KR100674726B1 - PTC sensor circuit - Google Patents

Abstract

The PC sensor circuit according to the present invention includes a microcomputer; A tilt change unit which adjusts a resistance change rate of the PC element; A buffer unit connected to the gradient converter to prevent distortion of a resistance change rate of the PC element; An amplifier including a predetermined OP amplifier to amplify the resistance change rate; And an amplification adjusting unit configured to enable multi-stage control by changing an input stage resistance of the OP amplifier configured in the amplifying unit, wherein the gradient change unit includes at least two transistors so that the reference resistance value of the Pc sensor input unit is changed. Characterized in that.

By the configuration of the PTC sensor circuit as proposed, the difference in A / D resolution for each temperature band can be minimized.

In addition, there is an advantage that the temperature detection quality can be improved by simultaneously changing the amplification degree and the reference resistance for each temperature band.

PTC, OP Amp, Transistor

Description

PTC sensor circuit

1 is a circuit diagram illustrating a PTC sensor circuit according to the prior art.

2 is a PTC sensor circuit diagram according to the spirit of the present invention.

3 is a view for explaining A / D resolution in a low temperature region of a PTC sensor circuit according to the spirit of the present invention;

4 is a diagram for explaining A / D resolution in a high temperature region of a PTC sensor circuit according to the spirit of the present invention;

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PTC sensor circuit, and more particularly, to a PTC sensor circuit for improving temperature sensing quality by simultaneously changing the amplification and the reference resistance so as to minimize the difference in resolution for each band. will be.

Sensors that detect high temperatures in cooking appliances such as microwave ovens mainly use positive temperature coefficient (PTC) elements.

The PTC element has a low resistance at low temperatures such as room temperature and has conductivity, but as the temperature increases, the electrical resistance increases rapidly in a relatively narrow temperature range. Accordingly, the PTC conductive polymer composition having such characteristics is suitable for use as an electric device such as a circuit protection device that varies with ambient temperature and current conditions.

1 is a circuit diagram illustrating a PTC sensor circuit according to the prior art.

Referring to FIG. 1, the PTC sensor circuit of the related art does not distort the slope of the slope change unit 1 for converting the slope of the resistance change with respect to the temperature of the PTC element, and the slope of the resistance change converted from the slope converter 1. And a buffer section 2 for amplifying the slope.

In detail, the slope converter 1 is connected to the fourth capacitor C4 and the fifth resistor R5 and is connected to the emitter terminal of the first transistor Q1. The collector terminal of the first transistor Q1 is connected to a fourth resistor R4, and the fourth resistor R4 is connected in parallel with the fifth resistor. The fourth resistor R4 is connected to the third capacitor C3.

In addition, the buffer unit 2 includes a first OP amplifier IC1 and a second capacitor C2 to which a 12V power difference is applied.

In more detail, the positive input terminal of the first OP amplifier IC1 is connected to the fourth resistor R4 and the third capacitor C3, and a voltage of 12V is applied to the first OP amplifier IC1. .

In addition, the amplifier 3 includes a feedback circuit, and includes a second OP amplifier IC2, and the positive input terminal of the second OP amplifier IC2 is connected to the first OP amplifier. It is connected to the output terminal of (IC1), the negative input terminal is connected to the ground point and the second resistor (R2).

In addition, the second resistor R2 is connected to the output terminal of the second OP amplifier IC2, so that a feedback circuit is configured to amplify a slope indicating a resistance change rate with respect to the temperature of the PTC device. The output terminal of the second OP amplifier IC2 is connected to the first resistor R1, and the first resistor R1 is connected to the first diode D1, the first capacitor C1, and the microcomputer M1. .

On the other hand, the operation of the PTC sensor circuit according to the prior art will be described.

The resistance change of PTC, which can be used even at high temperatures, is generally small. The high temperature usually means more than 500 ℉, and in the case of PTC 1000, PTC has a change of about 1000 ~ 2500Ω.

And since the amount of change in the high temperature of the said PTC is small, it is amplified by the said amplification part 3, and is used as an input of the microcomputer M1.

In addition, when amplification is performed, a high temperature region which cannot be used is generated. In this case, the microcomputer M1 transmits the changed slope to the amplification unit 3 by changing the slope in the gradient converter 1. The high temperature side is input and used.

The amplification degree is (1 + R2 / R3), and the slope becomes Rth / (R5 // R4 + Rth) in the low temperature region. In the high temperature region, Rth / (R5 + Rth) is obtained.

On the other hand, the PTC sensor circuit of the prior art has a high A / D resolution because the inclination of the low temperature region is relatively larger than the inclination of the high temperature region. Therefore, in the high temperature region, the slope is relatively reduced, which makes it difficult to A / D converter with the same resolution.

In addition, A / D resolution in a high temperature region has a relatively poor problem.

In addition, since the A / D resolution in the high temperature region is not good, there is a problem that the deviation in the temperature detection in the high temperature region compared to the low temperature is severe.

The present invention is proposed to solve the above problems, and an object of the present invention is to propose a PTC sensor circuit for minimizing the difference in resolution for each temperature band.

In addition, an object of the present invention is to propose a PTC sensor circuit capable of improving the temperature sensing quality by simultaneously changing the amplification degree and the reference resistance for each temperature band.

In addition, it aims to propose a PTC sensor circuit that can improve the temperature monitoring and temperature control logic design and use quality by minimizing the temperature sensing variation by temperature band.

PC sensor circuit according to the present invention for achieving the above object is a microcomputer; A tilt change unit which adjusts a resistance change rate of the PC element; A buffer unit connected to the gradient converter to prevent distortion of a resistance change rate of the PC element; An amplifier including a predetermined OP amplifier to amplify the resistance change rate; And an amplification adjusting unit configured to enable multi-stage control by changing an input stage resistance of the OP amplifier configured in the amplifying unit, wherein the gradient change unit includes at least two transistors to change the reference resistance of the PC sensor input unit. It is characterized by that.

By the configuration of the PTC sensor circuit as proposed, the difference in A / D resolution for each temperature band can be minimized.

In addition, there is an advantage that the temperature detection quality can be improved by simultaneously changing the amplification degree and the reference resistance for each temperature band.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail. However, the spirit of the present invention is not limited to the embodiments in which the present invention is presented, and those skilled in the art who understand the spirit of the present invention can easily make other embodiments by adding, changing, deleting, and adding components within the scope of the same idea. It may be proposed, but this will also fall within the scope of the present invention.

FIG. 2 is a PTC sensor circuit diagram according to the spirit of the present invention, FIG. 3 is a view illustrating an A / D resolution in the low temperature region of the PTC sensor circuit according to the spirit of the present invention, and FIG. It is a figure explaining a D resolution.

2 to 4, the PTC sensor circuit of the present invention does not distort the slope of the gradient converter 10 for changing the reference resistance value of the sensor input unit and the slope of the resistance change converted from the gradient converter 10. And a buffer unit 20 for amplifying a resistance change to facilitate temperature sensing at a high temperature, and an amplification adjusting unit 40 constituting a feedback circuit in the amplifying unit 30.

In detail, the slope converter 10 is configured such that a 5V power supply is connected to the thirteenth capacitor C13, the fourteenth resistor R14, the tenth transistor Q10, and the eleventh transistor Q11.

The thirteenth capacitor C13 is connected in parallel with the fourteenth resistor R14, the tenth transistor Q10, and the eleventh transistor Q11. The emitter terminal of the tenth transistor Q10 is connected to the 5V power supply, and the collector terminal is connected to the fifteenth resistor R15.

In addition, the emitter terminal of the eleventh transistor Q11 is connected to the 5V power supply, and the collector terminal is connected to the thirteenth resistor R13. The thirteenth resistor is connected to the fourteenth resistor R14, the fifteenth resistor R15, and the twelfth capacitor C12, and the other side of the twelfth capacitor C12 is grounded.

In addition, the buffer unit 20 includes a tenth OP amplifier IC10 and an eleventh capacitor C11 to which a 12V power difference is applied.

In more detail, the positive input terminal of the tenth OP amplifier IC10 is connected to the thirteenth, fourteenth, and fifteenth resistors R13, R14, and R15 and the twelfth capacitor C12, and the tenth operational amplifier IC10. ), A voltage difference of 12 V is applied.

In addition, the amplifying unit 30 includes a feedback circuit, and includes a twentieth operational amplifier IC20, and the positive input terminal of the twentieth operational amplifier IC20 is the tenth operational amplifier. It is connected to the output terminal of the IC10, the negative input terminal is connected to the twelfth resistor (R12).

The eleventh resistor R11 and the amplification controller 40 are connected between the negative input terminal and the output terminal of the twentieth OP amplifier IC20.

In addition, the amplification control unit 40 includes twelfth to fifteen transistors Q12, Q13, Q14, and Q15 connected to the microcomputer M10 and the tenth diode D10.

In more detail, a seventeenth resistor R17 is connected to the collector terminal of the fifteenth transistor Q15, and the seventeenth resistor R17 is connected to an output terminal of the twelfth OP amplifier IC20 and an eleventh resistor R11. Connected. The emitter terminal of the fifteenth transistor Q15 is connected to the negative input terminal of the twentieth OP amplifier IC20 and the eleventh resistor R11.

The collector terminal of the fourteenth transistor Q14 is connected to an eighteenth resistor R18, and the eighteenth resistor R18 is an output terminal of the twentieth OP amplifier IC20, the eleventh resistor R11, and the eighth resistor. 17 is connected to the resistor (R17). The emitter terminal of the fourteenth transistor Q14 is connected to the emitter terminal of the fifteenth transistor Q15.

The emitter terminal of the thirteenth transistor Q13 is connected to the anode terminal of the first zener diode ZD1, and the cathode terminal of the first zener diode ZD1 is connected to the output terminal of the 20th OP amplifier IC20. do.

The collector terminal of the twelfth transistor Q12 is connected to the collector terminal of the thirteenth transistor Q13, and the emitter terminal is connected to the cathode terminal of the first zener diode ZD1 and the twelfth OP amplifier IC20. It is connected to the output terminal.

In addition, the microcomputer M10 is connected to the tenth resistor R10, the anode terminal of the tenth diode D10, and the tenth capacitor C10, and the tenth resistor R10 is connected to the twelfth transistor Q12. Is connected to the collector terminal of and the collector terminal of the thirteenth transistor Q13.

The cathode terminal of the tenth diode D10 is connected to a 5V power supply, and one side of the tenth capacitor C10 is grounded.

On the other hand, the operation of the PTC sensor circuit according to the present invention will be described.

The resistance change of PTC, which can be used even at high temperatures, is generally small. The high temperature usually means more than 500 ℉, and in the case of PTC 1000, PTC has a change of about 1000 ~ 2500Ω.

Since the amount of change at the high temperature of the PTC is small, it is amplified by the amplifier 30 and used as the input of the microcomputer M10.

In addition, when a constant amplification occurs, a high temperature region that cannot be used is generated. In this case, the microcomputer M10 transmits the changed slope to the amplification unit 30 by changing the slope in the gradient converter 10. The high temperature side is input and used.

The above combination of inclinations enables seven combinations of inclinations by the combination of the thirteenth through fifteenth resistors R13, R14, and R15.

In other words, the combination of the slopes represented by the thirteenth to fifteenth resistors R13, R14 and R15 and Rth is Rth / (R14 // R13 + Rth), Rth / (R15 // R13 + Rth), Rth / (R15 // R14 + Rth), Rth / (R15 // R14 // R13 + Rth), Rth / (R13 + Rth), Rth / (R14 + Rth), Rth / (R15 + Rth) .

In addition, the amplification degree can be adjusted by changing the input terminal resistance of the amplifying unit 30 in the eleventh, 17 and 18th resistors R11, R17, and R18 relative to the determined reference resistance. Recovery and output amplification in comparison with the changed slope are amplified to the level of the microcomputer M10 sensing signal. This also allows the fine adjustment of the amplification degree by the combination of the eleventh, 17 and 18 resistors (R11, R17, R18) described above, and the finer combination with the slope combination of the sensor signal is possible.

The input stage resistance of the twentieth OP amplifier IC20 is changed by the eleventh resistor, the seventeenth resistor R17, and the eighteenth resistor R18 of the amplification controller 40 to adjust the amplification degree.

In more detail, the seven inclination combinations are possible by the combination of the thirteenth to fifteenth resistors R13, R14, and R15, thereby enabling fine adjustment of the amplification degree.

In addition, by selectively using the twelfth and thirteen transistors Q12 and Q13 configured in the amplification controller 40, the input level of the microcomputer M10 may be shifted. In other words, since the amplified signal can be increased to a certain level so that the potential level of the microcomputer M10 can be higher than that of the microcomputer M10, the circuit structure can be shifted to the potential level of the microcomputer M10 at different temperature bands. The same A / D resolution can be achieved by making the same slope as possible.

In addition, the combination of the inclination of the sensor signal can be combined in a more detailed manner, and as shown in FIGS. 3 and 4, the same A / D resolution as in the low temperature band is realized in the high temperature band. Therefore, since the resolution level of the microcomputer M10 may be inputted, the control logic quality of the microcomputer M10 may be improved.

By the configuration of the PTC sensor circuit as proposed, the difference in A / D resolution for each temperature band can be minimized.

In addition, there is an advantage that the temperature detection quality can be improved by simultaneously changing the amplification degree and the reference resistance for each temperature band.

In addition, by minimizing the temperature-sensing deviation of each temperature band, the temperature monitoring and temperature control logic design and use quality can be improved.

Claims (4)

Micom; A tilt change unit which adjusts a resistance change rate of the PC element; A buffer unit connected to the gradient converter to prevent distortion of a resistance change rate of the PC element; An amplifier including a predetermined OP amplifier to amplify the resistance change rate; And An amplification adjusting unit configured to enable multistage control by changing an input stage resistance of the OP amplifier configured in the amplifying unit; At least two transistors are included in the gradient change part to change the reference resistance value of the PC sensor input part. The method of claim 1, At least three or more resistors are provided in the inclination change unit to change the reference resistance value of the Pc sensor input unit. The method of claim 1, And the amplification controller further includes at least three resistors for changing the input stage resistance of the OP amplifier configured in the amplifier. The method of claim 3, The amplification control unit includes at least two transistors, And selectively shifting the transistor to a potential level of the microcomputer.

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