinity of the zero-crossing point of the AC power supply voltage, the reference setting voltage is output to the reference setting voltage output point, and during other periods, an output voltage approximately equal to the output voltage of the constant voltage circuit is output to the reference setting voltage output point. output,
The comparison circuit compares the reference voltage outputted to the reference setting voltage output point and the phase advance detection voltage of the phase advance circuit, and outputs a signal for operating the ignition circuit when the latter is greater than the former. Therefore, the controlled rectifier is turned on near the zero voltage of the AC power source.

(Example) An example of the present invention will be described below with reference to the drawings. Reference numeral 1 denotes an electric blanket main body, in which a heat-sensing heating element 2 and a heat-sensitive element 3 are arranged. That is, FIG. 2 is a diagram showing a heat-sensing heating element 2, in which a heating wire 2b serving as a heating element is wound around a core yarn 2a.
A nylon layer 2c melts at a predetermined temperature from above.
A heating sensing wire 2d is further wound around the wire and an electrically insulating coating 2e is applied to the outside thereof. Further, FIG. 3 is a diagram showing the heat sensitive body 3, and the core thread 3a
One conductor 3b is wound around the conductor 3b, a heat-sensitive layer 3c having an impedance characteristic of a negative temperature coefficient is provided on top of the heat-sensitive layer 3c, and the other conductor 3d is further wound on top of the heat-sensitive layer 3c, and an electrically insulating coating 3e is applied to the outside thereof. . This heat-sensitive layer 3c is made of an organic semiconductor made by adding an antistatic agent to vinyl chloride, and the conductors 3b, 3
The equivalent circuit when an AC voltage is applied between d and
As shown in the figure, when represented by a parallel circuit of a resistor R and a capacitor C, the respective impedances r and Xc exhibit temperature characteristics as shown in FIG. It will be shown as follows. On the other hand, 4 and 5 are a pair of AC power terminals,
A series circuit including a switch 6, a heating wire 2b, a thyristor 7 as a control rectifying element, and a temperature fuse 8 is connected between these. 9 is a fixed resistor, 10 is a variable resistor for temperature setting, and these are connected between AC power supply terminals 4 and 5 via a heater 11 that heats the impedance of the heat sensitive layer 3c of the heat sensitive body 3, the sensing wire 2d, and the temperature fuse 8. The fixed resistor 9 and the variable resistor 10 constitute a voltage dividing resistor, and a voltage is connected between the AC power terminals 4 and 5 at one end of the conductor 3b depending on the temperature of the electric blanket body 1. It is designed to output a temperature detection voltage V _S1 which is an AC voltage obtained by dividing the voltage of . Due to the action of the capacitor C shown in the equivalent circuit of the heat sensitive layer 3c, this temperature detection voltage V _S1 is slightly delayed in phase from the voltage V _AC between the AC power supply terminals 4 and 5, as shown in FIG. 6a. . 13 is a capacitor 14,
In a phase advancing circuit consisting of a resistor 15 and a diode 16, assuming that there is no diode 16, the output terminal
As shown in FIG. 6b, an alternating current is whose phase is advanced compared to the temperature detection voltage V _S1 flows, but in reality, the negative current bypasses the resistor 15 by the diode 16, so the output A phase advance detection voltage _VSO having a half-wave sinusoidal waveform as shown in FIG. 6d is output from the terminal When the impedance of the heat sensitive layer 3c is high, the phase advance detection voltage is V _SO2 in the same figure.
Conversely, when the impedance of the heat-sensitive layer 3c is low, the phase advance detection voltage changes in the direction shown by _VSO1 in the figure. Furthermore, the relationship between the impedance of the heat sensitive layer 3c and the phase advance detection voltage _VSO is changed by setting the variable resistor 10. Reference numeral 17 denotes a comparison control circuit, which includes a reference voltage generator 18 and operational amplifiers 38 and 39 corresponding to a comparison circuit, and controls a transistor 59 using the output of the operational amplifier 39 to cause a gate current to flow through the thyristor 7. It is. In particular, the reference voltage generating section 18 has the following configuration. That is, a resistor 29 and Zener diodes 19 and 20 with opposite polarities, which are constant voltage diodes, are connected in series between the AC power supply terminals 4 and 5.
At the common connection point with The AC power source is in a conductive state during the period in which the side is positive (hereinafter referred to as the "negative half cycle") exceeding a predetermined breakover voltage, and in a non-conductive state in the period below the breakover voltage. A changing voltage is output near the voltage zero-crossing point (zero voltage point) (Figure 6 bV _Z
reference). In addition, these Zener diodes 19,
A smoothing capacitor 37 is connected to the comparison control circuit 17 via a diode 25 between both ends of the series circuit 20.
A constant voltage circuit 63 is configured to output a constant voltage approximately equal to the breakover voltage to the common connection point between the diode 25 and the smoothing capacitor 37 over the full wave period of the AC power supply voltage. (See Figure 6 bV _Z1 ). The output voltage of this constant voltage circuit 63 is divided by a voltage dividing circuit 64 consisting of resistors 33 and 34, and this voltage is divided by both resistors 33 and 34.
The reference setting voltage is applied to the output terminal Y as the reference setting voltage output point, which is the common connection point of 4 (see Figure 6 dV _Z2 ).
is output as On the other hand, the transistors 35, 36 and diodes 21 to 24, 2 shown in FIG.
6 to 28 and resistors 33 to 32 constitute a switching circuit 65, and as will be made clear from the explanation of the operation described later, the rectified output voltage obtained by full-wave rectification of the outputs of the Zener diodes 19 and 20 and the constant voltage circuit 6
As a result, the potential of the output terminal _Y , which is the reference setting voltage output point, is changed between one half-wave period (positive half cycle) and the other half-wave period (positive half cycle). In the vicinity of the zero-crossing point of the period (negative half cycle), it is made equal to the reference setting voltage V _Z2 , and in the remaining period, it is made substantially equal to the output voltage V _Z1 of the constant voltage circuit 63. Note that the resistance value of the resistor 32 is set to be sufficiently smaller than that of the resistor 33. Note that 40 to 48 are resistors, 49 and 50 are diodes, and 51 is a transistor. 52 is a firing circuit, 53 is a resistor, 5
4 is a capacitor, 55 is a diode, 56 is a Zener diode, 57 is a resistor, and 58 is a capacitor. Further, 59 is a transistor as a switching element, 60 is a diode, and 6
1 is a heater that heats the temperature fuse 8;

Next, the operation of the above configuration will be described. When the switch 6 is turned on, the phase advance detection voltage _VSO is inputted to the inverting input terminal of the operational amplifier 38 via the resistor 40, and the reference voltage Vr from the output terminal Y of the reference voltage generation section 18 is inputted to the non-inverting input terminal. is input. Therefore, the voltage Vz at the common connection point of the Zener diode 19 and the diode 25 is
Due to the breakover effect of 0, the diode 25 and capacitor 37 change as shown in FIG.
At the common connection point of
V _Z1 is output, and a voltage V _Z ' as shown in FIG. 6c is input to the base of transistor 35.
That is, the transistor 35 is turned off for a short time each time near zero voltage of the AC power supply V _AC , and the transistor 3
Conversely, it turns on for a short time each time near the zero voltage of the AC power supply V _AC . When the transistor 36 is on, the collector voltage of the transistor 36 becomes approximately equal to the emitter voltage, so the diode ₂₈ is reverse biased and is in a cut-off state. The voltage V _Z2 divided by 33 and 34 is output, and when the transistor 36 is off, the resistor 32 with a sufficiently small resistance value is connected in parallel to the resistor 33 as described above, so the output terminal Y In short, a voltage V _Z1 ' approximately equal to the voltage V _Z1 is generated, and in short, the reference voltage Vr generated at the output terminal Y is at the low voltage portion of the voltage V _Z2 near the zero voltage of the power supply voltage V _AC , as shown in Fig. 6d. It becomes a waveform having 62.

Therefore, the state when the temperature of the electric blanket main body 1 is low immediately after the switch 6 is turned on is expressed from time t ₁ to
In _this state, the impedance of the heat-sensitive layer 3c is high, so the _phase advance detection voltage V _SO shown _{in FIG} . The low voltage section 62 is the phase advance detection voltage.
The voltage V _O1 at the output terminal of the operational amplifier 38 becomes lower than V _SO at times t ₁ and t ₃ as shown in FIG. 6e.
It becomes "low" when corresponding to the low voltage part 62 of
A voltage V _C shown in FIG. 6f is input to the inverting input terminal of the operational amplifier 39. A voltage V _R obtained by dividing the positive half cycle of the voltage V _Z by resistors 43 and 44 is applied to the non-inverting input terminal of the operational amplifier 39, and therefore, between times t ₁ and _{t 2} . t ₃ ~
During _t4 , since voltage V _R >voltage V _C , the voltage V _O2 at the output terminal of the operational amplifier 39 becomes "high" as shown in FIG. 6g. On the other hand, the current ic flowing through the capacitor 54 is
It is about 90 degrees ahead of V _AC and reaches its maximum value at each time t ₁ to t ₆ . Also,
Since the transistor 59 is conductive when the voltage V _O2 at the output terminal of the operational amplifier 39 is "high", the gate of the thyristor 7 has a voltage at time t ₁ as shown in FIG. 6i.
A gate trigger current i _G with a maximum value of t ₃ and t 3 is applied, and therefore, the thyristor 7 is ignited at zero voltage of the AC power supply V _AC and conducts, causing a positive sine half-wave current to flow through the heating wire 2b. As a result, when the temperature of the electric blanket body 1 rises, the impedance of the heat-sensitive layer _3c decreases, and as shown in _FIG . It becomes lower than the voltage section 62, and no "low" portion is generated at the output terminal of the operational amplifier 38, as shown at times _t5 to _t6 in FIG. 6e. Therefore, at time _t5 , the inverting input terminal of the operational amplifier 39 has a signal f in FIG.
Since the “high” level voltage V _C as shown by the broken line continues to be input to , and the voltage V _O2 at the output terminal of the operational amplifier 39 is at the “low” level, the voltage V _Z is applied to the non-inverting input terminal of the operational amplifier 39. resistor 43,
A voltage V _R divided by voltages 44 and 45 as shown by the solid line in FIG. 6f is applied between times t ₅ and _{t 6} . That is, the voltage V ₀₂ at the output terminal of the operational amplifier 39 is
As shown in Figure g, the state continues to be "low" from time t ₅ to _{t 6} .
Since the level state remains and the transistor 59 continues to be maintained in a non-conducting state, the thyristor 7
becomes non-conductive, current is no longer supplied to the heating wire 2b, and the temperature of the electric blanket body 1 stops rising. Then, temperature control is performed by repeating the above operations. In this case, the temperature of the electric blanket main body 1 can be set to an appropriate temperature by changing the resistance value of the variable resistor 10 and adjusting the value of the phase advance detection voltage V _SO with respect to a specific temperature.

In addition, due to some kind of circuit failure, the nylon layer 2
If the temperature of the wire c rises abnormally, it melts and the heating wire 2b is short-circuited to the sensing wire 2d, causing the heater 11
Since a larger current than usual flows through the heater 11
Temperature fuse 8 is blown by the heat generated by , and at the same time, an alternating current having the same phase as AC power supply voltage V _AC is applied to the base of transistor 51 , and transistor 51 is turned on during the positive half cycle of AC power supply V _AC to cut off transistor 59 . Therefore, even if the operational amplifier 39 generates an output current, the thyristor 7 will be prevented from firing and the current to the heating wire 2b will be cut off. When the current leakage increases, the diode 60
Current begins to flow to the heater 61 via
The temperature fuse 8 is blown by the heat generated by the heater 61.

By the way, the gate trigger current I _G of thyristor 7
If the time duration is not greater than a predetermined value, the voltage (V _AK ) between the anode and cathode of the thyristor 7 will be small and the anode current will not reach the latch current, so the thyristor 7 may not turn on. Further, if the thyristor 7 is turned on later than near zero voltage of the AC power supply V _AC and the thyristor 7 is fired after the anode voltage of the thyristor 7 becomes high, radio wave interference may occur. however,
In the above configuration, the reference voltage Vr having the low voltage part 62 near the zero voltage of the AC power supply V _AC and the phase advance detection voltage V _SO
Compare the output of the operational amplifier 3 with the comparison output.
8 and 39, and the transistor 59 is made conductive during the positive half cycle period from the zero voltage of the AC power supply V _AC , so the thyristor 7 receives the zero voltage of the AC power supply V _AC . Gate trigger current I _G with a sufficiently long duration as a starting point
, and the thyristor 7 can be reliably turned on when the anode voltage is OV.

The temperature is set using variable resistor 10, but this can be changed to a fixed resistor and resistor 3 is used instead.
3 or 34 may be used as a variable resistor to vertically change the low voltage portion 62 of the reference voltage Vr to set the temperature.

According to the above configuration, the following effects can be obtained. That is, since a sufficiently large gate trigger current can be passed through the gate of the thyristor 7, variations in the gate trigger sensitivity of the thyristor 7 can be absorbed and there is no need for selection, and the reference voltage Vr and the voltage V _Z2 of the low voltage section are Zena diode 19,20
Since the stabilized voltage is obtained by dividing the voltage, it has excellent voltage stability.Moreover, since no direct current is applied to the heat-sensitive layer 3c, it does not change over time, so the temperature can be set accurately. Since the thyristor 7 is continuously energized until it reaches the temperature,
Since the temperature of the electric blanket body 1 rises quickly and the ignition of the thyristor 7 is turned on and off at the zero cross at OV of the AC power supply voltage, there is no risk of radio wave interference. Furthermore, since the detection voltage is not smoothed using a capacitor or the like to convert it to DC, the comparison control circuit 17 can be easily integrated into an integrated circuit, and the operational amplifier 3
Since the input impedance of 8 is high, the heat sensitive layer 3c
Capacitor 1 that prevents direct current from flowing to
The capacity of 4 can also be made as small as possible. That is, when the capacitance of the capacitor 14 becomes large, the rate of voltage change with respect to temperature change of the heat-sensitive layer 3c becomes extremely poor at low temperatures, and the temperature detection ability decreases. 3c's temperature detection ability can be significantly improved. Furthermore, since there is no hysteresis with respect to the detected temperature and the detected voltage is not smoothed using a capacitor, there is no time delay caused by these factors, and the temperature ripple can be made as small as possible.

In the above embodiment, the comparator circuit is composed of two operational amplifiers 38 and 39, but the operational amplifier 39 connects the thyristor 7 with an AC power source.
Gate trigger current accurately at zero voltage point of V _{AC
i ​} Such resistors, diodes, etc. may be provided as necessary.

[Effects of the invention] As is clear from the above explanation, the present invention connects a series circuit consisting of a voltage dividing resistor and a heat sensitive body with negative temperature characteristics to an AC power source, and prevents a DC component from flowing through this heat sensitive body. The detected voltage of the temperature detection circuit obtained through a phase advancing circuit having a capacitor that is rated at Since the ignition circuit is operated for a corresponding period of time to bring the controlled rectifying element connected in series to the heating element into a conductive state, it operates in a fail-safe manner against equipment failure, and also protects the heat-sensitive element. Since no DC component is applied, it is possible to prevent the heat sensitive element from deteriorating over time, and since only the positive gate trigger current from the ignition circuit is applied to the control rectifier, a sufficiently large current is applied to the control rectifier. The gate trigger current can flow, and there is no need to select the control rectifier, and the control rectifier is turned on near the zero voltage of the AC power supply without phase control, and becomes a heating element during the positive half cycle of the AC power supply. Since it is energized, it is possible to prevent radio wave interference and quickly raise the temperature of the heating element.Furthermore, the capacitor in the circuit has a small capacity, making it easy to integrate the circuit, and has low temperature ripple and constant temperature characteristics. can provide an excellent temperature control device.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is an electric circuit diagram, Fig. 2 is a plan view of the overheat sensing heating element, Fig. 3 is a plan view of the heat sensitive element, and Fig. 4 is a plan view of the heat sensitive element. FIG. 5 is a diagram showing the temperature characteristics of the heat sensitive body, and FIG. 6 is a diagram showing the voltage or current waveform in the electric circuit. In the drawing, 1 is the electric blanket body, 2 is an overheat sensing heating element, 2b is a heating wire (heating element), 3 is a heat sensitive element, 4 and 5 are AC power terminals, 7 is a thyristor (control rectifying element), 9 and 10 12 is a temperature detection circuit, 13 is a phase advancing circuit, 1 is a resistance and a variable resistance (voltage dividing resistance),
7 is a comparison control circuit, 18 is a reference voltage generator, 19
and 20 is a Zener diode (constant voltage diode), 25 is a diode, 37 is a smoothing capacitor, 38 and 39 are operational amplifiers (comparison circuit), 52
is an ignition circuit, 59 is a transistor (switching element), 62 is a low voltage section, 63 is a constant voltage circuit, 6
4 is a voltage dividing circuit, 65 is a switching circuit, and Y is an output terminal (reference setting voltage output point).

Claims (1)

[Claims for Utility Model Registration] A heating element and a controlled rectifier connected in series between AC power terminals; a heat sensitive element having negative impedance temperature characteristics and provided to receive heat from the heating element; a temperature detection circuit that includes a voltage dividing resistor and the heat sensitive body connected in series between the AC power terminals and outputs an AC voltage obtained by dividing the voltage between the AC power terminals according to the temperature of the heat sensitive body; a phase advance circuit that advances the phase of the AC voltage of the temperature detection circuit to obtain a phase advance detection voltage; a firing circuit for supplying a gate trigger current to the gate of the control rectifier; and a circuit opposite to each other between the AC power supply terminals. polarity, and is conductive during a period exceeding a predetermined breakover voltage of one half-wave period and the other half-wave period of the AC power supply voltage, and is non-conductive during a period below the breakover voltage. Two constant voltage diodes that output a changing voltage near the zero-crossing point of the AC power supply voltage, and a smoothing capacitor connected in parallel to these constant voltage diodes via diodes are provided to control the entire AC power supply voltage. a constant voltage circuit that outputs a constant voltage substantially equal to the breakover voltage over a wave period; a voltage dividing circuit that divides the output voltage of the constant voltage circuit and uses this as a reference setting voltage; A rectified output voltage obtained by full-wave rectification of the output voltage and an output voltage of the voltage divider circuit are provided to perform a switching operation, and in the vicinity of the zero-crossing point of the AC power supply voltage, the reference setting voltage is changed to the reference setting voltage. a switching circuit that outputs an output voltage substantially equal to the output voltage of the constant voltage circuit to the reference setting voltage output point during other periods; and a reference voltage output to the reference setting voltage output point. A temperature control device comprising: a comparison circuit that compares the phase advance detection voltage and outputs a signal for operating the ignition circuit when the latter is larger than the former.