Patent Publication Number: US-10314136-B2

Title: Traffic light driving control circuit

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The instant disclosure relates to a drive integrated circuit (drive IC); in particular, to a drive IC having many circuits comprising different functions integrated for driving and controlling a traffic light. 
     2. Description of Related Art 
     For a traditional driving circuit of a traffic light, when different functions are required, new circuits need to be designed and they should be able to be applied to an original core circuit. Moreover, the original core circuit can only execute certain detections and controls by itself. There are some detection functions and some control functions that cannot be directly executed by the drive IC and thus new circuits need to be designed. The newly designed circuits should be able to be applied to the original core circuit, because it is the drive IC that drives them to execute their functions (e.g., a detection function or a control function). However, in this manner, the entire driving circuit of the traffic light is complex and has a big volume, which results in an increase of cost and a difficulty for the management of the circuit elements, and thus the quality of the traffic light suffers. 
     SUMMARY OF THE INVENTION 
     The instant disclosure provides a drive integrated circuit (drive IC) for a controlling traffic light, such as a LED traffic light. Many circuits having different functions for driving or controlling the traffic light are all integrated in one single chip, and in this way less circuit elements are used. Using less circuit elements makes the element management become easier and decreases the element cost, and as a result the product quality is effectively improved. Moreover, using less circuit elements makes the traffic light have a less thick structure. 
     The drive integrated circuit for controlling a traffic light comprises an input end and an output end, an input voltage detection circuit, a gain control circuit, a driving circuit, an impedance loop and a phase detection circuit. The input voltage detection circuit is connected to the input end of the drive integrated circuit. The input voltage detection circuit receives a first external signal to determine whether an input voltage of the traffic light is too low. The drive integrated circuit is shut down if the input voltage of the traffic light is too low. The gain control circuit is connected to the input voltage detection circuit to control the gain of an output end of the input voltage detection circuit. The driving circuit is connected to the gain control circuit, and outputs at least one driving signal. An output end of the driving circuit is the output end of the drive integrated circuit. The impedance loop is connected to the input end of the integrated circuit to detect whether the traffic light is damaged. The phase detection circuit is connected to the input end of the integrated circuit. The phase detection circuit receives a second external signal to obtain and provide a phase difference between the input voltage of the traffic light and the second external signal to the gain control circuit as a reference. The second external signal provides a determined output illumination of the traffic light. A rectifier is connected to the input end of the drive integrated circuit to provide a power supply. A load is connected to the output end of the drive integrated circuit, and the load is the traffic light comprising a LED lamp set. 
     In one embodiment of the drive IC for controlling a traffic light, the first external signal provides a determined low voltage. When the input voltage of the traffic light is lower than the determined low voltage provided by the first external signal, the gain control circuit shuts down the driving circuit and the load is not driven. At the same time, the gain control circuit protection control circuit is shut down and the impedance loop is driven, such that the impedance of the traffic light is low and an external traffic light controller can determine whether the traffic light is damaged. 
     In one embodiment of the drive IC for controlling a traffic light, the second external signal provides the determined output illumination. The gain control circuit controls the driving circuit to adjust the illumination of the traffic light according to the determined output illumination provided by the second external signal. 
     In one embodiment of the drive IC for controlling a traffic light, the drive IC further comprises a load current/voltage detection circuit and a protection control circuit. The load current/voltage detection circuit is connected to the driving circuit, and detects an output voltage and an output current of the drive integrated circuit. The protection control circuit is connected to the load current/voltage detection circuit and the input voltage detection circuit. The protection control circuit receives a third external signal that provides threshold values of the output voltage and the output current of the drive integrated circuit. Also, the protection control circuit determines whether the output current of the drive integrated circuit are larger than or lower than their corresponding threshold values to further determine whether to execute a protection mechanism. When the output current of the drive integrated circuit are larger than or lower than their corresponding threshold values provided by the third external signal, the protection control circuit executes the protection mechanism by turning on a switching circuit. The switching circuit is connected to the protection control circuit and the rectifier of the drive integrated circuit. By turning on a switching circuit, the drive integrated circuit is shut down to protect the traffic light. 
     In one embodiment of the drive IC for controlling a traffic light, the protection control circuit receives the third external signal. 
     For further understanding of the instant disclosure, reference is made to the following detailed description illustrating the embodiments of the instant disclosure. The description is only for illustrating the instant disclosure, not for limiting the scope of the claim. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
         FIG. 1  shows a block diagram of a drive IC for controlling a traffic light of the first embodiment of the instant disclosure. 
         FIG. 2  shows a block diagram of a drive IC for controlling a traffic light of the second embodiment of the instant disclosure. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The instant disclosure relates to a drive integrated circuit (Drive IC) for a controlling traffic light, such as LED traffic lights. Many circuits having different functions for driving or controlling traffic lights are all integrated in one single chip, and in this way less circuit elements will be used. 
     Referring to  FIG. 1 ,  FIG. 1  shows a block diagram of a drive IC for controlling a traffic light of the first embodiment of the instant disclosure. As shown in  FIG. 1 , an input end of the drive IC  1  for controlling a traffic light is connected to a rectifier  30 . The rectifier  30  receives and rectifies an AC power source and transmits the rectified current to the drive IC  1 . An output end of the drive IC  1  is connected to a load  40 , and the load  40  will be driven by the drive IC  1 . The load  40  can be an LED illumination module, an LED light string, many lamp sets that are in serial, an LED lamp module or the like, but it is not limited herein. The rectifier  30  can be a full-bridge rectifier, a half-bridge rectifier, a center-tapped full-bridge rectifier or the like, but it is also not limited herein. Moreover, the AC power source can be a utility power. The drive integrated circuit having circuits having different functions for driving or controlling traffic lights which are all integrated in one single chip is the drive IC  1 . 
     The drive IC  1  for controlling traffic lights comprises an input low-voltage control circuit  10 , a gain control circuit  12 , a driving circuit  14 , an impedance loop  16  and a phase detection circuit  18 . An input end of the input low-voltage control circuit  10 , which is just the input end of the drive IC  1 , is connected to the rectifier  30 , and another input end of the input low-voltage control circuit  10  receives a first external signal. The first external signal provides a determined low voltage. The input low-voltage control circuit  10  detects whether the input voltage of the traffic light is too low. If the input voltage of the drive integrated circuit is lower than the determined low voltage provided by the first external signal, it indicates that the traffic light needs to be turned off, so as to prevent the traffic light works abnormally because of being driven by a low input voltage. 
     An output end of the input low-voltage control circuit  10  is connected to the gain control circuit  12 . An output end of the gain control circuit  12  is connected to the driving circuit  14 . The gain control circuit  12  controls the gain of the entire drive IC  1  or the gain of the output of the drive IC  1 . Moreover, the gain control circuit  12  can adjust the gain of each circuit in the drive IC  1  for the driving circuit  14 . The driving circuit  14  is connected to a load  40 , and outputs a driving signal to drive the load  40 , for example, to turn on the LED lamp set. The gain control circuit  12  is connected to the driving circuit  14 , such that the driving circuit  14  can linearly increase the driving current of the traffic light, such as LED lamp sets that are in serial. In this manner, when the input voltage of the drive IC varies, the driving circuit  14  can determine how many LED lamp sets can be driven. 
     The impedance loop  16  is connected to the node connecting the input low-voltage control circuit  10  and the rectifier  30 . The node connecting the input low-voltage control circuit  10  and the rectifier  30  is just the input end of the drive IC  1 . In this manner, the impedance loop  16  helps an external traffic light controller to determine whether the traffic light is damaged even when the power supply is cut. The traffic light controller determines that the traffic light is damaged if the impedance loop  16  detects that the impedance at the output end of the rectifier  30  is high. For example, when the LED lamp set is damaged or the fuse is burned out, the drive IC  1  turns into an open circuit and thus the equivalent resistance measured at the output of the rectifier  30  will be very large. On the contrary, the traffic light controller determines that the traffic light is not damaged if the impedance loop  16  detects that the impedance at the output end of the rectifier  30  is low. The impedance loop  16  integrated in the drive IC  1  can provide an impedance detection function for helping the traffic light controller to determine whether the traffic light is not damaged 
     An input end of a phase detection circuit  18  is connected to the input end of the drive IC  1 , and another input end of the phase detection circuit  18  receives a second external signal. An output end of the phase detection circuit  18  is connected to the gain control circuit  12 . The phase detection circuit  18  detects a phase difference between the input voltage of the traffic light and the second external signal. The gain control circuit  12  adjust the input voltage and the input current of the driving circuit  14  according to the phase difference, so that the phases of the input voltage and the input current of the driving circuit  14  will not change. In another embodiment, the second external signal provides a predetermined output of the driving circuit  14  to the gain control circuit  12  as a reference, so that the traffic light driven by the driving circuit  14  can have a constant illumination even the input voltage of the drive IC  1  varies. 
     Referring to  FIG. 2 ,  FIG. 2  shows a block diagram of a drive IC for controlling a traffic light of the second embodiment of the instant disclosure. The difference between the drive IC  1  shown in  FIG. 1  and the drive IC  1  in this embodiment is that the drive IC  1  in this embodiment further comprises a load current/voltage detection circuit  20  and a protection control circuit  22 . Moreover, a switching circuit  50  is connected to the drive IC  1 , and the drive IC  1  further receives a third external signal. An input end of the load current/voltage detection circuit  20  is connected to the driving circuit  14 , and an output end of the load current/voltage detection circuit  20  is connected to the protection control circuit  22 . The load current/voltage detection circuit  20  detects the voltage and the current of the load  40 . The protection control circuit  22  is connected to the input low-voltage control circuit  10  and the switching circuit  50 , and receives the third external signal. The switching circuit  50  is connected to the rectifier  30 . 
     The load current/voltage detection circuit  20  detects the voltage and the current of the load  40 . When the voltage or the current of the load  40  is too large or too small, specifically speaking, when the voltage or the current of the load  40  is larger or smaller than a threshold value provided by the third external signal, the protection control circuit  22  further determines whether the input voltage of the drive IC  1  is lower than the low-voltage signal. According to the determination about whether the voltage or the current of the load  40  is larger or smaller than a threshold value provided by the third external signal, and the determination about whether the input voltage of the drive IC  1  is lower than the low-voltage signal, the protection control circuit  22  determines whether to execute a protection mechanism to turn on the switching circuit  50  for shutting down the traffic light. 
     The switching circuit  50  is configured outside the drive IC  1 , and is connected to the protection control circuit  22  of the drive IC  1  and the rectifier  30 . The switching circuit  50  can control the rectifier  30  to shut down the entire drive IC  1 . Alternatively, the protection control circuit  22  can transmit a signal to turn on the switching circuit  50 , and then the switching circuit  50  controls the rectifier  30  to shut down the drive IC  1  for protecting the traffic light. 
     The impedance loop  16 , the input low-voltage control circuit  10  and the phase detection circuit  18  of the drive IC  1  in this embodiment have the same connection relationship and the same working mechanism as the impedance loop  16 , the input low-voltage control circuit  10  and the phase detection circuit  18  of the drive IC  1  shown in  FIG. 1 . 
     The drive IC for controlling a traffic light provided by the instant disclosure at least has the following advantages: 
     1. It can decrease the volume of the traffic light because less circuit elements need to be used, which further makes the cost go down. 
     2. Compared with a traditional driving circuit for driving the traffic light, 70% of the needed circuit elements can be removed, which makes the management of the circuit elements easier. 
     3. The cost of the traffic light using the drive IC provided by the instant disclosure can be only 85% of the cost of a traditional traffic light, which is more competitive. 
     4. It has a simplified core circuit, and allows the light source elements of the traffic light and the circuit elements of the drive IC to be co-designed. 
     5. Common circuit elements can be designed together, which can be applied to a wide voltage range from 12V to 277V. 
     6. It can directly drive the load, such as a LED light source, with many different kinds of external controllers. 
     7. It can detect the input voltage and determines whether to drive the load or protect the load according to different external signals. 
     8. When the drive IC does not work, its internal resistance is low, such that an external controller determines that the traffic light is not damaged, and the traffic light will not be suddenly turned on due to a great leakage current. 
     9. It can detect the variation of the voltage or the current of the load, and further determine the driving signal according to the external signals. 
     10. It can detect the voltage or the phase difference of the driving circuit, and further adjust the output gain according to the external signals to control the illumination of the load. 
     To sum up, the drive IC for controlling a traffic light provided by the instant disclosure has a less cost, and makes the management of the circuit elements easier, which can thus improve the quality of the traffic light. Moreover, using less circuit elements makes the traffic light have a less thick structure, in other words, a smaller volume. The descriptions illustrated supra set forth simply the preferred embodiments of the instant disclosure; however, the characteristics of the instant disclosure are by no means restricted thereto. All changes, alterations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the instant disclosure delineated by the following claims.