Patent Publication Number: US-2019191526-A1

Title: Led lamp protection circuit

Description:
TECHNICAL FIELD 
     The invention relates to the field of LED illumination, and in particular to a protection circuit for an LED lamp. 
     BACKGROUND 
     LED lighting has seen rapid growth in recent years owing to its energy efficiency, long service life, compact size, and environmental friendly advantages. The time to replace traditional incandescent and fluorescent lighting with LED lighting is here. 
     In the process of replacing a fluorescent lamp with an LED lamp, the electronic ballast of the fluorescent lamp is usually not replaced in order to save cost. Generally, it is required that the driving circuit of the LED lamp is able to take power from the output of the electronic ballast, thereby allowing the replacement of the LED lamp by simply removing the old fluorescent lamp. LED lamps nowadays are able to use the electronic ballast of the original fluorescent lamp as the driver of the LED lamp. When modifying the lamp, not only can this bypass the additional configuration of special LED drivers, but it also saves a lot of labor. This is especially true in expensive countries or regions. 
     Existing LED lamps generally comprise a lamp, a circuit board configured within the lamp and having a light source, and a cap configured at an end of the lamp. A power source is provided in the cap, the light source and the power source are electrically connected through the circuit board. However, there is sometimes poor soldering in the circuit board of the LED lamp or poor soldering between the light source of the LED lamp and the circuit board, which causes the LED lamp circuit to open. If the LED lamp circuit is open, the electronic ballast will generate a continuous high voltage at the point of the LED lamp circuit that is open, so that an arc, that is, an arcing phenomenon, is easily generated. The generated arc can easily cause the rectifier circuit of the LED lamp to be damaged. If the arc is significant, the high temperature generated may cause the circuit board of the LED lamp to be carbonized or overheat. In severe cases, it may emit smoke or even catch fire, which is a serious safety hazard (electric shock or fire) for the user. 
     Therefore, it is necessary to provide a novel protection circuit for an LED lamp which can solve at least one of the above-mentioned technical problems. 
     SUMMARY 
     An LED lamp protection circuit comprising: a driving circuit, a rectifier circuit coupled with the driving circuit, an LED luminous component circuit coupled with the rectifier circuit, and an arcing protection circuit coupled between the rectifier circuit and the LED luminous component circuit. The arcing protection circuit and the LED luminous component circuit are connected in parallel. When the LED lamp works at a normal condition, the arcing protection circuit is in blocking state; when the LED lamp is open, the arcing protection circuit is turned on, a loop circuit is formed between the driving circuit and the arcing protection circuit to extinguish arc. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       These and other features, aspects and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings, in which like reference numerals are used throughout the drawings to refer to like parts, where: 
         FIG. 1  is a schematic diagram of a protection circuit for an LED lamp according to an embodiment of the present invention. 
         FIG. 2  is a circuit diagram of a protection circuit of an LED lamp according to an embodiment of the present invention. 
         FIG. 3  is a circuit diagram of a protection circuit of an LED lamp according to an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of a protection circuit of an LED lamp according to an embodiment of the present invention. 
         FIG. 5  is a circuit diagram of a protection circuit of an LED lamp according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Unless otherwise defined, technical terms or scientific terms used in the specification and claims shall be used in the ordinary meaning as understood by those having ordinary skill in the art to which the invention pertains. “First”, “second”, and similar words used herein do not denote any order, quantity, or importance, but are merely intended to distinguish between different constituents. The terms “one”, “a” and similar words are not meant to be limiting, but rather denote the presence of at least one. The approximate language used herein can be used for quantitative expressions, indicating that there is a certain amount of variation that can be allowed without changing the basic functions. Therefore, the numerical values corrected by languages such as “approximately”, “about” are not limited to the exact numerical value itself. Similarly, the terms “one”, “a”, and similar words are not meant to be limiting, but rather denote the presence of at least one. “Comprising”, “consisting”, and similar words mean that elements or articles appearing before “comprising” or “consisting” include the elements or articles and their equivalent elements appearing behind “comprising” or “consisting”, not excluding any other elements or articles. “Connected”, “connection”, “coupled”, and similar words are not limited to a physical or mechanical connection, but may include direct or indirect electrical connections, thermal connections, thermally conductive connections, and thermally transmissive connections. 
     The present invention relates to a protection circuit for an LED lamp, in particular to a protection circuit for an LED lamp driven by an electronic ballast. 
     Please refer to  FIG. 1 , which is a schematic diagram of a protection circuit  100  of an LED lamp according to an embodiment of the present invention, which comprises a driving circuit  101 , a rectifier circuit  102  coupled to the driving circuit  101 , an LED luminous component circuit  104  coupled to the rectifier circuit  102 , and an arcing protection circuit  103  coupled between the rectifier circuit  102  and the LED luminous component circuit  104 . 
     The driving circuit  101  is for driving an LED lamp, which can be used to receive an AC voltage from an AC power source and convert it into a high frequency AC voltage as a drive voltage of the rectifier circuit  102 . The driving circuit  101  can be an electronic ballast for converting the grid voltage into a high frequency, high voltage AC voltage. The electronic ballast can be a common electronic ballast, such as an instant-start electronic ballast, a programmed-start electronic ballast, a rapid-start electronic ballast, and so on. The protection circuit of the LED lamp is applicable to various types of electronic ballasts, and is not limited to the types of electronic ballasts mentioned above. The driving circuit  101  can be connected to one or both ends of the LED lamp through pins (not shown) of the LED lamp to transmit AC power to the rectifier circuit  102 . 
     The rectifier circuit  102  comprises an AC-DC converter, which is a full wave bridge rectifier circuit. The rectifier circuit may comprise four or more separate silicon diodes or a bridge assembly. The rectifier circuit  102  is configured to adjust a voltage of the LED luminous component circuit  104 , and convert the high frequency alternating current outputted by the driving circuit  101  into a direct current. The DC voltage positive output terminal and the DC voltage negative output terminal of the rectifier circuit  102  are coupled to both ends of the LED luminous assembly circuit  104  separately to provide an adjusted voltage and current required to drive the LED luminous component circuit  104 . 
     The arcing protection circuit  103  is coupled between the rectifier circuit  102  and the LED luminous component circuit  104 . An input terminal of the arcing protection circuit  103  is connected to a DC voltage output terminal of the rectifier circuit  102 , the output terminal is connected to the LED luminous component circuit  104 . When the LED lamp works under a normal condition, the arcing protection circuit  103  is in blocking state and does not function; when the LED lamp circuit is open, the arcing protection circuit  103  is turned on, a loop circuit is formed between the driving circuit  102  and the arcing protection circuit  103  to extinguish arc. 
     The LED luminous component circuit  104  comprises a light emitting diode assembly, which comprises a plurality of light emitting diodes connected in series. 
     Please refer to  FIG. 2 , which is a circuit diagram of a protection circuit  200  for an LED lamp according to an embodiment of the present invention. The protection circuit  200  of the LED lamp shown in  FIG. 2  comprises a driving circuit  201 , a rectifier circuit  202  coupled to the driving circuit  201 , an LED luminous component circuit  204  coupled to the rectifier circuit  202 , and the arcing protection circuit  203  coupled between the rectifier circuit  202  and the LED luminous component circuit  204 . 
     The driving circuit  201  is similar in structure and function to the driving circuit  101  in  FIG. 1 , and its details are not described herein. The driving circuit  201  comprises an electronic ballast that can be used to convert an alternating voltage of an alternating current source into a high frequency alternating voltage. 
     The rectifier circuit  202  comprises an AC-DC converter, which is a full-wave bridge rectifier circuit comprising a rectifier diode D 1 , a rectifier diode D 2 , a rectifier diode D 3 , and a rectifier diode D 4 . The rectifier circuit  203  is configured to adjust a voltage across the LED luminous component circuit  204  to convert the high frequency alternating current output by the driving circuit  201  into a DC current required by the LED lighting component circuit  204 . The input terminals of the rectifier circuit  202  are respectively connected to the AC voltage first input terminal AC 1  and the AC voltage second input terminal AC 2  of the driving circuit  201 . The output terminals of the rectifier circuit  202  comprise a DC voltage positive output terminal DC+ and a DC voltage negative output terminal DC−, which are respectively connected to the arcing protection circuit  203  and the two terminals of the LED luminous component circuit  204 . The rectifier circuit  202  of this embodiment is only an example. The number of rectifier diodes is not limited by this embodiment and may adjusted according to the needs of the circuit. 
     The arcing protection circuit  203  and the LED luminous component circuit  204  are connected in parallel. The arcing protection circuit  203  comprises a reverse diode, whose negative pole is connected to the DC voltage positive output terminal DC+ of the rectifier circuit  202 , and whose anode is connected to the DC voltage negative output terminal DC− of the rectifier circuit  202 . Under normal conditions, the reverse diode is not turned on because its reverse conducting voltage is greater than the operating voltage of the LED luminous component circuit  204 . The reverse diode is turned on only when the voltage reaches or exceeds the reverse conducting voltage of the reverse diode, and a loop circuit is formed between the driving circuit  201  and the arcing protection circuit  203  to eliminate arc. 
     The LED luminous component circuit  204  comprises a light-emitting diode component, which comprises a plurality of light-emitting diodes LED 1  to LEDN connected in series. 
     The protection circuit  200  of the LED lamp further comprises a non-resettable thermal fuse  205  configured between the driving circuit  201  and the rectifier circuit  202 . The non-resettable thermal fuse  205  may be configured at the AC voltage first output terminal AC 1  or the AC voltage second output terminal AC 2  of the driving circuit  201 . In this embodiment, the non-resettable thermal fuse  205  is configured at the first output terminal AC 1  of the AC voltage of the driving circuit  201 , one terminal thereof is connected to the AC output first output terminal AC 1 , and the other terminal thereof is connected to an input terminal of the rectifier circuit  202 . 
     When the LED lamp works under a normal condition, the arcing protection circuit  203  is in blocking state and does not function, a loop circuit is formed between the driving circuit  201  and the LED luminous component  204 , the LEDs of LED 1  to LEDN are illuminated, and the LED lamp is able to function as normal. When the LED lamp circuit is open, the arcing protection circuit  203  will function, which will be turned on by the high voltage generated by the driving circuit  201 , forming a loop circuit between the driving circuit  202  and the arcing protection circuit  203 ; to avoid continuous high voltage in the entire circuit, it can eliminate the arc and provide arcing protection. After the arcing protection circuit has functioned, the non-resettable thermal fuse  205  is blown by the high temperature generated by the arcing protection circuit  203  to prevent the entire LED lamp from continuing high voltage and high temperature, thereby further protecting the entire circuit of the LED lamp and eliminating potential safety hazards. 
     Please refer to  FIG. 3 , which is a circuit diagram of a protection circuit  300  for an LED lamp according to an embodiment of the present invention. The protection circuit  300  of the LED lamp shown in  FIG. 3  also comprises a driving circuit  301 , a rectifier circuit  302  coupled to the driving circuit  301 , an LED luminous component circuit  304  coupled to the rectifier circuit  302 , and an arcing protection circuit  303  coupled between the rectifier circuit  302  and the LED luminous component circuit  304 . 
     The protection circuit of the LED lamp shown in  FIG. 3  is similar to the protection circuit of the LED lamp shown in  FIG. 2 , and its details are not described herein. The arcing protection circuit  303  shown in  FIG. 3  also comprises a reverse diode, which is similar to the reverse diode of the arcing protection circuit  203  shown in  FIG. 2 , and its details are also not described again. The protection circuit of the LED lamp shown in  FIG. 3  is different from the protection circuit of the LED lamp shown in  FIG. 2 , in that the location of connection of the non-resettable thermal fuse  305  of the protection circuit of the LED lamp is different from that of the non-resettable thermal fuse  205  as shown in  FIG. 2 . The non-resettable thermal fuse  305  of  FIG. 3  is placed at the DC voltage output terminal of the rectifier circuit  302 , one end of which is connected to the DC voltage positive output terminal DC+ of the rectifier circuit  302 , while the other end of which is connected to the negative terminal of the reverse diode. 
     The protection circuit of the LED lamp shown in  FIG. 3  and the protection circuit of the LED lamp shown in  FIG. 2  are similar in operation. When the LED lamp works under a normal condition, the arcing protection circuit  303  is in blocking state and does not function, a loop circuit is formed between the driving circuit  301  and the LED luminous component  304 , the LEDs of LED 1  to LEDN are illuminated, and the LED lamp is able to function as normal. When the LED lamp circuit is open, the arcing protection circuit  303  will function, which will be turned on by the high voltage generated by the driving circuit  301 , forming a loop circuit between the driving circuit  302  and the arcing protection circuit  303 ; to avoid continuous high voltage in the entire circuit, it can eliminate the arc and provide arcing protection. After the arcing protection circuit  303  has functioned, the non-resettable thermal fuse  305  is blown by the high temperature generated by the arc protection circuit  303  to prevent the entire LED lamp from continuing high voltage and high temperature, thereby further protecting the entire circuit of the LED lamp and eliminating potential power safety hazards. 
     Please refer to  FIG. 4 , which is a circuit diagram of a protection circuit  400  for an LED lamp according to an embodiment of the present invention. The protection circuit  400  of the LED lamp shown in  FIG. 4  also comprises a driving circuit  401 , a rectifier circuit  402  coupled to the driving circuit  401 , an LED luminous component circuit  404  coupled to the rectifier circuit  402 , and an arcing protection circuit  403  coupled between the rectifier circuit  402  and the LED luminous component circuit  404 . 
     The protection circuit of the LED lamp shown in  FIG. 4  is similar to the protection circuit of the LED lamp shown in  FIG. 2  and  FIG. 3 , and its details are not described herein. The arcing protection circuit  403  shown in  FIG. 4  also comprises a reverse diode, which is similar to the reverse diode of the arcing protection circuit shown in  FIGS. 2 and 3 , and its details are not described herein. The protection circuit of the LED lamp shown in  FIG. 4  is different from the protection circuit of the LED lamp shown in  FIG. 2  and  FIG. 3 , in that the non-resettable thermal fuse  405  of the protection circuit of the LED lamp is connected to a different location as the non-resettable thermal fuses as shown in  FIG. 2  and  FIG. 3 . The non-resettable thermal fuse  405  as shown in  FIG. 4  is placed at the DC voltage negative output terminal of the rectifier circuit  402 , one end of which is connected to the DC voltage negative output terminal DC− of the rectifier circuit  402 , while the other end of which is connected to the positive terminal of the reverse diode. 
     The protection circuit of the LED lamp shown in  FIG. 4  and the protection circuit of the LED lamp shown in  FIGS. 2 and 3  are similar in operation. When the LED lamp works under a normal condition, the arcing protection circuit  403  is in blocking state and does not function, a loop circuit is formed between the driving circuit  401  and the LED luminous component  404 , the LEDs of LED 1  to LEDN are illuminated, and the LED lamp is able to function as normal. When the LED lamp circuit is open, the arcing protection circuit  403  will function, which will be turned on by the high voltage generated by the driving circuit  401 , forming a loop circuit between the driving circuit  402  and the arcing protection circuit  403 ; to avoid continuous high voltage in the entire circuit, it can eliminate the arc and provide arcing protection. After the arcing protection circuit  403  has functioned, the non-resettable thermal fuse  405  is blown by the high temperature generated by the arc protection circuit  403  to prevent the entire LED lamp from continuing high voltage and high temperature, thereby further protecting the entire circuit of the LED lamp and eliminating potential power safety hazards. 
       FIG. 5  is a circuit diagram of a protection circuit  500  for an LED lamp according to an embodiment of the present invention. The protection circuit  500  of the LED lamp shown in  FIG. 5  also comprises a driving circuit  501 , a rectifier circuit  502  coupled to the driving circuit  501 , an LED luminous component circuit  504  coupled to the rectifier circuit  502 , and an arcing protection circuit  503  coupled between the rectifier circuit  502  and the LED luminous component circuit  504 . 
     The protection circuit of the LED lamp shown in  FIG. 5  is similar to the protection circuit of the LED lamp shown in  FIG. 2  to  FIG. 4 , and its details are not described herein. The protection circuit of the LED lamp shown in  FIG. 5  differs from the protection circuit of the LED lamp shown in  FIGS. 2 to 4 , in that the arcing protection circuit  503  comprises a bidirectional voltage protection element. In this embodiment, the bidirectional voltage protection component may comprise a silicon diode for alternating current (SIDAC). In the present invention, the bidirectional voltage protection element is not limited to those enumerated in this embodiment, and may also comprise other types of bidirectional voltage protection elements. The bidirectional voltage protection element and the LED luminous component circuit  504  are connected in parallel. At the same time, one end of the bidirectional voltage protection element is connected to the DC voltage positive output terminal DC+ of the rectifier circuit  502 , while the other end is connected to the DC voltage negative output terminal DC− of the rectifier circuit  502 . Under a normal condition, the silicon diode for alternating current (SIDAC) is not turned on because its turn-on threshold voltage is greater than the operating voltage of the LED luminous component circuit  504 . The silicon diode for alternating current (SIDAC) is turned on only when the voltage reaches or exceeds the turn-on voltage threshold of the silicon diode for alternating current (SIDAC), a loop circuit is formed between the driving circuit  501  and the arcing protection circuit  503  to eliminate the arc and potential electrical safety hazards. 
     When the LED lamp works under a normal condition, the arcing protection circuit  503  is in blocking state and does not function, that is, the silicon diode for alternating current (SIDAC) is in blocking state, a loop circuit is formed between the driving circuit  501  and the LED luminous component circuits  504 , the LEDs of LED 1  to LEDN are illuminated, and the LED lamp is able to function as normal. When the LED lamp circuit is open, the arc protection circuit  503  will function, that is, the silicon diode for alternating current (SIDAC) will be turned on by the high voltage generated by the driving circuit  501 , a loop circuit is formed between the driving circuit  501  and the arcing protection circuit  503  to prevent the entire circuit from continuing to have a high voltage, thereby eliminating the arc and providing arc protection, eliminating potential power safety hazards. 
     The description uses specific embodiments to describe the present invention, including the best mode, and can help any person skilled in the art perform experimental operations. These operations include using any device and system and using any specific method. The patentable scope of the present invention is defined by the claims, and may include other examples that occur in the art. Other examples are considered to be within the scope of the claims of the invention if they are not structurally different from the literal language of the claims or they have equivalent structures as described in the claims.