Pulse system with clamping and freewheeling protection

Abstract

The invention discloses a pulse system with clamping and freewheeling protection functions, comprising a main control module, a sampling and processing module, a probe located on a target cell tissue, an IGBT switch component, a pulse energy storage capacitor and a clamping and freewheeling protection circuit; the clamping and freewheeling protection circuit comprises a diode D, a first resistor R1, a capacitor C, a second resistor R2 and an SCR array switch component; compared with the prior art, the invention has the following advantages: the invention adds an SCR array switch component on the basis of an original RCD circuit, and by controlling the start-up time of the RCD circuit, in addition to passive freewheeling through the diode D, active freewheeling can also be performed by pre-storing energy through the capacitor C, thereby realizing the clamping function and not affecting the characteristics of the output square wave.

Description

Technical Field

[0001] The present invention relates to the field of medical device electronics, and in particular to a pulse system with clamping and freewheeling protection functions. Background Art

[0002] The microsecond high-voltage square wave pulse source in the pulse system is mainly used in the medical field and can output square wave pulses for patient treatment. In the clinical treatment or test of irreversible electroporation ablation of biological cell tissues, unpredictable overcurrent or short circuit may occur between electrodes (probes), and fast and effective protection must be performed. In work, it is necessary to take into account the square wave characteristics during normal operation, and to ensure that the voltage between the two poles is limited to a safe range when the switch is rigidly turned off due to overcurrent or short circuit of the load. Traditionally, RCD circuits are used to protect the switch, but the capacitor C in the RCD circuit has a large capacity. During the normal shutdown process of the switch (MOSFET or IGBT), part of the energy can still be transferred to the load through the capacitor C, causing the square wave pulse waveform to be severely tailed. Therefore, it is very important to obtain a pulse system with a fast protection function that does not affect the square wave characteristics. Summary of the invention

[0003] To solve at least one of the above problems, the present invention provides a pulse system with clamping and freewheeling protection functions, including a main control module, a sampling and processing module, a probe located on a target cell tissue, an IGBT switch assembly, a pulse energy storage capacitor and a clamping and freewheeling protection circuit, wherein the clamping and freewheeling protection circuit includes a diode D, a first resistor R1, a capacitor C, a second resistor R2 and an SCR array switch assembly, wherein the diode D and the first resistor R1 are connected in parallel, and then the capacitor C is connected in series to the positive electrode port S1 of the SCR array switch assembly; the negative electrode port S2 of the SCR array switch assembly is connected to the first resistor R1 after being connected to the second resistor R2, and the negative electrode port S2 is connected to the anode of the diode after being connected to the second resistor R2; the COM end of the SCR array switch assembly is connected to the negative end of the IGBT switch assembly; the positive electrode of the pulse energy storage capacitor is connected to the positive end of the IGBT switch assembly, and its negative electrode is connected to the anode of the diode D; the positive electrode of the probe is connected to the COM end, and the negative electrode is connected to the sampling and processing module and the second resistor R2, the sampling and processing module is electrically connected to the main control module, and the main control module controls the operation of the above devices to output a square wave.

[0004] The SCR array switch component is a multi-stage series-connected thyristor. The SCR array switch component used in the present invention includes two groups of series-connected thyristors SS1 and SS2. The cathode of thyristor SS1 is connected to the anode of thyristor SS2, and the connection ends of the two are connected to a COM terminal. The anode of thyristor SS1 is the positive terminal of S1, and the cathode of thyristor SS2 is the negative terminal of S2.

[0005] The sampling and processing module includes a signal processing module and a current probe. The current probe is arranged on the line where the probe is connected to the second resistor R2, and transmits the line current information to the signal processing module. The signal processing module is controlled by the main control module to output the shutdown signal Sig1 and the opening signal Sig2.

[0006] It also includes a pulse capacitor residual pressure discharge module, which is connected in parallel with the pulse energy storage capacitor and is controlled by the main control module. It also includes a constant process control linear high voltage power supply module, which is connected in parallel with the pulse energy storage capacitor to power the above modules and circuits.

[0007] The capacitor C is a high-voltage film capacitor. The diode D is composed of multiple high-voltage fast recovery diodes connected in series. The first resistor R1 is a non-inductive wire-wound power resistor. The second resistor R2 is a non-inductive wire-wound power resistor.

[0008] Compared with the prior art, the advantages of the present invention are as follows: the present invention adds an SCR array switch component on the basis of the original RCD circuit, and by controlling the start-up time of the RCD circuit, in addition to the passive freewheeling through the diode D, the capacitor C can also pre-store energy for active freewheeling, thereby realizing the clamping function without affecting the characteristics of the output square wave. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of the circuit structure of the present invention;

[0010] Figure 2 It is a waveform diagram of the present invention under the SRCD mode;

[0011] Figure 3 It is a waveform diagram composed of low loop area and diode D. DETAILED DESCRIPTION

[0012] In order to enable those skilled in the art to better understand the present invention, and thus to more clearly define the scope of the protection claimed in the present invention, the present invention is described in detail below with respect to certain specific embodiments of the present invention. It should be noted that the following are only certain specific implementations of the present invention, which are only part of the embodiments of the present invention, wherein the specific and direct description of the relevant structures is only for the convenience of understanding the present invention, and each specific feature does not naturally and directly limit the scope of implementation of the present invention.

[0013] The present invention is applicable to the following environments: in biological effect research, the pulse current required is small, not exceeding 50A, and the peak voltage caused by L*di / dt can be ignored when the switch is normally turned off. The following will introduce a pulse system with clamping and freewheeling protection functions, which can achieve no redundant power consumption during normal operation without affecting the main pulse characteristics.

[0014] Referring to the accompanying drawings, the present invention adopts the following technical solution: a pulse system with clamping and freewheeling protection functions, including a main control module ( Figure 1 CPU shown in ), sampling processing module, probe located on the target cell tissue, IGBT switch component ( Figure 1 IGNT high-voltage, high-current, ultra-fast array switch components), pulse energy storage capacitors ( Figure 1 The high-voltage large-capacity pulse capacitor in the embodiment of the present invention) and the clamping and freewheeling protection circuit, the clamping and freewheeling protection circuit includes a diode D, a first resistor R1, a capacitor C, a second resistor R2 and an SCR array switch component. The diode D and the first resistor R1 are connected in parallel, and then the capacitor C is connected in series to the S1 positive port of the SCR array switch component; the S2 negative port of the SCR array switch component is connected to the second resistor R2 and then connected to the first resistor R1, and the S2 negative port is connected to the second resistor R2 and then connected to the anode of the diode; the COM end of the SCR array switch component is connected to the negative end of the IGBT switch component; the positive electrode of the pulse energy storage capacitor is connected to the positive end of the IGBT switch component, and its negative electrode is connected to the anode of the diode D; the positive electrode of the probe is connected to the COM end, and the negative electrode is connected to the sampling and processing module and the second resistor R2. The sampling and processing module is electrically connected to the main control module, and the main control module controls the operation of the above devices and outputs a PWM wave. The SCR array switch is composed of multiple stages of thyristors connected in series. The SCR array switch assembly used in this embodiment includes two groups of thyristors SS1 and SS2 connected in series. The cathode of thyristor SS1 is connected to the anode of thyristor SS2, and the connection ends of the two are connected to the COM terminal. The anode of thyristor SS1 is the positive terminal of S1, and the cathode of thyristor SS2 is the negative terminal of S2.

[0015] The sampling processing module includes a signal processing module ( Figure 1 The sampling signal processing module in the circuit) and the current probe are arranged on the line where the probe is connected to the second resistor R2, and the line current information is transmitted to the signal processing module, and the signal processing module is controlled by the main control module to output the shutdown signal Sig1 and the opening signal Sig2. It also includes a pulse capacitor residual pressure discharge module, which is connected in parallel with the pulse energy storage capacitor and is controlled by the main control module. It also includes a constant process control linear high voltage power supply module, which is connected in parallel with the pulse energy storage capacitor to power the above modules and circuits.

[0016] The capacitor C is a high-voltage film capacitor. The diode D is composed of multiple high-voltage fast recovery diodes connected in series. The first resistor R1 is a non-inductive wire-wound power resistor. The second resistor R2 is a non-inductive wire-wound power resistor.

[0017] The present invention adds an SCR array switch component to the RCD circuit. Since the SCR array switch component has a very small junction capacitance and is of medium power type, the high-frequency component of the square wave pulse can be isolated to the greatest extent without affecting the pulse characteristics. The SCR array switch component is composed of a plurality of thyristors connected in series, which not only improves the total withstand voltage of the high-voltage switch, but also reduces the junction capacitance of the entire switch component.

[0018] The COM end of the SCR array switch component is connected to the negative end of the IGBT component. After the SCR array switch is triggered, its on and off depends on the main circuit in which it is located, and there will be no rigid shutdown, thereby ensuring the safety of its operation. There is no need to design a protection circuit for the SCR array switch component in order to protect the IGBT component, which makes the circuit structure simpler and reduces production costs.

[0019] like Figure 1 As shown in the figure, the direction of the arrow is the main current flow direction. The two points at a specific distance on the tissue cell can be considered as pure resistance. The fast turn-on characteristics of the high-voltage, high-current, ultra-fast array switch component IGBT can be used to obtain an approximate step-up rising waveform. The tailing of the RC exponential discharge waveform during its rigid shutdown can be used to obtain an approximate step-down waveform, and a pulse approximate to a square wave can be obtained.

[0020] When the pulse source is working normally, the peak voltage is negligible, and the safety of the IGBT will not be threatened. However, if the resistance value between the electrodes (probes) located in the tissue cells is too low or short-circuited, the entire circuit will flow through a pulse current of up to kiloamperes. After a delay of several microseconds, the sampling signal processing module will issue a shutdown signal Sig1. During the rigid shutdown of the IGBT switch, the voltage across its two ends will theoretically rise quickly, and under the action of the line self-inductance, it will quickly exceed the safety voltage. However, at almost the same time, the SCR array switch component is turned on, and the capacitor C will be connected to the circuit. The capacitor C is pre-charged to the power supply voltage. By utilizing the characteristic that the capacitor voltage cannot be mutated, the negative terminal potential of the IGBT can be stabilized, which is equivalent to the clamping function; the capacitor C discharges through the original circuit (equivalent to active continuous current), which curbs the speed of the original circuit current reduction, that is, reduces the rate of change of di / dt; the voltage suppressed to a certain extent on the line inductance can still be passively continuous through the diode D and the capacitor C, and the capacitor C is reversely charged, which is equivalent to the discharge of the capacitor C.

[0021] When the resistance of biological tissue is too low or short-circuited, the current sampling module immediately sends out a signal Sg1 to turn off the IGBT switch component and a signal Sg2 to turn on the SCR switch component after receiving the overcurrent signal. Since the response speed of the IGBT switch is significantly faster than that of the SCR switch, the timing between Sg1 and Sg2 needs to be appropriately adjusted to match the circuit.

[0022] The COM end of the SCR array switch component in the clamping and freewheeling protection circuit is connected to the second resistor through the switch and then connected to the negative branch of the power supply. The function is: if the tissue cell is completely short-circuited and overcurrent occurs, the discharge current of the capacitor C will completely flow through the main circuit. At this time, even if a very short overcurrent flows through the tissue cell, there is no voltage and no excessive energy will be applied; if the tissue cell only has a small overcurrent due to a decrease in resistance, the discharge current of the capacitor C will be fully transferred to the low-resistance branch, and the cell tissue (load) circuit will be bypassed, which plays a role in protecting the tissue cells. This branch is a common part with the original circuit at the input and output ends, so it can also curb the change rate of the original circuit current.

[0023] like Figure 2 As shown in the figure, the black waveform is the voltage waveform at both ends of the IGBT high-voltage, high-current, ultra-fast array switch component when it is shut down due to overcurrent. The maximum is 3.13kV, and the peak voltage is limited to 1.5kV. From the analysis of the entire waveform trend, it can be considered that the voltage at both ends of the IGBT switch never exceeds the power supply voltage, and it is in an absolutely safe state. Even the IGBT switch does not need to leave any margin in the selection, which greatly saves costs. The gray waveform is the corresponding short-circuit current waveform, and its peak value is as high as 1.41kA. This value is limited by the resistor Rs. We can see that after the voltage spike, the current di / dt amplitude is significantly slowed down, and the voltage at both ends of the IGBT switch rises slowly; the above-mentioned numerical values ​​are not shown in the figure, and are described in text.

[0024] The RCD mode can also be achieved in theory Figure 2 However, this solution affects the normal working state, that is, the waveform is severely tailed, that is, the square wave is not square, and there is a certain degree of power loss.

[0025] like Figure 3 As shown, the gray waveform at the top represents the voltage across the IGBT high-voltage, high-current, ultra-fast array switch component when the high current is turned off. There is an overvoltage of 560V, that is, △560.0V in the figure. The gray waveform is the short-circuit current waveform. It can be seen that the current has dropped at an almost fixed speed. Figure 3 Although the square wave is not affected in the mode shown, the difficulty of structural implementation and the actual test results are somewhat different from the SRCD mode provided by the present invention, and are not operational.

[0026] It is worth mentioning that due to the internal structure limitations of the pulse source, when laying out the clamping and freewheeling protection circuits, cables of a certain length must be used for connection. This will introduce a small amount of inductance, especially at the negative end of the power supply. When there are clamping and freewheeling protection circuits, although the IGBT switch has a rapid spike voltage rise at both ends in the early stage of shutdown, the amplitude will be limited to a safe range, and the voltage will never exceed the power supply voltage at any time, thus playing a protective role. The early stage of shutdown is the critical point of shutdown, and the voltage across the IGBT switch is still zero at this time.

[0027] The above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A pulse system with clamping and freewheeling protection functions, characterized in that: It includes a main control module, a sampling and processing module, a probe located on the target cell tissue, an IGBT switch component, a pulse energy storage capacitor, and a clamping and freewheeling protection circuit. The clamping and freewheeling protection circuit comprises a diode D, a first resistor R1, a capacitor C, a second resistor R2 and an SCR array switch component. The diode D and the first resistor R1 are connected in parallel and then connected in series with the capacitor C to the positive terminal S1 of the SCR array switch component. The negative terminal of S2 of the SCR array switch assembly is connected to the second resistor R2 and then connected to the first resistor R1, and the negative terminal of S2 is connected to the second resistor R2 and then connected to the anode of the diode; The COM terminal of the SCR array switch assembly is connected to the negative terminal of the IGBT switch assembly; the positive electrode of the pulse energy storage capacitor is connected to the positive terminal of the IGBT switch assembly, and its negative electrode is connected to the anode of the diode D; The positive pole of the probe is connected to the COM terminal, and the negative pole is connected to the sampling processing module and the second resistor R2. The sampling processing module is electrically connected to the main control module. The main control module controls the sampling processing module, the probe located on the target cell tissue, the IGBT switch component, the pulse energy storage capacitor, and the clamping and freewheeling protection circuit to output a square wave. The SCR array switch component includes a multi-stage series-connected thyristor. The multi-stage series-connected thyristor uses two groups of thyristors SS1 and SS2. The cathode of the thyristor SS1 is connected to the anode of the thyristor SS2, and the connection end of the two leads to the COM terminal. The anode of the thyristor SS1 is the positive terminal of S1, and the cathode of the thyristor SS2 is the negative terminal of S2.

2. The pulse system with clamping and freewheeling protection functions according to claim 1, characterized in that: The sampling processing module includes a signal processing module and a current probe. The current probe is arranged on a line connecting the probe to the second resistor R2, and transmits the line current information to the signal processing module. The signal processing module is controlled by the main control module to output a shutdown signal Sig1 and an opening signal Sig2.

3. The pulse system with clamping and freewheeling protection functions according to claim 2, characterized in that: It also includes a pulse capacitor residual pressure discharge module, which is connected in parallel with the pulse energy storage capacitor and is controlled by the main control module.

4. The pulse system with clamping and freewheeling protection functions according to claim 3, characterized in that: It also includes a constant process-controlled linear high-voltage power supply module, which is connected in parallel with the pulse energy storage capacitor to supply power to the above modules and circuits.

5. The pulse system with clamping and freewheeling protection functions according to claim 1, characterized in that: The capacitor C is a high voltage film capacitor.

6. The pulse system with clamping and freewheeling protection functions according to claim 1, characterized in that: The diode D is composed of multiple stages of high-voltage fast recovery diodes connected in series.

7. The pulse system with clamping and freewheeling protection functions according to claim 1, characterized in that: The first resistor R1 is a non-inductive wire-wound power resistor.

8. The pulse system with clamping and freewheeling protection functions according to claim 1, characterized in that: The second resistor R2 is a non-inductive wire-wound power resistor.

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