WO2010054592A1

WO2010054592A1 - Control circuit for electronic temperature probe

Info

Publication number: WO2010054592A1
Application number: PCT/CN2009/074913
Authority: WO
Inventors: 郑荣兴
Original assignee: 漳州灿坤实业有限公司
Priority date: 2008-11-15
Filing date: 2009-11-12
Publication date: 2010-05-20
Also published as: CN201319149Y

Abstract

A control circuit for an electronic temperature probe includes a triangular wave generation circuit (20), a temperature signal processing circuit (30), a control signal output circuit (40), and a driving circuit for an electric heating tube (50). The triangular wave generation circuit (20) is used to generate triangular wave. The temperature signal processing circuit (30) includes a temperature regulating circuit for regulating the control temperature of the temperature probe, a temperature detecting circuit for detecting the temperature, and an operational amplifier (U1A) which is connected to the temperature regulating circuit and the temperature detecting circuit and compares to generate a temperature signal level. The control signal output circuit (40) is connected to the operational amplifiers (U1D,U1A) of the triangular wave generation circuit (20) and the temperature signal processing circuit (30) and is used to compare the triangular wave level with the temperature signal level to generate a control signal level. The driving circuit for an electric heating tube (50) is connected to the control signal output circuit (40) and is used to define a heating operation and heating time period.

Description

Instruction manual

Title of Invention: An electronic temperature sensing rod control circuit

[1] The present invention relates to an electronic temperature sensing rod control circuit, and more particularly to an electronic temperature sensing rod control circuit for a household appliance.

Background technique

[2] The temperature sensing bars that are seen on the market are divided into two categories, one is a mechanical temperature sensing rod, and the other is an electronic temperature sensing rod.

. Whether it is a mechanical temperature sensing rod or an electronic temperature sensing rod, their working methods are: based on the temperature point to be controlled, the detection temperature is continuously heated once the temperature is lower than the temperature point, and the detection temperature is higher than the temperature point. Then stop heating. Since the heating is directly or continuously stopped regardless of the difference between the detected temperature and the temperature point, when the difference is small, continuous heating or direct stop of heating, waste of power, overheating, low control precision, temperature The overshoot is too large and the fluctuation is too large.

Summary of the invention

[3] The present invention provides an electronic temperature sensing rod control circuit that overcomes the shortcomings of the background temperature sensing rods having low control precision, excessive temperature overshoot, and excessive fluctuation.

[4] The technical solution adopted by the present invention to solve its technical problems is:

[5] An electronic temperature sensing rod control circuit comprising a triangular wave generating circuit, a temperature signal processing circuit, a control signal output circuit and an electric combustion tube driving circuit. The triangular wave generating circuit is for generating a triangular wave. The temperature signal processing circuit includes a temperature adjustment circuit for adjusting the temperature of the temperature sensing rod, a temperature detection circuit for detecting the temperature, and a connection temperature adjustment circuit and the temperature detection circuit and comparing to generate a temperature signal level Op amp. The control signal output circuit is connected to the triangular wave generating circuit and the op amp of the temperature signal processing circuit for comparing the triangular wave level and the temperature signal level to generate a control signal level. The electric combustion tube driving circuit is connected to the control signal output circuit for controlling whether the heating and the heating time are controlled by the control signal level.

[6] The triangular wave generating circuit includes an op amp, resistors R1, R2, R3, R4 and a capacitor C1, and the resistors R1, R2 and R3 cooperate to form an amplitude adjusting circuit for adjusting the amplitude of the upper and lower limits of the triangular wave. The resistor R4 and the capacitor C1 cooperate to form a period adjusting circuit for adjusting the period of the triangular wave. [7] The temperature signal processing circuit includes an op amp, resistors R7, R8, VR, NTC, and a diode.

D2, the temperature regulating circuit includes resistors R7, R8 and VR, and the temperature detecting circuit comprises NTC and diode D2

[8] The control signal output circuit comprises an op amp, resistors R5, R9, and the two input terminals of the op amp are connected to the op amp of the triangular wave generating circuit and the temperature signal processing circuit through resistors R5 and R9, respectively.

[9] The electric heating tube driving circuit includes R6, R13, triode Ql, Q2, relay Kl, diode D3

The drain of the transistor Q1 is electrically connected to the control signal output circuit through a resistor R6. The C pole of the Q1 is electrically connected to the relay K1, the drain of the Q1 is electrically connected to the C pole of the Q2, and the B pole of the Q2 is electrically connected. One end of the resistor R13, the E pole of the Q2 is grounded, wherein when the R6 and R13 are at a high level, the transistors Q1 and Q2 are turned on, the relay K1 is attracted, and the electric heating tube starts heating.

[10] Further, the present invention further includes: a power supply circuit for supplying a power supply Vcc of the operational amplifier and an operating power supply of the electric heating tube driving circuit, which is electrically connected to the triangular wave generating circuit, the temperature signal processing circuit, the control signal output circuit, and the electric combustion tube Drive circuit.

[11] Further, the present invention further includes: a protection circuit for preventing the temperature sensing rod from being properly temperature controlled by the NTC open circuit, which is connected to the temperature signal processing circuit and the electric combustion tube driving circuit.

[12] The protection circuit includes resistors R10, Rl l, R12 and an op amp, an input end of the op amp is electrically connected to the temperature signal processing circuit through a resistor R10, and the other input terminal is electrically connected One end of the resistor R12 and the end of the resistor R11, the other end of the resistor R12 is grounded, and the other end of the resistor R11 is connected to the power supply circuit; the output end of the op amp is electrically connected to the B pole of the electric heating tube driving circuit transistor Q2, wherein After the NTC is open, the output of the op amp outputs a low level, which causes Q2 to be turned off.

[13] The technical solution is compared with the background art: since the control signal level generated by the control signal output circuit is obtained after comparing the triangular wave level and the temperature signal level, the control signal level controls the electric combustion tube to be heated, the electric heating tube The ratio between the working time and the non-working time decreases as the temperature signal level increases, and increases as the temperature signal level decreases. When the temperature is lower than the set position, the electric heating tube works. The longer the interval, the better the temperature can be approached to the set gear. Therefore, the temperature control method is asymptotic, which avoids overshoot, stabilizes the temperature more quickly, and controls the temperature more accurately and stably. A protection circuit is provided in the circuit to make the product more reliable. The invention can be used for heating temperature control of household appliances such as electric hot pot, rice cooker and electric oven. DRAWINGS

[14] The invention will now be further described with reference to the drawings and embodiments.

1 is a circuit diagram of an electronic temperature sensing rod control circuit of a preferred embodiment.

detailed description

[16] Please refer to FIG. 1, an electronic temperature sensing rod control circuit, which includes a power supply circuit 10, a triangular wave generating circuit 20, a temperature signal processing circuit 30, a control signal output circuit 40, an electric heating tube driving circuit 50, and a protection circuit. 60.

[17] The power supply circuit 10 is mainly used to supply the power supply Vcc of the operational amplifier and the operating power of the relay of the electric heating tube driving circuit 50. The power circuit 10 has a xenon lamp POWER11 and a xenon lamp Heaterl2, and the xenon lamp POW ER11 and the xenon lamp HeaterU are used to indicate the working state of the electronic temperature sensing bar. Among them, after power-on, the neon light PO WER11 is always bright, the power is off, the neon light POWER11 is off; the electric heating tube is heated, the xenon lamp Heaterl2 is on, the electric heating tube stops heating, the xenon lamp HeaterU is off.

[18] The triangular wave generating circuit 20 is for generating a triangular wave, which includes an op amp U1D and peripheral element resistors R1, R2, R3, R4 and a capacitor Cl. The U1D is available in U1 324 with a positive input, a negative input and an output. The positive input terminal is electrically connected to the resistor R1 - terminal and the resistor R 2 - terminal, and the negative input terminal is electrically connected to one end of the capacitor C1. The other end of the resistor R1 is electrically connected to the power supply circuit 10 to obtain a voltage Vcc; the other end of the resistor R2 is electrically connected to the other end of the resistor C1 and grounded; the resistor R3 is connected in series between the positive input terminal and the output terminal; the resistor R4 is connected in series at the negative input terminal and the output terminal. between. Resistor R1 is set to 100K, resistor R2 is set to 100K, resistor R3 is set to 100K, resistor R4 is set to 220K, and capacitor C1 is set to 100U and 25V. The resistors R1, R2 and R3 cooperate to form an amplitude adjusting circuit for adjusting the amplitude of the upper and lower limits of the triangular wave, and the resistor R4 and the capacitor C1 cooperate to form a period adjusting circuit for adjusting the period of the triangular wave.

[19] The temperature signal processing circuit 30 includes an op amp U1A and peripheral component resistors R7, R8, R14, VR, NTC and a diode D2. The U1A is available in UTC324 with a positive input, a negative input and an output. The resistors R7, VR, and R8 are sequentially connected in series, and the other end of the resistor R7 is electrically connected to the power circuit 10 to obtain a voltage Vcc; the NTC terminal is electrically connected to the outer end of the R7, and the other end of the NTC is electrically connected to the positive terminal of the diode D2. The negative terminal of the diode D2 is electrically connected to the positive input terminal of the op amp U1A and the VR, and the external terminal connected to the VR can adjust the VR; the negative input terminal of the op amp U1A is electrically connected to the output terminal; the R14-end Grounded, the other end is electrically connected to the negative terminal of diode D2. The resistor R7 is 10K, the electric Resistor R8 is set to 2K, the resistor R14 is set to 1Μ, the MAX of the resistor VR is set to 20Κ, and the resistor NTC is set to 200′4Ko. The resistors R7, R8 and VR form a thermostat circuit, and the R8 can adjust the electrons. The temperature sensor has the highest control temperature position. The R7 can reduce the ON angle of the VR and make the VR temperature adjustment angle larger. When the VR is adjusted to the uppermost level, its signal level is higher than the highest level of the triangle wave. . The NTC and the diode D 2 constitute a temperature detecting circuit for detecting the temperature.

[20] Control signal output circuit 40, including op amp U1C and peripheral components, the U1C product model UTC324 has a positive input, a negative input and an output. The positive input terminal is electrically connected to one end of the resistor R5, and the other end of the R5 is connected to the other end of the R4 of the triangular wave generating circuit 20; the negative input terminal is electrically connected to one end of the resistor R9, and the other end of the R9 is connected to the temperature signal processing circuit 30. The output. The R5 is set to 10K and the R9 is set to 10Κ. The amplifier U1C compares the triangular wave level signal generated by the amplifier U1D of the triangular wave generating circuit 20, and the temperature signal level generated by the amplifier U1A of the temperature signal processing circuit 30; the output level of the U1C output terminal The level is a control signal level, and the level is a determining condition for heating or not the electric heating tube of the electric heating tube drive circuit 50.

[21] When the triangular wave level is higher than the temperature signal level, the U1C outputs a high level; when the triangular wave level is lower than the temperature signal level, the U1C outputs a low level. When the temperature signal level is less than 1/3VCC吋, the U1C outputs a high level, so that the electric heating tube starts to heat; when the temperature signal is greater than 2/3VCC吋, the U1C outputs a low level, so that the electric heating tube stops heating; Among them, the ratio of the working temperature between the electric heating tube and the non-working time decreases as the temperature signal level increases, and increases as the temperature signal level decreases. That is to say, when the temperature is closer to the set temperature position, the electric heating tube works less; when the temperature is lower than the set position, the electric heating tube works longer. In this way, the temperature can be gradually approached to the set gear position, and the overshoot can be avoided, so that the temperature control of the product is stable and the fluctuation is small.

[22] The electric heating tube driving circuit 50 includes resistors R6, R13, transistors Ql, Q2, relay Kl, and diode D3. The R6 is 10K, and the drain of the Q1 is electrically connected to the output of the U1C through the resistor R6. The C pole of the Q1 is electrically connected to the relay K1, and the drain of the Q1 is electrically connected to the C pole of the Q2. The gate of the Q2 is electrically connected to one end of the resistor R13, and the drain of the Q2 is grounded. When the R6 and R13 are at a high level, the transistors Q1 and Q2 are turned on, the relay K1 is pulled in, and the electric heating tube starts to heat up.

[23] Protection circuit 60, including resistors R10, Rl l, R12, R13, op amp U1B, R10, Rl l, Rl 2, R13, U1B constitute NTC open circuit protection circuit, to avoid electronic temperature sensing rod due to NTC open circuit Not working properly Temperature control. The product model U1B is UTC324, which has a positive input, a negative input and an output. The resistor R10 is 10K, the resistor R11 is 240K, the resistor R12 is 10K, and the resistor R13 is 10K. The output end of the amplifier U1B is electrically connected to the other end of the resistor R13. The positive input terminal is electrically connected to the other end of the R14 through a resistor R10. The negative input terminal is electrically connected to the resistor R12-terminal and the resistor R11. One end, the other end of the resistor R12 is grounded, the other end of the resistor R11 is connected to the power supply circuit 10 to obtain the voltage VCCo. When the NTC is short-circuited, the control circuit itself can control the electric heating tube to not heat; when the NTC works normally, the diode D2 is turned on. The normal voltage drop, D2 positive will have a voltage greater than 0.7ZU; When NT C is open, the resistor R14 pulls down 吋D2 to get the positive voltage close to zero, R14 chooses a larger value, does not affect the normal temperature signal level , R11 and R12 resistor divider is about 0.5V; When NTC is open, U1B outputs low level, so that Q2 is cut off, the electric heating tube can not be heated normally.

Industrial applicability

[24] An electronic temperature sensing rod control circuit of the present invention, wherein a control signal level generated by the control signal output circuit is obtained after comparing a triangular wave level and a temperature signal level, the control signal level controlling the electric combustion tube heating, The ratio of the working and non-working time of the electric heating tube decreases as the temperature signal level increases, and increases as the temperature signal level decreases. When the temperature is lower than the set position, the electric heating tube The longer the working time, the better the temperature can be approached to the set gear. Therefore, the temperature control method is asymptotic, avoiding overshoot, making the temperature stable more quickly, and the temperature control is more accurate and stable.

Claims

Claim

[Claim 1] An electronic temperature sensing rod control circuit, which is characterized in that it comprises:

a triangular wave generating circuit for generating a triangular wave;

a temperature signal processing circuit, comprising: a temperature adjustment circuit for adjusting the temperature of the temperature sensing rod, a temperature detection circuit for detecting the temperature, and a connection temperature adjustment circuit and the temperature detection circuit and comparing to generate a temperature signal level Op amp

a control signal output circuit that compares a triangular wave level and a temperature signal level to generate a control signal level, which is connected to an operational amplifier of the triangular wave generating circuit and the temperature signal processing circuit;

The control signal output circuit is connected to the control circuit output circuit by controlling whether the control signal level is heated or not.

[Claim 2] The electronic temperature sensing rod control circuit according to claim 1, wherein: the triangular wave generating circuit comprises an op amp, resistors R1, R2, R3, R4 and a capacitor CI, the resistor R1, R2 and R3 cooperate to form an amplitude adjustment circuit for adjusting the amplitude of the upper and lower limits of the triangular wave. The resistor R4 and the capacitor C1 cooperate to form a period adjustment circuit for adjusting the period of the triangular wave.

[Claim 3] The electronic temperature sensing rod control circuit according to claim 1, wherein: the temperature signal processing circuit comprises an op amp, resistors R7, R8, VR, NTC and diode D2, the temperature adjustment The circuit includes resistors R7, R8, and VR, and the temperature detection circuit includes NT C and diode D2.

[Claim 4] The electronic temperature sensing rod control circuit according to claim 1, wherein: the control signal output circuit comprises an op amp, resistors R5, R9, and the two input ends of the op amp pass respectively R5 and R9 connect the triangular wave generating circuit and the op amp of the temperature signal processing circuit.

[Claim 5] The electronic temperature sensing rod control circuit according to claim 1, wherein: the electric heating tube driving circuit comprises R6, R13, triode Q1, Q2, relay K1, diode D3, and B pole of the Q1. The control signal output circuit is electrically connected through a resistor R6, and the C pole of the Q1 is electrically connected to the relay K1, and the drain of the Q1 is electrically connected to the C pole of the Q2, and the Q2 of the Q2 The pole is electrically connected to one end of the resistor R13, and the E pole of the Q2 is grounded, wherein, when the R6, R

13 is a high level 吋, the transistors Ql, Q2 are turned on, the relay K1 is sucked, and the electric heating tube starts heating.

[Claim 6] The electronic temperature sensing rod control circuit according to claim 5, further comprising:

A power supply circuit for supplying a power supply Vcc of an operational amplifier and an operating power supply of the electric heating tube driving circuit, which is electrically connected to a triangular wave generating circuit, a temperature signal processing circuit, a control signal output circuit, and an electric combustion tube driving circuit.

[Claim 7] The electronic temperature sensing rod control circuit according to claim 6, further comprising:

A protection circuit for preventing the temperature sensing rod from being properly temperature controlled by the NTC open circuit, which is connected to the temperature signal processing circuit and the electric combustion tube driving circuit.

[Claim 8] The electronic temperature sensing rod control circuit according to claim 7, wherein: the protection circuit comprises resistors R10, Rl l, R12 and an op amp, and an input end of the op amp passes through the resistor R10 is electrically connected to the temperature signal processing circuit, and the other input terminal is electrically connected to the resistor R12-terminal and the resistor R11-terminal, the other end of the resistor R12 is grounded, and the other end of the resistor R11 is connected to the power supply circuit; The output end of the device is electrically connected to the B pole of the electric heating tube driving circuit transistor Q2, wherein when the NTC is open, the output end of the op amp outputs a low level, so that Q2 is turned off.