An electric heater control circuit and junction box with drying function

Abstract

The present invention discloses an electric heater control circuit with a drying function and a junction box, comprising a plurality of operational amplifiers, a plurality of transistors, a plurality of resistors, and a thermistor; the operational amplifier U1 in the plurality of operational amplifiers is connected with one end of the thermistor RT1, the inverting end of the operational amplifier U3, and one end of the resistor R9, the inverting end is connected with the Vref_1 end, and the output end is connected with the base of the transistor Q1; the operational amplifier U3 inverting end is connected with the Vref_2 end, and the output end is connected with the base of the transistor Q3; the collector of the transistor Q1, the thermistor The other end of RT1 is connected to the power supply, and the emitter is connected to the base of transistor Q2, the collector of transistor Q4, and one end of resistor R4; the collector of transistor Q2 is connected to the base of transistor Q4 and one end of resistor R8, and the emitter is connected to one end of resistor R3, the other end of resistor R4, one end of resistor R5, and Port_1; the collector of transistor Q3 is connected to the other end of resistor R3, and the emitter is connected to the other end of resistor R8; the emitter of transistor Q4, the other end of resistor R5, the other end of resistor R9 and the ground are connected.

Description

Technical Field

[0001] The invention relates to the technical field of junction boxes, and in particular to an electric heater control circuit and a junction box with a drying function. Background Art

[0002] When using a heater, it is necessary to ensure that the terminal is not damp to prevent moisture from causing oxidation and rust of metal parts such as the terminal and wires, which may lead to safety accidents such as short circuits, insulation breakdown, and even burning. At present, the heater junction box is designed with multiple sets of copper bars or terminals for connecting heating tubes, and is equipped with heat dissipation facilities to avoid heat accumulation, and dehumidification is carried out through heat dissipation facilities such as vents, heat sinks and fans to increase the dryness inside the box. These facilities connect the heat sink and the box body through silicone for heat conduction. When the heater is started, the controller will detect the temperature inside the junction box and control the fan operation accordingly to complete the heat dissipation. However, the disadvantage is that after the fan is started, if the temperature inside the box is close to the set value, the fan may start frequently. Summary of the invention

[0003] In view of the above technical problems, the object of the present invention is to provide an electric heater control circuit with a drying function, comprising a plurality of operational amplifiers, a plurality of triodes, a plurality of resistors, and a thermistor;

[0004] The in-phase end of the operational amplifier U1 among the plurality of operational amplifiers is connected to one end of the thermistor RT1, the inverting end of the operational amplifier U3, and one end of the resistor R9, the inverting end is connected to the Vref_1 end, and the output end is connected to the base of the transistor Q1; the in-phase end of the operational amplifier U3 is connected to the Vref_2 end, and the output end is connected to the base of the transistor Q3; the collector of the transistor Q1 and the other end of the thermistor RT1 are connected to the power supply, and the emitter is connected to the base of the transistor Q2, the collector of the transistor Q4, and one end of the resistor R4; the collector of the transistor Q2 is connected to the base of the transistor Q4 and one end of the resistor R8, and the emitter is connected to one end of the resistor R3, the other end of the resistor R4, one end of the resistor R5, and the Port_1 end; the collector of the transistor Q3 is connected to the other end of the resistor R3, and the emitter is connected to the other end of the resistor R8; the emitter of the transistor Q4, the other end of the resistor R5, and the other end of the resistor R9 are connected to the ground end.

[0005] Furthermore, it also includes a number of operational amplifiers, a number of resistors, a thermistor, a digital potentiometer, and a connector;

[0006] The inverting end of the operational amplifier U5 among the plurality of operational amplifiers is connected to the output end of the operational amplifier U6 and one end of the resistor R15, and the output end is connected to the second pin of the digital potentiometer U4; the in-phase end of the operational amplifier U6 is connected to one end of the resistor R14 and one end of the resistor R16, and the inverting end is connected to the other end of the resistor R15 and one end of the resistor R18; the third pin of the digital potentiometer U4 is connected to the first connection end of the connector P1, one end of the resistor R11, and the other end of the resistor R18, and the eighth pin is connected to one end of the thermistor RT2, the other end of the resistor R11, and the collector of the transistor Q3; the second pin of the connector P1 is connected to the The connection end is connected to the power supply, the third connection end is connected to one end of the resistor R2; the other end of the resistor R2 is connected to one end of the resistor R6 and the Vref_1 end; the other end of the resistor R6 is connected to one end of the resistor R10 and the Vref_2 end; the other end of the thermistor RT2 is connected to the other end of the resistor R14 and one end of the resistor R17; the fourth pin of the digital potentiometer U4, the fifth pin of the digital potentiometer U4, the sixth pin of the digital potentiometer U4, the seventh pin of the digital potentiometer U4, the other end of the resistor R10, the other end of the resistor R16, the other end of the resistor R17 and the ground end are connected.

[0007] Furthermore, it also includes an operational amplifier and several resistors;

[0008] The operational amplifier U2 has a common-phase terminal connected to one end of the resistor R1 and one end of the resistor R7, an inverting terminal connected to the Port_1 terminal, and an output terminal connected to the Vout terminal; the other end of the resistor R1 is connected to the power supply; and the other end of the resistor R7 is connected to the ground terminal.

[0009] Further, it also includes capacitors;

[0010] One end of the capacitor C1 is connected to the inverting end of the operational amplifier U3, and the other end is connected to the ground end.

[0011] Furthermore, a number of resistors are included;

[0012] One end of the resistor R12 among the plurality of resistors is connected to the other end of the resistor R3, and the other end is connected to one end of the resistor R13 and the in-phase end of the operational amplifier U5; the other end of the resistor R13 is connected to the ground end.

[0013] Furthermore, the capacitor C1 is an adjustable capacitor.

[0014] Furthermore, the resistor R12 is an adjustable resistor.

[0015] The present invention also provides a junction box of an electric heater control circuit with a drying function, the junction box comprising:

[0016] Shell module: The shell module is made of insulating material to protect the internal components;

[0017] Terminal block module: The terminal block is provided with a plurality of terminals inside, which are used to connect the heating wire and the power wire;

[0018] Heating and drying module: The heating and drying module includes an electric heating tube, which is controlled by an electric heater control circuit with a drying function.

[0019] The beneficial effects of the present invention compared with the prior art are:

[0020] The present invention can effectively reduce the frequent startup problem of the fan when the temperature is close to the set value, and can maintain stable operation by adaptively adjusting the set value when the external environment changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the prior art and the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 A schematic diagram of the circuit structure provided by the present invention. DETAILED DESCRIPTION

[0023] In order to make the objects and advantages of the present invention more clearly understood, the present invention is specifically described below in conjunction with embodiments. It should be understood that the following text is only used to describe one or several specific implementations of the present invention, and does not strictly limit the scope of protection specifically requested by the present invention.

[0024] The invention discloses an electric heater control circuit with a drying function, comprising a plurality of operational amplifiers, a plurality of triodes, a plurality of resistors and a thermistor;

[0025] The in-phase end of the operational amplifier U1 among the plurality of operational amplifiers is connected to one end of the thermistor RT1, the inverting end of the operational amplifier U3, and one end of the resistor R9, the inverting end is connected to the Vref_1 end, and the output end is connected to the base of the transistor Q1; the in-phase end of the operational amplifier U3 is connected to the Vref_2 end, and the output end is connected to the base of the transistor Q3; the collector of the transistor Q1 and the other end of the thermistor RT1 are connected to the power supply, and the emitter is connected to the base of the transistor Q2, the collector of the transistor Q4, and one end of the resistor R4; the collector of the transistor Q2 is connected to the base of the transistor Q4 and one end of the resistor R8, and the emitter is connected to one end of the resistor R3, the other end of the resistor R4, one end of the resistor R5, and the Port_1 end; the collector of the transistor Q3 is connected to the other end of the resistor R3, and the emitter is connected to the other end of the resistor R8; the emitter of the transistor Q4, the other end of the resistor R5, and the other end of the resistor R9 are connected to the ground end.

[0026] Specifically, it also includes several operational amplifiers, several resistors, thermistors, digital potentiometers, and connectors; the inverting end of the operational amplifier U5 in the several operational amplifiers is connected to the output end of the operational amplifier U6 and one end of the resistor R15, and the output end is connected to the second pin of the digital potentiometer U4; the in-phase end of the operational amplifier U6 is connected to one end of the resistor R14 and one end of the resistor R16, and the inverting end is connected to the other end of the resistor R15 and one end of the resistor R18; the third pin of the digital potentiometer U4 is connected to the first connection end of the connector P1, one end of the resistor R11, and the other end of the resistor R18, and the eighth pin is connected to one end of the thermistor RT2, the other end of the resistor R11, and the three-pole The collector of tube Q3 is connected; the second connection end of connector P1 is connected to the power supply, and the third connection end is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R6 and Vref_1; the other end of resistor R6 is connected to one end of resistor R10 and Vref_2; the other end of thermistor RT2 is connected to the other end of resistor R14 and one end of resistor R17; the fourth pin of digital potentiometer U4, the fifth pin of digital potentiometer U4, the sixth pin of digital potentiometer U4, the seventh pin of digital potentiometer U4, the other end of resistor R10, the other end of resistor R16, the other end of resistor R17 and the ground are connected.

[0027] Specifically, it also includes an operational amplifier and several resistors;

[0028] The operational amplifier U2 has a common-phase terminal connected to one end of the resistor R1 and one end of the resistor R7, an inverting terminal connected to the Port_1 terminal, and an output terminal connected to the Vout terminal; the other end of the resistor R1 is connected to the power supply; and the other end of the resistor R7 is connected to the ground terminal.

[0029] Specifically, it also includes capacitance;

[0030] One end of the capacitor C1 is connected to the inverting end of the operational amplifier U3, and the other end is connected to the ground end.

[0031] Specifically, it also includes a number of resistors;

[0032] One end of the resistor R12 among the plurality of resistors is connected to the other end of the resistor R3, and the other end is connected to one end of the resistor R13 and the in-phase end of the operational amplifier U5; the other end of the resistor R13 is connected to the ground end.

[0033] Specifically, the capacitor C1 is an adjustable capacitor.

[0034] Specifically, the resistor R12 is an adjustable resistor.

[0035] To avoid frequent startup of the fan when it is working near the temperature setting value, in one embodiment, the temperature setting value range signal is input to the op amp U1 and the op amp U3 through Vref_1 and Vref_2, the voltage amplitude of Vref_1 is greater than the voltage amplitude of Vref_2, the in-phase terminal of the op amp U1 and the inverting terminal of the op amp U3 are connected in parallel, the thermistor RT1 and the resistor R9 are connected in series to sample the temperature in the junction box and then input to the inverting terminal of the op amp U1 and the in-phase terminal of the op amp U3, and Port_1 feedbacks the fan startup. Or stop signal, when the circuit is powered on, if the temperature is less than the voltage amplitude of Vref_2, the thermistor RT1 is high resistance, the op amp U3 outputs a signal to the base of transistor Q3, transistor Q3 is turned on, the collector power signal is input to the base of transistor Q4 through the emitter of transistor Q3 and resistor R8, transistor Q4 is turned on, the power supply at the resistor R3 end passes through the emitter, base, collector, emitter and ground loop of transistor Q2, and then another way through the emitter and collector of transistor Q2. The input is the voltage drop at the base of transistor Q4 and the emitter of transistor Q2, and the voltage is pulled down and fed back to Port_1. When the temperature rises, the resistance of thermistor RT1 gradually changes from high resistance to low resistance and is divided by resistor R9 and fed back to the same-phase terminal of op amp U1 and the reverse-phase terminal of op amp U3. The voltage at resistor R9 is pulled up, op amp U3 cuts off the output, and transistor Q3 is cut off. In the process, the power supply at resistor R3 forms feedback through the emitter, collector, and base of transistor Q2, and the emitter voltage of transistor Q2 is pulled down. Feedback to Port_1, then op amp U1 outputs a signal to the base of transistor Q1, transistor Q1 is turned on, the collector power supply signal of transistor Q1 is fed back to the base of transistor Q2, the voltage difference between the base and emitter of transistor Q2 is lower than the conduction voltage difference, transistor Q2 is cut off, and the voltage at the connection end of resistor R3 and resistor R4 is pulled up and fed back to Port_1. After the resistance of thermistor RT1 changes from low resistance to high resistance again, op amp U3 outputs a signal again to avoid frequent startup of the fan when working near the temperature value.

[0036] In one embodiment, what is to be achieved is to adaptively adjust the parameters of the set value according to the external temperature to ensure that when the external environment changes, the fan will not be frequently started due to improper set values. Based on the above scheme, resistors R2, R6, and R10 are added to feedback set value signals to Vref_1 and Vref_2. Connector P1 is used to select whether to adopt adaptive according to the changes in the external environment. The three connection ends of connector P1 are selectively connected through a line. When adaptive is selected, the feedback signal of the third pin connection end of resistor R11 and digital potentiometer U4 is input to resistor R2 through the line. Thermistor RT2 and resistor R17 detect the external temperature, and are pulled up and fed back to the same phase end of op amp U6 through resistor R14 and resistor R16. Resistor R11 and digital potentiometer U4 set the reference temperature signal, which is input to op amp U4 through resistor R18. 6 inverting terminal, the output signal of the operational amplifier U6 is first fed back to the inverting terminal of the operational amplifier U6 through the resistor R15 for differentiation, and then input to the inverting terminal of the operational amplifier U5. The non-inverting terminal of the operational amplifier U5 sets the offset reference signal of the operational amplifier U6, and the signal amplitude is greater than the offset voltage when there is no output at the output terminal of the operational amplifier U6. When the external ambient temperature is greater than or less than the reference temperature, the operational amplifier U5 outputs a high level or a low level signal to the second pin of the digital potentiometer U4 to adjust the position of the two ends of the wiper device, that is, the position of the fifth pin from the third pin or the sixth pin. The voltage at the connection end of the third pin of the digital potentiometer U4 and the resistor R11 changes, and then is input to the resistors R2, R6, and R10 through the connector P1 to obtain different Vref_1 and Vref_2 setting value ranges, so that the initial temperature is at a fixed position within the range of Vref_1 and Vref_2 to avoid frequent startup.

[0037] In one embodiment, a capacitor C1 is added to reduce the sensitivity of the thermistor RT, the output state of Port_1 is sampled through the inverting terminal of the operational amplifier U2, Vout outputs a fan control signal, and the resistors R1 and R7 set a reference voltage, the voltage amplitude of which is greater than the emitter-to-base conduction voltage of the transistor Q2.

[0038] The present invention also provides a junction box of an electric heater control circuit with a drying function, the junction box comprising:

[0039] Shell module: The shell module is made of insulating material to protect the internal components;

[0040] Terminal block module: The terminal block is provided with a plurality of terminals inside, which are used to connect the heating wire and the power wire;

[0041] Heating and drying module: The heating and drying module includes an electric heating tube, which is controlled by an electric heater control circuit with a drying function. The junction box has the functions of the above embodiments, and the specific examples are not repeated.

[0042] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations within the meaning and scope of the equivalent elements of the claims be included in the invention. Any marking in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A control circuit for an electric heater junction box with a drying function, characterized in that: Including operational amplifiers U1, U3, U5, U6; transistors Q1, Q2, Q3, Q4; thermistors RT1, RT2; digital potentiometer U4; connector P1; and several resistors; The in-phase end of the operational amplifier U1 is respectively connected to one end of the thermistor RT1, the inverting end of the operational amplifier U3, and one end of the resistor R9, the inverting end is connected to the Vref_1 end, and the output end is connected to the base of the transistor Q1; the in-phase end of the operational amplifier U3 is connected to the Vref_2 end, and the output end is connected to the base of the transistor Q3; the collector of the transistor Q1 and the other end of the thermistor RT1 are connected to the power supply, and the emitter is connected to the base of the transistor Q2, the collector of the transistor Q4, and one end of the resistor R4; the collector of the transistor Q2 is connected to the base of the transistor Q4 and one end of the resistor R8, and the emitter is connected to the power supply. One end of resistor R3, the other end of resistor R4, one end of resistor R5, and the end of Port_1 are connected; the collector of transistor Q3 is connected to the other end of resistor R3, and the emitter is connected to the other end of resistor R8; the emitter of transistor Q4, the other end of resistor R5, the other end of resistor R9, and the ground are connected; the inverting end of op amp U5 is connected to the output end of op amp U6, one end of resistor R15, and the output end is connected to the second pin of digital potentiometer U4; the in-phase end of op amp U6 is connected to one end of resistor R14 and one end of resistor R16, and the inverting end is connected to the other end of resistor R15 and one end of resistor R18; The third pin of the digital potentiometer U4 is connected to the first connection end of the connector P1, one end of the resistor R11, and the other end of the resistor R18, and the eighth pin is connected to one end of the thermistor RT2, the other end of the resistor R11, and the collector of the transistor Q3; the second connection end of the connector P1 is connected to the power supply, and the third connection end is connected to one end of the resistor R2; the other end of the resistor R2 is connected to one end of the resistor R6 and the Vref_1 end; the other end of the resistor R6 is connected to one end of the resistor R10 and the Vref_2 end; the other end of the thermistor RT2 is connected to the other end of the resistor R14 and one end of the resistor R17; the fourth pin of the digital potentiometer U4, the fifth pin of the digital potentiometer U4, the sixth pin of the digital potentiometer U4, the seventh pin of the digital potentiometer U4, the other end of the resistor R10, the other end of the resistor R16, the other end of the resistor R17 and the ground end are connected.

2. The control circuit of the electric heater junction box with drying function according to claim 1, characterized in that: It also includes op amp U2; The operational amplifier U2 has a common-phase terminal connected to one end of the resistor R1 and one end of the resistor R7, an inverting terminal connected to the Port_1 terminal, and an output terminal connected to the Vout terminal; the other end of the resistor R1 is connected to the power supply; and the other end of the resistor R7 is connected to the ground terminal.

3. The control circuit of the electric heater junction box with drying function according to claim 1, characterized in that: Also includes capacitor C1; One end of the capacitor C1 is connected to the inverting end of the operational amplifier U3, and the other end is connected to the ground end.

4. The control circuit of the electric heater junction box with drying function according to claim 1, characterized in that: One end of the resistor R12 among the plurality of resistors is connected to the other end of the resistor R3, and the other end is connected to one end of the resistor R13 and the in-phase end of the operational amplifier U5; the other end of the resistor R13 is connected to the ground end.

5. The control circuit of the electric heater junction box with drying function according to claim 3, characterized in that: The capacitor C1 is an adjustable capacitor.

6. The control circuit of the electric heater junction box with drying function according to claim 4, characterized in that: The resistor R12 is an adjustable resistor.

7. A junction box, comprising the control circuit of the electric heater junction box with drying function according to any one of claims 1 to 6, characterized in that: The junction box comprises: Shell module: The shell module is made of insulating material to protect the internal components; Terminal block module: The junction box is provided with a plurality of terminals inside, which are used to connect the heating wire and the power wire; Heating and drying module: The heating and drying module includes an electric heating tube, which is controlled by an electric heater control circuit with a drying function.

Images