Biphasic defibrillation circuit and defibrillator

1. A biphasic defibrillation circuit for supplying a biphasic pulse to a patient when connected to defibrillation electrodes of an automated external defibrillator, comprising:

a switching circuit comprising a first switch, a second switch, a third switch, and a fourth switch, wherein a first output terminal and a second output terminal from the switching circuit are respectively coupled to the defibrillation electrodes, wherein a first phase pulse and a second phase pulse in an opposite direction to the first phase pulse are applied to the defibrillation electrodes by the switching circuit;

a first energy storage device coupled to the defibrillation electrodes by the switching circuit for delivering a first phase current to the defibrillation electrodes during the first phase pulse and delivering a second phase current in an opposite direction to the first phase current to the defibrillation electrodes during the second phase pulse, wherein the first energy storage device is a high voltage energy storage device, a first lead of the first energy storage device is coupled with the switching circuit directly and a second lead of the first energy storage device is coupled with the switching circuit through an eighth switch;

a second energy storage device coupled to defibrillation electrodes during at least one of the first and second phase pulses for respectively delivering at least one of the first phase current and the second phase current in conjunction with the first energy storage device, wherein the second energy storage device is a low voltage energy storage device, a first lead of the second energy storage device is coupled with the switching circuitry through a sixth switch and with the second lead of the first energy storage device through a seventh switch and a second lead of the second energy storage device is coupled with the switching circuit directly; and

a charging circuit coupled to the first and second energy storage devices for charging the first and second energy storage devices, wherein charging of the first and second energy storage devices is controlled by a fifth switch;

wherein a serial branch formed by the sixth switch and the second energy storage device connects in parallel to a serial branch formed by the first energy storage device and the eighth switch; and

wherein a difference between a first length of a first discharging time of the first phase pulse and a second length of a second discharging time of the second phase pulse is less than 40 percent of the first length of the first discharging time.

2. The biphasic defibrillation circuit according to claim 1 , wherein only the first energy storage device delivers the first phase current during the first phase pulse, and both the first and second energy storage devices deliver the second phase current in the opposite direction of the first phase current during the second phase pulse.

3. The biphasic defibrillation circuit according to claim 2 , wherein the first energy storage device connects with the second energy storage device in series through the seventh switch, and wherein the switching circuit comprises:

a first switch set, comprising the first switch and the third switch, wherein switches of the first switch set and the seventh switch are turned off and the sixth and eighth switches are turned on during the second phase pulse and the switches of the first switch set and the seventh switch are turned on and the sixth and eighth switches are turned off during the first phase pulse to make a positive and negative terminals of a serial branch formed by the first energy storage device, the seventh switch, and the second energy storage device couple to the first and second output terminals respectively; and

a second switch set, comprising the second switch and the fourth switch, wherein switches of the second switch set and the sixth and eighth switches are turned off during the first phase pulse and are turned on during the second phase pulse to make positive and negative terminals of a parallel branch formed by the first and second energy storage device connect to the second and first output terminals respectively.

4. The biphasic defibrillation circuit according to claim 3 , wherein the first switch set comprises:

a first switch coupled between the first output terminal and positive lead that couples the first lead of the first energy storage device with the first lead of the second energy storage device;

a third switch coupled between a negative lead, that couples the second lead of the first energy storage device with the second lead of the second energy storage device, and

the second output terminal of the switching circuit; and

wherein the second switch set comprises:

a second switch coupled between the positive lead and the second output terminal of the switching circuit; and

a fourth switch coupled between the negative lead and the first output terminal of the switching circuit.

5. The biphasic defibrillation circuit according to claim 1 , further comprising:

a microprocessor for outputting control signals to the switching circuit;

and

a transformer, wherein a primary coil of the transformer is coupled between power and ground through the fifth switch, and an auxiliary coil forms a charging structure which charges the first and second energy storage devices, wherein a control terminal of the fifth switch responds to a control signal from the microprocessor to change a state of the fifth switch between an off state and an on state.

6. The biphasic defibrillation circuit according to claim 1 , wherein only the first energy storage device is used to deliver the first phase current to the defibrillation electrodes during the first phase pulse, and the first and second energy storage devices are connected in parallel to deliver the second phase current in the opposite direction to the first phase current to the defibrillation electrodes during the second phase pulse.

7. The biphasic defibrillation circuit according to claim 6 , wherein the sixth switch and the seventh switch are turned off and the eighth switch is turned on during the first phase pulse and the sixth switch and the eighth switch are turned on while the seventh switch is turned off during the second phase pulse;

wherein a serial branch formed by the sixth switch and the second energy storage device connects to a serial branch formed by the eighth switch and the first energy storage device in parallel; and

wherein the switching circuit further comprises:

a first switch set, comprising the first switch and the third switch, wherein the first switch set is turned off during the second phase pulse and turned on during the first phase pulse to couple positive and negative terminals of the first energy storage device to the first and second output terminal of the switching circuit respectively; and

a second switch set, comprising the second switch and the fourth switch, wherein the second switch set is turned off during the first phase pulse and turned on during the second phase pulse to couple the positive and negative terminal of the parallel branch formed by the first and second energy storage device to the second and first output terminals of the switching circuit respectively.

8. The biphasic defibrillation circuit according to claim 1 , wherein both the first and second energy storage devices are used to deliver the first phase current to the defibrillation electrodes during the first phase pulse, and only the first energy storage device is used to deliver the second phase current in the opposite direction to the first phase current to the defibrillation electrodes during the second phase pulse.

9. The biphasic defibrillation circuit according to claim 1 , wherein the first and second energy storage devices are connected in a first combination to deliver the first phase current to the defibrillation electrodes during the first phase pulse, and the first and second energy storage devices are connected in a second combination to deliver the second phase current in the opposite direction of the first phase current to the defibrillation electrodes during the second phase pulse.

10. The biphasic defibrillation circuit according to claim 1 , wherein at least one of the first and second energy storage devices comprises a capacitor.

11. The biphasic defibrillation circuit according to claim 1 , wherein the voltage of the second energy storage device is one-tenth the voltage of the first energy storage device.

12. The biphasic defibrillation circuit according to claim 1 , further comprising:

a first voltage sampling circuit coupled to two terminals of the serial branch formed by the first energy storage device and the eighth switch for sampling the voltage of the first energy storage device;

a second voltage sampling circuit coupled to positive and negative terminals of the second energy storage device for sampling the voltage of the second energy storage device.

13. The biphasic defibrillation circuit according to claim 1 , further comprising:

a discharging circuit coupled between the second lead of the first energy storage device and the first lead of the second energy storage device for discharging excess energy stored in the first and second energy storage devices.

14. A biphasic defibrillation circuit for supplying first phase pulses and second phase pulses to a patient when connected to defibrillation electrodes of an automated external defibrillator, comprising:

a switching circuit comprising an H-bridge switch arrangement, wherein a first output terminal and a second output terminal from the H-bridge switch arrangement are respectively coupled to the defibrillation electrodes, wherein the first phase pulse and the second phase pulse in an opposite direction to the first phase pulse are applied to the defibrillation electrodes by the switching circuit through changing the state of the switching circuit;

a microprocessor for outputting control signals to the switching circuit and controlling the state of the switching circuit;

a first energy storage device coupled to defibrillation electrodes by the switching circuit for delivering first phase current to the defibrillation electrodes during the first phase pulse and delivering second phase current to the defibrillation electrodes during the second phase pulse, wherein the first energy storage device is a high voltage energy storage device, a first lead of the first energy storage device is coupled with the switching circuit directly and a second lead of the first energy storage device is coupled with the switching circuit through a first switch; and

a second energy storage device for delivering one or both of the first and second phase current to the defibrillation electrodes in combination with the first energy storage device, such that a discharging time constant of the second phase pulse is different from the discharging time constant of the first phase pulse or a starting discharging voltage of the second phase pulse is larger than an ending discharging voltage of the first phase pulse, wherein the second energy storage device is a low voltage energy storage device, a first lead of the second energy storage device is coupled with the switching circuitry through a second switch and with the second lead of the first energy storage device through a third switch and a second lead of the second energy storage device is coupled with the switching circuit directly, such that a serial branch formed by the second switch and the second energy storage device connects in parallel to a serial branch formed by the first energy storage device and the first switch,

wherein a difference between a first length of a first discharging time of the first phase pulse and a second length of a second discharging time of the second phase pulse is less than 40 percent of the first length of the first discharging time.

15. An automated external defibrillator, comprising:

a pair of defibrillation electrodes for connecting to a patient; and

a biphasic defibrillation circuit comprising:

a switching circuit comprising a first output terminal and a second output terminal respectively coupled to the defibrillation electrodes, wherein the switching circuit includes a first switching set and a second switching set configured such that a first phase pulse and a second phase pulse in an opposite direction to the first phase pulse are applied to the defibrillation electrodes by the switching circuit;

a first energy storage device coupled to defibrillation electrodes by the switching circuit for delivering first phase current to the defibrillation electrodes during the first phase pulse and delivering second phase current in an opposite direction to the first phase current to the defibrillation electrodes during the second phase pulse, wherein the first energy storage device is a high voltage energy storage device, a first lead of the first energy storage device is coupled with the switching circuit directly and a second lead of the first energy storage device is coupled with the switching circuit through a first switch; and

a second energy storage device coupled to defibrillation electrodes during at least one of the first and second phase pulses for respectively delivering at least one of the first phase current and the second phase current in conjunction with the first energy storage device, wherein the second energy storage device is a low voltage energy storage device, a first lead of the second energy storage device is coupled with the switching circuitry through a second switch and with the second lead of the first energy storage device through a third switch and a second lead of the second energy storage device is coupled with the switching circuit directly, such that a serial branch formed by the second switch and the second energy storage device connects in parallel to a serial branch formed by the first energy storage device and the first switch,

wherein a difference between a trailing edge voltage of the first phase pulse and a leading edge voltage of the second phase pulse is less than 50 percent of the trailing edge voltage of the first phase pulse.

16. A biphasic defibrillation circuit for supplying a biphasic pulse to a patient when connected to defibrillation electrodes of an automated external defibrillator, comprising:

a switching circuit comprising a first switch, a second switch, a third switch, and a fourth switch, wherein a first output terminal and a second output terminal from the switching circuit are respectively coupled to the defibrillation electrodes, wherein a first phase pulse and a second phase pulse in an opposite direction to the first phase pulse are applied to the defibrillation electrodes by the switching circuit;

a first energy storage device coupled to the defibrillation electrodes by the switching circuit for delivering a first phase current to the defibrillation electrodes during the first phase pulse and delivering a second phase current in an opposite direction to the first phase current to the defibrillation electrodes during the second phase pulse, wherein the first energy storage device is a high voltage energy storage device, a first lead of the first energy storage device is coupled with the switching circuit directly and a second lead of the first energy storage device is coupled with the switching circuit through an eighth switch;

a second energy storage device coupled to defibrillation electrodes during at least one of the first and second phase pulses for respectively delivering at least one of the first phase current and the second phase current in conjunction with the first energy storage device, wherein the second energy storage device is a low voltage energy storage device, a first lead of the second energy storage device is coupled with the switching circuitry through a sixth switch and with the second lead of the first energy storage device through a seventh switch and a second lead of the second energy storage device is coupled with the switching circuit directly; and

a charging circuit coupled to the first and second energy storage devices for charging the first and second energy storage devices, wherein charging of the first and second energy storage devices is controlled by a fifth switch;

wherein a serial branch formed by the sixth switch and the second energy storage device connects in parallel to a serial branch formed by the first energy storage device and the eighth switch; and

wherein a difference between a trailing edge voltage of the first phase pulse and a leading edge voltage of the second phase pulse is less than 50 percent of the trailing edge voltage of the first phase pulse.