Residual water quantity detection circuit and steam box

Abstract

The utility model discloses a residual water quantity detection circuit and a steam box, and the residual water quantity detection circuit comprises a heating pipe which is used for heating water; the power switch unit is used for controlling the working state of the heating pipe; the power control unit is used for adjusting the heating power of the heating pipe; the current detection unit is used for detecting the current flowing through the heating pipe, and the current is associated with the residual water amount; wherein the heating tube, the power switch unit, the power control unit and the current detection unit are connected in series. According to the scheme, the residual water amount can be accurately detected, the detection logic is easy to realize, the number of devices in the steam box can be reduced, and the complexity of a circuit structure is reduced.

Description

Technical Field

[0001] This disclosure relates to the field of household appliance technology, specifically to a residual water detection circuit and a steam oven. Background Technology

[0002] A steam oven is a cooking device that uses a steam heating plate (also called a heating plate, evaporation plate, or heating element) to convert water into high-temperature steam for steam cooking food. During operation, it is necessary to monitor the remaining water level on the steam heating plate to prevent it from drying out and endangering the user's life and property.

[0003] Currently, steam ovens commonly use dedicated sensors, such as humidity sensors and water level sensors, to detect the residual water on the steam heating plate. This increases the number of components in the steam oven, and the sensors need to be connected to the steam oven's operating circuitry, which undoubtedly increases the complexity of the circuit structure. Utility Model Content

[0004] One object of the present disclosure is to provide an improved residual water detection circuit.

[0005] Therefore, this disclosure provides a residual water detection circuit, including: a heating element for heating water; a power switch unit for controlling the working state of the heating element; a power control unit for adjusting the heating power of the heating element; and a current detection unit for detecting the current flowing through the heating element, wherein the current is associated with the residual water volume; wherein the heating element, the power switch unit, the power control unit, and the current detection unit are connected in series.

[0006] Therefore, by monitoring the current in the circuit containing the heating element, the heating power of the heating element can be accurately and directly obtained. Based on this heating power, the remaining water volume in the area affected by the heating element can be estimated, eliminating the need for a dedicated sensor to detect residual water. Furthermore, eliminating the sensor reduces the number of components that need to be integrated into the device with the residual water detection circuit, and all sensor-related connection circuits can be eliminated, thus reducing the complexity of the circuit structure. The device may include a steam oven.

[0007] Optionally, the remaining water detection circuit further includes a control unit, coupled to the power switch unit, the power control unit, and the current detection unit, respectively. The control unit receives feedback signals from the current detection unit and sends control signals to the power switch unit and / or the power control unit based on the feedback signals. The feedback signals include the current detection result. Thus, the control unit obtains the remaining water level based on the feedback result from the current detection unit, and then rationally controls the operating state of at least one of the power switch unit and the power control unit based on the remaining water level to ensure that the heating process is controllable and meets expectations. Taking a steam oven as an example, the heating process can be the steam oven's cooking program.

[0008] Optionally, the current detection unit includes: a wire segment connected in series between the heating tube and the power control unit; a current transformer for sensing the current flowing through the wire segment; and a current-to-voltage conversion circuit connected in parallel with the current transformer for converting the current to a voltage domain for characterization. This allows the heating power of the heating tube to be obtained without disrupting the original circuit structure of the device. Furthermore, the current transformer can be placed at any position in the series circuit, making full use of the available space inside the device.

[0009] Optionally, the current detection unit further includes an amplification bias circuit coupled to the current-to-voltage conversion circuit. The amplification bias circuit amplifies the output value of the current-to-voltage conversion circuit and biases it to a positive value. This allows the sampled detection signal to be biased and further amplified for subsequent analysis.

[0010] Optionally, the amplification bias circuit includes: a bias unit coupled to the current-to-voltage conversion circuit, the bias unit being used to bias the output value of the current-to-voltage conversion circuit to a positive value; and a power amplifier unit coupled to the bias unit, the power amplifier unit being used to amplify the output value of the bias unit. Considering that the power supply for the heating element is usually AC, and the current induced by the corresponding current transformer is also AC, the AC voltage obtained by the current-to-voltage conversion circuit is not conducive to measurement. Therefore, the bias unit is used to boost the overall voltage waveform to above 0V for easier measurement. Furthermore, the voltage value output by the current-to-voltage conversion circuit is relatively small, so the power amplifier unit amplifies the voltage value by a factor of two for subsequent analysis.

[0011] Optionally, the biasing unit includes a first resistor and a second resistor, which are respectively coupled to the two ends of the current-to-voltage conversion circuit. Thus, voltage bias is achieved by connecting resistors to the two ends of the current-to-voltage conversion circuit.

[0012] Optionally, the power amplifier unit includes a power amplifier, and a feedback resistor and a filter capacitor connected in parallel with the power amplifier. The power amplifier amplifies the signal; the feedback resistor improves the stability and anti-interference performance of the power supply; and the filter capacitor provides a smooth and clean DC voltage to the power amplifier, stores energy, and reduces distortion of the power amplifier output signal.

[0013] Optionally, the voltage across the conductor segment is much greater than the voltage across the current transformer. This allows for voltage isolation between the heating element and the control unit, and the current waveform in the series circuit can be proportionally converted to a waveform acceptable to the control unit via the current detection unit.

[0014] Optionally, the current-to-voltage conversion circuit includes a first sampling resistor and a second sampling resistor connected in parallel. The design of multiple sampling resistors allows for the use of combinations of resistors with common resistance values ​​to obtain sampling resistors with resistance values ​​suitable for this embodiment. Furthermore, if the current transformer is open-circuited, high voltage will directly act on the control unit and damage the chip; therefore, multiple sampling resistors can be designed to be redundant, ensuring the safety of the control circuit.

[0015] Another object of the embodiments of this disclosure is to provide an improved steam oven.

[0016] Therefore, this disclosure provides a steam oven, including: a steam heating plate for holding water; and the aforementioned remaining water detection circuit for detecting the remaining water in the steam heating plate.

[0017] Therefore, during the process of heating water onto the steam heating plate by the heating element, the heating power of the heating element is accurately and directly obtained by monitoring the current in the circuit containing the heating element through the remaining water detection circuit. Based on this heating power, the remaining water volume in the steam heating plate can be estimated, eliminating the need for a dedicated sensor on the steam heating plate to detect residual water. Furthermore, eliminating the sensor reduces the number of components that need to be integrated into the steam chamber, and all sensor-related connection circuits in the circuit structure can be eliminated, thereby reducing the complexity of the circuit structure. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for detecting residual water according to an embodiment of this disclosure;

[0019] Figure 2 This is a functional block diagram of a steam oven according to an embodiment of the present disclosure;

[0020] Figure 3 This is a logic block diagram of a residual water detection circuit according to an embodiment of the present disclosure;

[0021] Figure 4 yes Figure 3A circuit diagram of a variation of the power amplifier unit;

[0022] In the attached image:

[0023] 11-Steam heating plate; 12-Heating tube; 13-Monitoring module; 14-Control module; 15-Switch module; 16-Adjustment module; 17-Temperature control switch; 21-Power switch unit; 22-Power control unit; 23-Current detection unit; 231-Current transformer; 232-Wire segment; 233-Current-voltage conversion circuit; 234-Bias unit; 235-Power amplifier unit; R1-First sampling resistor; R2-Second sampling resistor; R3-First resistor; R4-Second resistor; R5, R6-Feedback resistors; 236-Power amplifier; C1-First filter capacitor; C2-Second filter capacitor; C3-Capacitor; R7-Third resistor; R8-Fourth resistor; 24-Control unit. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings.

[0025] Figure 1 This is a flowchart of a method for detecting residual water volume according to an embodiment of this disclosure.

[0026] This implementation scheme can be applied to scenarios involving the detection of remaining water in a steam heating plate. The steam heating plate can be installed in a steam oven or other electrical equipment that requires steam during operation. The following section will use a steam oven as an example to elaborate on this implementation scheme.

[0027] This implementation scheme can be executed by a control module integrated into the steam oven. The control module can be a microcontroller within the steam oven, or it can be a dedicated control unit within the steam oven for executing this implementation scheme.

[0028] Specifically, refer to Figure 1 The remaining water detection method described in this embodiment may include the following steps:

[0029] S101, monitor the current and / or voltage flowing through the heating tube to obtain the heating power of the heating tube;

[0030] S102, at least based on the initial water volume of the target area and the heating power, the remaining water volume of the target area is calculated, and the heating tube is used to heat the target area.

[0031] More specifically, the target area can be a steam heating plate. The heat generated when the heating element is energized can radiate to the steam heating plate, thus converting the water contained within it into steam. Furthermore, the heating power of the heating element can be adjusted by regulating the current flowing through it. For example, a higher current results in a higher heating power and consequently, more heat is generated.

[0032] Furthermore, the heating power of the heating element is related to the heat generated by the heating element, and thus to the amount of water evaporation in the target area per unit time. Therefore, the amount of water evaporation in the target area from time t0 to time t1 can be determined based on the heating power, and the remaining water volume in the target area at time t1 can be determined by combining the initial water volume in the target area at time t0.

[0033] Furthermore, time t0 can be the start time of the program, where the program can be used to control the operation of the heating element. For example, if the steam oven executes a cooking program and accordingly controls the heating element to be powered on to generate heat, the water volume in the steam heating plate at the start of the cooking program can be obtained as the initial water volume.

[0034] Alternatively, time t0 can be any time during program execution. For example, this implementation scheme can be executed periodically, in which case the remaining water volume determined in the previous execution of S101 and S102 can be used as the initial water volume for the next execution of this implementation scheme.

[0035] In some embodiments, a current sensor can be used to detect the current flowing through the heating element. The current sensor can be a galvanometer, a current transformer, a Hall effect sensor, etc. In S101, the heating power of the heating element can be equal to the product of the detected current value and the operating voltage of the heating element. The operating voltage of the heating element can be equivalent to the power supply voltage of the steam oven, such as 220 volts (V) of AC mains.

[0036] Furthermore, the current flowing through the heating element can be alternating current (AC). Accordingly, the heating power can be calculated based on the effective value of the AC current and the operating voltage of the heating element. The effective value of the AC current can be the projected area of ​​the AC waveform over time. Therefore, in scenarios where the steam oven is powered by AC, considering the fluctuating characteristics of AC current, the heating power is calculated using the effective value of the AC current combined with the operating voltage, ensuring the accuracy of the heating power calculation.

[0037] In one variation, a voltage sensor can be used to detect the voltage across the heating element, and a current sensor can be used to detect the current flowing through the heating element. For example, the two ends of the heating element can be directly or indirectly coupled to the live wire and neutral wire of the power supply, respectively. Voltage sensors can be coupled to the live wire and neutral wire to accurately measure the actual voltage of the heating element. Therefore, a more accurate heating power can be calculated based on the detected current and voltage values.

[0038] In one variation, only a voltage sensor can be used to detect the voltage of the heating element, while the current flowing through the heating element can be obtained in other ways; this implementation does not impose any restrictions on this. Thus, the heating power of the heating element can also be calculated.

[0039] Therefore, by monitoring the current and / or voltage in the circuit containing the heating element, the heating power of the heating element can be accurately and directly obtained, and the remaining water volume in the target area can be estimated based on the heating power. Using this implementation scheme, residual water volume detection can be achieved without the need for an additional dedicated water level sensor in the target area. Furthermore, the detection logic of this implementation scheme is easy to implement, and when applied to a steam oven, it can reduce the number of components in the steam oven and lower the complexity of the circuit structure.

[0040] In one specific implementation, S102 may include the steps of: calculating the amount of water evaporation in the target area within a preset time period based on the heating power; and calculating the remaining amount of water in the target area based on the initial water volume and the amount of water evaporation.

[0041] Specifically, there is a correlation between the amount of water evaporating per unit time in the target area and the heating power of the heating element. For example, the amount of water evaporating in a steam heating pan under the influence of heat from the heating element has an algorithmic proportional relationship with the heating power of the heating element. In practical applications, the specific algorithmic proportional relationship between water evaporation and heating power can be determined through experiments and / or theoretical simulations.

[0042] Furthermore, based on the current value detected by S101, the heating power output by the heating tube within a preset time period can be calculated, thereby determining the generated heat.

[0043] Furthermore, by subtracting the amount of water evaporation from the initial water volume in the target area, the remaining water volume in the target area after a preset time period can be obtained.

[0044] Taking a steam oven as an example, assuming the preset time is from when the heating element starts working to the present, the initial water volume can be the amount of water injected into the steam heating plate when the steam oven starts its cooking program. By detecting the current flowing through the heating element since it was energized, and combining this with the operating voltage of the heating element, the heating power of the heating element can be calculated. Furthermore, based on the correlation between heating power and water evaporation, the amount of water evaporated from the steam heating plate since the steam oven started its cooking program can be determined. Then, subtracting the amount of water evaporated from the initial water volume gives the remaining water volume in the steam heating plate since the steam oven started operating.

[0045] Furthermore, the amount of water injected into the steam heating plate when the steam oven starts the cooking program can be determined based on the duration the steam oven's water pump is turned on.

[0046] The specific value of the preset duration can be set as needed, and this embodiment does not impose any restrictions on it.

[0047] In one variation, the amount of water evaporation in a target area within a preset time period can be calculated based on the heating power and the temperature of the target area. Specifically, the temperature of the target area also affects the rate of water evaporation. Therefore, based on the heating power, initial water volume, and temperature, the remaining water volume can be accurately calculated, enabling precise detection of the residual water in the target area. For example, a temperature sensor can be placed near the target area to collect its temperature.

[0048] In one specific implementation, the current of the heating element can be converted to the voltage domain for monitoring. For example, a sampling resistor can be set up, coupled to a current sensor, to convert the current value detected by the current sensor into a voltage value. Thus, by converting the current, which is inconvenient to measure directly, into voltage for measurement and characterization, it is beneficial to calculate an accurate heating power value.

[0049] In one specific implementation, the steam oven can add water to the steam heating plate in batches multiple times during operation. Correspondingly, the monitoring of the current and / or voltage flowing through the heating tube in S101 can be continuously performed during the operation of the heating tube. Thus, the remaining water level in the steam heating plate can be continuously monitored throughout the entire operation of the steam oven, so as to respond promptly when the remaining water level approaches zero.

[0050] Furthermore, the monitored current and / or voltage values ​​can also be used to determine whether dry burning has occurred in the target area (e.g., the steam heating plate). For example, if the detected current value is 0 (represented by a constant voltage of 1.42V in the voltage domain), it indicates that the remaining water in the target area is zero, indicating dry burning; if the detected current value is non-zero (represented by a 50Hz sine curve fluctuating between 1V and 2V in the voltage domain), it indicates that there is still residual water in the target area, and dry burning has not occurred. Thus, continuous monitoring ensures the continuity of dry burning monitoring. When this implementation scheme is applied to the detection of remaining water in the steam heating plate of a steam oven, the target area is the steam heating plate, and continuous dry burning monitoring improves the safety of steam oven use.

[0051] In one specific implementation, the action of calculating the remaining water volume in the target area in S102 is performed at least within the last preset duration of the heating element's operation. When the heating element initially operates, the remaining water volume in the target area is relatively high, so calculating the remaining water volume can be omitted to save power. After the heating element has been operating for a period of time, such as during the last preset duration, the remaining water volume in the target area is relatively low. Calculating the remaining water volume at this time helps to accurately obtain information on changes in the remaining water volume and promptly detect dry burning.

[0052] Furthermore, based on historical data on remaining water volume, the time it takes for the remaining water volume to approach zero under similar initial water volume, temperature, and heating power conditions can be statistically analyzed. This time can then be slightly earlier to determine the start time of the final preset duration. The module in the steam oven used to calculate the remaining water volume can remain in a dormant state before the final preset duration, which helps reduce the steam oven's power consumption.

[0053] In one specific implementation, in response to the detection that the current flowing through the heating element is zero and / or the voltage (the detected current value converted to a voltage domain representation) is constant, the control module can issue a first warning message to indicate that the target area is in a dry-burning state. For example, the steam oven may be equipped with an audible and visual alarm or communicate with the user's smart device. In response to the detection of dry-burning, the control module of the steam oven can activate the audible and visual alarm or send a reminder to the user's smart device to prompt the user to take timely action. Thus, by monitoring the current and / or voltage values ​​of the heating element, dry-burning can be detected in a timely manner, ensuring the safety of the user's life and property. Furthermore, the control module can also control the heating element to cut off the power to stop heating.

[0054] In one specific implementation, during the operation of the heating element, water can be added to the target area in batches. After each addition, this implementation plan can be executed to monitor the remaining water volume in the target area. Furthermore, the control module can determine the timing of the next water addition based on the calculated remaining water volume.

[0055] Taking a steam oven as an example, the steam oven's cooking program can be preset with water addition times. For instance, by default, water is added every ten minutes. By executing S101 and S102, the control module can obtain the real-time remaining water level in the steam heating plate. Assuming the steam oven controls the water pump to start at time t1 to add water to the steam heating plate, the next water addition time should be t1+10 minutes (min) according to the default interval. However, at t1+7 minutes, the control module determines through S101 and S102 that the remaining water in the steam heating plate will evaporate before the next water addition time. Therefore, the control module can advance the next water addition time, for example, by starting the water pump at t1+9 minutes. Thus, the control module can promptly control the water pump to add water before dry burning occurs, preventing dry burning.

[0056] In some embodiments, the action of determining the timing of the next water addition based on the calculated remaining water volume can be performed after each water addition except for the last water addition.

[0057] Furthermore, after the final water addition, the control module can adjust the heating power of the heating element based on the remaining water volume, the temperature of the target area, and the remaining time, so that the remaining water volume in the target area drops to zero at the preset end time. The remaining time is the duration between the current time and the preset end time.

[0058] For example, based on the current temperature of the target area and the remaining water volume at the current moment, the control module can estimate whether the remaining water volume will evaporate completely within the remaining time. If the estimation indicates that the remaining water volume will not evaporate completely within the remaining time, the control module can increase the current flowing through the heating element to increase the heating power of the heating element and accelerate the water evaporation rate. If the estimation indicates that the remaining water volume may evaporate completely before the end of the remaining time, the control module can decrease the current to the heating element to reduce the heating power of the heating element and slow down the water evaporation rate.

[0059] Therefore, by adjusting the heating power according to the remaining water level, the water in the target area is ensured to evaporate completely by the end of the program. The program can be a cooking program for the steam oven. This ensures that no water remains in the target area when the steaming operation is complete, eliminating the need for the user to manually empty the residual water from the steam heating plate after cooking, thus optimizing the user experience. For example, estimating the remaining water level before the last addition ensures timely addition of water before dry burning, while estimating the remaining water level after the last addition ensures timely adjustment of the heating power to guarantee that the water has evaporated completely by the end of the steam oven's program.

[0060] In some embodiments, after each water addition, the control module can update the initial water volume of the target area so that the remaining water volume can be calculated more accurately in subsequent steps. For example, the remaining water volume of the target area detected before each water addition can be summed with the newly added water volume during this addition to obtain the updated initial water volume.

[0061] Figure 2 This is a functional block diagram of a steam oven according to an embodiment of the present disclosure.

[0062] Specifically, refer to Figure 2 The steam oven of this embodiment may include: a steam heating plate 11 for holding water; and a heating pipe 12 for heating the steam heating plate 11 to generate steam. For example, in the physical construction of the steam oven, the control circuitry may be integrated into the non-cooking space of the steam oven and coupled to the heating pipe 12. The heating pipe 12 may be laid below the steam heating plate 11 to heat the water held in the steam heating plate 11. The evaporated water forms steam, which is then transported to the cooking space of the steam oven to heat the food. The steam heating plate 11 may be located below the cooking space so that the generated steam reaches the cooking space with less loss.

[0063] Furthermore, the steam oven may also include a monitoring module 13, coupled to the heating element 12 to monitor the current and / or voltage flowing through the heating element 12. The monitoring module 13 may be connected in series or equivalently in series with the control circuit of the heating element 12. For example, one end of the heating element 12 may be directly or indirectly coupled to the live wire of the power supply, and the other end of the heating element 12 may be coupled to the neutral wire of the power supply via the monitoring module 13.

[0064] Furthermore, the steam oven may also include a control module 14, coupled to the monitoring module 13 to obtain monitoring results. The control module 14 is used to perform the above-mentioned functions. Figure 1 The remaining water detection method described in the embodiment shown is used to detect the remaining water in the steam heating plate 11.

[0065] For example, the steam oven may also include a switch module 15 connected in series between the power supply live wire and the heating element 12, and the control module 14 may control the switch module 15 to conduct in order to apply current to the heating element 12. Furthermore, during the operation of the heating element 12, the monitoring module 13 may continuously monitor the current and / or voltage flowing through the heating element 12 and feed the monitoring results back to the control module 14.

[0066] Therefore, by monitoring the current and / or voltage in the circuit containing the heating element 12, the heating power of the heating element 12 can be accurately and directly obtained. Based on this heating power, the remaining water volume in the steam heating plate 11 can be estimated, eliminating the need for a dedicated sensor on the steam heating plate 11 to detect residual water. Furthermore, eliminating the sensor reduces the number of components that need to be integrated into the steam oven, and all sensor-related connection circuits in the circuit structure can be eliminated, thereby reducing the complexity of the control circuit structure.

[0067] In a specific implementation, continue to refer to Figure 2The steam oven may also include an adjustment module 16 for adjusting the heating power of the heating element 12. Specifically, the adjustment module 16 can be connected in series in the control circuit of the heating element 12; for example, the adjustment module 16 can be coupled between the heating element 12 and the monitoring module 13. This embodiment does not impose any restrictions on the specific placement of the adjustment module 16 and the monitoring module 13 in the control circuit of the heating element 12, as long as they can monitor or adjust the current flowing through the heating element 12.

[0068] Furthermore, the adjustment module 16 can be coupled to the control module 14 and receive control signals sent by the latter. In response to receiving a feedback signal from the monitoring module 13, the control module 14 executes the above-described... Figure 1 The remaining water detection method of the illustrated embodiment can determine the remaining water volume of the steam heating plate 11. If it is determined based on factors such as the remaining water volume that the heating power of the heating tube needs to be increased, the control module 14 sends a control signal to the adjustment module 16 to instruct the adjustment module 16 to increase the current flowing through the heating tube 12; conversely, if it is determined based on factors such as the remaining water volume that the heating power of the heating tube needs to be decreased, the control module 14 sends a control signal to the adjustment module 16 to instruct the adjustment module 16 to decrease the current flowing through the heating tube 12.

[0069] Therefore, the heating power of the heating tube 12 can be adjusted in a timely manner according to the detected remaining water volume, so that the evaporation rate of the water in the steam heating plate 11 is as consistent as possible with the cooking program operation rate.

[0070] In a specific implementation, combined with Figure 2 and Figure 3 The switching module 15 may include a power switch unit 21 for controlling the operating state of the heating element 12; the adjustment module 16 may include a power control unit 22 for adjusting the heating power of the heating element 12; and the monitoring module 13 may include a current detection unit 23 for detecting the current flowing through the heating element 12, the current being related to the remaining water volume. The heating element 12, power switch unit 21, power control unit 22, and current detection unit 23 are connected in series to form the remaining water volume detection circuit in the control circuit.

[0071] Specifically, the power switch unit 21 can control the on or off of the entire series circuit. When the power switch unit 21 is on, the heating tube 12 is energized and generates heat, and the current detection unit 23 detects the current flowing through the heating tube 12. Furthermore, the detected current value can directly reflect the heating power of the heating tube 12, thereby calculating the amount of water evaporated from the steam heating plate 11 within a preset time. Combined with the initial water volume of the steam heating plate 11 at the start of the preset time, the remaining water volume of the steam heating plate 11 at the end of the preset time can be determined.

[0072] Further reference Figure 2 and Figure 3 The control module 14 may include a control unit 24, which is coupled to the power switch unit 21, the power control unit 22, and the current detection unit 23, respectively. The control unit 24 is used to receive feedback signals sent by the current detection unit 23, and send control signals to the power switch unit 21 and / or the power control unit 22 according to the feedback signals. The feedback signals include the current detection results.

[0073] For example, in response to receiving a feedback signal, if the control unit 24 determines that the remaining water in the steam heating plate 11 is low and, based on the current temperature of the steam heating plate 11, the water in the steam heating plate 11 is very likely to evaporate completely before the next water addition, then the control unit 24 sends a control signal to the power control unit 22. The control signal instructs the power control unit 22 to reduce the current flowing through the heating tube 12 to slow down the water evaporation rate. Alternatively, if, in response to receiving a feedback signal, the control unit 24 determines that the remaining water in the steam heating plate 11 is high and the last water addition action of the current cooking program has been performed, then the control unit 24 sends a control signal to the power control unit 22. The control signal instructs the power control unit 22 to increase the current flowing through the heating tube 12 to accelerate the water evaporation rate, so that the water in the steam heating plate 11 is basically evaporated by the end of the cooking program.

[0074] For example, in response to a feedback signal indicating that the current flowing through the heating element 11 is zero, the control unit 24 can determine that the water in the steam heating plate 11 has evaporated completely (i.e., the remaining water volume is zero). The control unit 24 then sends a control signal to the power switch unit 21 to disconnect the series circuit and stop supplying power to the heating element 12. Alternatively, in response to the start of the cooking program, the control unit 24 sends a control signal to the power switch unit 21, instructing it to connect the series circuit to energize the heating element 12.

[0075] In a specific implementation, continue to refer to Figure 2 and Figure 3 The current detection unit 23 may include a current transformer 231 for sensing the current flowing through the heating tube 12. Specifically, the current transformer 231 can acquire the current flowing through the heating tube 12 in a non-contact manner. In other words, the current transformer 231 can acquire the current of the heating tube 12 without actually connecting to the control circuit of the heating tube 12. Thus, the heating power of the heating tube 12 can be obtained without damaging the original circuit structure of the steam oven.

[0076] Furthermore, the inductive current acquisition method using current transformer 231 also improves safety. Specifically, the series circuit of heating tube 12 is coupled to the power supply of the steam oven, meaning that heating tube 12 operates in a 220V high-voltage environment. If an invasive current acquisition method (such as directly connecting a galvanometer in the series circuit) is used, the galvanometer may be damaged by excessively high current pulses, and the large current value acquired may also damage the control unit 24. Therefore, this embodiment uses current transformer 231 to sense the current of heating tube 12 in a non-invasive manner. Current transformer 231 can proportionally (e.g., 1:1000) reduce the current flowing through heating tube 12, ensuring that the feedback signal received by control unit 24 is within the safe range that control unit 24 can withstand. Thus, the remaining water detection circuit provided in this embodiment has voltage isolation capability, and most of the functional components of the remaining water detection circuit operate in a safe voltage environment of more than 5V, improving the safety of the steam oven.

[0077] Further reference Figure 3 The current detection unit 23 may also include a conductor segment 232 connected in series between the heating tube 12 and the power control unit 22, and a current transformer 231 may be used to sense the current flowing through the conductor segment 232. Thus, the current transformer 231 can be placed at any position in the series circuit, making full use of the empty space inside the steamer.

[0078] For example, in a control circuit, a section of metal wire (equivalent to a current bridge) can be installed as conductor segment 232. The metal wire is connected in a series circuit and passes through the magnetic core of the current transformer 231. The metal wire can be, for example, copper wire.

[0079] Furthermore, the voltage across conductor segment 232 is much greater than the voltage across current transformer 231. For example, the voltage across conductor segment 232 is approximately 220V, while the voltage across current transformer 231 is approximately 5V. Therefore, voltage isolation can be achieved between the heating tube 12 side and the control unit 24 side, and the current waveform in the series circuit can be proportionally converted to a current waveform acceptable to the control unit 24 via the current detection unit 23.

[0080] In a specific implementation, continue to refer to Figure 2 and Figure 3 The current detection unit 23 may include a current-to-voltage conversion circuit 233, which is connected in parallel with the current transformer 231 to convert the current sensed by the current transformer 231 into the voltage domain for characterization.

[0081] Specifically, the current-to-voltage conversion circuit 233 may include at least one sampling resistor. If there are multiple sampling resistors, the multiple sampling resistors are connected in parallel, for example, Figure 3The example shows two sampling resistors connected in parallel (denoted as the first sampling resistor R1 and the second sampling resistor R2, respectively). The design of multiple sampling resistors allows for the use of combinations of resistors with common resistance values ​​to obtain sampling resistors with resistance values ​​suitable for this embodiment. Furthermore, if the current transformer 231 is open-circuited, high voltage will directly act on the control unit 24, causing chip breakdown. Therefore, multiple sampling resistors can be designed as redundancies to ensure the safety of the control circuit.

[0082] In some embodiments, the resistance values ​​of the first sampling resistor R1 and the second sampling resistor R2 can be equal.

[0083] In one specific implementation, the monitoring module 13 may further include an amplification bias unit for amplifying the output value of the sampling resistor and biasing it to a positive value. (Continue to refer to...) Figure 2 and Figure 3 The amplification bias unit can be implemented through an amplification bias circuit. The amplification bias circuit is coupled to the current-voltage conversion circuit 233 to amplify the output value of the current-voltage conversion circuit 233 and bias it to a positive value.

[0084] Specifically, the steam oven is powered by alternating current (AC), and the current transformer 231 senses an AC current. The AC voltage obtained by the current-to-voltage conversion circuit 233 is not suitable for measurement. Therefore, a bias circuit is used to boost the overall voltage waveform to above 0V to facilitate measurement.

[0085] Furthermore, the voltage value output by the current-to-voltage conversion circuit 233 is relatively small, so the voltage value is amplified by a factor of several through an amplifier circuit to facilitate subsequent analysis.

[0086] Therefore, the sampled detection signal (i.e., the AC voltage output by the current-to-voltage conversion circuit 233) is biased and further amplified by the amplification bias unit for subsequent analysis.

[0087] In some embodiments, continue to refer to Figure 3 The amplification bias circuit may include a bias unit 234, coupled to a current-to-voltage conversion circuit 233, the bias unit 234 being used to bias the output value of the current-to-voltage conversion circuit 233 to a positive value; and a power amplifier unit 235, coupled to the bias unit 234, the power amplifier unit 235 being used to amplify the output value of the bias unit 234.

[0088] Specifically, the bias unit 234 may include a first resistor R3 and a second resistor R4, which are respectively coupled to the two ends of the current-to-voltage conversion circuit 233. For example, the first resistor R3 is coupled to one end of the sampling resistor (such as the first sampling resistor R1, or the second sampling resistor R2), and the second resistor R4 is coupled to the other end of the sampling resistor (such as the first sampling resistor R1, or the second sampling resistor R2). In other words, the first resistor R3 is connected in series between one end of the sampling resistor (such as the first sampling resistor R1, or the second sampling resistor R2) and the power amplifier unit 235, and the second resistor R4 is connected in series between the other end of the sampling resistor (such as the first sampling resistor R1, or the second sampling resistor R2) and the power amplifier unit 235. In some embodiments, the resistance values ​​of the first resistor R3 and the second resistor R4 may be equal, and in practical applications, the resistance values ​​of the first resistor R3 and the second resistor R4 can be set according to the required bias amplitude.

[0089] Furthermore, the power amplifier unit 235 may include a power amplifier 236 and a feedback resistor R5 and a filter capacitor connected in parallel with the power amplifier 236. The filter capacitor may include a first filter capacitor C1 and a second filter capacitor C2, which are respectively coupled to different functional pins of the power amplifier 236. The power amplifier 236 can be powered by a supply voltage (5V), and the feedback resistor R5 can improve the stability of the power supply and its anti-interference performance. The filter capacitor can provide a smooth and clean DC voltage for the power amplifier 236, store energy, and reduce distortion of the power amplifier output signal.

[0090] Furthermore, the power amplifier 236 has its power supply terminal VCC coupled to the supply voltage, its ground terminal GND grounded, and a second filter capacitor C2 coupled between the power supply terminal VCC and the ground terminal GND.

[0091] It should be noted that this implementation scheme does not impose any restrictions on the specific structure of the power amplifier unit 235. For example, the power amplifier unit 235 can also adopt other structures such as... Figure 4 The circuit structure shown is shown. Figure 4 The circuit structure of the power amplifier unit 235 shown is similar to... Figure 3 The main differences in the circuit structure of the 235 power amplifier unit include:

[0092] 1. Replace the first filter capacitor C1 with the feedback resistor R6;

[0093] 2. The wiring method of at least one pin of the power amplifier unit 235 is different, as detailed below:

[0094] Figure 3In the circuit structure shown, the first resistor R3 is coupled to the positive input terminal INPLUS of the power amplifier 236, and the positive input terminal INPLUS of the power amplifier 236 is also coupled to the supply voltage through the fourth resistor R8; the second resistor R4 is coupled to the negative input terminal INMINUS of the power amplifier 236; the first filter capacitor C1 is connected in parallel to the negative input terminal INMINUS and the output terminal OUT of the power amplifier 236, and the feedback resistor R5 is connected in parallel with the first filter capacitor C1; the output terminal OUT of the power amplifier 236 is coupled to the control unit 24 through the third resistor R7, and a capacitor C3 is also coupled in the circuit between the third resistor R7 and the control unit 24, with the other end of the capacitor C3 grounded.

[0095] Figure 4 In the circuit structure shown, the fourth resistor R8 is connected in series between the power amplifier 236 and the bias unit 234. Specifically, one end of the fourth resistor R8 is coupled to the positive input terminal INPLUS of the power amplifier 236, and the other end TG of the fourth resistor R8 is coupled to the first resistor R3 of the bias unit 234. The third resistor R7 is connected in series between the power amplifier 236 and the bias unit 234. Specifically, one end of the third resistor R7 is coupled to the negative input terminal INMINUS of the power amplifier 236, and the other end TL of the third resistor R7 is coupled to the second resistor R4 of the bias unit 234. One end of the capacitor C3 is coupled between the third resistor R7 and the second resistor R4, and the other end of the capacitor C3 is grounded. The feedback resistors R5 and R6 are connected in parallel to the negative input terminal INMINUS and the output terminal OUT of the power amplifier 236. The output terminal OUT of the power amplifier 236 is coupled to the control unit 24 to send a feedback signal Output to the latter.

[0096] In one specific implementation, the steam oven may also include a water pump for adding water to the steam heating plate 11. Specifically, the steam oven may be equipped with a water tank for storing water, the water tank being connected to the steam heating plate 11 via a water pipe equipped with a valve. The control module 14 can control the valve to open or close to regulate the connection or disconnection between the water tank and the steam heating plate 11. When the valve opens, the control module 14 controls the water pump to start, delivering water from the water tank to the steam heating plate 11; after water filling is complete, the control module 14 controls the water pump to stop running and controls the valve to close.

[0097] Furthermore, simultaneously or after the control valve opens and the water pump starts, the control module 14 can control the switch module 15 to activate the control circuit containing the heating element 12, so that the heating element 12 is energized and begins to heat up. As the heating element 12 heats up, the water injected into the steam heating plate 11 heats up until it evaporates.

[0098] In a specific implementation, continue to refer to Figure 2The steam oven may also include at least one temperature control switch 17 for controlling the heating element 12 to heat or stop heating. Specifically, the temperature control switch 17 may be connected in series in the control circuit of the heating element 12 and located near the steam heating plate 11 to detect the temperature of the steam heating plate 11.

[0099] Generally, if the steam heating plate 11 becomes dry-burned, its temperature will rise sharply. During the cooking process in the steam oven, the temperature control switch 17 can be in the on state by default, energizing the heating element 12 to achieve the heating function. If a drastic temperature change is detected in the steam heating plate 11 (e.g., exceeding a preset threshold), the temperature control switch 17 disconnects the control circuit of the heating element 12, causing the heating element 12 to stop heating. The preset threshold can be determined in advance through experimentation, such as setting the temperature at which the steam heating plate 11 becomes dry-burned as the preset threshold.

[0100] further, Figure 2 Two temperature control switches 17 are used as an example for illustration. One of the two temperature control switches 17 is connected in series between the switch module 15 and the heating tube 12, and the other is connected in series between the heating tube 12 and the regulating module 16. Both temperature control switches 17 are in the on state by default. When either of the two temperature control switches 17 detects that the temperature of the steam heating plate 11 exceeds a preset threshold, it disconnects the control circuit of the heating tube 12 to control the heating tube 12 to stop heating.

[0101] Therefore, when the remaining water level of the steam heating plate 11 is detected to be zero and dry burning occurs, the power is promptly cut off via the temperature control switch 17 to prevent dry burning and protect the safety of the user's life and property. Furthermore, multiple temperature control switches 17 can be used as a redundant design, so even if one fails, the remaining temperature control switches 17 can still work normally.

[0102] In some embodiments, the power switch unit 21 may include a relay.

[0103] In some embodiments, the control unit 24 may include a microcontroller integrated into the control circuit and coupled to other functional modules of the steam oven to control the overall operation of the steam oven.

[0104] In one variation, the monitoring module 13 may include a voltage sensor (not shown) for acquiring the voltage of the heating element 12. For example, the voltage sensor may be coupled to the control circuit of the heating element 12. Thus, the real-time voltage of the heating element 12 can be directly measured, and the heating power of the heating element 12 can be calculated.

[0105] Furthermore, the steam oven can be equipped with both a voltage sensor and a device such as... Figure 3The current detection unit 23 is shown. The control unit 24 receives the voltage value of the heating tube 12 collected by the voltage sensor and the current value of the heating tube 12 output by the current detection unit 23, and determines the heating power of the heating tube 12 by multiplying the voltage value and the current value, thereby determining the remaining water volume of the steam heating plate 11.

[0106] Although specific embodiments have been described above, these embodiments are not intended to limit the scope of this disclosure, even when only a single embodiment is described with respect to a particular feature. The examples of features provided in this disclosure are intended to be illustrative and not limiting, unless otherwise stated. In practice, one or more technical features of the dependent claims may be combined with technical features of the independent claims, and technical features from the respective independent claims may be combined in any suitable manner rather than solely by the specific combinations listed in the claims.

[0107] While the above disclosure is provided, it is not limited thereto. Any person skilled in the art may make various alterations and modifications without departing from the spirit and scope of this disclosure; therefore, the scope of protection of this disclosure shall be determined by the scope defined in the claims.

Claims

1. A residual water amount detection circuit characterized by comprising: The application relates to a residual water amount detection circuit. The application comprises: a heating pipe (12) for heating water; a power switch unit (21) for controlling the working state of the heating pipe (12); a power control unit (22) for adjusting the heating power of the heating pipe (12); a current detection unit (23) for detecting the current flowing through the heating pipe (12), the current being associated with the residual water amount; 2. The residual water amount detection circuit according to claim 1, characterized by wherein the heating pipe (12), the power switch unit (21), the power control unit (22) and the current detection unit (23) are connected in series. The application further comprises:

3. The residual water amount detection circuit according to claim 1 or 2, characterized by, a control unit (24) coupled with the power switch unit (21), the power control unit (22) and the current detection unit (23) respectively, the control unit (24) being used for receiving a feedback signal sent by the current detection unit (23) and sending a control signal to the power switch unit (21) and / or the power control unit (22) according to the feedback signal, the feedback signal comprising the detection result of the current. The current detection unit (23) comprises: a wire segment (232) connected in series between the heating pipe (12) and the power control unit (22); a current transformer (231) for inducting the current flowing through the wire segment (232); 4. The residual water amount detection circuit according to claim 3, characterized by a current-voltage conversion circuit (233) connected in parallel with the current transformer (231) and used for converting the current to a voltage domain for representation. The current detection unit (23) further comprises:

5. The residual water amount detection circuit according to claim 4, characterized by an amplification bias circuit coupled with the current-voltage conversion circuit (233), the amplification bias circuit being used for amplifying the output value of the current-voltage conversion circuit (233) and biasing to a positive value. The amplification bias circuit comprises: a bias unit (234) coupled with the current-voltage conversion circuit (233), the bias unit (234) being used for biasing the output value of the current-voltage conversion circuit (233) to a positive value; 6. The residual water amount detection circuit according to claim 5, characterized by a power amplifier unit (235) coupled with the bias unit (234), the power amplifier unit (235) being used for amplifying the output value of the bias unit (234).

7. The residual water amount detection circuit according to claim 5, wherein The bias unit (234) comprises a first resistor and a second resistor, the first resistor and the second resistor being coupled with two ends of the current-voltage conversion circuit (233) respectively.

8. The residual water amount detection circuit according to claim 3, characterized by The power amplifier unit (235) comprises a power amplifier (236), a feedback resistor and a filter capacitor connected in parallel with the power amplifier (236).

9. The residual water amount detection circuit according to claim 3, characterized by, The voltage at two ends of the wire segment (232) is much larger than the voltage at two ends of the current transformer (231).

10. A steaming box, characterized by The current-voltage conversion circuit (233) comprises a first sampling resistor and a second sampling resistor connected in parallel. The application further relates to a steam heating disc (11) for carrying water and the residual water amount detection circuit in any one of claims 1 to 9 for detecting the residual water amount of the steam heating disc (11).

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