CN210246308U

CN210246308U - Inductance current-limiting circuit

Info

Publication number: CN210246308U
Application number: CN201921609253.3U
Authority: CN
Inventors: Peilin Wang; 汪培林
Original assignee: Suzhou Weisi Medical Technology Co ltd
Current assignee: Suzhou Weisi Medical Technology Co ltd
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2020-04-03
Anticipated expiration: 2029-09-25

Abstract

The utility model discloses an inductance current-limiting circuit, it includes: the high-voltage detection circuit comprises a high-voltage capacitor, a current-limiting inductor, an IGBT-H bridge circuit, a control circuit and a detection circuit, wherein the positive electrode of the high-voltage capacitor is connected with the current-limiting inductor, and the current-limiting inductor is connected with the IGBT-H bridge circuit; the control circuit is respectively connected with the IGBT-H bridge circuit and the detection circuit, and the detection circuit is connected with the IGBT-H bridge circuit. Inductance current-limiting circuit, can select the IGBT that flow resistance value is lower, the volume can all reduce a lot with the cost to reduce the design redundancy.

Description

Inductance current-limiting circuit

Technical Field

The utility model relates to a medical equipment technical field specifically relates to an inductance current-limiting circuit, it can be applicable to on the equipment of defibrillating.

Background

The defibrillation discharge waveform of the prior defibrillator product basically takes a biphase truncation index wave as a main part, the principle of generating the waveform is to charge a high-voltage capacitor to reach a certain voltage (1000V-2200V) so as to store corresponding energy, then the charged capacitor is connected with a specified part of a patient to discharge to the patient, so that current flows through the heart to achieve the defibrillation effect.

The turning of the current in the discharging process is realized by an H bridge formed by IGBTs (insulated gate bipolar transistors), and different current directions can be realized by opening the corresponding IGBTs in the H bridge. The IGBT has the advantages of small driving power, large current-carrying density and low saturation voltage drop. However, the current technical limitation is that the larger the withstand voltage value and the larger the current withstand value, the larger the IGBT volume is, and the more expensive the IGBT is.

In the case of defibrillator usage, the required withstand voltage is a high requirement for the present IGBTs, and in the case of extreme accidents (sweating, wetness of the patient's body, faulty short-circuiting of the electrode pads, etc.), a large current is generated (above 100A), which, although less likely, must be taken into account in the design process. The current endurance requirements for IGBTs are also high. Currents exceeding the IGBT limits may burn the IGBT out, causing danger or affecting rescue. Therefore, current defibrillator manufacturers generally choose IGBTs with large maximum carrying current to deal with, and the current defibrillator manufacturers are large in size and high in cost.

Therefore, the present inventors have been eagerly required to devise a new technique to improve the problems thereof.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, the utility model provides an inductance current limiting circuit.

The technical scheme of the utility model is that:

an inductive current limiting circuit, comprising: the high-voltage detection circuit comprises a high-voltage capacitor, a current-limiting inductor, an IGBT-H bridge circuit, a control circuit and a detection circuit, wherein the positive electrode of the high-voltage capacitor is connected with the current-limiting inductor, and the current-limiting inductor is connected with the IGBT-H bridge circuit; the control circuit is respectively connected with the IGBT-H bridge circuit and the detection circuit, and the detection circuit is connected with the IGBT-H bridge circuit.

Preferably, the IGBT-H bridge circuit includes an insulated gate bipolar transistor Q800, an insulated gate bipolar transistor Q801, an insulated gate bipolar transistor Q802, and an insulated gate bipolar transistor Q803, where a third pin of the insulated gate bipolar transistor Q800 and a third pin of the insulated gate bipolar transistor Q801 are both connected to the current-limiting inductor; the third pin of the insulated gate bipolar transistor Q802 is connected with the second pin of the insulated gate bipolar transistor Q800, the second pin of the insulated gate bipolar transistor Q802 is connected with the second pin of the insulated gate bipolar transistor Q803, and the third pin of the insulated gate bipolar transistor Q803 is connected with the second pin of the insulated gate bipolar transistor Q801.

Preferably, the control circuit comprises an and gate U1A, an and gate U1B, an and gate U1C, and an and gate U1D, and the third pin of the and gate U1A is connected to the first pin of the igbt Q800 through a resistor R1; the third pin of the AND gate U1B is connected with the first pin of the insulated gate bipolar transistor Q801 through a resistor R2; the third pin of the and gate U1C is connected to the first pin of the igbt Q802 through a resistor R3; and the third pin of the and gate U1D is connected to the first pin of the igbt Q803 through a resistor R4.

Preferably, the detection circuit comprises an operational amplifier U807 and resistors R811, R800, R801, R816 and R814, wherein a fourth pin of the operational amplifier U807 is connected with the control circuit, and a third pin of the operational amplifier U807 is connected with the IGBT-H bridge circuit through the resistor R811. The first leg of the operational amplifier U807 is connected to resistors R800, R801, R816, R814.

Preferably, the high-voltage power supply further comprises a current sampling resistor R813 which is arranged between the negative electrode of the high-voltage capacitor and the IGBT-H bridge circuit.

Preferably, the current-limiting inductor further comprises a diode D800, a diode D801 and a diode D802 which are sequentially connected in series, the diode D800, the diode D801 and the diode D802 are connected in parallel with the current-limiting inductor, wherein the anode of the diode D802 is connected with the IGBT-H bridge circuit, and the cathode of the diode D800 is connected with the anode of the capacitor.

Preferably, the and gate U1A, the and gate U1B, the and gate U1C, and the and gate U1D are 74LVC08 and gates.

Preferably, the operational amplifier U807 is an LMV331 operational amplifier.

Adopt above-mentioned technical scheme, the utility model discloses at least, include following beneficial effect:

inductance current-limiting circuit, under the prerequisite of guaranteeing not delaying the defibrillator rescue, can select the IGBT that flow resistance value is lower, the volume can all reduce a lot with the cost to reduce the design redundancy.

Drawings

Fig. 1 is a schematic diagram of an inductive current limiting circuit according to the present invention;

fig. 2 is a circuit diagram of the inductor current limiting circuit according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

As shown in fig. 1 to fig. 2, the inductor current limiting circuit according to the present invention includes: the high-voltage power supply comprises a high-voltage capacitor, a current-limiting inductor, an IGBT-H bridge circuit, a control circuit and a detection circuit, wherein the positive electrode of the high-voltage capacitor is connected with the current-limiting inductor, the current-limiting inductor is connected with the IGBT-H bridge circuit, and the IGBT-H bridge circuit is connected with a patient; the control circuit is respectively connected with the IGBT-H bridge circuit and the detection circuit, and outputs a bridge switching signal to control the on-off of the IGBT-H bridge circuit; the detection circuit is connected with the IGBT-H bridge circuit.

Preferably, the current-limiting inductor further comprises a diode D800, a diode D801 and a diode D802 which are sequentially connected in series, the diode D800, the diode D801 and the diode D802 are connected in parallel with the current-limiting inductor, and the anode of the diode D802 is connected with the IGBT-H bridge circuit.

Preferably, the operational amplifier U807 is a model LMV331 operational amplifier.

The principle of the current limiting circuit of the invention mainly utilizes the characteristic that the inductor blocks the current change. When the high-voltage capacitor discharges the circuit, according to ohm's law, I ═ U/R, and if there is no inductor, the current in the circuit will instantaneously reach a value. The inductor is characterized by blocking current change in the circuit, and an RL circuit is formed after the inductor is added into a discharge circuit, wherein the current formula in the RL circuit is i ═ Imax ^ (1-e ^ (-t/tau)), wherein Imax is the final maximum current of the circuit, t is time, and tau is a time constant tau ═ L/R. After 5 time constants τ have elapsed, the current reaches 99.9% of the maximum value, which can be considered to have been reached.

In the RL circuit, the current rises at a certain rate due to the blocking effect of the inductance. The larger the inductance value, the slower the rise time. In defibrillator applications, the current is typically on the order of 20-80A, requiring inductance above 100 uH. The inductance with the magnetic core can easily reach the inductance value, the size can be small, the saturation current of the inductance with the magnetic core is very small, and the inductance does not have the function of blocking the current after the current reaches saturation. The preferred use of this embodiment is an air core inductor with a large saturation current and a somewhat larger volume, but within an acceptable range.

By taking the capacitor voltage of 2000V, the circuit impedance of 18 Ω and the circuit block diagram shown in fig. 1 as an example, the limit current endurance value of the IGBT selected in the circuit is only 88A. Without the protection circuit, at the moment of discharge, the current 2000/18 is 111A, which has exceeded the limit value of the IGBT (88A), and the IGBT will burn out.

Therefore, a detection circuit is added in the discharging circuit, when the current exceeds 80A, the detection circuit sends out a signal to inform the control circuit to completely turn off the H bridge, and the overload current is prevented from flowing through the IGBT. However, a certain time is required for the logic circuit to react (the logic circuit sends out a turn-off signal by detection, receives the signal, and sends out the turn-off signal to turn off the IGBT switch), and the reaction time of all devices on the overcurrent protection circuit needs 1.5us at most. The circuit current cannot directly exceed 88A and must be left for a counter-off time.

The control circuit is preferably a 4-AND circuit, the output of each AND gate corresponds to the switching signal of 4 IGBTs respectively, and when the signal is at high level, the corresponding IGBT is turned on. Each and gate has two input signals, and the and gate output is high if and only if both input signals are high. Thus, one of the input signals is connected to the control signal of the MCU and the other signal is connected to the detection circuit. When the detection circuit detects that the current of the circuit exceeds the threshold (80A in the example), the detection circuit outputs low level, all AND gates are closed, and the effect of closing all the IGBT bridges is achieved.

Therefore, an inductor with inductance of 150uH is added into the circuit. In the above circuit, the time constant τ of the RL circuit is 150uH/18 Ω is 8.3(us), and the current i in the inductor circuit is Imax (1-e ^ (-t/τ)), so that after the inductor is added, it will take 2.08us for the current in the circuit to reach 88A from 80A, and the delay time of the inductance action is sufficient for the logic circuit to perform the actions of detecting and closing the H-bridge.

In practical rescue applications, the transthoracic impedance of humans is no lower than 25 Ω, and 25 Ω is also the lower limit of patient impedance in safety guidelines. The case below 25 Ω indicates a problem in the connection state of the electrode pad with the patient: abnormal conditions such as the moisture of the body of the patient, the contact with a metal necklace, the superposition of electrode plates and the like can be corrected by the operation of the rescuer. The defibrillation voltage of 2000V belongs to the higher voltage of the current defibrillation products, and only the IGBT with the current resistance value of more than 80A needs to be selected. But to avoid the above-described abnormal situation occurring to directly damage the defibrillator, 18 Ω or even below must be considered. The selection of the IGBT with the high current endurance value can inherently include the situation that under the abnormal condition, the discharge is firstly carried out, and then the rescuer is prompted to correct the field condition. But use the utility model discloses a current-limiting protection circuit both can choose for use the IGBT of lower resistant current value, realize littleer volume and lower cost, can satisfy the operation requirement of the safety criterion of defibrillating again, in time interrupt discharge when the limit condition appears, give the person of suing and labouring operation suggestion, protect patient and machine.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An inductive current limiting circuit, comprising: the high-voltage detection circuit comprises a high-voltage capacitor, a current-limiting inductor, an IGBT-H bridge circuit, a control circuit and a detection circuit, wherein the positive electrode of the high-voltage capacitor is connected with the current-limiting inductor, and the current-limiting inductor is connected with the IGBT-H bridge circuit; the control circuit is respectively connected with the IGBT-H bridge circuit and the detection circuit, and the detection circuit is connected with the IGBT-H bridge circuit.

2. The inductive current-limiting circuit of claim 1, wherein: the IGBT-H bridge circuit comprises an insulated gate bipolar transistor Q800, an insulated gate bipolar transistor Q801, an insulated gate bipolar transistor Q802 and an insulated gate bipolar transistor Q803, wherein a third pin of the insulated gate bipolar transistor Q800 and a third pin of the insulated gate bipolar transistor Q801 are both connected with the current-limiting inductor; the third pin of the insulated gate bipolar transistor Q802 is connected with the second pin of the insulated gate bipolar transistor Q800, the second pin of the insulated gate bipolar transistor Q802 is connected with the second pin of the insulated gate bipolar transistor Q803, and the third pin of the insulated gate bipolar transistor Q803 is connected with the second pin of the insulated gate bipolar transistor Q801.

3. The inductive current-limiting circuit of claim 2, wherein: the control circuit comprises an AND gate U1A, an AND gate U1B, an AND gate U1C and an AND gate U1D, wherein a third pin of the AND gate U1A is connected with a first pin of an insulated gate bipolar transistor Q800 through a resistor R1; the third pin of the AND gate U1B is connected with the first pin of the insulated gate bipolar transistor Q801 through a resistor R2; the third pin of the and gate U1C is connected to the first pin of the igbt Q802 through a resistor R3; and the third pin of the and gate U1D is connected to the first pin of the igbt Q803 through a resistor R4.

4. The inductive current-limiting circuit of claim 1, wherein: the detection circuit comprises an operational amplifier U807 and resistors R811, R800, R801, R816 and R814, wherein a fourth pin of the operational amplifier U807 is connected with the control circuit, and a third pin of the operational amplifier U807 is connected with the IGBT-H bridge circuit through the resistor R811.

5. The inductive current-limiting circuit of claim 1, wherein: and the current sampling resistor R813 is arranged between the negative electrode of the high-voltage capacitor and the IGBT-H bridge circuit.

6. The inductive current-limiting circuit of claim 1, wherein: the current-limiting inductor further comprises a diode D800, a diode D801 and a diode D802 which are sequentially connected in series, wherein the diode D800, the diode D801 and the diode D802 are connected with the current-limiting inductor in parallel, and the anode of the diode D802 is connected with the IGBT-H bridge circuit.

7. The inductive current-limiting circuit of claim 3, wherein: the AND gate U1A, the AND gate U1B, the AND gate U1C and the AND gate U1D are 74LVC08 AND gates.

8. The inductive current-limiting circuit of claim 4, wherein: the operational amplifier U807 is an LMV331 operational amplifier.