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 utility model provides an atomizing sheet dry burning protection circuit with hardware overvoltage clamping and software control functions, which is characterized in that transient voltage suppression diodes are connected in parallel at two ends of an MOS (Metal Oxide Semiconductor) tube or an atomizing sheet of an LC (Liquid Crystal) 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, strong compatibility and the like.

Description

TECHNICAL FIELD

[0001] The utility model belongs to liquid atomization technical field, more specifically, relate to a kind of atomization piece dry burning protection circuit. BACKGROUND

[0002] As the core equipment for converting liquid into small mist droplets using high-frequency vibration, the nebulizer is widely used in medical aerosol administration, industrial spray cooling, smart home humidification and other scenarios. Among them, the piezoelectric nebulizer becomes the mainstream due to its high energy conversion efficiency, uniform atomization particles and other advantages. The core component of the piezoelectric nebulizer, the atomization piece (piezoelectric ceramic transducer piece), converts electrical energy into high-frequency mechanical vibration of about 1.7 MHz or 2.4 MHz through the inverse piezoelectric effect, realizing liquid atomization. However, when the piezoelectric nebulizer is dry burning (liquid is depleted or the liquid level is insufficient), the atomization piece loses the liquid load, causing the LC resonance circuit in the drive circuit to be out of tune, and the inductor element generates a voltage spike of up to hundreds of volts at the moment of MOS tube shutdown, causing irreversible damage such as piezoelectric ceramic breakdown and electrode layer shedding in the atomization piece.

[0003] The prior art mainly detects current threshold or frequency offset to realize dry burning alarm. For example, a Chinese invention patent with the publication number CN114877507B, granted on May 10, 2024, discloses a kind of atomization piece dry burning protection circuit, humidifying device and dry burning protection method, which includes a power supply module, a vibration starting module, a control module, a current detection module and a temperature detection module. The input end of the power supply module is connected to an external power supply. The output end of the power supply module is connected to the control module and the vibration starting module, respectively. The control module is connected to the vibration starting module and the current detection module, respectively. The vibration starting module also includes an output port for connecting the atomization piece. The current detection module is used to detect the first working current of the atomization piece. The temperature detection module detects the detection temperature of the atomization piece. The control module is used to output a high-frequency drive signal to make the vibration starting module control the atomization piece to resonate according to the high-frequency drive signal. The power supply module is used to provide power for the control module and the vibration starting module. However, it takes a certain amount of time to detect the increase in current. This invention patent does not absorb energy for transient overvoltage. During the detection of the circuit, the inductor element generates a voltage spike of up to hundreds of volts at the moment of MOS tube shutdown, which can still cause irreversible damage such as piezoelectric ceramic breakdown and electrode layer shedding in the atomization piece. The actual dry burning tolerance is only 50 times, and there is still a risk of electrode shedding during long-term use. Therefore, the protection effect of this invention on the atomization piece is limited, and a composite protection scheme is needed to real-time suppress voltage spikes and quickly cut off energy injection to improve the dry burning tolerance. UTILITY MODEL CONTENT

[0004] The utility model discloses a dry burning protection circuit of atomizing piece to further improve the protection effect of atomizing piece.

[0005] In order to realize the above-mentioned utility model purposes, the dry burning protection circuit of atomizing piece includes a driving circuit and an atomizing piece, and is characterized in that it further includes:

[0006] At least one transient voltage suppression diode (TVS) is used as an overvoltage clamping unit, and the transient voltage suppression diode is connected in parallel in an LC resonant circuit of the driving circuit.

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

[0008] As a further improvement, the transient voltage suppression diode has at least two, and is connected in parallel between the drain and the source of a driving MOS tube of the driving circuit and between the two poles of the atomizing piece, respectively.

[0009] The transient voltage suppression diode is a unidirectional or bidirectional transient voltage suppression diode.

[0010] As a further improvement, the dry burning protection circuit of atomizing piece further includes a control unit, which monitors the atomizing piece loop current in real time through a sampling resistor.

[0011] The utility model discloses a dry burning protection circuit of atomizing piece to further improve the protection effect of atomizing piece.

[0012] In view to the atomizing piece failure problem caused by voltage peak impact and energy loss during dry burning in the prior art, the utility model provides a kind of atomizing piece dry burning protection circuit with hardware overvoltage clamping and software control, by parallel transient voltage suppression diode at the both ends of MOS tube or atomizing piece in the LC resonant loop of drive circuit, in combination with control unit (usually realized using microprocessor), real-time current detection, form the cooperative protection mechanism of hardware clamping and software detection, realize the double inhibition of overvoltage and overheat during dry burning process, effectively reduce the overvoltage and thermal damage that atomizing piece bears, significantly improve the dry burning resistance of atomizing piece, the dry burning resistance of atomizing piece is improved from 50 times to 1000 times or more.The utility model can be applicable to he excitation type and self-excitation type atomizer drive circuit, can be used for medical, industrial and household atomizer, with the advantages of simple circuit, low cost, strong compatibility etc.

[0013] The utility model has the following beneficial effects:

[0014] 1, overvoltage suppression efficiency improves: compared with traditional scheme, the shunt clamping of transient voltage suppression diode reduces the voltage that atomizing piece bears by 30%-40%, and the service life of electrode layer is prolonged by more than 5 times;

[0015] 2, heat damage risk reduces: in combination with control unit real-time current detection, and fast shutdown, dry burning energy injection time is controlled within a few seconds, temperature peak value is reduced from 250 DEG C to below 150 DEG C, avoid piezoelectric ceramic depolarization;

[0016] 3, compatibility enhances:

[0017] When transient voltage suppression diode is directly connected in parallel to the two poles of atomizing piece, the utility model can be directly applied to self-excitation type atomizer, without changing original oscillation circuit, and the adaptability is better than pure software detection scheme. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is the principle diagram of a specific embodiment of the atomizing piece dry burning protection circuit of the utility model;

[0019] Figure 2 It is atomizing piece voltage waveform diagram when working normally;

[0020] Figure 3 It is the waveform diagram measured at the both ends of atomizing piece when dry burning occurs and MOS tube and atomizing piece are not connected in parallel with TVS tube;

[0021] Figure 4 It is the waveform diagram measured at the both ends of atomizing piece when dry burning occurs and MOS tube is connected in parallel with TVS tube;

[0022] Figure 5 It is the waveform diagram measured at the both ends of atomizing piece when dry burning occurs and atomizing piece is connected in parallel with TVS tube.

[0023] Figure 6 These are waveforms measured at both ends of the atomizing plate when it is dry-burned, after connecting TVS diodes in parallel at both ends of the MOS transistor and the atomizing plate. Detailed Implementation

[0024] The specific embodiments of this utility model will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand this utility model. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of this utility model will be omitted here.

[0025] In piezoelectric atomizers, the reliable operation of the atomizing plate depends on the dynamic matching between the drive circuit and the load. Under normal operation, such as... Figure 1 As shown, the atomizing plate and the LC resonant circuit (inductors L1 / L2, capacitor C3) form a 1.7MHz resonant system with an equivalent impedance as low as below 2Ω, efficiently converting energy into mechanical vibration energy. During dry burning, the liquid load disappears, and the equivalent impedance of the atomizing plate increases sharply due to detuning (reaching tens of ohms), leading to two major destructive factors in the drive circuit:

[0026] 1. Overvoltage surge caused by inductor back electromotive force

[0027] According to the law of electromagnetic induction When the driving MOSFET is turned off, the inductor current drops sharply (di / dt can reach 10). 8 The back electromotive force generated (A / s level) can form a voltage spike of over 180V (the measured peak-to-peak value reaches 180V without protection). This voltage far exceeds the safe operating range of the atomizing plate (80-110Vp-p), causing grain boundary breakdown of the piezoelectric ceramic of the atomizing plate and oxidation and peeling of the silver layer of the electrode. A single dry burning can cause performance degradation.

[0028] 2. Heat accumulation caused by energy conversion imbalance

[0029] In a detuned state, electrical energy cannot be effectively converted into mechanical energy and is entirely dissipated as Joule heat. The temperature of the atomizing plate rises by more than 200°C per minute, and permanent depolarization occurs after exceeding the Curie temperature (300°C). Existing solutions rely on the MCU to detect a drop in current (e.g., from 2A to 0.24A) to trigger a shutdown, but fatal thermal damage occurs during the response delay (>50ms).

[0030] Analysis of key component characteristics:

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

[0032] 1.1 Resonance state (normal operation):

[0033] Equivalent circuit for pure resistive load Z r ≤ 2Ω, LC loop matches 1.7MHz frequency, energy conversion efficiency > 90%.

[0034] 1.2, Mis-tuned state (dry burning):

[0035] The disappearance of the liquid load causes the equivalent capacitance Co to change, and when the frequency deviates by ± 50kHz, the impedance modulus rises to more than 60Ω (capacitive or inductive dominant), the power factor drops to less than 0.3, and the energy loss increases dramatically.

[0036] 1.3, Analysis of impedance changes when the atomizing piece is working normally and mis-tuned

[0037] Impedance characteristics of piezoelectric devices (taking a 17000kHz specification atomizing piece as an example):

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

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

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

[0041]

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

[0043] Z c = 2πfL

[0044] The actual inductance value is needed, but the trend is that the impedance increases

[0045] Impedance changes when dry burning:

[0046] When dry burning, the atomizing piece loses the water load, and the equivalent capacitance and mechanical damping change, causing the resonant frequency to deviate.

[0047] Actual data support: According to the specification sheet of the atomizing piece, it can be known that the normal underwater impedance is ≤ 2Ω; when dry burning, the impedance may rise to several Ω to several tens of Ω (the specific value needs to be measured experimentally).

[0048] 2, Key parameter matching of transient voltage suppression diode (TVS diode)

[0049] 2.1, Response characteristics:

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

[0051] 2.2, high frequency compatibility:

[0052] The junction capacitance C j ≈30pF, the capacitive reactance XC=3.12kΩ at 1.7MHz, the shunt ratio <0.1% (relative to 2Ω atomization piece impedance), does not affect the normal resonant circuit work.

[0053] 2.3, energy absorption capacity:

[0054] The peak pulse power is 400W, and more than 100 times of 180V peak impact can be withstood, so that the daily dry burning error trigger protection demand is met.

[0055] Figure 1 It is a schematic diagram of a specific embodiment of the atomization piece dry burning protection circuit.

[0056] In this embodiment, as shown in the figure, Figure 1 The atomization piece dry burning protection circuit comprises a driving circuit 1, an atomization piece 2 and at least one transient voltage suppression diode, namely a TVS tube, as an overvoltage clamping unit 3.

[0057] In this embodiment, as shown in the figure, Figure 1 The transient voltage suppression diode has two, namely D2 and D1, which are 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 atomization piece 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, 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 atomization piece, namely the 2 pin, and the cathode is connected to the atomization piece electrode, namely the 1 pin.

[0058] The transient voltage suppression diode is connected in parallel in the LC resonant circuit of the driving circuit, when the atomization piece dry burning causes the atomization piece impedance to increase, the LC resonant circuit load mismatch produces a voltage peak exceeding the normal working voltage, the atomization piece high-frequency current is shunted and clamped, and the voltage across the atomization piece is reduced.

[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 atomization piece:

[0060] Scheme 1: MOS tube end overvoltage clamping

[0061] In the drive MOS tube drain (D) and source (S) between the parallel TVS tube (such as SMAJ80A), using its fast conduction characteristics, the back electromotive force of the MOS tube is clamped to a safe threshold (80-97.6V) when it is turned off, cutting off the transmission path of the overvoltage to the atomizing piece circuit, indirectly protecting the atomizing piece electrode layer from impact (the actual peak-to-peak value is reduced from 180V to 149V).

[0062] Scheme 2: Direct protection of the atomizing piece end

[0063] Parallel TVS tubes are connected to the two poles of the atomizing piece. For the abnormal voltage rise when the atomizing piece is out of tune (such as 180V), the TVS tube is turned on to shunt (the shunt ratio increases with the increase of impedance), and the voltage across the atomizing piece is stabilized below 127V, directly suppressing the electric field strength that the piezoelectric ceramic can withstand (field strength ≤20kV / mm safety threshold).

[0064] Scheme 3: MCU linkage control

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

[0066] Real-time sampling of circuit current:

[0067] The circuit current is monitored by a sampling resistor RA1, and the microprocessor of the control unit collects the voltage signal. When the effective value of the current 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 10kHz, the set current value is 1A, and the set number of oscillation periods is 5.

[0068] Hierarchical protection strategy:

[0069] A, first response: turn off the MOS tube drive signal and stop energy injection (response time <10ms);

[0070] B, second response: trigger the buzzer alarm and LED indication, and lock the system until manual reset to avoid repeated dry burning cumulative damage.

[0071] In the specific implementation process, we can:

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

[0073] 2. Scheme 3: Scheme 1 + Scheme 2 + MCU controlled triple protection, suitable for high reliability requirements, can reduce the dry burning power from 67.5W to 30.5W, and the temperature rise rate is inhibited to below 2.5℃ / s.

[0074] Example 1: Scheme 1 example (MOS tube end protection)

[0075] 1. Component selection:

[0076] SMAJ80A type TVS tube (breakdown voltage 88.8-97.6V, junction capacitance 30pF) is selected and connected in reverse parallel between the D and S poles of MOS tube Q2.

[0077] 2. Workflow:

[0078] A. Normal driving: TVS tube is in high resistance state, which does not affect the transmission of 1.7MHz switching signal;

[0079] B. Dry burning transient: the inductance back electromotive force makes the D-S voltage exceed 97.6V at the moment of MOS tube shutdown, and the TVS tube is immediately turned on to clamp the voltage to below 120V (typical clamping voltage), limiting the peak energy into the atomizing piece circuit.

[0080] Example 2: Scheme 2 example (atomizing piece end protection)

[0081] 1. Component selection:

[0082] Bidirectional TVS tube (such as SMBJ80CA) is selected and directly connected in parallel to the two poles of the atomizing piece TD, with its anode connected to the reference ground of the atomizing piece and its cathode connected to the atomizing piece electrode.

[0083] A. Key parameter acquisition

[0084] A1. Junction capacitance (C j ):

[0085] We use SMAJ80A as an example, which usually has a low junction capacitance value, typically in the range of 10-50pF. Referring to the measured data of similar high-voltage TVS (such as SMAJ series), we assume that the junction capacitance of SMAJ80A is approximately 30pF (actual data manual should be used for reference, this is an estimate).

[0086] A2. High-frequency impedance calculation

[0087] Capacitance impedance formula:

[0088]

[0089] 1.7MHz:

[0090]

[0091] 2.4MHz:

[0092]

[0093] B, shunt analysis in parallel with 2Ω atomizer sheet

[0094] B1, equivalent circuit model

[0095] Atomizer sheet equivalent impedance: Z r = 2Ω (pure resistance).

[0096] TVS high-frequency equivalent model: capacitive reactance X c In parallel with the atomizer sheet.

[0097] B2, shunt current ratio

[0098] The shunt current is determined by the impedance inversely:

[0099]

[0100] 1.7MHz:

[0101] Shunt ratio:

[0102] 2.4MHz:

[0103]

[0104] Conclusion: The shunt of the atomizer sheet by the TVS tube can be ignored (<0.1%) when the atomizer sheet is working normally, and it will not affect the product performance.

[0105] C, impedance change analysis when detuned

[0106] Atomizer sheet (using 1.7MHz as an example) piezoelectric device impedance characteristics:

[0107] At the resonant frequency (1.7MHz), the impedance is minimum (pure resistance, Z r ≤ 2Ω).

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

[0109] For example:

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

[0111]

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

[0113] Z c = 2πfL

[0114] Note: actual inductance value, but the trend is the impedance increases.

[0115] Impedance change when dry burning: when dry burning, the atomizing piece loses water load, the equivalent capacitance and mechanical damping change, causing the resonance frequency to shift. The actual data support: according to the specification, the normal underwater impedance is ≤2Ω; when dry burning, the impedance may rise to several Ω to several tens of Ω.

[0116] D, TVS protection scheme feasibility verification (take SMAJ series TVS tube as an example)

[0117] 1. TVS selection analysis:

[0118] SMAJ80A key parameters:

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

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

[0121] We take a model: JHB25-17A565 atomizing piece as an example

[0122] The atomizing piece working waveform under normal working condition is as shown in Figure 2

[0123] The atomizing piece working voltage is peak-to-peak value 86V, which meets the design requirement of 80-110Vp-p (average 40-55V), which is lower than the V br of SMAJ80A, and the TVS tube is not conducting.

[0124] 2. Impedance matching design:

[0125] The impedance of the atomizing piece is 2Ω when it is working normally, and the impedance of the TVS is 3.12kΩ, so the shunt can be ignored; when the dry burning impedance rises to 60Ω, the shunt ratio of the TVS is increased to 28%, which significantly reduces the power consumption of the atomizing piece (from 67.5W to 33.6W).

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

[0127] 1. Current detection circuit:

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

[0129] 2. Software algorithm:​

[0130] The sliding window algorithm (window width 100 μs) is used to calculate the current effective value. When the current is <1 A and the frequency offset is >±50 kHz for 3 consecutive windows, the dry burning protection program is triggered, and the MOS tube driving signal is turned off through the PWM module.

[0131] In this embodiment, as shown in Figure 1 , the oscillation current passes through the current detection resistor RA1, and then passes through the filter circuit composed of R8 and C5 to input to the 7th pin (CUR) of the MCU. When the current anomaly is detected, the MCU judges the preset condition and the dry burning condition. When the dry burning condition is met, the driving signal is turned off, so that the energy injection is cut off, and the dry burning time is shortened, which also protects the atomizing piece.

[0132] The waveforms under various combinations of dry burning conditions are as follows:

[0133] As shown in Figures 3 to 6 , the TVS tube clamping effect is verified (180V without protection→121V with double TVS protection). Dry burning causes the impedance of the atomizing piece to increase, and the oscillation circuit produces a voltage spike beyond the normal working voltage due to load mismatch.

[0134] 1. The waveform measured across the atomizing piece when the atomizing piece is dry and the MOS tube and the atomizing piece are not connected in parallel with a TVS tube is shown in Figure 3 . From the waveform diagram in Figure 3 , we can measure the peak-to-peak voltage across the atomizing piece when the MOS tube and the atomizing piece are not connected in parallel with a TVS tube, which is 180V.

[0135] 2. The waveform measured across the atomizing piece after the MOS tube is connected in parallel with a TVS tube is shown in Figure 4 . From the waveform diagram in Figure 4 , we can measure the peak-to-peak voltage measured across the atomizing piece after the MOS tube is connected in parallel with a TVS tube, which is 149V.

[0136] 3. The waveform measured across the atomizing piece when the atomizing piece is dry and the atomizing piece is connected in parallel with a TVS tube is shown in Figure 5 . From the waveform diagram in Figure 5 , we can measure the peak-to-peak voltage measured across the atomizing piece when the atomizing piece is connected in parallel with a TVS tube, which is 127V.

[0137] 4. The waveform measured across the atomizing piece when the atomizing piece is dry and the MOS tube and the atomizing piece are connected in parallel with a TVS tube is shown in Figure 6 . From the waveform diagram in Figure 6In the waveform diagram, we can measure the peak-to-peak voltage across the atomizing plate after the MOS tube and the atomizing plate are connected in parallel with the TVS tube, which is 121V.

[0138] Dry burning occurs under the energy loss calculation of the atomizing plate under various parallel TVS tube combination conditions:

[0139] 1. If the resistance of the atomizing plate rises to 60Ω, the dry burning power consumption of the atomizing plate without TVS on the MOS tube and the atomizing plate is:

[0140]

[0141] The peak-to-peak voltage across the atomizing plate is 180V, so 90 in the formula is the average value.

[0142] 2. When TVS is added across the MOS tube alone, the dry burning power consumption of the atomizing plate is:

[0143]

[0144] The peak-to-peak voltage across the atomizing plate is 149V, so 74.5 in the formula is the average value.

[0145] 3. When TVS is added across the atomizing plate alone, the dry burning power consumption of the atomizing plate is:

[0146]

[0147] The peak-to-peak voltage across the atomizing plate is 127V, so 63.5 in the formula is the average value.

[0148] 4. When TVS is added across the MOS tube and the atomizing plate respectively, the dry burning power consumption of the atomizing plate is:

[0149]

[0150] The peak-to-peak voltage across the atomizing plate is 121V, so 60.5 in the formula is the average value.

[0151] Conclusion: From the calculation results of the above four formulas, it can be seen that whether TVS is added across the MOS tube and the atomizing plate alone or in combination, the result can significantly reduce the self power consumption of the atomizing plate 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, the energy injection during dry burning of the atomizing plate can be intervened in time, which can further reduce the energy loss of the atomizing plate during dry burning.

[0153]

[0154] Table 1

[0155] Table 1 is a test data comparison table, which quantifies the temperature rise rate and the number of resistances of different schemes, and proves the significant advantages of the utility model.

[0156] Through the above test and calculation, it can be seen that the utility model can effectively improve the reliability of the atomizing piece in the dry burning scene. In addition, the utility model circuit is simple and the protection effect is remarkable, and is suitable for various atomizers adopting self-excited driving.

[0157] Although the above describes the specific embodiments of the utility model in a demonstrative manner, so as to facilitate the understanding of the utility model by the person skilled in the art, it should be clear that the utility model is not limited to the range of the specific embodiments, and for the person skilled in the ordinary skill in the art, as long as various changes are within the spirit and scope of the utility model defined and determined by the appended claims, these changes are obvious, and all the invention and creation utilizing the concept of the utility model are within the scope of protection.

Claims

1. A dry-burn protection circuit for an atomizing plate, comprising a driving circuit and an atomizing plate, characterized in that, Also includes: At least one transient voltage suppression diode, i.e., a TVS diode, is used as an overvoltage clamping unit. The transient voltage suppression diode is connected in parallel in the LC resonant circuit of the drive circuit. When the atomizing sheet is dry-burned, causing the impedance of the atomizing sheet to increase, and the load mismatch of the LC resonant circuit generates a voltage spike that exceeds the normal operation, the high-frequency current of the atomizing sheet is shunt and clamped to reduce the voltage across the atomizing sheet.

2. The atomizing plate dry-burn protection circuit according to claim 1, characterized in that, The transient voltage suppression diode is connected in parallel between the drain and source of the driving MOS transistor in the driving circuit, or directly in parallel between the two poles of the atomizing sheet.

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

4. The atomizing plate dry-burn protection circuit according to claim 2 or 3, characterized in that, The transient voltage suppression diode can be a unidirectional or bidirectional transient voltage suppression diode. If it is a unidirectional transient voltage suppression diode, when it is connected in parallel between the drain and source of the driving MOSFET, its anode is connected to the source of the MOSFET and its cathode is connected to the drain of the MOSFET. When it is connected in parallel between the two electrodes of the atomizing plate, its anode is connected to the reference ground of the atomizing plate and its cathode is connected to the electrode of the atomizing plate. If it is a bidirectional transient voltage suppression diode, polarity does not need to be distinguished.

5. The atomizing plate dry-burn protection circuit according to claim 4, characterized in that, It also includes a control unit that monitors the atomizer circuit current in real time through a sampling resistor. When the effective value of the atomizer circuit current is lower than the set percentage of the normal operating current and the duration exceeds a set number of oscillation cycles, the control signal is output to turn off the MOS transistor drive and cut off the energy injection.

Images