WO2017037735A1

WO2017037735A1 - A discharging system for a defibrillator

Info

Publication number: WO2017037735A1
Application number: PCT/IN2016/000223
Authority: WO
Inventors: Sreeram Dhurjaty; Aniruddha Shashikant ATRE; Ashish Shivajirao GAWADE; Sarang Vasant GADGIL
Original assignee: Jeevtronics Pvt. Ltd.
Priority date: 2015-09-02
Filing date: 2016-09-01
Publication date: 2017-03-09

Abstract

The present invention describes a discharging system for a defibrillator. The system comprises at least one high-voltage capacitor adapted to store predetermined energy, a plurality of modules, connected to a high-voltage capacitor, comprising of a floating power supply module which also balances a plurality of semiconductor switches, the floating power supply module consisting of a combination of voltage reference units, resistors and capacitors, and at least a pair of electrodes for providing predetermined energy to a patient.

Description

A DISCHARGING SYSTEM FOR A DEFIBRILLATOR

RELATED APPLICATION

Benefit is claimed to Indian Provisional Application No. 3368/MUM/2015 titled "DISCHARGING SYSTEM FOR A HAND CRANKED DEFIBRILLATOR" filed on 02 September 2015, which is herein incorporated in its entirety by reference for all purposes.

FIELD OF THE INVENTION

The present invention generally relates to discharging system, and more particularly relates to a discharging system for a defibrillator.

BACKGROUND OF THE INVENTION

A defibrillator is a device which treats an abnormal heart condition called fibrillation, in which the heart beats randomly; fibrillation will often cause death if not reversed within a few minutes of its occurrence. Defibrillators are devices which attempt to reverse fibrillation. Defibrillators are generally powered either by mains and/or by batteries. This poses no substantial problem in the developed countries, such as the United States. In developing countries, however, more often there is no ready access to either main power or battery power.

Even when batteries are available to power defibrillators, they invariably lose their power over time; and there is a risk that, in a life-threatening situation, a battery-powered defibrillator may not function. Consequently, the manufacturers of battery-powered defibrillators suggest that the batteries therein be checked frequently, a suggestion which is as often ignored as is followed.

Furthermore, many of the battery-powered defibrillators contain lithium batteries, which may explode. Therefore, there is requirement of an alternating means to have appropriate power for defibrillators such as by mechanical means. There is no defibrillator currently existing in the market that can operated by mechanical means. Discharge circuits/systems for biphasic defibrillators are used to generate Bi-Phasic waveforms to defibrillate a patient. These waveforms start at around 1800 volts and are applied between the sternum and apex of a patient to enable a fibrillating patient to be defibrillated and restore sinus rhythm. Modern Bi-phasic circuit/system use relatively expensive components in a bridge-circuit that is actuated by isolators for each leg of the bridge. Typically, four 2400-volt IGBTs are used with each of the IGBTs actuated by an isolated power supply. This leads to an expensive solution as these IGBTs are expensive, as are the isolated power supplies used to actuate each IGBT.

Thus, there is a need for a discharging system for a defibrillator with a unique floating supply that allows actuating each of the low voltage IGBTs.

The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.

SUMMARY OF THE INVENTION

Various embodiments herein describe a discharging system for a defibrillator. The system comprises at least one high-voltage capacitor adapted to store predetermined energy, a plurality of modules connected to a high voltage capacitor, with each of the modules comprising of a floating power supply which also balances a plurality of semiconductor switches, the said floating power supply module consisting of a combination of voltage reference units, resistors and capacitors, and at least a pair of electrodes for providing predetermined energy to a patient.

According to an embodiment herein, each module comprises of at least one semiconductor switch such as an insulated gate bipolar transistor (IGBT), at least one IGBT driver to actuate the semiconductor switch for providing a controlled voltage, an actuating element having predefined instructions to provide a control signal to the semiconductor switch, wherein the actuating element comprises of digital logic or a microcontroller and logic gates, and an optical or a magnetic isolator connected to the said element to provide isolation between the control signals and the high voltage capacitor and providing the control signal received from the actuating element to the semiconductor switch; and the floating power supply module which is connected to the optical isolator, and the IGBT driver.

According to an embodiment herein, the floating power supply module comprises of at least one voltage reference unit, at least one resistor and at least one capacitor. The system has four legs for generating a biphasic waveform and each of the four legs consists of at least two semiconductor switches such as IGBTs. At least four modules forming two legs generate a single phase of the biphasic waveform.

According to an embodiment herein, at least one module comprises a monitoring module for monitoring the voltage across the high voltage capacitor, the voltage being monitored across the high voltage capacitor is further attenuated in order to be fed back to a closed loop system to control the charge, discharge elements and the high voltage capacitor.

According to an embodiment herein, the floating power supply module comprises of a plurality of transistors and resistors which provides a means to discharge the high voltage capacitor to allow safe transportation of the defibrillator. The IGBT driver comprises at least one of a NPN transistor and PNP transistor to actively turn on and turn off the IGBT. The actuating element is configured to initiate second phase of the biphasic pulse when the high voltage capacitor has discharged to a pre-specified percentage of its initial stored energy during the first phase of defibrillation. Further, in order to enhance the reliability and safety of the discharge system defined herein, it is necessary that inadvertent turn-on of the wrong IGBT legs does not occur due to reset of the microcontroller program. To achieve this, a redundancy is designed into the said discharge system wherein a combination of logic gates is configured to override any such reset event of the microcontroller program. The foregoing has outlined, in general, the various aspects of the invention and is to serve as an aid to better understanding the more complete detailed description which is to follow, in reference to such, there is to be a clear understanding that the present invention is not limited to the method or application of use described and illustrated herein. It is intended that any other advantages and objects of the present invention that become apparent or obvious from the detailed description or illustrations contained herein are within the scope of the present invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:

Figure 1 is a schematic representation illustrating a defibrillator, according to an embodiment of the present invention.

Figure 2 is a schematic representation illustrating a discharging system of a defibrillator, according to an embodiment of the present invention. Figure 3 is a block diagram representation illustrating a module in the circuit of a defibrillator, according to an embodiment of the present invention.

Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a discharging system for a defibrillator. In the following detailed description of the embodiments of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.

The specification may refer to "an", "one" or "some" embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms "includes", "comprises", "including" and/or "comprising" when used in this specification, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations and arrangements of one or more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The present invention describes a discharging system for a defibrillator. In one embodiment, the discharging system for a hand-cranked defibrillator is capable of discharging a high voltage capacitor, which is about 2000V / 360 Joules in order to deliver a biphasic shock. The defibrillator is powered by a human powered generator, a pull rope generator, a pneumatic source or mains (90V- 250V AC). The defibrillator comprises of plurality of semiconductor switches such as IGBT or MOSFET rated between 1200- 1500V configured in a way to fire a biphasic current pulse through a patient. In the circuit, each of the four legs consists of two IGBTs and each of the IGBT contains a combination of voltage reference, resistor and capacitor, which allow a floating supply to power each IGBT. The floating power supply for each IGBT references itself to the emitter of the IGBT and uses the voltage divider. The voltage divider in one of the modules is used for monitoring the high voltage capacitor in order to balance the IGBTs. The high voltage capacitor is typically 120uF and could be charged up to 2200 volts by a charging system. The voltage divider also serves to discharge the capacitor over several seconds so as to prevent a charged capacitor from being transported, thereby enhancing safety.

Figure 1 is a schematic representation illustrating a defibrillator, according to an embodiment of the present invention. The defibrillator 100 comprises a hand crank generator 101, defibrillator paddles 102, cable cord 103, cable 104, headphones 105, and a display assembly 106. A generator is connected to mechanical means such as a hand crank generator 101 for producing alternating voltage. The alternating voltage that is generated by the hand crank generator 101 charges the high voltage capacitor up to 360J. The defibrillator paddles 102 are provided with switches which when operated discharge energy into the patient. The cable cord 103 has extensions that could be used for the patient's right arm (RA), left arm (LA) and left leg (LL). While operating the defibrillator 100, the cable 104 is adapted to provide an audio output to headphones 105. The display assembly 106 is disposed at the front casing of the defibrillator 100 and it displays the energy that is being given to patient.

Figure 2 is a schematic representation illustrating a discharging system of a defibrillator, according to an embodiment of the present invention. The discharging system for a defibrillator comprises at least one high-voltage capacitor, a plurality of modules, and at least a pair of electrodes. The high-voltage capacitor is adapted to store a predetermined energy. The plurality of modules that are connected to a high-voltage capacitor comprises a floating power supply module which balances a plurality of semiconductor switches. The floating power supply module consists of a combination of voltage reference units, resistors and capacitors. The pair of electrodes provide the predetermined energy to a patient. The predetermined energies are determined by the manufacturer or based on user's configuration.

The discharging system comprises a plurality of modules 201-208 which are self- contained modules. Each of the modules consists of a semiconductor switch such as an insulated gate bipolar transistor (IGBT) and associated isolated drivers. One of the modules 204 has an additional output that allows monitoring of the HV capacitor voltage through a voltage divider. Each module consists of an opto-coupler to energize each of the modules in a floating power supply that is referenced to the emitter of the IGBT. In another embodiment, each module comprises a plurality of IGBTs. The paddles 209 and 210 of the defibrillator connect to apex and sternum of a patient 21 1. These paddles are also connected to an electrocardiogram (ECG) amplifier. A high voltage capacitor 212 stores the energy for discharge. The capacitor is 120uF and could be charged up to 1800V. An isolated ground 213 allows the circuit to create a biphasic waveform.

According to an embodiment of the present invention, a signal Enable 1 enables a first phase of the biphasic waveform by applying full capacitor voltage, thereby actuating the modules 201, 202, 207 and 208. Meanwhile, the other modules are in switched off mode by de-asserting a signal Enable 2. The capacitor voltage is monitored through the voltage divider in module 204. After the capacitor has discharged to a certain voltage which is less than the peak voltage of the capacitor, the second phase of the biphasic waveform is initiated. After a certain programmed time delay of 1 to 2ms, the modules 203, 204, 205 and 206 are enabled by asserting the signal Enable 2, whereas the other modules are de- asserted. The duration of each phase will be dependent on the impedance of the patient. The second phase will be truncated as soon as the voltage reaches 200 Volts. This procedure ensures that half of the energy is delivered in each of the two phases and the energy varies according to the user selection and patient impedance.

Figure 3 is a block diagram representation illustrating a module in the circuit of a defibrillator, according to an embodiment of the present invention. In one embodiment, each module of the plurality modules 201 to 208 comprises an actuator 301, an optical isolator 302, an IGBT 303, an IGBT driver 304, and a floating power supply module 305. The circuit has four legs and each of the four legs consists of two IGBTs. According to the present invention, the actuator 301 actuates either Enable 1 or Enable 2 depending on the position of the modules in the bridge. When either of the signals i.e., Enable 1 or Enable 2 is actuated, an optical isolator 302 is energized. The signal i.e., Enable 1 or Enable 2, emanates from a microcontroller. The optical isolator 302 further controls the single or multiple transistors.

According to an embodiment of the present invention, the floating power supply module is illustrated as follows. Through a combination of resistor, voltage reference and a diode, a small capacitor, value of which could be any value between luF to 220uF is charged from the high voltage capacitor to a suitable voltage level required to power the module mentioned above. In one embodiment, this capacitor is a floating power supply 305 that powers the module. The charge stored at the terminals of resistors in series with each of the modules is large enough to prevent leakage of charge from the high voltage capacitor. The capacitor which acts as a floating power supply 305 for the IGBT module 303 is enabled to maintain sufficient voltage that will allow the IGBT 303 to turn on. A diode isolates this floating capacitor from the charging system/circuit, when the IGBT turns ON and prevents discharge of this charged floating capacitor as this diode will be reverse biased. According to an embodiment of the present invention, the IGBT driver 304 module is illustrated as follows. According to an embodiment of the present invention, when either of the signals i.e., Enable 1 or Enable 2 is actuated, an optical isolator 302 is energized and the phototransistor in optical isolator 302 saturates. This causes the voltage at the top of the floating power supply 305 to be applied through an emitter follower configuration of an NPN transistor which rums on the IGBT 303. Simultaneously during this phase where IGBT is held ON, the emitter follower NPN switch also causes another transistor, preferably a PNP switch, to be held in OFF state. When the actuation is de-asserted, the optical isolator 302 causes its phototransistor to be OFF which causes the NPN emitter follower transistor to turn OFF. At this point the PNP switch described above turns ON because its base gets more negatively biased with respect to its emitter. This is achieved using a voltage drop of a single or plurality of diodes connected to this PNP transistor. Thus present invention uses behavior characteristics of discrete components to achieve switch ON/OFF modes rather than using expensive integrated circuits used to drive high voltage switches. These techniques enable use of commonly available components to achieve the same precision as that of the expensive integrated circuit based drivers. Therefore, this invention is several times cost effective, reliable and safe compared to standard defibrillator circuits. According to an embodiment of the present invention, the monitor in module 204 is at the top of the Zener diode. The voltage provided to the monitor is 4 times of the Zener voltage, whereas the Zener voltage is 25% of the capacitor voltage minus 60V, for a nominal Zener voltage of say 15V. This voltage, using a voltage divider, is read by the microcontroller to determine the capacitor voltage during both charging as well as discharging.

According to another embodiment of the present invention, a combination circuit is disclosed, which is composed of combination or multiplicity of components. The combination circuit consists of balancing and biasing resistors. Each IGBT has different leakage current and it requires balancing, where the magnitude should be 3-5 times the leakage current of the IGBT. This is achieved with a balance resistor in series with the Zener diode in each leg of the circuit and value of the resistor needs to be tuned based on the IGBT leakage current value. Further, the present invention uses PNP transistor in combination with a large resistance and plurality of diodes between the emitter of the PNP and ground for actively discharging the gate of the IGBT.

Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

Claims

We claim:

1. A discharging system for a defibrillator, comprising:

at least one high-voltage capacitor adapted to store predetermined energy; a plurality of modules, connected to a high-voltage capacitor, comprising of a floating power supply module which also balances a plurality of semiconductor switches, the floating power supply module consisting of a combination of voltage reference units, resistors and capacitors; and

at least a pair of electrodes for providing the predetermined energy to a patient.

2. The discharging system of claim 1 , wherein each module comprises of:

at least one semiconductor switch such as an insulated gate bipolar transistor (IGBT);

at least one IGBT driver to actuate the semiconductor switch for providing a controlled voltage;

an actuating element having predefined instructions to provide a control signal to the semiconductor switch, wherein the actuating element comprises of digital logic or a microcontroller and logic gates, and an optical or a magnetic isolator connected to the said element to provide isolation between the control signals and the high voltage capacitor and providing the control signal received from the actuating element to the semiconductor switch; and the floating power supply module which is connected to the optical isolator, and the IGBT driver.

3. The discharging system of claim 1, wherein the floating power supply module comprises of at least one voltage reference unit, at least one resistor and at least one capacitor.

4. The discharging system of claim 1, wherein the system has four legs for generating a biphasic waveform and each of the four legs consists of at least two semiconductor switches such as IGBTs.

5. The discharging system of claim 1, wherein at least four modules forming two legs generate a single phase of the biphasic waveform.

6. The discharging system of claim 1, wherein at least one module comprises a monitoring module for monitoring the voltage across the high voltage capacitor, the voltage being monitored across the high voltage capacitor is further attenuated in order to be fed back to a closed loop system to control the charge, discharge elements and the high voltage capacitor.

7. The discharging system of claim 1, wherein the high voltage capacitor is charged by a hand cranked generator or an AC-DC or DC-DC converter.

8. The discharging system of claim 1, wherein the floating power supply module comprises of a plurality of transistors and resistors which provides a means to discharge the high voltage capacitor to allow safe transportation of the defibrillator.

9. The discharging system of claim 2, wherein the IGBT driver comprises at least one of a NPN transistor and PNP transistor to actively turn on and turn off the IGBT.

10. The discharging system of claim 2, wherein the actuating element is configured to initiate second phase of the biphasic pulse when the high voltage capacitor has discharged to a pre-specified percentage of its initial stored energy during the first phase of defibrillation.

1. The discharging system of claim 2, wherein the actuating element is further connected to a redundancy based instruction set and components configured to ensure that incorrect legs of the IGBT modules do not fire simultaneously, thereby enhancing the safety of the discharge system components and avoids inadvertent short circuit path for high voltage capacitor to ground.