JPS6154174A - Heater disconnection and leakage detector circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a heater disconnection detection and earth leakage detection circuit for a heating element in an electric carpet or the like.

(Background Art) Figure 3 is a cross-sectional view showing the configuration of a planar heating element having two systems of heaters H, , ) I2, which is made of an organic semiconductor having a negative impedance characteristic with respect to 1 degree. A heater pattern of heaters H, . FIG. 4 shows a part of the heating element in a plan view, and the two heaters H, , H, are wired in parallel so that no current flows between the heater patterns.

Since the impedance of the temperature change element T disposed between the heaters H, H2 and the temperature detection electrode 8iiS changes according to the temperature of the heating element, a temperature detection signal is obtained from this impedance change, and the temperature control circuit By the operation of 1), the power supply to the heater is controlled so that the desired temperature is reached. Furthermore, by disconnecting either of the heaters H, H2 from the circuit using a changeover switch or the like, the overall capacity of the heating element can be changed.

By the way, in the configuration of the heating element as described above, the two heaters H, H2 generate strong electric non-coupling via the temperature change element T, and during normal use, the heater pattern changes as described above. In parallel, i! il! 2, so no current flows between the two heaters, but if one heater was disconnected, the potential balance between the two heater patterns would be disrupted, causing current to flow between both heaters, creating a dangerous situation. .

In other words, FIG. 5 shows a case where a disconnection occurs at the terminal a of heater H, and while the normal heater H2 has a distribution of 100 to ov when viewed from the ground point, the disconnected heater H1 For example, since the voltage is uniformly 100V, a potential difference occurs between adjacent heater patterns, and a current 1 corresponding to this potential difference flows. Here, the point where the current value is the largest is the part of the pattern near the terminal part a where the IITS is applied, so if that area is locally insulated with a cushion, etc., the temperature of that part will rise. However, the temperature increase causes the impedance of the temperature change element T having negative impedance characteristics to decrease by -IJ, which further increases the current, which may lead to a dangerous situation due to so-called thermal runaway.

In addition, it is not limited to the two systems ζζ as described above, but even systems with a larger number of systems have similar drawbacks.

(Object of the Invention) The present invention has been proposed in view of the above points, and its purpose is to provide a heating system using a heating element having two or more heater systems in order to perform power switching. Safe heater disconnection detection and leakage detection that can quickly stop power supply when a heater is disconnected, and can also stop power supply when a leak occurs in any part of the device. The purpose is to provide circuits.

(σa indication of the invention) DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to drawings showing embodiments.

FIG. 1 shows the overall configuration of a heating device to which the heater disconnection detection and earth leakage detection circuit of the present invention is applied.

In the figure, H, and H2 are the heaters of the heating elements shown in FIGS. 3 and 4, and in this example, the H and H can be separated from the road by a two-way switch S and SW2, It is possible to switch between high-power heating using the heaters H, , H, and low-power heating using only the heater H8. That is, the heater H2 is directly connected to the commercial power source (AClooV) via the relay contacts 'V, p'V@, and the heater H1 is connected to both ends of the heater H2 via the double-ended switches sw, , sw2. There is. In addition, ZCT is a zero-phase transformer installed to detect unbalanced current, and is a feature of the present invention. It is installed through the core of the zero-phase transformer ZCT to serve as the primary winding.
The secondary of the zero-phase transformer ZCT is the amplification circuit described later.
Connected to the input terminal of i4.

On the other hand, 1 is a power supply circuit for supplying DC power to the circuit sections, its input terminal is connected to a commercial power source, and its DC output terminal is connected to each circuit section. In addition, 2 is a relay contact inserted between 1:1 data H,,H, and the commercial power supply'! /
This is a relay circuit that opens and closes 1F'y2, and is driven by the output signal of the temperature control circuit 3. Although the details of the temperature control circuit 3 are omitted, the heater H,
, H2, a signal is obtained from the temperature detection T4 pole provided opposite to H2, a signal corresponding to the temperature of the heating element is detected, and the signal is compared with the set temperature to instruct whether to energize or stop the heater. It has the function of sending out.

Next, the output terminal of the amplification circuit 4 to which the secondary winding ML of the zero-phase transformer ZCT is connected to the input terminal is connected to the signal processing circuit 5.
The output terminal of the signal processing circuit 5 is connected to the relay circuit 2 together with the output terminal of the temperature control circuit 3.

FIG. 2 shows a concrete circuit configuration of the configuration shown in FIG. 1, and the same parts as in FIG. 1 are given the same reference numerals. In the figure, an operational amplifier A constitutes an amplifier circuit 4, and its inverting input terminal is connected to its own output terminal via a resistor R4, and the output voltage V of the power supply circuit 1 is
The non-inverting input terminal is connected to the point where ce is divided by the resistors R, , R, through the resistor R5 and the capacitor C1, and the non-inverting input terminal is connected to the resistor R,, R, through the secondary winding of the zero-phase transformer ZCT.
It is connected to the second connection point.

Further, the output terminal of the operational amplifier A is connected to the ground via the resistor R6 and the capacitor C2 after passing through the diode D, and is also connected to the operational amplifier A2 constituting the signal processing circuit 5.
is connected to the non-inverting input terminal of The inverting input terminal of the operational amplifier A2 connects the output voltage Vee of the power supply circuit 1 to the resistor FL.
The resistance R,,R, of the circuit divided by ,,R,,R,
The output terminal of the operational amplifier A2 is connected to the connection point of the resistor R? It is connected via a resistor R9 to the base of a transistor Q, whose collector and emitter are connected to both ends of the transistor Q.

On the other hand, in the relay circuit 92, a relay RY is connected between the output terminal of the ri power supply circuit and the collector of a transistor Q3 whose emitter is grounded, and the base of the transistor Q is connected to the temperature control circuit 3 through a resistor R11. It is connected to the output terminal and is also grounded through the collector-emitter of a transistor Q2 whose base is connected to the output terminal of the operational amplifier A2 through a resistor R10.

The operation will be explained below with reference to FIG.

In normal temperature control, the operation of the temperature control circuit 3 ζζ
The temperature of the heating element is compared with the set temperature, and if the temperature of the heating element is lower than the set temperature, the signal given from the temperature control circuit 3 to the transistor Q becomes high level, turns on the relay Ry, and closes the relay contact. 'V1p' V2 is turned on to energize the heater, and conversely, when the temperature is higher than the set temperature, the relay contact is turned off and energization is stopped. Through these operations, the heating element is maintained at a desired temperature.

It is also possible to switch the heat generation temperature according to the ambient temperature etc. by operating the changeover switches SW, SW.

Next, if a Tanabata wire breakage occurs, for example, if the terminal part a of the heater H1 is broken as shown in Fig. 5, then the sum of the currents 1 flowing between both heaters H, H, flows from one end of the heater H1, and the currents in the current paths at both ends of the heater H1 become unbalanced. Therefore, this unbalanced current Σi
is detected by zero-phase transformer ZCT, and its secondary winding @L
A voltage will be generated. This signal is then applied to resistor FL3. After being amplified by the amplification factor determined by the ratio of R4, it is rectified and smoothed by diode D1, capacitor C2, and resistor R6, and then output to operational amplifier A.
2 will be compared with the voltage set by the resistors R,,R,,R,. Here, the resistances RS, R,, R
, +f zero-phase transformation @1zcT Since operational amplifier A2 is set to sufficiently invert when unbalanced current is detected, the output of operational amplifier A2 changes from low level to high level at the same time as unbalanced current is detected. Then, the transistor Q2 is turned on, the base of the transistor Q3 is forcibly pulled down to a low level, and the current supply to the heater is stopped regardless of the operation of the temperature control circuit 3, thereby shifting to the safety mode. , In addition, as the output of operational amplifier A2 changes to high level, transistor Q turns on, and resistor R
7 and short-circuit the voltage V- applied to the inverting input terminal of operational amplifier A2 as V-=VVce (R6+R7)/(
Rs + R, + R7) to V- = Vec-R, / (Rs + R,),
Lock state. Therefore, the relay contact'! /1 p
Even if 'V@ is turned off and the energization to the heater is stopped and no voltage is generated in the secondary winding ML of the zero-phase transformation #ZCT, the state of energization cutoff can be maintained.

Although the above explanation deals with the case where the terminal part a of the heater HL is disconnected, the same applies even if the disconnection occurs in other parts. Even if there is an unbalanced current, an unbalanced current is generated in the heater H4, so by providing an unbalanced current detection means only in the heater H2, a disconnection can be detected.

On the other hand, if a current leakage occurs in a part of the circuit, for example if a conductor such as a pin is stuck in a heating element and a current leakage occurs on the floor, the unbalanced current in the AC line due to this leakage will be zero. This is detected by the phase transformer ZCT, and the same operation as above is performed to stop energizing the heater and shift to the safety mode.

(Effects of the Invention) As described above, in the present invention, in a heating element having at least two heater patterns arranged in parallel to each other, a current path at both ends of one heater pattern; A zero-phase transformer that detects unbalanced current is installed in common on the current path connecting the heating device and the commercial power supply, and it detects disconnection of the heater pattern and leakage, so if one of the heaters is disconnected. Furthermore, when a current leakage occurs, it is possible to quickly stop the current supply, and there is an advantage that a highly reliable and safe disconnection detection/earth leakage detection circuit can be provided.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing FIG. 1 in more detail, and FIG. 3 is a diagram showing the configuration of a heating element to which the present invention is applied. FIG. 4 is a cross-sectional view, and FIG. 4 is a plan view showing the same pattern of the heating element as described above. FIG. 5 is a conceptual diagram of unbalanced current generated when the heater is disconnected. H,, H2...Heater, T...Temperature change element, S...Temperature detection electrode, 1...
Power supply circuit, 2...Relay circuit, 3...Temperature control circuit, 4...Amplification circuit, 5...Signal processing circuit, zCT...Zero Phase transformer, L...
・Secondary winding of zero-phase transformer, SL, SF3...
Double switching switch, Ry... Relay, ry
Hp ry2... Relay contact, A,, A2.
...Op amp, Q. ~Q3...Transistor, R1~R1,...
...Resistance, C,, C, ...Capacitor, D,
,D...Diode engineering,

Claims (1)

[Claims] In a heating element having at least two heater patterns arranged in parallel to each other, the current path at both ends of one heater pattern and the current path connecting the heating device and the commercial power supply are commonly unbalanced. A heater disconnection detection/earth leakage detection circuit is provided with a zero-phase transformer for detecting current, and detects heater pattern disconnection and earth leakage.