Patent Publication Number: US-9839077-B2

Title: LED lighting device using ballast

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Korean Patent Application No. 10-2013-0019310, filed on Feb. 22, 2013, the contents of which are hereby incorporated by reference in their entirety into the present disclosure. 
     BACKGROUND 
     Field 
     The present invention relates to an LED lighting device using a ballast 
     Description of Related Art 
     Recently, a light emitting diode (LED) is being increasingly used as a new lighting device in place of a filament bulb or a fluorescent lamp and becomes popular. The LED can be driven at a low voltage and has a longer life span, lower power consumption, a more rapid response speed and stronger crashworthiness than those of other lighting devices. The LED can become smaller and lighter. However, since the LED is activated by a very low direct current power and is turned on in a manner different from that of the fluorescent lamp, a general LED lamp cannot be applied as it is to a fluorescent lamp system. In particular, an electronic ballast converts a commercial alternating current power of 60 Hz into a radio frequency of several tens of KHz, and then provides to the lamp. Therefore, conventional lighting devices as well as the ballast should be removed in order to use the LED lighting device. If an LED driving circuit is directly connected to the connection terminal of the conventional ballast without removing the ballast, etc., the LED driving circuit is not able to process the high frequency or voltage of the ballast, etc., so that the LED lamp does not work or is destroyed. 
     Accordingly, recently, an LED lighting device capable of being directly connected to the ballast and used without removing the ballast is being developed. 
     SUMMARY 
     One embodiment is an LED lighting device using a ballast. The LED lighting device includes: an LED unit which includes at least one LED device; a rectifier which rectifies a current power signal output from the ballast; and a current driving unit which receives an output current of the rectifier and controls the power which is transmitted from the ballast to the LED unit. The current driving unit transmits current which has a magnitude greater than that of the output current of the rectifier to the LED unit. 
     The current driving unit may include: a switch which electrically connects or disconnects transmission of some of the received ballast output power to the LED unit; a diode which allows the current to continuously flow to the LED unit when the switch is in an off-state; and a capacitor and an inductor which store and release energy in a reciprocal manner. 
     The LED lighting device may further include a current sensor which senses a magnitude of the current flowing through the LED unit; and a controller which receives the magnitude of the current flowing through the LED unit from the current sensor and controls on/off of the switch. 
     The controller may use a ballast which increases a duty of the switch when the value of the current flowing through the LED unit is greater than a predetermined current value, and decreases the duty of the switch when the value of the current flowing through the LED unit is less than a predetermined current value. 
     The LED lighting device using the ballast may include a first connection terminal CT 1  which includes a first electrode and a second electrode and receives the power from the ballast; and a second connection terminal CT 2  which includes a third electrode and a fourth electrode and receives the power from the ballast. The rectifier may include: a first rectifier which includes a first filament capacitor which is connected in parallel to the first electrode and the second electrode and a plurality of bridge diodes; and a second rectifier which includes a second filament capacitor which is connected in parallel to the third electrode and the fourth electrode and a plurality of bridge diodes. 
     The current driving unit may include a switch which connects or disconnects electrically transmission of some of the received ballast output power to the LED unit; a diode which allows the current to continuously flow to the LED unit when the switch is in an off-state; a capacitor which stores or releases energy; and a transformer which electrically separates the ballast from the LED unit. 
     The LED lighting device may further include a current sensor which senses a magnitude of the current flowing through the LED unit; and a controller which receives the magnitude of the current flowing through the LED unit from the current sensor and controls on/off of the switch. 
     The controller may increase a duty of the switch when the value of the current flowing through the LED unit is greater than a predetermined current value, and may decrease the duty of the switch when the value of the current flowing through the LED unit is less than a predetermined current value. 
     The LED lighting device may further include a filter which smoothes an output signal of the current driving unit and transmits to the LED unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit diagram of an LED lighting device using a ballast; 
         FIG. 2  is a block diagram of an LED lighting device using a ballast according to an embodiment of the present invention; 
         FIG. 3  is a circuit diagram of an LED lighting device using a ballast according to the embodiment of the present invention; 
         FIG. 4 a    is a circuit diagram showing that both ends of a lamp are connected to a choke magnetic ballast by using a two-terminal short-circuit rectifier; 
         FIG. 4 b    is a circuit diagram showing that both ends of the lamp are connected to a rapid start magnetic ballast by using the two-terminal short-circuit rectifier; 
         FIG. 4 c    is a circuit diagram showing that both ends of the lamp are connected to a rapid start electronic ballast by using a rectifier into which a resistor of filament has been inserted; 
         FIG. 4 d    is a circuit diagram showing that both ends of the lamp are connected to the rapid start electronic ballast by using a rectifier inserted into the both ends of the lamp respectively; 
         FIG. 4 e    shows an equivalent circuit to that of  FIG. 4   d;    
         FIG. 5  is a circuit diagram of the rectifier according to the embodiment of the present invention; 
         FIGS. 6 a  to 6 d    are circuit diagrams showing various implementation examples of the rectifier in accordance with the embodiment of the present invention; 
         FIGS. 7 a  to 7 d    are circuit diagrams of the LED lighting device using the rectifier in accordance with the embodiment of the present invention and are views showing that the LED lighting device is connected to various ballasts; 
         FIG. 8 a    shows the LED lighting device including a current buck converter, and  FIG. 8 b    shows the LED lighting device including a current boost converter; 
         FIG. 9  is a circuit diagram of an LED lighting device according to another embodiment of the present invention; 
         FIG. 10  is a circuit diagram of an LED lighting device according to further another embodiment of the present invention; and 
         FIG. 11 a    shows a circuit of a current driving unit including the current boost converter and shows a waveform of a specific signal, and  FIG. 11 b    shows a circuit of a current driving unit using a transformer and shows a waveform of a specific signal. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description of the present invention shows a specified embodiment of the present invention and will be provided with reference to the accompanying drawings. The embodiment will be described in enough detail that those skilled in the art are able to embody the present invention. It should be understood that various embodiments of the present invention are different from each other and need not be mutually exclusive. For example, a specific shape, structure and properties, which are described in this disclosure, may be implemented in other embodiments without departing from the spirit and scope of the present invention with respect to one embodiment. Also, it should be noted that positions or placements of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Therefore, the following detailed description is not intended to be limited. If adequately described, the scope of the present invention is limited only by the appended claims of the present invention as well as all equivalents thereto. Similar reference numerals in the drawings designate the same or similar functions in many aspects. 
     Embodiment of the Present Invention 
     The principle of an LED lighting device using a ballast in accordance with the embodiment of the present invention will be briefly described. 
       FIG. 1  shows an LED lighting device using a ballast. 
     Referring to  FIG. 1 , in the LED lighting device, power sources  31  and  33  receive alternating current power through power input terminals  15  and  16 . A rectifier  35  receives and full-wave rectifies the power from the power sources  31  and  33 , and then transmits to a filter  39 . The filter  39  smoothes the full-wave rectified voltage from the rectifier  35  into a direct current voltage, and then transmits to a driving unit  41 . The driving unit  41  includes a buck-boost converter and controls the voltage and current which are supplied to the LED to be constant by using the direct current voltage output from the filter  39 . 
     However, the LED lighting device shown in  FIG. 1  has a structure for controlling only the power transmitted to the LED by using a voltage converter without consideration of the output of the ballast. When the output power of the ballast is larger than the power required by the LED, energy is accumulated in the capacitor of the filter  39  and the voltage continuously rises. Describing in more detail, in the LED lighting device in a steady state, when the current which is input from the ballast for any reason is increased, the amount of electric charges accumulated in the capacitor of the filter  39  is increased, and thus, the voltage at both sides of the capacitor of the filter  39  rises. Since the LED lamp consumes a constant power, the amount of the current which is transmitted from the filter  39  to the LED lamp becomes less than that of the steady state. Therefore, since the amount of the current which is input to the filter  39  is less than the amount of the current which is output from the filter  39 , a voltage higher than an acceptable value is applied to the filter  39  comprised of the capacitors due to a positive feedback phenomenon in which the voltage at both sides of the capacitor of the filter  39  is continuously increased, so that passive devices or chips of the LED lighting device are damaged. That is, the lifespan of the LED lighting device is shortened. Besides, the LED lighting device is not compatible with various ballasts having different standards and has stability vulnerable to the power change. In particular, the ballast of the currently and widely used fluorescent lamp or halogen lamp has a different operating method from that of the LED device and has problems to be used in direct connection with the LED device. 
     The below-described LED lighting device using the ballast in accordance with the embodiment of the present invention is able to overcome the above-mentioned problems. 
     Hereafter, the LED lighting device using the ballast in accordance with the embodiment of the present invention will be described. 
       FIG. 2  is a block diagram of an LED lighting device  200  using a ballast according to an embodiment of the present invention. 
     Referring to  FIG. 2 , the LED lighting device using the ballast according to the embodiment of the present invention includes an LED unit  130  which includes at least one LED device, a rectifier  100  which rectifies a current power signal output from a ballast  10 , and a current driving unit  110  which receives an output signal of the rectifier  100  and controls the power which is transmitted from the ballast  10  to the LED unit  130 . 
     Also, the LED lighting device  200  using the ballast according to the embodiment of the present invention may further include a filter  120  which smoothes the output signal of the current driving unit  110  and transmits to the LED unit  130 . 
     The ballast according to the embodiment of the present invention may be used in the fluorescent lamp or halogen lamp, etc. 
       FIG. 3  is a circuit diagram of the LED lighting device using the ballast according to the embodiment of the present invention. 
     As shown in  FIG. 3 , the rectifier  100  of the LED device  200  using the ballast according to the embodiment of the present invention may include a first rectifier  101  and a second rectifier  102  which rectify the current power input from the ballast  10 . Further, the current driving unit  110  receives the output power of the rectifier  100  and controls the power which is transmitted from the ballast  10  to the LED unit  130 . The current driving unit  110  transmits current which has the magnitude greater than that of the output current of the rectifier  100  to the LED unit  130 . The current driving unit  110  may include a current boost converter which includes a capacitor  111 , a diode  112 , an inductor  113 , and a switch  114 . The diode  112  may be replaced by a switching element which operates complementarily to the switch  114 . The filter  120  may be implemented by a capacitor unit  121  including at least one capacitor, and the LED unit  130  may include at least one LED device. 
     Hereafter, the rectifier  100  of the LED lighting device  200  using the ballast according to the embodiment of the present invention will be described. 
     The LED lighting device to which the rectifier  100  is applied according to the embodiment of the present invention will be briefly described. 
       FIG. 4 a    shows that both ends of a lamp are connected to a choke magnetic ballast by using a two-terminal short-circuit rectifier.  FIG. 4 b    shows that both ends of the lamp are connected to a rapid start magnetic ballast by using the two-terminal short-circuit rectifier.  FIG. 4 c    shows that both ends of the lamp are connected to a rapid start electronic ballast by using a rectifier into which a resistor of filament has been inserted.  FIG. 4 d    shows that both ends of the lamp are connected to the rapid start electronic ballast by using a rectifier inserted into the both ends of the lamp respectively.  FIG. 4 e    shows an equivalent circuit to that of  FIG. 4   d.    
     As shown in  FIG. 4 a   , for the purpose of obtaining a discharge voltage, a choke magnetic ballast  11  makes use of a choke (starter) which becomes an open state or short-circuit state at a particular point of time. In the choke magnetic ballast  11  using a common rectifier  21 , a starter path of an auxiliary path  3  required for discharging is not separated. Therefore, since a voltage source path of a main path  2  is not separated from the starter path of the auxiliary path  3 , the choke required for alternately opening and short-circuiting may malfunction. 
     As shown in  FIG. 4 b   , in the rapid start magnetic ballast  12 , filament is preheated by a first transformer T 1  and a second transformer T 2 , and the characteristics of a current source is obtained by using the first and second transformers T 1  and T 2 . However, when the main path  2  and the auxiliary path  3  are short-circuited, excess current is generated by the transformer, thereby causing problems in stability and reducing the efficiency of the ballast. 
     As shown in  FIG. 4 c   , in the rapid start electronic ballast  13 , when the resistance value of filament, i.e., about 3Ω (R 1  to R 4 ) is inserted into the rectifier  23 , all the problems caused by the short-circuit of the main path  2  and the auxiliary path  3  can be overcome. However, the power is consumed by the resistors R 1  to R 4  of the current source path, i.e., the main path  2 , so that the efficiency of the lighting device is reduced. 
     Meanwhile, when the rectifier  24  including the first and second rectifiers on both sides of the LED lamp is applied to the magnetic ballast, the starter path or the transformer path is separated, thereby solving the problem caused by the short-circuit. However, as shown in  FIG. 4 d   , when the rectifier  24  including the first and second rectifiers is applied to the rapid start electronic ballast  13 , a parallel capacitor Cp included in a resonator of the electronic ballast  13  is removed, so that the resonance characteristics of the ballast  13  are changed. Accordingly, it is not possible for the ballast to normally operate. Referring to  FIG. 4 e   , though the rectifier  24  transmits the power received from the ballast  13  to the driving unit or LED unit, the driving unit or LED unit cannot transmit the power to the rectifier  24 . Therefore, there occurs an effect that the auxiliary path  3  is isolated and this is beneficial to the magnetic ballast. However, since the auxiliary path  3  is opened in the electronic ballast  13  and there occurs an effect that the parallel capacitor Cp is removed, so that it is expected that the ballast may malfunction due to the resonator change. 
     In the meantime, though not shown in  FIGS. 4 a  to 4 e   , with regard to some of program start electronic ballasts, when the filament is short-circuited, a voltage is not sensed in the filament, so that LED unit is turned on later or is never turned on. 
       FIG. 5  shows the rectifier according to the embodiment of the present invention, which is capable of solving the problems of the rectifiers shown in  FIGS. 4 a    to  4   e.    
     Referring to  FIGS. 3 and 5 , bridge diodes D 11  to D 14  of the first rectifier  101  and bridge diodes D 21  to D 24  of the second rectifier  102  have the same wiring (connection direction of the diode, etc.) combination with respect to a first connection terminal CT 1  and a second connection terminal CT 2 , respectively, which receive the power from the ballast. This intends to cope with the fact that the connection terminals or electrodes are optionally connected to each other in the general lighting device. Also, the rectifier  100  according to the embodiment of the present invention may include a first electrode J 1 , a second electrode J 2 , a third electrode J 3 , and a fourth electrode J 4 . 
     As shown in  FIGS. 3 and 5 , when the alternating current power of the ballast including four or two electrodes is input through the first to fourth electrodes J 1  to J 4 , the first rectifier  101  and the second rectifier  102  output the full wave rectified voltage to the current driving unit  110 . In the bridge diode combination (D 11  to D 14  and D 21  to D 24 ), it is preferable to use a high-frequency diode for processing the alternating current power of a frequency several hundred times as much as a commercial electric power output from the ballast. 
     Also, when the rectifier  100  according to the embodiment of the present invention is connected to the magnetic ballast, the auxiliary path for preheating the starter or filament of the ballast is removed. When the rectifier  100  is connected to the electronic ballast, a circuit connecting the auxiliary path is configured. For this, the rectifier  100  according to the embodiment of the present invention includes a first impedance Z 1 ( f ) which is connected in parallel to the first electrode J 1  and the second electrode J 2 , and a second impedance Z 2 ( f ) which is connected in parallel to the third electrode J 3  and the fourth electrode J 4 . The impedance values of the first impedance Z 1 ( f ) and the second impedance Z 2 ( f ) may be changed depending on the input frequency f. 
       FIGS. 6 a  to 6 d    are circuit diagrams showing concrete circuit types of the rectifier  100  in accordance with the embodiment of the present invention. 
     Referring to  FIG. 6 a   , the first impedance Z 1 ( f ) and the second impedance Z 2 ( f ) may be implemented by a first filament capacitor Cf 1  and a second filament capacitor Cf 2  respectively. Therefore, the first filament capacitor Cf 1  and the second filament capacitor Cf 2  are opened at a low frequency and are short-circuited at a high frequency. Since the magnetic ballast uses a low frequency signal of about 50 to 60 Hz and the electronic ballast uses a high frequency signal greater than 20 KHz, the auxiliary path is opened in the magnetic ballast using the low frequency signal and is short-circuited in the electronic ballast using the high frequency signal. It is preferable that the capacitances of the first and second filament capacitors Cf 1  and Cf 2  are sufficiently greater than the capacitance of the parallel capacitor Cp of the electronic ballast. Thus, as viewed from the auxiliary path, the impedance by the first and second filament capacitors Cf 1  and Cf 2  has a negligible size. Since the capacitance of the parallel capacitor Cp of a general electronic ballast is approximately 5 nF, it is recommended that the first and second filament capacitors Cf 1  and Cf 2  have a capacitance greater than 30 nF. 
     Referring to  FIG. 6 b   , the first impedance Z 1 ( f ) and the second impedance Z 2 ( f ) may be implemented by a first switch SW 1  and a second switch SW 2  respectively. 
     When the magnetic ballast is connected to the lighting device, both ends of the first and second switches SW 1  and SW 2  are opened, and when the electronic ballast is connected to the lighting device, both ends of the first and second switches SW 1  and SW 2  are short-circuited. Accordingly, the on/off of the first and second switches SW 1  and SW 2  is set in advance in accordance with the kind of the ballast, the lighting device according the embodiment of the present invention is compatible with all of the magnetic ballast and electronic ballast. Also, the rectifier may further include a circuit which senses the output frequency of the ballast and changes the state of the switch. The on/off operation of the first and second switches SW 1  and SW 2  may be controlled by a control voltage Vcon. Meanwhile, for the purpose of fast switching, the first and second switches SW 1  and SW 2  may be transistors, and specifically, may be MOS field-effect transistors (MOSFET) or bipolar junction transistors (BJT). 
     Referring to  FIG. 6 c   , the first impedance Z 1 ( f ) and the second impedance Z 2 ( f ) may be implemented by a first variable resistor VR 1  and a second variable resistor VR 2  respectively. 
     When the magnetic ballast is connected to the lighting device, the first and second variable resistors VR 1  and VR 2  have a very high resistance value in such a manner that both ends of the variable resistor are close to the open state. When the electronic ballast is connected to the lighting device, the first and second variable resistors VR 1  and VR 2  have a very low resistance value in such a manner that both ends of the variable resistor are close to the short-circuit state. Therefore, the resistance values of the first and second variable resistors VR 1  and VR 2  are set in advance in accordance with the kind of the ballast, the lighting device according the embodiment of the present invention is compatible with all of the magnetic ballast and electronic ballast. Also, the rectifier may further include a circuit which senses the output frequency of the ballast and changes the resistance value of the variable resistor. The resistance values of the first and second variable resistors VR 1  and VR 2  may be implemented by the resistor and switch. The switch can be controlled by the control voltage Vcon. 
     Referring to  FIG. 6 d   , the first impedance Z 1 ( f ) and the second impedance Z 2 ( f ) may be implemented by a first resonator and a second resonator. 
     As shown in  FIG. 6 d   , the first resonator may be a band pass filter including two inductors Lf 1  and Lf 2  and one capacitor Cf 1 . The second resonator may be a band pass filter including two inductors Lf 3  and Lf 4  and one capacitor Cf 2 . 
     When the magnetic ballast is connected to the lighting device, the first resonator and second resonator set a pass band frequency in such a manner that both ends of the capacitors Cf 1  and Cf 2  are opened. When the electronic ballast is connected to the lighting device, the first resonator and second resonator set a pass band frequency in such a manner that both ends of the capacitors Cf 1  and Cf 2  are short-circuited. Specifically, since the electronic ballast operates at a frequency of 30 to 75 KHz, the first resonator and second resonator may be implemented by an LC resonator having a low selectivity in such a manner as to have a low impedance in a band of 30 to 75 KHz. Also, a method for varying the capacitors Cf 1  and Cf 2  of the first and second resonators may be used in order to control the pass band. The capacitor may be varied by a plurality of the capacitors and switches. 
     In summary, the rectifier  100  according to the embodiment of the present invention includes two rectifiers  101  and  102 . When the magnetic ballast is connected to the lighting device, each of the rectifiers  101  and  102  operates in such a manner as to cause the main path and the auxiliary path to be opened, and when the electronic ballast is connected to the lighting device, each of the rectifiers  101  and  102  operates in such a manner as to cause the main path and the auxiliary path to be short-circuited. Also, the circuit including the first and second impedances Z 1 ( f ) and Z 2 ( f ) of  FIGS. 6 a  and 6 d    is not necessarily implemented independently and may be implemented to include two or more circuits. 
       FIGS. 7 a  to 7 d    are block diagrams of the LED lighting device including the rectifier in accordance with the embodiment of the present invention. 
     As shown in  FIGS. 4 a  and 7 a   , when the common rectifier  21  is applied to the choke magnetic ballast  11 , the starter path  3  required for discharging the voltage is not separated from the current source path  2 , so that there is a possibility of malfunction. However, the rectifier  100  according to the embodiment of the present invention receives the low frequency signal of the magnetic ballast, so that the first and second impedances Z 1 ( f ) and Z 2 ( f ) are opened. Accordingly, the starter path  3  is isolated, and thus, the possibility of malfunction is removed. 
     As shown in  FIGS. 4 b  and 7 b   , in a case where the common rectifier  22  is applied to the rapid start magnetic ballast  12 , when the current source path  2  and the auxiliary path  3  are short-circuited, excess current is generated, thereby causing problems in stability and reducing the efficiency of the ballast. However, since the rectifier  100  according to the embodiment of the present invention receives the low frequency signal of the magnetic ballast, the magnitude of the filament current becomes closer to 0. Accordingly, it is possible to solve the problems in stability of the lighting device and the reduction of the efficiency of the ballast. 
     As shown in  FIGS. 4 c  and 7 c   , when the common rectifier  23  is applied to the rapid start magnetic ballast  13 , most of the problems caused by the short-circuit are overcome. However, the power is consumed in the resistor of the current source path  2 , so that the efficiency of the lighting device is reduced. However, the rectifier  100  according to the embodiment of the present invention receives the high frequency signal of the electronic ballast, so that the first and second impedances Z 1 ( f ) and Z 2 ( f ) are short-circuited and the auxiliary path is connected. Further, since no resistor is used, there is no power loss and the efficiency of the lighting device can be enhanced. 
     Meanwhile, with regard to an instant start electronic ballast  14  with a two-terminal output, as shown in  FIG. 7 d   , even when the rectifier  100  according to the embodiment of the present invention is connected to a fluorescent lamp ballast with the two-terminal output, the rectifier  100  is not influenced by the short-circuit. Accordingly, the lighting device according the embodiment of the present invention is compatible with the ballast with the two-terminal output. 
     In summary, the rectifier  100  according to the embodiment of the present invention is compatible with all of the electronic ballast and magnetic ballast and consumes less power. 
     Next, the current driving unit  110  of the LED lighting device  200  using the ballast according to the embodiment of the present invention will be described. 
     As briefly described above, the LED lighting device using the ballast shown in  FIG. 1  makes use of the voltage converter such as a voltage boost converter or a voltage buck converter in order to supply the constant power to the LED unit. However, since the power source which transmits the power from the ballast to the LED lighting device is not a voltage source but a current source, there is a limit to control the power through use of the voltage converter. Therefore, in the LED lighting device using the ballast shown in  FIG. 1 , the filter which converts the current source input from the ballast into the voltage source is inserted between rectifier and the voltage converter. When the amount of the current input from the ballast is increased, the voltage converter reduces the amount of the current output so as to transmit the constant power to the LED unit, so that the voltage which is applied to the capacitor of the filter is more increased. Consequently, the LED lighting device using the common voltage converter has a problem that the voltage which is applied to the capacitor of the filter rises excessively. 
     For the purpose of solving the above-mentioned problem, as shown in  FIG. 3 , the current driving unit  110  of the LED lighting device using the ballast in accordance with the embodiment of the present invention may use the current boost converter which controls the current power which is applied from the rectifier  100 . 
     As shown in  FIG. 3 , the current driving unit  110  receives the rectified signal output from the rectifier  100  and controls the power which is transmitted from the ballast to the LED unit. That is, the current driving unit  110  outputs a rated voltage and current signal for the LED unit  130  by using the ballast output. The current driving unit  110  includes a first terminal N 1  and a second terminal N 2  and transmits/receives the current signal rectified by using the rectifier  100  through the first terminal N 1  and the second terminal N 2 . The current driving unit  110  may include the current boost converter which receives the current power from the rectifier  100  and supplies the current power to the LED unit  130 . The current driving unit  110  includes the switch  114  which electrically connects or disconnects the transmission of some of the received ballast output power to the LED unit, the diode  112  which allows the current to continuously flow to the LED unit when the switch is in an off-state, the capacitor  111  and the inductor  113  which store and release the energy in a reciprocal manner. The switch  114  may be implemented by a transistor. Also, though it has been described in the embodiment of the present invention that the current flows continuously to the LED unit  130  by using the diode  112 , the component allowing the current to flow continuously to the LED unit  130  is not necessarily limited to the diode  112 , and it is enough as long as the component is a switching element which operates complementarily to the switch  114 . The switching element may include MOS field-effect transistors (MOSFET) or bipolar junction transistors (BJT), etc. 
     As shown in  FIG. 3 , in the current driving unit  110 , the capacitor  111  is connected between the first terminal N 1  and the second terminal N 2 , and the cathode of the diode  112  is connected to the first terminal N 1  and the anode of the diode  112  is connected to an end of the switch  114  and an end of the LED unit  130 . One end of the inductor  113  is connected to the first terminal N 1  and the other end of the inductor  113  is connected to the positive terminal or negative terminal of the LED unit  130 . One end of the switch  114  is connected to the second terminal N 2  and the other end of the switch  114  is connected to the positive terminal or negative terminal of the LED unit  130 . 
       FIG. 8 a    shows the LED lighting device using the ballast including a current buck converter.  FIG. 8 b    shows the LED lighting device using the ballast including the current boost converter in accordance with the embodiment of the present invention. 
     A current buck driver  109  using the current buck converter shown in  FIG. 8 a    and the current driving unit  110  including the current boost converter shown in  FIG. 8 b    are in common with each other in that they basically receive the current power and transmit the power to loads. However, the current buck driver  109  shown in  FIG. 8 a    controls such that the magnitude of the current which is transmitted to a load unit is less than the magnitude of the current which is input to the current buck driver  109 . Therefore, the magnitude of the voltage which is transmitted to the load unit is increased so as to transmit the constant power to the load unit. If the load unit is an LED device, a high voltage higher than 60 V may be applied to the LED device. In some regions like US, etc., tempered glass is required for ensuring stability when the high voltage higher than 60 V is applied to the LED device. As a result, transparency becomes lower, and thus, optical efficiency is decreased. However, in the current driving unit  110  including the current boost converter, which is contrary to the above-mentioned current buck driver  109 , the current which is applied to the LED device is increased, so that the magnitude of the voltage which is applied to the LED device is reduced. Accordingly, the problem of the above-described current buck driver  109  does not occur. In other words, the current driving unit  110  including the current boost converter in accordance with the embodiment of the present invention has a better stability for the voltage than that of the current buck driver  109 , a low cost, and a high optical efficiency when applied to the lighting device. Also, the ballast is a non-ideal current source having the parallel capacitor Cp. The current buck structure which is switched in parallel with the current source input discharges the capacitance of the parallel capacitor Cp, so that the efficiency of the lighting device may be reduced. Therefore, it is advantageous to apply the current boost structure which is not switched in parallel with the current source input. 
     Referring to  FIG. 3 , the filter  120  includes the capacitor and smoothes the voltage and current controlled by the current driving unit  110 , and then supplies to the LED unit  130 . The filter  120  may include the capacitor unit including at least one capacitor. It is recommended that the filter  120  is designed to have a time constant sufficient to smooth the power including a high-frequency ripple which is supplied from the current driving unit  110 , thereby preventing the LED from flickering due to the change of the current value. 
     The LED unit  130  includes LED devices which emit light by using the voltage and current supplied from the filter  120 . The LED devices included in the LED unit  130  are connected in series or in parallel and lighted. 
       FIG. 9  is a circuit diagram of the LED lighting device which further includes a controller controlling the current flowing through the LED unit and uses the ballast in accordance with the embodiment of the present invention. 
     Referring to  FIG. 9 , the current driving unit  110  includes the capacitor  111 , the diode  112 , the inductor  113 , and the switch  114  of  FIG. 3 , and further includes a controller  115  and a current sensor  116 . The controller  115  controls the on/off of the switch  114 . The current sensor  116  senses the current flowing through the LED unit  130  and transmits the magnitude of the current to the controller  115 . 
     That is, regarding various ballasts having different device values, it is possible to control such that the magnitude of the power consumed by the LED unit  130  is constant by controlling the duty of the switch  114  of the current driving unit  110 . Specifically, the controller  115  receives the magnitude of the current flowing through the LED unit  130  from the current sensor  116  and controls the on/off of the switch  114 . Rated voltage and current required by the LED part  130  can be supplied in a manner that when the value of the current flowing through the LED unit  130  is greater than a predetermined current value, the duty of the switch  114  is increased, and when the value of the current flowing through the LED unit  130  is greater than a predetermined current value, the duty of the switch  114  is decreased. Therefore, regardless of the device characteristics of the ballast, since the constant power can be supplied to the LED unit  130  through the on/off control of the switch  114 , the lighting device according the embodiment of the present invention is compatible with various ballasts. Also, since the power required by the LED unit  130  is supplied, it is possible to fundamentally remove the problems that energy is accumulated in the filter  120 , the LED brightness cannot be controlled, etc., due to the fact that the output power of the ballast does not match the power consumed by the LED lighting device, thereby preventing chips or passive devices, for example the filter  120  from being damaged. 
     The rectifier  100  according to the embodiment of the present invention includes two rectifiers having the filament capacitor respectively, so that the lighting device according the embodiment of the present invention is compatible with all of the magnetic ballast and the electronic ballast. 
       FIG. 10  shows a current driving unit according to another embodiment of the present invention. 
     Referring to  FIG. 10 , a current driving unit  131  of an LED lighting device  201  according to the another embodiment of the present invention includes a transformer circuit. 
       FIG. 11 a    shows a waveform of a specific signal of the current driving unit including the current boost converter.  FIG. 11 b    shows a waveform of a specific signal of the current driving unit using a transformer. 
     Referring to  FIGS. 11 a  and 11 b   , it can be understood that the current ic and voltage Vc which are applied to the capacitors C 1  and C 2  when the switch is in an off-state are the same as the current ic and voltage Vc which are applied to the capacitors C 1  and C 2  when the switch is in an on-state. 
     As shown in  FIGS. 10, 11   a , and  11   b , the current driving unit  131  including the transformer  212  controls the power which is transmitted from the ballast  10  to the LED unit  130 . Depending on the turns ratio of the transformer  212 , the current driving unit  131  of the LED lighting device  201  according to the another embodiment of the present invention is able to transmit current having a magnitude greater than that of the output current of the rectifier  100  to the LED unit  130 . The current driving unit  131  according to the another embodiment of the present invention may include a switch  214 , a diode  213 , a capacitor  211 , and the transformer  212 . The switch  214  connects or disconnects electrically the transmission of some of the received ballast output power to the LED unit  130 . The diode  212  allows the current to continuously flow to the LED unit  130  when the switch  214  is in an off-state. The capacitor  211  stores or releases the energy when the switch  214  is in an on or off-state. The transformer  212  separates electrically the ballast  10  from the LED unit  130 . 
     Since the current driving unit  131  according to the embodiment of the present invention isolates the ballast  10 , i.e., the first side of the transformer  212  from the LED unit  130 , i.e., the second side of the transformer  212  by using the transformer  212 , the stability of the LED lighting device  201  can be improved. The LED lighting device  201  including the current driving unit  131  using the transformer also adjusts the duty of the switch  214 , thereby supplying rated voltage and current required by the LED part  130   
     As described above, according to the embodiment of the present invention, it is possible to easily implement the LED lighting device using the ballast. That is, the power which is transmitted from the ballast is transmitted as the power required by the LED unit through the current driving unit, so that the passive devices or chips of the lighting device can be protected. Further, the rated voltage and current are supplied to the LED unit and loads applied to other passive devices or chips can be reduced. Accordingly, the LED lighting device is compatible with any conventional ballast according to the power control of the controller, and it is possible to stably supply the power and to protect the circuit element. 
     The features, structures and effects and the like described in the embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Furthermore, the features, structures, effects and the like provided in each embodiment can be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, contents related to the combination and modification should be construed to be included in the scope of the present invention. 
     Although embodiments of the present invention were described above, these are just examples and do not limit the present invention. Further, the present invention may be changed and modified in various ways, without departing from the essential features of the present invention, by those skilled in the art. For example, the components described in detail in the embodiments of the present invention may be modified. Further, differences due to the modification and application should be construed as being included in the scope and spirit of the present invention, which is described in the accompanying claims.