Temperature control circuit for water heater

Abstract

The utility model discloses a temperature control circuit for a water heater, which comprises a temperature difference calculation circuit, a required gas quantity calculation circuit and a gas valve driving circuit, and the required gas quantity calculation circuit comprises a signal conversion sub-circuit, a gas quantity difference sub-circuit and a water outlet temperature detection sub-circuit. The high-precision temperature sensor assembly is adopted, the water temperature of the water outlet pipe is accurately detected in real time, information is fed back, the gas supply amount is adjusted in time, the water temperature is kept within the set range, the water temperature is controlled to be within the set range, the water temperature is controlled to be within the set range, and the water temperature is controlled to be within the set range. And the system has a pure hardware structure, is simple and reliable, and has a wide popularization value.

Description

Technical Field

[0001] This utility model relates to the field of water heater technology, specifically to a temperature control circuit for water heaters. Background Technology

[0002] Traditional gas water heaters use a proportional gas valve for temperature control, which is simple but only adjusts the gas flow. This often results in large temperature fluctuations and slow response times, negatively impacting the user experience. Especially when family members have different water usage habits or experience significant fluctuations in water consumption, the water heater struggles to quickly and accurately adjust to a comfortable temperature, leading to large temperature differences that waste energy and compromise comfort.

[0003] Existing intelligent water temperature control systems can stabilize the water temperature near the set value by adjusting the heat output or heating power through temperature control elements and control algorithms. However, these systems involve multiple components and algorithms, making them relatively complex and increasing the difficulty of maintenance and troubleshooting. Therefore, it is particularly important to develop a constant temperature water heater control system that can effectively avoid large temperature differences and improve energy efficiency. Utility Model Content

[0004] The purpose of this invention is to provide a temperature control circuit for a water heater to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution: a temperature control circuit for a water heater, including a temperature difference calculation circuit, a required gas quantity calculation circuit, and a gas valve drive circuit. The temperature difference calculation circuit inputs the inlet pipe temperature signal detected by the temperature sensing component and the set temperature signal, and calculates the temperature difference output by a subtractor.

[0006] The required gas quantity calculation circuit includes a signal conversion sub-circuit, a gas quantity difference sub-circuit, and an outlet water temperature detection sub-circuit. The signal conversion sub-circuit takes in the temperature difference signal as input, and its output is connected to the input of the gas quantity difference sub-circuit. The output of the gas quantity difference sub-circuit is a control signal. The outlet water temperature detection sub-circuit detects the outlet water pipe temperature signal through a temperature sensing component, and the outlet water pipe temperature signal is connected to the signal conversion sub-circuit.

[0007] The gas valve drive circuit includes a gas valve adjustment direction control sub-circuit and a gas valve adjustment amount drive sub-circuit. The gas valve adjustment direction control sub-circuit inputs the temperature difference signal, and an NPN transistor converts the positive and negative values ​​of the temperature difference signal into high and low level outputs. The gas valve adjustment amount drive sub-circuit inputs the high and low level signals and a control signal. The high and low level signals are applied to a switch, the control signal is applied to the input of a delay circuit, and the output of the delay circuit and the power supply connected to the switch are applied to the gas valve.

[0008] Preferably, the signal conversion sub-circuit includes an optocoupler U1, pin 1 of the optocoupler U1 is connected to the temperature difference, pin 2 of the optocoupler U1 is connected to ground, pin 4 of the optocoupler U1 and one end of resistor R4 are connected to the input of the gas volume difference sub-circuit, the other end of resistor R6 is connected to the power supply +6V, and pin 3 of the optocoupler U1 is connected to ground through resistor R4.

[0009] The gas volume differential circuit includes a resistor R6. One end of the resistor R6 is connected to pin 4 of the optocoupler U1. The other end of the resistor R6 is connected to the upper end of the bidirectional Zener diode VD2, the inverting input of the operational amplifier AR2, and one end of the resistor R9. The non-inverting input of the operational amplifier AR2 is connected to the lower end of the bidirectional Zener diode VD2, one end of the resistor R7, and one end of the grounding resistor R8. The other end of the resistor R7 is connected to the existing gas supply signal. The output of the operational amplifier AR2 and the other end of the resistor R9 output a control signal.

[0010] The outlet water temperature detection sub-circuit includes a resistor R13 and a potentiometer RW2. One end of the resistor R13 is connected to the outlet water pipe temperature signal detected by the temperature sensing component. The other end of the resistor R13 is connected to one end of the resistor R12, one end of the capacitor C5, and the inverting input of the operational amplifier AR3. The non-inverting input of the operational amplifier AR3 is connected to ground through the potentiometer RW2. The output of the operational amplifier AR3, the other end of the resistor R12, and the other end of the capacitor C5 are connected to pin 5 of the optocoupler U1.

[0011] Preferably, the gas valve regulation drive sub-circuit includes chip U2 and bidirectional diode D2. Pins 2 and 6 of chip U2, one end of resistor R12, one end of grounding capacitor CP1, and one end of bidirectional diode D2 are connected to the control signal. The other end of bidirectional diode D2 is connected to one end of resistor R10. The other end of resistor R10 is connected to the gate of MOSFET Q1. The drain of MOSFET Q1 is connected to the common terminal of switch K1. The normally closed contact of switch K1 is connected to the +24V power supply, and the normally open contact of switch K1 is connected to the -24V power supply. The control pin of switch K1 is connected to high and low levels respectively. The source of MOSFET Q1 is connected to two... The negative terminal of transistor D1, pin 1 of gas valve J1, and pin 2 of gas valve J1 are connected to ground. Pin 7 of chip U2 is connected to the other end of resistor R12 and one end of resistor R14, respectively. Pins 4 and 8 of chip U2 are connected to the +5V power supply. Pin 1 of chip U2 is connected to ground. Pin 5 of chip U2 is connected to one end of grounding capacitor C1 and one end of grounding resistor R15. Pin 3 of chip U2 is connected to one end of resistor R16. The other end of resistor R16 is connected to one end of grounding capacitor C9 and the gate of MOSFET Q2, the source of MOSFET Q2 is connected to ground, and the drain of MOSFET Q2 is connected to the positive terminal of diode D1.

[0012] Compared with the prior art, the beneficial effects of this utility model are: by using a high-precision temperature sensor component, the water temperature of the inlet pipe can be detected in real time and accurately, and the difference between the set temperature and the inlet pipe temperature can be calculated quickly. Based on the fact that the water temperature is proportional to the gas supply per unit of gas, the required gas supply can be calculated, that is, the output control signal can be used to precisely control the opening degree and opening and closing time of the gas valve by executing the control signal, which can ensure the stability and accuracy of water temperature control.

[0013] Employing a high-precision temperature sensor assembly, it can detect the water temperature in the water pipe in real time and provide feedback to adjust the gas supply in a timely manner, keeping the water temperature within the set range, thus improving user comfort and satisfaction. With a pure hardware structure, it is simple, reliable, and has broad application value. Attached Figure Description

[0014] Figure 1 This is the circuit schematic diagram of this utility model;

[0015] Figure 2 This is a schematic diagram of the structure of this utility model. Detailed Implementation

[0016] For the purposes of this utility model, the foregoing and other technical contents, features and effects are described in conjunction with the appendix below. Figures 1 to 2 The detailed description of the embodiments will make this clear. All structural details mentioned in the following embodiments are based on the accompanying drawings.

[0017] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings.

[0018] Example 1: A temperature control circuit for a water heater includes a temperature difference calculation circuit, a required gas quantity calculation circuit, and a gas valve drive circuit. The temperature difference calculation circuit inputs the inlet pipe temperature signal detected by the temperature sensing component and the set temperature signal. The temperature sensing component can be a 50K copper-plated nickel high-precision temperature sensor, which has high accuracy and the copper-plated nickel shell has good corrosion resistance and thermal conductivity. Alternatively, an M8 threaded NTC temperature sensor can be used, which is easy to install and remove. The detected inlet pipe temperature is converted into an electrical signal, and the temperature difference is calculated by a subtractor. This allows for the rapid calculation of the difference between the set temperature and the inlet pipe temperature, providing a reliable basis for subsequent gas quantity calculation.

[0019] The required gas quantity calculation circuit includes a signal conversion sub-circuit, a gas quantity difference sub-circuit, and a water outlet temperature detection sub-circuit. The signal conversion sub-circuit takes in the temperature difference signal. Since the water temperature is proportional to the gas supply per unit of gas, the gas supply signal is linearly converted through the electric coupler U1 and resistors R4 and R5. The converted signal is used for calculation by the gas quantity difference sub-circuit. Specifically, it is applied to the inverting input of operational amplifier AR2 through resistor R6, and the non-inverting input of operational amplifier AR2 is connected to the existing gas supply signal. The differential amplifier calculates the control signal for adjusting the required gas supply and calculates the gas quantity difference required to reach the set temperature (i.e., the amount of gas that needs to be increased or decreased). This is used as a control signal to adjust the opening degree or opening and closing time of the gas valve.

[0020] The outlet water temperature detection sub-circuit uses a high-precision temperature sensor component, which can detect the actual water temperature of the outlet pipe in real time and accurately, and convert it into an electrical signal. The electrical signal is amplified and conditioned, and then applied to pin 5 of the optocoupler U1. The sensitivity of the optocoupler U1 is adjusted, and the magnitude of the linear conversion gas supply signal is adjusted, so as to realize the function of feeding back the information and adjusting the gas supply in a timely manner.

[0021] The gas valve drive circuit includes a gas valve adjustment direction control subcircuit and a gas valve adjustment amount drive subcircuit. The gas valve adjustment direction control subcircuit inputs the temperature difference signal, and an NPN transistor converts the positive and negative values ​​of the temperature difference signal into high and low level outputs, thereby determining whether the gas valve is adjusted to increase in the positive direction or decrease in the negative direction. The gas valve adjustment amount drive subcircuit inputs the high and low level control signals. The high and low levels are applied to the control pin (IN pin) of switch K1. When the level is low, switch K1 does not operate, and +24V is applied to the drain of MOSFET Q1, and the gate of MOSFET Q1 is open. The control signal is connected through resistor R10. A bidirectional diode D2 is connected in parallel between the gate of MOSFET Q1 and resistor R10. To allow for a certain temperature difference and avoid frequent adjustments, the gas valve is connected to the power supply when adjustment is required. This further determines whether the gas valve needs adjustment. The control signal is used as the input of the delay circuit to generate a certain duration of voltage level, which is applied to the gate of MOSFET Q2 to control the conduction duration of MOSFET Q2. This is used to precisely adjust the opening degree of the gas valve. In this way, by executing the control signal to precisely control the opening degree and opening and closing time of the gas valve, the stability and accuracy of water temperature control can be ensured.

[0022] This design ensures that the water heater can automatically adjust the gas supply according to the user's set temperature, improving user comfort and satisfaction. It is a pure hardware structure that is simple, reliable, and has broad application value.

[0023] In Example 2, based on Example 1, the temperature difference calculation circuit inputs the inlet pipe temperature signal and the set temperature signal detected by the temperature sensing component. The temperature sensing component can be a 50K copper-plated nickel high-precision temperature sensor, which has high accuracy and a copper-plated nickel shell with good corrosion resistance and thermal conductivity. Alternatively, an M8 threaded NTC temperature sensor can be used, as its M8 threaded package facilitates installation and disassembly. The detected inlet pipe temperature is converted into an electrical signal, referred to as the inlet pipe temperature signal, which is applied to the inverting input of operational amplifier AR1 via resistor R1. The non-inverting input of operational amplifier AR1 is connected to the electrical signal corresponding to the set temperature, referred to as the set temperature signal, which is controlled by resistor R2 and potentiometer R... W1 provides voltage divider, and the user adjusts the set temperature signal by rotating the potentiometer. Operational amplifier AR1 and resistors R1-R3 form a subtractor, with resistor R3 serving as the feedback resistor. The subtractor calculates the temperature difference output, including resistor R1. One end of resistor R1 is input to the inlet pipe temperature signal detected by the temperature sensing component, and the other end of resistor R1 is connected to the inverting input of operational amplifier AR1. The non-inverting input of operational amplifier AR1 is connected to one end of resistor R2, one end of resistor R3, and one end of ground potentiometer RW1, respectively. The other end of resistor R2 is connected to the +5V power supply. The output of operational amplifier AR1, the other end of resistor R3, and the upper end of bidirectional Zener diode VD1 output the temperature difference.

[0024] In Example 3, based on Example 1, the signal conversion sub-circuit inputs the temperature difference signal. Since the water temperature is proportional to the gas supply per unit of gas, the gas supply signal is linearly converted through the electrocoupler U1 and resistors R4 and R5. The output of the signal conversion sub-circuit is connected to the input of the gas volume difference sub-circuit, including the optocoupler U1. Pin 1 of the optocoupler U1 is connected to the temperature difference, pin 2 of the optocoupler U1 is connected to ground, pin 4 of the optocoupler U1 and one end of resistor R4 are connected to the input of the gas volume difference sub-circuit, the other end of resistor R6 is connected to the +6V power supply, and pin 3 of the optocoupler U1 is connected to ground through resistor R4.

[0025] The gas supply differential circuit inputs the gas supply signal, which is applied to the inverting input of operational amplifier AR2 through resistor R6. The non-inverting input of operational amplifier AR2 is connected to the existing gas supply signal (the gas supply signal corresponding to the existing valve opening). Resistor R6-resistor R9, transient suppression diode VD2, and operational amplifier AR2 constitute a differential amplifier to calculate the control signal for adjusting the required gas supply. Resistor R6 is connected to pin 4 of optocoupler U1, and the other end of resistor R6 is connected to the upper end of bidirectional Zener diode VD2, the inverting input of operational amplifier AR2, and one end of resistor R9. The non-inverting input of operational amplifier AR2 is connected to the lower end of bidirectional Zener diode VD2, one end of resistor R7, and one end of grounding resistor R8. The other end of resistor R7 is connected to the existing gas supply signal. The output of operational amplifier AR2 and the other end of resistor R9 output the control signal.

[0026] The outlet water temperature detection subcircuit uses a high-precision temperature sensor component, which can detect the actual water temperature of the outlet pipe in real time and accurately, and convert it into an electrical signal. The electrical signal is amplified and conditioned by operational amplifier AR3, resistors R12 and R13, and capacitor C5. The conditioned signal is then applied to pin 5 of optocoupler U1 to adjust the sensitivity of optocoupler U1 and adjust the magnitude of the linear conversion gas supply signal, thereby realizing the function of feeding back this information and adjusting the gas supply in a timely manner. The subcircuit includes resistor R13 and potentiometer RW2. One end of resistor R13 is connected to the outlet water temperature signal detected by the temperature sensor component. The other end of resistor R13 is connected to one end of resistor R12, one end of capacitor C5, and the inverting input of operational amplifier AR3. The non-inverting input of operational amplifier AR3 is connected to ground through potentiometer RW2. The output of operational amplifier AR3, the other end of resistor R12, and the other end of capacitor C5 are connected to pin 5 of optocoupler U1.

[0027] In Example 4, based on Example 1, the gas valve adjustment direction control sub-circuit inputs the temperature difference signal. When the temperature difference signal is positive, the Zener diode Z1 breaks down and the NPN transistor Q3 conducts, outputting a low level. When the temperature difference signal is negative, the Zener diode Z1 breaks down and the NPN transistor Q3 does not work, outputting a high level. This converts the positive and negative values ​​of the temperature difference signal into high and low level outputs. The high and low level gas valve adjustment direction includes the Zener diode Z1. The negative terminal of the Zener diode Z1 is connected to the temperature difference, and the positive terminal of the Zener diode Z1 is connected to the base of the transistor Q3. The collector of the transistor Q3 is connected to the +5V power supply, and the emitter of the transistor Q3 is connected to the positive terminal of the diode D2. The negative terminal of the diode D2 and one end of the grounding resistor R17 output high and low levels.

[0028] Example 5, based on Example 1, the gas valve adjustment drive sub-circuit inputs the high and low level control signals. The high and low levels are applied to the control pin (IN pin) of switch K1. When the level is low, switch K1 does not operate, and +24V is applied to the drain of MOSFET Q1. The gate of MOSFET Q1 is connected to the control signal through resistor R10. A bidirectional diode D2 is connected in parallel between the gate of MOSFET Q1 and resistor R10. To allow for a certain temperature difference and avoid frequent adjustments, when adjustment is needed, the gas valve is connected to the power supply. The control signal serves as the input of the delay circuit, generating a level of a certain duration, which is applied to the gate of MOSFET Q2 to control the conduction duration of MOSFET Q2. In this way, by executing the control signal, the opening degree and opening and closing time of the gas valve can be precisely controlled, ensuring the stability and accuracy of water temperature control. This includes chip U2, bidirectional diode D2, pins 2 and 6 of chip U2, one end of resistor R12, one end of grounding capacitor CP1, and one end of bidirectional diode D2 connected to the control signal. The other end of diode D2 is connected to one end of resistor R10, and the other end of resistor R10 is connected to the gate of MOSFET Q1. The drain of MOSFET Q1 is connected to the common terminal of switch K1. The normally closed contact of switch K1 is connected to the +24V power supply, and the normally open contact of switch K1 is connected to the -24V power supply. The control pin of switch K1 is connected to high and low levels. The source of MOSFET Q1 is connected to the cathode of diode D1 and pin 1 of gas valve J1. Pin 2 of gas valve J1 is connected to ground. Pin 7 of chip U2 is connected to... Connect the other end of resistor R12 and one end of resistor R14. Connect pins 4 and 8 of chip U2 to the +5V power supply. Connect pin 1 of chip U2 to ground. Connect pin 5 of chip U2 to one end of grounding capacitor C1 and one end of grounding resistor R15. Connect pin 3 of chip U2 to one end of resistor R16. Connect the other end of resistor R16 to one end of grounding capacitor C9 and the gate of MOSFET Q2. Connect the source of MOSFET Q2 to ground. Connect the drain of MOSFET Q2 to the positive terminal of diode D1.

[0029] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A temperature control circuit for a water heater, comprising a temperature difference calculation circuit, a required gas amount calculation circuit, a gas valve drive circuit, characterized in that: The temperature difference calculation circuit takes the inlet pipe temperature signal and the set temperature signal detected by the temperature sensing component as input, and calculates the temperature difference by the subtractor and outputs it. The required gas quantity calculation circuit includes a signal conversion sub-circuit, a gas quantity difference sub-circuit, and a water outlet temperature detection sub-circuit. The signal conversion sub-circuit is input to the temperature difference and outputs. The output of the signal conversion sub-circuit is connected to the input of the gas quantity difference sub-circuit, and the output of the gas quantity difference sub-circuit is a control signal. The water outlet temperature detection sub-circuit detects the water outlet pipe temperature signal through a temperature sensing component, and the water outlet pipe temperature signal is connected to the signal conversion sub-circuit. The gas valve drive circuit includes a gas valve adjustment direction control sub-circuit and a gas valve adjustment amount drive sub-circuit. The gas valve adjustment direction control sub-circuit takes the temperature difference output as input and uses an NPN transistor to convert the positive and negative of the temperature difference output into a high or low level output. The gas valve adjustment amount drive sub-circuit takes the high or low level and a control signal as input. The high or low level is applied to the switch, the control signal is applied to the input of the delay circuit, and the output of the delay circuit and the power supply connected to the switch are applied to the gas valve.

2. A temperature control circuit for a water heater as claimed in claim 1 wherein: The temperature difference calculation circuit includes a resistor R1. One end of the resistor R1 is input to the water inlet pipe temperature signal detected by the temperature sensing component. The other end of the resistor R1 is connected to the inverting input of the operational amplifier AR1. The non-inverting input of the operational amplifier AR1 is connected to one end of the resistor R2, one end of the resistor R3, and one end of the ground potentiometer RW1, respectively. The other end of the resistor R2 is connected to the +5V power supply. The output of the operational amplifier AR1, the other end of the resistor R3, and the upper end of the bidirectional Zener diode VD1 output the temperature difference.

3. The temperature control circuit for a water heater of claim 1, wherein: The signal conversion sub-circuit includes an optocoupler U1. Pin 1 of the optocoupler U1 is connected to the temperature difference, pin 2 of the optocoupler U1 is connected to ground, pin 4 of the optocoupler U1 and one end of resistor R4 are connected to the input of the gas volume difference sub-circuit, the other end of resistor R6 is connected to the power supply +6V, and pin 3 of the optocoupler U1 is connected to ground through resistor R4. The gas volume differential circuit includes a resistor R6. One end of the resistor R6 is connected to pin 4 of the optocoupler U1. The other end of the resistor R6 is connected to the upper end of the bidirectional Zener diode VD2, the inverting input of the operational amplifier AR2, and one end of the resistor R9. The non-inverting input of the operational amplifier AR2 is connected to the lower end of the bidirectional Zener diode VD2, one end of the resistor R7, and one end of the grounding resistor R8. The other end of the resistor R7 is connected to the existing gas supply signal. The output of the operational amplifier AR2 and the other end of the resistor R9 output a control signal. The outlet water temperature detection sub-circuit includes a resistor R13 and a potentiometer RW2. One end of the resistor R13 is connected to the outlet water pipe temperature signal detected by the temperature sensing component. The other end of the resistor R13 is connected to one end of the resistor R12, one end of the capacitor C5, and the inverting input of the operational amplifier AR3. The non-inverting input of the operational amplifier AR3 is connected to ground through the potentiometer RW2. The output of the operational amplifier AR3, the other end of the resistor R12, and the other end of the capacitor C5 are connected to pin 5 of the optocoupler U1.

4. A temperature control circuit for a water heater according to claim 1, characterized in that: The gas valve adjustment direction control sub-circuit includes a Zener diode Z1. The negative terminal of the Zener diode Z1 is connected to the temperature difference, the positive terminal of the Zener diode Z1 is connected to the base of the transistor Q3, the collector of the transistor Q3 is connected to the +5V power supply, and the emitter of the transistor Q3 is connected to the positive terminal of the diode D2. The negative terminal of the diode D2 and one end of the grounding resistor R17 output high and low levels.

5. The temperature control circuit for a water heater of claim 1, wherein: The gas valve regulation drive sub-circuit includes chip U2, bidirectional diode D2, pins 2 and 6 of chip U2, one end of resistor R12, one end of grounding capacitor CP1, and one end of bidirectional diode D2 are connected to the control signal. The other end of bidirectional diode D2 is connected to one end of resistor R10, and the other end of resistor R10 is connected to the gate of MOSFET Q1. The drain of MOSFET Q1 is connected to the common terminal of switch K1, and the normally closed contact of switch K1 is connected to the +24V power supply. The normally open contact of switch K1 is connected to the -24V power supply. The control pin of switch K1 is connected to the high and low levels. The source of MOSFET Q1 is connected to the negative terminal of diode D1 and pin 1 of gas valve J1. Pin 2 of gas valve J1 is connected to ground. Pin 7 of chip U2 is connected to the other end of resistor R12 and one end of resistor R14. Pins 4 and 8 of chip U2 are connected to the +5V power supply. Pin 1 of chip U2 is connected to ground. Pin 5 of chip U2 is connected to one end of grounding capacitor C1 and one end of grounding resistor R15. Pin 3 of chip U2 is connected to one end of resistor R16. The other end of resistor R16 is connected to one end of grounding capacitor C9 and the gate of MOSFET Q2. The source of MOSFET Q2 is connected to ground. The drain of MOSFET Q2 is connected to the positive terminal of diode D1.

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