JPS6112625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control circuit for a planar heating element used in carpets, roof heaters, etc., and its object is to provide a heater and a heat-sensitive electrode, and further provide a heat-sensitive element having a temperature impedance characteristic between them. To provide a temperature control circuit for a planar heating element, which enables temperature control through an intervening method, and which does not cause an electric shock accident even if a metal pin is inserted into the planar heating element from the outside.

FIGS. 1a, b, and c show various configurations of the planar heating element, and the one in FIG. A heat-sensitive element 3 is interposed in the heat-sensitive electrode 2.
has a full-surface shape with no meandering formation. In FIG. 1b, the heat-sensitive electrode 2 is formed in a meandering plane like the heater 1, but the width of the conductive part is larger than the width of the conductive part of the heater 1. In the case shown in FIG. 1c, the conductive parts of the heater 1 and the heat-sensitive electrode 2 are formed to have the same width.

As shown in FIG. 2, the output voltage of an oscillation circuit 6, which is supplied with power from a control power supply unit 5 connected to a commercial frequency AC power supply 4, is applied to the sheet heating element by a coupling circuit 7 including an impedance conversion unit and a transformer. Then, the magnitude of the voltage applied between the heater 1 and the heat-sensitive electrode 2 is detected by the detecting section 8 including a transformer and a resonant circuit, and the switching section 9 opens and closes the switching contact 10 of the relay. More heater 1
The temperature of the heater 1 is controlled by intermittent feeding lines connected to the heater 1. However, when the voltage of the AC power supply 4 applied to both ends of the heater 1 is 100V, 50V because it is connected to heater 1 through element 3
voltage is applied. Therefore, Fig. 1a,
If the heat-sensitive electrode 2 is wider than the conductive part of the heater 1 as shown in b, the metal pin inserted from the outside will come into contact with only the heat-sensitive electrode 2, and in this case, there will be no change in the detection signal, so opening and closing will not be possible. Contact 10,1
0 will not work and there is a risk of electric shock. and the first
If the heater 1 and the heat-sensitive electrode 2 are conductive parts with the same width as shown in Figure c, the metal pin will pierce both at the same time, so the impedance between them will be zero, and in this case, the switching part 9 will turn off the switching contact 10. Therefore, there is little danger. However, matching both conductive parts as shown in FIG. 1c is difficult from a manufacturing standpoint because the same pattern must be adopted and misalignment during polymerization must be eliminated.

In view of this, the present invention aims to improve the temperature control circuit so that there is no risk of electric shock in any of the above-described planar heating elements.

The embodiment of the temperature control circuit for the planar heating element of the present invention will be described below with reference to FIGS. Two power supply lines extending from both ends are connected to the heater 1 through the primary winding 13 of the zero-phase current transformer 11 and the switching contact 10, respectively, so as to detect the unbalanced current of the power supply lines. Vessel 11-1
Next, a control power supply section 5 to the temperature control circuit is provided which is connected to the AC power supply 4 through the windings 13, 13, and connected to the control power supply section 5, the oscillation section 6, the coupling section 7, the detection section 8, and the switching section are connected. 9 is provided, and the high frequency signal voltage of the oscillator 6 is applied via the coupling circuit 7 between the heater 1 and the heat sensitive electrode 2 with the heat sensitive element 3 of the planar heating element interposed therebetween, and the signal voltage at both ends thereof is detected. The opening/closing contacts 10, 10 of the switching section 9 including a relay are operated, and the output of the secondary winding 12 of the zero-phase current transformer 11 is used to negate the signal voltage of the detecting section 8 and to switch on/off. Contact 10,1
An earth leakage detection section 14 is attached to the switching section 9, which turns the switch 0 off.

A concrete implementation circuit of the switching section 9 to which the earth leakage detection section 14 is attached is shown in FIG. In the figure, the switching section 9 includes a switching circuit composed of resistors R ₁ , R ₂ and gates G ₁ , G ₂ , and the output of the switching circuit is connected to resistors R ₃ , R ₄ .
This is used as a gate signal for the thyristor SCR ₁ , and consists of an output circuit that connects the thyristor SCR ₁ , the relay L ₁ , and the diode D ₁ in series to the AC power supply 4. And diode _D2 is connected for protection.

The earth leakage detection unit 14 includes a gate resistor R ₅ connected to the secondary winding 12 of the zero-phase current transformer 11 and a thyristor.
It consists of an SCR ₂ , a holding power source E ₁ , and a resistor R ₆ , and is connected to the gates G ₁ and G ₂ of the switching section 9 to switch their levels.

Therefore, when the temperature of the heater 1 is high, the control voltage between the heater 1 and the heat-sensitive electrode 2 becomes small, and the detection voltage of the detection section 8 also decreases, and the output of the gate _G2 becomes L level in the switching section 9, and the thyristor is activated.
Turn off SCR ₁ and open/close contacts 10, 10 of relay L ₁
Turn off. Conversely, when the temperature of the heater 1 decreases, the detection voltage of the detection section 8 increases, and the output of the gate _G2 of the switching section 9 becomes H level, and the switching contact 10,
10 is turned on and power is supplied to the heater 1.

In the above temperature control, when the currents flowing through the primary windings of the zero-phase current transformer 11 are completely equal, no voltage is generated in the secondary winding 12 and the above control operation is repeated. If a metal pin is stuck in the heater 1 or the heat-sensitive electrode 2 and an electric shock or leakage occurs, the current flowing through the primary windings 13 and 13 on both sides of the AC power source 4 will be unbalanced, and a voltage will be generated in the secondary winding 12. Thyristor SCR ₂ of the earth leakage detection section 14
turns on.

This thyristor SCR ₂ holds the power supply E ₁ from the resistor R ₆
The gate is held on by the current flowing through it.
G ₁ and G ₂ are short-circuited, and the output of gate G ₂ is L.
level. Therefore, the signal from the detection unit 8 inputted through the resistor _R1 is negated, the thyristor _SCR1 is turned off, and the switching contacts 10, 10 are turned off.

According to the temperature control circuit described above, FIG.
If the width of the conductive part of the heat-sensitive electrode 2 is larger than the width of the conductive part of the heater 1, and the metal pin sticks from the heat-sensitive electrode 2 side, even if it stands only on the heat-sensitive electrode 2, the metal When an electric shock or leakage occurs through the pin, the leakage detection section 14 activates the switching section 9 regardless of the detection signal from the detection section 8.
is activated to cut off the power supply from the AC power source 4 to the planar heating element to prevent an unexpected situation from occurring. Negating the detection signal is advantageous in that the opening/closing contacts 10, 10 do not move when the metal pin is pierced when the temperature of the sheet heating element has decreased. The attachment speeds up the operation of the switching part 9 and ensures reliable off operation of the opening/closing contacts 10, 10, etc.
According to the temperature control circuit of the present invention, it can be used for various configurations of sheet heating elements, and the range of application can be increased.

[Brief explanation of the drawing]

1 and 2 show conventional examples, in which FIG. 1a shows a planar heating element in which the heat-sensitive electrodes are all over the surface, and FIG. FIG. 1c is a planar heating element having the same width as that of FIG. 1b, and FIG. 2 is a circuit diagram of a temperature control circuit. 3 to 4 show an embodiment of the temperature control circuit for the planar heating element of the present invention, FIG. 3 is a block diagram of the temperature control circuit, and FIG. 2 is a circuit diagram showing details of the switching section. DESCRIPTION OF SYMBOLS 1... Heater, 2... Heat-sensitive electrode, 3... Heat-sensitive element, 4... AC power supply, 5... Control power supply section, 6...
Oscillating section, 7... Coupling section, 8... Detecting section, 9... Switching section, 10... Switching contact, 11... Zero phase current transformer, 12... Secondary winding, 13... Primary winding line,
14...Earth leakage detection section.

Claims (1)

[Claims] 1. A control power supply unit that is connected to the heater from both ends of the AC power supply through the primary winding and switching contacts of the zero-phase current transformer, and connected to the AC power supply through the primary winding of the zero-phase current transformer; An oscillation section, a coupling section, a detection section, and a switching section are connected to the control power supply section, and the high-frequency signal voltage of the oscillation section is connected to the heater and the heat-sensitive electrode with the heat-sensitive element of the planar heating element interposed through the coupling circuit. In addition, the signal voltage at both ends of the current transformer is detected by a detecting section to operate the switching contact of the switching section, and the signal voltage at the detecting section is detected by the output of the secondary winding of the zero-phase current transformer. 1. A temperature control circuit for a planar heating element, wherein a leakage detection section is attached to the switching section so as to turn the opening/closing contact off.