Ultrasonic piezoelectric ceramic piece contact state detection circuit

Abstract

The embodiment of the invention discloses an ultrasonic piezoelectric ceramic piece contact state detection circuit. According to one specific implementation mode of the method, the ultrasonic piezoelectric ceramic piece contact state detection circuit is composed of a low-pass filter circuit, a reference voltage setting circuit, an input detection circuit and an LED indicating circuit. According to the embodiment, a stable, efficient and easy-to-use scheme is provided for detecting the contact state of the ultrasonic application equipment and the human body.

Description

Technical Field

[0001] The embodiments disclosed herein relate to the field of electronic circuit technology, specifically to an ultrasonic piezoelectric ceramic sheet contact state detection circuit. Background Technology

[0002] Ultrasonic contact heads (e.g., ultrasonic beauty heads), as core components utilizing the piezoelectric effect to convert mechanical energy into electrical energy, are widely used in ultrasonic application equipment (e.g., ultrasonic beauty instruments, ultrasonic physiotherapy equipment). An ultrasonic contact head consists of a metal head and a piezoelectric ceramic plate located inside the metal head. Ultrasonic contact heads are typically designed to contact the human body, and their contact state directly determines the equipment's working efficiency, safety, and energy transfer stability. When the metal head of the ultrasonic contact head contacts the human body surface or is subjected to external stress, the piezoelectric ceramic plate inside the metal head generates a characteristic low-frequency AC signal due to the piezoelectric effect. This physical characteristic becomes a key basis for judging the contact state; therefore, a reliable contact detection circuit is crucial for the development of related equipment.

[0003] Currently, common contact status detection solutions include the following: (1) The indirect detection scheme based on pressure sensor has the characteristic of mechanical deformation hysteresis of pressure sensing unit itself, which will cause a response delay in contact state, and requires the configuration of pressure sensor structure, which is not easy to miniaturize the equipment. (2) The detection scheme based on capacitance change uses the characteristic that the capacitance value of the ultrasonic contact head changes when it comes into contact with the human body as the basis for judgment. It can respond to the contact state in real time, but it is affected by environmental factors such as skin humidity and oil and requires frequent calibration. In addition, the capacitance detection chip is expensive and has strict requirements for circuit board wiring.

[0004] (3) The detection scheme based on impedance characteristics uses the characteristic that the impedance value of the ultrasonic contact head changes when it comes into contact with air or solid medium as the basis for judgment. No additional sensor is required and the structure has good compatibility. However, a high-precision signal source and lock-in amplifier module need to be designed, the circuit structure is complex, the cost is high, and the versatility is poor. Summary of the Invention

[0005] The summary portion of this disclosure is intended to provide a brief overview of the concepts, which will be described in detail in the detailed description portion. This summary portion is not intended to identify key or essential features of the claimed technical solutions, nor is it intended to limit the scope of the claimed technical solutions.

[0006] Some embodiments of this disclosure propose an ultrasonic piezoelectric ceramic sheet contact state detection circuit to solve the technical problems mentioned in the background section above.

[0007] In a first aspect, some embodiments of this disclosure provide an ultrasonic piezoelectric ceramic sheet contact state detection circuit. The method includes: a low-pass filter circuit, wherein the low-pass filter circuit is used to filter out the high-frequency AC signal transmitted by the ultrasonic output device to the piezoelectric ceramic sheet located inside the metal head, and to select the low-frequency AC signal generated by the piezoelectric ceramic sheet inside the metal head when it is subjected to external stress or contacted by a human body surface from the high-frequency AC signal, and provide it as an AC signal source to the input detection circuit; a reference voltage setting circuit, wherein the reference voltage setting circuit provides a DC signal source to the input detection circuit; an input detection circuit, wherein the input detection circuit is used to output a fixed amplitude AC signal generated by superimposing the AC signal source provided by the low-pass filter circuit and the DC signal source provided by the reference voltage setting circuit to an LED indicator circuit in an analog level manner; and an LED indicator circuit, wherein the LED indicator circuit is used to display the state when the metal head is subjected to external stress or contacted by a human body surface.

[0008] Optionally, the low-pass filter circuit includes a 2-pin connector J1 with a 2.54mm pitch, a first resistor R1, a first inductor L1, a first capacitor C1, a second capacitor C2, and a second resistor R2. Specifically: the first pin of the 2-pin connector J1 is simultaneously connected to the positive terminal of the piezoelectric ceramic plate inside the metal head and the first end of the first resistor R1; the second pin of the 2-pin connector J1 is simultaneously connected to the negative terminal of the piezoelectric ceramic plate inside the metal head and a common ground; the second end of the first resistor R1 is connected to the first end of the first inductor L1; the second end of the first inductor L1 is simultaneously connected to the first ends of the first capacitor C1, the second capacitor C2, and the second resistor R2; the second ends of the first capacitor C1 and the second capacitor C2 are connected to a common ground; the second end of the second resistor R2 is simultaneously connected to the common terminal of the third resistor R3 and the fourth resistor R4 in the reference voltage setting circuit, and the base of the first NPN transistor QN1 in the input detection circuit.

[0009] Optionally, the reference voltage setting circuit includes a third capacitor C3, a third resistor R3, a fourth resistor R4, and a first adjustable resistor RV1, wherein: the first end of the third capacitor C3, the first end of the third resistor R3, and one fixed end of the adjustable resistor RV1 are connected to the external power supply VDD; the second end of the third resistor R3 is connected to the second end of the fourth resistor R4, the second end of the second resistor R2 in the low-pass filter circuit, and the base of the first NPN transistor QN1 in the input detection circuit; the second end of the fourth resistor R4 is connected to the sliding end of the adjustable resistor RV1; and the second end of the third capacitor C3 and the other fixed end of the adjustable resistor RV1 are connected to the common ground.

[0010] Optionally, the input detection circuit includes a fifth resistor R5, a first NPN transistor QN1, a sixth resistor R6, a fourth capacitor C4, a seventh resistor R7, a second NPN transistor QN2, an eighth resistor R8, and a fifth capacitor C5. Specifically: the first terminal of the fifth resistor R5 is connected to the external power supply VDD; the second terminal of the fifth resistor R5 is simultaneously connected to the first terminal of the sixth resistor R6 and the collector of the first NPN transistor QN1; the base of the first NPN transistor QN1 is simultaneously connected to the second terminal of the second resistor R2 in the low-pass filter circuit and the common terminal of the third resistor R3 and the fourth resistor R4 in the reference voltage setting circuit. The second end of resistor R6 is connected to the first end of capacitor C4 and the first end of resistor R7. The second end of resistor R7 is connected to the base of NPN transistor QN2. The collector of NPN transistor QN2 is connected to the second end of resistor R8, the first end of capacitor C5, and the cathode of LED1 in the LED indicator circuit. The first end of resistor R8 is connected to the external power supply VDD. The emitter of NPN transistor QN1, the second end of capacitor C4, the emitter of NPN transistor QN2, and the second end of capacitor C5 are connected to the common ground.

[0011] Optionally, the LED indicator circuit includes a first LED indicator LED1 and a ninth resistor R9, wherein: the cathode of the first LED indicator LED1 is connected to the common terminal of the fifth capacitor C5, the eighth resistor R8, and the collector of the second NPN transistor QN2 in the input detection circuit; the anode of the first LED indicator LED1 is connected to the first terminal of the ninth resistor R9; and the second terminal of the ninth resistor R9 is connected to the external power supply VDD.

[0012] The above-described embodiments of this disclosure have the following beneficial effects: In view of the shortcomings of traditional contact detection schemes, such as response delay, high cost, complex circuit structure, and poor versatility, this application proposes an ultrasonic contact head contact state detection circuit composed of a low-pass filter circuit, a reference voltage setting circuit, an input detection circuit, and an LED indicator circuit. It takes into account the characteristics of fast response, low cost, simple circuit structure, and strong versatility, and provides a stable, efficient and easy-to-use solution for detecting the contact state between ultrasonic application equipment (e.g., ultrasonic beauty instrument, ultrasonic physiotherapy equipment) and the human body. Attached Figure Description

[0013] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and elements are not necessarily drawn to scale.

[0014] Figure 1This is a schematic diagram of the ultrasonic piezoelectric ceramic sheet contact state detection circuit according to this disclosure; Figure 2 This is a bottom view of the ultrasonic contact head; Figure 3 This is a side view of the ultrasonic contact head; Figure 4 This is a schematic diagram of a low-pass filter circuit; Figure 5 This is a schematic diagram of the reference voltage setting circuit; Figure 6 This is a schematic diagram of the input detection circuit; Figure 7 This is a schematic diagram of an LED indicator circuit. Detailed Implementation

[0015] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0016] It should also be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings. Unless otherwise specified, the embodiments and features described in this disclosure can be combined with each other.

[0017] It should be noted that the concepts of "first" and "second" mentioned in this disclosure are used only to distinguish different devices, modules or units, and are not used to limit the order of functions performed by these devices, modules or units or their interdependencies.

[0018] It should be noted that the terms "a" and "a plurality of" used in this disclosure are illustrative rather than restrictive, and those skilled in the art should understand that, unless otherwise expressly indicated in the context, they should be understood as "one or more".

[0019] The names of messages or information exchanged between multiple devices in the embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of such messages or information.

[0020] This disclosure will now be described in detail with reference to the accompanying drawings and embodiments.

[0021] Figure 1 This is a schematic diagram of the ultrasonic piezoelectric ceramic sheet contact state detection circuit according to this disclosure. Figure 1As shown, the ultrasonic piezoelectric ceramic contact state detection circuit mainly consists of a low-pass filter circuit, a reference voltage setting circuit, an input detection circuit, and an LED (Light-Emitting Diode) indicator circuit. Specifically: The low-pass filter circuit filters out the high-frequency AC signal transmitted from the ultrasonic output device to the piezoelectric ceramic sheet inside the metal head, and selects the low-frequency AC signal generated by the piezoelectric ceramic sheet when the metal head is subjected to external stress or contact with a human body surface, providing this low-frequency AC signal to the input detection circuit. The reference voltage setting circuit provides a DC signal source to the input detection circuit. The input detection circuit combines the AC signal from the low-pass filter circuit and the DC signal from the reference voltage setting circuit to generate a fixed-amplitude AC signal, which is then output to the LED indicator circuit in analog mode. The LED indicator circuit displays the state of the metal head when subjected to external stress or contact with a human body surface.

[0022] As an example, Figure 2 and Figure 3 The ultrasonic contact head is shown from both a bottom view and a side view. The ultrasonic contact head consists of a metal head 1 and a piezoelectric ceramic sheet 2. The piezoelectric ceramic sheet is further divided into a positive electrode 3 and a negative electrode 4.

[0023] Optionally, the low-pass filter circuit mentioned above includes a 2-pin connector J1 with a 2.54mm pitch, a first resistor R1, a first inductor L1, a first capacitor C1, a second capacitor C2, and a second resistor R2.

[0024] Among them, see Figure 4 The diagram shown is of a low-pass filter circuit. The first pin of the 2.54mm pitch 2-pin connector J1 is simultaneously connected to the positive terminal (PC_OUT) of the piezoelectric ceramic plate inside the metal head and the first end of the first resistor R1. The second pin of the 2.54mm pitch 2-pin connector J1 is simultaneously connected to the negative terminal of the piezoelectric ceramic plate inside the metal head and the GND (Ground) common ground. The second end of the first resistor R1 is connected to the first end of the first inductor L1. The second end of the first inductor L1 is simultaneously connected to the first end of the first capacitor C1, the second capacitor C2, and the second resistor R2. The second ends of the first capacitor C1 and the second capacitor C2 are connected to the GND common ground. The second end of the second resistor R2 (i.e., the Low-Pass Filter to LPF OUT, LPF_OUT, low-pass filter output terminal) is simultaneously connected to the common terminal of the third resistor R3 and the fourth resistor R4 in the reference voltage setting circuit, and the base of the first NPN transistor QN1 in the input detection circuit. Here, the first end can be the left or top end of the component, and the second end can be the right or bottom end of the component.

[0025] In practice, when the metal head of the ultrasonic contact head is not subjected to external stress or is in contact with the human body surface, the piezoelectric ceramic sheet inside it does not output a signal, and the low-pass filter circuit fails.

[0026] Secondly, when the metal head in the ultrasonic contact head is subjected to external stress or comes into contact with the human body surface, the piezoelectric ceramic sheet inside generates a piezoelectric effect due to mechanical stress, thereby outputting a low-frequency AC signal. At this time, the first resistor R1 can absorb the instantaneous current in the circuit to avoid device overload, and can also perform impedance matching with the (subsequent) low-pass filter circuit to ensure stable signal transmission. The low-pass filter circuit composed of the first inductor L1 and the first capacitor C1, with its characteristics of low impedance to low-frequency signals and high impedance to high-frequency signals, allows low-frequency AC signals to pass smoothly, while blocking the transmission of high-frequency interference signals. The second capacitor C2 can further filter out the high-frequency noise remaining in the previous stage and improve the signal purity.

[0027] Specifically, the piezoelectric ceramic sheet has a diameter of 30mm, a thickness of 2mm, and a resonant frequency of 1MHz. When human skin contacts the metal head, the piezoelectric ceramic sheet outputs a 50Hz 17V sine wave signal; when the metal head is inverted on a table, it outputs a 50Hz 9V sine wave signal. R1 is 1KΩ, L1 is 8mH, C1 is 10nF, C2 is 100nF, and R2 is 1KΩ. The low-frequency filter circuit formed by L1 and C1 has a resonant frequency of 11.58KHz. This circuit allows low-frequency signals of 50Hz to pass through with almost no attenuation, while high-frequency signals above 1MHz are significantly attenuated. Ultimately, the combined action of the first resistor R1, the first inductor L1, the first capacitor C1, the second capacitor C2, and the second resistor R2 filters out the high-frequency AC signal transmitted from the ultrasonic output device to the piezoelectric ceramic sheet located inside the metal head of the ultrasonic contact head, and selects the low-frequency AC signal to provide an AC signal source for the input detection circuit.

[0028] Optionally, the reference voltage setting circuit includes a third capacitor C3, a third resistor R3, a fourth resistor R4, and a first adjustable resistor RV1.

[0029] Among them, see Figure 4 and Figure 5 The first terminal of the third capacitor C3, the first terminal of the third resistor R3, and one fixed terminal of the adjustable resistor RV1 are connected to the external power supply VDD. The second terminal of the third resistor R3 is connected to the first terminal of the fourth resistor R4. The second terminal of the second resistor R2 in the low-pass filter circuit and the base of the first NPN transistor QN1 in the input detection circuit are connected. The second terminal of the fourth resistor R4 is connected to the sliding terminal of the adjustable resistor RV1. The second terminal of the third capacitor C3 and the other fixed terminal of the adjustable resistor RV1 are connected to the GND common ground. Additionally, DC1 is the (Direct Current) power supply terminal.

[0030] In practice, when the metal head of the ultrasonic contact head is not subjected to external stress or is in contact with the human body surface, its internal piezoelectric ceramic plate has no signal output, the low-pass filter circuit fails, and thus the input detection circuit has no AC signal source. Under the action of the third capacitor C3, the high-frequency ripple of the external power supply VDD is filtered out, effectively ensuring the stability of the power supply voltage. The voltage divider circuit composed of the third resistor R3, the fourth resistor R4 and the first adjustable resistor RV1 can accurately set the DC level of the output by adjusting the resistance value of the first adjustable resistor RV1, providing a DC signal source for the input detection circuit. Ultimately, the output detection circuit obtains only a DC signal source.

[0031] As an example, the third capacitor C3 is 100nF, the third resistor R3 is 1MΩ, the fourth resistor R4 is 220KΩ, the first adjustable resistor RV1 is 50KΩ, and the resistance between the sliding end of the first adjustable resistor RV1 and the GND common ground line is approximately 3.1KΩ. VDD is powered by a 5V DC power supply. Under the combined action of the third capacitor C3, the third resistor R3, the fourth resistor R4, and the first adjustable resistor RV1, a stable DC signal of approximately 900mV is provided to the input detection circuit.

[0032] Furthermore, when the metal head in the ultrasonic contact head is subjected to external stress or comes into contact with the human body surface, the piezoelectric ceramic sheet inside it generates a piezoelectric effect due to mechanical stress, thereby outputting a low-frequency AC signal. On the one hand, under the action of the low-pass filter circuit, the low-frequency AC signal is filtered out from the piezoelectric ceramic sheet inside the metal head, providing an AC signal source for the input detection circuit. On the other hand, under the action of the third capacitor C3, the high-frequency ripple of the external power supply VDD is filtered out, effectively ensuring the stability of the power supply voltage. The voltage divider circuit composed of the third resistor R3, the fourth resistor R4, and the first adjustable resistor RV1 can output a stable DC level by adjusting the resistance value of the first adjustable resistor RV1. Ultimately, the signal source obtained by the input detection circuit is a fixed-amplitude AC signal generated by superimposing both the AC signal source and the DC signal source.

[0033] Optionally, the input detection circuit includes a fifth resistor R5, a first NPN transistor QN1, a sixth resistor R6, a fourth capacitor C4, a seventh resistor R7, a second NPN transistor QN2, an eighth resistor R8, and a fifth capacitor C5.

[0034] Among them, see Figure 4 , Figure 5 and Figure 6The first terminal of the fifth resistor R5 is connected to the external power supply VDD. The second terminal of the fifth resistor R5 is simultaneously connected to the first terminal of the sixth resistor R6 and the collector of the first NPN transistor QN1. The base of the first NPN transistor QN1 is simultaneously connected to the second terminal of the second resistor R2 in the low-pass filter circuit (i.e., the low-pass filter). OUT, LPF_OUT (low-pass filter output terminal) and the common terminal of the third resistor R3 and the fourth resistor R4 in the reference voltage setting circuit, the second terminal of the sixth resistor R6 is connected to the first terminal of the fourth capacitor C4 and the first terminal of the seventh resistor R7, the second terminal of the seventh resistor R7 is connected to the base of the second NPN transistor QN2, the collector of the second NPN transistor QN2 is connected to the second terminal of the eighth resistor R8 and the first terminal of the fifth capacitor C5 and the cathode of the first LED indicator LED1 in the LED indicator circuit, the first terminal of the eighth resistor R8 is connected to the external power supply VDD, the emitter of the first NPN transistor QN1, the second terminal of the fourth capacitor C4, the emitter of the second NPN transistor QN2, and the second terminal of the fifth capacitor C5 are connected to the GND common ground line.

[0035] In practice, when the metal head of the ultrasonic contact head is not subjected to external stress or is in contact with the human body surface, the ultrasonic piezoelectric ceramic sheet has no signal output, the low-pass filter circuit fails, and under the action of the reference voltage setting circuit, the input detection circuit only obtains a DC signal source. This DC signal causes the first NPN transistor QN1 to conduct. Under the action of the fifth pull-up resistor R5, the collector of the first NPN transistor QN1 is equivalent to being connected to the GND common ground line, that is, the base level of the second NPN transistor QN2 is equivalent to the GND common ground line. Therefore, the second NPN transistor QN2 is cut off. Under the action of the eighth pull-up resistor R8, the collector output level of the second NPN transistor QN2 is the external power supply VDD, that is, the level of the contact state CHECK signal is the external power supply VDD.

[0036] When the metal head of the ultrasonic contact head is subjected to external stress or comes into contact with the human body surface, the piezoelectric ceramic plate inside generates a piezoelectric effect due to mechanical stress, thereby outputting a low-frequency AC signal. Under the combined action of the low-pass filter circuit and the reference voltage setting circuit, the input detection circuit obtains an AC signal with a fixed amplitude. Under the action of the pull-up resistor R5, this signal causes the first NPN transistor QN1 to stably switch between conduction and cutoff. Under the action of the current-limiting protection resistor R6, the signal at the collector of the first NPN transistor QN1 is stably transmitted. The fourth capacitor C4 has the energy storage and The filter has a dual function, providing a stable DC signal to the seventh resistor R7. This signal acts on the base of the second NPN transistor QN2, causing QN2 to conduct. With the pull-up resistor R8, the collector output level of QN2 is equivalent to the GND common ground line, meaning the contact state CHECK signal level is equivalent to the GND common ground line. With the fifth capacitor C5, high-frequency noise at the collector of QN2 is filtered out, thus ensuring a stable collector output level and reliable signal detection.

[0037] As an example, the first NPN transistor QN1 and the second NPN transistor QN2 are SS8050 models. At room temperature of 25°C, the threshold voltage between the base and emitter is about 0.5V. When a voltage of more than 0.5V is applied to the base, it can be made to operate in the conducting state. The fifth resistor R5, the sixth resistor R6, the seventh resistor R7 and the eighth resistor R8 are all 10KΩ, C4 is 47uF, and the fifth capacitor C5 is 100nF.

[0038] Optionally, the LED indicator circuit includes a first LED indicator LED1 and a ninth resistor R9.

[0039] Among them, see Figure 6 and Figure 7 The cathode of the first LED indicator LED1 is connected... Figure 6 In the input detection circuit, the common terminal of the fifth capacitor C5, the eighth resistor R8, and the collector of the second NPN transistor QN2 is connected to the anode of the first LED indicator LED1. The second terminal of the ninth resistor R9 is connected to the external power supply VDD. Additionally... Figure 6 Input detection circuit and Figure 7 The LED indicator circuits are interconnected via the CHECK terminal (i.e., the break point).

[0040] In practice, when the metal head of the ultrasonic contact head is not subjected to external stress or is in contact with the human body surface, the ultrasonic piezoelectric ceramic sheet has no signal output, the low-pass filter circuit fails, and under the combined action of the reference voltage setting circuit and the input detection circuit, the output level of the contact state CHECK signal in the input detection circuit is the external power supply VDD, that is, the cathode level of the first LED indicator LED1 is VDD. Under the action of the pull-up resistor R9, the first LED indicator LED1 cannot be lit.

[0041] In addition, when the metal head in the ultrasonic contact head is subjected to external stress or comes into contact with the human body surface, the piezoelectric ceramic sheet inside generates a piezoelectric effect due to mechanical stress, thereby outputting a low-frequency AC signal. When the low-pass filter is working, under the combined action of the low-pass filter, the reference voltage setting circuit, and the input detection circuit, the output level of the contact state CHECK signal in the input detection circuit is equal to the GND common ground line, that is, the cathode level of the first LED indicator LED1 is equal to the GND common ground line. Under the action of the pull-up resistor R9, the first LED indicator LED1 is lit up.

[0042] The above-described embodiments of this disclosure have the following beneficial effects: (1) Fast response mechanism: Real-time signal processing is achieved using pure hardware circuits, which shortens the response time and solves the response delay problem of traditional solutions.

[0043] (2) Low-cost architecture technology: By adjusting the parameters of the reference voltage circuit, it can be adapted to ultrasonic piezoelectric ceramic sheets of different models and frequencies, without the need for separate design for specific equipment, thus solving the defect of poor universality of traditional solutions.

[0044] (3) Design of contact status detection circuit with integrated LED indicator function: The LED indicator circuit is integrated with the detection circuit to realize the visual judgment of the contact status of the ultrasonic piezoelectric ceramic sheet. No additional display device is required, which simplifies the overall structure of the equipment.

[0045] Specifically, this application has the following technical advantages: fast response, low cost, simple circuit structure, and strong versatility. Fast response: Compared with the delay caused by mechanical trigger feedback in traditional pressure sensor solutions, it simplifies the signal processing link and avoids complex data calculations, greatly improving the identification speed of ultrasonic piezoelectric ceramic sheet contact state detection. Low cost: The module circuit is composed only of common and low-cost components such as resistors, capacitors, transistors, and LEDs. Simple circuit structure: Compared with traditional impedance-based and capacitance-based detection schemes, it uses only conventional components such as resistors, capacitors, transistors, and LEDs, and can be implemented using a double-layer PCB board. Strong versatility: Compared with traditional impedance-based and capacitance-based detection schemes, the resistors, capacitors, transistors, and LEDs used are all conventional components. By changing the metal head with different resonant frequencies, such as 1MHz and 2MHz, the contact state of the ultrasonic contact head can be accurately identified. The circuit is easy to implement and replicate. Status visualization: The LED indicator can intuitively display the status of the ultrasonic piezoelectric ceramic sheet when it is subjected to external stress or when it comes into contact with the human body; when the human body touches the metal head in the ultrasonic contact head, the LED indicator is constantly lit; when the human body does not touch the metal head in the ultrasonic contact head, the indicator is off.

[0046] In summary, this circuit is suitable for use in various ultrasonic beauty devices or ultrasonic physiotherapy equipment, and other electronic devices that require detection of the contact status of the ultrasonic probe. For example, when a user applies the ultrasonic probe of an ultrasonic beauty device to their arm, the piezoelectric ceramic plate inside the probe generates a piezoelectric effect due to the mechanical pressure of the skin, thereby outputting a low-frequency AC signal. Under the action of the reference voltage setting circuit, a fixed amplitude AC signal is provided to the input detection circuit. This signal enables both NPN transistors in the input detection circuit to conduct effectively, thus changing the signal at the output terminal of the input detection circuit from a high level to a low level, thereby illuminating the LED indicator. Furthermore, the subsequent circuit can identify the effective contact between the ultrasonic probe and the human body by acquiring the detection signal. With the help of a high-frequency generation circuit, the high-frequency signal output by the drive control is applied to the piezoelectric ceramic plate, which then generates an inverse piezoelectric effect under the action of the electrical signal, converting electrical energy into mechanical energy, thereby generating high-frequency mechanical vibration (ultrasound). When the probe contacts the human body, the ultrasound can achieve functions such as cleaning and iontophoresis.

[0047] The above description is merely a selection of preferred embodiments of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. An ultrasonic piezoelectric ceramic sheet contact state detection circuit, characterized in that, include: The low-pass filter circuit is used to filter out the high-frequency AC signal transmitted by the ultrasonic output device to the piezoelectric ceramic sheet inside the metal head, and to filter out the low-frequency AC signal generated by the piezoelectric ceramic sheet inside the metal head when it is subjected to external stress or contacted by the human body surface from the high-frequency AC signal, and provide it as an AC signal source to the input detection circuit. A reference voltage setting circuit, wherein the reference voltage setting circuit provides a DC signal source for the input detection circuit; The input detection circuit is used to output a fixed-amplitude AC signal generated by superimposing the AC signal source provided by the low-pass filter circuit and the DC signal source provided by the reference voltage setting circuit to the LED indicator circuit in an analog level manner. The LED indicator circuit is used to display the state of the metal head when it is subjected to external stress or when it comes into contact with the human body surface.

2. The ultrasonic piezoelectric ceramic sheet contact state detection circuit according to claim 1, characterized in that, The low-pass filter circuit includes a 2-pin through-hole connector J1 with a 2.54mm pitch, a first resistor R1, a first inductor L1, a first capacitor C1, a second capacitor C2, and a second resistor R2, wherein: The first pin of the 2.54mm pitch 2PIN connector J1 is connected to the positive terminal of the piezoelectric ceramic plate inside the metal head and the first end of the first resistor R1. The second pin of the 2.54mm pitch 2PIN connector J1 is connected to the negative terminal of the piezoelectric ceramic plate inside the metal head and the common ground. The second end of the first resistor R1 is connected to the first end of the first inductor L1. The second end of the first inductor L1 is connected to the first end of the first capacitor C1, the second capacitor C2, and the second resistor R2. The second ends of the first capacitor C1 and the second capacitor C2 are connected to the common ground. The second end of the second resistor R2 is connected to the common terminal of the third resistor R3 and the fourth resistor R4 in the reference voltage setting circuit, as well as the base of the first NPN transistor QN1 in the input detection circuit.

3. The ultrasonic piezoelectric ceramic sheet contact state detection circuit according to claim 1, characterized in that, The reference voltage setting circuit includes a third capacitor C3, a third resistor R3, a fourth resistor R4, and a first adjustable resistor RV1, wherein: The first terminal of the third capacitor C3, the first terminal of the third resistor R3, and one fixed terminal of the adjustable resistor RV1 are connected to the external power supply VDD. The second terminal of the third resistor R3 is connected to the second terminal of the fourth resistor R4, the second terminal of the second resistor R2 in the low-pass filter circuit, and the base of the first NPN transistor QN1 in the input detection circuit. The second terminal of the fourth resistor R4 is connected to the sliding terminal of the adjustable resistor RV1. The second terminal of the third capacitor C3 and the other fixed terminal of the adjustable resistor RV1 are connected to the common ground.

4. The ultrasonic piezoelectric ceramic sheet contact state detection circuit according to claim 1, characterized in that, The input detection circuit includes a fifth resistor R5, a first NPN transistor QN1, a sixth resistor R6, a fourth capacitor C4, a seventh resistor R7, a second NPN transistor QN2, an eighth resistor R8, and a fifth capacitor C5, wherein: The first end of the fifth resistor R5 is connected to the external power supply VDD. The second end of the fifth resistor R5 is simultaneously connected to the first end of the sixth resistor R6 and the collector of the first NPN transistor QN1. The base of the first NPN transistor QN1 is simultaneously connected to the second end of the second resistor R2 in the low-pass filter circuit and the common terminal of the third resistor R3 and the fourth resistor R4 in the reference voltage setting circuit. The second end of the sixth resistor R6 is simultaneously connected to the first end of the fourth capacitor C4 and the first end of the seventh resistor R7. The second end of the seventh resistor R7 is connected to the base of the second NPN transistor QN2. The collector of the second NPN transistor QN2 is simultaneously connected to the second end of the eighth resistor R8, the first end of the fifth capacitor C5, and the cathode of the first LED indicator LED1 in the LED indicator circuit. The first end of the eighth resistor R8 is connected to the external power supply VDD. The emitter of the first NPN transistor QN1, the second end of the fourth capacitor C4, the emitter of the second NPN transistor QN2, and the second end of the fifth capacitor C5 are connected to the common ground.

5. The ultrasonic piezoelectric ceramic sheet contact state detection circuit according to claim 4, characterized in that, The LED indicator circuit includes a first LED indicator LED1 and a ninth resistor R9, wherein: The cathode of the first LED indicator LED1 is connected to the common terminal of the fifth capacitor C5, the eighth resistor R8, and the collector of the second NPN transistor QN2 in the input detection circuit. The anode of the first LED indicator LED1 is connected to the first terminal of the ninth resistor R9, and the second terminal of the ninth resistor R9 is connected to the external power supply VDD.

Images