A power control and drive integrated system of an air fryer

Abstract

The utility model discloses a power control drive integration system of air fryer belongs to circuit drive control technical field. 220VAC power filter circuit is connected with DC DC step -down circuit and heating pipe switch circuit respectively, and DC DC step -down circuit is connected with motor drive circuit and main control MCU respectively, and main control MCU is connected with motor drive circuit, knob control circuit, heating pipe switch circuit, NTC temperature detection circuit and zero -crossing detection circuit respectively. The utility model is used to solve the power panel of traditional air fryer, the upper control board, motor drive board need to separate design, lead to big, high cost. To solve this problem, want to reduce cost and volume, need multi -module integration, and the traditional upper control board adopts button collocation display screen selection, and this leads to the problem that cost and volume can not reduce.

Description

Technical Field

[0001] This utility model belongs to the field of circuit drive control technology, specifically relating to an integrated power control drive system for an air fryer. Background Technology

[0002] Air fryers, a popular appliance that has rapidly penetrated family kitchens in recent years, rely on high-speed circulating hot air technology to achieve baking and frying effects without the need for additional cooking oil. This precisely meets the core demands of modern consumers for healthy eating and a low-fat lifestyle, making them an essential kitchen appliance for small apartments, young families, and health-conscious food enthusiasts. However, with the continuous increase in market penetration, user demands have evolved from "basic oil-free cooking" to a multi-dimensional upgrade towards "safety, reliability, compact portability, and energy efficiency." The potential shortcomings in traditional air fryer designs are gradually being exposed, affecting not only the user experience but also posing safety hazards in certain scenarios. From a safety perspective, as a kitchen appliance that operates in a high-temperature environment for extended periods, the air fryer's safety protection system directly relates to user safety and the safety of family property, and must be adequately protected. In the heating circuit design, the most critical risk lies in the unexpected startup issue caused by MCU malfunction. In traditional designs, if the MCU experiences program malfunctions due to voltage fluctuations, component aging, or external interference, the heating element may malfunction without receiving proper instructions. If food residue remains in the fryer or the user fails to notice in time, the sustained high temperature can easily cause the food to burn or even start a fire, posing a serious threat to home safety. Furthermore, the electrical sparks generated by the relays in the heating circuit during frequent switching are also a significant safety hazard: on one hand, these sparks may interfere with the normal operation of surrounding electronic components, shortening the lifespan of the circuit board; on the other hand, if oil or dust enters the fryer due to improper sealing, the sparks may ignite these flammable substances, further amplifying the safety risk. These issues place higher demands on the protective design of the heating circuit.

[0003] At the circuit board architecture level, traditional air fryer designs have significant limitations. To achieve independent operation of power supply, upper temperature and function control, and motor drive, traditional products typically employ a three-part architecture: a power board, an upper control board, and a motor drive board. While this design meets basic functional requirements, its drawbacks are significant: First, the three circuit boards require independent layout and wiring, and signal and power transmission between them must be achieved through connecting harnesses. This directly results in extremely low internal space utilization for the air fryer, making it difficult to reduce its size and meet the modern family's demand for "miniaturized, space-saving" appliances. Especially in small apartments with limited kitchen counter space, an excessively large body increases storage difficulty. Second, the separate design means more circuit board substrates, electronic components, and connecting wires, which not only increases production costs but also increases the number of connection points between components. Each connection point is a potential point of failure, and long-term use can easily lead to problems such as poor contact and aging wiring, reducing the overall reliability and lifespan of the product.

[0004] As the core power component for hot air circulation in an air fryer, the selection and control technology of the motor have a direct and crucial impact on the cooking efficiency, noise level, energy consumption, and lifespan of the appliance. In traditional air fryer designs, due to cost control and technological barriers, most products use AC motors. While these motors can meet basic hot air drive requirements, they have significant performance shortcomings. AC motors generate considerable noise and vibration during operation, especially at high speeds, and the continuous noise can negatively affect the user's kitchen experience. Furthermore, their energy consumption is relatively high, which does not align with the current trend of "energy saving and low carbon" in the home appliance industry. Additionally, their lifespan is relatively short; long-term, high-frequency use can easily lead to motor wear and power attenuation, increasing the user's subsequent maintenance costs. Summary of the Invention

[0005] This invention provides an integrated power control and drive system for air fryers, addressing the problem that traditional air fryers require separate designs for the power board, upper control board, and motor drive board, resulting in large size and high cost. To solve this problem and reduce cost and size, multi-module integration is necessary. Traditional upper control boards use buttons and a display screen for selection, which limits cost and size reduction.

[0006] This utility model is achieved through the following technical solution:

[0007] An integrated power control and drive system for an air fryer, the system comprising a 220VAC power filter circuit, a DC-DC step-down circuit, a motor drive circuit, a heating element switch circuit, a main control MCU, a knob control circuit, an NTC temperature detection circuit, and a zero-crossing detection circuit;

[0008] The 220VAC power filter circuit is connected to the DC-DC step-down circuit and the heating tube switch circuit respectively. The DC-DC step-down circuit is connected to the motor drive circuit and the main control MCU respectively. The main control MCU is connected to the motor drive circuit, the knob control circuit, the heating tube switch circuit, the NTC temperature detection circuit and the zero-crossing detection circuit respectively.

[0009] The other end of resistor R30 in the NTC temperature detection circuit is connected to one end of resistor R29 and the second end of temperature-changing resistor R11. The first end of temperature-changing resistor R11 is connected to the other end of capacitor C10 and then grounded. The other end of resistor R29 is connected to the working voltage 5V.

[0010] Furthermore, the main control MCU includes a chip U2, and terminal 1 of the chip U2 is connected to one end of the resistor R25 of the programming port.

[0011] Terminal 3 of chip U2 is connected to one end of resistor R28 and one end of capacitor C9 of the zero-crossing detection circuit, respectively.

[0012] Terminal 4 of chip U2 is connected to one end of resistor R30 and one end of capacitor C10 of the NTC temperature detection circuit, respectively.

[0013] Terminal 5 of the chip U2 is connected to one end of resistor R37 in the knob control circuit.

[0014] Terminal 6 of the chip U2 is connected to one end of resistor R38 in the knob control circuit.

[0015] Terminal 7 of the chip U2 is connected to one end of resistor R39 in the knob control circuit.

[0016] Terminal 8 of chip U2 is connected to a 24V voltage, terminal 9 of chip U2, one end of capacitor C3, and the operating voltage of 24V. Terminal 9 of chip U2 is connected to a 24V voltage.

[0017] Terminal 10 of chip U2 is connected to the other end of capacitor C3, one end of capacitor C4, one end of capacitor C5, and the ground terminal, respectively. Terminal 11 of chip U2 is connected to the other ends of capacitor C4 and capacitor C5, respectively.

[0018] Terminal 12 of the chip U2 is connected to one end of resistor R14 in the motor drive circuit.

[0019] Terminal 13 of the chip U2 is connected to one end of resistor R17 in the motor drive circuit.

[0020] Terminal 14 of the chip U2 is connected to one end of resistor R15 in the motor drive circuit.

[0021] Terminal 15 of the chip U2 is connected to one end of resistor R18 in the motor drive circuit.

[0022] Terminal 16 of the chip U2 is connected to one end of resistor R19 in the motor drive circuit.

[0023] Terminal 17 of the chip U2 is connected to one end of resistor R16 in the motor drive circuit.

[0024] Terminal 18 of the chip U2 is connected to one end of capacitor C14 in the heating tube switching circuit.

[0025] Terminal 19 of the chip U2 is connected to one end of resistor R20 and one end of capacitor C6 in the motor drive circuit.

[0026] Terminal 20 of the chip U2 is connected to one end of resistor R22 and the other end of capacitor C6 in the motor drive circuit.

[0027] Terminal 21 of the chip U2 is connected to one end of resistor R21 and one end of capacitor C7 in the motor drive circuit.

[0028] Terminal 22 of the chip U2 is connected to one end of resistor R23 and the other end of capacitor C7 in the motor drive circuit.

[0029] Terminal 23 of the chip U2 is connected to one end of resistor R24 ​​in the programming port.

[0030] Terminal 24 of the chip U2 is connected to one end of resistor R26, one end of capacitor C8, and one end of resistor RB3 of the motor drive circuit.

[0031] Furthermore, in the zero-crossing detection circuit, the other end of resistor R31 is connected to one end of resistor R32, the other end of resistor R32 is connected to one end of resistor R33, the other end of resistor R33 is connected to one end of resistor R34, one end of capacitor C13, and the base (B) terminal of transistor Q2, the collector (C) terminal of transistor Q2 is connected to one end of resistor R27 and the other end of resistor R28, and the other end of resistor R27 is connected to the operating voltage of 5V.

[0032] The E terminal of the transistor Q2 is connected to the other ends of capacitors C13 and C9, respectively, and then grounded.

[0033] Furthermore, the other end of resistor R14 in the motor drive circuit is connected to terminal 4 of field-effect transistor M1, the other end of resistor R17 is connected to terminal 2 of field-effect transistor M1, terminal 3 of field-effect transistor M1 is connected to one end of capacitor C2 and the operating voltage 24V, terminal 1 of field-effect transistor M1 is connected to the other end of resistor R20 and one end of resistor RB1, and the other end of resistor RB1 is connected to the other end of resistor R22, the other end of resistor R26, one end of resistor RB3, the other end of resistor R23, one end of resistor RB2 and terminal 1 of field-effect transistor M3.

[0034] Terminal 2 of the field-effect transistor M3 is connected to the other end of resistor R19, terminal 4 of the field-effect transistor M3 is connected to the other end of resistor R16, and terminal 3 of the field-effect transistor M3 is connected to the operating voltage 24V.

[0035] The other end of resistor RB3 is connected to the other end of resistor R21 and terminal 1 of field-effect transistor M2. Terminal 2 of field-effect transistor M2 is connected to the other end of resistor R18. Terminal 4 of field-effect transistor M2 is connected to the other end of resistor R15. Terminal 3 of field-effect transistor M2 is connected to the operating voltage 24V.

[0036] Terminals 5-8 of the field-effect transistor M1 are all connected to the U terminal of the motor, terminals 5-8 of the field-effect transistor M2 are all connected to the V terminal of the motor, and terminals 5-8 of the field-effect transistor M3 are all connected to the W terminal of the motor; the other end of the capacitor C8 is grounded, and the other end of the resistor RB3 is grounded.

[0037] Furthermore, the other end of resistor R39 in the knob control circuit is connected to the third terminal of the sliding rheostat K3. One end of the sliding rheostat K3 is connected to one end of resistor R40. The other end of resistor R40 is connected to terminal 2 of the digital knob K2 and the operating voltage 5V. The other end of the sliding rheostat K3 is connected to terminal 3 of the digital knob K2 and then grounded.

[0038] The other end of the resistor R37 is connected to terminal 1 of the digital knob K2, and the other end of the resistor R37 is connected to terminal 4 of the digital knob K2.

[0039] Furthermore, the other end of capacitor C18 in the heating tube switching circuit is connected to the anode of diode D8 and the cathode of diode D10, respectively. The cathode of diode D8 is connected to one end of capacitor C11, one end of resistor R35, and one end of resistor R36, respectively. The other end of resistor R36 is connected to the base (B) terminal of transistor Q3. The anode of diode D10 is connected to the other end of capacitor C11, the other end of resistor R35, and the emitter (E) terminal of transistor Q3, and then grounded. The C terminal of Q3 is connected to the positive terminal of diode D6 and one end of solenoid valve K1. The negative terminal of diode D6 is connected to the other end of solenoid valve K1 and the operating voltage 24V. The third terminal of solenoid valve K1 is connected to the AC L input terminal of the power supply circuit. The fourth terminal of solenoid valve K1 is connected to the heating wire interface H1 terminal. The AC N input terminal of the heating tube switching circuit is connected to the AC N input terminal of the power supply circuit. The AC N input terminal is connected to the heating wire interface H3 terminal.

[0040] The beneficial effects of this utility model are:

[0041] From a structural perspective, this utility model integrates traditional multi-board components, simplifies the circuitry, reduces the board size, saves space, and lowers production and assembly costs. In terms of operation, the dual-knob design simplifies the process, making it convenient, efficient, and easy for users to learn.

[0042] Functionally, the various circuits in this invention work together seamlessly. The ingenious design of the heating switch circuit ensures user safety, the NTC circuit provides precise temperature control, and the FOC control of the motor ensures smoother operation.

[0043] While most air fryers of the same cost use AC motors, this invention uses a brushless motor and reduces the cost gap with AC motors by optimizing the peripheral circuitry, thus improving the overall user experience and safety.

[0044] This invention replaces the traditional air fryer's top control panel with two knobs, making it simple and efficient. Attached Figure Description

[0045] Figure 1 This is a structural block diagram of the present invention.

[0046] Figure 2 This is a schematic diagram of the 220VAC power supply filter circuit and DC-DC step-down circuit of this utility model.

[0047] Figure 3 This is a schematic diagram of the motor drive circuit of this utility model.

[0048] Figure 4 This is the schematic diagram of the main control MCU of this utility model.

[0049] Figure 5 This is a schematic diagram of the heating tube switching circuit of this utility model.

[0050] Figure 6 This is a schematic diagram of the zero-crossing detection circuit of this utility model.

[0051] Figure 7 This is a schematic diagram of the knob control circuit of this utility model.

[0052] Figure 8 This is a schematic diagram of the NTC temperature detection circuit of this utility model.

[0053] Figure 9 This is the schematic diagram of the programming port circuit of this utility model. Detailed Implementation

[0054] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of this application with unnecessary detail.

[0055] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0056] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0057] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0058] Implementation Method 1

[0059] like Figure 1As shown, this embodiment provides an integrated power control and drive system for an air fryer. The system includes a 220VAC power filter circuit, a DC-DC step-down circuit, a motor drive circuit, a heating element switch circuit, a main control MCU, a knob control circuit, an NTC temperature detection circuit, and a zero-crossing detection circuit.

[0060] The 220VAC power filter circuit is connected to the DC-DC step-down circuit and the heating tube switch circuit respectively. The DC-DC step-down circuit is connected to the motor drive circuit and the main control MCU respectively. The main control MCU is connected to the motor drive circuit, the knob control circuit, the heating tube switch circuit, the NTC temperature detection circuit and the zero-crossing detection circuit respectively.

[0061] Furthermore, such as Figure 4 As shown, the main control MCU includes chip U2, and terminal 1 of chip U2 is connected to one end of resistor R25 of the programming port.

[0062] Terminal 3 of chip U2 is connected to one end of resistor R28 and one end of capacitor C9 of the zero-crossing detection circuit, respectively.

[0063] Terminal 4 of chip U2 is connected to one end of resistor R30 and one end of capacitor C10 of the NTC temperature detection circuit, respectively.

[0064] Terminal 5 of the chip U2 is connected to one end of resistor R37 in the knob control circuit.

[0065] Terminal 6 of the chip U2 is connected to one end of resistor R38 in the knob control circuit.

[0066] Terminal 7 of the chip U2 is connected to one end of resistor R39 in the knob control circuit.

[0067] Terminal 8 of chip U2 is connected to a 24V voltage, terminal 9 of chip U2, one end of capacitor C3, and the operating voltage of 24V. Terminal 9 of chip U2 is connected to a 24V voltage.

[0068] Terminal 10 of chip U2 is connected to the other end of capacitor C3, one end of capacitor C4, one end of capacitor C5, and the ground terminal, respectively. Terminal 11 of chip U2 is connected to the other ends of capacitor C4 and capacitor C5, respectively.

[0069] Terminal 12 of the chip U2 is connected to one end of resistor R14 in the motor drive circuit.

[0070] Terminal 13 of the chip U2 is connected to one end of resistor R17 in the motor drive circuit.

[0071] Terminal 14 of the chip U2 is connected to one end of resistor R15 in the motor drive circuit.

[0072] Terminal 15 of the chip U2 is connected to one end of resistor R18 in the motor drive circuit.

[0073] Terminal 16 of the chip U2 is connected to one end of resistor R19 in the motor drive circuit.

[0074] Terminal 17 of the chip U2 is connected to one end of resistor R16 in the motor drive circuit.

[0075] Terminal 18 of the chip U2 is connected to one end of capacitor C14 in the heating tube switching circuit.

[0076] Terminal 19 of the chip U2 is connected to one end of resistor R20 and one end of capacitor C6 in the motor drive circuit.

[0077] Terminal 20 of the chip U2 is connected to one end of resistor R22 and the other end of capacitor C6 in the motor drive circuit.

[0078] Terminal 21 of the chip U2 is connected to one end of resistor R21 and one end of capacitor C7 in the motor drive circuit.

[0079] Terminal 22 of the chip U2 is connected to one end of resistor R23 and the other end of capacitor C7 in the motor drive circuit.

[0080] Terminal 23 of the chip U2 is connected to one end of resistor R24 ​​in the programming port.

[0081] Terminal 24 of the chip U2 is connected to one end of resistor R26, one end of capacitor C8, and one end of resistor RB3 of the motor drive circuit.

[0082] Furthermore, in the zero-crossing detection circuit, the other end of resistor R31 is connected to one end of resistor R32, the other end of resistor R32 is connected to one end of resistor R33, the other end of resistor R33 is connected to one end of resistor R34, one end of capacitor C13, and the base (B) terminal of transistor Q2, the collector (C) terminal of transistor Q2 is connected to one end of resistor R27 and the other end of resistor R28, and the other end of resistor R27 is connected to the operating voltage of 5V.

[0083] The E terminal of the transistor Q2 is connected to the other ends of capacitors C13 and C9, respectively, and then grounded.

[0084] Furthermore, the other end of resistor R30 in the NTC temperature detection circuit is connected to one end of resistor R29 and the second end of temperature-changing resistor R11. The first end of temperature-changing resistor R11 is connected to the other end of capacitor C10 and then grounded. The other end of resistor R29 is connected to the operating voltage 5V.

[0085] Furthermore, the other end of resistor R14 in the motor drive circuit is connected to terminal 4 of field-effect transistor M1, the other end of resistor R17 is connected to terminal 2 of field-effect transistor M1, terminal 3 of field-effect transistor M1 is connected to one end of capacitor C2 and the operating voltage 24V, terminal 1 of field-effect transistor M1 is connected to the other end of resistor R20 and one end of resistor RB1, and the other end of resistor RB1 is connected to the other end of resistor R22, the other end of resistor R26, one end of resistor RB3, the other end of resistor R23, one end of resistor RB2 and terminal 1 of field-effect transistor M3.

[0086] Terminal 2 of the field-effect transistor M3 is connected to the other end of resistor R19, terminal 4 of the field-effect transistor M3 is connected to the other end of resistor R16, and terminal 3 of the field-effect transistor M3 is connected to the operating voltage 24V.

[0087] The other end of resistor RB3 is connected to the other end of resistor R21 and terminal 1 of field-effect transistor M2. Terminal 2 of field-effect transistor M2 is connected to the other end of resistor R18. Terminal 4 of field-effect transistor M2 is connected to the other end of resistor R15. Terminal 3 of field-effect transistor M2 is connected to the operating voltage 24V.

[0088] Terminals 5-8 of the field-effect transistor M1 are all connected to the U terminal of the motor, terminals 5-8 of the field-effect transistor M2 are all connected to the V terminal of the motor, and terminals 5-8 of the field-effect transistor M3 are all connected to the W terminal of the motor; the other end of the capacitor C8 is grounded, and the other end of the resistor RB3 is grounded.

[0089] Furthermore, the other end of resistor R39 in the knob control circuit is connected to the third terminal of the sliding rheostat K3. One end of the sliding rheostat K3 is connected to one end of resistor R40. The other end of resistor R40 is connected to terminal 2 of the digital knob K2 and the operating voltage 5V. The other end of the sliding rheostat K3 is connected to terminal 3 of the digital knob K2 and then grounded.

[0090] The other end of the resistor R37 is connected to terminal 1 of the digital knob K2, and the other end of the resistor R37 is connected to terminal 4 of the digital knob K2.

[0091] Furthermore, the other end of capacitor C18 in the heating tube switching circuit is connected to the anode of diode D8 and the cathode of diode D10, respectively. The cathode of diode D8 is connected to one end of capacitor C11, one end of resistor R35, and one end of resistor R36, respectively. The other end of resistor R36 is connected to the base (B) terminal of transistor Q3. The anode of diode D10 is connected to the other end of capacitor C11, the other end of resistor R35, and the emitter (E) terminal of transistor Q3, and then grounded. The C terminal of Q3 is connected to the positive terminal of diode D6 and one end of solenoid valve K1. The negative terminal of diode D6 is connected to the other end of solenoid valve K1 and the operating voltage 24V. The third terminal of solenoid valve K1 is connected to the AC L input terminal of the power supply circuit. The fourth terminal of solenoid valve K1 is connected to the heating wire interface H1 terminal. The AC N input terminal of the heating tube switching circuit is connected to the AC N input terminal of the power supply circuit. The AC N input terminal is connected to the heating wire interface H3 terminal.

[0092] This invention addresses the issue of traditional air fryers requiring separate power boards, control boards, and motor drive boards, which leads to larger size and higher cost. To solve this problem and reduce cost and size, multi-module integration is necessary. Traditional control boards use buttons and displays for selection, which limits cost and size reduction. Therefore, this design uses a rotary knob control, requiring only three I / O ports. This means only three free pins on the MCU are needed for control. This integrated design reduces the circuit board size by approximately 40%. Furthermore, the high degree of integration significantly reduces assembly costs, saving approximately 30% in production and assembly costs.

[0093] As a common kitchen appliance, the air fryer of this invention requires guaranteed safety. The heating circuit must prevent accidental activation and fire in case of MCU malfunction, and also avoid sparks generated during relay switching. Therefore, the heating switch circuit employs a capacitor isolation design (C14 series capacitor + C11 parallel filter) to ensure that only AC signals can drive the transistor. The heating circuit isolation design has passed 100% fault simulation testing. A zero-crossing detection circuit controls the relay to switch at zero point, reducing arcing and grid interference.

[0094] In the design of this air fryer, the selection and control technology of the motor directly impact the device's performance. Traditional air fryers mostly use AC motors, while this system innovatively employs a DC brushless motor combined with advanced FOC (Field Oriented Control) technology. The DC brushless motor replaces the traditional mechanical commutator with an electronic commutator, eliminating friction between the commutator and brushes. This results in smoother motor operation, reduced vibration and noise, and reduced energy loss, making the air fryer more energy-efficient in heating and circulating air. Due to the absence of brush wear, the DC brushless motor has a significantly longer lifespan than an AC motor, reducing maintenance costs and extending the air fryer's lifespan. This design delivers a significant performance improvement, increasing energy efficiency by 15% compared to AC motors. Furthermore, the user experience is also optimized.

[0095] This system combines an NTC temperature detection circuit with a knob control circuit to achieve precise temperature and time control. Users can accurately set cooking parameters according to the needs of the ingredients, improving cooking results. The dual-knob design not only simplifies the operation process but also provides an intuitive user interface, allowing even first-time users to quickly master the system and enjoy a convenient cooking experience.

[0096] Implementation Method 2

[0097] In this embodiment, the main control MCU serves as the control core of the entire system. It receives signals from the knob control circuit and determines the heating temperature and heating time. The MCU receives the heating temperature information fed back by the NTC temperature detection circuit and determines whether the heating temperature has reached the knob's set value. Simultaneously with the start of heating, a drive signal is sent to the motor drive module circuit to control the motor's operation.

[0098] The main control MCU has a built-in bus voltage detection circuit, LDO 5V circuit, and pre-drive circuit. This greatly simplifies the MCU's peripheral circuitry and reduces the board size.

[0099] The main controller sends a drive signal to control the motor speed through an internal algorithm, samples the voltage on phase current resistors RB1 and RB2, amplifies it through the operational amplifier integrated in the main controller MCU and sends it to the ADC integrated in the MCU for sampling, and calculates the current. The current calculation formula is as follows (1). The main controller MCU monitors the phase current and the input bus voltage and the current set speed, and controls the motor output through the algorithm to make the motor reach the set speed.

[0100] The phase current sampling circuit and the OCP sampling circuit together constitute the current monitoring and protection mechanism. The former monitors the current changes in the circuit in real time, while the latter, as an overcurrent protection sampling circuit, quickly triggers the protection mechanism when the current exceeds the safety threshold to prevent circuit damage or safety accidents. Vadc is the AD value sampled by the ADC, Vadcmax is the AD value of the ADC at the reference voltage, Vref is the ADC reference voltage, Aout is the operational amplifier multiple, and RB1 is the resistance value of the sampling resistor.

[0101] (1)

[0102] The bus voltage is integrated into the MCU. Its working principle is that after passing through the voltage divider circuit, the main control MCU samples the AD value through the ADC and calculates the actual voltage. The bus voltage calculation formula is as follows (2): Vadc is the value sampled by the ADC, Vadcmax is the ADC value corresponding to the reference voltage, and Vref is the ADC reference voltage.

[0103] (2)

[0104] Power supply circuit:

[0105] The power supply circuit of this invention consists of two parts. The first part is an AC-to-DC filter and rectifier circuit, where AC power is filtered and then converted into DC power via a rectifier bridge. The second part is a DC-DC step-down switching power supply circuit with a BUCK structure, which converts the voltage to 24V. This power supply is an important power supply circuit for motor drive, and a power chip with high load capacity has been selected.

[0106] Heating switch circuit:

[0107] This invention uses a relay to control the heating wire switch and an AC signal to drive a transistor. A capacitor (C14) is connected in series in the circuit to isolate the AC and DC signals, and a capacitor (C11) is connected in parallel in the circuit for filtering. When an AC signal is input: a high level charges capacitor (C14), and a low level discharges capacitor (C14). The signal is then filtered by capacitor (C11) to become a high-level DC signal, which turns on the transistor, thus heating. If the input signal is only a single high or low level, it cannot pass through capacitor (C14), and therefore will not heat up. This design ensures user safety; the heating will not activate if the MCU malfunctions.

[0108] Zero-crossing detection circuit:

[0109] The sampling AC power input of this invention allows the MCU to quickly determine whether there is a power outage. Furthermore, it controls the relay to open at zero point to avoid sparking and reduce interference to the power grid during switching.

[0110] NTC temperature detection circuit:

[0111] The NTC probe of this invention is placed on the baking pan to detect the temperature of the baking pan and feed the data back to the main control MCU to ensure that the temperature is always kept within the set range and to avoid the food from being overcooked or undercooked.

[0112] Motor drive module: This part of the circuit mainly consists of 3 NMOS and 3 PMOS transistors, with 1 NMOS and 1 PMOS integrated into a single chip to provide stable drive for motor operation.

[0113] Knob control circuit:

[0114] This invention features two knobs for adjusting time and temperature. The temperature adjustment uses a potentiometer-like knob; by adjusting the resistance, the voltage after voltage division is changed and input to the MCU, which then selects the corresponding temperature. The time knob is a digital knob; rotating it selects the time. Rotating the knob one notch sends a high-level signal (OUT1 pin) to the MCU corresponding to 5 minutes. After rotation, pressing the knob sends a high-level signal (OUT2 pin) to confirm and start operation; pressing it again stops operation. These knobs simplify the operation of the air fryer, allowing users to easily learn and use it without a complicated learning process, providing a simple and efficient user experience.

Claims

1. An integrated power control and drive system for an air fryer, characterized in that, The system includes a 220VAC power filter circuit, a DC-DC step-down circuit, a motor drive circuit, a heating tube switch circuit, a main control MCU, a knob control circuit, an NTC temperature detection circuit, and a zero-crossing detection circuit. The 220VAC power filter circuit is connected to the DC-DC step-down circuit and the heating tube switch circuit respectively. The DC-DC step-down circuit is connected to the motor drive circuit and the main control MCU respectively. The main control MCU is connected to the motor drive circuit, the knob control circuit, the heating tube switch circuit, the NTC temperature detection circuit and the zero-crossing detection circuit respectively. The other end of resistor R30 in the NTC temperature detection circuit is connected to one end of resistor R29 and the second end of temperature-changing resistor R11. The first end of temperature-changing resistor R11 is connected to the other end of capacitor C10 and then grounded. The other end of resistor R29 is connected to the working voltage 5V.

2. The system according to claim 1, characterized in that, The main control MCU includes a chip U2, and terminal 1 of the chip U2 is connected to one end of the resistor R25 of the programming port. Terminal 3 of chip U2 is connected to one end of resistor R28 and one end of capacitor C9 of the zero-crossing detection circuit, respectively. Terminal 4 of chip U2 is connected to one end of resistor R30 and one end of capacitor C10 of the NTC temperature detection circuit, respectively. Terminal 5 of the chip U2 is connected to one end of resistor R37 in the knob control circuit. Terminal 6 of the chip U2 is connected to one end of resistor R38 in the knob control circuit. Terminal 7 of the chip U2 is connected to one end of resistor R39 in the knob control circuit. Terminal 8 of chip U2 is connected to a 24V voltage, terminal 9 of chip U2, one end of capacitor C3, and the operating voltage of 24V. Terminal 9 of chip U2 is connected to a 24V voltage. Terminal 10 of chip U2 is connected to the other end of capacitor C3, one end of capacitor C4, one end of capacitor C5, and the ground terminal, respectively. Terminal 11 of chip U2 is connected to the other ends of capacitor C4 and capacitor C5, respectively. Terminal 12 of the chip U2 is connected to one end of resistor R14 in the motor drive circuit. Terminal 13 of the chip U2 is connected to one end of resistor R17 in the motor drive circuit. Terminal 14 of the chip U2 is connected to one end of resistor R15 in the motor drive circuit. Terminal 15 of the chip U2 is connected to one end of resistor R18 in the motor drive circuit. Terminal 16 of the chip U2 is connected to one end of resistor R19 in the motor drive circuit. Terminal 17 of the chip U2 is connected to one end of resistor R16 in the motor drive circuit. Terminal 18 of the chip U2 is connected to one end of capacitor C14 in the heating tube switching circuit. Terminal 19 of the chip U2 is connected to one end of resistor R20 and one end of capacitor C6 in the motor drive circuit. Terminal 20 of the chip U2 is connected to one end of resistor R22 and the other end of capacitor C6 in the motor drive circuit. Terminal 21 of the chip U2 is connected to one end of resistor R21 and one end of capacitor C7 in the motor drive circuit. Terminal 22 of the chip U2 is connected to one end of resistor R23 and the other end of capacitor C7 in the motor drive circuit. Terminal 23 of the chip U2 is connected to one end of resistor R24 ​​in the programming port. Terminal 24 of the chip U2 is connected to one end of resistor R26, one end of capacitor C8, and one end of resistor RB3 of the motor drive circuit.

3. The system according to claim 2, characterized in that, The other end of resistor R31 in the zero-crossing detection circuit is connected to one end of resistor R32. The other end of resistor R32 is connected to one end of resistor R33. The other end of resistor R33 is connected to one end of resistor R34, one end of capacitor C13, and the base (B) terminal of transistor Q2. The collector (C) terminal of transistor Q2 is connected to one end of resistor R27 and the other end of resistor R28. The other end of resistor R27 is connected to the operating voltage of 5V. The E terminal of the transistor Q2 is connected to the other ends of capacitors C13 and C9, respectively, and then grounded.

4. The system according to claim 2, characterized in that, The other end of resistor R14 in the motor drive circuit is connected to terminal 4 of field-effect transistor M1; the other end of resistor R17 is connected to terminal 2 of field-effect transistor M1; terminal 3 of field-effect transistor M1 is connected to one end of capacitor C2 and the operating voltage 24V; terminal 1 of field-effect transistor M1 is connected to the other end of resistor R20 and one end of resistor RB1; and the other end of resistor RB1 is connected to the other end of resistor R22, the other end of resistor R26, one end of resistor RB3, the other end of resistor R23, one end of resistor RB2, and terminal 1 of field-effect transistor M3. Terminal 2 of the field-effect transistor M3 is connected to the other end of resistor R19, terminal 4 of the field-effect transistor M3 is connected to the other end of resistor R16, and terminal 3 of the field-effect transistor M3 is connected to the operating voltage 24V. The other end of resistor RB3 is connected to the other end of resistor R21 and terminal 1 of field-effect transistor M2. Terminal 2 of field-effect transistor M2 is connected to the other end of resistor R18. Terminal 4 of field-effect transistor M2 is connected to the other end of resistor R15. Terminal 3 of field-effect transistor M2 is connected to the operating voltage 24V. Terminals 5-8 of the field-effect transistor M1 are all connected to the U terminal of the motor, terminals 5-8 of the field-effect transistor M2 are all connected to the V terminal of the motor, and terminals 5-8 of the field-effect transistor M3 are all connected to the W terminal of the motor; the other end of the capacitor C8 is grounded, and the other end of the resistor RB3 is grounded.

5. The system according to claim 2, characterized in that, The other end of resistor R39 in the knob control circuit is connected to the third terminal of sliding rheostat K3. One end of sliding rheostat K3 is connected to one end of resistor R40. The other end of resistor R40 is connected to terminal 2 of digital knob K2 and the operating voltage 5V. The other end of sliding rheostat K3 is connected to terminal 3 of digital knob K2 and then grounded. The other end of the resistor R37 is connected to terminal 1 of the digital knob K2, and the other end of the resistor R37 is connected to terminal 4 of the digital knob K2.

6. The system according to claim 2, characterized in that, The other end of capacitor C18 in the heating tube switching circuit is connected to the anode of diode D8 and the cathode of diode D10. The cathode of diode D8 is connected to one end of capacitor C11, one end of resistor R35, and one end of resistor R36. The other end of resistor R36 is connected to the base (B) terminal of transistor Q3. The anode of diode D10 is connected to the other end of capacitor C11, the other end of resistor R35, and the emitter (E) terminal of transistor Q3, and then grounded. Terminal C is connected to the positive terminal of diode D6 and one end of solenoid valve K1. The negative terminal of diode D6 is connected to the other end of solenoid valve K1 and the operating voltage 24V. The third terminal of solenoid valve K1 is connected to the AC input terminal L of the power supply circuit. The fourth terminal of solenoid valve K1 is connected to the heating wire interface H1. The AC input terminal N of the heating tube switching circuit is connected to the AC input terminal N of the power supply circuit. The AC input terminal N is connected to the heating wire interface H3.

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