High-reliability overcurrent protection system circuit and application thereof

Abstract

This invention discloses a high-reliability overcurrent protection system circuit and its application, belonging to the field of AED technology. It includes a load module comprising an electrical load and a sampling resistor connected in series with the electrical load. The sampling resistor is used to convert the load current into a differential voltage signal. This invention establishes a dual-path overcurrent protection architecture by setting up a differential operational amplifier for continuous monitoring and a high-speed comparator for rapid triggering. The ADC of the control module performs accurate current monitoring and rapid overcurrent protection, while the high-speed comparator provides nanosecond-level fast response protection. The two are redundant, greatly improving the reliability of overcurrent protection. Furthermore, the use of a hardware high-speed comparator for threshold judgment avoids the delay caused by traditional pure software sampling, achieving nanosecond-level response time and real-time protection of sensitive circuits. During the high-voltage discharge process of the AED, it can quickly cut off the circuit in the early stages of current abnormality, protecting core components.

Description

Technical Field

[0001] This invention belongs to the field of AED technology, and in particular to a high-reliability overcurrent protection system circuit and its application. Background Technology

[0002] An automated external defibrillator (AED) is a portable medical device used to treat patients suffering from sudden cardiac arrest. It generates a high-voltage pulse to the heart, thereby terminating ventricular fibrillation and restoring the heart to a normal rhythm. More than 80% of sudden cardiac deaths are caused by malignant arrhythmias such as ventricular fibrillation. The AED is currently the only medical device capable of effective early electrical defibrillation, and it is of great significance in saving patients' lives.

[0003] During operation, AED devices charge their internal high-voltage energy storage capacitors and deliver defibrillation pulses to the patient via an H-bridge circuit. This process involves drastic current fluctuations in the circuit, particularly the large instantaneous current generated during discharge, which can easily damage the control circuitry. Furthermore, as portable medical devices, AEDs are frequently carried and used by non-professionals, exposing them to various electrical hazards such as electrostatic discharge, battery overcurrent, and motor or high-voltage circuit malfunctions. Any power or communication interface can become an entry point for electrical transients; therefore, circuit protection design is crucial for ensuring the safety and reliability of medical devices.

[0004] Traditional overcurrent protection schemes mainly employ the following methods: Fuse protection: Overcurrent protection is achieved by connecting a fuse in series in the circuit. When the current exceeds the rated value, the fuse melts and cuts off the circuit. This method has a slow response time, and once it blows, it needs to be replaced and cannot self-recover, making it unsuitable for AED devices with extremely high reliability requirements.

[0005] Semiconductor device protection: Overcurrent detection is performed using power switching devices in conjunction with simple sampling resistors. While this method can achieve overcurrent shutdown, it typically provides only a single overcurrent detection channel and lacks redundancy. If the detection circuit itself fails, the protection function will fail.

[0006] Passive component protection: such as positive temperature coefficient (PTC) thermistors, can limit current when an overload occurs and automatically reset after the overload disappears. However, this method has a slow response speed and low accuracy, and cannot meet the precise protection requirements of AED devices for high-voltage discharge circuits.

[0007] The aforementioned existing technology has the following problems: The circuit response speed is slow: Traditional software sampling methods require ADC conversion and software judgment, which results in a large delay and cannot respond to overcurrent events within nanoseconds, potentially missing the protection window.

[0008] Without dual protection mechanism: If a single protection channel fails, the entire overcurrent protection function is lost, and the system reliability cannot be guaranteed.

[0009] The protection circuit lacks a self-test function: Traditional overcurrent protection circuits cannot determine whether they are functioning properly. In scenarios where AED devices are left idle for extended periods, it is impossible to confirm whether the overcurrent detection circuit is in a healthy state, posing a risk of protection failure.

[0010] Accuracy and speed are difficult to balance: high-precision sampling usually requires complex signal processing and has a slow response speed; fast protection usually sacrifices accuracy and cannot achieve continuous monitoring of current.

[0011] The purpose of this invention is to provide a highly reliable overcurrent protection system circuit and its application to solve the problems mentioned in the background art. Summary of the Invention

[0012] The purpose of this invention is to provide a highly reliable overcurrent protection system circuit to solve the problems mentioned in the background art.

[0013] To achieve the above objectives, the present invention provides the following technical solution: a high-reliability overcurrent protection system circuit, characterized in that it includes: a load module, comprising an electrical load and a sampling resistor connected in series with the electrical load, wherein the sampling resistor is used to convert the load current into a differential voltage signal; The differential amplifier module has its input terminal connected to both ends of the sampling resistor, and is used to receive and amplify the differential voltage signal, and output an analog voltage signal proportional to the load current. A high-speed comparator module has its first input terminal connected to the output terminal of the differential amplifier module, and its second input terminal connected to a preset overcurrent threshold voltage. It is used to compare the analog voltage signal with the overcurrent threshold voltage and output a digital overcurrent trigger signal. A control module is connected to the output of the differential amplifier module and the output of the high-speed comparator module, respectively. The control module includes an analog-to-digital converter unit and a power switching device. The control module receives the analog voltage signal in real time through the analog-to-digital conversion unit to achieve continuous current monitoring, and also receives the digital overcurrent trigger signal. The control module is also used to control the power switching device to cut off the power supply circuit of the load module when the digital overcurrent trigger signal is received.

[0014] Furthermore, the control module is also used to verify the authenticity of the digital overcurrent trigger signal output by the high-speed comparator module using the analog voltage signal acquired by the analog-to-digital conversion unit.

[0015] Furthermore, the high-speed comparator module includes a hysteresis comparator circuit, which is used to set a comparison threshold to suppress output jitter.

[0016] Furthermore: the control module also includes a digital-to-analog converter unit, the output of which is connected to the input of the differential amplifier module or the input of the high-speed comparator module; The control module is used to output test signals through the digital-to-analog converter unit to perform self-testing on the circuit functions of the differential amplifier module and / or the high-speed comparator module.

[0017] Furthermore: the control module is used to output a first test voltage through the digital-to-analog converter unit, and to acquire a first output value of the differential amplifier module corresponding to the first test voltage through the analog-to-digital converter unit, and to determine whether the differential amplifier module is normal based on the comparison result of the first output value and the preset gain.

[0018] Furthermore: the control module is used to output a second test voltage through the digital-to-analog converter unit and detect whether the digital overcurrent trigger signal output by the high-speed comparator module is received, so as to determine whether the high-speed comparator module is normal; wherein, after the second test voltage is amplified by the differential amplifier module, its voltage value is greater than the overcurrent threshold voltage.

[0019] Furthermore, the control module also includes a non-volatile memory for recording fault information when overcurrent protection is triggered.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention employs a dual-path overcurrent protection architecture, consisting of continuous monitoring by a differential operational amplifier and rapid triggering by a high-speed comparator. The ADC of the control module performs precise current monitoring and rapid overcurrent protection, while the high-speed comparator provides nanosecond-level fast response protection. The two are redundant, greatly improving the reliability of overcurrent protection. The use of a hardware high-speed comparator for threshold judgment avoids the delay caused by traditional pure software sampling, achieving nanosecond-level response time and real-time protection of sensitive circuits. During the high-voltage discharge process of an AED, it can quickly cut off the circuit in the early stages of current abnormality, protecting core components.

[0021] This invention utilizes the DAC output of the control module to output a specific test voltage, actively verifying the amplification factor of the differential operational amplifier and the response capability of the high-speed comparator. The end-to-end self-test function can detect faults in the sampling circuit during power-on or operation, preventing the loss of protection functions due to the failure of the detection circuit itself, significantly improving the safety and reliability of the system. Furthermore, the high common-mode rejection ratio (CMRR) of the differential operational amplifier effectively suppresses common-mode interference on the sampling line, achieving high-precision detection of minute current changes. The hysteresis design of the high-speed comparator avoids false triggering caused by noise, ensuring the accuracy and stability of the overcurrent signal. (See attached figures.) To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the control module of the present invention; Figure 2 The circuit in this invention Figure 1 Schematic diagram; Figure 3 The circuit in this invention Figure 2 Schematic diagram. Detailed Implementation

[0023] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0024] Unless otherwise defined, the directions mentioned herein, such as up, down, left, right, front, back, inside, and outside, are based on the directions shown in the figures of this invention, and are explained here together.

[0025] The connection method can be any existing method, such as bonding, welding, or bolting, depending on the actual needs.

[0026] like Figure 1 As shown, the overcurrent protection circuit in this embodiment includes: Load module: Contains the AED's high-voltage discharge load (such as an H-bridge discharge circuit and patient chest impedance) and a precision sampling resistor (0.01Ω~0.1Ω, 1% accuracy) connected in series with the load. The sampling resistor converts the discharge current into a millivolt-level differential voltage signal. Auxiliary components include fuses, TVS diodes (for ESD protection), and filter capacitors.

[0027] Differential amplifier module: Employs the high-precision instrumentation amplifier INA213, with its input connected to the sampling resistor. The INA213 features a high common-mode rejection ratio (>100dB) and low offset voltage (<100μV), capable of amplifying weak differential voltages to a range of 0~3.3V, outputting an analog voltage signal proportional to the discharge current. Peripheral circuitry includes a gain setting resistor (amplification factor set to 50~100 times), input protection diodes, and power supply decoupling capacitors.

[0028] High-speed comparator module: Employs the high-speed voltage comparator LMV7219. Its non-inverting input is connected to the output of the differential amplifier module, while its inverting input is connected to the overcurrent threshold voltage (corresponding to the upper limit of the discharge current, such as 50A) set by a precision voltage divider resistor. The comparator output is connected to the GPIO pin of the control module via a pull-up resistor. Hysteresis resistors (10kΩ~100kΩ) are included in the module to set a hysteresis voltage of approximately 50mV, preventing jitter due to noise near the threshold.

[0029] Control Module: Employs an STM32 series microcontroller with a built-in 12-bit ADC and 12-bit DAC. The ADC input is connected to the output of the differential amplifier module for real-time acquisition of the analog signal of the discharge current. The DAC output is connected to the input of the differential amplifier module via an analog switch (for self-test). The power switching device uses MOSFETs (such as IRF540), connected in series in the load power supply circuit and controlled by the MCU's GPIO. The module also includes non-volatile flash memory (for recording overcurrent event logs), status indicator LEDs, and a communication interface (UART / CAN).

[0030] Working principle: Normal operating phase: When the AED is in standby or charging mode, the circuit continuously monitors the current. When the device performs a defibrillation operation, the high-voltage discharge circuit is activated, and the current flows through the sampling resistor to generate a differential voltage. The differential amplifier module amplifies this voltage and outputs an analog voltage signal Vout, which is simultaneously sent to the ADC and high-speed comparator modules of the control module.

[0031] Continuous current monitoring: The control module continuously monitors the discharge current by acquiring Vout in real time via an ADC at a sampling rate of 1kHz~10kHz. A slow overcurrent threshold (slightly higher than the fast threshold for redundancy verification) is set in the software. If an abnormal current is detected but has not reached the fast threshold, the circuit can be cut off via software control.

[0032] Fast overcurrent protection: The high-speed comparator module compares Vout with a preset overcurrent threshold Vth. When the discharge current abnormally increases and Vout exceeds Vth, the comparator output immediately jumps from low to high, sending a digital overcurrent trigger signal to the control module. This trigger signal can be used as a high-priority interrupt input, and the control module immediately shuts down the power MOSFET and cuts off the discharge circuit in the interrupt service routine. The entire process is a purely hardware response, with a delay only the comparator's propagation delay (nanosecond level), achieving extremely fast overcurrent protection.

[0033] Redundancy check: After receiving the digital trigger signal from the comparator, the control module reads the analog voltage value acquired by the ADC for confirmation. If the two are consistent, it is confirmed as a real overcurrent event; if the ADC reading does not reach the threshold, it is judged as a comparator false trigger, the abnormality can be recorded but the protection action is not executed temporarily to avoid false protection.

[0034] Self-test function The key innovation of this embodiment lies in its fully closed-loop self-test function. The self-test process is executed during the AED device's power-on self-test or during standby idle time, and includes the following steps: Step 1: Differential Amplifier Module Self-Test The control module outputs a first test voltage X (e.g., 0.5V) via a DAC, which is injected into the input of the differential amplifier module. According to the circuit design, the differential amplifier module should amplify this test voltage by a preset value G (e.g., 50 times). The control module acquires the output voltage Y of the differential amplifier module via an ADC and calculates the actual amplification factor G' = Y / X. If the deviation between G' and G is within the allowable range (e.g., ±5%), the differential amplifier module is considered normal; otherwise, a fault is recorded.

[0035] Step 2: High-speed comparator module self-test The control module outputs a second test voltage Y_test via a DAC. This voltage is calculated to ensure that, after amplification by the differential amplifier module, its value is greater than the overcurrent threshold voltage. Specifically, X_test is selected such that G × X_test > Vth. Theoretically, injecting this test voltage should trigger the high-speed comparator, outputting a digital overcurrent signal. The control module checks for a comparator interrupt signal; if received, the comparator module is considered normal; otherwise, a fault is recorded.

[0036] By performing the above self-test, it is possible to confirm whether the entire overcurrent detection link (differential amplifier + comparator + interrupt response) is intact before using the equipment, thus avoiding the loss of protection function due to detection circuit failure.

[0037] Fault logging and communication When an overcurrent event occurs, the control module writes information such as the time of the fault, the current value, and the trigger source (ADC monitoring trigger / comparator trigger) into non-volatile memory. Simultaneously, it sends fault alarm information to the host computer via the UART / CAN interface, supporting remote monitoring and fault troubleshooting.

[0038] Example 2: Applied to AED motor drive circuit This embodiment applies the invention to the drive circuit of an AED device. AED devices may generate a large current upon startup, requiring overcurrent protection.

[0039] The sampling resistor value should be appropriately increased (e.g., 0.1Ω~1Ω) to accommodate a smaller current range; The gain of the differential amplifier module is adjusted accordingly to adapt the output voltage range to 0~3.3V; The overcurrent threshold is set according to the motor's rated current (e.g., 1.5 to 2 times the rated current).

[0040] The workflow is the same as in Example 1, realizing dual overcurrent protection and self-test functions for the motor drive circuit.

[0041] Example 3: Application in AED power management circuit This embodiment applies the present invention to the power management circuit of an AED device, including a battery charging circuit and a DC-DC conversion circuit.

[0042] In battery charging circuits, overcurrent protection is used to prevent excessive charging current from damaging the battery; in DC-DC conversion circuits, it is used to prevent output short circuits or overloads. The circuit structure is the same as above, with multiple sampling resistors monitoring the current of different power paths, and the control module cuts off the corresponding power switches based on the overcurrent trigger signal.

[0043] Self-test process example Specifically as follows: S101: The system is powered on or has entered self-test mode; S102: The control module outputs the first test voltage X1 via the DAC; S103: ADC acquisition differential amplifier module output Vout1; S104: Calculate the actual gain G1 = Vout1 / X1, and determine if |G1-G| < ΔG? If yes, proceed to S105; otherwise, record "Differential amplifier module failure". S105: The control module outputs a second test voltage X2 via the DAC to ensure that G×X2 > Vth; S106: Wait for a preset time (e.g., 10ms) to check if a comparator interrupt signal is received; S107: Determine if an interrupt has been received. If yes, record "Comparator module normal"; if no, record "Comparator module fault". S108: Self-inspection complete, report self-inspection results.

[0044] Component selection guide: According to specific embodiments of the present invention, the following typical devices may be selected: It should be noted that, in this document, relational terms such as "one" and "two" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, the phrase "comprising an element defined as..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-reliability overcurrent protection system circuit, characterized in that: include: A load module includes an electrical load and a sampling resistor connected in series with the electrical load, the sampling resistor being used to convert the load current into a differential voltage signal; The differential amplifier module has its input terminal connected to both ends of the sampling resistor, and is used to receive and amplify the differential voltage signal, and output an analog voltage signal proportional to the load current. A high-speed comparator module has its first input terminal connected to the output terminal of the differential amplifier module, and its second input terminal connected to a preset overcurrent threshold voltage. It is used to compare the analog voltage signal with the overcurrent threshold voltage and output a digital overcurrent trigger signal. A control module is connected to the output of the differential amplifier module and the output of the high-speed comparator module, respectively. The control module includes an analog-to-digital converter unit and a power switching device. The control module receives the analog voltage signal in real time through the analog-to-digital conversion unit to achieve continuous current monitoring, and also receives the digital overcurrent trigger signal. The control module is also used to control the power switching device to cut off the power supply circuit of the load module when the digital overcurrent trigger signal is received.

2. The high-reliability overcurrent protection system circuit according to claim 1, characterized in that: The control module is also used to verify the authenticity of the digital overcurrent trigger signal output by the high-speed comparator module by using the analog voltage signal acquired by the analog-to-digital conversion unit.

3. The high-reliability overcurrent protection system circuit according to claim 1, characterized in that: The high-speed comparator module includes a hysteresis comparator circuit, which is used to set a comparison threshold to suppress output jitter.

4. The high-reliability overcurrent protection system circuit according to claim 1, characterized in that: The control module also includes a digital-to-analog converter unit, the output of which is connected to the input of the differential amplifier module or the input of the high-speed comparator module. The control module is used to output test signals through the digital-to-analog converter unit to perform self-testing on the circuit functions of the differential amplifier module and / or the high-speed comparator module.

5. A high-reliability overcurrent protection system circuit according to claim 4, characterized in that: The control module is used to output a first test voltage through the digital-to-analog converter unit, and to acquire a first output value of the differential amplifier module corresponding to the first test voltage through the analog-to-digital converter unit. Based on the comparison result of the first output value and the preset gain, the control module determines whether the differential amplifier module is normal.

6. The high-reliability overcurrent protection system circuit according to claim 4, characterized in that: The control module is used to output a second test voltage through the digital-to-analog converter unit and detect whether the digital overcurrent trigger signal output by the high-speed comparator module is received, so as to determine whether the high-speed comparator module is normal; wherein, after the second test voltage is amplified by the differential amplifier module, its voltage value is greater than the overcurrent threshold voltage.

7. The high-reliability overcurrent protection system circuit according to claim 1, characterized in that: The control module also includes a non-volatile memory for recording fault information when overcurrent protection is triggered.

8. Application of a high-reliability overcurrent protection system circuit, as described in claims 1-7, characterized in that: It is used in the protection current circuit of AED devices.

Images