CN108398972B

CN108398972B - Temperature controller based on silicon controlled rectifier

Info

Publication number: CN108398972B
Application number: CN201810459109.XA
Authority: CN
Inventors: 高玉琴
Original assignee: Individual
Current assignee: Individual
Priority date: 2018-05-15
Filing date: 2018-05-15
Publication date: 2023-08-22
Anticipated expiration: 2038-05-15
Also published as: CN108398972A

Abstract

A temperature controller based on a silicon controlled rectifier comprises a temperature detection circuit consisting of a comparator A1, triodes T1 and T2, a thermistor RT, a variable resistor R1, resistors R2-R8 and an electrolytic capacitor C1; the square wave generator circuit consists of an operational amplifier A2, resistors R9-R10, triodes T3 and T4, resistors R11-R12, capacitors C2-C3 and a time base integrated circuit IC1; the power amplifying circuit consists of an optical coupler GE1 and a bidirectional silicon controlled rectifier KG 1; the temperature detection circuit compares the heating temperature with a set value, when the heating temperature is equal to the set value, the voltage of the electrolytic capacitor C1 is kept at a proper value, the voltage of the electrolytic capacitor C1 controls the duty ratio of square waves of the square wave generator to adjust the heating power of the bidirectional thyristor KG1, and when the heating temperature is equal to the set value, the heating capacity is close to the heat dissipation capacity, so that the fluctuation range of the control temperature is greatly reduced, and the constant temperature is realized.

Description

Temperature controller based on silicon controlled rectifier

Technical Field

The invention relates to a temperature controller, which consists of electronic components.

Background

The temperature controller generally comprises a thermistor for sensing temperature and a comparator, wherein the comparator compares a temperature signal with a set value, and when the temperature signal is smaller than the set value, the comparator outputs a heating signal to electrify the electric heater; when the temperature signal is equal to or greater than a set value, the comparator outputs a heating stop signal to power off the electric heater; the disadvantage is that the heater is not stable (i.e. no continuous power for maintaining the temperature), the fluctuation range of the controlled temperature is large, and the constant temperature performance is poor.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a temperature controller based on a silicon controlled rectifier, which has small temperature control fluctuation and small error between the controlled temperature and the set temperature.

The technical scheme of the invention is that the temperature controller based on the controllable silicon comprises a temperature detection circuit, a square wave generator circuit and a power amplification circuit; the temperature detection circuit is characterized by comprising a thermistor RT with a positive temperature coefficient, a comparator A1, a triode T1 and a triode T2, wherein one end of the thermistor RT is connected with the non-inverting input end of the comparator A1, the other end of the thermistor RT is grounded, the non-inverting input end of the comparator A1 is connected with a regulated power supply V+ through a variable resistor R1, the inverting input end of the comparator A1 is connected with the regulated power supply V+ through a resistor R2, and the inverting input end of the comparator A1 is grounded through a resistor R3; the output end of the comparator A1 is connected with the base electrode of the triode T1 through a resistor R5, the base electrode of the triode T1 is connected with a regulated power supply V+ through a resistor R4, the emitter electrode of the triode T1 is connected with the regulated power supply V+, and the collector electrode of the triode T1 is connected with the anode of the electrolytic capacitor C1 through a resistor R8, and the cathode of the electrolytic capacitor C1 is grounded; the output end of the comparator A1 is connected with the base electrode of the triode T2 through a resistor R6, the base electrode of the triode T2 is grounded through a resistor R7, the emitter electrode of the triode T2 is grounded, and the collector electrode of the triode T2 is connected with the collector electrode of the triode T1; the stabilized voltage power supply V+ is connected with one power supply input end of the comparator A1, and the stabilized voltage power supply V-is connected with the other power supply input end of the comparator A1;

the square wave generator circuit comprises an operational amplifier A2, a triode T3 and a time base integrated circuit IC1, wherein the non-inverting input end of the operational amplifier A2 is connected with the positive electrode of an electrolytic capacitor C1, the inverting input end of the operational amplifier A2 is grounded through a resistor R9, and a resistor R10 is connected between the inverting input end and the output end of the operational amplifier A2;

the base electrode of the triode T3 is connected with the output end of the operational amplifier A2, the emitter electrode of the triode T3 is connected with the regulated power supply V+ through a resistor R11, the collector electrode of the triode T3 is connected with one end of a capacitor C2, the other end of the capacitor C2 is grounded, one end of the capacitor C2 is connected with a pin 2 and a pin 6 of the time base integrated circuit IC1, a pin 7 of the time base integrated circuit IC1 is connected with the emitter electrode of the triode T3, the base electrode of the triode T4 is connected with the output end of the operational amplifier A2, the collector electrode of the triode T4 is connected with the collector electrode of the triode T3, the emitter electrode of the triode T4 is connected with a pin 7 of the time base integrated circuit IC1 through a resistor R12, and the pin 3 of the time base integrated circuit IC1 outputs square wave signals; pin 4 and pin 8 of the time base integrated circuit IC1 are connected with a regulated power supply V+, pin 1 of the time base integrated circuit IC1 is grounded, and pin 5 of the time base integrated circuit IC1 is grounded through a capacitor C3;

the power amplifying circuit comprises an optical coupler GE1 and a bidirectional thyristor KG1, wherein a pin 3 of the time base integrated circuit IC1 is connected with the anode of a light emitting diode of the optical coupler GE1, the cathode of the light emitting diode of the optical coupler GE1 is grounded through a resistor R13, one end of a photoelectric trigger diode of the optical coupler GE1 is connected with a control electrode of the bidirectional thyristor, the other end of the photoelectric trigger diode is connected with a first electrode of the bidirectional thyristor through a resistor R14, the first electrode of the bidirectional thyristor is connected with one end of an electric heater RL, the other end of the electric heater RL is connected with a phase line a of mains supply, and a second electrode of the bidirectional thyristor is connected with a zero line 0 of the mains supply.

The temperature control process comprises the following steps: when the temperature is lower than a set value, the resistance of the thermistor is low, the voltage of the non-inverting input end of the comparator A1 is smaller than the voltage of the inverting input end, the voltage of the output end of the comparator A1 is negative, the triode T1 is conducted to charge the electrolytic capacitor C1, the voltage of the electrolytic capacitor C1 is increased or is at the highest value, the duty ratio of the square wave generator is increased or is at the highest value, and the power of the electric heater is increased or is the greatest; when the temperature is higher than a set value, the resistance of the thermistor is increased, the voltage of the non-inverting input end of the comparator A1 is larger than the voltage of the inverting input end, the voltage of the output end of the comparator A1 is positive, the triode T1 is conducted to discharge the electrolytic capacitor C1, the voltage of the electrolytic capacitor C1 is reduced, the duty ratio of the square wave generator is reduced, and the power of the electric heater is reduced; when the voltage of the non-inverting input end of the comparator A1 is equal to the voltage of the inverting input end (namely, the temperature is equal to a set value), the voltage of the output end of the comparator A1 is 0, the triode T1 and the triode T2 are cut off, the voltage on the electrolytic capacitor C1 is kept unchanged, the duty ratio of the square wave generator is kept unchanged, and the power of the electric heater is also unchanged; the method is characterized in that when the heating temperature is close to the set temperature, the voltage of the electrolytic capacitor C1 is kept at a proper value, the square wave generator correspondingly forms a corresponding duty ratio, the bidirectional thyristor outputs a maintenance power, the heating capacity is close to the heat dissipation capacity, and thus the fluctuation range of the controlled temperature is greatly reduced, and the constant temperature is realized.

Drawings

Fig. 1 is a schematic circuit diagram of the present invention.

Detailed Description

Specific embodiments of the present invention will now be described with reference to the accompanying drawings.

A temperature controller based on a silicon controlled rectifier comprises a temperature detection circuit, a square wave generator circuit and a power amplification circuit.

The temperature detection circuit comprises a comparator A1, a PNP triode T1, an NPN triode T2, a positive temperature coefficient thermistor RT, a variable resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8 and an electrolytic capacitor C1, wherein the variable resistor R1 and the thermistor RT convert temperature change into voltage, the voltage division value is the voltage u1 of the non-inverting input end of the comparator A1, the resistor R2 and the resistor R3 are used for setting temperature, the voltage division value is the voltage u2 of the inverting input end of the comparator A1, and the resistor R2 can be replaced by a potentiometer so as to facilitate the adjustment of a temperature set value.

When the voltage u1 at the non-inverting input terminal of the comparator A1 is smaller than the voltage u2 at the inverting input terminal of the comparator A1, the comparator A1 outputs negative voltage, and the triode T1 charges the capacitor C1; when the voltage u1 of the non-inverting input end of the comparator A1 is larger than the voltage u2 of the inverting input end of the comparator A1, the comparator A1 outputs positive voltage, and the triode T2 discharges the capacitor C1; when the voltage u1 at the non-inverting input terminal of the comparator A1 is equal to the voltage u2 at the inverting input terminal of the comparator A1, the comparator A1 outputs 0, and the capacitor C1 stops charging and discharging.

The resistor R4 and the resistor R5 are used to define the base voltage of the transistor T1, the resistor R6 and the resistor R7 are used to define the base voltage of the transistor T2, and the transistor T1 and the transistor T2 are turned off when the output of the comparator A1 is 0.

The square wave generator circuit comprises an operational amplifier A2, a resistor R9, a resistor R10, a PNP type triode T3, an NPN type triode T4, a resistor R11, a resistor R12, a capacitor C2, a capacitor C3 and a time base integrated circuit IC1 with the model of NE 555;

the operational amplifier A2, the resistor R9 and the resistor R10 form an in-phase amplifier, amplify the voltage of the electrolytic capacitor C1 and provide base voltages for the triode T3 and the triode T4; the triode T3, the triode T4, the resistor R11, the resistor R12, the capacitor C2 and the time base integrated circuit IC1 form a square wave generator with controllable duty ratio, and when the input voltage signal at the non-inverting input end of the operational amplifier A2 changes, the duty ratio of the square wave generator also changes.

The duty cycle is defined as duty cycle=tg/(tg+td), where tg is the duration of the high level output by the square wave generator and td is the duration of the low level output by the square wave generator.

The oscillation principle of the square wave generator is that the base electrodes of a triode T3 and a triode T4 are connected with the output end of an operational amplifier A2, the operational amplifier A2 is arranged to output certain voltage, the triode T3 and a resistor R11 charge a capacitor C2 in a constant current manner, and the triode T4 and a resistor R12 discharge the capacitor C2 in a constant current manner; in the charging process, when the voltage on the capacitor C2 rises to two thirds VDD (VDD is the voltage value of the regulated power supply V+), the pin 3 of the time base integrated circuit IC1 is changed from high level to low level, the pin 7 of the time base integrated circuit IC1 is conducted to ground, the triode T3 stops charging the capacitor C2, and the triode T4 starts discharging the capacitor C2; in the discharging process, when the voltage drop VDD on the capacitor C2 is one third, the pin 3 of the time base integrated circuit IC1 is changed from low level to high level, the pin 7 of the time base integrated circuit IC1 is turned off to ground, the triode T4 stops discharging the capacitor C2, and the triode T3 starts charging the capacitor C2; the oscillation is repeatedly formed, the pin 3 of the time base integrated circuit IC1 outputs a square wave signal, and the oscillation period of the square wave signal is related to the resistor R11, the resistor R12 and the capacitor C2.

The principle of controllable duty ratio is that when the output voltage of the operational amplifier A2 increases, the collector current of the triode T3 decreases, the charging speed of the capacitor C2 is slow, and the duration of the high level output by the square wave generator increases; and the collector current of transistor T4 increases, the discharge rate of capacitor C2 increases, and the duration of the high level output by the square wave generator decreases, and vice versa.

The power amplifying circuit comprises an optocoupler GE1, a bidirectional thyristor KG1, a resistor R13, a resistor R14 and an electric heater RL, when a pin 3 of the base integrated circuit IC1 is at a high level, a light emitting diode of the optocoupler GE1 passes current, a photoelectric trigger diode of the optocoupler GE1 is conducted, the bidirectional thyristor KG1 is conducted, the electric heater RL is electrified, when the pin 3 of the base integrated circuit IC1 is at a low level, the light emitting diode of the optocoupler GE1 does not pass current, the photoelectric trigger diode of the optocoupler GE1 is cut off, and the electric heater RL is powered off.

It should be noted that, the triac KG1 may be triggered at a non-zero crossing, that is, the rising edge of the square wave generator does not occur at the zero crossing of the mains supply, the on-time of the triac KG1 is longer than the high-level time of the square wave, the on-time error is within 5 ms, which is about 1/2 half-waves of the mains supply, the off-time of the triac KG1 is shorter than the low-level time of the square wave, the off-time error is also within 5 ms, and in order to reduce the error, the oscillation period of the square wave may be selected between 0.5 seconds and 2 seconds, the longer the oscillation period of the square wave is, the smaller the on-time error and the off-time error are, and the preferred oscillation period of the square wave is 1 second.

As an improvement, an electronic switch K1 is connected between the collector of the triode T3 and the capacitor C2, one end of the electronic switch K1 is connected with the collector of the triode T3, the other end of the electronic switch K1 is connected with one end of the capacitor C2, the control electrode of the electronic switch K1 is connected with a synchronous pulse ut, the resistance values of the resistor R11 and the resistor R12 are properly reduced, and the oscillation period of the square wave signal can be 100 times of the period of the synchronous pulse ut;

the electronic switch is turned on when the synchronization pulse ut is high and turned off when the synchronization pulse ut is low. Therefore, only when the synchronous pulse ut arrives, the capacitor C2 can be charged or discharged, so that the conduction time of the bidirectional triode thyristor KG1 is equal to the high-level time of the square wave, the cut-off time of the bidirectional triode thyristor KG1 is equal to the low-level time of the square wave, and the conduction error and the cut-off error of the bidirectional triode thyristor KG1 are eliminated; and the bidirectional thyristor KG1 is triggered by zero crossing, so that the harmonic current of the electric heater is reduced.

The forming circuit of the synchronous pulse ut is that a primary coil of the transformer B1 is connected with a mains supply, one end of a secondary coil of the transformer B1 is connected with an anode of a diode D1, a cathode of the diode D1 is connected with a base electrode of a triode T5 through a resistor R15, a collector electrode of the triode T5 is connected with a stabilized voltage supply V+ through a resistor R17, an emitter electrode of the triode T5 is grounded, the other end of the secondary coil of the transformer B1 is connected with an anode of a diode D4, a cathode of the diode D4 is connected with a base electrode of the triode T5 through a resistor R16, a center tap of the secondary coil of the transformer B1 is grounded, and the collector electrode of the triode T5 outputs the synchronous pulse ut. The collector of the triode T5 is connected with the control electrode of the electronic switch K1, and the synchronous pulse appears when the waveform of the mains supply crosses zero.

The circuit of the voltage-stabilizing power supply V+ is that one end of a secondary coil of the transformer B1 is connected with an anode of the diode D2, a cathode of the diode D2 is grounded through the electrolytic capacitor C4, the cathode of the diode D2 is connected with a pin 1 of the voltage-stabilizing integrated circuit IC2, a pin 2 of the voltage-stabilizing integrated circuit IC2 is grounded, a pin 3 of the voltage-stabilizing integrated circuit IC2 is grounded through the electrolytic capacitor C6, the model of the voltage-stabilizing integrated circuit IC2 is 7812V, the output voltage of the pin 3 of the voltage-stabilizing integrated circuit IC2 is 12V, and a center tap of the secondary coil of the transformer B1 is grounded.

The circuit of the voltage-stabilizing power supply V-is that the other end of the secondary coil of the transformer B1 is connected with the cathode of the diode D3, the anode of the diode D3 is grounded through the electrolytic capacitor C5, the anode of the diode D3 is connected with the pin 2 of the voltage-stabilizing integrated circuit IC3, the pin 1 of the voltage-stabilizing integrated circuit IC3 is grounded, the pin 3 of the voltage-stabilizing integrated circuit IC3 is grounded through the electrolytic capacitor C7, the model of the voltage-stabilizing integrated circuit IC3 is 7912, and the output voltage of the pin 3 of the voltage-stabilizing integrated circuit IC3 is minus 12V.

Claims

1. A temperature controller based on a silicon controlled rectifier comprises a temperature detection circuit, a square wave generator circuit and a power amplification circuit; the temperature detection circuit is characterized by comprising a thermistor RT with a positive temperature coefficient, a comparator A1, a triode T1 and a triode T2, wherein one end of the thermistor RT is connected with the non-inverting input end of the comparator A1, the other end of the thermistor RT is grounded, the non-inverting input end of the comparator A1 is connected with a regulated power supply V+ through a variable resistor R1, the inverting input end of the comparator A1 is connected with the regulated power supply V+ through a resistor R2, and the inverting input end of the comparator A1 is grounded through a resistor R3; the output end of the comparator A1 is connected with the base electrode of the triode T1 through a resistor R5, the base electrode of the triode T1 is connected with a regulated power supply V+ through a resistor R4, the emitter electrode of the triode T1 is connected with the regulated power supply V+, and the collector electrode of the triode T1 is connected with the anode of the electrolytic capacitor C1 through a resistor R8, and the cathode of the electrolytic capacitor C1 is grounded; the output end of the comparator A1 is connected with the base electrode of the triode T2 through a resistor R6, the base electrode of the triode T2 is grounded through a resistor R7, the emitter electrode of the triode T2 is grounded, and the collector electrode of the triode T2 is connected with the collector electrode of the triode T1; the stabilized voltage power supply V+ is connected with one power supply input end of the comparator A1, and the stabilized voltage power supply V-is connected with the other power supply input end of the comparator A1; the square wave generator circuit comprises an operational amplifier A2, a triode T3 and a time base integrated circuit IC1, wherein the non-inverting input end of the operational amplifier A2 is connected with the positive electrode of an electrolytic capacitor C1, the inverting input end of the operational amplifier A2 is grounded through a resistor R9, and a resistor R10 is connected between the inverting input end and the output end of the operational amplifier A2; the base electrode of the triode T3 is connected with the output end of the operational amplifier A2, the emitter electrode of the triode T3 is connected with the regulated power supply V+ through a resistor R11, the collector electrode of the triode T3 is connected with one end of a capacitor C2, the other end of the capacitor C2 is grounded, one end of the capacitor C2 is connected with a pin 2 and a pin 6 of the time base integrated circuit IC1, a pin 7 of the time base integrated circuit IC1 is connected with the emitter electrode of the triode T3, the base electrode of the triode T4 is connected with the output end of the operational amplifier A2, the collector electrode of the triode T4 is connected with the collector electrode of the triode T3, the emitter electrode of the triode T4 is connected with a pin 7 of the time base integrated circuit IC1 through a resistor R12, and the pin 3 of the time base integrated circuit IC1 outputs square wave signals; pin 4 and pin 8 of the time base integrated circuit IC1 are connected with a regulated power supply V+, pin 1 of the time base integrated circuit IC1 is grounded, and pin 5 of the time base integrated circuit IC1 is grounded through a capacitor C3; the power amplifying circuit comprises an optical coupler GE1 and a bidirectional thyristor KG1, wherein a pin 3 of a time base integrated circuit IC1 is connected with the anode of a light emitting diode of the optical coupler GE1, the cathode of the light emitting diode of the optical coupler GE1 is grounded through a resistor R13, one end of a photoelectric trigger diode of the optical coupler GE1 is connected with a control electrode of the bidirectional thyristor, the other end of the photoelectric trigger diode is connected with a first electrode of the bidirectional thyristor through a resistor R14, the first electrode of the bidirectional thyristor is connected with one end of an electric heater RL, the other end of the electric heater RL is connected with a phase line a of mains supply, and a second electrode of the bidirectional thyristor is connected with a zero line 0 of the mains supply;

the oscillation period of the square wave signal is 1 second;

in the square wave generator circuit, an electronic switch K1 is connected between a collector electrode of a triode T3 and a capacitor C2, and a control electrode of the electronic switch K1 is connected with a synchronous pulse ut; the oscillation period of the square wave signal is 100 times of the period of the synchronous pulse ut; the forming circuit of the synchronous pulse ut is that a primary coil of a transformer B1 is connected with a mains supply, one end of a secondary coil of the transformer B1 is connected with an anode of a diode D1, a cathode of the diode D1 is connected with a base electrode of a triode T5 through a resistor R15, a collector electrode of the triode T5 is connected with a stabilized voltage supply V+ through a resistor R17, an emitter electrode of the triode T5 is grounded, the other end of the secondary coil of the transformer B1 is connected with an anode of a diode D4, a cathode of the diode D4 is connected with a base electrode of the triode T5 through a resistor R16, a center tap of the secondary coil of the transformer B1 is grounded, the collector electrode of the triode T5 outputs the synchronous pulse ut, and the collector electrode of the triode T5 is connected with a control electrode of an electronic switch K1.