CN115282481A - Ascending wave external cardiac defibrillator and control method thereof - Google Patents
Ascending wave external cardiac defibrillator and control method thereof Download PDFInfo
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- CN115282481A CN115282481A CN202210965512.6A CN202210965512A CN115282481A CN 115282481 A CN115282481 A CN 115282481A CN 202210965512 A CN202210965512 A CN 202210965512A CN 115282481 A CN115282481 A CN 115282481A
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- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
- A61N1/39—Heart defibrillators
- A61N1/3904—External heart defibrillators [EHD]
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- A—HUMAN NECESSITIES
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- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N1/00—Electrotherapy; Circuits therefor
- A61N1/18—Applying electric currents by contact electrodes
- A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
- A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
- A61N1/39—Heart defibrillators
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- A61N1/3937—Monitoring output parameters
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Abstract
The invention belongs to the technical field of medical instruments, and particularly relates to an ascending wave external cardiac defibrillator and a control method thereof. A kind of external cardiac defibrillator of the rising wave, including the intensity control circuit, have the first capacitor and two defibrillation outputs; the intensity control circuit further has: the drain electrode of the first field effect transistor is connected with one end of the first capacitor; the anode of the first diode is connected with the other end of the first capacitor, and the cathode of the first diode is connected with the source electrode of the first field effect transistor; one end of the inductor is connected with the source electrode of the first field effect transistor; one end of the second capacitor is connected with the other end of the first capacitor; a source electrode of the second field effect transistor is connected with the other end of the first capacitor; and the anode of the second diode is respectively connected with the other end of the inductor and the drain electrode of the second field effect transistor, and the cathode of the second diode is connected with the other end of the second capacitor. The invention controls the defibrillation current through the intensity control circuit to form the rising defibrillation wave, more conforms to the response characteristic of the myocardial cells, improves the defibrillation success rate and reduces the damage of the current to the myocardial cells.
Description
Technical Field
The invention belongs to the technical field of medical instruments, and particularly relates to an ascending wave external cardiac defibrillator and a control method thereof.
Background
External defibrillators apply high-intensity electrical pulses to the patient's skin (external electrodes) or exposed heart (internal electrodes) through electrodes, and pulse currents are passed through the heart to eliminate arrhythmias and restore sinus rhythm. It can be used for emergency treatment of patients with ventricular fibrillation, ventricular tachycardia, and suspected cardiac arrest. Successful defibrillation requires the delivery of brief electrical pulses of sufficient current and duration to the heart to terminate ventricular fibrillation while reducing the damage to the myocardial cells from the defibrillation current.
Modern external defibrillators employ a dc defibrillation technique based on RC charging and discharging, where R is the load of the defibrillator, i.e. the thoracic impedance of the patient, and C is the capacitance of the capacitor used by the defibrillator. The time constant τ = RC is about 10ms. During discharge, the voltage on the capacitor decays exponentially over time. The capacitor voltage drops to 36.8% of the initial value for a time constant. With two time constants, the capacitor voltage will drop to 13% of the initial value.
The defibrillation waveform is a curve of voltage or current of two output electrode ends of the defibrillator changing along with time when discharging cardiac shock, and is one of key technologies for determining defibrillation efficiency. Literature studies have shown the effectiveness of different waveforms. Factors that affect defibrillation are mainly waveform shape, pulse width, current polarity, etc.
Almost all new defibrillators in the current market use biphasic defibrillation waveforms. Among the various types of biphasic waves, those commonly recognized as truncated exponential biphasic waves, biphasic square waves, and current profiles on these waveforms are not able to rise with discharge time.
In the research of the implantable defibrillator, people evaluate myocardial damage and necrosis caused by defibrillation shock in three aspects of electrophysiological indexes, histological analysis and biochemical indexes, and the result shows that when the same energy is adopted for the defibrillation shock, the biphasic ascending wave defibrillation is much smaller than the myocardial damage caused by the biphasic exponential truncated wave defibrillation, the defibrillation threshold is also obviously reduced, and the initial success rate is obviously improved. The reason is that the intracellular fluid and the extracellular fluid have good conductivity, the cell membrane contains phospholipid, the conductivity is poor, and the myocardial cell is equivalent to an RC circuit, so that the corresponding curve of the myocardial cell to defibrillation electric pulse is a rising exponential wave. The ascending defibrillation waveform follows the response trend of the myocardial cells.
Either implantable defibrillators or external defibrillators utilize electrical pulses to achieve defibrillation. The above conclusions are also applicable to external defibrillators.
The implantable defibrillator applies electrical pulses directly to the heart in vivo. Defibrillation energy reaches 100% of the heart, and external defibrillators apply electrical pulses indirectly to the heart by applying them to the patient's skin (external electrodes). Defibrillation energy needs to overcome the transthoracic electrical resistance of the body to reach the heart, and only 4% of defibrillation energy reaches the heart. Thus, the external defibrillation electrical pulse energy is two orders of magnitude higher than the internal defibrillation electrical pulse energy. The electrical pulse power of an external defibrillator is on the order of tens of kilowatts.
Due to the characteristic of capacitor discharge, the output voltage of the rising wave needs to rise in a counter potential, and the realization is difficult.
Disclosure of Invention
The invention aims to solve the technical problem that the realization of the defibrillation waveform of a defibrillator by the rising wave is difficult due to the characteristic of capacitor discharge in the prior art, and aims to provide a rising wave external cardiac defibrillator and a control method thereof.
A kind of rising wave external heart defibrillator, including a strength control circuit, have the first capacitor and two defibrillation outputs, the said strength control circuit is used for controlling the magnitude of the defibrillation current, realize the rising waveform;
the intensity control circuit further has:
the drain electrode of the first field effect transistor is connected with one end of the first capacitor, and the grid electrode of the first field effect transistor is connected with an external control circuit;
the anode of the first diode is connected with the other end of the first capacitor, and the cathode of the first diode is connected with the source electrode of the first field effect transistor;
one end of the inductor is connected with the source electrode of the first field effect transistor;
the two ends of the second capacitor are respectively connected with the two defibrillation output ends, and one end of the second capacitor is connected with the other end of the first capacitor;
the source electrode of the second field effect transistor is connected with the other end of the first capacitor, and the grid electrode of the second field effect transistor is connected with an external control circuit;
and the anode of the second diode is respectively connected with the other end of the inductor and the drain electrode of the second field effect transistor, and the cathode of the second diode is connected with the other end of the second capacitor.
As a preferred scheme, the first field effect transistor and the second field effect transistor are both N-channel field effect transistors, preferably silicon carbide field effect transistors;
the discharge frequency of the first field effect tube and the discharge frequency of the second field effect tube are both above 100 kHz.
Preferably, the ascending wave external cardiac defibrillator further comprises a direction control circuit, the direction control circuit is used for controlling the direction of defibrillation current and generating a two-phase defibrillation wave, and the direction control circuit is located between the second capacitor and the two defibrillation output ends;
the direction control circuit includes:
a third transistor, wherein the collector is connected with the other end of the second capacitor, and the grid is connected with an external control circuit;
a fourth transistor, wherein the collector of the fourth transistor is connected with the emitter of the third transistor, the emitter of the fourth transistor is connected with one end of the second capacitor, and the grid of the fourth transistor is connected with an external control circuit;
a fifth transistor, wherein the collector of the fifth transistor is connected with the other end of the second capacitor, and the grid of the fifth transistor is connected with an external control circuit;
the collector of the sixth transistor is connected with the emitter of the fifth transistor, the emitter of the sixth transistor is connected with one end of the second capacitor, and the grid of the sixth transistor is connected with an external control circuit;
the two defibrillation output ends are respectively a first output end and a second output end, the first output end is connected with the common end of the emitter of the third transistor and the collector of the fourth transistor, and the second output end is connected with the common end of the emitter of the fifth transistor and the collector of the sixth transistor.
Preferably, the first field effect transistor and the second field effect transistor both use Insulated Gate Bipolar Transistors (IGBTs).
Preferably, the direction control circuit further includes:
a first bidirectional sequential-change suppression diode arranged between the common terminal of the emitter of the third transistor and the collector of the fourth transistor and the first output terminal;
and the second bidirectional compliance suppression diode is arranged between the second output end and the common end of the emitter of the fifth transistor and the collector of the sixth transistor.
A method of controlling an intensity control circuit, comprising:
the first field effect transistor, the first diode, the inductor and the second capacitor form a voltage reduction discharge circuit, and the second field effect transistor, the second diode, the inductor and the second capacitor form a voltage boosting discharge circuit;
collecting the voltage on the first capacitor and setting the voltage as input voltage Va, and collecting the voltage on the second capacitor and setting the voltage as output voltage Vb;
when discharging is started, va is larger than Vb, the voltage reduction discharging circuit works, when Va = Vb, the voltage reduction discharging circuit stops working, and the voltage boosting discharging circuit works until defibrillation discharging is finished.
Preferably, at the start of discharge, va > Vb, the step-down discharge circuit operates: the first field effect transistor is controlled to work in a high-frequency switching state by the external control circuit, the second field effect transistor is closed by the external control circuit, and the first field effect transistor and the second field effect transistor are controlled to work in a high-frequency switching state by the external control circuitAn external control circuit controls the first field effect transistors to be staggered in an on period (T) ON ) And off period (T) OFF )；
When Va = Vb, the boost discharge circuit operates: the first field effect transistor is switched on through the external control circuit, the second field effect transistor is controlled to work in a high-frequency switching state through the external control circuit, and the second field effect transistor is controlled to be in a switching-on period and a switching-off period in a staggered mode through the external control circuit;
and after a preset discharge period is reached, the first field effect transistor and the second field effect transistor are closed through the external control circuit.
Preferably, when the step-down discharge circuit operates, a relationship between the output voltage Vb and the input voltage Va is:
Vb＝D·Va
wherein D is the ON period (T) of the first FET ON ) And the switching period (T) ON +T OFF ) Duty cycle of (d);
the purpose of the output voltage Vb rising with the discharge time is achieved by adjusting D.
Preferably, when the boost discharge circuit operates, the relationship between the output voltage Vb and the input voltage Va is:
wherein D is the ON period (T) of the second field effect transistor ON ) And switching period (T) ON +T OFF ) And D is 0-99%;
the counter-potential rise of the output voltage Vb is achieved by adjusting D.
A control method of a direction control circuit, comprising:
at the start of discharge, first phase discharge starts: turning off the fourth transistor by the external control circuit, turning on the third transistor by the external control circuit, turning off the fifth transistor by the external control circuit, and turning on the sixth transistor by the external control circuit;
after a preset discharge period, considering that the first-phase discharge is finished, turning off the first field effect transistor through the external control circuit, turning off the second field effect transistor through the external control circuit, turning off the third transistor through the external control circuit, turning on the fourth transistor through the external control circuit, turning off the sixth transistor through the external control circuit, and turning on the fifth transistor through the external control circuit;
after waiting for a preset time, the second phase discharge starts: and switching on the first field effect transistor or the second field effect transistor through the external control circuit, and continuing to perform discharge work until the second-phase discharge is finished and the defibrillation discharge is finished.
Preferably, before the start of discharging, the third transistor and the fifth transistor are turned off by the external control circuit, and the fourth transistor and the sixth transistor are turned on by the external control circuit.
The positive progress effects of the invention are as follows: the invention adopts the wave-rising external cardiac defibrillator and the control method thereof, and has the following advantages:
1. the intensity control circuit controls the defibrillation current to form rising defibrillation waves, the waveform better conforms to the response characteristic of myocardial cells, the defibrillation success rate is improved, and the current damage to the myocardial cells is reduced.
2. The user is used as the center, the change of the application environment of the user is put in, and the external defibrillation can be applied to various external defibrillations.
3. And the high-frequency discharge circuit is utilized to realize the accurate control of the defibrillation current.
4. The circuit structure has good compliance and is convenient for industrialization.
5. The diode is used for replacing the traditional high-voltage relay, and the high-voltage relay has no mechanical contact, and is good in durability, high in reliability and good in electromagnetic compatibility.
6. The design of the direction control circuit can complete the polarity conversion of the defibrillation current, generate a second phase of the defibrillation pulse, and combine with the strength control circuit to form the purpose of biphasic rising wave defibrillation.
Drawings
FIG. 1 is a schematic diagram of a circuit structure according to the present invention;
fig. 2 is a timing diagram between waveforms at various points during a defibrillation discharge of the present invention.
Detailed Description
In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further described with the specific drawings.
Referring to fig. 1, a boosted-wave external cardiac defibrillator includes an intensity control circuit for controlling the magnitude of a defibrillation current to achieve a boosted waveform. The intensity control circuit comprises a first capacitor C1, a second capacitor C2, a first field effect tube Q1, a second field effect tube Q2, a first diode D1, a second diode D2, an inductor L and two defibrillation output ends.
One end of the first capacitor C1 is connected to the drain of the first field effect transistor Q1, and the other end of the first capacitor C1 is grounded. The grid electrode of the first field effect transistor Q1 is connected with an external control circuit, and the source electrode of the first field effect transistor Q1 is respectively connected with the negative electrode of the first diode D1 and one end of the inductor L. The anode of the first diode D1 is connected to the other end of the first capacitor C1. Two ends of a second capacitor C2 are respectively connected with the two defibrillation output ends, one end of the second capacitor C2 is connected with the other end of the first capacitor C1, the other end of the second capacitor C2 is connected with the cathode of a second diode D2, and the anode of the second diode D2 is respectively connected with the other end of the inductor L and the drain of the second field effect transistor Q2. The source electrode of the second field effect transistor Q2 is connected with the other end of the first capacitor C1, and the grid electrode of the second field effect transistor Q2 is connected with an external control circuit.
In some embodiments, the first field effect transistor Q1 and the second field effect transistor Q2 are both N-channel field effect transistors, preferably silicon carbide type field effect transistors; the discharge frequency of the first field effect tube Q1 and the second field effect tube Q2 is over 100kHz, so that when large current is discharged, the first field effect tube Q1 and the second field effect tube Q2 are quickly opened and reliably closed.
In some embodiments, the boosted-wave external cardiac defibrillator further comprises a direction control circuit for controlling the direction of the defibrillation current, generating a biphasic defibrillation wave, and controlling the direction of the defibrillation current and the body information signal. The direction control circuit is located between the second capacitor C2 and the two defibrillation outputs. The direction control circuit includes a third transistor Q3, a fourth transistor Q4, a fifth transistor Q5, and a sixth transistor Q6.
The collector of the third transistor Q3 is connected to the other end of the second capacitor C2, the gate of the third transistor Q3 is connected to the external control circuit, and the emitter of the third transistor Q3 is connected to the collector of the fourth transistor Q4. An emitter of the fourth transistor Q4 is connected to one end of the second capacitor C2, and a gate of the fourth transistor Q4 is connected to an external control circuit. A collector of the fifth transistor Q5 is connected to the other end of the second capacitor C2, a gate of the fifth transistor Q5 is connected to the external control circuit, and an emitter of the fifth transistor Q5 is connected to a collector of the sixth transistor Q6. An emitter of the sixth transistor Q6 is connected to one end of the second capacitor C2, and a gate of the sixth transistor Q6 is connected to an external control circuit.
The two defibrillation output terminals are respectively a first output terminal and a second output terminal, the first output terminal is connected with the common terminal of the emitter of the third transistor Q3 and the collector of the fourth transistor Q4, and the second output terminal is connected with the common terminal of the emitter of the fifth transistor Q5 and the collector of the sixth transistor Q6.
In some embodiments, the first field effect transistor Q1 and the second field effect transistor Q2 both use Insulated Gate Bipolar Transistors (IGBTs) and are responsible for controlling the current polarity.
In some embodiments, the directional control circuit further includes a first bi-directional compliance suppressor diode Z1 and a second bi-directional compliance suppressor diode Z2. The first bidirectional compliance suppression diode Z1 is disposed between the common terminal and the first output terminal of the emitter of the third transistor Q3 and the collector of the fourth transistor Q4. A second bidirectional compliance suppressor diode Z2 is provided between the second output terminal and the common terminal of the emitter of the fifth transistor Q5 and the collector of the sixth transistor Q6.
The first capacitor C1 of the present invention is an energy storage device that can be charged with the energy necessary to deliver an electrical defibrillation pulse to the patient. Before defibrillation discharge, the first capacitor C1 needs to be charged, the first capacitor C1 can be charged through the existing charging circuit, and the energy stored in the first capacitor C1 is enough to complete defibrillation discharge. The voltage across the first capacitor C1 is represented by the input voltage Va. The two defibrillation output ends are used for being connected with a pair of electrodes, and the pair of electrodes acts outside or inside the human body. When a pair of electrodes is applied to the body, the transthoracic impedance of the body is a resistance RT, which is associated with the individual patient and is typically 25 Ω -175 Ω. A discharge circuit is formed between the first capacitor C1 and the resistor RT. When defibrillation is discharged, the discharge loop starts to work, and the energy in the first capacitor C1 is released to the human body through the pair of electrodes. The relationship between the magnitude of the defibrillation current and the output voltage Vb across the second capacitor C2 and the resistor RT follows ohm's law. The direction control circuit works in an opening state during discharging to provide a passage for discharging current.
The discharge circuit comprises the intensity control circuit, and the intensity control circuit adopts two topological structures, namely a voltage reduction discharge circuit and a voltage boosting discharge circuit. During the discharging process, the voltage of the first capacitor C1 is automatically switched according to the relation of the voltage required by defibrillation. The high-frequency discharge switches, namely the first field effect transistor Q1 and the second field effect transistor Q2 can accurately control discharge current to generate defibrillation pulse with rising waveform. The intensity control circuit of the present invention can be controlled in the following manner.
In some embodiments, the present invention also provides a control method of an intensity control circuit, comprising:
the first field effect tube Q1, the first diode D1, the inductor L and the second capacitor C2 form a voltage reduction discharge circuit, and the second field effect tube Q2, the second diode D2, the inductor L and the second capacitor C2 form a voltage boosting discharge circuit.
The voltage across the first capacitor C1 is collected and set as the input voltage Va, and the voltage across the second capacitor C2 is collected and set as the output voltage Vb.
The voltage reduction discharging circuit and the voltage boosting discharging circuit work in a time-sharing mode, namely when discharging starts, va is larger than Vb, the voltage reduction discharging circuit works, when Va = Vb, the voltage reduction discharging circuit stops working, and the voltage boosting discharging circuit works until defibrillation discharging is finished.
In some embodiments, the generation of the defibrillation waveform is described in detail with reference to fig. 2. Wherein, (a) is a defibrillation current and cell and myocardial response curve, a1 is a first-phase defibrillation waveform, and a2 is a myocardial response curve. And (b) the start and polarity control signals of the defibrillation waveform. (c) Is the gate driving signal of the first field effect transistor Q1, which is provided by an external control circuit. (d) Is the gate drive signal of the second field effect transistor Q2, which is provided by an external control circuit.
At the start of discharge, i.e., at time t1 in fig. 2, va > Vb, the step-down discharge circuit starts operating: the first field effect transistor Q1 is controlled to work in a high-frequency switching state through the external control circuit, and the second field effect transistor Q2 is closed through the external control circuit, so that the second field effect transistor Q2 works in a turn-off state. The first field effect transistor Q1 is controlled to be staggered in an on period (T) by an external control circuit ON ) And off period (T) OFF ) That is, in the discharge period from T1 to T2, the first FET Q1 is divided into an on period (T) ON ) And off period (T) OFF )。
At T ON During the period: in this state, the first diode D1 is reverse biased and thus equivalently open. The charge on the first capacitor C1 flows through the first fet Q1, the inductor L, the second capacitor C2, and the resistor RT. The voltage VL = Va-Vb > 0 across the inductance L. Therefore, the inductor current rises in a linear manner. Since the voltage of the inductor L is in the same direction as the current, the inductor current increases, so that at T ON Meanwhile, the first capacitor C1 stores energy into the inductor L, and simultaneously stores energy into the second capacitor C2, and supplies current to the resistor RT.
At T OFF During the period: when the first field effect transistor Q1 is disconnected, the current at two ends of the inductor L cannot change suddenly, and the direction of the inductor current is opposite to that of T ON Similarly, at this time, the current in the inductor L changes in the decreasing direction. The voltage across the inductor L changes abruptly and the first diode D1 is turned on. Electric powerThe inductance L and the second capacitor C2 will T ON During which the stored energy supplies current to resistor RT.
The relationship between the output voltage Vb and the input voltage Va is:
Vb＝D·Va
wherein D is the ON period (T) of the first FET Q1 ON ) And the switching period (T) ON +T OFF ) The duty cycle of (c). Although Va decreases with discharge time, the purpose of the output voltage Vb increasing with discharge time is achieved by adjusting D.
When discharging is carried out to the time t2, va = Vb, the voltage reduction discharging circuit stops working, the voltage boosting discharging circuit works: the first field effect transistor Q1 is turned on through an external control circuit, namely the first field effect transistor Q1 works in a normally open state to provide a path for the boost discharge circuit. And the second field effect transistor Q2 is controlled by an external control circuit to work in a high-frequency switching state so as to carry out boosting discharge. The second field effect transistor Q2 is controlled to be staggered in an opening period (T) by an external control circuit ON ) And off period (T) OFF )。
At T ON During the period: the first field effect transistor Q1 and the second field effect transistor Q2 are both switched on to connect the inductor L and the first capacitor C1 in parallel, the electric energy in the first capacitor C1 is transferred into the inductor L, and the defibrillation current is provided by the second capacitor C2.
At T OFF During the period: the second field effect transistor Q2 is turned off, the inductor L maintains the original current direction, the back electromotive force in the inductor L turns on the second diode D2, the inductor current supplies energy to the load, and at the same time, the second capacitor C2 is replenished with energy. The inductor current is continuous and does not reach zero during a switching cycle, and the relationship between the output voltage Vb and the input voltage Va is:
wherein D is the ON period (T) of the second field effect transistor Q2 ON ) And the switching period (T) ON +T OFF ) And D is 0-99%; by regulating D the inverse potential of the output voltage VbAnd (5) lifting.
When the discharging is carried out to the time t3, a preset discharging period is considered to be reached (the first phase discharging is completed), the first field effect transistor Q1 and the second field effect transistor Q2 are closed through the external control circuit, and the boosting discharging circuit stops discharging. The polarity conversion of the defibrillation current may be accomplished by the directional control circuit to produce a second phase of the defibrillation pulse.
In some embodiments, referring to fig. 2, the present invention further provides a control method of the direction control circuit, wherein the third transistor Q3, the fourth transistor Q4, the fifth transistor Q5 and the sixth transistor Q6 of the direction control circuit are responsible for controlling the current polarity, so that the defibrillation pulse has a first phase and a second phase. The specific process is as follows:
before the discharge starts, the third transistor Q3 and the fifth transistor Q5 are turned off by the external control circuit, and the fourth transistor Q4 and the sixth transistor Q6 are turned on by the external control circuit. The resistor RT is disconnected from the second capacitor C2, and two ends of the resistor RT are grounded through the first bidirectional forward-change suppression diode Z1 and the second bidirectional forward-change suppression diode Z2. This may reduce patient leakage current across resistor RT.
At the start of discharge, i.e. at time t1 in fig. 2, first phase discharge starts: the fourth transistor Q4 is turned off by the external control circuit, the third transistor Q3 is turned on by the external control circuit, the fifth transistor Q5 is turned off by the external control circuit, and the sixth transistor Q6 is turned on by the external control circuit.
The first fet Q1 delivers energy to the second capacitor C2 at a high frequency through the inductor L and the output voltage Vb starts to rise, causing the defibrillation current to start to rise. As shown in fig. 1, the direction of the current generated in the resistor RT is positive up and negative down.
When the discharging is carried out to the time t3, the preset discharging period is considered to be reached, the first phase discharging is finished, the first field effect tube Q1 is closed through the external control circuit, and the second field effect tube Q2 is closed through the external control circuit, so that the discharging is suspended. The third transistor Q3 is turned off by the external control circuit, the fourth transistor Q4 is turned on by the external control circuit, the sixth transistor Q6 is turned off by the external control circuit, and the fifth transistor Q5 is turned on by the external control circuit. And a certain time is left to ensure that the switch enters a stable state. The third transistor Q3, the fourth transistor Q4, or the sixth transistor Q6, the fifth transistor Q5 may be turned on at the same time during the switching process. This is not allowed in conventional defibrillation discharges. Since the first capacitor C1 is short-circuited, the IGBT (insulated gate bipolar transistor) is electrically broken down by a high voltage with catastrophic consequences. Therefore, the present invention prefers that the switching speed of the first fet Q1 and the second fet Q2 is one order of magnitude faster than that of the IGBT. When the discharge is stopped, the first field effect tube Q1 and the second field effect tube Q2 are immediately closed. After the third transistor Q3 and the fourth transistor Q4 are turned on at the same time, the second capacitor C2 is short-circuited. Since the energy in the second capacitor C2 is small, the IGBT itself has a short-circuit resistance, so the IGBT is not burned out.
After waiting for a preset time, when the discharge is carried out to the time t4, the second-phase discharge is started: and the first field effect tube Q1 or the second field effect tube Q2 is switched on through the external control circuit, and the discharging work is continued until the second phase discharging is finished and the defibrillation discharging is finished.
As shown in fig. 2, when the discharge is performed to the time t4, the first fet Q1 is turned on by the external control circuit, and the second fet Q2 is controlled by the external control circuit to operate in the high-frequency switching state, so that the boost discharge is performed. The second field effect transistor Q2 is controlled to be staggered in the on period (T) by an external control circuit ON ) And off period (T) OFF ). the operation principle during the period t4 to t5 is the same as that during the period t2 to t 3.
The conduction voltage drop of the first bidirectional forward-variation suppression diode Z1 and the second bidirectional forward-variation suppression diode Z2 is only several volts, and the switching speed is in picosecond level. Since the defibrillation voltage is up to two kilovolts, the defibrillation current can smoothly pass through the first bidirectional compliance suppression diode Z1 and the second bidirectional compliance suppression diode Z2 to reach the resistor RT. For the electrocardio of a patient, human body information signals such as impedance detection and the like are millivolt-level weak signals and cannot pass through the first bidirectional cis-trans suppression diode Z1 and the second bidirectional cis-trans suppression diode Z2. The first bidirectional compliance suppression diode Z1 and the second bidirectional compliance suppression diode Z2 are equivalent to completely disconnecting the human body information signal from the discharge circuit. The human body information signal is taken out from the voltage detection point Ve and the voltage detection point Vf in fig. 1. The internal resistance of the human body information signal is less than 100k omega. The impedance of the first bidirectional compliance suppression diode Z1 and the second bidirectional compliance suppression diode Z2 to weak signals is 200M Ω. Since the defibrillation discharge is completed between t1 and t5, the measurement of the human body information signal is performed outside the time period from t1 to t 5. So that the two signals do not influence each other. The advantages of the above method of the present invention are no mechanical contacts, good durability and high reliability.
The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are described in the specification and illustrated only to illustrate the principle of the present invention, but that various changes and modifications may be made therein without departing from the spirit and scope of the present invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (10)
1. A kind of rising wave external heart defibrillator, including a intensity control circuit, have first capacitor and two defibrillation outputs;
characterized in that the intensity control circuit further has:
the drain electrode of the first field effect transistor is connected with one end of the first capacitor, and the grid electrode of the first field effect transistor is connected with an external control circuit;
the anode of the first diode is connected with the other end of the first capacitor, and the cathode of the first diode is connected with the source electrode of the first field effect transistor;
one end of the inductor is connected with the source electrode of the first field effect transistor;
the two ends of the second capacitor are respectively connected with the two defibrillation output ends, and one end of the second capacitor is connected with the other end of the first capacitor;
the source electrode of the second field effect transistor is connected with the other end of the first capacitor, and the grid electrode of the second field effect transistor is connected with an external control circuit;
and the anode of the second diode is respectively connected with the other end of the inductor and the drain electrode of the second field effect transistor, and the cathode of the second diode is connected with the other end of the second capacitor.
2. The ascending wave external cardiac defibrillator of claim 1 further comprising a direction control circuit, said direction control circuit being positioned between said second capacitor and said two defibrillation outputs;
the direction control circuit has:
a third transistor, wherein the collector is connected with the other end of the second capacitor, and the grid is connected with an external control circuit;
a fourth transistor, wherein the collector is connected with the emitter of the third transistor, the emitter is connected with one end of the second capacitor, and the grid is connected with an external control circuit;
a fifth transistor, the collector of which is connected with the other end of the second capacitor, and the grid of which is connected with an external control circuit;
a sixth transistor, wherein the collector is connected with the emitter of the fifth transistor, the emitter is connected with one end of the second capacitor, and the grid is connected with an external control circuit;
the two defibrillation output ends are respectively a first output end and a second output end, the first output end is connected with the common end of the emitter of the third transistor and the collector of the fourth transistor, and the second output end is connected with the common end of the emitter of the fifth transistor and the collector of the sixth transistor.
3. The ascending wave external cardiac defibrillator of claim 2 wherein said first and second fets are N-channel fets, preferably sic fets, and wherein said first and second fets each discharge at a frequency of 100kHz or more;
the first field effect transistor and the second field effect transistor are preferably insulated gate bipolar transistors.
4. The ascending wave external cardiac defibrillator of claim 2 wherein the direction control circuit further comprises:
a first bidirectional sequential-change suppression diode arranged between the common terminal of the emitter of the third transistor and the collector of the fourth transistor and the first output terminal;
and the second bidirectional compliance suppression diode is arranged between the common end of the emitter of the fifth transistor and the collector of the sixth transistor and the second output end.
5. A method of controlling an intensity control circuit of any of claims 1 to 4, comprising:
the first field effect transistor, the first diode, the inductor and the second capacitor form a voltage reduction discharge circuit, and the second field effect transistor, the second diode, the inductor and the second capacitor form a voltage boosting discharge circuit;
collecting the voltage on the first capacitor and setting the voltage as input voltage Va, and collecting the voltage on the second capacitor and setting the voltage as output voltage Vb;
when discharging is started, va is larger than Vb, the voltage reduction discharging circuit works, when Va = Vb, the voltage reduction discharging circuit stops working, and the voltage boosting discharging circuit works until defibrillation discharging is finished.
6. The control method of the intensity control circuit according to claim 5, wherein at the start of discharge, va > Vb, the step-down discharge circuit operates: controlling the first field effect transistor to work in a high-frequency switching state, closing the second field effect transistor, and controlling the first field effect transistor to be in an on period and an off period in a staggered manner;
when Va = Vb, the boost discharge circuit operates: switching on the first field effect transistor, controlling the second field effect transistor to work in a high-frequency switching state, and controlling the second field effect transistor to be in a switching-on period and a switching-off period in a staggered manner;
and turning off the first field effect transistor and the second field effect transistor until a preset discharge period is reached.
7. The method for controlling an intensity control circuit according to claim 6, wherein, when the step-down discharge circuit operates, a relationship between the output voltage Vb and the input voltage Va is:
Vb＝D·Va
d is the duty ratio of the first field effect transistor in the on period and the switching period;
the purpose of the output voltage Vb rising with the discharge time is achieved by adjusting D.
8. The method for controlling the intensity control circuit according to claim 6, wherein the relationship between the output voltage Vb and the input voltage Va when the step-up discharge circuit operates is:
wherein D is the duty ratio of the on period and the switching period of the second field effect transistor, and the value of D is 0-99%;
the counter-potential rise of the output voltage Vb is achieved by adjusting D.
9. A control method of the direction control circuit of any one of claims 2 to 4, comprising:
at the start of discharge, first phase discharge starts: turning off the fourth transistor, turning on the third transistor, turning off the fifth transistor, and turning on the sixth transistor;
after a preset discharge period, considering that the first phase discharge is finished, closing the first field effect transistor, closing the second field effect transistor, closing the third transistor, turning on the fourth transistor, closing the sixth transistor and turning on the fifth transistor;
after waiting for a preset time, the second phase discharge starts: and turning on the first field effect transistor or the second field effect transistor, and continuing to perform discharge work until the second-phase discharge is finished and the defibrillation discharge is finished.
10. The control method of the direction control circuit according to claim 9, wherein before the start of discharge, the third transistor and the fifth transistor are turned off, and the fourth transistor and the sixth transistor are turned on.
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| CN202210965512.6A CN115282481A (en) | 2022-08-12 | 2022-08-12 | Ascending wave external cardiac defibrillator and control method thereof |
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| CN202210965512.6A CN115282481A (en) | 2022-08-12 | 2022-08-12 | Ascending wave external cardiac defibrillator and control method thereof |
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