Two-bus short circuit isolation circuit based on MOS tube
By using a MOSFET-based two-bus short-circuit isolation circuit, and leveraging the linkage of relays, resettable fuses, LEDs, and phototransistors, automatic isolation and recovery of two-bus short circuits are achieved. This solves the problems of overheating from resettable fuses and external power supply, simplifies the circuit structure, and saves costs.
Patent Information
- Application Number
- CN202422473733.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-11-04
- Estimated Expiration
- 2034-10-14
AI Technical Summary
Existing two-bus short-circuit isolation methods suffer from problems such as heat generation and energy consumption of self-resetting fuses, inability to automatically recover, and increased costs. Furthermore, traditional MOSFET methods require an external power supply, which increases complexity and cost.
A two-bus short-circuit isolation circuit based on MOSFETs is adopted, combined with the linkage of relays, self-resetting fuses, light-emitting diodes and phototransistors. The fast conduction function of MOSFETs is used to realize automatic fault recovery. Through the cooperation of isolation control circuit and self-resetting control circuit, automatic isolation and recovery of short-circuit faults are realized.
It effectively avoids energy loss caused by the overheating of self-resetting fuses, realizes automatic recovery of short-circuit faults, simplifies circuit structure, and saves costs.
Smart Images
Figure CN223514592U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electrical automatic control, specifically a two-bus short-circuit isolation circuit based on MOSFETs. Background Technology
[0002] Two-wire bus is a technology that combines power and signal lines into one, compared to a four-wire system (two power lines and two communication lines), allowing both signals and power to share a single bus. Two-wire bus reduces construction and cabling costs, greatly simplifying on-site installation and subsequent maintenance. It is widely used in fire protection, instrumentation, sensors, and industrial control. The bus system can operate stably with 256 nodes over a distance of 2km. In such systems, it is difficult to pinpoint the location of a short circuit; and a single fault can disable the entire bus. Using a bus isolator isolates the short-circuited section from the main bus, making it easier to locate the fault and ensuring the normal operation of other bus sections.
[0003] Currently, two-wire short-circuit isolation methods include the branch-series self-resetting fuse method and methods that utilize the switching function of MOSFETs to quickly disconnect short-circuited branches. The branch-series self-resetting fuse method mainly utilizes the characteristics of the self-resetting fuse resistor: when the current is small, the fuse resistance is small, and the line operates normally; when the short-circuit current suddenly increases, the resistance increases rapidly, limiting the short-circuit current to a very small range, effectively disconnecting it and ensuring normal bus operation. When the short-circuit fault is eliminated and the line current decreases, the self-resetting fuse resistance returns to its normal value, and the line operates normally. Its advantages are ease of implementation, low cost, and automatic recovery when the fault is eliminated. The disadvantage is that when the line is short-circuited, the self-resetting fuse resistor is very large, which generates heat and consumes bus power, reducing the bus's load capacity and potentially causing unstable operation of downstream devices. The method of quickly cutting off short-circuit branches using the switching function of MOSFETs works by using a detection circuit to detect whether a line is short-circuited. Once a short circuit occurs, the gate voltage in the MOSFET drive circuit becomes zero, thereby turning off the MOSFET and cutting off the short-circuit line, ensuring normal bus operation. Its advantages are speed and the ability to completely cut off short-circuit lines without affecting other lines. The disadvantages are that power cannot be automatically restored when the fault is cleared. Since the bus length reaches 2 kilometers and the environment is complex, short circuits are more likely to occur due to factors such as humidity. The inability to automatically restore power after fault clearance brings inconvenience to system maintenance. In addition, most methods of cutting off short-circuit lines using MOSFETs require an external power supply to power the MOSFETs, increasing additional costs. Utility Model Content
[0004] The technical problem to be solved by this utility model is to provide a two-bus short-circuit isolation circuit based on MOSFETs, which can effectively solve the problems mentioned in the background art.
[0005] To solve the above problems, the technical solution adopted by this utility model is: a two-bus short-circuit isolation circuit based on a MOSFET, including a main circuit, an isolation control circuit, and a self-resetting control circuit. The main circuit includes 24V non-polar bus input terminals Z1 and Z2, output terminals zo1 and zo2, a Zener diode D3, and normally open (NO) and normally closed (NC) contacts of a relay K connected in series on the bus. The normally closed (NC) contact of the relay K is connected in series with a self-resetting fuse F1, and the normally open (NO) contact of the relay K is connected in series with the self-resetting control circuit. The current forms a loop through Z1-zo1-zo2-F1-NC-Z2. The isolation control circuit is connected in parallel to one end of the normally closed (NC) contact and the self-resetting fuse F1. The two ends of the self-resetting control circuit are connected across the two ends of the main circuit output bus via the normally open (NO) contact of the relay K.
[0006] As a further preferred embodiment of this utility model, the isolation control circuit includes a rectifier bridge D1, a filter capacitor C2, a current-limiting resistor R3, a current-limiting resistor R4, a light-emitting diode (LED), a phototransistor X1, a MOSFET Q1, and a relay coil KM. The input terminal of the rectifier bridge D1 is connected to the 24V non-polarized bus of the main circuit and outputs DC power after rectification. The filter capacitor C2 is connected to the output terminal of the rectifier bridge D1 to filter the DC power. The current-limiting resistor R3 is connected to the output terminal of the rectifier bridge D1 and is connected in series with the LED. The current-limiting resistor R4 is connected to the output terminal of the rectifier bridge D1. The emitter of the phototransistor X1 is connected to the current-limiting resistor R4, and the base is connected to the other end of the LED. The source of the MOSFET Q1 is connected to GND, the drain is connected to the negative terminal of the relay coil KM, and the gate is connected to the output terminal of the phototransistor X1. The other end of the relay coil KM is connected to the output terminal of the current-limiting resistor R4.
[0007] As a further preferred embodiment of this utility model, the self-recovery control circuit includes a rectifier bridge D2, a filter capacitor C1, a Zener diode D4, a current-limiting resistor R2, and a photodiode X1; the input terminal of the rectifier bridge D2 is connected to the normally open contact NO of the relay K in the main circuit; the filter capacitor C1 is connected to the output terminal of the rectifier bridge D2; the Zener diode D4 is connected to the output terminal of the rectifier bridge D2; the current-limiting resistor R2 is connected to the output terminal of the rectifier bridge D2, and the current-limiting resistor R2 is connected in series with the photodiode X1.
[0008] Compared with the prior art, this utility model provides a two-bus short-circuit isolation circuit based on MOSFETs, which has the following advantages:
[0009] 1. By isolating the short-circuited load circuit from the system through relays, compared with the traditional self-resetting fuse isolation method, the energy loss caused by the heat generated by the self-resetting fuse is avoided;
[0010] Second, by utilizing the linkage between light-emitting diodes and phototransistors and the fast conduction function of MOSFETs, the system automatically recovers after a short-circuit fault is eliminated.
[0011] Third, it makes full use of the 24V bus voltage, avoiding the need for an external power supply, simplifying the circuit and saving costs. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of the circuit principle of this utility model;
[0013] Figure 2 This is a schematic diagram of the main circuit principle of this utility model;
[0014] Figure 3 This is a schematic diagram of the isolation control circuit of this utility model;
[0015] Figure 4 This is a schematic diagram of the self-recovery control circuit of this utility model; Detailed Implementation
[0016] It should be noted that if the embodiments of this utility model involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a specific posture. If the specific posture changes, the directional indicators will also change accordingly.
[0017] This embodiment is based on what can be achieved by those skilled in the art. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that such combination of technical solutions does not exist and is not within the protection scope of this utility model.
[0018] Reference Figure 1-4 This utility model provides a two-bus short-circuit isolation circuit based on MOSFETs, comprising three parts: a main circuit, an isolation control circuit, and a self-recovery control circuit. The main circuit includes 24V non-polar bus input terminals Z1 and Z2, output terminals zo1 and zo2, a Zener diode D3, and normally open (NO) and normally closed (NC) contacts of a relay K connected in series on the bus.
[0019] The main circuit is as follows Figure 2As shown, Z1 and Z2 are input terminals connected to the system bus, and zo1 and zo2 are output terminals that can be connected to loads such as smoke detectors. The normally closed contact NC of relay K is connected in series with the self-resetting fuse F1, and the normally open contact NO is connected in series with the self-resetting control circuit. During normal operation, the relay coil KM is not energized, the normally closed contact NC is in the closed state, the self-resetting fuse F1 has a very small resistance and remains unobstructed, and the current forms a loop through Z1-zo1-zo2-F1-NC-Z2, and the load operates normally. The isolation control circuit connected in parallel across NC and F1 has zero voltage across it and does not operate. Since the normally open contact is in the open state, the self-resetting control circuit connected in series at the NO terminal also does not operate, and the system operates normally.
[0020] As a further preferred embodiment of this utility model, the isolation control circuit includes a rectifier bridge D1, a filter capacitor C2, a current limiting resistor R3, R4, a light-emitting diode LED, a phototransistor X1, a MOSFET Q1, and a relay coil KM;
[0021] The isolation control circuit is as follows Figure 3 As shown, the rectifier bridge D1 rectifies the 24V non-polarized current on the bus into DC current, which is then filtered by capacitor C1 and used as power for the circuit, thus eliminating the need for an external power supply. The energization and de-energization of the relay coil KM control the opening and closing of the normally open (NO) and normally closed (NC) contacts, thereby controlling whether the self-resetting fuse F1 in the main circuit is isolated and the on / off state of the self-resetting control circuit. The phototransistor X1 and MOSFET Q2 de-energize the relay coil KM when the short-circuit fault is cleared. The LED serves as a fault indicator. When a load connected to the output terminals zo1 and zo2 experiences a short circuit, the current on the main circuit bus increases rapidly, and the self-resetting fuse F1 also increases rapidly, effectively breaking the circuit and isolating the short-circuit. Because the resistance of F1 is very high at this time, F1 will generate heat and consume bus power, causing the downstream load to operate unstablely due to insufficient power. Therefore, F1 needs to be disconnected. As mentioned earlier, when the load is short-circuited, the resistance of F1 is very large, which is equivalent to an open circuit. The two ends of the control isolation circuit are equivalent to being connected to the two ends of the system bus Z1 and Z2, which powers on the isolation control circuit, energizes the coil KM, and opens the normally closed contact NC of the relay connected in series in the main circuit, completely isolating the short-circuit loop. The self-resetting fuse is also disconnected and no longer generates heat. The two ends of the self-resetting control circuit are connected to the two ends of the load. Since the load is short-circuited, the voltage across the two ends is zero, and the self-resetting control circuit does not operate.
[0022] As a further preferred embodiment of this utility model, the self-recovery control circuit includes a rectifier bridge D2, a filter capacitor C1, a Zener diode D4, a current-limiting resistor R2, and a photodiode X1.
[0023] The self-recovery control circuit is as follows: Figure 4As shown, the two ends of the circuit are connected across the output main circuit bus via the normally open contact NO of relay K. The rectifier bridge D2 and filter capacitor C1 operate on the same principle as the aforementioned isolation control circuit and will not be described again. Zener diode D4 acts as a voltage regulator, ensuring voltage stability, and together with current-limiting resistor R2, provides a stable operating current for the LED.
[0024] The light-emitting diode (LED) controls the switching on and off of the phototransistor X1 in the isolation control circuit. When the load short-circuit fault is cleared, the bus output terminals zo1 and zo2 are turned on. Since the normally open contact NO of relay K is closed, the self-resetting control circuit connected in parallel with the load will conduct due to the voltage difference. The voltage across the circuit is rectified by the electrolytic capacitor D2, filtered by the filter capacitor C1, regulated by the Zener diode D4, and current-limiting by the current-limiting resistor R2, providing a stable current to the LED, causing it to conduct and emit light. The LED's illumination turns on the phototransistor X1 in the isolation control circuit. Because the emitter of phototransistor X1 is connected to the gate of MOSFET Q1... When connected, the phototransistor X1 conducts, causing the drain and source of the MOSFET Q1 to conduct. After the MOSFET conducts, its resistance is very small, which is equivalent to a short circuit. This causes the voltage across the relay coil KM, which is connected in parallel across the drain and source of the MOSFET, to drop rapidly. The normally closed contact NC of the relay coil KM is de-energized and closes. The voltage across the isolation circuit connected in parallel across the normally closed contact NC is zero, and the isolation circuit is de-energized and stops working. The fault indicator LED goes out, and the normally open contact NO also opens. The self-recovery control circuit connected in series on the side of the normally open contact NO also disconnects and stops working. The entire system returns to normal operating mode.
[0025] As a specific embodiment of this utility model: Under normal operating conditions, the bus input terminal Z2 is connected to the output terminal Z02 via the normally closed contact NC of the relay and the resettable fuse F1. The bus output terminals Z01 and Z02 are connected to the bus Z1, forming a closed loop, and the load operates normally. Because the isolation circuit is connected in parallel between the normally closed contact NC of the relay and the resettable fuse, there is no voltage at these two points during normal operation, and the circuit is not conductive. The resettable control circuit is connected between the normally open contact NO and the other two ends of the bus. Because the normally open contact NO is open, the circuit is also not conductive. When a short circuit occurs in the load, the current flowing through the resettable fuse F1 increases rapidly, causing F1 to open. At this time, the isolation circuit conducts, the relay coil KM connected in series in the isolation circuit is energized, the normally closed contact NC opens, disconnecting the resettable fuse F1 from the main circuit bus and isolating the short circuit. The normally open contact NO connected in series in the resettable control circuit closes, but because the output pin is short-circuited, there is no voltage at the two ends of the resettable control circuit, and it is not conductive. When the short-circuit fault is cleared, the self-resetting control circuit connected across the load is turned on due to the voltage difference. The photodiode X1 connected in series in the circuit emits light, causing the phototransistor X1 in the isolation circuit to conduct. Since the emitter of the phototransistor X1 is connected to the gate of the MOSFET Q1, the MOSFET Q1 is saturated and turned on, quickly making the voltage of the relay coil KM zero. The normally closed contact NC changes from open to closed, the self-resetting fuse F1 is turned on, and the isolation control circuit loses power and stops working. At the same time, the normally open contact NO changes from closed to open, the self-resetting control circuit is de-energized and stops working, and the system returns to normal working state.
[0026] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. All equivalent structural transformations made under the inventive concept of the present utility model using the contents of the present utility model specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present utility model.
Claims
1. A dual-bus short-circuit isolation circuit based on a MOSFET, characterized in that, The circuit includes a main circuit, an isolation control circuit, and a self-resetting control circuit. The main circuit includes 24V non-polar bus input terminals Z1 and Z2, output terminals zo1 and zo2, a Zener diode D3, and normally open (NO) and normally closed (NC) contacts of a relay K connected in series on the bus. A self-resetting fuse F1 is connected in series with the normally closed (NC) contact of the relay K, and the normally open (NO) contact of the relay K is connected in series with the self-resetting control circuit. The current forms a loop through Z1-zo1-zo2-F1-NC-Z2. The isolation control circuit is connected in parallel to one end of the normally closed (NC) contact and the self-resetting fuse F1. The two ends of the self-resetting control circuit are connected across the two ends of the main circuit output bus via the normally open (NO) contact of the relay K.
2. The dual-bus short-circuit isolation circuit based on MOS transistors according to claim 1, characterized in that, The isolation control circuit includes a rectifier bridge D1, a filter capacitor C2, a current-limiting resistor R3, a current-limiting resistor R4, a light-emitting diode (LED), a phototransistor X1, a MOSFET Q1, and a relay coil KM. The input terminal of the rectifier bridge D1 is connected to the 24V non-polarized bus of the main circuit and outputs DC power after rectification. The filter capacitor C2 is connected to the output terminal of the rectifier bridge D1 to filter the DC power. The current-limiting resistor R3 is connected to the output terminal of the rectifier bridge D1 and is connected in series with the LED. The current-limiting resistor R4 is connected to the output terminal of the rectifier bridge D1. The emitter of the phototransistor X1 is connected to the current-limiting resistor R4, and the base is connected to the other end of the LED. The source of the MOSFET Q1 is connected to GND, the drain is connected to the negative terminal of the relay coil KM, and the gate is connected to the output terminal of the phototransistor X1. The other end of the relay coil KM is connected to the output terminal of the current-limiting resistor R4.
3. The dual-bus short-circuit isolation circuit based on MOS transistors according to claim 1 or 2, characterized in that, The self-recovery control circuit includes a rectifier bridge D2, a filter capacitor C1, a Zener diode D4, a current-limiting resistor R2, and a photodiode X1. The input terminal of the rectifier bridge D2 is connected to the normally open contact NO of the relay K in the main circuit. The filter capacitor C1 is connected to the output terminal of the rectifier bridge D2. The Zener diode D4 is connected to the output terminal of the rectifier bridge D2. The current-limiting resistor R2 is connected to the output terminal of the rectifier bridge D2, and the current-limiting resistor R2 is connected in series with the photodiode X1.