Digital and analog circuit combined ultrasonic scalpel driving method

Abstract

The invention provides an ultrasonic scalpel driving method combining a digital circuit and an analog circuit, and relates to the technical field of medical ultrasonic scalps.The ultrasonic scalpel driving method comprises the steps that a waveform data table is quantized through the digital technology, quantized waveform data are output through a DA conversion chip, and a driving signal for driving a digital H-bridge circuit is generated; performing power amplification on the driving signal for driving the digital H-bridge circuit through the digital H-bridge circuit, and outputting a driving signal with a square wave waveform; the matched filter circuit filters the square wave signal to form a sine wave signal, so that impedance matching of the piezoelectric ceramic sheet stack connected with the matched filter circuit is realized; an output electric signal is converted into mechanical vibration with corresponding frequency and amplitude through the piezoelectric ceramic piece stack.

Description

Technical Field

[0001] The present invention relates to the technical field of medical ultrasonic scalpels, and particularly relates to a driving method for an ultrasonic scalpel combining digital and analog circuits. Background Art

[0002] Medical ultrasonic scalpels are widely used in the current surgical field and are known as bloodless scalpels. Commonly used driving circuits for medical ultrasonic scalpels: Currently, the commonly used driving circuits adopt Class A or Class AB linear amplifications. See Figure 1 . Such an amplification circuit uses a Direct Digital Synthesizer (DDS) to generate a sine wave signal. The sine wave signal is differentially amplified to generate two sinusoidal waves Vsh and Vsl with complementary phases. Bias amplification adjustment circuits A and B generate DC bias voltages. The bias voltages VA, VB and the sinusoidal AC signals Vsh, Vsl are respectively applied to the gates G of linear MOS transistors Q1 and Q2, and the linear MOS transistors Q1 and Q2 respectively amplify the positive half-cycles of the sinusoidal signals at their gates. A complete sinusoidal driving signal VO is output on the secondary side of the transformer T1. In addition, there are also some current and voltage samplings and feedback signals in the circuit to adjust and correct the frequency and phase of the sine wave output by the DDS signal source. Impedance matching is to match the impedance characteristics of the piezoelectric ceramic stack of the ultrasonic scalpel.

[0003] The limitations of the current driving circuits for medical ultrasonic scalpels are as follows: First, in order to ensure linear amplification, Class A and Class AB amplification circuits need to always work near a certain static DC operating point, resulting in relatively high static power consumption and low energy conversion efficiency of such circuits. Usually, the effective energy conversion efficiency is lower than 30%, which leads to defects in the main body of the device for driving the ultrasonic scalpel: the power supply of the device increases; the device needs to add additional heat dissipation designs; the device is bulky and the heat dissipation design may bring other potential safety hazards, such as the outlet temperature, thermal stability, electromagnetic stability, etc. Second, Class A and Class AB amplification circuits amplify the sine signal step by step, and at the same time, it is necessary to consider meeting the impedance matching characteristics of the piezoelectric ceramic sheet. Moreover, the design and debugging difficulty of the hybrid circuit of high-precision analog signal processing, DDS and feedback high-frequency digital signals and high-power output increase linearly, resulting in a geometric increase in cost. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention proposes a driving method for an ultrasonic scalpel combining digital and analog circuits, including the following steps:

[0005] S1. Quantify the waveform data table by using digital technology.

[0006] S2. Output the quantized waveform data through a DA conversion chip to generate a driving signal for driving the digital H-bridge circuit;

[0007] S3. Amplify the driving signal for driving the digital H-bridge circuit generated in step S2 through the digital H-bridge circuit and output a driving signal with a square wave waveform;

[0008] S4. The matched filtering circuit filters the square wave signal to form a sine wave signal to achieve impedance matching of the piezoelectric ceramic stack connected to the matched filtering circuit;

[0009] S5. Convert the electrical signal output in step S4 through the piezoelectric ceramic stack into mechanical vibrations with corresponding frequencies and amplitudes.

[0010] In a preferred embodiment, in step S1, a direct digital synthesizer DDS is used to generate waveform data tables in two different quantization methods, PWM and SPWM, in advance, and according to the driving requirements of the piezoelectric ceramic stack, a signal with a corresponding output frequency is generated.

[0011] In a preferred embodiment, the waveform output after the direct digital synthesizer DDS is differentially amplified is a pair of square wave signals with complementary waveform phases.

[0012] In a preferred embodiment, in step S2, the DA conversion chip adopts DA conversion technology, and the 10-bit DAC frequency resolution reaches 0.1 Hz.

[0013] In a preferred embodiment, in step S4, the filter and impedance matching circuit parameters are selected to convert the square wave signal output by the digital H-bridge circuit in step S3 into a sine wave output with a corresponding frequency.

[0014] In a preferred embodiment, in step S4, the filter and impedance matching circuit parameters are selected to minimize the energy loss before and after the matched filtering circuit in step S4.

[0015] In a preferred embodiment, the driving signal conversion path includes:

[0016] First, the direct digital synthesizer DDS generates an analog waveform from digital data;

[0017] Secondly, the digital H-bridge circuit converts the analog signal into a digital signal;

[0018] Finally, the filter matching circuit converts the digital signal into an analog signal.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects:

[0020] Compared with the Class AB amplifier circuit, without reducing the adjustable accuracy of the output sine wave, the energy conversion efficiency of the present invention is greatly improved; a large amount of heat dissipation design is not required, and the space size is greatly reduced; the analog design and debugging circuit are reduced, the cost is reduced, and the performance is close to that of the Class AB amplifier circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 Principle of the driving circuit of the commonly used medical ultrasonic scalpel;

[0023] Figure 2 Schematic flow chart of the present invention;

[0024] Figure 3 Schematic diagram of the waveform data representation of the present invention;

[0025] Figure 4 Schematic circuit diagram of the ultrasonic scalpel driving method combining digital and analog circuits of the present invention;

[0026] Figure 5 Schematic diagram of the DDS frequency synthesizer of the present invention;

[0027] Figure 6 PWM output waveform of the present invention;

[0028] Figure 7 SPWM output waveform of the present invention;

[0029] Figure 8 Schematic diagram of the signal conversion path of the present invention;

[0030] Figure 9 Schematic diagram of the waveform conversion before and after RLC impedance matching of the present invention;

[0031] Figure 10 Schematic diagram of the energy comparison before and after the matching filter circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts belong to the scope of protection of this application.

[0033] In the accompanying drawings of the specific embodiments of the present invention, in order to better and more clearly describe the working principles of the components in the system and show the connection relationships of the various parts of the device, only the relative positional relationships between the components are clearly distinguished, and it does not constitute a limitation on the signal transmission direction, connection sequence, and the sizes, dimensions, and shapes of the various parts of the component or structure.

[0034] Embodiment 1

[0035] As Figure 2 shown, it is a flowchart of a method for driving an ultrasonic scalpel by combining digital and analog circuits according to the present invention, including the following steps:

[0036] S1. Quantize the waveform data table using digital technology.

[0037] This quantized waveform data table is a data table composed of a group of discrete digital quantities. As Figure 3 shown in the schematic diagram of waveform data: 16 discrete data from T0 to T15 provide inputs for the S2 digital-to-analog conversion.

[0038] Adopt a direct digital synthesizer (DDS) to generate waveform data tables with two different quantization methods, PWM and SPWM, in advance. According to the driving requirements of the piezoelectric ceramic stack, signals with corresponding output frequencies are generated.

[0039] S2. Output the quantized waveform data through a DA conversion chip to generate a driving signal for driving a digital H-bridge circuit.

[0040] The DA conversion chip uses DA conversion technology with high resolution. The frequency resolution of a 10-bit DAC can reach about 0.1 Hz, which can meet the frequency requirements of the piezoelectric ceramic stack used in the ultrasonic scalpel.

[0041] S3. Amplify the driving signal for driving the digital H-bridge circuit generated in S2 through the digital H-bridge circuit and output a driving signal with a square wave waveform.

[0042] The digital H-bridge circuit amplifies the driving signal for driving the digital H-bridge circuit generated by S2 in terms of power to meet the power requirement of the piezoelectric ceramic stack in S5. Moreover, the energy conversion efficiency can reach over 90%, and the heat generation of the circuit is greatly reduced compared with the power amplification circuits of medical ultrasonic scalpels commonly used in the current market. Thus, while improving the energy utilization rate, the size of the medical device is made smaller. It should be noted that: during the power amplification process, it is inevitable that the circuit itself will generate heat and consume a part of the energy. If the energy consumed by its own heat generation is low, the conversion efficiency is high.

[0043] S4. The matching filter circuit filters the square wave signal to form a sine wave signal to achieve impedance matching with the piezoelectric ceramic stack in S5. For the piezoelectric ceramic in step S5 to work stably, an impedance circuit matching its electrical characteristics is required. Usually, the impedance matching circuit is directly connected in series or in parallel with the piezoelectric ceramic stack in S5 to ensure that the driving electrical energy output in step S4 is output to the piezoelectric ceramic stack in S5 to the greatest extent and stably.

[0044] S5. The piezoelectric ceramic stack converts the electrical signal output in step S4 into mechanical vibrations with corresponding frequency and amplitude.

[0045] The piezoelectric ceramic stack is a device for realizing energy conversion. It can complete the mutual conversion between mechanical energy (radio frequency, ultrasonic vibration) and electrical energy. When the piezoelectric ceramic stack works at its resonance frequency point, the conversion efficiency from electrical energy to mechanical energy is the highest and it works most stably.

[0046] Preferably, by selecting appropriate filter and impedance matching circuit parameters, the digital square wave output by the digital H-bridge circuit in S3 is converted into a sine wave output with a corresponding frequency.

[0047] As Figure 9 shown in the schematic diagram of the waveform conversion before and after RLC impedance matching, in the figure: (a) converting the PWM wave into a sine wave, (b) converting the SPWM wave into a sine wave. Among them, the solid line waveform is the digital square wave output by the H-bridge circuit, and the dotted line waveform is the output sine waveform after filtering and impedance matching.

[0048] Preferably, by selecting appropriate filter and impedance matching circuit parameters in S4, the energy output by the digital H-bridge circuit in S3 can be basically controlled to be perfectly transferred to the piezoelectric ceramic stack in S5 with very little loss. As Figure 10 can be seen, by selecting appropriate filter and impedance matching circuit parameters, the energy loss before and after the matching filter circuit in S4 is very small.

[0049] Embodiment 2

[0050] Figure 4 This is a circuit schematic diagram of the driving method of the ultrasonic scalpel implemented by the combination of digital and analog circuits in the present invention. Among them:

[0051] DDS: Direct Digital Synthesizer (DDS) refers to the technology that generates a series of digital signals and converts them into analog signals through DA conversion. The implementation solutions include: the DDS synthesis scheme based on MCU or FPGA, and the dedicated DDS integrated chip. Figure 5 It is a schematic diagram of the DDS frequency synthesizer. The DDS can generate waveforms with two different quantization methods: PWM and SPWM.

[0052] Differential amplification: After the DDS output is differentially amplified, there are two waveforms. See Figure 6 and Figure 7 , Figure 6 is the PWM output waveform, Figure 7 is the SPWM output waveform. U1 and U2 are the waveforms output by the differential amplification circuit. From the corresponding waveform directions of U1 and U2, it can be seen that the waveforms are complementary (the phases are exactly opposite). Both waveform U1 and waveform U2 are square wave signals with complementary phases of a pair of waveforms.

[0053] Digital H-bridge circuit: The digital H-bridge circuit consists of 4 switching tubes Q11, Q12, Q21, Q22 and the corresponding drive circuits. To improve the energy conversion efficiency, a digital H-bridge power amplification circuit is used to convert the analog signal into a digital signal.

[0054] Transformer T1: Used to achieve electrical safety isolation.

[0055] Matched filtering circuit: After passing through the matched filtering circuit, the signal is converted from the digital switching signal output by the digital H-bridge circuit back into an analog sine wave.

[0056] The functions of the matched filtering circuit are as follows: First, filtering: filtering the digital switching square wave signal into a sine wave; Second, impedance matching: making the output match the ultrasonic scalpel piezoelectric ceramic stack RZ.

[0057] RH-C: The loop current sampling circuit of the digital H-bridge circuit.

[0058] RL-V: The voltage value and phase sampling circuit of the secondary side of transformer T1.

[0059] RL-C: The current value and phase sampling circuit of the secondary side of transformer T1.

[0060] Figure 8 It is a schematic diagram of the signal conversion path. The signal conversion path includes the following processes:

[0061] First, the DDS generates an analog waveform from digital data;

[0062] Second, the digital H-bridge circuit converts the analog signal into a digital signal;

[0063] Finally, the filter matching circuit converts the digital signal back into an analog signal. As Figure 9 shown is the schematic diagram of waveform conversion before and after RLC impedance matching, where (a) is the schematic diagram of PWM data waveform conversion, and (b) is the schematic diagram of SPWM data waveform conversion.

[0064] Among them, the solid square wave waveform is the output waveform of the digital H-bridge circuit, and the dashed sine waveform is the output waveform after passing through the filter matching circuit. Through this conversion path, the power utilization rate will be greatly improved.

[0065] The present invention proposes a method for driving an ultrasonic scalpel by combining digital and analog circuits, which relates to the technical field of medical ultrasonic scalpels. The DDS technology is used to generate a PWM or SPWM wave data table with a frequency resolution of less than 1 Hz, and the obtained waveform data table is output through a DA conversion chip, thereby generating high and low level signals that can drive the digital H-bridge. Finally, a sine wave is generated through a resonant circuit to drive the piezoelectric ceramic stack of the medical ultrasonic scalpel. Compared with the Class AB amplifier circuit, without reducing the adjustable accuracy of the output sine wave, the energy conversion efficiency of the present invention is greatly improved, a large amount of heat dissipation design is not required, the space size is greatly reduced, the analog design and debugging circuit are reduced, the cost is reduced, and the performance is close to that of the Class AB amplifier circuit.

[0066] The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for driving an ultrasonic surgical knife combining digital and analog circuits, characterized in that: The steps include: S1. Quantify waveform data table using digital technology; S2, outputting the quantized waveform data through the DA conversion chip to generate a driving signal for driving the digital H-bridge circuit; S3, amplifying the driving signal for driving the digital H-bridge circuit generated in step S2 by means of a digital H-bridge circuit, and outputting a driving signal with a square wave waveform; S4, the matched filter circuit filters the square wave signal to form a sine wave signal, thereby achieving impedance matching of the piezoelectric ceramic stack connected to the matched filter circuit; S5. Convert the electrical signal outputted in step S4 into mechanical vibration of corresponding frequency and amplitude through the piezoelectric ceramic stack.

2. The ultrasonic surgical knife driving method combining digital and analog circuits according to claim 1, characterized in that: In step S1, a direct digital frequency synthesizer DDS is used to generate waveform data tables of two different quantization modes, PWM and SPWM, in advance, and a signal of a corresponding output frequency is generated according to the driving requirements of the piezoelectric ceramic stack.

3. The ultrasonic surgical knife driving method combining digital and analog circuits according to claim 2, characterized in that: The waveform output by the direct digital frequency synthesizer DDS after differential amplification is a pair of square wave signals with complementary waveform phases.

4. The ultrasonic surgical knife driving method combining digital and analog circuits according to claim 1, characterized in that: In step S2, the DA conversion chip adopts DA conversion technology, and the frequency resolution of the 10-bit DAC reaches 0.1 Hz.

5. The ultrasonic surgical knife driving method combining digital and analog circuits according to claim 1, characterized in that: In step S4, filtering and impedance matching circuit parameters are selected to convert the square wave signal output by the digital H-bridge circuit in step S3 into a sine wave output of a corresponding frequency.

6. The ultrasonic surgical knife driving method combining digital and analog circuits according to claim 1, characterized in that: In step S4, the filtering and impedance matching circuit parameters are selected so that the energy loss of the front and rear stages of the matching filtering circuit in step S4 is minimized.

7. The ultrasonic surgical knife driving method combining digital and analog circuits according to claim 1, characterized in that: The drive signal conversion path includes: First, the direct digital frequency synthesizer DDS generates an analog waveform from digital data; Secondly, the digital H-bridge circuit converts the analog signal into a digital signal; Finally, the filter matching circuit converts the digital signal into an analog signal.

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