JPH03159090A - Heater circuit and semiconductor heater - Google Patents

Abstract

PURPOSE:To prevent the occurrence of rush current and enable a constant temperature exothermic operation in a steady state exothermic operation zone by applying the constitution wherein a specific thermister has a negative resistance temperature coefficient in a temperature zone below Curie temperature, and a positive resistance temperature coefficient in a temperature zone equal to or above the Curie temperature. CONSTITUTION:Power supplies 1 and 2 are constituted with a switch 2, and current limiting resistors 3 and 4 with a semiconductor heater 4. Furthermore, the semiconductor heater 4 includes a thermister comprising a SrTiO3-PbTiO3 semiconductor material. This thermister has a negative resistance temperature coefficient in a temperature zone below Curie temperature. In a low temperature zone immediately after turning on a power supply, therefore, the thermister works as a high resistance body given by the negative resistance temperature coefficient. On the other hand, the thermister has a positive resistance temperature coefficient in a temperature zone equal to or above the Curie temperature. The thermister, therefore, is capable of self-temperature control function in a steady state exothermic operation zone. According to the aforesaid construction, rush current can be restrained and the thermister can operate as a constant temperature exothermic body in the steady state exothermic operation zone.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a heater circuit and a semiconductor heater, and uses a thermistor whose resistance-temperature characteristic is V characteristic as the semiconductor heater, thereby achieving a constant temperature that has an inrush current prevention function. Accordingly, it is possible to provide a heater circuit and a semiconductor heater.

<Prior Art> Conventionally, a semiconductor heater using a positive temperature coefficient thermistor having a positive temperature coefficient of resistance is well known. A positive temperature coefficient thermistor exhibits low resistance in a low temperature range, but when the temperature reaches near the Curie temperature, the resistance value increases rapidly, and it has a self-temperature control function that automatically controls the self-heating temperature. As a safe and highly reliable semiconductor heater, it is used as a heat source for various heating appliances.

<Problems to be Solved by the Invention> However, since the positive temperature coefficient thermistor has a low resistance value in a low temperature region, there is a problem in that the inrush current when the power is turned on increases. This difficulty is, for example, when adding overcurrent protection II1 function parts such as fuses in consideration of overcurrent protection due to deterioration of a positive temperature coefficient thermistor, these overcurrent protection function parts must be set to values that take into account inrush current. There is also the problem that it is difficult to consistently determine only the optimum value for overcurrent protection.

JP-A-61-159705 discloses an overcurrent protection element, which is not used as a heater circuit, but is another important use of a positive temperature coefficient thermistor, by combining a positive coefficient thermistor with a negative coefficient thermistor, and using a negative coefficient thermistor. Discloses technology to prevent inrush current. However, even when this conventional technique is applied to a heater circuit, a combination of two types of positive and negative thermistors is essential, which leads to an increase in the number of parts and an increase in size.

Therefore, the object of the present invention is to solve the above-mentioned conventional problems, to ensure inrush current prevention effect by itself, and to have a self-temperature control function in the steady-state heating operation region to stably perform constant-temperature heating operation. An object of the present invention is to provide a semiconductor heater and a heater circuit.

Means for Solving the Problems> In order to solve the above problems, the present invention provides a heater circuit having a semiconductor heater, wherein the semiconductor heater includes a thermistor made of a 5rTiOs-PbTiO3 based semiconductor material, and the thermistor includes a , has a negative temperature coefficient of resistance in a temperature range lower than the Curie temperature, and has a positive temperature coefficient of resistance in a temperature range higher than the Curie temperature.

Function> The semiconductor heater includes a thermistor made of a 5rTiOs PbTiOs semiconductor material, and this thermistor has the following properties:
Since it has a negative temperature coefficient of resistance in a temperature range lower than the Curie temperature, it operates as a high resistance element given by the negative temperature coefficient of resistance in the low temperature range immediately after power is turned on.

Therefore, rush current is suppressed.

Moreover, it has a positive temperature coefficient of resistance in the temperature range higher than the Curie temperature, so in the steady heat generation operation range, it can provide the same self-temperature control function as a conventional positive temperature coefficient thermistor.
Operates as a constant temperature heating element.

The above-mentioned negative temperature coefficient of resistance and negative temperature coefficient of resistance can be obtained with a single thermistor, so unlike the conventional technology that combines a negative characteristic thermistor and a positive characteristic thermistor, the number of parts is small and the size is small. become.

<Example> FIG. 1 is an electrical circuit diagram of a heater circuit according to the present invention.
In the figure, 1 is a power source, 2 is a switch, 3 is a current limiting resistor, and 4 is a semiconductor heater. The semiconductor heater 4 is
As shown in Figure 2, a thermistor (hereinafter referred to as V (referred to as a characteristic thermistor). Therefore, the Curie temperature Tc.

It shows the lowest resistance value in the vicinity.

■The characteristic thermistor is BaT, which has a positive temperature coefficient of resistance.
i0. Obtained by replacing barium Ba in the semiconductor ceramic composition with strontium S and lead Pb, which have the same valence and approximate ionic radius, to produce a 5rTlOs-PbTiOs semiconductor. ■Characteristics Thermistor manufacturing method and electrode The structure etc. may be the same as that of a conventionally well-known positive temperature coefficient thermistor.

Although the power supply 1 is shown as a DC power supply in the circuit example of FIG. 1, it may be an AC power supply as shown in FIG.

The resistor 3 is inserted to control the power supplied to the semiconductor heater 2 constituted by a characteristic thermistor, and its resistance value R is determined in consideration of the heat load capacity. The resistor 3 can be replaced by a variable resistor or a current control element or control circuit other than the resistor, or can be omitted if such control is unnecessary.

Next, the circuit operation of the heater circuit shown in FIGS. 1 and 3 will be explained with reference to the resistance temperature characteristic diagram shown in FIG. When the switch 2 is open, the temperature TP of the semiconductor heater 4, which is a thermistor with characteristic (1), is a temperature determined by the environmental temperature, and its resistance value RP is a value corresponding to the temperature TP. It is assumed that the temperature T is lower than the Curie temperature Tc. In this state, when switch 2 is closed,
■Circuit current 1V in semiconductor heater 4 made of characteristic thermistor
flows, and energy Rp'lv' is consumed in the semiconductor heater 4. The semiconductor heater 4 is self-heated by this Joule heat, and its temperature increases. The generated heat ff1pp (W) is expressed as follows with respect to the resistance value R1 of the resistor 3, the resistance value RP5 of the semiconductor heater 4, and the voltage E of the power source 1.

Pp(W)=Rp −E2/ (Rp +R)'(w)
Since the operating region of the semiconductor heater 4 at this time is a region having a negative temperature coefficient of resistance in the characteristic (1), the operating point P shifts in a direction in which the resistance value R becomes lower due to the above-mentioned self-heating. Therefore, the circuit current Iv flowing through the semiconductor heater 4 further increases, Joule heat increases, and this further causes the semiconductor heater 4 to self-heat. With this series of actions,
The operating point P of the semiconductor heater 4 changes at an accelerated rate up to the Curie temperature Tc. In this way, immediately after the switch 2 is closed and the power supply 1 is turned on, it operates as a high resistance element given by the negative temperature coefficient of resistance, so that the inrush current is automatically suppressed by the characteristics of the semiconductor heater 4 itself. be done.

When the operating point P exceeds the Curie temperature Tc due to the heating effect described above, the semiconductor heater 4 enters a region having a positive temperature coefficient of resistance. In this area, the self-temperature control theory discussed in conventional positive temperature coefficient thermistors prevails. That is, when the resistance value of the semiconductor heater 4 increases due to self-heating, the circuit current IV decreases. As a result, the amount of heat generated by the semiconductor heater 4 decreases, and the operating point P moves toward the Curie temperature Tc. That is, the self-temperature control function operates so that the energy consumed by the semiconductor heater 4 is maximized, or in other words, the amount of heat generated by the semiconductor heater 4 is maximized. The amount of heat generated P (w) at this time is the resistance 3
The resistance value R1 of the semiconductor heater 4 at the Curie temperature Tc is expressed as follows, where the resistance value ROs is the voltage ε of the power supply 1.

P (w)=Ro−E”/(Ro+R)”(w
) As shown in the above formula, the amount of heat generated P (w) can be variably adjusted by changing the resistance value RO at the Curie temperature Tc. Furthermore, by changing the resistance value R of the resistor 3 and the voltage value E of the power source 1, the amount of heat generated P (w) can be variably adjusted.

<Effects of the Invention> As described above, according to the present invention, the following effects can be obtained.

(a) The semiconductor heater constituting the heater circuit is made of 5rTi
Since the thermistor includes a thermistor made of an O,-PbTiO3-based semiconductor material and has a negative temperature coefficient of resistance in a temperature range lower than the Curie temperature, it is possible to provide a heater circuit and a semiconductor heater that can suppress inrush current.

(b) Since the thermistor constituting the semiconductor heater has a positive temperature coefficient of resistance in a temperature range higher than the Curie temperature, it is possible to provide a heater circuit and a semiconductor heater that operate as a constant temperature heating element in a steady heat generation operation range.

(C) Unlike the conventional technology in which a negative characteristic thermistor and a positive characteristic thermistor are combined, the number of parts is small, and a small heater circuit and semiconductor heater can be provided.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of a heater circuit according to the present invention, FIG. 2 is a diagram showing resistance temperature characteristics of a semiconductor heater constituting one heater circuit, and FIG. 3 is another embodiment of a heater circuit according to the present invention. FIG. 4... Semiconductor heater 1 Fig. Fig. Main skin Fig.

Claims (2)

[Claims] (1) A heater circuit having a semiconductor heater, wherein the semiconductor heater is SrTiO_3-PbTiO_3
The thermistor is characterized in that it has a negative temperature coefficient of resistance in a temperature range lower than the Curie temperature and a positive temperature coefficient of resistance in a temperature range higher than the Curie temperature. heater circuit. (2) A semiconductor heater including a thermistor made of a SrTiO_3-PbTiO_3-based semiconductor material, wherein the thermistor has a negative temperature coefficient of resistance in a temperature range lower than the Curie temperature and a positive resistance temperature coefficient in a temperature range higher than the Curie temperature. A semiconductor heater characterized by having a temperature coefficient of resistance of .