A modular intrinsically safe protection circuit

Abstract

The application relates to the technical field of power supply protection, in particular to a modular intrinsic safety protection circuit. The intrinsic safety protection circuit comprises at least one intrinsic safety protection unit, each intrinsic safety protection unit comprising: a protection control chip for monitoring input voltage and current signals and outputting on-off control signals; a power switch tube connected to the output end of the protection control chip and used for performing switching actions according to the on-off control signals; an adjustable voltage division network connected to an input power supply end and used for setting the under-voltage protection threshold or the over-voltage protection threshold of the modular intrinsic safety protection circuit by adjusting resistance values; and a replaceable current sampling resistor connected in series in a power supply loop and used for setting the over-current protection threshold of the modular intrinsic safety protection circuit. By replacing the resistors of the adjustable voltage division network and / or the current sampling resistor, the modular intrinsic safety protection circuit can be adapted to intrinsic safety power supplies of different voltage / current levels.

Description

Technical Field

[0001] This application relates to the field of power protection technology, and in particular to a modular intrinsically safe protection circuit. Background Technology

[0002] Intrinsically safe protection circuits are the core component of intrinsically safe circuits. They are mainly used in industrial fields such as coal mines and chemical plants where there are flammable and explosive environments. Their core function is to limit the energy (voltage, current, power) in the circuit to ensure that even if a short circuit or open circuit occurs, the released energy will not ignite the surrounding explosive gas mixture, thereby achieving explosion-proof safety protection.

[0003] Traditional intrinsically safe protection circuits can only be adapted to intrinsically safe power supplies of a single voltage / current level.

[0004] However, when the application scenario requires the replacement of intrinsically safe power supplies with different voltages or currents, it is necessary to redesign the circuit topology, replace the core chip, or make large-scale adjustments to peripheral components, resulting in high development costs and long debugging cycles, making it difficult to meet the needs of reuse in multiple scenarios. Therefore, improvements are urgently needed. Utility Model Content

[0005] Therefore, it is necessary to provide a modular intrinsically safe protection circuit suitable for diverse scenarios to address the aforementioned technical problems.

[0006] A modular intrinsically safe protection circuit includes at least one intrinsically safe protection unit, each intrinsically safe protection unit comprising:

[0007] The protection control chip monitors the input voltage and current signals and outputs on / off control signals.

[0008] The power switching transistor is connected to the output terminal of the protection control chip and is used to perform switching actions according to the on / off control signal.

[0009] An adjustable voltage divider network is connected to the input power supply. By adjusting the resistance value, the undervoltage protection threshold or overvoltage protection threshold of the modular intrinsically safe protection circuit can be set.

[0010] A replaceable current sampling resistor is connected in series in the power supply circuit to set the overcurrent protection threshold of the modular intrinsically safe protection circuit.

[0011] By replacing the resistors of the adjustable voltage divider network and / or the current sampling resistor, the modular intrinsically safe protection circuit can be adapted to intrinsically safe power supplies of different voltage / current levels.

[0012] In one embodiment, each intrinsically safe protection unit includes two intrinsically safe protection units and a second intrinsically safe protection unit connected in series, wherein:

[0013] The output terminal of the first intrinsically safe protection unit is connected to the input terminal of the second intrinsically safe protection unit;

[0014] The output of the second intrinsically safe protection unit serves as the output port of the modular intrinsically safe protection circuit.

[0015] In one embodiment, the adjustable voltage divider network includes:

[0016] The undervoltage detection branch includes at least two series-connected undervoltage protection resistors, and the voltage divider node between the two series-connected undervoltage protection resistors is connected to the undervoltage detection pin of the protection control chip.

[0017] The overvoltage detection branch includes at least two series-connected overvoltage protection resistors, and the voltage divider node between the two series-connected overvoltage protection resistors is connected to the overvoltage detection pin of the protection control chip.

[0018] In one embodiment, the resistance value of the undervoltage protection resistor can be replaced to adjust the undervoltage protection threshold.

[0019] The resistance value of the overvoltage protection resistor is replaceable, which is used to adjust the overvoltage protection threshold.

[0020] In one embodiment, the protection control chip is configured to turn off the power switch when one of the following shutdown conditions is met; the shutdown conditions include:

[0021] When the voltage at the undervoltage detection pin is less than the undervoltage protection threshold, or

[0022] The voltage at the overvoltage detection pin is greater than the overvoltage protection threshold, or

[0023] The voltage across the current sampling resistor is greater than or equal to the overcurrent voltage threshold.

[0024] In one embodiment, the power switch is an N-channel MOSFET;

[0025] The drain of the power switching transistor is connected to the power input terminal of the intrinsically safe protection unit through a current sampling resistor;

[0026] The source of the power switch is connected to the output node of the intrinsically safe protection unit;

[0027] The output node is connected to the input terminal of the subsequent intrinsically safe protection unit or the output port of the modular intrinsically safe protection circuit.

[0028] In one embodiment, the protection control chip further includes:

[0029] The current sensing terminal is connected to both ends of the current sampling resistor;

[0030] The drive output is directly connected to the gate of the power switch transistor;

[0031] The current detection terminal is configured to detect the voltage across the current sampling resistor.

[0032] In one embodiment, the modular intrinsically safe protection circuit further includes:

[0033] The timed restart unit is connected to the timer pin of the protection control chip;

[0034] The timed restart unit includes a timed capacitor and a timed resistor connected in series, which are used for automatic recovery circuit after the fault is cleared.

[0035] In one embodiment, the modular intrinsically safe protection circuit further includes a status indication unit, comprising:

[0036] The positive terminal of the light-emitting diode is connected to the output terminal of the power switching transistor;

[0037] A current-limiting resistor is connected in series between the negative terminal of the LED and ground.

[0038] In one embodiment, the overvoltage protection resistor or undervoltage protection resistor is in a pluggable or solderable replaceable package, making the modular intrinsically safe protection circuit compatible with 9V, 12V, and 24V input power supplies.

[0039] The current sampling resistor is available in terminal connection or pad package form, making the modular intrinsically safe protection circuit compatible with 0.5A-5A loads.

[0040] The aforementioned modular intrinsically safe protection circuit features an adjustable voltage divider network composed of replaceable series resistors. By changing the resistors to adjust the voltage division ratio, undervoltage / overvoltage protection thresholds for different voltage levels can be flexibly set without redesigning the voltage detection circuit, enabling a single circuit to adapt to multiple voltage levels. The current sampling resistor is connected in series in the main circuit, and its resistance value directly determines the overcurrent protection threshold. By replacing the sampling resistor with different values, it can adapt to loads with different current levels, such as 0.5A to 5A, without adjusting the core structure of the current detection circuit. Each protection unit is a standardized module, supporting independent operation of a single unit or series expansion of multiple units. This meets the basic protection needs of simple scenarios and can also improve the protection reliability of complex scenarios through cascading, avoiding the need to redesign the entire circuit due to changes in scenarios. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a circuit diagram of a modular intrinsically safe protection circuit in one embodiment;

[0043] Figure 2 This is a schematic diagram illustrating the connection relationship between the first intrinsically safe protection unit and the second intrinsically safe protection unit in one embodiment;

[0044] Figure 3 This is a circuit diagram of the first intrinsically safe protection unit and the second intrinsically safe protection unit in one embodiment;

[0045] Explanation of reference numerals in the attached figures:

[0046] 11. Protection control chip; 12. Power switching transistor;

[0047] 13. Adjustable voltage divider network; 14. Current sampling resistor. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0049] In one exemplary embodiment, a modular intrinsically safe protection circuit is provided, such as... Figure 1 As shown, it includes at least one intrinsically safe protection unit, and each intrinsically safe protection unit includes:

[0050] Protection control chip 11 monitors input voltage and current signals and outputs on / off control signals;

[0051] The power switching transistor 12 is connected to the output terminal of the protection control chip and is used to perform switching actions according to the on / off control signal.

[0052] The adjustable voltage divider network 13 is connected to the input power supply terminal. The undervoltage protection threshold or overvoltage protection threshold of the modular intrinsically safe protection circuit can be set by adjusting the resistance value.

[0053] A replaceable current sampling resistor 14 is connected in series in the power supply circuit to set the overcurrent protection threshold of the modular intrinsically safe protection circuit.

[0054] By replacing the resistors of the adjustable voltage divider network and / or the current sampling resistor, the modular intrinsically safe protection circuit can be adapted to intrinsically safe power supplies of different voltage / current levels.

[0055] Understandably, each intrinsically safe protection unit is the basic functional carrier of the circuit, independently performing overvoltage, undervoltage, and overcurrent monitoring and protection of the input power supply. Its core components are as follows:

[0056] The protection control chip 11, as the core controller of the intrinsically safe protection unit, collects the input voltage signal (undervoltage / overvoltage) and the loop current signal (overcurrent) in real time. After comparing them with preset thresholds, it outputs high / low level on / off control signals to realize the switching control of the power switching transistor. At the same time, it integrates necessary drive circuits (such as a charge pump, mentioned in the background technology) to simplify the peripheral structure.

[0057] The protection control chip 11 can be an integrated protection chip, such as the LM5069 series or a dedicated chip with the same function (supporting wide voltage input, built-in voltage comparator and current detection module). This type of chip has built-in charge pump technology and can directly drive NMOS transistors without the need for additional drive circuitry, simplifying the circuit structure.

[0058] The power switching transistor 12 acts as a "switch" in the power supply circuit. It receives the on / off signal from the protection control chip. When it is on, it supplies power to the subsequent circuit. When it is off, it cuts off the circuit to achieve fault protection.

[0059] The power switch 12 can be an N-channel MOSFET (such as the NCE6080K), featuring low on-resistance and high voltage withstand characteristics. Its gate is connected to the output of the protection control chip, its drain is connected to the input power supply after a current sampling resistor in series, and its source is connected to the subsequent circuit or the output. It is driven by the chip's built-in charge pump to ensure reliable conduction over a wide voltage range.

[0060] The adjustable voltage divider network 13 converts the input power supply voltage into a signal that the protection control chip can recognize through resistor voltage division. This signal is used to set the undervoltage protection threshold (triggered when the input voltage is too low) and the overvoltage protection threshold (triggered when the input voltage is too high).

[0061] The adjustable voltage divider network 13 may include independent undervoltage detection branches and independent overvoltage detection branches:

[0062] Undervoltage detection branch: Two replaceable precision resistors (e.g., 10kΩ~100kΩ metal film resistors) are connected in series. One end is connected to the input power supply, and the other end is grounded. The voltage divider node is connected to the undervoltage detection pin (UVLO) of the protection control chip. The voltage division ratio can be changed by changing the resistors. For example, when adapting to a 9V power supply, select R1=20kΩ and R2=10kΩ (voltage division value = 9V×10kΩ / (20kΩ+10kΩ)=3V, which will work normally if it is higher than the chip's built-in threshold of 2.5V).

[0063] Overvoltage detection branch: Two replaceable precision resistors (e.g., 20kΩ~200kΩ) are connected in series. One end is connected to the input power supply, and the other end is grounded. The voltage divider node is connected to the overvoltage detection pin (OVP) of the protection control chip. Similarly, the overvoltage threshold is set by changing the resistors. For example, when adapting to a 24V power supply, select R3=100kΩ and R4=10kΩ (voltage divider value = 24V×10kΩ / (100kΩ+10kΩ)≈2.18V, which is lower than the chip's built-in threshold of 2.5V for normal operation).

[0064] The replaceable current sampling resistor 14 is connected in series in the main power supply circuit to convert the circuit current into a voltage signal (U=I×R) for the protection control chip to detect and set the overcurrent protection threshold (the protection is triggered when the current exceeds the threshold).

[0065] The replaceable current sampling resistor 14 is a high-precision, low-temperature-drift sampling resistor (e.g., 0.01Ω~1Ω, 1% accuracy), connected in series between the input power supply and the drain of the power switching transistor. The voltage across its terminals is directly input to the current detection terminal of the protection control chip. The overcurrent threshold is set by changing the resistor value: for example, when 300mA overcurrent protection is required, a 0.1Ω resistor is selected (300mA × 0.1Ω = 30mV, reaching the typical overcurrent trigger voltage of the chip); when a 500mA threshold is required, it is replaced with a 0.06Ω resistor (500mA × 0.06Ω = 30mV).

[0066] It is understood that the adjustable voltage divider network is the core module for the circuit to achieve multi-voltage adaptation. Through independent undervoltage detection branches and overvoltage detection branches, the lower limit (undervoltage) and upper limit (overvoltage) protection thresholds of the input voltage are set respectively. In an exemplary embodiment, the adjustable voltage divider network includes:

[0067] The undervoltage detection branch includes at least two series-connected undervoltage protection resistors, and the voltage divider node between the two series-connected undervoltage protection resistors is connected to the undervoltage detection pin of the protection control chip.

[0068] The overvoltage detection branch includes at least two series-connected overvoltage protection resistors, and the voltage divider node between the two series-connected overvoltage protection resistors is connected to the overvoltage detection pin of the protection control chip.

[0069] The resistance value of the undervoltage protection resistor can be replaced to adjust the undervoltage protection threshold; the resistance value of the overvoltage protection resistor can also be replaced to adjust the overvoltage protection threshold.

[0070] Furthermore, the overvoltage protection resistor or undervoltage protection resistor adopts a pluggable or solderable replacement package, making the modular intrinsically safe protection circuit compatible with 9V, 12V, and 24V input power supplies.

[0071] Furthermore, the current sampling resistor adopts terminal connection or pad packaging form, so that the modular intrinsically safe protection circuit can be adapted to 0.5A-5A load.

[0072] Understandably, the undervoltage detection branch is used to monitor whether the input power supply voltage is below the safe operating range. When the voltage is too low, an undervoltage signal is sent to the protection control chip through the voltage divider node, triggering protection actions (such as shutting down the power switch). The undervoltage detection branch consists of at least two undervoltage protection resistors connected in series. The series connection node (voltage divider node) of the two resistors is directly connected to the undervoltage detection pin (such as the UVLO pin) of the protection control chip. The undervoltage protection resistors use pluggable terminals (such as 2.54mm pitch pin headers) or solderable pads (such as 0805 / 1206 package SMD pads), supporting quick replacement of resistors with different values.

[0073] Understandably, the overvoltage detection branch is used to monitor whether the input power supply voltage exceeds the safe operating range. When the voltage is too high, an overvoltage signal is sent to the protection control chip through the voltage divider node, triggering the protection action. The overvoltage detection branch consists of at least two overvoltage protection resistors connected in series. The series connection node (voltage divider node) of the two resistors is directly connected to the overvoltage detection pin (such as the OVP pin) of the protection control chip. The overvoltage protection resistor and the undervoltage protection resistor use the same replaceable package (pluggable / solderable) to ensure consistent operation.

[0074] Understandably, by changing the resistance values ​​of the undervoltage protection resistor and the overvoltage protection resistor, the ratio of the voltage divider node voltage to the input voltage is adjusted, allowing the protection control chip to operate normally within the target voltage range (taking the chip's built-in 2.5V reference threshold as an example). For undervoltage protection, the voltage divider node voltage must be ≥2.5V (the chip determines the voltage is normal); for overvoltage protection, the voltage divider node voltage must be ≤2.5V (the chip determines the voltage is normal). Changing the resistance values ​​can satisfy the threshold settings for 9V / 12V / 24V input power supplies.

[0075] Understandably, the current sampling resistor is a core component for setting the overcurrent protection threshold. By monitoring the voltage across its terminals, it reflects the circuit current, enabling adaptation to different load currents. Connected in series in the main power supply circuit, the current sampling resistor converts the flowing current into a voltage signal (U=I×R). When the voltage exceeds the overcurrent threshold of the protection control chip (e.g., 30mV), overcurrent protection is triggered (shutting down the power switch). The current sampling resistor uses a high-precision, low-temperature drift resistor (e.g., 0.005Ω~0.1Ω, 1% accuracy), supporting load current detection from 0.5A to 5A. The current sampling resistor uses terminal connections (e.g., M3 screw terminals) or large-size pads (e.g., 2512 package SMD pads), facilitating the replacement of resistors with different values ​​according to load requirements.

[0076] It is understandable that by changing the resistance value of the current sampling resistor, different overcurrent protection thresholds can be set (taking the chip overcurrent trigger voltage of 30mV as an example).

[0077] In one exemplary embodiment, the protection control chip is configured to turn off the power switch when one of the following shutdown conditions is met; the shutdown conditions include:

[0078] When the voltage at the undervoltage detection pin is less than the undervoltage protection threshold, or

[0079] The voltage at the overvoltage detection pin is greater than the overvoltage protection threshold, or

[0080] The voltage across the current sampling resistor is greater than or equal to the overcurrent voltage threshold.

[0081] Understandably, the protection control chip, acting as the "brain" of the circuit, uses three independent monitoring channels (undervoltage, overvoltage, and overcurrent) to determine the circuit status in real time and trigger protection actions (shutting down the power switch) when an abnormality occurs.

[0082] Undervoltage protection: When the input voltage is lower than the set threshold, the output is cut off to prevent the downstream circuit from operating abnormally due to insufficient voltage.

[0083] When the voltage of the undervoltage detection pin (UVLO) is less than the undervoltage protection threshold (usually the chip's built-in 2.5V). Example: For a 9V power supply, the undervoltage detection branch uses R1=20kΩ and R2=10kΩ (voltage divider ratio 1:3). At this time, the UVLO pin voltage = 9V×(10kΩ / (20kΩ+10kΩ))=3V>2.5V, which is normal operation; when the voltage drops to 8V, UVLO=8V×(1 / 3)≈2.67V>2.5V, which is still normal; when the voltage drops to 7.5V, UVLO=7.5V×(1 / 3)=2.5V, triggering undervoltage protection.

[0084] Overvoltage protection: When the input voltage exceeds the set threshold, the output is cut off to prevent high voltage from damaging the subsequent circuitry.

[0085] When the voltage at the overvoltage detection pin (OVP) exceeds the overvoltage protection threshold (typically the chip's built-in 2.5V). Example: For a 24V power supply, the overvoltage detection branch uses R3=100kΩ and R4=10kΩ (voltage divider ratio 1:11). At this time, the OVP pin voltage = 24V×(10kΩ / (100kΩ+10kΩ))≈2.18V<2.5V, which is normal operation. When the voltage rises to 27.5V, OVP = 27.5V×(1 / 11)=2.5V, triggering overvoltage protection.

[0086] Overcurrent protection: When the circuit current exceeds the safe range, the output is cut off to prevent safety risks caused by overload or short circuit.

[0087] Optionally, the overcurrent protection will be triggered when the voltage across the current sampling resistor is greater than or equal to the overcurrent voltage threshold (usually 30mV built into the chip). Example: Using a 0.06Ω current sampling resistor, when the loop current reaches 0.5A, the voltage across the sampling resistor = 0.5A × 0.06Ω = 30mV, triggering overcurrent protection.

[0088] Optionally, the power switch is an N-channel MOSFET;

[0089] The drain of the power switching transistor is connected to the power input terminal of the intrinsically safe protection unit through a current sampling resistor;

[0090] The source of the power switch is connected to the output node of the intrinsically safe protection unit;

[0091] The output node is connected to the input terminal of the subsequent intrinsically safe protection unit or the output port of the modular intrinsically safe protection circuit.

[0092] Correspondingly, a dedicated protection chip (such as TI's LM5069 series) can be used for protection control, integrating a voltage comparator, current sensing amplifier, and MOSFET driver circuit, simplifying the peripheral design. The pin functions are as follows:

[0093] Undervoltage detection pin (UVLO): Connects to the undervoltage detection branch of the adjustable voltage divider network to monitor the lower limit of the input voltage.

[0094] Overvoltage Detection Pin (OVP): Connects to the overvoltage detection branch of the adjustable voltage divider network to monitor the upper limit of the input voltage.

[0095] Current sensing terminal (ISENSE): Differential input, directly connected to both ends of the current sampling resistor to monitor the loop current.

[0096] Drive output terminal (GATE): Directly connected to the gate of the power switch, outputting high and low levels to control the MOSFET's on and off states.

[0097] Understandably, the MOSFET drain is connected to the power input terminal through a current sampling resistor to ensure that all load current must flow through the sampling resistor, thereby achieving accurate current detection.

[0098] The MOSFET source is directly connected to the output node, providing a stable power supply to the subsequent circuitry or the next intrinsically safe protection unit.

[0099] The drive output (GATE) of the protection control chip is directly connected to the MOSFET gate, and the MOSFET is turned on / off by outputting high or low levels.

[0100] When the GATE pin outputs a high level (typically 10~12V), the gate-source voltage (VGS) of the MOSFET is greater than the turn-on voltage (e.g., VGS(th) = 4V), and the MOSFET enters a low-impedance on-state (RDS(on) ≈ a few milliohms). Turn-off condition: When the GATE pin outputs a low level (0V), VGS = 0V, the MOSFET is turned off, cutting off the power supply circuit.

[0101] In one exemplary embodiment, the modular intrinsically safe protection circuit further includes:

[0102] The timed restart unit is connected to the timer pin of the protection control chip;

[0103] The timed restart unit includes a timed capacitor and a timed resistor connected in series, which are used for automatic recovery circuit after the fault is cleared.

[0104] Timing capacitor (C): A low leakage current ceramic capacitor (such as 100nF~1μF, X7R material) is used to handle charging and discharging timing.

[0105] Timing resistor (R): A high-precision carbon film resistor (such as 10kΩ~100kΩ, ±5% accuracy) is used to control the charging and discharging rate of the capacitor.

[0106] After the two are connected in series, one end is connected to the timing pin of the protection control chip (such as the RT / CT pin of LM5069), and the other end is grounded.

[0107] Fault stage: When the circuit triggers protection (such as overcurrent), the protection control chip shuts down the power switch transistor, and at the same time, the timing pin outputs a high level, and the timing capacitor begins to discharge through the timing resistor (the discharge time is determined by the RC time constant τ=R×C).

[0108] Recovery phase: After the fault is cleared, the protection control chip detects that the voltage / current has returned to the normal range, and the timing capacitor begins to charge through the chip's internal circuitry; when the capacitor voltage reaches the chip's built-in threshold (such as 2.5V), the chip automatically outputs a drive signal to re-turn on the power switch and restore power supply.

[0109] Restart time adjustment: Adjust the restart delay time by replacing the timing capacitor or timing resistor to adapt to different scenario requirements.

[0110] In one exemplary embodiment, the modular intrinsically safe protection circuit further includes a status indication unit, comprising:

[0111] The positive terminal of the light-emitting diode is connected to the output terminal of the power switching transistor;

[0112] A current-limiting resistor is connected in series between the negative terminal of the LED and ground.

[0113] Light Emitting Diode (LED): Low-power surface-mount LEDs (such as 3mm red LEDs with a forward voltage drop of 1.8~2.2V) are used, providing moderate brightness to suit the dim environment underground.

[0114] Current limiting resistor (R) 限 ): Use 1kΩ~5kΩ carbon film resistors to limit the current flowing through the LED (usually controlled at 5~20mA to avoid burning out the LED).

[0115] Normal operating state: The power switch is turned on, there is voltage at the output node (e.g., 9~24V), the current flows through the LED positive terminal → current limiting resistor → ground, the LED lights up (red light is always on), indicating that the circuit is powered normally.

[0116] Protection status: The power switch is off, there is no voltage at the output node, no current flows through the LED, and it is off, indicating that the circuit is in undervoltage / overvoltage / overcurrent protection status.

[0117] Troubleshooting assistance: If the LED flashes frequently (alternating between on and off), it indicates that the circuit is in a "fault-recovery" cycle (such as intermittent short circuit), which can guide maintenance personnel to check the load or power supply stability.

[0118] In one exemplary embodiment, such as Figure 2 As shown, each intrinsically safe protection unit includes two intrinsically safe protection units connected in series: a first intrinsically safe protection unit and a second intrinsically safe protection unit. The output terminal of the first intrinsically safe protection unit is connected to the input terminal of the second intrinsically safe protection unit. The output terminal of the second intrinsically safe protection unit serves as the output port of the modular intrinsically safe protection circuit.

[0119] Furthermore, such as Figure 3 As shown, the protection control chip of the first intrinsically safe protection unit is U1 (model LM5069MM-2). Its undervoltage detection pin is connected to the voltage divider node of the undervoltage detection branch, its overvoltage detection pin is connected to the voltage divider node of the overvoltage detection branch, its output terminal is connected to the gate of the power switch, its timing pin is connected to the timing unit, and its current detection terminal is connected to both ends of the current sampling resistor.

[0120] The power switch of the first intrinsically safe protection unit is Q1 (model NCE6080K, N-channel MOSFET). Its gate is connected to the output terminal of the protection control chip U1, its drain is connected to the power input terminal of the first intrinsically safe protection unit through the current sampling resistor R1, and its source is connected to the output node of the first intrinsically safe protection unit (this node is also connected to the input terminal of the second intrinsically safe protection unit).

[0121] The adjustable voltage divider network of the first intrinsically safe protection unit includes an undervoltage detection branch and an overvoltage detection branch: the undervoltage detection branch consists of two series-connected undervoltage protection resistors R3 and R16, and their voltage divider nodes are connected to the undervoltage detection pin of the protection control chip U1; the overvoltage detection branch consists of two series-connected overvoltage protection resistors R4 and R10, and their voltage divider nodes are connected to the overvoltage detection pin of the protection control chip U1.

[0122] The current sampling resistor of the first intrinsically safe protection unit is R1. One end of R1 is connected to the power input terminal of the first intrinsically safe protection unit, and the other end is connected to the drain of the power switching transistor Q1. Both ends are connected to the current detection terminal of the protection control chip U1.

[0123] The timed restart unit of the first intrinsically safe protection unit includes a timed capacitor C4 and a timed resistor R17 connected in series. The series connection point of the two is connected to the timed pin of the protection control chip U1, and the other end is grounded.

[0124] The status indication unit of the first intrinsically safe protection unit includes a light-emitting diode LED1 and a current-limiting resistor R8. The positive terminal of LED1 is connected to the source of the power switch Q1 (the output node of the first intrinsically safe protection unit), and the negative terminal is connected to ground after being connected in series with the current-limiting resistor R8.

[0125] The first intrinsically safe protection unit also includes a filter capacitor C1: connected between the power input terminal of the first intrinsically safe protection unit and ground, used to filter out high-frequency interference from the input power supply. One end of the capacitor is connected to the input power supply, and the other end is grounded to provide a stable DC input for subsequent circuits.

[0126] Furthermore, such as Figure 3 As shown, the protection control chip of the second intrinsically safe protection unit is U2 (model LM5069MM-2). Its undervoltage detection pin is connected to the voltage divider node of the undervoltage detection branch, its overvoltage detection pin is connected to the voltage divider node of the overvoltage detection branch, its output terminal is connected to the gate of the power switch, its timing pin is connected to the timing unit of the second intrinsically safe protection unit, and its current detection terminal is connected to both ends of the current sampling resistor of the second intrinsically safe protection unit.

[0127] The power switch of the second intrinsically safe protection unit is Q2 (model NCE6080K, N-channel MOSFET). Its gate is connected to the output terminal of the protection control chip U2, its drain is connected to the power input terminal of the second intrinsically safe protection unit (i.e., the output node of the first intrinsically safe protection unit) through the current sampling resistor R2, and its source is connected to the output node of the second intrinsically safe protection unit (this node serves as the output port of the modular intrinsically safe protection circuit).

[0128] The adjustable voltage divider network of the second intrinsically safe protection unit includes an undervoltage detection branch and an overvoltage detection branch: the undervoltage detection branch consists of two series-connected undervoltage protection resistors R5 and R18, and their voltage divider node is connected to the undervoltage detection pin of the protection control chip U2; the overvoltage detection branch consists of two series-connected overvoltage protection resistors R6 and R9, and their voltage divider node is connected to the overvoltage detection pin of the protection control chip U2.

[0129] The current sampling resistor of the second intrinsically safe protection unit is R2. One end of R2 is connected to the power input terminal of the second intrinsically safe protection unit (the output node of the first intrinsically safe protection unit), and the other end is connected to the drain of the power switch Q2. Both ends are connected to the current detection terminal of the protection control chip U2.

[0130] The second intrinsically safe protection unit's timed restart unit includes a timed capacitor C5 and a timed resistor R19 connected in series. The series connection point of the two is connected to the timed pin of the protection control chip U2, and the other end is grounded.

[0131] The status indication unit of the second intrinsically safe protection unit includes a light-emitting diode LED2 and a current-limiting resistor R7. The positive terminal of LED2 is connected to the output port of the second intrinsically safe protection unit (the source of the power switch Q2), and the negative terminal is connected to ground after being connected in series with the current-limiting resistor R7.

[0132] The second intrinsically safe protection unit also includes output-related components R11 and R12: R12 is connected in series between the output node of the first intrinsically safe protection unit and the input terminal of the second intrinsically safe protection unit to limit the current and prevent instantaneous current surges between the two units; R11 is connected in series between the output node (Q2 source) of the second intrinsically safe protection unit and the final output port OUT to further stabilize the output current and protect the load.

[0133] When the input port IN is connected to a DC power supply (DC9-24V), C1 first filters the input voltage. In the first intrinsically safe protection unit, R3, R16 and R4, R10 divide the voltage respectively, and input the undervoltage and overvoltage detection signals to U1; U1, according to its internal logic, controls the on / off state of Q1 through pin 10 to realize overvoltage, undervoltage, and overcurrent protection (overcurrent is detected by sampling through R1), and LED1 synchronously indicates the working status of the first intrinsically safe protection unit.

[0134] The voltage protected by the first intrinsically safe protection unit is input to the second intrinsically safe protection unit. R5, R18 and R6, R9 repeatedly divide the voltage for detection. U2 controls the on / off state of Q2 to complete the secondary protection. The final voltage is output through OUT, and LED2 indicates the overall output status. After the fault is cleared, capacitors C4 and C5 connected to pin 6 of U1 and U2 charge and discharge, realizing the automatic restart function of the circuit.

[0135] This embodiment constructs an intrinsically safe circuit with multi-level protection and automatic recovery by connecting two intrinsically safe protection units in series, using hardware voltage divider sampling and MOSFET switching control. It is suitable for scenarios with stringent requirements for power supply stability and safety.

[0136] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0137] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A modular intrinsically safe protection circuit, characterized in that, Includes at least one intrinsically safe protection element, each intrinsically safe protection element comprising: The protection control chip (11) monitors the input voltage and current signals and outputs on / off control signals; The power switch (12) is connected to the output terminal of the protection control chip (11) and is used to perform switching actions according to the on / off control signal; An adjustable voltage divider network (13) is connected to the input power supply terminal. The undervoltage protection threshold or overvoltage protection threshold of the modular intrinsically safe protection circuit is set by adjusting the resistance value. A replaceable current sampling resistor (14) is connected in series in the power supply circuit to set the overcurrent protection threshold of the modular intrinsically safe protection circuit. In this way, by replacing the resistor of the adjustable voltage divider network (13) and / or the current sampling resistor (14), the modular intrinsically safe protection circuit can be adapted to intrinsically safe power supplies of different voltage / current levels. Each intrinsically safe protection unit includes two intrinsically safe protection units connected in series: a first intrinsically safe protection unit and a second intrinsically safe protection unit. The output terminal of the first intrinsically safe protection unit is connected to the input terminal of the second intrinsically safe protection unit; The output terminal of the second intrinsically safe protection unit serves as the output port of the modular intrinsically safe protection circuit; The adjustable voltage divider network (13) includes: The undervoltage detection branch includes at least two series undervoltage protection resistors, and the voltage divider node between the two series undervoltage protection resistors is connected to the undervoltage detection pin of the protection control chip (11). The overvoltage detection branch includes at least two series overvoltage protection resistors, and the voltage divider node between the two series overvoltage protection resistors is connected to the overvoltage detection pin of the protection control chip (11). The resistance value of the undervoltage protection resistor can be replaced to adjust the undervoltage protection threshold. The resistance value of the overvoltage protection resistor can be replaced to adjust the overvoltage protection threshold. The protection control chip (11) is configured to turn off the power switch (12) when one of the following shutdown conditions is met; the shutdown conditions include: When the voltage at the undervoltage detection pin is less than the undervoltage protection threshold, or The voltage at the overvoltage detection pin is greater than the overvoltage protection threshold, or The voltage across the current sampling resistor (14) is greater than or equal to the overcurrent voltage threshold. The power switch (12) is an N-channel MOSFET. The drain of the power switch (12) is connected to the power input terminal of the intrinsically safe protection unit through the current sampling resistor (14); The source of the power switch (12) is connected to the output node of the intrinsically safe protection unit; The output node is connected to the input terminal of the subsequent intrinsically safe protection unit or the output port of the modular intrinsically safe protection circuit. The protection control chip (11) further includes: The current detection terminal is connected to both ends of the current sampling resistor (14); The drive output terminal is directly connected to the gate of the power switch (12); The current detection terminal is configured to detect the voltage across the current sampling resistor (14); The modular intrinsically safe protection circuit further includes: The timed restart unit is connected to the timed pin of the protection control chip (11); The timed restart unit includes a timed capacitor and a timed resistor connected in series, which are used to automatically restore the circuit after the fault is cleared. The modular intrinsically safe protection circuit further includes a status indication unit, comprising: A light-emitting diode, the positive terminal of which is connected to the output terminal of the power switch (12); A current-limiting resistor is connected in series between the negative terminal of the light-emitting diode and ground; The overvoltage protection resistor or the undervoltage protection resistor adopts a pluggable or solderable replacement package, so that the modular intrinsically safe protection circuit can be adapted to 9V, 12V and 24V input power supply. The current sampling resistor (14) adopts a terminal connection or pad packaging form, so that the modular intrinsically safe protection circuit can be adapted to a 0.5A-5A load.

Images