A method for eliminating power distortion of high-frequency electrosurgical knife

Abstract

The present invention discloses a method for eliminating power distortion in a high-frequency electrosurgical unit. The method utilizes a microcontroller (MCU) and a power output circuit. The MCU collects the AD value (Uad) of the output power voltage and the AD value (Iad) of the feedback current from the power output circuit. The MCU then adjusts the pulse duty cycle (PWM) of the control signal based on the feedback values ​​(Uad and Iad). The power output circuit then outputs different power levels based on the input PWM. This method can reduce or even eliminate distortion caused by impedance variations, ensuring effective electrosurgical coagulation.

Description

Technical Field

[0001] The present invention relates to a method for eliminating power distortion of a high-frequency electric knife. Specifically, when the impedance of the high-frequency electric knife changes, power output distortion is caused due to hardware characteristics. This method can eliminate such power distortion. Background Art

[0002] A high-frequency electrosurgical unit is an electrosurgical device that replaces mechanical scalpels for tissue cutting. It heats tissue when in contact with the body through the high-frequency, high-voltage current generated by the active electrode tip, achieving the purpose of cutting and coagulation.

[0003] The output power of a high-frequency electrosurgical unit should be as stable as possible. When the power supply voltage fluctuates or the load changes, the output power should remain within the specified range. Otherwise, during surgery, the cutting and coagulation effects may be poor, or the tissue may be scorched or even burned.

[0004] To ensure accurate power output, the power is typically calibrated from small to large according to different modes under standard load conditions, and this calibration data is stored in an EEPROM (Electrically Erasable Programmable Read-Only Memory). After normal startup, the corresponding calibration data is read according to the selected mode. When the electrosurgical unit is started, the measured power is calculated based on the calibration data, and the power output is adjusted based on the set power and measured power. This method accurately measures the output power under standard loads, but it can be inaccurate under non-standard impedances, resulting in errors in the output power. Summary of the Invention

[0005] In order to ensure that the output power does not change due to impedance changes, the present invention designs a method for eliminating power distortion of a high-frequency electrosurgical unit. This method can reduce or even eliminate the distortion caused by impedance changes to ensure the coagulation effect of the electrosurgical unit.

[0006] The technical solution of the present invention is: a method for eliminating power distortion of a high-frequency electric knife, using a microcontroller MCU and a power output circuit; the microcontroller MCU is responsible for collecting the AD value Uad of the feedback voltage and the AD value Iad of the feedback current of the output power from the power output circuit, and then adjusting the pulse duty cycle PWM of the control signal according to the feedback Uad and Iad. The power output circuit outputs different powers according to different input PWM.

[0007] Furthermore, the load impedance R is the impedance value of the load when the electrosurgical unit is working, and the calculation method is as follows: let the AD value of the load impedance be represented by Rad, and Rad = Uad / Iad, where Uad and Iad are acquired by the MCU; under the condition of the same target output power, multiple points are calibrated at different impedances to obtain a curve of Rad and R. Rad and R satisfy an approximately linear law, and R can be calculated through Rad;

[0008] By calibrating different target output powers at rated load through the calibration mode, the rated load curve Uad-Ur and the rated load curve Iad-Ir are obtained. Through the Rad-R curve, Uad-Ur curve, Iad-Ir curve, and the collected Uadi and Iadi, Ri, Uci, and Ici can be calculated, and then Uri and Iri are obtained, Pri = Uri*Iri, and then the output PWM is adjusted according to the current actual power and target power; the r suffix indicates the actual value, the c suffix indicates the measured value, and the i suffix indicates the current value.

[0009] Furthermore, the calculation of the distortion coefficient of voltage and current is carried out as follows:

[0010] Let the calculated voltage distortion coefficient relationship be m = Ur / Uc, the current distortion coefficient relationship be n = Ir / Ic, and the actual output power relationship be Pr = (m * Uc) * (n * Ic);

[0011] Where: Ur represents the actual output voltage, Ir represents the actual output current, Uc represents the voltage measurement value calculated based on the rated load curve Uad-Ur, and Ic represents the current measurement value calculated based on the rated load curve Iad-Ir;

[0012] When the target output power is the same, multiple points are calibrated under different impedances to obtain two curves, namely Rm and Rn curves.

[0013] Substituting the load impedance Ri into the two curves of Rm and Rn, we can get the distortion coefficients mi and ni. Combining them with the previously calculated Uci and Ici, we can get Uri = mi*Uci, Iri = ni*Ici; then Pri = Uri*Iri;

[0014] With Pri and the known target power setting, a proportional control scheme can be used to adjust PWM to make the actual output close to the target setting value.

[0015] Furthermore, when calculating the Rm and Rn curves, if the ad value exceeds the calibration value range, the linear calculation is performed according to the boundary curve and the over-limit processing is done.

[0016] The present invention provides a method for eliminating power distortion in a high-frequency electrosurgical unit, adjusting power output in real time based on changes in load impedance to achieve stable power output. This method can reduce or even eliminate distortion caused by impedance changes, ensuring effective electrosurgical coagulation. It can also effectively compensate for power output distortion caused by hardware distortion. It can also maintain constant system power output, ensuring stable operation of the high-frequency electrosurgical unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Simplify the block diagram for the system;

[0018] Figure 2 is the power output distortion diagram;

[0019] Figure 3 is the curve relationship diagram of Rad and R;

[0020] Figure 4 is the curve relationship diagram of Uad and Ur;

[0021] Figure 5 is the curve relationship diagram of Iad and Ir;

[0022] Figure 6 is the relationship diagram between load impedance and voltage distortion coefficient m;

[0023] Figure 7 is the relationship diagram between load impedance and current distortion coefficient n;

[0024] Figure 8 Rad-R curve calibrated at different powers. DETAILED DESCRIPTION

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] The simplified system block diagram of the power regulation part of the system is as follows Figure 1 As shown, the main components include a microcontroller (MCU) and a power output circuit. The MCU is responsible for collecting the AD value of the output power feedback voltage (Uad) and the AD value of the feedback current (Iad) from the power output circuit. It then adjusts the pulse width modulation (PWM) of the control signal based on the feedback Uad and Iad. The power output circuit outputs different amounts of power according to the input PWM.

[0027] This method has two core ideas: one is the calculation of load impedance, and the other is the calculation of voltage and current distortion coefficients.

[0028] First, let's look at the calculation of load impedance.

[0029] like Figure 2The following figure shows the actual output power at different impedances when the target output power is set to 50W in the dot coagulation mode. The main reason for the output distortion is that the sensor samples the same AD at different impedances, but the actual power is inconsistent. In short, the distortion of the AD sampling circuit leads to the distortion of the power output.

[0030] Because power output is dependent on load impedance variations, eliminating errors caused by this distortion requires measuring the load impedance (R) during operation. This assumes the AD value of the load impedance, denoted by Rad. Rad is not a directly derived value but rather is derived from the Uad and Iad values ​​collected by the MCU. Equation 1: Rad = Uad / Iad.

[0031] By calibrating multiple points at different impedances while maintaining the same target output power, a Rad-R curve can be generated. This allows the MCU to calculate Rad from the collected Uad and Iad data during electrosurgical operation, and thus the current load impedance, R. This method is only effective if Rad and R exhibit a near-linear relationship at the same power output, allowing R to be calculated from Rad. Multiple tests have confirmed that this method can be used to approximate the current load impedance, R, of electrosurgical equipment in this system, and that this Rad-R curve can be used to approximate the Rad-R curve for adjacent power levels.

[0032] Table 1 shows the measured data in point coagulation mode at 100, 200, 500, 1000, and 2000 Ω. The system's MCU has a 10-bit AD sampling resolution. Rad is calculated by dividing Uad by Iad and amplifying the result by 256. The actual voltage (Ur) and actual current (Ir) are calculated using the impedance and power formulas, amplified by 10 and 1000 times, respectively. Once the calibrated impedance and power are determined, the actual voltage and current values ​​can be directly calculated using the power-resistance relationship, which will be used in subsequent calculations. Figure 3 is the Rad-R curve.

[0033] Table 1

[0034] Serial number 0 1 2 3 4 impedance 100 200 500 1000 2000 Ur 707 1000 1581 2236 3162 Ir 707 500 316 224 158 Uad 60 76 118 165 238 Iad 308 214 131 90 67 PWM 379 326 304 323 382 Rad 50 91 231 469 909

[0035] Table 2 shows the data recorded at eight points in point coagulation mode, calibrated from 1W to 100W, at a rated load of 500Ω. The actual voltage (Ur) and actual current (Ir) are calculated using the impedance and power formulas, amplified by 10x and 1000x, respectively. Figure 4 is the Uad-Ur curve, Figure 5 It is the Iad-Ir curve.

[0036] Table 2

[0037] Serial number 0 1 2 3 4 5 6 7 power 1 5 20 40 50 60 80 100 Ur 224 500 1000 1414 1581 1732 2000 2236 Ir 45 100 200 283 316 346 400 447 Uad 2 15 64 102 118 130 156 178 Iad 1 25 76 114 131 144 170 193 PWM 52 110 203 274 304 328 373 413

[0038] In all the following names, the suffix "r" indicates the actual value, the suffix "c" indicates the measured value, the suffix "i" indicates the current value, and the suffix "s" indicates the set value.

[0039] During normal operation, the MCU collects Uadi and Iadi data, uses Equation 1 above to calculate Radi, and then uses the Rad-R curve to calculate the current load resistance Ri. The measured voltage Uci can be calculated from the Uad-Ur curve. The measured current Ici can be calculated from the Iad-Ir curve. Because the Uad-Ur and Iad-Ir curves are calibrated at a rated load of 500Ω, the values ​​calculated using these two curves are distorted when the actual impedance is not 500Ω. Therefore, they represent only measured values, not actual values.

[0040] Currently, using the Rad-R, Uad-Ur, and Iad-Ir curves, along with the collected Uadi and Iadi, we can calculate Ri, Uci, and Ici. The key is to find Uri and Iri, Pri = Uri * Iri, and then adjust the output PWM based on the current actual power and target power.

[0041] Finally, let’s look at the calculation of the distortion coefficient of voltage and current.

[0042] Assuming the calculated voltage distortion coefficient equation (2) is m = Ur / Uc, and the current distortion coefficient equation (3) is n = Ir / Ic, the actual output power equation is Pr = (m * Uc) * (n * Ic). Ur represents the actual output voltage, Ir represents the actual output current, Uc represents the voltage measurement value calculated based on the rated load curve (Uad - Ur), and Ic represents the current measurement value calculated based on the rated load curve (Iad - Ir).

[0043] Because the rated load of the electrosurgical unit in coagulation mode is 500Ω, the distortion is relative to the load of 500Ω. Therefore, when the load is 500Ω, the distortion coefficient is 1. When the load is not 500Ω, the distortion coefficient calculation process is as follows.

[0044] Refer to the data in Table 1 and Table 2, assuming we need the voltage distortion coefficient at 100 ohms. First, find the Uad of 50W calibrated at 100Ω is 60, and substitute it into Figure 4The calculated Uc is approximately 959 (unit: 0.1V) from the Uad-Ur curve. Table 1 shows that the actual voltage Ur is 707 (unit: 0.1V), so m = Ur / Uc = 707 / 959. The result is amplified by 128 times and then rounded to 94, which is one of the distortion coefficients required for our system calculations.

[0045] Suppose we want to find the current distortion coefficient when the resistor is 1000 ohms. First, find the Iad of 50W when the resistor is 1000 ohms, which is 90. Substitute it into Figure 5 The Iad-Ir curve shows that the calculated Ic is approximately 231 (unit: 0.001A). Table 1 shows that the actual current Ir is 224 (unit: 0.001A), so n = Ir / Ic = 224 / 231. The result is first amplified by 128 times and then rounded to 124.

[0046] Through the above method, we can obtain two curves, namely Rm and Rn curves. When calculating the curve, if the ad value exceeds the calibration value range, it is calculated according to the linearity of the boundary curve and the over-limit treatment is done. The calculated data is shown in Table 3 (the distortion coefficient of voltage and current when the output is set to 50W (magnified 128 times)). The curve is as follows Figure 6 and Figure 7 shown.

[0047] Table 3

[0048] impedance 100 200 500 1000 2000 Voltage distortion coefficient m 94 113 128 136 140 Current distortion coefficient n 132 130 128 124 111

[0049] After obtaining these two curves, we can bring the previously calculated Ri into Figure 6 and Figure 7 The two curves can be used to obtain the distortion coefficients mi and ni. Combined with the previously calculated Uci and Ici, we can obtain Uri = mi*Uci and Iri = ni*Ici. Then Pri = Uri*Iri.

[0050] Once Pri and the target power setting are known, a proportional control scheme can be used to adjust PWM to make the actual output close to the target setting value.

[0051] In actual use, the rated power of the dot condenser is 100W. Because the Rad-R curve is different under different power output conditions, and all calculations of our system are based on accurate resistance calculations, in order to reduce the error caused by impedance calculations, it is necessary to calibrate two curves under different impedances at 50W and 100W. When setting different target powers, the currently required curve is calculated. The calculation method of this curve is that when it is less than 50W, the parameters of the 50W Rad-R curve are used. When it is greater than 50W and less than 100W, the Rad under different impedances is calculated using interpolation calculations, and the new data obtained represents the currently used Rad-R curve. For reference, Figure 8 As shown, the difference between the 100W and 50W curves in the dot-coagulation mode is intentionally exaggerated to demonstrate the effect. The voltage and current compensation coefficients measured at 50W are sufficient to meet system requirements. However, using the same Rad-R calculation method for sampling has been shown to produce less than ideal results.

[0052] In actual systems, the maximum output power, voltage, and current of the hardware must be considered. If the hardware does not support these, the system may be saturated during calibration, or the data may be severely distorted. The saved data will be meaningless and may lead to larger system errors and instability.

[0053] Example 1:

[0054] Assume that the rated power of one mode of the electrosurgical unit is 100W and the standard impedance is 500Ω.

[0055] (1) Calibration

[0056] After entering calibration mode, this mode requires calibration at 8 points at 500Ω, and 8 points at 100Ω, 200Ω, 1000Ω, and 2000Ω. The calibration power is shown in Table 4. Each calibration requires the required PWM, Uad, and Iad to be saved in EEPROM.

[0057] Table 4

[0058] Serial number 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 impedance 500 500 500 500 500 500 500 500 100 100 200 200 1000 1000 2000 2000 power 1 5 20 40 50 60 80 100 50 100 50 100 50 100 50 100

[0059] (2) Normal operation

[0060] After selecting the specified mode, when the start button is pressed to output power, the data of the current mode saved in the EEPROM is read out. If there is enough RAM, these data can be read out at the same time when the device is turned on to increase the startup speed.

[0061] The Rad-R curve, Uad-U curve, Iad-I curve, Rm curve, and Rn curve are calculated according to the set power.

[0062] After startup, the system first outputs a calibrated PWM signal under a calibrated load. Then, at regular intervals, it collects Uadi and Iadi data, calculates Radi, and calculates the current load impedance Ri based on the Rad-R curve. The current voltage Uci is calculated based on the Uad-Ur curve, and the current current Ici is calculated based on the Iad-Ir curve. The voltage distortion compensation coefficient mi and the current distortion compensation coefficient ni are calculated based on the Rm curve. The actual voltage Uri is calculated from mi and Ui, and the actual current Iri is calculated from ni and Ii. The current power Pri = Uri * Iri. The PWM output is adjusted based on the current actual power and the target power setting. The next acquisition and PWM adjustment cycle then begins.

[0063] This method can effectively compensate for the power output distortion caused by hardware distortion, and can make the system output constant power, so that the high-frequency electrosurgical unit can operate in a stable output state.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for eliminating power distortion of a high-frequency electrosurgical unit, characterized by: A microcontroller (MCU) and a power output circuit are used; the MCU is responsible for collecting the AD value Uad of the output power feedback voltage and the AD value Iad of the feedback current from the power output circuit, and then adjusting the pulse duty cycle PWM of the control signal according to the feedback Uad and Iad. The power output circuit outputs different powers according to different input PWM values; The load impedance R is the impedance value of the load when the electrosurgical unit is working. The calculation method is as follows: Let the AD value of the load impedance be represented by Rad, and Rad = Uad / Iad, where Uad and Iad are acquired by the MCU. Under the condition of the same target output power, multiple points are calibrated at different impedances to obtain a curve of Rad and R. Rad and R satisfy an approximately linear law, and R can be calculated from Rad. The rated load curve Uad-Ur and the rated load curve Iad-Ir are obtained by calibrating different target output powers at rated load through the calibration mode. Ri, Uci, and Ici can be calculated through the Rad-R curve, Uad-Ur curve, and Iad-Ir curve, as well as the collected Uadi and Iadi. Then, Uri and Iri are obtained, Pri = Uri * Iri, and then the output PWM is adjusted according to the current actual power and target power. The r suffix indicates the actual value, the c suffix indicates the measured value, and the i suffix indicates the current value. Including the calculation of the distortion coefficient of voltage and current, the specific calculation method is as follows: Let the calculated voltage distortion coefficient relationship be m = Ur / Uc, the current distortion coefficient relationship be n = Ir / Ic, and the actual output power relationship be Pr = (m * Uc) * (n * Ic); Where: Ur represents the actual output voltage, Ir represents the actual output current, Uc represents the voltage measurement value calculated based on the rated load curve Uad-Ur, and Ic represents the current measurement value calculated based on the rated load curve Iad-Ir; When the target output power is the same, multiple points are calibrated under different impedances to obtain two curves, namely Rm and Rn curves. Substituting the load impedance Ri into the two curves of Rm and Rn, we can get the distortion coefficients mi and ni. Combining them with the previously calculated Uci and Ici, we can get Uri = mi*Uci, Iri = ni*Ici; then Pri = Uri*Iri; With Pri and the known target power setting, a proportional control scheme can be used to adjust PWM to make the actual output close to the target setting value.

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