CN102509471B - Light-emitting diode (LED) traffic light failure monitoring system and method - Google Patents

Abstract

The present invention provides a LED traffic signal light fault monitoring system and method, including an AC power supply and detection unit arranged inside the traffic signal machine, an LED lamp group current detection module, an AC power on-off control module and a continuous flow element. The working current of the LED signal lamp is detected by the LED lamp group current detection module. When the working current of the LED signal lamp is lower than the normal working threshold, the AC on-off control module disconnects the AC loop, and the AC power supply and detection unit cannot detect the AC current, and judges the LED signal lamp Fault. The LED traffic signal lamp fault monitoring system and method of the present invention can obtain reliable fault detection results without changing the circuit structure of the traffic signal machine in the prior art.

Description

LED traffic signal lamp failure monitoring system and method

technical field

The invention relates to the technical field of traffic control, in particular to a LED traffic signal lamp failure monitoring system and method.

Background technique

Traffic signal lights are an important part of traffic signal command and the basic language of road traffic. They are widely used in road intersections, curves, bridges and other dangerous road sections with potential safety hazards to direct drivers or pedestrians to promote smooth traffic and avoid traffic. Accidents and accidents happen. It is one of the important components of the modern urban traffic system to control the traffic signal lights to carry out marking and color changes according to certain rules, so as to realize the control and management of urban road traffic signals.

The traditional traffic lights are generally incandescent lamps, and the filaments of incandescent lamps have a short lifespan, and failures often occur. Therefore, a fault monitoring circuit must be installed inside the traffic signal machine. Figure 1 shows the principle diagram of the incandescent signal lamp failure detection circuit in the prior art, as shown in the figure: the power supply of the incandescent signal lamp is supplied by the AC power provided inside the traffic signal machine and the 220V AC power provided by the detection unit is passed through the transformer It is composed of a DC power generating circuit, and the DC power generated by the DC power generating circuit provides working voltage for the incandescent traffic signal lamp. The AC power supply and detection unit forms an AC loop with the primary winding of the transformer, while the incandescent traffic signal light as a load forms a DC loop with the DC power generation circuit. When the incandescent traffic signal lamp works normally, a certain amount of current passes through the incandescent traffic signal lamp. At this time, the secondary winding of the transformer must pass through a certain amount of alternating current. According to the working principle of the transformer, the corresponding in the primary winding of the transformer will be There is an alternating current passing through, that is, there is an alternating current in the alternating current circuit. After the alternating current power supply and detection unit detects the alternating current, it can judge that the incandescent traffic signal lamp is working normally. When the incandescent lamp fails, the filament is broken, no current flows in the DC circuit, and there is no AC current in the corresponding AC circuit. If the AC power supply and detection unit cannot detect the AC current, it can be judged that the incandescent traffic signal lamp is faulty. To sum up, it is judged whether the incandescent traffic signal lamp is faulty or not according to the alternating current power supply and whether the detection unit detects the alternating current.

Due to the continuous improvement of the living standards of human society, the demand for energy is also increasing, and the problem of energy shortage is becoming more and more obvious. With the shortage of natural resources such as oil and coal in various countries, most of the The region has also taken various measures to deal with power shortages. In this case, due to the great advantages of LED lights in energy saving and environmental protection, the traffic lights in many cities have also been replaced by LED signal lights from the original incandescent traffic lights to save energy. Due to the many differences in physical structure and working characteristics between LED signal lights and incandescent traffic lights, it is reasonable to replace traffic lights with the replacement of traffic lights to ensure the reliability of traffic light control and fault monitoring. However, if it is a huge project to replace all the traffic signals, it will inevitably increase the cost, and the replaced traffic signals cannot continue to be used, causing waste. Therefore, in order to save costs, most cities continue to use the existing traffic signals. A method for controlling a signal lamp and detecting a signal lamp fault in the prior art.

Inside the LED signal lamp is an LED lamp group formed by a plurality of LED lamps connected in series/parallel, and the traffic signal machine in the prior art can realize accurate control of the LED signal lamp. However, the reliability of fault detection of LED signal lamps by traffic signal machines in the prior art is relatively poor. Because for pedestrians or drivers on the road, when 20% of the signal lights in the LED signal lights can emit light normally, due to the influence of sunlight or street lights, people can no longer visually identify whether the LED lights are normally illuminated, and as a It is common knowledge that when an LED lamp fails, only its internal resistance becomes very large, but it is not completely disconnected. Therefore, when 80% of the LED lamps inside the LED signal lamp fail, its LED signal lamp only has a large resistance. , but it does not guarantee that the DC circuit is completely disconnected, even when all the LED lights inside the LED signal lamp cannot emit light normally, the DC circuit is still in a connected state. According to the working principle of the transformer, the AC power supply and detection unit can still detect the AC current, and at this time it will not determine the failure of the LED signal light. Therefore, when the LED signal lamp has broken down, and pedestrians and drivers can no longer distinguish whether the LED signal lamp is emitting light, the existing fault monitoring method cannot make accurate judgments, which brings potential safety hazards to road traffic.

In order to solve the above problems, the existing patent document CN2783697Y discloses a control circuit for LED light source color lamp signal machine, which includes a city source transformer, a JZXC-H18 type filament relay, a lighting unit and a fault detection unit; the lighting unit consists of a lighting Transformer, bridge rectifier current, filter capacitor, threshold relay and light source conversion relay, the city source transformer output 72V voltage terminal is connected in series with the JZXC-H18 filament relay and connected to the input terminal of the lighting transformer, and the output terminal of the lighting transformer is connected to the bridge rectifier circuit , forming the DC power supply of the LED light source; the filter capacitor is connected to the DC power supply in parallel; the normally closed and normally open contacts of the light source conversion relay are respectively connected to the main LED light source and the auxiliary light source, and a photosensitive resistor is installed next to the main LED light source, consisting of a photosensitive resistor and a voltage dividing resistor The voltage divider circuit is connected to the control pole of the thyristor diode to form a fault detection unit; another group of normally open contacts of the light source conversion relay outputs a fault alarm signal; the threshold relay is connected to the circuit before the LED light source; although the above technical scheme There is no need to replace the signal interlock circuit, which can ensure the normal operation of the interlock circuit, but the above-mentioned technical solution also has the following problems:

①In the above technical scheme, it is necessary to install a photoresistor inside each LED signal lamp, and the internal space of the LED signal lamp is limited, so it is difficult to install a photoresistor inside it, especially to set a photoresistor for each LED lamp. It will inevitably increase the complexity of the process and increase the cost. In addition, if each LED lamp is equipped with a photoresistor, the subsequent processing circuit for the electrical signal output by the photoresistor is very complicated and difficult to implement. larger.

②In the above technical solution, it is impossible to directly adapt the traffic signal machine in the prior art to the fault detection unit, and it is necessary to transform the existing traffic signal machine into the LED light source signal machine in the above technical solution. The structural changes of traffic signals are small, and the cost has been reduced compared to the replacement of traffic signals. However, the number of traffic signals in each city is large, and it is a huge project to transform all traffic signals, which is time-consuming and labor-intensive.

Contents of the invention

The technical problem to be solved by the present invention is that in the prior art, under the premise of not replacing the traffic signal machine, the fault detection circuit for detecting the failure of the incandescent lamp is used to detect the failure of the LED signal lamp with low reliability, and the use of photoresistors cannot satisfy the internal limitation of the LED signal lamp. The reasonable layout of the space increases the complexity of the processing and production of LED signal lamps, leading to an increase in cost, and then provides a LED signal lamp fault detection circuit with simple circuit that can accurately detect the LED lamp faults in the LED lamp group.

In order to solve the above technical problems, the present invention provides a fault monitoring system for LED traffic lights, which includes an AC power supply and detection unit installed inside the traffic signal, and also includes: an LED lamp group current detection module installed outside the traffic signal, an AC Electric on-off control module and freewheeling element;

The LED lamp group current detection module is used to detect the magnitude of the LED lamp group current, and when the value of the LED lamp group current is less than the LED signal lamp operating current threshold, send a signal to the AC on-off control module to control the AC The electric on-off control module disconnects the AC loop;

The AC power on-off control module is connected between the AC power supply and the primary winding; when the AC power on-off control module is connected to the AC loop, the AC power supply is connected to the primary winding, and the AC power When the on-off control module disconnects the AC loop, the AC power supply is disconnected from the primary winding, and the charged freewheeling element is connected to the AC on-off control module;

The freewheeling element has the function of charging and discharging, and is connected to the DC power generation circuit through the AC on-off control module. When the AC on-off control module is connected to the AC circuit, the DC power generation circuit charges the freewheeling element.

The LED lamp group current detection module includes:

Current sampling resistor: connected between the output terminal of the LED lamp group and the ground signal, the voltage drop U1 across the current sampling resistor is proportional to the current of the LED lamp group, when the current of the LED lamp group is equal to the LED signal lamp When the working current threshold is reached, the voltage drop across the current sampling resistor is U0;

Control circuit: real-time detection of the voltage value U1 at both ends of the current sampling resistor and comparison of the relationship between U1 and U0. When U1<U0, the control circuit outputs a "1" control signal, which means that the LED signal light is faulty.

The control circuit adopts an MPU (Micro Processor Unit) controller with an analog-to-digital converter.

The AC on-off control module includes an electric control switch, a relay and a load resistor;

The electric control switch is connected between the relay and the output terminal of the control circuit, when the control circuit outputs a "1" control signal, the electric control switch is closed and turned on, and the relay disconnects the AC circuit;

The relay can simultaneously switch AC 220v and DC 12v, its normally closed contact III is connected to an output end of the AC power supply, the common contact II of the relay is connected to an input end of the primary winding, and the DC The power generating circuit is connected with the freewheeling element through the normally closed contact VI, and when the public contact II of the relay is closed with the normally closed contact III, the public contact VII is closed with the normally closed contact VI, The AC circuit is in a connected state while the freewheeling element is in a charging state;

The normally open contact V of the relay is connected to the electric control switch through the load resistance, and when the common contact VII of the relay is connected to the normally open contact V, the AC circuit is disconnected, and the charging is completed. The freewheeling element provides conduction voltage for the electronically controlled switch through the load resistor.

The electric control switch adopts a Darlington triode, and the connection relationship of the Darlington in the system is: the base is connected to the output terminal of the control circuit, the collector is connected to the normally closed contact I of the relay, and the emitter Connect to ground signal.

The freewheeling element adopts a 4700uF freewheeling capacitor, one end of the freewheeling capacitor is connected to the ground signal, and the other end is connected to the common contact VII and the normally closed contact VIII of the relay.

The operating current threshold of the LED signal lamp is selected as one-half of the current of the LED lamp group when all the LED lamps in the LED lamp group are working normally.

The present invention also provides a LED traffic signal lamp fault detection method, comprising the following steps:

① The AC on-off control module is connected to the AC circuit, and the freewheeling element is charged;

② After the freewheeling element is charged, the LED lamp group current detection module starts to detect the LED lamp group current in real time, and the AC power supply and detection unit detects the AC current in the AC circuit;

③ When the current of the LED lamp group is greater than or equal to the working current threshold of the LED signal lamp, the AC on-off control module remains connected, the AC current detected by the AC power supply and detection unit is not zero, and it is judged that the LED signal lamp is working normally;

When the value of the current of the LED lamp group is less than the operating current threshold of the LED signal lamp, the current detection module of the LED lamp group controls the switching off of the AC on-off control module, and the fully charged freewheeling element provides work for the AC on-off control module voltage, the AC current detected by the AC power supply and detection unit is zero, and it is judged that the LED signal light is faulty.

In the step ②, when the AC on-off control module is connected, the change of the current of the LED lamp group is converted into the change of the voltage drop across the current sampling resistor by using the current sampling resistor, and the control circuit is used to detect the change of the current sampling resistor The voltage drop U1 at both ends; the control circuit stores the voltage drop U0 at both ends of the current sampling resistor when the current of the LED lamp group is equal to the working current threshold of the LED signal lamp;

In the step ③, the control circuit compares the relationship between U1 and U0, and when U1<U0, the control circuit outputs a "1" control signal to the AC on-off control module, and the AC on-off control If the AC circuit of the module control is disconnected, the AC power supply and detection unit cannot detect the AC current, and the LED signal lamp is judged to be faulty.

In the step ③, an MPU controller with an analog-to-digital converter is used as the control circuit.

In the step ③, the AC on-off control module uses a relay that can simultaneously switch between AC 220v and DC 12v to control whether the AC circuit is connected and the relay is connected in series with an electric control switch, and the relay is disconnected when the electric control switch is turned on AC circuit, when the electric control switch is turned off, the relay is connected to the AC circuit;

The control circuit compares the relationship between U1 and U0, and when U1<U0, the control circuit outputs a "1" control signal to the electric control switch, the electric control switch is closed and conducting, and the relay disconnects the AC circuit , the charged freewheeling capacitor is used as a power supply to provide the working voltage for the relay and the conduction voltage of the electric control switch, the AC power supply and detection unit cannot detect the AC current, and judges that the LED signal light is faulty.

In the step ①, a 4700uF freewheeling capacitor is selected as the freewheeling element.

In the step ③, the operating current threshold of the LED signal lamp is selected as half of the current of the LED lamp group when all the LED lamps in the LED lamp group are working normally.

Compared with the prior art, the technical solution of the present invention has the following advantages:

①In the LED fault detection system and detection method of the present invention, the LED lamp group current detection module is used to detect the output current of the LED signal lamp, and when the circuit current of the LED signal lamp lamp group is less than the normal operating current threshold of the LED, the AC on-off control module is used The control AC circuit is disconnected. After the AC circuit is disconnected, the AC power supply and detection unit cannot detect the AC signal, and judge the LED signal lamp to be faulty. Therefore, on the premise of not changing the existing traffic signal machine, the method of controlling the connection or disconnection of the AC circuit in the prior art can be used to detect whether the LED signal lamp is faulty, which effectively solves the problem of the AC power supply and detection unit when the LED signal lamp is faulty. Problems with alternating current can also be detected.

②The current detection module of the LED lamp group in the present invention includes a current sampling resistor, the purpose is to convert the change of the current of the LED lamp group into the change of the voltage at both ends of the current sampling resistor, which can effectively avoid the problem caused by the small change in the current of the LED lamp group. Inaccurate detection results; at the same time, the control circuit in the LED lamp group current detection module can choose an MPU controller with an analog-to-digital converter, which is low in cost and powerful in function, and its programmable implementation is easy to upgrade and control parameters.

③In the present invention, the AC on-off control module uses a relay as the main component. Since the relay adopts the model of switching AC 220v and DC 12v at the same time, the switching current is 2A, because when the disc is full of lights, the maximum brightness of the LED lamp group needs 12v more. , 1.2A, converted to AC 220v is less than 100mmA, so the switching current of the selected relay is much larger than the current required by the LED signal lamp.

④ In the present invention, the Darlington triode is selected as the electric control switch, and the use of the Darlington triode to drive the relay can effectively reduce the power loss of the relay for the voltage.

⑤ In the present invention, the freewheeling element adopts a 4700uF freewheeling capacitor, which can maintain the system power off for 4-5s. If you choose the traffic signal machine of the MPU controller, the time required to detect a power failure should be much less than 1s, and maintaining the system power failure for 4-5s is to prepare for the possible differences in different types of traffic signals, so for different types The fault detection system and detection method of the present invention can accurately detect the faults of LED signal lamps for traffic signal machines of different types.

Description of drawings

In order to make the content of the present invention more easily understood, the present invention will be described in further detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

1 is a schematic diagram of a fault detection circuit for an incandescent signal lamp in the prior art;

Fig. 2 is a block diagram of the LED signal lamp failure detection system of the present invention;

Figure 3 is a schematic diagram of the LED signal lamp failure detection circuit when the LED signal lamp is working normally;

Fig. 4 is a schematic diagram of the LED signal lamp failure detection circuit when the LED signal lamp fails;

5 is a circuit schematic diagram of the LED lamp group current detection module according to the present invention;

Detailed ways

Example 1

This embodiment provides a LED signal lamp failure monitoring system, as shown in Figure 2, including an AC power supply and detection unit arranged inside the traffic signal machine, and also includes: LED lamp group current detection module, AC power on-off control module and continuation flow element;

The LED lamp group current detection module is used to detect the magnitude of the LED lamp group current, and when the value of the LED lamp group current is less than the LED signal lamp operating current threshold, send a signal to the AC on-off control module to control the AC The power on-off control module disconnects the AC loop; as shown in Figure 3, the LED lamp group current detection module includes: a current sampling resistor RS: connected between the output terminal of the LED lamp group and the ground signal, the current The voltage drop _U1 across the sampling resistor RS is proportional to the current of the LED lamp group, when the current of the LED lamp group is equal to the operating current threshold of the LED signal lamp, the voltage drop across the current sampling resistor RS is _U0 ; the control circuit : Real-time detection of the voltage value _U1 at both ends of the current sampling resistor RS and comparing the relationship between _U1 and _U0 , when _U1 < _U0 , the control circuit outputs a "1" control signal, that is, the LED signal lamp is faulty; In the actual application process, the size of RS can be selected according to the actual situation, but excessive resistance of RS should be avoided to cause unnecessary power loss to the system. As a preferred embodiment, the control circuit adopts an MPU (Micro Processor Unit) controller with an analog-to-digital converter, more preferably PIC series 8-bit 12F629 or similar MPU controller or comparator can be selected, which The feature is that it does not need peripheral circuit support such as crystal oscillator and reset circuit.

The AC power on-off control module is connected between the AC power supply and the primary winding; when the AC power on-off control module is connected to the AC loop, the AC power supply is connected to the primary winding, and the AC power supply is connected to the primary winding. When the power on-off control module disconnects the AC loop, the AC power supply is disconnected from the primary winding, and the charged freewheeling element is connected to the AC on-off control module;

In this embodiment, the AC on-off control module includes an electric control switch, a relay and a load resistor;

The electronically controlled switch is connected between the relay and the output terminal of the control circuit, when the control circuit outputs a "1" control signal, the electronically controlled switch is closed and turned on, and the relay disconnects the AC circuit; as a preferred In the embodiment, the Darlington triode is selected as the electronically controlled switch, which can effectively reduce the power loss of the relay.

The relay can simultaneously switch AC 220v and DC 12v, its normally closed contact III is connected to an output end of the AC power supply, the common contact II of the relay is connected to an input end of the primary winding, and the DC The power generation circuit is connected to the freewheeling element through the normally closed contact VI;

As shown in Figure 4, when the public contact II and the normally closed contact III of the relay are closed, the public contact VII is closed with the normally closed contact VI, and the AC circuit is in a connected state while the The freewheeling element is in charging state;

As shown in Figure 5, the normally open contact V of the relay is connected to the electric control switch through the load resistance, and when the common contact VII of the relay is connected to the normally open contact V, the charging is completed. The freewheeling element provides conduction voltage for the electric control switch through the load resistance, and the AC circuit is disconnected. In this embodiment, contacts 1 to 8 are used to represent contacts 1 to 8 in the drawings, mainly to avoid confusion between Arabic numerals and reference signs.

The electric control switch adopts a Darlington triode, and the connection relationship of the Darlington in the system is: the base is connected to the output terminal of the control circuit, the collector is connected to the normally closed contact I of the relay, and the emitter Connect to ground signal. Since the relay adopts the model of switching AC 220v and DC 12v at the same time, the switching current is 2A, because when the disc is full of lights, the maximum brightness of the LED light group needs 12v, 1.2A, converted to AC 220v is less than 100mmA, so the switching current of the selected relay Far greater than the current required by the LED signal light.

The freewheeling element has the function of charging and discharging, and is connected to the DC power generation circuit through the AC on-off control module. When the AC on-off control module is connected to the AC circuit, the DC power generation circuit charges the freewheeling element. In this embodiment, the freewheeling element uses a freewheeling capacitor of 4700uF, which can maintain the system power-off for 4-5s, and prepare for the possible differences in different types of traffic signals. Therefore, the present invention is used for different types and models of traffic signals. Both the fault detection system and the detection method can accurately detect the fault of the LED signal lamp.

The present embodiment also provides a LED signal light fault detection method, including the following steps:

① The AC on-off control module is connected to the AC circuit, and the freewheeling element is charged;

② After the freewheeling element is charged, the LED lamp group current detection module starts to detect the LED lamp group current in real time, and the AC power supply and detection unit detects the AC current in the AC circuit;

③ When the current of the LED lamp group is greater than or equal to the working current threshold of the LED signal lamp, the AC on-off control module remains connected, the AC current detected by the AC power supply and detection unit is not zero, and it is judged that the LED signal lamp is working normally;

When the value of the current of the LED lamp group is less than the operating current threshold of the LED signal lamp, the current detection module of the LED lamp group controls the switching off of the AC on-off control module, and the fully charged freewheeling element provides work for the AC on-off control module voltage, the AC current detected by the AC power supply and detection unit is zero, and it is judged that the LED signal light is faulty.

Example 2

In this embodiment, on the basis of Embodiment 1, the operating current threshold of the LED signal lamp is selected as one-half of the current of the LED signal lamp when all the LED lamps in the LED lamp group are working normally. That is, when half of the LED lamps in the LED lamp group fail, the fault detection system in this embodiment will determine that the LED signal lamp is faulty and needs to be replaced. Although pedestrians and drivers can judge whether the LED signal light is on or not, the system reminds that the LED signal light is faulty and replaces the LED signal light to improve safety performance. In specific applications, the operating current threshold of the LED signal light can also be selected according to the actual situation.

Apparently, the above-mentioned embodiments are only examples for clear description, rather than limiting the implementation. For those of ordinary skill in the art, other changes or changes in different forms can be made on the basis of the above description. It is not necessary and impossible to exhaustively list all the implementation manners here. And the obvious changes or changes derived therefrom are still within the scope of protection of the present invention.

Claims (10)

1. A LED traffic signal light failure monitoring system, comprising an AC power supply and a detection unit arranged inside the traffic signal machine, is characterized in that it also includes: an LED lamp group current detection module arranged outside the traffic signal machine, an alternating current on-off Control modules and freewheeling components; The LED lamp group current detection module is used to detect the magnitude of the LED lamp group current, and when the value of the LED lamp group current is less than the LED signal lamp operating current threshold, send a signal to the AC on-off control module to control the AC The electric on-off control module disconnects the AC loop; The LED lamp group current detection module includes: Current sampling resistor: connected between the output terminal of the LED lamp group and the ground signal, the voltage drop _U1 across the current sampling resistor is proportional to the current of the LED lamp group, when the current of the LED lamp group is equal to the LED lamp group current When the working current threshold of the signal lamp is reached, the voltage drop across the current sampling resistor is U ₀ ; Control circuit: using an MPU controller with an analog-to-digital converter to detect the voltage value _U1 at both ends of the current sampling resistor in real time and compare the relationship between _U1 and _U0 , when _U1 < _U0 , the control circuit outputs "1" control signal, which means that the LED signal light is faulty; The AC power on-off control module is connected between the AC power supply and the primary winding; when the AC power on-off control module is connected to the AC loop, the AC power supply is connected to the primary winding, and the AC power When the on-off control module disconnects the AC loop, the AC power supply is disconnected from the primary winding, and the charged freewheeling element is connected to the AC on-off control module; The AC on-off control module includes an electric control switch, a relay and a load resistor; The electric control switch is connected between the relay and the output terminal of the control circuit, when the control circuit outputs a "1" control signal, the electric control switch is closed and turned on, and the relay disconnects the AC circuit; The relay can simultaneously switch AC 220v and DC 12v, its normally closed contact III is connected to an output end of the AC power supply, the common contact II of the relay is connected to an input end of the primary winding, and the DC The power generation circuit is connected to the freewheeling element through the normally closed contact VI, and when the public contact II of the relay is closed with the normally closed contact III, the public contact VII is closed with the normally closed contact VI at the same time, so The AC circuit is in a connected state while the freewheeling element is in a charging state; The normally open contact V of the relay is connected to the electric control switch through the load resistance, and when the common contact VII of the relay is connected to the normally open contact V, the AC circuit is disconnected, and the charging is completed. The freewheeling element provides a turn-on voltage for the electronically controlled switch through the load resistor; The freewheeling element has the function of charging and discharging, and is connected to the DC power generation circuit through the AC on-off control module. When the AC on-off control module is connected to the AC circuit, the DC power generation circuit charges the freewheeling element. 2. The LED traffic signal lamp failure monitoring system according to claim 1, characterized in that: The electric control switch adopts a Darlington triode, and the connection relationship of the Darlington in the system is: the base is connected to the output terminal of the control circuit, the collector is connected to the normally closed contact I of the relay, and the emitter Connect to ground signal. 3. The LED traffic signal lamp failure monitoring system according to claim 1 or 2, characterized in that: The freewheeling element adopts a 4700uF freewheeling capacitor, one end of the freewheeling capacitor is connected to the ground signal, and the other end is connected to the common contact VII and the normally closed contact VIII of the relay. 4. The LED traffic signal lamp failure monitoring system according to claim 3, characterized in that: The operating current threshold of the LED signal lamp is selected as one-half of the current of the LED lamp group when all the LED lamps in the LED lamp group are working normally. 5. A LED traffic signal lamp failure detection method, is characterized in that, comprises the steps: ① The AC on-off control module is connected to the AC circuit, and the freewheeling element is charged; ② After the freewheeling element is charged, the LED lamp group current detection module starts to detect the LED lamp group current in real time, and the AC power supply and detection unit detects the AC current in the AC circuit; ③ When the current of the LED lamp group is greater than or equal to the working current threshold of the LED signal lamp, the AC on-off control module remains connected, the AC current detected by the AC power supply and detection unit is not zero, and it is judged that the LED signal lamp is working normally; When the value of the current of the LED lamp group is less than the operating current threshold of the LED signal lamp, the current detection module of the LED lamp group controls the switching off of the AC on-off control module, and the fully charged freewheeling element provides work for the AC on-off control module voltage, the AC current detected by the AC power supply and detection unit is zero, and it is judged that the LED signal light is faulty. 6. The LED traffic signal lamp fault detection method according to claim 5, characterized in that: In the step ②, when the AC on-off control module is connected, the change of the current of the LED lamp group is converted into the change of the voltage drop across the current sampling resistor by using the current sampling resistor, and the control circuit is used to detect the change of the current sampling resistor The voltage drop U ₁ at both ends; the control circuit stores the voltage drop U ₀ at both ends of the current sampling resistor when the current of the LED lamp group is equal to the operating current threshold of the LED signal lamp; In the step ③, the control circuit compares the relationship between U ₁ and U ₀ , and when U ₁ <U ₀ , the control circuit outputs a "1" control signal to the AC on-off control module, and the AC The power on-off control module controls the disconnection of the AC circuit, then the AC power supply and detection unit cannot detect the AC current, and judges that the LED signal light is faulty. 7. The LED traffic signal lamp fault detection method according to claim 6, characterized in that: In the step ③, an MPU controller with an analog-to-digital converter is used as the control circuit. 8. The LED traffic signal lamp fault detection method according to claim 6 or 7, characterized in that: In the step ③, the AC on-off control module uses a relay that can simultaneously switch between AC 220v and DC 12v to control whether the AC circuit is connected and the relay is connected in series with an electric control switch, and the relay is disconnected when the electric control switch is turned on AC circuit, when the electric control switch is turned off, the relay is connected to the AC circuit; The control circuit compares the relationship between U ₁ and U ₀ , and when U ₁ <U ₀ , the control circuit outputs a "1" control signal to the electric control switch, the electric control switch is turned on, and the relay The AC circuit is disconnected, and the charged freewheeling capacitor is used as a power supply to provide the relay with the working voltage and the conduction voltage of the electric control switch. The AC power supply and detection unit cannot detect the AC current, and judges that the LED signal light is faulty. 9. The LED traffic signal lamp failure detection method according to claim 8, characterized in that: In the step ①, a 4700uF freewheeling capacitor is selected as the freewheeling element. 10. The LED traffic signal lamp fault detection method according to claim 9, characterized in that: In the step ③, the operating current threshold of the LED signal lamp is selected as half of the current of the LED lamp group when all the LED lamps in the LED lamp group are working normally.

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