Load protection circuit and method for power supply module of medical equipment

Abstract

The invention provides a load protection circuit and method for a power supply module of medical equipment, and relates to the technical field of medical power distribution. One side of the energy absorption circuit is connected with the output direct current port, and the other side of the energy absorption circuit is connected with the input end of the medical device; the driving sub-circuit is electrically connected with the energy absorption circuit; the energy absorption main circuit comprises a voltage sampling unit, a comparison unit, a driving unit and a power switch unit; and the output end of the relaxation oscillator of the driving sub-circuit is connected with the control end of the driving unit in the energy absorption main circuit. The system has the advantages of extremely high reliability, long service life, ultra-fast response, active protection, strong energy absorption capability, excellent anti-interference performance and stability, and the intelligentization and manageability of the system are enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medical power distribution, in particular to a medical equipment power module load protection circuit. BACKGROUND

[0002] In the medical equipment power supply system, due to the switching action, power supply switching or fault state of the load such as CT, MRI, DSA, X-ray machine and other image diagnosis and treatment equipment, the output end of the power supply module often produces instantaneous high voltage peak or voltage surge. These overvoltage phenomena not only may damage the power supply module itself, but also may cause permanent damage to the precision medical equipment such as CT, MRI, DSA, X-ray machine and other image diagnosis and treatment equipment connected thereto, affecting medical safety. In addition, when the medical equipment is powered off, the energy stored in the inductive load inside the medical equipment will be released in the form of reverse electromotive force, which may also impact the power supply circuit.

[0003] The existing energy absorption circuit uses a combination of relays and resistors, which is realized by increasing the relay control circuit. However, the relay contact surface is oxidized or contaminated, forming a thin film that hinders the passage of current, affecting the circuit conduction, resulting in poor reliability and slow response of the power module load protection circuit; secondly, the contact area is reduced due to mechanical wear during long-term use, affecting the load carrying capacity; thirdly, the contact pressure is insufficient, so that the contacts cannot form good contact, affecting the reliability of the circuit. SUMMARY

[0004] The present application aims to solve the problem of poor conduction and poor reliability of the existing power module load protection circuit.

[0005] To solve the above problems, the present application provides a medical equipment power module load protection circuit, which comprises an energy absorption circuit and a drive sub-circuit; one side of the energy absorption circuit is connected with an output DC port, and the other side of the energy absorption circuit is connected with a medical device input end; the drive sub-circuit is electrically connected with the energy absorption circuit; The energy absorption main circuit comprises a voltage sampling unit, a comparison unit, a drive unit and a power switch unit; the voltage sampling unit is connected to the output DC port for outputting a sampling signal proportional to the DC output voltage; the first input end of the comparison unit is connected to the output end of the voltage sampling unit, and the second input end of the comparison unit is connected to a reference voltage source for comparing the sampling signal with the reference voltage and outputting a control signal; the input end of the drive unit is connected to the output end of the comparison unit; the control end of the power switch unit is connected to the output end of the drive unit, the first power end of the power switch unit is connected to the output DC port through an absorption resistor, and the second power end of the power switch unit is grounded; The drive sub-circuit comprises a relaxation oscillator for generating a square wave signal of a fixed frequency; and an output terminal of the relaxation oscillator is connected with a control terminal of a drive unit in the energy absorption main circuit.

[0006] The medical equipment power supply module load protection circuit provided by the application has the following advantages, but is not limited to the following advantages: The application has high reliability and long service life, discards mechanical relays, and adopts full solid-state electronic devices, i.e., operational amplifiers, MOSFETs, resistors and capacitors. There are no moving parts, no contact oxidation, no wear and tear, and no pressure deficiency problems. The theoretical service life depends on semiconductor devices, far exceeds that of mechanical relays, and can reach several decades, truly realizing maintenance-free.

[0007] The application has super-fast response and active protection. Based on high-speed operational amplifiers, the response time can reach microseconds, which is much faster than the millisecond-level response of relays. The application can actively intervene in the early stage of voltage peak generation, kill the harm in the embryonic state, and has more complete protection effect.

[0008] The application has strong energy absorption capacity. Special power MOSFETs and absorption resistors are used, device parameters can be flexibly selected according to the size of expected overvoltage energy, the through-flow capacity is strong, and large-energy voltage surges and reverse electromotive forces can be safely and effectively absorbed, and the protection level is high.

[0009] The application has excellent anti-interference and stability. Filtering and hysteresis designs are introduced in multiple places in the circuit, which can effectively suppress power supply noise and glitch interference, and prevent misoperation. The use of a reference source ensures the high precision and temperature stability of the protection threshold.

[0010] The application has a double protection mechanism. The comparator detects and controls the conduction of the MOSFET, and the forward overvoltage absorption comes from the voltage peak of the power supply module side. The parasitic diode inside the power MOSFET or the external parallel diode is used. When the reverse electromotive force is generated when the load is powered off, the diode is naturally turned on, a discharge loop is formed through the absorption resistor, and the control circuit does not need to participate.

[0011] The application has flexible expansion and optimization capability. The PWM signal generated by the drive sub-circuit provides an additional control dimension. It can be used to realize an intermittent protection mode to reduce power consumption, or as a trigger signal for system self-checking, enhancing the intelligence and manageability of the system.

[0012] Furthermore, the energy absorption circuit includes a first sampling resistor R1, a second sampling resistor R2, a first current-limiting resistor R3, a second current-limiting resistor R4, a first filter capacitor C1, a Zener diode D1, a first operational amplifier U1, a third current-limiting resistor R7, a push-pull circuit Q1, a MOSFET Q2, a fourth current-limiting resistor R8, a fifth current-limiting resistor R9, a second filter resistor R10, a diode D2, and an absorption resistor R11. The positive terminal of the output DC port, the first sampling resistor R1, the second sampling resistor R2, and the negative terminal of the output DC port are connected in series. A first filter capacitor C1 is connected in parallel across the two ends of the second sampling resistor R2; A Zener diode D1 is connected in parallel across the two ends of the second sampling resistor R2, and the positive terminal of the Zener diode D1 is connected to the negative terminal of the output DC power port. The negative terminal of Zener diode D1 is electrically connected to the positive input terminal of the first operational amplifier U1 through the first current-limiting resistor R3; One end of the second current-limiting resistor R4 is connected to a 3V reference source, and the other end of the second current-limiting resistor R4 is electrically connected to the negative input terminal of the first amplifier U1. One end of the third current-limiting resistor R7 is connected to the output of the operational amplifier U1, and the other end of the third current-limiting resistor R7 is connected to the input of the push-pull circuit Q1. The output terminal of the push-pull circuit Q1 is connected to the negative terminal of diode D2, the positive terminal of diode D2 is connected to one end of the fifth current-limiting resistor R9, and the other end of the fifth current-limiting resistor R9 is connected to the gate of MOSFET Q2. A fourth current-limiting resistor R8 is connected in parallel across the two ends of diode D2; The gate of MOSFET Q2 is connected to one end of the second filter resistor R10, and the other end of the second filter resistor R10 is grounded. The source of MOSFET Q2 is grounded, and the drain of MOSFET Q2 is connected to the input terminal of the medical device through the energy absorption resistor R11.

[0013] Furthermore, the positive input terminal of the first operational amplifier U1 is electrically connected to one end of the gain feedback resistor R6, and the other end of the gain feedback resistor R6 is electrically connected to the output terminal of the first operational amplifier U1.

[0014] Furthermore, the negative input terminal of the operational amplifier U1 is electrically connected to one end of the second filter capacitor C2, and the other end of the second filter capacitor C2 is grounded; the first filter resistor R5 is connected in parallel with the second filter capacitor C2.

[0015] Furthermore, the driving sub-circuit includes a second operational amplifier U2, the negative input terminal of the second operational amplifier U2 is connected to one end of a first-order RC capacitor C3, and the other end of the first-order RC capacitor C3 is grounded; The positive input terminal of the second operational amplifier U2 is connected to one end of the first hysteresis resistor R13, and the other end of the first hysteresis resistor R13 is connected to a 12V power supply. The output of the second operational amplifier U2 is connected to one end of the sixth current-limiting resistor R16, and the other end of the sixth current-limiting resistor R16 outputs a square wave signal to the input of the push-pull circuit Q1 section of the energy absorption circuit.

[0016] Furthermore, the positive input terminal of the second operational amplifier U2 is connected to one end of the second hysteresis resistor R14, and the other end of the second hysteresis resistor R14 is connected to the output terminal of the second operational amplifier U2. The positive input terminal of the second operational amplifier U2 is connected to one end of the third filter resistor R15, and the other end of the third filter resistor R15 is grounded.

[0017] Furthermore, the negative input terminal of the second operational amplifier U2 is connected to one end of the first-order RC resistor R12, and the other end of the first-order RC resistor R12 is connected to the output terminal of the second operational amplifier U2.

[0018] Furthermore, the power supply terminal of the second operational amplifier U2 is connected to a 12V power supply, and the ground terminal of the second operational amplifier U2 is grounded.

[0019] A method for protecting the load of a power supply module for medical devices includes the following steps: S1: Real-time sampling and filtering of the output DC port voltage of the power supply module to obtain a voltage feedback signal; S2: Compare the voltage feedback signal with a reference voltage. When the voltage feedback signal exceeds the upper threshold voltage set by the reference voltage, an overvoltage trigger signal is generated. S3: Amplify the overvoltage trigger signal to generate a strong drive signal; S4: A power switching device is turned on by using a strong drive signal, so that an absorption resistor is connected between the output DC port and ground, forming a low-impedance energy discharge path to absorb voltage spikes or reverse electromotive force. S5: When the voltage feedback signal drops below the lower threshold voltage set by the reference voltage, the overvoltage trigger signal and the strong drive signal are canceled, the power switching device is turned off, and the absorption resistor is disconnected from the circuit.

[0020] Furthermore, in step S2, a hysteresis comparison is formed by introducing positive feedback, where the upper threshold voltage is higher than the reference voltage and the lower threshold voltage is lower than the reference voltage. Attached Figure Description

[0021] Fig. 1 This is a schematic diagram of the load protection circuit of the medical device power supply module according to an embodiment of the present invention; Fig. 2 This is a schematic diagram of the energy absorption circuit in the load protection circuit of the medical device power supply module according to an embodiment of the present invention; Fig. 3 This is a schematic diagram of the drive sub-circuit of the load protection circuit of the medical device power supply module in an embodiment of the present invention.

[0022] Explanation of reference numerals in the attached diagram: R1, first sampling resistor; R2, second sampling resistor; R3, first current limiting resistor; R4, second current limiting resistor; C1, first filter capacitor; C2, second filter capacitor; R5, first filter resistor; R6, hysteresis feedback resistor; D1, Zener diode; U1, first operational amplifier; R7, third current limiting resistor; Q1, push-pull circuit; Q2, MOSFET; R8, fourth current limiting resistor; R9, fifth current limiting resistor; R10, second filter resistor; D2, diode; R11, absorption resistor; R12, first-order RC resistor; C3, first-order RC capacitor; R13, first hysteresis resistor; R14, second hysteresis resistor; U2, second operational amplifier; R15, third filter resistor; R16, sixth current limiting resistor. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings showing multiple embodiments according to this application. It should be understood that the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments described in this application without creative effort will fall within the scope of protection of this application.

[0024] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing specific embodiments only and is not intended to limit this application; the terms "comprising," "including," "having," "containing," etc., in the description, claims, and accompanying drawings of this application are open-ended terms. Therefore, "comprising," "including," or "having" refers to, for example, a method or apparatus having one or more steps or elements, but is not limited to having only these one or more elements. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this invention, it should be understood that the terms "upper", "lower", "left", "right", "front", "rear", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0026] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0027] It should be emphasized that when the term "comprising / including" is used in this specification, it is used to explicitly indicate the presence of the stated feature, integer, step, or component, but does not exclude the presence or addition of one or more other features, integers, steps, parts, or groups of features, integers, steps, or parts.

[0028] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0029] See Figs. 1-3 A load protection circuit for a medical device power supply module according to an embodiment of the present invention includes an energy absorption circuit and a drive sub-circuit; one side of the energy absorption circuit is connected to the output DC power port, and the other side of the energy absorption circuit is connected to the input terminal of the medical device; the drive sub-circuit is electrically connected to the energy absorption circuit. The energy absorption main circuit includes a voltage sampling unit, a comparison unit, a drive unit, and a power switch unit. The voltage sampling unit is connected to the output DC port and is used to output a sampling signal proportional to the DC output voltage. The first input terminal of the comparison unit is connected to the output terminal of the voltage sampling unit, and the second input terminal of the comparison unit is connected to a reference voltage source to compare the sampling signal with the reference voltage and output a control signal. The input terminal of the drive unit is connected to the output terminal of the comparison unit. The control terminal of the power switch unit is connected to the output terminal of the drive unit. The first power terminal of the power switch unit is connected to the output DC port through an absorption resistor, and the second power terminal of the power switch unit is grounded. The driving sub-circuit includes a relaxation oscillator for generating a square wave signal at a fixed frequency; the output of the relaxation oscillator is connected to the control terminal of the driving unit in the energy absorption main circuit.

[0030] This invention provides an all-solid-state circuit architecture based on active detection, bidirectional discharge, and intelligent drive. Through the coordinated design and specific connection of voltage sampling and hysteresis comparison unit, power switch and absorption unit, and independent oscillation drive unit, it not only realizes the function replacement of relay, but also achieves breakthrough improvements in response speed, reliability, anti-interference, energy handling capability, and system intelligence.

[0031] This invention employs a specific combination of a high-speed operational amplifier U1 forming a hysteresis comparator and a push-pull drive circuit Q1 directly coupled, compressing the entire response time of the detection-decision-drive chain to the microsecond level. The high-speed characteristics of the comparator itself, combined with the rapid charging and discharging capability of the MOSFET gate capacitor by the push-pull circuit, result in an extremely short time from voltage over-threshold to the full conduction of the MOSFET Q2. This ensures that voltage spikes are clamped early on the rising edge, nipping potential threats in the bud, achieving true active and instantaneous protection. The thoroughness of this protection far surpasses conventional solutions with detection delays or drive hysteresis.

[0032] This invention innovatively introduces a drive sub-circuit composed of an independent relaxation oscillator, which generates a fixed-frequency square wave signal as an additional control dimension injected into the main protection circuit. During non-sustained overvoltage periods, the square wave signal allows the protection circuit to periodically and intermittently conduct, maintaining monitoring status while significantly reducing the continuous heating and static power consumption of power devices and absorption resistors, achieving intermittent protection mode and extending component lifespan. This square wave can also serve as a periodic trigger signal to verify the normality of the entire operating link from the comparator to the power switch, providing a system self-test signal and realizing the online self-diagnostic function of the protection circuit, which is difficult to achieve with conventional solid-state or relay solutions.

[0033] This invention utilizes semiconductors and passive devices throughout its circuitry, with no moving mechanical parts. Its theoretical lifespan, determined by the lifespan of the semiconductor devices, can reach decades, truly achieving a "maintenance-free" design with a lifespan comparable to medical equipment. Compared to conventional solid-state solutions, this invention, through the aforementioned multiple design features, achieves a balance and unity of speed, stability, durability, and intelligence at a higher level, without sacrificing response speed and protection capabilities while pursuing a long lifespan.

[0034] This invention is not simply a solid-state relay, but rather a meticulously designed, tightly coupled all-solid-state circuit topology and control method that produces technical effects that exceed the expectations of those skilled in the art and are significantly superior to ordinary solid-state protection schemes in terms of response speed (microsecond-level active protection), anti-interference capability (multi-layer filtering and hysteresis lockout), protection completeness (active and passive bidirectional discharge), system intelligence (intermittent operation and self-test), and ultimate reliability. It is particularly suitable for power supply scenarios of medical equipment with extreme requirements for safety, reliability, and stability.

[0035] This invention boasts extremely high reliability and long lifespan, eliminating mechanical relays and employing all-solid-state electronic components, namely operational amplifiers, MOSFETs, resistors, and capacitors. With no moving parts, it eliminates problems such as contact oxidation, wear, and insufficient pressure. Its theoretical lifespan, dependent on the semiconductor devices, far exceeds that of mechanical relays, reaching decades, truly achieving maintenance-free operation.

[0036] This invention features ultra-fast response and proactive protection. Based on a high-speed operational amplifier, its response time reaches the microsecond level, far faster than the millisecond response of a relay. It can proactively intervene at the very early stage of voltage spikes, nipping potential hazards in the bud and providing more thorough protection.

[0037] This invention has a strong energy absorption capability. It uses a dedicated power MOSFET and absorption resistor, and the device parameters can be flexibly selected according to the expected overvoltage energy. It has a strong current carrying capacity and can safely and effectively absorb large-energy voltage surges and reverse electromotive forces, with a high protection level.

[0038] This invention exhibits excellent anti-interference and stability: multiple filtering and hysteresis designs are incorporated into the circuit, effectively suppressing power supply noise and glitches, and preventing malfunctions. The use of a reference source ensures high accuracy and temperature stability of the protection threshold.

[0039] This invention features a dual protection mechanism: a comparator detects and controls the MOSFET's conduction to absorb voltage spikes from the power supply module side during forward overvoltage; and it utilizes the unidirectional conductivity of the parasitic body diode inside the power MOSFET or an external parallel diode. When the load is de-energized and a reverse electromotive force is generated (positive at the bottom, negative at the top), the diode naturally conducts, forming a discharge circuit through the absorption resistor. No control circuit is required, and the reverse electromotive force absorption achieves fully passive, zero-delay reverse protection.

[0040] This invention offers flexible expansion and optimization capabilities, with the PWM signal generated by the drive sub-circuit providing an additional control dimension. It can be used to implement intermittent protection modes to reduce power consumption, or as a trigger signal for system self-testing, enhancing the system's intelligence and manageability.

[0041] Furthermore, the energy absorption circuit includes a first sampling resistor R1, a second sampling resistor R2, a first current-limiting resistor R3, a second current-limiting resistor R4, a first filter capacitor C1, a Zener diode D1, a first operational amplifier U1, a third current-limiting resistor R7, a push-pull circuit Q1, a MOSFET Q2, a fourth current-limiting resistor R8, a fifth current-limiting resistor R9, a second filter resistor R10, a diode D2, and an absorption resistor R11. The positive terminal of the output DC port, the first sampling resistor R1, the second sampling resistor R2, and the negative terminal of the output DC port are connected in series. A first filter capacitor C1 is connected in parallel across the two ends of the second sampling resistor R2; A Zener diode D1 is connected in parallel across the two ends of the second sampling resistor R2, and the positive terminal of the Zener diode D1 is connected to the negative terminal of the output DC power port. The negative terminal of Zener diode D1 is electrically connected to the positive input terminal of the first operational amplifier U1 through the first current-limiting resistor R3; One end of the second current-limiting resistor R4 is connected to a 3V reference source, and the other end of the second current-limiting resistor R4 is electrically connected to the negative input terminal of the first amplifier U1. One end of the third current-limiting resistor R7 is connected to the output of the operational amplifier U1, and the other end of the third current-limiting resistor R7 is connected to the input of the push-pull circuit Q1. The output terminal of the push-pull circuit Q1 is connected to the negative terminal of diode D2, the positive terminal of diode D2 is connected to one end of the fifth current-limiting resistor R9, and the other end of the fifth current-limiting resistor R9 is connected to the gate of MOSFET Q2. A fourth current-limiting resistor R8 is connected in parallel across the two ends of diode D2; The gate of MOSFET Q2 is connected to one end of the second filter resistor R10, and the other end of the second filter resistor R10 is grounded. The source of MOSFET Q2 is grounded, and the drain of MOSFET Q2 is connected to the input terminal of the medical device through the energy absorption resistor R11.

[0042] In this application, the first sampling resistor R1 and the second sampling resistor R2 are connected in series for voltage division. The voltage value of the series division is then limited by the Zener diode D1, the first filter capacitor C1, and the first current limiting resistor R3 to obtain a stable and safe voltage value, which is then sent to the positive input terminal of the first operational amplifier. At the same time, it is compared with the reference voltage that flows to the negative input terminal of the first operational amplifier through the second current limiting resistor. When the operating voltage spikes and exceeds the rated value, the first operational amplifier U1 is set high, and the drive circuit is started.

[0043] When the first operational amplifier U1 is set high, the drive circuit is started, and the push-pull circuit Q1 performs drive amplification. The turn-on signal of the MOS transistor is given through the fourth current-limiting resistor R8 and the fifth current-limiting resistor R9. The second filter resistor R10 filters out the drive interference signal. The diode D2 absorbs the reverse electromotive force when the drive is turned off. The energy absorption resistor R11 absorbs the voltage spike energy at the DC output terminal.

[0044] This invention introduces a collaborative filtering and positive feedback lock-in mechanism at several key nodes, forming a multi-layered anti-interference system: at the sampling end, C1 and Zener diode D1 constitute the primary filter and voltage limiter. At the reference end, R5 and C2 form a low-pass filter network to provide an "absolutely quiet" reference voltage for the comparator. In the comparison stage, resistor R6 introduces positive feedback hysteresis, transforming single-point comparison into window comparison with hysteresis. This design ensures that the circuit enters a "locked-in" state once activated, and will only reset when the voltage drops significantly below the trigger point, completely eliminating oscillations or noise-induced false triggering near the threshold point. This design combination performs particularly well in complex electromagnetic environments, such as high-frequency electrosurgical interference, achieving near-zero false triggering stability.

[0045] This invention constructs a natural, non-controllable bidirectional energy discharge path by using a specific connection between the power MOSFET Q2 and the absorption resistor R11, and utilizing the body diode of the MOSFET or an external fast recovery diode D2. Forward overvoltage is actively activated by the control circuit, with the voltage discharged through R11. Reverse electromotive force occurs when a reverse voltage (positive at the bottom and negative at the top) is generated at the load terminal, automatically turning on the body diode of MOSFET Q2 or D2, similarly forming a discharge loop through R11. This process is completely passive and without any delay. This topology provides hardware-level reliability redundancy; even if part of the control circuit fails, the reverse protection function remains intact. Furthermore, the parameters of the power devices and absorption resistor can be flexibly selected according to the most severe expected energy, and the current carrying capacity and energy tolerance far exceed those of relay contacts.

[0046] Furthermore, the positive input terminal of the first operational amplifier U1 is electrically connected to one end of the gain feedback resistor R6, and the other end of the gain feedback resistor R6 is electrically connected to the output terminal of the first operational amplifier U1.

[0047] This invention constitutes a typical positive feedback network. This gives the comparator a memory characteristic. Assuming the initial state is a low output level, when the voltage at the non-inverting input rises from low to high, it needs to exceed an upper threshold voltage higher than 3V before the output flips high. Once flipped, due to positive feedback, the voltage at the non-inverting input is momentarily pulled up slightly by R6, forming a locked state. This greatly enhances the circuit's anti-interference capability in complex electromagnetic environments, such as near high-frequency surgical scalpels in medical equipment or during motor start-stop operations, and completely eliminates malfunctions of the protection circuit.

[0048] Furthermore, the negative input terminal of the operational amplifier U1 is electrically connected to one end of the second filter capacitor C2, and the other end of the second filter capacitor C2 is grounded; the first filter resistor R5 is connected in parallel with the second filter capacitor C2.

[0049] The capacitor C2 and resistor R5 connected in parallel at the output of the reference source form a low-pass filter. Capacitor C2 provides a low-impedance AC path directly to ground for high-frequency noise. Resistors R5 and C2 together set the cutoff frequency of the filter, effectively filtering out noise components in the reference voltage with frequencies higher than this cutoff frequency. This ensures that the comparison reference sent to the negative input of U1 is an extremely quiet DC level, avoiding comparator misjudgments caused by fluctuations in the reference itself.

[0050] like Fig. 3 As shown, further, the driving sub-circuit includes a second operational amplifier U2, the negative input terminal of the second operational amplifier U2 is connected to one end of a first-order RC capacitor C3, and the other end of the first-order RC capacitor C3 is grounded; The positive input terminal of the second operational amplifier U2 is connected to one end of the first hysteresis resistor R13, and the other end of the first hysteresis resistor R13 is connected to a 12V power supply. The output of the second operational amplifier U2 is connected to one end of the sixth current-limiting resistor R16, and the other end of the sixth current-limiting resistor R16 outputs a square wave signal to the input of the push-pull circuit Q1 section of the energy absorption circuit.

[0051] This invention forms the core of a relaxation oscillator, generating a precise square wave signal. The capacitor C3 connected to the negative input of the second operational amplifier U2 is an integrating capacitor, forming a self-excited relaxation oscillator. This circuit can autonomously generate a highly stable square wave signal with a duty cycle close to 50% without relying on an external clock or microcontroller. This square wave signal is the physical carrier driving the sub-circuit's function; its frequency is precisely determined by the RC time constant and the hysteresis voltage threshold, exhibiting good stability and minimal impact from power supply voltage and temperature variations.

[0052] This invention provides a clear signal output interface. The square wave signal is generated from the output of the second operational amplifier U2 and output to the energy absorption main circuit through the sixth current-limiting resistor R16. R16, as the output series resistor, primarily limits the output current. When an abnormality occurs at the input of the push-pull circuit Q1, such as a short circuit to ground, R16 prevents a large current from flowing into the output stage of the second operational amplifier U2, effectively protecting it from damage. R16 also provides isolation and buffering to a certain extent. It reduces the load effect of the input capacitor of the subsequent circuit on the oscillation circuit, especially during the charging and discharging process of C3, helping to maintain the stability of the oscillation frequency and potentially suppressing ringing on the signal line.

[0053] Furthermore, the positive input terminal of the second operational amplifier U2 is connected to one end of the second hysteresis resistor R14, and the other end of the second hysteresis resistor R14 is connected to the output terminal of the second operational amplifier U2.

[0054] The positive input terminal of the second operational amplifier U2 is connected to one end of the third filter resistor R15, and the other end of the third filter resistor R15 is grounded.

[0055] The second operational amplifier U2, resistors R13, R14, and R15 together form a positive feedback comparator. R14 is the positive feedback resistor that feeds the output signal back to the non-inverting input. When the output of the second operational amplifier U2 is high, the voltage division between resistors R14, R13, and R15 establishes a higher voltage at the non-inverting input of the second operational amplifier U2, called the upper threshold voltage. The output will only flip low when the voltage across capacitor C3 at the inverting input is higher than this upper threshold. After the output flips low, the same positive feedback network establishes a lower voltage at the non-inverting input, called the lower threshold voltage. The output will only flip high again when the voltage across capacitor C3 is lower than this lower threshold.

[0056] This invention provides the physical basis for the spontaneous and stable oscillation of a circuit. It ensures that state transitions are defined and inertial, preventing jittering due to noise or minute perturbations near a single threshold, thus achieving a precisely controllable oscillation frequency.

[0057] Furthermore, the negative input terminal of the second operational amplifier U2 is connected to one end of the first-order RC resistor R12, and the other end of the first-order RC resistor R12 is connected to the output terminal of the second operational amplifier U2.

[0058] This invention creates a precise RC charging / discharging circuit. The capacitor C3 connected to ground at the inverting input makes the negative input node of operational amplifier U2 a summing point of an integrator.

[0059] When the output of the second operational amplifier U2 is high, current flows through R12 to capacitor C3, charging C3 with a constant current, causing the voltage at the negative input terminal of the second operational amplifier U2 to rise linearly. When the output of the second operational amplifier U2 is low, the voltage across capacitor C3 is higher than that at the output terminal, and current flows in the reverse direction through R12, discharging C3 with a constant current, causing the voltage at that point to drop linearly.

[0060] This invention provides the physical basis for generating a square wave output with stable frequency and controllable duty cycle. Compared to a simple RC relaxation oscillator, the operational amplifier integrator offers more linear charging and discharging and stronger driving capability.

[0061] Furthermore, the power supply terminal of the second operational amplifier U2 is connected to a 12V power supply, and the ground terminal of the second operational amplifier U2 is grounded.

[0062] Connecting the power rail of the second operational amplifier U2 directly to a stable and clean 12V power supply establishes a defined and stable voltage reference for the entire relaxation oscillator circuit, ensuring the oscillation waveform parameters.

[0063] In this embodiment, the first-order RC resistor R12 and the first-order capacitor C3 form a first-order RC circuit. In practical applications, the resistor R12 is 46kΩ and the capacitor C3 is 0.1uF. The total response of the first-order RC circuit is analyzed, and the time constant of the first-order circuit is as follows: τ=R12 C3 The first hysteresis resistor R13, the second hysteresis resistor R14, and the second operational amplifier U2 form a hysteresis circuit. The operational amplifier is not connected to a negative feedback network, so it operates in an open-loop state, with the voltage gain approaching infinity and the linear operating region being negligible. In practical applications, resistors R13 and R14 are both taken as 1MΩ. Analyze the positive input voltage of the circuit: Depending on the circuit configuration, positive feedback will ensure that the output is driven to one of two stable states, so that the operational amplifier output is initially driven to a high level Vcc, at which point the upper threshold voltage V can be obtained. high :

[0064] The operational amplifier output is low (Gnd), and the lower threshold voltage V... low :

[0065] like Fig. 3 As shown, the voltage of the first-order capacitor C3 continuously charges and discharges at the upper and lower threshold voltages. To accurately calculate the circuit frequency based on the components, the charging and discharging equations of an RC circuit are used.

[0066] The general form of the charging equation is:

[0067] Solving for t in this equation yields:

[0068] The general form of the discharge equation is:

[0069] Solving for t in this equation yields:

[0070] Now, if we consider the time from Vlow charging to Vhigh, and simultaneously the time from Vhigh discharging to Vlow, we will obtain the output cycle: T = t1 + t2 = 4.9565 ms Therefore, the square wave frequency f = 1 / T = 1 / 4.9565 ≈ 200Hz.

[0071] A method for protecting the load of a power supply module for medical devices includes the following steps: S1: Real-time sampling and filtering of the output DC port voltage of the power supply module to obtain a voltage feedback signal; S2: Compare the voltage feedback signal with a reference voltage. When the voltage feedback signal exceeds the upper threshold voltage set by the reference voltage, an overvoltage trigger signal is generated. S3: Amplify the overvoltage trigger signal to generate a strong drive signal; S4: A power switching device is turned on by using a strong drive signal, so that an absorption resistor is connected between the output DC port and ground, forming a low-impedance energy discharge path to absorb voltage spikes or reverse electromotive force. S5: When the voltage feedback signal drops below the lower threshold voltage set by the reference voltage, the overvoltage trigger signal and the strong drive signal are canceled, the power switching device is turned off, and the absorption resistor is disconnected from the circuit.

[0072] This method constructs a closed-loop active energy management system. S1 continuously monitors the health status of the power supply port in real time; S2 intelligently judges anomalies based on precise thresholds; S3 and S4 quickly execute to actively connect the discharge path to consume harmful energy; and S5 automatically recovers and exits the protection state when the conditions are met. The function of this closed-loop system is to transform uncontrollable and destructive overvoltage events into a controllable process of detection-control-consumption, thereby ensuring the voltage cleanliness of the power supply port.

[0073] This method, based on solid-state electronic devices such as operational amplifiers and MOSFEs, allows the entire closed-loop response time to be controlled within a few microseconds. This means that it can effectively clamp and absorb voltage spikes before they reach their peak value and cause damage, achieving true instantaneous protection and significantly improving the protection effect.

[0074] This method has no moving mechanical parts; its core components are semiconductors and resistors / capacitors. As long as it operates within the design parameters, its theoretical lifespan is virtually unlimited, achieving maintenance-free protection circuitry with a lifespan matching that of the equipment, significantly improving the overall MTBF of medical devices.

[0075] This method, through the ingenious application of power MOSFETs, inherently possesses bidirectional protection capabilities. The control circuit actively turns on the MOSFET, dissipating through the absorption resistor. The body diode of the MOSFET or an externally parallel fast recovery diode automatically and without delay conducts, forming a discharge circuit.

[0076] This method, based on a high-precision reference voltage source and comparator, ensures highly accurate, stable, and predictable protection start-up and recovery points. This not only guarantees the reliability of the protection but also allows for the customization of the most suitable protection threshold for loads with different sensitivity levels.

[0077] Furthermore, in step S2, a hysteresis comparison is formed by introducing positive feedback, with the upper threshold voltage higher than the reference voltage and the lower threshold voltage lower than the reference voltage, in order to prevent output jitter caused by noise interference.

[0078] This invention establishes clear action and release boundaries. The method splits a single comparison threshold reference voltage Vref, such as 3V, into two distinct thresholds: a higher upper action threshold Vhigh, such as 3.1V, and a lower release threshold Vlow, such as 2.9V. This prevents harmful oscillations and thermal damage to power devices. The existence of a hysteresis window forces voltage changes to cross a finite, non-zero voltage difference to trigger a state change. This ensures deterministic and predictable protection behavior.

[0079] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A load protection circuit for a power supply module of a medical device, characterized in that, It includes an energy absorption circuit and a driving sub-circuit; one side of the energy absorption circuit is connected to the output DC port, and the other side of the energy absorption circuit is connected to the input terminal of the medical device; the driving sub-circuit is electrically connected to the energy absorption circuit. The energy absorption main circuit includes a voltage sampling unit, a comparison unit, a drive unit, and a power switching unit; the voltage sampling unit is connected to the output DC port and is used to output a sampling signal that is proportional to the DC output voltage; The first input terminal of the comparator unit is connected to the output terminal of the voltage sampling unit, and the second input terminal of the comparator unit is connected to a reference voltage source for comparing the sampled signal with the reference voltage and outputting a control signal; the input terminal of the drive unit is connected to the output terminal of the comparator unit; the control terminal of the power switch unit is connected to the output terminal of the drive unit, the first power terminal of the power switch unit is connected to the output DC port through an absorption resistor, and the second power terminal of the power switch unit is grounded. The driving sub-circuit includes a relaxation oscillator for generating a square wave signal at a fixed frequency; the output of the relaxation oscillator is connected to the control terminal of the driving unit in the energy absorption main circuit.

2. The load protection circuit for the medical device power supply module according to claim 1, characterized in that, The energy absorption circuit includes a first sampling resistor R1, a second sampling resistor R2, a first current-limiting resistor R3, a second current-limiting resistor R4, a first filter capacitor C1, a Zener diode D1, a first operational amplifier U1, a third current-limiting resistor R7, a push-pull circuit Q1, a MOSFET Q2, a fourth current-limiting resistor R8, a fifth current-limiting resistor R9, a second filter resistor R10, a diode D2, and an absorption resistor R11. The positive terminal of the output DC port, the first sampling resistor R1, the second sampling resistor R2, and the negative terminal of the output DC port are connected in series. A first filter capacitor C1 is connected in parallel across the two ends of the second sampling resistor R2; A Zener diode D1 is connected in parallel across the two ends of the second sampling resistor R2, and the positive terminal of the Zener diode D1 is connected to the negative terminal of the output DC power port. The negative terminal of Zener diode D1 is electrically connected to the positive input terminal of the first operational amplifier U1 through the first current-limiting resistor R3; One end of the second current-limiting resistor R4 is connected to a 3V reference source, and the other end of the second current-limiting resistor R4 is electrically connected to the negative input terminal of the first amplifier U1. One end of the third current-limiting resistor R7 is connected to the output of the operational amplifier U1, and the other end of the third current-limiting resistor R7 is connected to the input of the push-pull circuit Q1. The output terminal of the push-pull circuit Q1 is connected to the negative terminal of diode D2, the positive terminal of diode D2 is connected to one end of the fifth current-limiting resistor R9, and the other end of the fifth current-limiting resistor R9 is connected to the gate of MOSFET Q2. A fourth current-limiting resistor R8 is connected in parallel across the two ends of diode D2; The gate of MOSFET Q2 is connected to one end of the second filter resistor R10, and the other end of the second filter resistor R10 is grounded. The source of MOSFET Q2 is grounded, and the drain of MOSFET Q2 is connected to the input terminal of the medical device through the energy absorption resistor R11.

3. The load protection circuit for the medical device power supply module according to claim 2, characterized in that, The positive input terminal of the first operational amplifier U1 is electrically connected to one end of the gain feedback resistor R6, and the other end of the gain feedback resistor R6 is electrically connected to the output terminal of the first operational amplifier U1.

4. The load protection circuit for the medical device power supply module according to claim 3, characterized in that, The negative input terminal of the operational amplifier U1 is electrically connected to one end of the second filter capacitor C2, and the other end of the second filter capacitor C2 is grounded; the first filter resistor R5 is connected in parallel with the second filter capacitor C2.

5. The load protection circuit for the medical device power supply module according to claim 1, characterized in that, The driving sub-circuit includes a second operational amplifier U2, the negative input terminal of the second operational amplifier U2 is connected to one end of a first-order RC capacitor C3, and the other end of the first-order RC capacitor C3 is grounded. The positive input terminal of the second operational amplifier U2 is connected to one end of the first hysteresis resistor R13, and the other end of the first hysteresis resistor R13 is connected to a 12V power supply. The output of the second operational amplifier U2 is connected to one end of the sixth current-limiting resistor R16, and the other end of the sixth current-limiting resistor R16 outputs a square wave signal to the input of the push-pull circuit Q1 section of the energy absorption circuit.

6. The load protection circuit for the medical device power supply module according to claim 5, characterized in that, The positive input terminal of the second operational amplifier U2 is connected to one end of the second hysteresis resistor R14, and the other end of the second hysteresis resistor R14 is connected to the output terminal of the second operational amplifier U2. The positive input terminal of the second operational amplifier U2 is connected to one end of the third filter resistor R15, and the other end of the third filter resistor R15 is grounded.

7. The load protection circuit for the medical device power supply module according to claim 6, characterized in that, The negative input terminal of the second operational amplifier U2 is connected to one end of the first-order RC resistor R12, and the other end of the first-order RC resistor R12 is connected to the output terminal of the second operational amplifier U2.

8. The load protection circuit for the medical device power supply module according to claim 7, characterized in that, The power supply terminal of the second operational amplifier U2 is connected to a 12V power supply, and the ground terminal of the second operational amplifier U2 is grounded.

9. The protection method for the load protection circuit of the medical device power supply module as described in any one of claims 1-8, characterized in that, Includes the following steps: S1: Real-time sampling and filtering of the output DC port voltage of the power supply module to obtain a voltage feedback signal; S2: Compare the voltage feedback signal with a reference voltage. When the voltage feedback signal exceeds the upper threshold voltage set by the reference voltage, an overvoltage trigger signal is generated. S3: Amplify the overvoltage trigger signal to generate a strong drive signal; S4: A power switching device is turned on by using a strong drive signal, so that an absorption resistor is connected between the output DC port and ground, forming a low-impedance energy discharge path to absorb voltage spikes or reverse electromotive force. S5: When the voltage feedback signal drops below the lower threshold voltage set by the reference voltage, the overvoltage trigger signal and the strong drive signal are canceled, the power switching device is turned off, and the absorption resistor is disconnected from the circuit.

10. The protection method for the load protection circuit of the medical device power supply module according to claim 9, characterized in that, In step S2, a hysteresis comparison is formed by introducing positive feedback, with the upper threshold voltage being higher than the reference voltage and the lower threshold voltage being lower than the reference voltage.

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