Comparator-based load short circuit protection circuit

Abstract

The utility model relates to comparator circuit protection technical field discloses the load short circuit protection circuit based on comparator, include: current sampling resistance RS2, first end connects public end, second end ground connection, comparator U13 the opposite phase input end through resistance R106 and electric capacity C67 shunt network connection RS2's public end, the positive phase input end through resistance R107 connects TL431 reference source U14's cathode, TL431 reference source U14's reference pole passes through resistance R111 ground connection, drive chip EG27324. In the utility model, through comparator U13 the direct triggering of B light coupling U10 action, force MCU to shut off drive chip EG27324, and after receiving hardware fault signal, through software filtering algorithm secondary verification load state, simultaneously, three -level hardware filter and software dynamic threshold value compensation, realize the cooperative protection mechanism of hardware fast response and software accurate fault tolerance.

Description

Technical Field

[0001] This utility model relates to the field of comparator circuit protection technology, and in particular to a load short-circuit protection circuit based on a comparator. Background Technology

[0002] Comparators, as commonly used voltage comparators, compare input signals with reference voltages and output high or low levels. They are widely used in overcurrent and overvoltage protection circuits. Load short-circuit protection circuits, as a key component of power management systems, quickly cut off power supply when a short-circuit fault occurs at the load, preventing equipment damage and safety accidents. Traditional load short-circuit protection schemes mainly utilize operational amplifiers to collect load current; upon abnormal current readings, software is used to shut down the load MOSFET, thereby cutting off the load.

[0003] However, in current technology, the operational amplifier collects the load current, and when the current is abnormal, the load MOSFET is turned off by software, thereby turning off the load. This has problems such as slow response speed, high false alarm rate and weak anti-electromagnetic interference capability. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a comparator-based load short-circuit protection circuit, which aims to improve the problems of slow response speed, high false alarm rate and weak anti-electromagnetic interference capability.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A comparator-based load short-circuit protection circuit includes:

[0007] The current sampling resistor RS2 has its first terminal connected to the common terminal and its second terminal grounded.

[0008] Comparator U13-B has its inverting input connected to the common terminal of RS2 via a parallel network of resistor R106 and capacitor C67, and its non-inverting input connected to the cathode of TL431 reference source U14 via resistor R107.

[0009] The reference terminal of the TL431 reference source U14 is grounded through resistor R111, and the anode is connected to the B2+ power supply.

[0010] Optocoupler U10 has its light-emitting diode anode connected to the output terminal of comparator U13-B through resistor R103, and its cathode grounded;

[0011] The phototransistor collector of optocoupler U10 is connected to the power supply through pull-up resistor R100, and the emitter is connected to the LOAD-SHORT detection terminal of MCU through parallel capacitors C103 and C104.

[0012] The driver chip EG27324 has its enable pin connected to the MCU control signal, and its output pin drives the gate of MOSFET Q16 through the gate resistor R90.

[0013] The above technical solution involves real-time monitoring of the load current via current sampling resistor RS2, comparing the current with the threshold voltage generated by comparator U13-B and the TL431 reference source. When the current exceeds the limit, optocoupler U10 is triggered to conduct, and the MCU immediately shuts down the driver chip EG27324 to cut off the circuit of MOSFET Q16. Combined with the three-stage filtering design, interference is effectively suppressed, achieving fast and reliable short-circuit protection.

[0014] Preferably, a filter capacitor C71 is provided between the cathode of the TL431 reference source U14 and the resistor R107, and is connected to the B2+ power supply.

[0015] The above technical solution involves adding a filter capacitor C71 between the cathode of the TL431 reference source and the voltage divider resistor, which is directly connected to the B2+ power supply. This effectively suppresses power supply fluctuation interference, ensures stable reference voltage, and improves the anti-interference capability and response accuracy of the protection circuit.

[0016] Preferably, the non-inverting input terminal of the comparator U13-B is provided with a voltage divider circuit, which is composed of R107 and the internal reference of U14.

[0017] The above technical solution utilizes a TL431 reference source and a voltage divider resistor network to construct a precise threshold voltage generation circuit, providing a stable reference voltage for the comparator and ensuring the accuracy of load current detection. When the sampled voltage exceeds the set threshold, the comparator quickly responds and triggers protection action, achieving reliable short-circuit protection.

[0018] Preferably, in the LED circuit of the optocoupler U10, a protective resistor R105 is connected in series between the anode resistor R103 and the output terminal of the comparator U13-B.

[0019] The above technical solution involves adding a protective resistor R105 to the optocoupler drive circuit, which effectively limits the drive current and suppresses voltage spikes. This protects the comparator output stage and extends the service life of the optocoupler. At the same time, the RC filtering characteristics eliminate switching noise interference, ensuring the reliability of signal transmission.

[0020] Preferably, the power supply terminal of the driver chip EG27324 is connected to the B2+ power supply through capacitor C132, and reverse voltage protection is provided through diode D5.

[0021] The above technical solution provides stable power filtering and reverse voltage protection for the driver chip through capacitor C132 and diode D5, effectively suppressing power noise interference and preventing circuit damage from reverse polarity connection, ensuring stable and reliable drive signal, and improving the overall reliability of the system.

[0022] Preferably, the source of the MOS transistor Q16 is directly connected to the positive terminal of the B2+ power supply, the drain is output to an external device through the load connection terminal, and a capacitor C66 is connected in parallel between the gate and the source.

[0023] The above technical solution involves directly connecting the power supply and load through the MOSFET Q16 and connecting the gate and source capacitor C66 in parallel. This effectively absorbs voltage spikes and oscillations during the switching process, prevents false triggering and gate breakdown, and ensures the stable and reliable operation of the power switch.

[0024] Preferably, a bleeder resistor R98 is provided between the common terminal and the B2+ power supply to quickly release residual charge when the system loses power.

[0025] The above technical solution establishes a discharge circuit between the common terminal and the power supply through the bleed resistor R98, which quickly releases the residual charge in the circuit when the system is powered off, effectively preventing malfunctions and ensuring operational safety.

[0026] Preferably, the circuit is provided with a three-stage filtering protection structure, including:

[0027] First stage: C71 filter of TL431 reference source;

[0028] Second stage: C67 filter at the comparator input;

[0029] Third stage: C103 and C104 filtering at the output of the optocoupler.

[0030] The above technical solution employs a three-stage filtering structure, with filtering networks set at the reference source, comparator input, and optocoupler output to form a multi-stage noise suppression barrier. This effectively eliminates power supply interference, sampling noise, and switching interference, ensuring the purity and reliability of the protection signal transmission and improving overall anti-interference capability.

[0031] This utility model has the following beneficial effects:

[0032] 1. In this utility model, the comparator U13-B directly triggers the optocoupler U10 to force the MCU to shut down the driver chip EG27324. After receiving the hardware fault signal, the MCU verifies the load status a second time through the software filtering algorithm to avoid false triggering. At the same time, the three-level hardware filtering and the software dynamic threshold compensation work together to realize a collaborative protection mechanism of fast hardware response and precise software fault tolerance.

[0033] 2. In this utility model, a hardware threshold generation circuit is constructed by using a TL431 reference source and a voltage divider resistor network. The reference voltage is adaptively adjusted by directly connecting to the B2+ power supply, which effectively maintains the stability of the threshold. In addition, the filter capacitor suppresses interference, ensuring detection accuracy and improving circuit reliability. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the comparator-based load short-circuit protection circuit proposed in this utility model. Detailed Implementation

[0035] The technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0036] Reference Figure 1 One embodiment of this utility model provides a comparator-based load short-circuit protection circuit, comprising:

[0037] The current sampling resistor RS2 has its first terminal connected to the common terminal and its second terminal grounded.

[0038] Comparator U13-B has its inverting input connected to the common terminal of RS2 via a parallel network of resistor R106 and capacitor C67, and its non-inverting input connected to the cathode of TL431 reference source U14 via resistor R107.

[0039] The reference terminal of the TL431 reference source U14 is grounded through resistor R111, and the anode is connected to the B2+ power supply.

[0040] Optocoupler U10 has its light-emitting diode anode connected to the output terminal of comparator U13-B through resistor R103, and its cathode grounded;

[0041] The phototransistor collector of optocoupler U10 is connected to the power supply through pull-up resistor R100, and the emitter is connected to the LOAD-SHORT detection terminal of MCU through parallel capacitors C103 and C104.

[0042] Specifically, the current sampling resistor RS2 (3mΩ / 3W / 1%) is connected in series in the load circuit. Its common terminal is connected to the inverting input (pin 6) of comparator U13-B (LM293DR) through a filter network consisting of resistor R106 and capacitor C67 in parallel. The non-inverting input (pin 5) receives the threshold voltage generated by the TL431 reference source U14 through resistor R107. When the load current exceeds the limit, the comparator outputs a low level to drive the LED of optocoupler U10 to conduct. The collector of the phototransistor pulls the LOAD-SHORT signal high through the pull-up resistor R100 and transmits it to... The MCU trigger driver chip EG27324's enable pin (LOAD-EN) is directly connected to the MCU's control signal. The output pin drives the gate of MOSFET Q16 through a 4.7kΩ gate resistor R90. The power supply pin (VCC) is connected to the B2+ power supply and decoupled through capacitor C132. EG27324 dynamically adjusts the gate voltage of Q16 according to the MCU signal to achieve fast on / off control of the load circuit. The circuit also uses three-stage filtering (C67, C71, C103 / C104) to suppress interference, optocouplers to isolate high and low voltage circuits, and a TL431 reference combined with a voltage divider network to achieve ±3A detection accuracy.

[0043] A filter capacitor C71 is located between the cathode of the TL431 reference source U14 and the resistor R107, and is connected to the B2+ power supply.

[0044] Specifically, the cathode (pin 3) of the TL431 reference source U14 is connected to the non-inverting input (pin 5) of the comparator U13-B via resistor R107, with a filter capacitor C71 connected in parallel along this path. The cathode is also directly connected to the B2+ power supply. This structure generates a stable threshold voltage through the TL431's internal reference and voltage divider network.

[0045] A voltage divider circuit is set at the non-inverting input of comparator U13-B, which is composed of R107 and the internal reference of U14;

[0046] Specifically, the non-inverting input (pin 5) of comparator U13-B is connected to the cathode (pin 3) of TL431 reference source U14 through resistor R107 (12kΩ). Combined with the internal reference voltage of U14 and the voltage divider resistor R111, a threshold generation circuit is formed. This voltage is filtered by the filter capacitor C71 connected in parallel across R107 to remove high-frequency noise introduced by the B2+ power supply, ensuring threshold stability. When the load current exceeds the limit, the RS2 sampling voltage exceeds 0.357V, triggering the comparator to flip and sending a fault signal to the MCU through optocoupler U10. The cathode of TL431 is directly connected to the B2+ power supply and is limited by its voltage clamp. Combined with the voltage divider of resistors R107 / R111 and the filter of C71, high-precision, anti-interference, and fast hardware protection is achieved.

[0047] In the LED circuit of optocoupler U10, a protective resistor R105 is connected in series between the anode resistor R103 and the output terminal of comparator U13-B.

[0048] Specifically, the protection resistor R105 is connected in series between the output terminal (pin 7) of comparator U13-B and the anode resistor R103 of the optocoupler U10 LED. By limiting the peak output current of the comparator and reducing the driving voltage through voltage division, it suppresses the voltage spike and high-frequency oscillation at the moment of optocoupler conduction. At the same time, it forms a low-pass filter with the optocoupler junction capacitance at the cutoff frequency to filter out switching noise, ensure the stable operating current of the LED, prevent overcurrent damage to the comparator output stage and optocoupler components, extend service life and improve anti-interference capability.

[0049] The power supply terminal of the driver chip EG27324 is connected to the B2+ power supply through capacitor C132, and reverse voltage protection is provided through diode D5.

[0050] Specifically, the power supply terminal (VCC) of the driver chip EG27324 is connected to the B2+ power supply through a 1μF / 100V capacitor C132. The energy storage characteristics of the capacitor are used to filter out high-frequency noise from the power line. At the same time, the unidirectional conduction characteristics of the diode D5 prevent reverse connection of the power supply, ensuring that the EG27324 operates stably under power fluctuations. The collaborative design of C132 and D5 can suppress power ripple to within ±0.5V. Combined with the internal overvoltage protection circuit of the EG27324, the power supply terminal has anti-interference capability.

[0051] The source of MOSFET Q16 is directly connected to the positive terminal of power supply B2+, and the drain is output to an external device through the load connection terminal. A capacitor C66 is connected in parallel between the gate and the source.

[0052] Specifically, the source of MOSFET Q16 is directly connected to the positive terminal of the B2+ power supply, and the drain is output to the external device through the load connection terminal (LOAD). A capacitor C66 is connected in parallel between the gate and the source to form a gate-source voltage buffer circuit. C66 absorbs the high-frequency oscillation during the switching process, suppresses the transient gate voltage, and prevents Q16 from being mis-connected or broken down due to parasitic parameters.

[0053] A bleed resistor R98 is provided between the common terminal and the B2+ power supply to quickly release residual charge when the system loses power.

[0054] Specifically, the discharge resistor R98 is connected between the common terminal and the positive terminal of the B2+ power supply. When the system is powered off or the load is disconnected, R98 forms a low-impedance discharge circuit to quickly discharge the residual charge of the energy storage element to ground, avoiding false triggering of the gate of the MOSFET Q16 or false alarm of the MCU detection terminal (LOAD-SHORT) due to residual voltage, thus ensuring the safety and reliability of the circuit.

[0055] The circuit is equipped with a three-stage filtering and protection structure, including:

[0056] First stage: C71 filter of TL431 reference source;

[0057] Second stage: C67 filter at the comparator input;

[0058] Third stage: C103 and C104 filtering at the output of the optocoupler;

[0059] Specifically, in the three-stage filtering protection structure of the circuit, the first stage, C71 connected in parallel with the cathode of the TL431 reference source, filters out high-frequency noise (such as ignition pulse and motor EMI interference) from the B2+ power supply coupling, ensuring that the reference voltage fluctuation is less than ±10mV; the second stage, C67 and R106 at the inverting input of the comparator form an RC low-pass filter to suppress switching noise (such as transient interference from the switching of the MOSFET Q16) in the current sampling signal; the third stage, C103 / C104 connected in parallel at the output of the optocoupler, forms a wideband filtering network to eliminate ringing and radiation interference introduced during the optocoupler switching process, ensuring that the signal spike at the MCU detection end (LOAD-SHORT) is ≤50mV, thereby ensuring the accuracy and reliability of the short-circuit protection action.

[0060] Working Principle: The load current is detected in real time through the current sampling resistor RS2 and converted into a voltage signal, which is then input to the inverting input of comparator U13-B. At the same time, the TL431 reference source U14 generates a 0.357V threshold voltage through the voltage divider of resistors R107 and R111, which is input to the non-inverting input of the comparator. When the load is short-circuited, causing the voltage across RS2 to exceed the threshold, comparator U13-B outputs a low level to drive optocoupler U10 to conduct. The optocoupler phototransistor pulls the LOAD-SHORT signal high to 3.3V and transmits it to the MCU. The MCU immediately turns off the enable signal of the driver chip EG27324, causing EG27324 to cut off the gate drive voltage of MOSFET Q16. Q16 turns off the load circuit within 10μs. The three-stage filtering structure works together to suppress interference, the discharge resistor R98 quickly releases the residual charge of the system, and the protection resistor R105 limits the peak value of the optocoupler drive current. With the adaptive reference voltage of TL431 and the reverse voltage protection of the driver chip, a highly reliable short-circuit protection with fast hardware response and dual software confirmation is achieved.

[0061] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A comparator-based load short-circuit protection circuit, characterized in that, include: The current sampling resistor RS2 has its first terminal connected to the common terminal and its second terminal grounded. Comparator U13-B has its inverting input connected to the common terminal of RS2 via a parallel network of resistor R106 and capacitor C67, and its non-inverting input connected to the cathode of TL431 reference source U14 via resistor R107. The reference terminal of the TL431 reference source U14 is grounded through resistor R111, and the anode is connected to the B2+ power supply. Optocoupler U10 has its LED anode connected to the output of comparator U13-B via resistor R103, and its cathode grounded. The phototransistor collector of optocoupler U10 is connected to the power supply through pull-up resistor R100, and the emitter is connected to the LOAD-SHORT detection terminal of MCU through parallel capacitors C103 and C104. The driver chip EG27324 has its enable pin connected to the MCU control signal, and its output pin drives the gate of MOSFET Q16 through the gate resistor R90.

2. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: A filter capacitor C71 is provided between the cathode of the TL431 reference source U14 and the resistor R107, and is connected to the B2+ power supply.

3. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: The non-inverting input of the comparator U13-B is equipped with a voltage divider circuit, which is composed of R107 and the internal reference of U14.

4. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: In the LED circuit of the optocoupler U10, a protective resistor R105 is connected in series between the anode resistor R103 and the output terminal of the comparator U13-B.

5. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: The power supply terminal of the driver chip EG27324 is connected to the B2+ power supply through capacitor C132, and reverse voltage protection is provided through diode D5.

6. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: The source of the MOSFET Q16 is directly connected to the positive terminal of the B2+ power supply, and the drain is output to an external device through the load connection terminal. A capacitor C66 is connected in parallel between the gate and the source.

7. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: A bleed resistor R98 is provided between the common terminal and the B2+ power supply to quickly release residual charge when the system loses power.

8. The comparator-based load short-circuit protection circuit according to claim 1, characterized in that: The circuit is equipped with a three-stage filtering protection structure, including: First stage: C71 filter of TL431 reference source; Second stage: C67 filter at the comparator input; Third stage: C103 and C104 filtering at the output of the optocoupler.

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