Bus short circuit isolation circuit and fire alarm system

Abstract

The application discloses a kind of bus short-circuit isolation circuit and fire alarm system, for realizing the short-circuit isolation of annular loop fire-fighting equipment on fire-fighting bus, comprising: low-voltage detection module is used to detect the low voltage drop signal on fire-fighting bus when short-circuit occurs, triggering module is used to turn on after receiving low voltage drop signal, switch control module is used to cut off according to on signal to make the negative end of short-circuit isolator high resistance state;Or, switch control module is used to detect the short-circuit signal at short-circuit isolator when short-circuit occurs, switch control module is cut off according to short-circuit signal, triggering module is used to keep the cut-off state of switch control module to make the negative end of short-circuit isolator high resistance state;When short-circuit is removed, triggering module is used to receive short-circuit removal signal, and switch control module is used to turn on according to short-circuit removal signal to make the negative end of short-circuit isolator low resistance state.The application effectively improves the communication stability of fire alarm system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fire control technology, and in particular to a bus short-circuit isolation circuit and a fire alarm system. BACKGROUND

[0002] In a bus system fire alarm system, a local bus fault (for example, short circuit) often causes the entire alarm system to fail to work normally. In order to avoid this fault, a short-circuit isolator is introduced into the bus circuit. The function of the fire short-circuit isolator is to isolate the part of the bus where the short-circuit fault occurs from the entire system when the short-circuit fault occurs, so as to ensure that the other parts of the system can work normally, and facilitate determination of the part of the bus where the fault occurs. When the short-circuit fault part of the bus is removed, the short-circuit isolator can automatically restore the work and re-integrate the isolated part into the system.

[0003] The short-circuit isolator on the market, whether it is a ring circuit or a tree circuit, when a short circuit occurs at a certain place of the bus and the short-circuit isolator starts isolation, it may cause 32 fire-fighting devices connected behind the isolator to be lost. Such a short-circuit isolator can be considered as a regional isolation. When the short-circuit isolator starts isolation, the fire detectors, manual alarm buttons and modules and other fire-fighting devices connected behind the isolator will not be able to report alarms, thereby causing poor stability of the fire alarm system, high maintenance cost and affecting the efficiency of the fire alarm. Therefore, it is an urgent problem for those skilled in the art to invent a reliable fire alarm system display circuit. SUMMARY

[0004] The purpose of the present application is to provide a bus short-circuit isolation circuit and a fire alarm system. In the present application, when the bus works normally, the switch control module connected to the negative input end IN- and the negative output end OUT- is closed and presents a low resistance state, thereby providing a low impedance path at the negative end of the bus. When the bus is short-circuited, the switch control module is disconnected, the negative input end IN- and the negative output end OUT- present a high resistance state, thereby cutting off the large current flow path and isolating the short-circuit part, and reducing the influence on the bus.

[0005] To solve the above technical problems, the present application provides a bus short-circuit isolation circuit for realizing short-circuit isolation of a ring circuit fire-fighting device on a fire-fighting bus, which comprises a switch control module, a low-voltage detection module and a trigger module.

[0006] The switch control module is electrically connected to the input signal end and the output signal end of the short-circuit isolator, the low-voltage detection module is electrically connected to the switch control module and the trigger module, and the trigger module is electrically connected to the switch control module.

[0007] The low-voltage detection module is configured to detect a low-voltage drop signal on the fire-fighting bus when a short circuit occurs at the end of the bus, the trigger module is configured to be turned on after receiving the low-voltage drop signal, and the switch control module is configured to be turned off according to the turn-on signal of the trigger module so that the negative end of the short-circuit isolator is in a high-impedance state.

[0008] Alternatively, the switch control module is configured to detect an input voltage at the short-circuit isolator when a short circuit occurs in the bus, the switch control module is turned off according to the input voltage, and the trigger module is configured to maintain the off state of the switch control module so that the negative end of the short-circuit isolator is in a high-impedance state.

[0009] When the short circuit is removed, the trigger module is configured to receive a short-circuit removal signal, and the switch control module is configured to be turned on according to the short-circuit removal signal so that the negative end of the short-circuit isolator is in a low-impedance state.

[0010] Preferably, the switch control module comprises a first diode, a second diode, a first switch module and a second switch module.

[0011] The anode of the first diode is electrically connected to the first switch module, a positive input end and a positive output end of the short-circuit isolator respectively, and the cathode of the first diode is electrically connected to the low-voltage detection module and the first switch module respectively.

[0012] The anode of the second diode is electrically connected to a negative output end of the short-circuit isolator, and the cathode of the second diode is electrically connected to the anode of the first diode and the first switch module respectively.

[0013] The first switch module is electrically connected to a negative input end of the short-circuit isolator and the trigger module respectively.

[0014] The second switch module is electrically connected to a negative output end of the short-circuit isolator, the first switch module and the trigger module respectively.

[0015] Preferably, the first switch module comprises a first NMOS tube, a third diode, a fourth diode and a first fast-recovery diode.

[0016] The drain of the first NMOS is electrically connected with the negative input end of the short-circuit isolator, the anode of the third diode, the cathode of the fourth diode and the second switch module respectively, the gate of the first NMOS is electrically connected with the second switch module, the first end of the first fast recovery diode, the trigger module and the cathode of the first diode respectively, the source of the first NMOS and the anode of the fourth diode are grounded, the cathode of the third diode is electrically connected with the positive input end and the positive output end of the short-circuit isolator, the second end of the first fast recovery diode and the anode of the first diode respectively, the third end of the first fast recovery diode is electrically connected with the trigger module and the second switch module respectively.

[0017] The first NMOS is used to cut off the negative input end of the short-circuit isolator when the short circuit occurs, and restore the negative input end of the short-circuit isolator when the short circuit is removed.

[0018] Preferably, the second switch module comprises a second NMOS, a fifth diode, a sixth diode, a second fast recovery diode and a first resistor.

[0019] The drain of the second NMOS is electrically connected with the negative output end of the short-circuit isolator, the anode of the first diode, the first end of the second fast recovery diode and the cathode of the fifth diode respectively, the gate of the second NMOS is electrically connected with the cathode of the sixth diode, the first end of the first resistor, the first switch module and the trigger module respectively, the source of the second NMOS and the anode of the fifth diode are grounded, the anode of the sixth diode and the second end of the first resistor are grounded, and the second end of the second fast recovery diode is electrically connected with the negative input end of the short-circuit isolator.

[0020] The second NMOS is used to cut off the negative output end of the short-circuit isolator when the short circuit occurs, and restore the negative output end of the short-circuit isolator when the short circuit is removed.

[0021] Preferably, the first switch module further comprises a second resistor, a third resistor and a first capacitor.

[0022] The first end of the second resistor, the first end of the third resistor, the first end of the first capacitor and the trigger module are electrically connected with the third end of the first fast recovery diode, the second end of the second resistor is electrically connected with the cathode of the first diode and the low-voltage detection module respectively, the second end of the third resistor is electrically connected with the second end of the first capacitor, the second switch module, the gate of the first NMOS and the first end of the first fast recovery diode respectively.

[0023] Preferably, the low-voltage detection module includes a first PNP transistor, a third NMOS transistor, a fourth resistor, a fifth resistor, and a seventh diode;

[0024] The emitter of the first PNP transistor is electrically connected to the switch control module, the first terminal of the fourth resistor, the drain of the third NMOS transistor, and the trigger module. The second terminal of the fourth resistor is electrically connected to the anode of the seventh diode and the first terminal of the fifth resistor. The second terminal of the fifth resistor is grounded. The cathode of the seventh diode is electrically connected to the base of the first PNP transistor. The collector of the first PNP transistor is electrically connected to the gate of the third NMOS transistor, and the source of the third NMOS transistor is grounded.

[0025] Preferably, the low-voltage detection module further includes a sixth resistor, a seventh resistor, an eighth resistor, and a second capacitor;

[0026] The first end of the sixth resistor is electrically connected to the emitter of the first PNP transistor, the second end of the sixth resistor is electrically connected to the drain of the third NMOS transistor, the first end of the seventh resistor is electrically connected to the collector of the first PNP transistor, the second end of the seventh resistor is electrically connected to the gate of the third NMOS transistor, the first end of the eighth resistor and the first end of the second capacitor, and the second end of the eighth resistor and the second end of the second capacitor are grounded.

[0027] Preferably, the trigger module includes a second PNP transistor, a third fast recovery diode, and a fourth NMOS transistor;

[0028] The emitter of the second PNP transistor is electrically connected to the switch control module, the collector of the second PNP transistor is electrically connected to the first terminal of the third fast recovery diode, the second terminal of the third fast recovery diode is electrically connected to the low-voltage detection module, the collector of the second PNP transistor and the third terminal of the third fast recovery diode are grounded, the gate of the fourth NMOS transistor is electrically connected to the third terminal of the third fast recovery diode, the drain of the fourth NMOS transistor is electrically connected to the switch control module, and the source of the fourth NMOS transistor is grounded.

[0029] Preferably, the trigger module further includes an eighth diode, a ninth diode, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third capacitor, a fourth capacitor, a fifth capacitor, and a sixth capacitor;

[0030] The first terminal of the third capacitor and the first terminal of the fourth capacitor are electrically connected to the emitter of the second PNP transistor. The second terminal of the third capacitor and the second terminal of the fourth capacitor are grounded. The anode of the eighth diode is electrically connected to the first terminal of the ninth resistor. The second terminal of the ninth resistor, the first terminal of the tenth resistor, and the first terminal of the fifth capacitor are grounded. The cathode of the eighth diode is electrically connected to the base of the second PNP diode. The second terminal of the tenth resistor is electrically connected to the collector of the second PNP diode and the first terminal of the eleventh resistor. The second terminal of the eleventh resistor is electrically connected to the first terminal of the third fast recovery diode. The second terminal of the fifth capacitor is electrically connected to the third terminal of the third fast recovery diode, the first terminal of the twelfth resistor, and the first terminal of the sixth capacitor. The second terminal of the twelfth resistor is electrically connected to the second terminal of the sixth capacitor, the cathode of the ninth diode, the first terminal of the thirteenth resistor, and the gate of the fourth NMOS transistor. The anode of the ninth diode and the second terminal of the thirteenth resistor are grounded.

[0031] To address the aforementioned technical problems, this application also provides a fire alarm system, including the aforementioned bus short-circuit isolation circuit. The bus short-circuit isolation circuit is used to protect a fire-fighting device on the fire-fighting bus. Each fire-fighting device is connected to the fire-fighting bus through a bus short-circuit isolation circuit installed inside its base or by having the bus short-circuit isolation circuit built into it.

[0032] The bus short-circuit isolation circuit of the present invention has the following beneficial effects. The bus short-circuit isolation circuit disclosed in the present invention includes: a switch control module, a low-voltage detection module, and a trigger module;

[0033] The switch control module is electrically connected to the input signal terminal and the output signal terminal of the short-circuit isolator, respectively. The low-voltage detection module is electrically connected to the switch control module and the trigger module, respectively. The trigger module is electrically connected to the switch control module. The low-voltage detection module is used to detect the low voltage drop signal on the fire bus when the end of the bus is short-circuited. The trigger module is used to turn on after receiving the low voltage drop signal. The switch control module is used to turn off according to the turn-on signal of the trigger module so that the negative terminal of the short-circuit isolator is in a high-resistance state. Alternatively, the switch control module is used to detect the input terminal voltage at the short-circuit isolator when the bus is short-circuited. The switch control module is turned off according to the input terminal voltage. The trigger module is used to maintain the off state of the switch control module so that the negative terminal of the short-circuit isolator is in a high-resistance state. When the short circuit is released, the trigger module is used to receive the short-circuit release signal. The switch control module is used to turn on according to the short-circuit release signal so that the negative terminal of the short-circuit isolator is in a low-resistance state. Therefore, when a short circuit occurs in the cable between two adjacent fire-fighting devices on the fire bus, the bus short-circuit isolation circuit on the two fire-fighting devices is triggered, automatically isolating the short-circuited part between the two fire-fighting devices. This ensures that the communication between the detectors on the two fire-fighting devices and other fire-fighting devices and controllers on the bus is not affected. When the short circuit is cleared, the two fire-fighting devices can resume normal operation. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort:

[0035] Figure 1 This is a schematic block diagram of a bus short-circuit isolation circuit according to a preferred embodiment of the present invention;

[0036] Figure 2 This is a ring circuit diagram of the isolation base of a bus short-circuit isolation circuit according to a preferred embodiment of the present invention;

[0037] Figure 3 This is a circuit diagram of a bus short-circuit isolation circuit according to a preferred embodiment of the present invention. Detailed Implementation

[0038] The core of this invention is to provide a bus short-circuit isolation circuit and a fire alarm system, which can effectively improve the communication stability of the fire alarm system and reduce maintenance costs.

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example One

[0041] Figure 1 A schematic diagram of a bus short-circuit isolation circuit provided in this application includes:

[0042] In summary, this application provides a bus short-circuit isolation circuit for realizing short-circuit isolation of ring circuit fire-fighting equipment on a fire bus. In this solution, the bus short-circuit isolation circuit includes: a switch control module 1, a low-voltage detection module 2, and a trigger module 3.

[0043] The switch control module 1 is electrically connected to the input signal terminal and the output signal terminal of the short-circuit isolator, respectively. The low-voltage detection module 2 is electrically connected to the switch control module 1 and the trigger module 3, respectively. The trigger module 3 is electrically connected to the switch control module 1.

[0044] The low-voltage detection module 2 is used to detect the low voltage drop signal on the fire bus when the end of the bus is short-circuited. The trigger module 3 is used to turn on after receiving the low voltage drop signal. The switch control module 1 is used to turn off according to the turn-on signal of the trigger module so that the negative terminal of the short-circuit isolator is in a high-resistance state.

[0045] Alternatively, the switch control module 1 is used to detect the input voltage at the short-circuit isolator when the bus is short-circuited, the switch control module 1 is turned off according to the input voltage, and the trigger module 3 is used to maintain the off state of the switch control module 1 so that the negative terminal of the short-circuit isolator in a high-impedance state.

[0046] When the short circuit is released, the trigger module 3 is used to receive the short circuit release signal, and the switch control module 1 is used to conduct according to the short circuit release signal so that the negative terminal of the short circuit isolator is in a low resistance state.

[0047] In existing technologies, according to the specifications for automatic fire alarm systems (GB50116), bus short-circuit isolators should be installed on the system bus. The total number of fire detectors, manual fire alarm buttons, and modules protected by each bus short-circuit isolator should not exceed 32. Therefore, in existing technologies, whether the short-circuit isolator is a ring circuit or a tree circuit, when a short circuit triggers the isolator to activate isolation, it may cause the loss of 32 fire-fighting devices connected to the isolator. This short-circuit isolation technology is area isolation. When the short-circuit isolator activates isolation, the fire detectors, manual fire alarm buttons, and modules connected to the isolator will all fail to alarm.

[0048] To address the issue of excessive fire-fighting equipment loss during short-circuit isolator activation, this application proposes a bus short-circuit isolation circuit. Please refer to [link to relevant documentation]. Figure 2 When each fire-fighting device in the bus is connected to the short-circuit isolator in a daisy-chain loop, each device connects to the isolator via a bus short-circuit isolation circuit either internally installed in its base or built into itself, providing single-point short-circuit isolation. When a short circuit occurs between two adjacent fire-fighting devices on the bus, the isolation circuits on these two devices are triggered, automatically isolating the short circuit between them. Communication between the detectors on these two devices and other fire-fighting devices and controllers on the bus remains unaffected. When the short circuit is released, the short-circuit isolator resumes normal operation. Therefore, this application significantly improves the communication stability of the fire alarm system, effectively reduces maintenance costs, and ensures the efficiency of the fire alarm system.

[0049] Specifically, in real-world scenarios, to ensure the area coverage of fire-fighting equipment, the wiring for fire-fighting equipment is very long. In this case, the resistance of the fire-fighting bus is very high. When a short circuit occurs, the bus voltage cannot be pulled down to zero volts. At this time, the voltage drop generated on the fire-fighting bus is large, and the voltage to the short-circuit isolator will drop very low. Therefore, on the one hand, when a short circuit occurs at the end of the fire-fighting bus, the low-voltage detection module 2 triggers the short-circuit isolator to operate. When the voltage drops to a certain level, a signal is generated to trigger module 3. Trigger module 3 is used to receive the signal from the low-voltage detection module and then conduct, while switch control module 1 is used to cut off according to the conduction signal so that the negative terminal of the short-circuit isolator is in a high-resistance state.

[0050] Specifically, on the other hand, when a short circuit occurs at a certain port of the short-circuit isolator, the switch control module 1 directly detects that the input voltage of the short-circuit isolator is zero volts when the short circuit occurs. The switch control module 1 is then turned off, and the trigger module 3 maintains the off state of the switch control module 1 so that the negative terminal of the short-circuit isolator in a high-impedance state.

[0051] Based on the above two scenarios, when the short circuit is released, the trigger module 3 receives the short circuit release signal, and the switch control module 1 is used to conduct according to the short circuit release signal so that the negative terminal of the short circuit isolator is in a low resistance state.

[0052] In summary, this application provides a bus short-circuit isolation circuit. This circuit includes a switch control module 1, a low-voltage detection module 2, and a trigger module 3. The switch control module 1 is electrically connected to the input signal terminal and the output signal terminal of the short-circuit isolator, respectively. The low-voltage detection module 2 is electrically connected to both the switch control module 1 and the trigger module 3, and the trigger module 3 is electrically connected to the switch control module 1. The low-voltage detection module 2 detects the low voltage drop signal on the fire bus when the end of the bus is short-circuited. The trigger module 3 is turned on after receiving the low voltage drop signal, and the switch control module 1 is turned off according to the on signal of the trigger module, so that the negative terminal of the short-circuit isolator is in a high-resistance state. Alternatively, the switch control module 1 detects the input voltage signal at the short-circuit isolator when the bus is short-circuited, and the switch control module 1 is turned off according to the input voltage. The trigger module 3 maintains the off state of the switch control module 1, so that the negative terminal of the short-circuit isolator is in a high-resistance state. When the short circuit is released, the trigger module 3 receives the short-circuit release signal, and the switch control module 1 is turned on according to the short-circuit release signal, so that the negative terminal of the short-circuit isolator is in a low-resistance state. The short-circuit isolator has two input signal terminals: a positive input terminal IN+ and a negative input terminal IN-. Its output signal terminals include a positive output terminal OUT+ and a negative output terminal OUT-. Therefore, when a short circuit occurs between two adjacent fire-fighting devices on the fire protection bus, the bus short-circuit isolation circuit on both devices is triggered, automatically isolating the short-circuit portion between them. This ensures that communication between the detectors on the two devices and other fire-fighting equipment and controllers on the bus is unaffected. When the short circuit is released, both short-circuit isolators can resume normal operation.

[0053] Based on the above embodiments:

[0054] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a switch control module 1 provided in this application.

[0055] In a preferred embodiment, the switch control module 1 includes a first diode D1, a second diode TVS1, a first switch module 11, and a second switch module 12;

[0056] The anode of the first diode D1 is electrically connected to the positive input terminal IN+ and the positive output terminal of the first switch module 11 and the short-circuit isolator, respectively. The cathode of the first diode D1 is electrically connected to the low-voltage detection module 2 and the first switch module 11, respectively. The first diode D1 is used to prevent capacitive backflow from the isolation circuit into the fire bus.

[0057] The anode of the second diode TVS1 is electrically connected to the negative output terminal IN- on the short-circuit isolator, and the cathode of the second diode TVS2 is electrically connected to the anode of the first diode D1 and the first switching module 11 respectively; the second diode TVS2 is used to absorb surge voltage and prevent excessive voltage from damaging downstream components.

[0058] The first switch module 11 is electrically connected to the negative input terminal IN- of the short-circuit isolator and the trigger module 3, respectively.

[0059] The second switch module 12 is electrically connected to the negative output terminal OUT- of the short-circuit isolator, the first switch module 11, and the trigger module 3, respectively.

[0060] The first switch module 11 is used to disconnect the negative input terminal of the short-circuit isolator when a short circuit occurs, and restore the negative input terminal IN- of the short-circuit isolator when the short circuit is released; the second switch module 12 is used to disconnect the negative output terminal OUT- of the short-circuit isolator when a short circuit occurs, and restore the negative output terminal OUT- of the short-circuit isolator when the short circuit is released.

[0061] Specifically, when the bus is powered on, the voltage rises, and both the first switch module 11 and the second switch module 12 are turned on, forming a low-impedance path between the negative input terminal IN- and the negative output terminal OUT-. When the positive output terminal OUT+ and the negative output terminal OUT- (or the positive input terminal IN+ and the negative input terminal IN-) are short-circuited, both the first switch module 11 and the second switch module 12 are turned off, and the negative input terminal IN- and the negative output terminal OUT- are in a high-impedance state, cutting off the path for high current flow. At this time, the short-circuited part is isolated, reducing the impact on the bus.

[0062] In a preferred embodiment, the first switching module 11 includes a first NMOS transistor Q5A, a third diode TVS2, a fourth diode D6, and a first fast recovery diode D2;

[0063] The drain of the first NMOS transistor Q5A is electrically connected to the negative input terminal IN- of the short-circuit isolator, the anode of the third diode TVS2, the cathode of the fourth diode D6, and the second switch module 12. The gate of the first NMOS transistor Q5A is electrically connected to the second switch module 12, the first terminal of the first fast recovery diode D2, the trigger module 3, and the cathode of the first diode. The source of the first NMOS transistor Q5A and the anode of the fourth diode D6 are grounded. The cathode of the third diode TVS2 is electrically connected to the positive input terminal IN+ and the positive output terminal OUT+ of the short-circuit isolator, the second terminal of the first fast recovery diode D2, and the anode of the first diode D1. The third terminal of the first fast recovery diode D2 is electrically connected to the trigger module 3 and the second switch module 12.

[0064] The first NMOS transistor Q5A is used to disconnect the negative input terminal of the short-circuit isolator when a short circuit occurs, and to restore the negative input terminal IN- of the short-circuit isolator when the short circuit is released.

[0065] Specifically, when the bus is powered on, the voltage rises, and both the first and second NMOS transistors are turned on, forming a low-impedance path at the IN- and OUT- ports.

[0066] In a preferred embodiment, the second switching module 12 includes a second NMOS transistor Q5B, a fifth diode D8, a sixth diode D10, a second fast recovery diode D3, and a first resistor R15;

[0067] The drain of the second NMOS transistor Q5B is electrically connected to the negative output terminal OUT- of the short-circuit isolator, the anode of the first diode, the first terminal of the second fast recovery diode D3, and the cathode of the fifth diode D8. The gate of the second NMOS transistor Q5B is electrically connected to the cathode of the sixth diode D10, the first terminal of the first resistor R15, the first switch module 11, and the trigger module 3. The source of the second NMOS transistor Q5B and the anode of the fifth diode D8 are grounded. The anode of the sixth diode D10 and the second terminal of the first resistor R15 are grounded. The second terminal of the second fast recovery diode D3 is electrically connected to the negative input terminal IN- of the short-circuit isolator.

[0068] The second NMOS transistor Q5B is used to disconnect the negative output terminal OUT- of the short-circuit isolator when a short circuit occurs, and to restore the negative output terminal OUT- of the short-circuit isolator when the short circuit is released.

[0069] When the positive output terminal OUT+ and the negative output terminal OUT- (or the positive input terminal IN+ and the negative input terminal IN-) are connected only by wires, the voltage of L+ (OUT+ & IN+) will be pulled down to 0V. When the voltage of L+ drops to 0V, the first fast recovery diode D2 turns on, and the voltage of the VGS network connected to the positive terminal of D2 drops, causing the VGS of the first NMOS transistor Q5A and the second NMOS transistor Q5B to be lower than the minimum turn-on voltage of 1V. The first NMOS transistor Q5A and the second NMOS transistor Q5B turn off and are in a high-impedance state, cutting off the high current path. At this time, the voltage of L+ rises rapidly. Since L+ is shorted to the negative output terminal OUT-, the voltages of the positive output terminal OUT+ and the negative output terminal OUT- are basically equal, causing the second fast recovery diode D3 to conduct. After the negative output terminal OUT- passes through the second fast recovery diode D3, the voltage of the trigger network in the trigger module drops by about 0.5V compared to the voltage of OUT+, and the trigger module conducts, keeping the first NMOS transistor Q5A and the second NMOS transistor Q5B in the off state. The negative input terminal IN- and the negative output terminal OUT- are in a high-impedance state.

[0070] In a preferred embodiment, the first switch module 11 further includes a second resistor R7, a third resistor R10, and a first capacitor C2;

[0071] The first terminal of the second resistor R7, the first terminal of the third resistor R10, the first terminal of the first capacitor C2, and the trigger module 3 are all electrically connected to the third terminal of the first fast recovery diode D2. The second terminal of the second resistor R7 is electrically connected to the cathode of the first diode and the low-voltage detection module 2, respectively. The second terminal of the third resistor R10 is electrically connected to the second terminal of the first capacitor C2, the second switching module, the gate of the first NMOS, and the first terminal of the first fast recovery diode D2, respectively. In this embodiment, the first switching module 11 is also equipped with the second resistor R7 and the third resistor R10 to serve as voltage dividers and current limiters, protecting the first fast recovery diode D2 from damage caused by sudden high voltage changes, so that the gate voltages of Q5A and Q5B are not too high; the first capacitor C2 is used to filter out interference from different frequency band signals in the output voltage and to perform energy storage.

[0072] In a preferred embodiment, the low-voltage detection module 2 includes a first PNP transistor Q2, a third NMOS transistor Q4, a fourth resistor R3, a fifth resistor R6, and a seventh diode ZD2;

[0073] The emitter of the first PNP transistor Q2 is electrically connected to the switch control module 1, the first terminal of the fourth resistor R3, the drain of the third NMOS transistor Q4, and the trigger module 3. The second terminal of the fourth resistor R3 is electrically connected to the anode of the seventh diode ZD2 and the first terminal of the fifth resistor R6. The second terminal of the fifth resistor R6 is grounded. The cathode of the seventh diode ZD2 is electrically connected to the base of the first PNP transistor Q2. The collector of the first PNP transistor Q2 is electrically connected to the gate of the third NMOS transistor Q4, and the source of the third NMOS transistor Q4 is grounded.

[0074] Specifically, when a short circuit occurs at the end of the fire alarm bus, the low-voltage detection module 2 triggers the short-circuit isolator to operate. When the input voltage on the short-circuit isolator drops to a certain level, the bus voltage is lower than the minimum turn-on voltage of the circuit consisting of resistor R6, the seventh diode ZD2, and the first PNP transistor Q2, preventing the first PNP transistor Q2 from conducting. At this time, the first PNP transistor Q2 is cut off, the gate (G) of the third NMOS transistor Q4 is at a low level, and the drain (D) of the third NMOS transistor Q4 outputs a high level, thereby turning on the trigger module 3. The VGS of the first NMOS transistor Q5A and the second NMOS transistor Q5B are pulled low and cut off, so that the negative terminal of the short-circuit is in a high-impedance state.

[0075] In a preferred embodiment, the low-voltage detection module 2 further includes a sixth resistor R4, a seventh resistor R8, an eighth resistor R9, and a second capacitor C3;

[0076] The first terminal of the sixth resistor R4 is electrically connected to the emitter of the first PNP transistor, and the second terminal of the sixth resistor is electrically connected to the drain of the third NMOS transistor Q4. The first terminal of the seventh resistor R8 is electrically connected to the collector of the first PNP transistor, and the second terminal of the seventh resistor R8 is electrically connected to the gate of the third NMOS transistor Q4, the first terminal of the eighth resistor R9, and the first terminal of the second capacitor C3. The second terminals of the eighth resistor R9 and the second terminal of the second capacitor C3 are grounded. In this embodiment, the low-voltage detection module 2 also uses the sixth resistor R4, the seventh resistor R8, and the eighth resistor R9 for voltage division and current limiting, and uses the second capacitor C3 to ensure that it will not malfunction when the bus is at a low level.

[0077] In a preferred embodiment, the trigger module 3 includes a second PNP transistor Q9, a third fast recovery diode D5, and a fourth NMOS transistor Q6;

[0078] The emitter of the second PNP transistor Q9 is electrically connected to the switch control module 1. The collector of the second PNP transistor Q9 is electrically connected to the first terminal of the third fast recovery diode D5. The second terminal of the third fast recovery diode D5 is electrically connected to the low voltage detection module 2. The collector of the second PNP transistor Q9 and the third terminal of the third fast recovery diode D5 are grounded. The gate of the fourth NMOS transistor Q6 is electrically connected to the third terminal of the third fast recovery diode D5. The drain of the fourth NMOS transistor Q6 is electrically connected to the switch control module 1. The source of the fourth NMOS transistor Q6 is grounded.

[0079] Specifically, when the positive output terminal OUT+ and the negative output terminal OUT- (or the positive input terminal IN+ and the negative input terminal IN-) are only connected by wires, the voltage of L+ (OUT+ & IN+) will be pulled down to 0V. When the voltage of L+ drops to 0V, the first fast recovery diode D2 turns on, and the voltage of the VGS network connected to the positive terminal of D2 drops, causing the VGS of the first NMOS transistor Q5A and the second NMOS transistor Q5B to be lower than the minimum turn-on voltage of 1V. The first NMOS transistor Q5A and the second NMOS transistor Q5B turn off and are in a high-resistance state, cutting off the high current path. At this time, the voltage of L+ rises rapidly. Since L+ is shorted to the negative output terminal OUT-, the voltages of the positive output terminal OUT+ and the negative output terminal OUT- are basically equal, causing the second fast recovery diode D3 to conduct. After the negative output terminal OUT- passes through the second fast recovery diode D3, the second PNP transistor Q9 conducts, the third fast recovery diode D5 conducts, and the fourth NMOS transistor conducts. The VGS of the first NMOS transistor Q5A and the second NMOS transistor Q5B are pulled low, so that the first NMOS transistor Q5A and the second NMOS transistor Q5B remain in the off state, and the negative input terminal IN- and the negative output terminal OUT- are in a high-impedance state.

[0080] Based on the above two scenarios, when the short circuit is removed, the first NMOS transistor Q5A and the second NMOS transistor Q5B are turned on, making the negative input terminal IN- low and connected to GND. GND is connected to the negative output terminal OUT-, so the negative output terminal OUT- quickly goes low. The second fast recovery diode D3 is turned off, the second PNP transistor Q9 is turned off, the third recovery diode D5 is turned off, and the fourth NMOS transistor Q6 is turned off. The VGS of the first NMOS transistor Q5A and the second NMOS transistor Q5B are pulled high, and the first NMOS transistor Q5A and the second NMOS transistor Q5B are turned on. The resistance between IN- and OUT- is low.

[0081] In a preferred embodiment, the trigger module 3 further includes an eighth diode ZD4, a ninth diode ZD3, a ninth resistor R12, a tenth resistor R13, an eleventh resistor R25, a twelfth resistor R11, a thirteenth resistor R14, a third capacitor C12, a fourth capacitor C11, a fifth capacitor C4, and a sixth capacitor C3.

[0082] The first terminals of the third capacitor C12 and the fourth capacitor C11 are electrically connected to the emitter of the second PNP transistor. The second terminals of the third capacitor C12 and the fourth capacitor C11 are grounded. The anode of the eighth diode ZD4 is electrically connected to the first terminal of the ninth resistor R12. The second terminal of the ninth resistor R12, the first terminal of the tenth resistor R13, and the first terminal of the fifth capacitor C4 are grounded. The cathode of the eighth diode ZD4 is electrically connected to the base of the second PNP diode. The second terminal of the tenth resistor R13 is connected to the collector of the second PNP diode and the eleventh resistor, respectively. The first terminal of R25 is electrically connected. The second terminal of the eleventh resistor R25 is electrically connected to the first terminal of the third fast recovery diode D5. The second terminal of the fifth capacitor C4 is electrically connected to the third terminal of the third fast recovery diode D5, the first terminal of the twelfth resistor R11, and the first terminal of the sixth capacitor C3. The second terminal of the twelfth resistor R11 is electrically connected to the second terminal of the sixth capacitor C3, the cathode of the ninth diode ZD3, the first terminal of the thirteenth resistor R14, and the gate of the fourth NMOS transistor. The anode of the ninth diode ZD3 and the second terminal of the thirteenth resistor R14 are grounded. In this embodiment, the trigger module 3 also sets an eighth diode ZD4 to ensure that the trigger voltage threshold cannot be lower than the regulated value of ZD4, sets a ninth diode ZD3 to protect the fourth NMOS transistor Q6, and prevents the voltage of the fourth NMOS transistor Q6_G from exceeding the regulated value of ZD3. The ninth resistor R12, the tenth resistor R13, the eleventh resistor R25, the twelfth resistor R11, and the thirteenth resistor R14 are set for voltage division and current limiting. The third capacitor C12, the fourth capacitor C11, the fifth capacitor C4, and the sixth capacitor C3 are set to filter out interference from different frequency band signals and to perform energy storage functions.

[0083] This application also provides a fire alarm system, including a bus short-circuit isolation circuit for protecting a fire-fighting device on the fire-fighting bus. Each fire-fighting device is connected to the fire-fighting bus through a bus short-circuit isolation circuit installed inside its base or a bus short-circuit isolation circuit built into itself.

[0084] For a description of the fire alarm system provided in this application, please refer to the above embodiments; further details will not be repeated here.

[0085] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0086] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0087] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bus short-circuit isolation circuit, characterized in that, A bus short-circuit isolation circuit for short-circuit isolation of fire-fighting equipment in a ring loop on a fire-fighting bus includes: a switch control module, a low-voltage detection module, and a trigger module; the switch control module includes a first diode, a second diode, a first switch module, and a second switch module. The switch control module is electrically connected to the input signal terminal and the output signal terminal of the short-circuit isolator, respectively. The low-voltage detection module is electrically connected to the switch control module and the trigger module, respectively. The trigger module is electrically connected to the switch control module. The low-voltage detection module is used to detect the low voltage drop signal on the fire bus when the end of the bus is short-circuited. The trigger module is used to turn on after receiving the low voltage drop signal. The switch control module is used to turn off according to the turn-on signal of the trigger module so that the negative terminal of the short-circuit isolator is in a high-resistance state. Alternatively, the switch control module is used to detect the input voltage at the short-circuit isolator when the bus is short-circuited, the switch control module is turned off according to the input voltage, and the trigger module is used to maintain the off state of the switch control module so that the negative terminal of the short-circuit isolator in a high-impedance state. When the short circuit is released, the triggering module is used to receive the short circuit release signal, and the switch control module is used to turn on according to the short circuit release signal so that the negative terminal of the short circuit isolator is in a low resistance state. The first switching module includes a first NMOS transistor, a third diode, a fourth diode, and a first fast recovery diode; The drain of the first NMOS transistor is electrically connected to the negative input terminal of the short-circuit isolator, the anode of the third diode, the cathode of the fourth diode, and the second switching module. The gate of the first NMOS transistor is electrically connected to the second switching module, the first terminal of the first fast recovery diode, the trigger module, and the cathode of the first diode. The source of the first NMOS transistor and the anode of the fourth diode are grounded. The cathode of the third diode is electrically connected to the positive input terminal and the positive output terminal of the short-circuit isolator, the second terminal of the first fast recovery diode, and the anode of the first diode. The third terminal of the first fast recovery diode is electrically connected to the trigger module and the second switching module. The first NMOS transistor is used to disconnect the negative input terminal of the short-circuit isolator when a short circuit occurs, and to restore the negative input terminal of the short-circuit isolator when the short circuit is released; The low-voltage detection module includes a first PNP transistor, a third NMOS transistor, a fourth resistor, a fifth resistor, and a seventh diode. The emitter of the first PNP transistor is electrically connected to the switch control module, the first terminal of the fourth resistor, the drain of the third NMOS transistor, and the trigger module, respectively. The second terminal of the fourth resistor is electrically connected to the anode of the seventh diode and the first terminal of the fifth resistor, respectively. The second terminal of the fifth resistor is grounded. The cathode of the seventh diode is electrically connected to the base of the first PNP transistor. The collector of the first PNP transistor is electrically connected to the gate of the third NMOS transistor. The source of the third NMOS transistor is grounded.

2. The bus short-circuit isolation circuit according to claim 1, characterized in that, The anode of the first diode is electrically connected to the positive input terminal and the positive output terminal of the first switch module and the short-circuit isolator, respectively, and the cathode of the first diode is electrically connected to the low-voltage detection module and the first switch module, respectively. The anode of the second diode is electrically connected to the negative output terminal of the short-circuit isolator, and the cathode of the second diode is electrically connected to the anode of the first diode and the first switching module, respectively. The first switch module is electrically connected to the negative input terminal of the short-circuit isolator and the trigger module, respectively; The second switch module is electrically connected to the negative output terminal of the short-circuit isolator, the first switch module, and the trigger module, respectively.

3. A bus short-circuit isolation circuit according to claim 2, characterized in that, The second switching module includes a second NMOS transistor, a fifth diode, a sixth diode, a second fast recovery diode, and a first resistor; The drain of the second NMOS transistor is electrically connected to the negative output terminal of the short-circuit isolator, the anode of the first diode, the first terminal of the second fast recovery diode, and the cathode of the fifth diode, respectively. The gate of the second NMOS transistor is electrically connected to the cathode of the sixth diode, the first terminal of the first resistor, the first switching module, and the trigger module, respectively. The source of the second NMOS transistor and the anode of the fifth diode are grounded. The anode of the sixth diode and the second terminal of the first resistor are grounded. The second terminal of the second fast recovery diode is electrically connected to the negative input terminal of the short-circuit isolator. The second NMOS transistor is used to disconnect the negative output terminal of the short-circuit isolator when a short circuit occurs, and to restore the negative output terminal of the short-circuit isolator when the short circuit is released.

4. A bus short-circuit isolation circuit according to claim 1, characterized in that, The first switching module also includes a second resistor, a third resistor, and a first capacitor; The first end of the second resistor, the first end of the third resistor, the first end of the first capacitor, and the trigger module are all electrically connected to the third end of the first fast recovery diode. The second end of the second resistor is electrically connected to the cathode of the first diode and the low-voltage detection module, respectively. The second end of the third resistor is electrically connected to the second end of the first capacitor, the second switching module, the gate of the first NMOS, and the first end of the first fast recovery diode, respectively.

5. A bus short-circuit isolation circuit according to claim 1, characterized in that, The low-voltage detection module also includes a sixth resistor, a seventh resistor, an eighth resistor, and a second capacitor; The first end of the sixth resistor is electrically connected to the emitter of the first PNP transistor, the second end of the sixth resistor is electrically connected to the drain of the third NMOS transistor, the first end of the seventh resistor is electrically connected to the collector of the first PNP transistor, the second end of the seventh resistor is electrically connected to the gate of the third NMOS transistor, the first end of the eighth resistor and the first end of the second capacitor, and the second end of the eighth resistor and the second end of the second capacitor are grounded.

6. A bus short-circuit isolation circuit according to claim 1, characterized in that, The triggering module includes a second PNP transistor, a third fast recovery diode, and a fourth NMOS transistor; The emitter of the second PNP transistor is electrically connected to the switch control module, the collector of the second PNP transistor is electrically connected to the first terminal of the third fast recovery diode, the second terminal of the third fast recovery diode is electrically connected to the low-voltage detection module, the collector of the second PNP transistor and the third terminal of the third fast recovery diode are grounded, the gate of the fourth NMOS transistor is electrically connected to the third terminal of the third fast recovery diode, the drain of the fourth NMOS transistor is electrically connected to the switch control module, and the source of the fourth NMOS transistor is grounded.

7. A bus short-circuit isolation circuit according to claim 6, characterized in that, The trigger module also includes an eighth diode, a ninth diode, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a third capacitor, a fourth capacitor, a fifth capacitor, and a sixth capacitor; The first terminal of the third capacitor and the first terminal of the fourth capacitor are electrically connected to the emitter of the second PNP transistor. The second terminal of the third capacitor and the second terminal of the fourth capacitor are grounded. The anode of the eighth diode is electrically connected to the first terminal of the ninth resistor. The second terminal of the ninth resistor, the first terminal of the tenth resistor, and the first terminal of the fifth capacitor are grounded. The cathode of the eighth diode is electrically connected to the base of the second PNP transistor. The second terminal of the tenth resistor is electrically connected to the collector of the second PNP transistor and the first terminal of the eleventh resistor. The second terminal of the eleventh resistor is electrically connected to the first terminal of the third fast recovery diode. The second terminal of the fifth capacitor is electrically connected to the third terminal of the third fast recovery diode, the first terminal of the twelfth resistor, and the first terminal of the sixth capacitor. The second terminal of the twelfth resistor is electrically connected to the second terminal of the sixth capacitor, the cathode of the ninth diode, the first terminal of the thirteenth resistor, and the gate of the fourth NMOS transistor. The anode of the ninth diode and the second terminal of the thirteenth resistor are grounded.

8. A fire alarm system, characterized in that, The invention includes a bus short-circuit isolation circuit as described in any one of claims 1-7, wherein the bus short-circuit isolation circuit is used to protect a fire-fighting device on the fire-fighting bus, and each fire-fighting device is connected to the fire-fighting bus by either having the bus short-circuit isolation circuit installed inside its base or by having the bus short-circuit isolation circuit built into it.

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