Atomizing sheet dry burning protection circuit

Abstract

In order to solve the problem of failure of an atomizing sheet caused by voltage spike impact and energy loss during dry burning in the prior art, the invention provides an atomizing sheet dry burning protection circuit with hardware overvoltage clamping and software control functions, and transient voltage suppression diodes are connected in parallel to two ends of an MOS tube or an atomizing sheet of an LC resonance circuit of a driving circuit. A cooperative protection mechanism of hardware clamping and software detection is formed by combining real-time current detection of the control unit, double suppression of overvoltage and overheating in the dry burning process is achieved, overvoltage and thermal damage borne by the atomization piece are effectively reduced, the dry burning tolerance of the atomization piece is remarkably improved, and the dry burning tolerance frequency of the atomization piece is increased from 50 times to 1000 times or above. The driving circuit can be suitable for separately-excited and self-excited atomizer driving circuits, can be used for medical, industrial and household atomizers, and has the advantages of simple circuit, low cost, high compatibility and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquid atomization, and more specifically, relates to a dry-burning protection circuit for an atomizer. Background Art

[0002] As a core device that uses high-frequency vibration to convert liquid into tiny droplets, the nebulizer is widely used in scenarios such as medical aerosol drug delivery, industrial spray cooling, and smart home humidification. Among them, piezoelectric nebulizers have become mainstream due to their advantages such as high energy conversion efficiency and uniform atomized particles. Its core component, the atomizer (piezoelectric ceramic transducer), converts electrical energy into high-frequency mechanical vibrations of about 1.7MHz or 2.4MHz through the inverse piezoelectric effect to achieve liquid atomization. However, when the piezoelectric nebulizer is dry-burned (liquid is exhausted or the liquid level is insufficient), the atomizer loses its liquid load, causing the LC resonant circuit in the drive circuit to detune, and the inductor generates a voltage spike of up to hundreds of volts at the moment the MOS tube is turned off, causing irreversible damage such as breakdown of the piezoelectric ceramics in the atomizer and shedding of the electrode layer.

[0003] The prior art mostly implements dry burning alarm by detecting current threshold or frequency offset. For example, the Chinese invention patent with authorization announcement number CN114877507B, which was authorized and announced on May 10, 2024, discloses a dry burning protection circuit for an atomizer, a humidifying device and a dry burning protection method, which includes a power supply module, an oscillating module, a control module, a current detection module and a temperature detection module, wherein the input end of the power supply module is connected to an external power supply, the output end of the power supply module is respectively connected to the control module and the oscillating module, the control module is respectively connected to the oscillating module and the current detection module, and the oscillating module also includes an output port for connecting the atomizer; the current detection module is used to detect the first working current of the atomizer; the temperature detection module detects the detection temperature of the atomizer, the control module is used to output a high-frequency driving signal so that the oscillating module controls the atomizer to resonate according to the high-frequency driving signal; the power supply module is used to provide power to the control module and the oscillating module. However, it takes a certain amount of time to detect the increase in current. The invention patent does not absorb energy for transient overvoltage. During the detection circuit, the inductor element generates a voltage spike of up to hundreds of volts when the MOS tube is turned off, which can still cause irreversible damage such as breakdown of piezoelectric ceramics in the atomizer and detachment of the electrode layer. The actual dry-burn tolerance number is only 50 times, and there is still a risk of electrode detachment in long-term use. Therefore, the invention has limited protection effect on the atomizer. There is an urgent need for a composite protection solution that can suppress voltage spikes in real time and quickly cut off energy injection to increase the dry-burn tolerance number. Summary of the invention

[0004] The object of the present invention is to overcome the deficiencies of the prior art and provide a dry burning protection circuit for an atomizing sheet to further improve the protection effect of the atomizing sheet.

[0005] To achieve the above object of the invention, the dry burning protection circuit for an atomizing sheet of the present invention includes a driving circuit and an atomizing sheet, and is characterized in that it further includes:

[0006] At least one transient voltage suppression diode, i.e., a TVS diode, as an overvoltage clamping unit. The transient voltage suppression diode is connected in parallel in the LC resonance circuit of the driving circuit. When the dry burning of the atomizing sheet causes the impedance of the atomizing sheet to increase and the load mismatch of the LC resonance circuit generates a voltage spike exceeding the normal operation, it shunts and clamps the high-frequency current of the atomizing sheet to reduce the voltage across the atomizing sheet.

[0007] As a further improvement, the transient voltage suppression diode is connected in parallel between the drain and source of the driving MOS transistor of the driving circuit, or directly connected in parallel to both poles of the atomizing sheet.

[0008] As a further improvement, there are at least two transient voltage suppression diodes, which are respectively connected in parallel between the drain and source of the driving MOS transistor of the driving circuit and both poles of the atomizing sheet;

[0009] The transient voltage suppression diode is a unidirectional or bidirectional transient voltage suppression diode. If it is a unidirectional transient voltage suppression diode, when connected in parallel between the drain and source of the MOS transistor, its anode is connected to the source of the MOS transistor and its cathode is connected to the drain of the MOS transistor. When connected in parallel to both poles of the atomizing sheet, its anode is connected to the reference ground of the atomizing sheet and its cathode is connected to the electrode of the atomizing sheet. If it is a bidirectional transient voltage suppression diode, there is no need to distinguish the polarity;

[0010] As a further improvement, the dry burning protection circuit for an atomizing sheet of the present invention further includes a control unit, which monitors the current of the atomizing sheet circuit in real time through a sampling resistor. When the effective value of the current of the atomizing sheet circuit is lower than 10% of the normal operating current and the duration exceeds 5 oscillation periods, it outputs a control signal to turn off the driving of the MOS transistor and cut off the energy injection.

[0011] The object of the invention of the present invention is achieved as follows:

[0012] Aiming at the problem of atomizer sheet failure caused by voltage spike impact and energy loss during dry burning in the prior art, the present invention proposes a dry burning protection circuit for atomizer sheets that combines hardware overvoltage clamping and software control. By connecting a transient voltage suppression diode in parallel at both ends of the MOS tube or the atomizer sheet in the LC resonance circuit of the drive circuit, and combining the real-time current detection of the control unit (usually implemented by a microprocessor), a collaborative protection mechanism of hardware clamping and software detection is formed to achieve dual suppression of overvoltage and overheating during dry burning, effectively reducing the overvoltage and thermal damage suffered by the atomizer sheet, significantly improving the dry burning tolerance of the atomizer sheet, and increasing the dry burning tolerance times of the atomizer sheet from 50 times to more than 1000 times. The present invention is applicable to the drive circuits of both hetaerodyne and self-excited atomizers, and can be used in medical, industrial, and household atomizers, with advantages such as simple circuit, low cost, and strong compatibility.

[0013] The present invention has the following beneficial effects:

[0014] 1. Improvement in overvoltage suppression efficiency: Compared with the traditional scheme, the shunt clamping of the transient voltage suppression diode reduces the voltage borne by the atomizer sheet by 30%-40%, and extends the life of the electrode layer by more than 5 times;

[0015] 2. Reduction of the risk of thermal damage: Combining the real-time current detection of the control unit and quickly shutting down, the dry burning energy injection time is controlled within a few seconds, and the temperature peak value drops from 250°C to below 150°C, avoiding the depolarization of the piezoelectric ceramic;

[0016] 3. Enhancement of compatibility:

[0017] When the transient voltage suppression diode is directly connected in parallel at both poles of the atomizer sheet, the present invention can be directly applied to self-excited atomizers without modifying the original oscillation circuit, and the adaptability is better than the pure software detection scheme. Description of the Drawings

[0018] Figure 1 is the schematic diagram of a specific implementation manner of the dry burning protection circuit for the atomizer sheet of the present invention;

[0019] Figure 2 is the voltage waveform diagram of the atomizer sheet during normal operation;

[0020] Figure 3 is the waveform diagram measured at both ends of the atomizer sheet when the atomizer sheet undergoes dry burning and neither the MOS tube nor the atomizer sheet is connected in parallel with a TVS tube;

[0021] Figure 4 is the waveform diagram measured at both ends of the atomizer sheet when the atomizer sheet undergoes dry burning and a TVS tube is connected in parallel only at the MOS tube;

[0022] Figure 5 is the waveform diagram measured at both ends of the atomizer sheet when a TVS tube is connected in parallel only at both ends of the atomizer sheet during dry burning;

[0023] Figure 6 It is the waveform diagram measured at both ends of the atomizing sheet after connecting TVS diodes in parallel at both ends of the MOS transistor and the atomizing sheet respectively when the atomizing sheet is dry burned. Specific embodiments

[0024] The following describes the specific embodiments of the present invention with reference to the accompanying drawings, so that those skilled in the art can better understand the present invention. It should be particularly noted that in the following description, when the detailed description of known functions and designs may dilute the main content of the present invention, these descriptions will be omitted here.

[0025] In a piezoelectric atomizer, the reliable operation of the atomizing sheet depends on the dynamic matching of the drive circuit and the load. When working normally, as Figure 1 shown, the atomizing sheet and the LC resonance circuit (inductor L1 / L2, capacitor C3) form a 1.7 MHz resonance system, and the equivalent impedance is as low as below 2 Ω, and the energy is efficiently converted into mechanical vibration energy. When dry burned, the liquid load disappears, and the equivalent impedance of the atomizing sheet increases sharply due to detuning (up to dozens of ohms), resulting in two major destructive factors in the drive circuit:

[0026] 1. Overvoltage shock caused by the back electromotive force of the inductor

[0027] According to the law of electromagnetic induction When the driving MOS transistor is turned off, the inductor current drops suddenly (di / dt can reach the order of 10 8 A / s), and the generated back electromotive force can form a voltage spike of more than 180 V (the measured peak-to-peak value without protection reaches 180 V). This voltage far exceeds the safe operating range of the atomizing sheet (80 - 110 Vp-p), resulting in the breakdown of the grain boundary of the piezoelectric ceramic of the atomizing sheet and the oxidation and peeling of the electrode silver layer, and the performance attenuation can be caused by a single dry burn.

[0028] 2. Thermal accumulation caused by the imbalance of energy conversion

[0029] In the detuned state, electrical energy cannot be effectively converted into mechanical energy and is all dissipated in the form of Joule heat. The temperature of the atomizing sheet rises by more than 200 °C per minute. After exceeding the Curie temperature (300 °C), permanent depolarization occurs. The existing scheme relies on the MCU to detect the current drop (such as from 2 A to 0.24 A) to trigger shutdown, but fatal thermal damage has occurred during the response delay (>50 ms).

[0030] Analysis of the characteristics of key components:

[0031] 1. Impedance characteristics and detuning mechanism of the atomizing sheet

[0032] 1.1. Resonant state (normal operation):

[0033] The equivalent circuit is a pure resistive load Z r≤2Ω, the LC circuit is matched to a frequency of 1.7 MHz, and the energy conversion efficiency > 90%.

[0034] 1.2. Detuned state (dry burning):

[0035] The disappearance of the liquid load causes a change in the equivalent capacitance C0. When the frequency deviates by ±50 kHz, the impedance modulus rises above 60 Ω (capacitive or inductive dominance), the power factor drops below 0.3, and the energy loss increases sharply.

[0036] 1.3. Analysis of impedance changes during normal operation and detuning of the atomizing sheet

[0037] Impedance characteristics of piezoelectric devices (taking the atomizing sheet with a specification of 17000KHz as an example):

[0038] At the resonant frequency (1700 kHz), the impedance is the smallest (purely resistive, Z r ≤2Ω).

[0039] When the frequency deviates from the resonant point (detuned), the impedance is dominated by capacitive reactance or inductive reactance, and the modulus increases. For example:

[0040] If the frequency deviates to 1650 kHz (lower than the resonant frequency), the impedance is capacitive, and the capacitive reactance is:

[0041]

[0042] If the frequency deviates to 1750 kHz (higher than the resonant frequency), the impedance is inductive, and the inductive reactance is:

[0043] Z c =2πfL

[0044] The actual inductance value is required, but the trend is an increase in impedance

[0045] Impedance change during dry burning:

[0046] During dry burning, the atomizing sheet loses the water load, and the equivalent capacitance and mechanical damping change, resulting in a deviation of the resonant frequency.

[0047] The measured data supports that according to the specification sheet of the atomizing sheet, the impedance under normal water conditions ≤2Ω; during dry burning, the impedance may rise to several Ω to dozens of Ω (the specific value needs to be measured experimentally).

[0048] 2. Key parameter matching of transient voltage suppression diodes, i.e., TVS tubes

[0049] 2.1. Response characteristics:

[0050] The response time of the SMAJ80A type TVS tube < 1 ns, and it can complete conduction within the rising edge of the inductor back electromotive force (about 10 ns), clamp the voltage to 80 - 97.6 V (breakdown voltage range), and the clamping efficiency > 90%.

[0051] 2.2. High-frequency compatibility:

[0052] Junction capacitance C j ≈30 pF. At 1.7 MHz, the capacitive reactance XC = 3.12 kΩ, and the shunt ratio < 0.1% (relative to the impedance of the 2 Ω atomizing sheet), which does not affect the normal operation of the resonant circuit.

[0053] 2.3. Energy absorption capacity:

[0054] The peak pulse power is 400 W, and it can withstand more than 100 spikes of 180 V, meeting the daily protection requirements for dry burning mis-triggering.

[0055] Figure 1 It is the schematic diagram of a specific implementation of the dry burning protection circuit of the atomizing sheet of the present invention.

[0056] In this embodiment, as Figure 1 shown, the dry burning protection circuit of the atomizing sheet of the present invention includes a driving circuit 1, an atomizing sheet 2, and at least one transient voltage suppression diode, i.e., a TVS tube, as an overvoltage clamping unit 3.

[0057] In this embodiment, as Figure 1 shown, there are two transient voltage suppression diodes, i.e., D2 and D1, which are respectively connected in parallel between the drain and source of the driving MOS tube Q2 of the driving circuit 1 and the two poles of the atomizing sheet 2. The transient voltage suppression diodes D2 and D1 are unidirectional transient voltage suppression diodes. The anode of the transient voltage suppression diode D2 is connected to the source of the MOS tube, and the cathode is connected to the drain of the MOS tube. The anode of the transient voltage suppression diode D1 is connected to the reference ground of the atomizing sheet, i.e., pin 2, and the cathode is connected to the electrode of the atomizing sheet, i.e., pin 1.

[0058] The transient voltage suppression diode is connected in parallel in the LC resonant circuit of the driving circuit. When the dry burning of the atomizing sheet causes the impedance of the atomizing sheet to increase and the load of the LC resonant circuit is mismatched, resulting in a voltage spike exceeding the normal operation, it shunts and clamps the high-frequency current of the atomizing sheet to reduce the voltage across the atomizing sheet.

[0059] In the specific implementation process, the transient voltage suppression diode can also be connected in parallel between the drain and source of the driving MOS tube of the driving circuit, or directly connected in parallel to the two poles of the atomizing sheet:

[0060] Scheme 1: Overvoltage clamping at the MOS tube end

[0061] A TVS diode (such as SMAJ80A) is connected in parallel between the drain (D) and source (S) of the driving MOS transistor. Utilizing its fast conduction characteristic, the back electromotive force when the MOS transistor is turned off is clamped at a safe threshold (80 - 97.6V), cutting off the transmission path of the overvoltage to the atomizing sheet circuit, and indirectly protecting the electrode layer of the atomizing sheet from impact (the measured peak-to-peak value drops from 180V to 149V).

[0062] Solution 2: Direct protection at the atomizing sheet end

[0063] TVS diodes are connected in parallel across the two poles of the atomizing sheet. For the abnormal voltage increase (such as 180V) during detuning, through the conduction and shunt of the TVS diodes (the shunt ratio increases with the increase in impedance), the voltage across the atomizing sheet is stabilized below 127V, directly suppressing the electric field intensity borne by the piezoelectric ceramic (the electric field intensity ≤ 20 kV / mm safety threshold).

[0064] Solution 3: MCU interlock control

[0065] In this embodiment, as Figure 1 shown, the dry burning protection circuit of the atomizing sheet further includes a control unit 4, which monitors the current in the atomizing sheet circuit in real time through a sampling resistor. When the MCU monitors that the effective value of the current in the atomizing sheet circuit is lower than a set percentage of the normal operating current, which is 10% in this embodiment, and the duration exceeds a set number, which is 5 oscillation periods in this embodiment, the MCU outputs a control signal to turn off the MOS transistor drive and cut off the energy injection.

[0066] Real-time sampling of the circuit current:

[0067] The circuit current is monitored through the sampling resistor RA1, and the microprocessor of the control unit collects the voltage signal. When the effective current value is lower than the set current value and lasts for a set number of oscillation periods, it is determined to be in a dry burning state. In this embodiment, the sampling resistor RA1 is 0.25Ω, the frequency of the microprocessor collecting the voltage signal is 10 kHz, the set current value is 1A, and the set number of oscillation periods is 5.

[0068] Hierarchical protection strategy:

[0069] A. First-level response: Turn off the MOS transistor drive signal and stop the energy injection (response time < 10 ms);

[0070] B. Second-level response: Trigger the buzzer alarm and LED indication, lock the system until manual reset, and avoid cumulative damage caused by repeated dry burning.

[0071] In the specific implementation process, it is possible to:

[0072] 1. Use Solution 1 or Solution 2 alone, which is suitable for cost-sensitive scenarios;

[0073] 2. Solution 3: Triple protection of Solution 1 + Solution 2 + MCU control, applicable to high-reliability requirements, can reduce the dry-burning power consumption from 67.5W to 30.5W and suppress the temperature rise rate to below 2.5°C / s.

[0074] Example 1: Example of Solution 1 (MOS transistor terminal protection)

[0075] 1. Component selection:

[0076] Select an SMAJ80A type TVS diode (breakdown voltage 88.8 - 97.6V, junction capacitance 30pF), and connect it in reverse parallel between the D and S poles of MOS transistor Q2.

[0077] 2. Working process:

[0078] A. Normal drive: The TVS diode is in a high-impedance state and does not affect the transmission of the 1.7MHz switching signal;

[0079] B. Dry-burning transient: When the MOS transistor turns off instantaneously, the back electromotive force of the inductor causes the D-S voltage to exceed 97.6V, and the TVS diode immediately conducts, clamping the voltage below 120V (typical clamping voltage) to limit the peak energy from entering the atomization sheet circuit.

[0080] Example 2: Example of Solution 2 (atomization sheet terminal protection)

[0081] 1. Component selection:

[0082] Select a bidirectional TVS diode (such as SMBJ80CA), and directly connect it in parallel between the two poles of the atomization sheet TD. Its anode is connected to the reference ground of the atomization sheet, and the cathode is connected to the atomization sheet electrode.

[0083] A. Obtaining key parameters

[0084] A1. Junction capacitance (C j )

[0085] Taking SMAJ80A as an example, its junction capacitance value is usually relatively low, and the typical range is about 10 - 50pF. Referring to the measured data of similar high-voltage TVS diodes (such as the SMAJ series), assuming that the junction capacitance of SMAJ80A ≈ 30pF (subject to the actual data sheet, this is an estimate here).

[0086] A2. High-frequency impedance calculation

[0087] Capacitance impedance formula:

[0088]

[0089] At 1.7MHz:

[0090]

[0091] At 2.4 MHz:

[0092]

[0093] B. Shunt analysis of the shunt connected across the 2 Ω atomizer

[0094] B1. Equivalent circuit model

[0095] Equivalent impedance of the atomizer: Z r = 2 Ω (purely resistive).

[0096] High-frequency equivalent model of TVS: capacitive reactance X c Connected in parallel with the atomizer.

[0097] B2. Shunt current ratio

[0098] The shunt current is determined by the inverse ratio of impedances:

[0099]

[0100] At 1.7 MHz:

[0101] Shunt ratio:

[0102] At 2.4 MHz:

[0103]

[0104] Conclusion: When the atomizer is operating normally, the shunt of the TVS tube to the high-frequency current of the atomizer can be ignored (<0.1%), and it will not affect the product performance.

[0105] C. Analysis of impedance change during detuning

[0106] Impedance characteristics of the piezoelectric device of the atomizer (taking 1.7 MHz as an example):

[0107] At the resonant frequency (1.7 MHz), the impedance is the smallest (purely resistive, Z r ≤ 2 Ω).

[0108] When the frequency deviates from the resonant point (detuning), the impedance is dominated by capacitive reactance or inductive reactance, and the modulus increases.

[0109] For example:

[0110] If the frequency deviates to 1650 kHz (lower than the resonant frequency), the impedance is capacitive, and the capacitive reactance is:

[0111]

[0112] If the frequency deviates to 1750 kHz (higher than the resonant frequency), the impedance is inductive, and the inductive reactance is:

[0113] Z c = 2πfL

[0114] Note: The actual inductance value is required, but the trend is an increase in impedance.

[0115] Impedance change during dry burning: During dry burning, the atomizing sheet loses the water load, and the equivalent capacitance and mechanical damping change, resulting in a shift in the resonance frequency. The measured data supports that according to the specification, the impedance under normal water conditions ≤ 2Ω; the impedance during dry burning may increase to several Ω to dozens of Ω.

[0116] D. Feasibility verification of the TVS protection scheme (taking the SMAJ series TVS tubes as an example)

[0117] 1. TVS selection analysis:

[0118] Key parameters of SMAJ80A:

[0119] Breakdown voltage (Vbr): 88.8V (minimum) to 97.6V (maximum)

[0120] Clamping voltage (Vclamp): 12V (typical value)

[0121] We take an atomizing sheet with the model: JHB25 - 17A565 as an example

[0122] The working waveform of the atomizing sheet under normal working conditions is as Figure 2 shown,

[0123] The working voltage of the atomizing sheet is 86V peak - to - peak, meeting the design requirements of 80 - 110Vp - p (average 40 - 55V), lower than the V of SMAJ80A br , and the TVS tube does not conduct.

[0124] 2. Impedance matching design:

[0125] The impedance of the atomizing sheet during normal operation is 2Ω, the capacitive reactance of the TVS is 3.12kΩ, and the shunt can be ignored; when the dry - burning impedance rises to 60Ω, the TVS shunt ratio increases to 28%, significantly reducing the power consumption of the atomizing sheet (from 67.5W to 33.6W).

[0126] Example 3: Embodiment of Scheme 3 (MCU linkage control)

[0127] 1. Current detection circuit:

[0128] The oscillating current is converted into a voltage signal through RA1 (0.25Ω), and is input to the CUR pin of the MCU (AD sampling accuracy 12 - bit) through the RC filter (cut - off frequency 16kHz) composed of R8 (1kΩ) and C5 (104pF).

[0129] 2. Software algorithm:

[0130] The effective value of the current is calculated using a sliding window algorithm (window width: 100 μs). When the current < 1 A and the frequency deviation > ±50 kHz are detected in three consecutive windows, the dry-burning protection program is triggered, and the MOS tube drive signal is turned off through the PWM module.

[0131] In this embodiment, as Figure 1 shown, the oscillating current passes through the current detection resistor RA1, and then is filtered by the filter circuit composed of R8 and C5 and input to pin 7 (CUR) of the MCU. When an abnormal current is detected, the MCU judges the preset conditions and the dry-burning conditions. When the dry-burning conditions are met, the drive signal is turned off, thereby cutting off the energy injection. Thus, the dry-burning time is shortened, which protects the atomizing sheet.

[0132] Waveforms under various combined conditions during dry burning:

[0133] As Figures 3 - 6 shown, verify the clamping effect of the TVS tube (unprotected 180 V → double TVS protection 121 V). Dry burning causes the impedance of the atomizing sheet to increase, and the oscillating circuit generates voltage spikes beyond normal operation due to load mismatch.

[0134] 1. When the atomizing sheet undergoes dry burning and neither the MOS tube nor the atomizing sheet is paralleled with a TVS tube, the waveform measured at both ends of the atomizing sheet is as Figure 3 shown. From Figure 3 the waveform diagram, we can measure that the peak-to-peak voltage of the atomizing sheet when neither the MOS tube nor the atomizing sheet is paralleled with a TVS tube is 180 V.

[0135] 2. When the atomizing sheet undergoes dry burning and a TVS tube is paralleled only at the MOS tube, the waveform measured at both ends of the atomizing sheet is as Figure 4 shown. From Figure 4 the waveform diagram, we can measure that the peak-to-peak voltage of the atomizing sheet when a TVS tube is paralleled only at the MOS tube is 149 V.

[0136] 3. When the atomizing sheet undergoes dry burning and a TVS tube is paralleled only at both ends of the atomizing sheet, the waveform measured at both ends of the atomizing sheet is as Figure 5 shown. From Figure 5 the waveform diagram, we can measure that the peak-to-peak voltage of the atomizing sheet when a TVS tube is paralleled only at both ends of the atomizing sheet is 127 V.

[0137] 4. When the atomizing sheet undergoes dry burning and TVS tubes are paralleled at both the MOS tube and the atomizing sheet respectively, the waveform measured at both ends of the atomizing sheet is as Figure 6 shown. From Figure 6In the waveform diagram, we can measure that the peak-to-peak voltage measured at both ends of the atomizing sheet is 121V after the atomizing sheet is connected in parallel with a TVS tube at both ends of the MOS tube and the atomizing sheet respectively.

[0138] Calculation of the energy loss of the atomizing sheet under various combinations of parallel TVS tubes during dry burning:

[0139] 1. If the impedance of the atomizing sheet rises to 60Ω, the dry-burning power consumption of the atomizing sheet without adding a TVS to the MOS tube and the atomizing sheet is:

[0140]

[0141] The peak-to-peak voltage at both ends of the atomizing sheet is 180V, so 90 in the formula is the average value.

[0142] 2. When adding a TVS only at both ends of the MOS tube, the dry-burning power consumption of the atomizing sheet is:

[0143]

[0144] The peak-to-peak voltage at both ends of the atomizing sheet is 149V, so 74.5 in the formula is the average value.

[0145] 3. When adding a TVS only at both ends of the atomizing sheet, the dry-burning power consumption of the atomizing sheet is:

[0146]

[0147] The peak-to-peak voltage at both ends of the atomizing sheet is 127V, so 63.5 in the formula is the average value.

[0148] 4. When adding a TVS at both ends of the MOS tube and the atomizing sheet respectively, the dry-burning power consumption of the atomizing sheet is:

[0149]

[0150] The peak-to-peak voltage at both ends of the atomizing sheet is 121V, so 60.5 in the formula is the average value.

[0151] Conclusion: It can be seen from the calculation results of the above 4 formulas that whether adding a TVS tube in parallel to the MOS tube and the atomizing sheet alone, or adding TVS tubes together in combination, the results can significantly reduce the self-power consumption of the atomizing sheet during dry burning, thereby controlling the temperature rise.

[0152] At the same time, combined with the dry-burning current detection function of the single-chip microcomputer MCU, timely intervention in the energy injection during the dry burning of the atomizing sheet can further reduce the energy loss during the dry burning of the atomizing sheet.

[0153]

[0154] Table 1

[0155] Table 1 is a comparison table of test data, quantifying the temperature rise rate and the number of tolerances of different solutions, and proving the significant advantages of the present invention.

[0156] Through the above tests and calculations, it can be seen that the present invention can effectively improve the reliability of the atomizing sheet in the dry burning scenario. In addition, the circuit of the present invention is simple and the protection effect is remarkable, and it is applicable to various atomizer products using the self-excited drive.

[0157] Although the above-described illustrative specific embodiments of the present invention have been described to facilitate the understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions made using the concept of the present invention are within the scope of protection.

Claims

1. An atomizing sheet dry-burning protection circuit, comprising a driving circuit and an atomizing sheet, characterized in that, It further includes: At least one transient voltage suppression diode, namely a TVS diode, as an overvoltage clamping unit. The transient voltage suppression diode is connected in parallel to the LC resonance circuit of the drive circuit. When the atomizing sheet dries out and burns, resulting in an increase in the impedance of the atomizing sheet and a voltage spike beyond the normal operating voltage due to the load mismatch in the LC resonance circuit, it shunts and clamps the high-frequency current of the atomizing sheet to reduce the voltage across the atomizing sheet.

2. The atomizing sheet dry burning protection circuit according to claim 1, wherein The transient voltage suppression diode is connected in parallel between the drain and source of the drive MOS transistor of the drive circuit, or directly connected in parallel to the two poles of the atomizing sheet.

3. The atomizing sheet dry burning protection circuit according to claim 1, characterized in that, There are at least two transient voltage suppression diodes, which are respectively connected in parallel between the drain and source of the drive MOS transistor of the drive circuit and the two poles of the atomizing sheet.

4. The atomizing sheet dry burning protection circuit according to claim 2 or 3, characterized in that, The transient voltage suppression diode is a unidirectional or bidirectional transient voltage suppression diode. If it is a unidirectional transient voltage suppression diode, when connected in parallel between the drain and source of the drive MOS transistor, its anode is connected to the source of the MOS transistor and its cathode is connected to the drain of the MOS transistor. When connected in parallel to the two poles of the atomizing sheet, its anode is connected to the reference ground of the atomizing sheet and its cathode is connected to the electrode of the atomizing sheet. If it is a bidirectional transient voltage suppression diode, there is no need to distinguish the polarity.

5. The atomizing sheet dry-burning protection circuit according to claim 4 further includes a control unit that monitors the current of the atomizing sheet loop in real time through a sampling resistor. When the effective value of the current in the atomizing sheet loop is lower than a set percentage of the normal operating current and the duration exceeds a set number of oscillation periods, it outputs a control signal to turn off the MOS transistor drive and cut off the energy injection.

6. The atomizing sheet dry burning protection circuit according to claim 1, characterized in that Real-time sampling of the loop current: Monitor the loop current through a sampling resistor, and the microprocessor of the control unit collects the voltage signal. When the effective current value is lower than the set current value and lasts for a set number of oscillation periods, it is determined as the dry-burning state. Hierarchical protection strategy: A. First-level response: Turn off the drive signal of the MOS transistor, stop the energy injection, and the response time < 10 ms; B. Second-level response: Trigger the buzzer alarm and LED indication, lock the system until manual reset to avoid cumulative damage caused by repeated dry burning.

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