Patent Publication Number: US-8981659-B2

Title: Input voltage transfer apparatus for light emitting diode lighting system

Description:
TECHNICAL FIELD 
     The present disclosure relates to an input voltage transfer apparatus for a Light Emitting Diode (LED) lighting system. 
     BACKGROUND ART 
     Generally, since LEDs are semiconductor devices, LEDs have long service life, fast lighting speed, low consumption power, and excellent color reproductivity. 
     Moreover, LEDs are robust to impact, and it is easy to miniaturize and thin LEDs. 
     Therefore, lighting systems with LEDs are recently being introduced, and research is continuously being conducted on an LED lighting system that more effectively controls the amount of a current supplied to LEDs. 
     DISCLOSURE OF INVENTION 
     Technical Problem 
     Embodiments provide an input voltage transfer apparatus for an LED lighting system, which turns on a switching element when a zero voltage is inputted as an input voltage, turns on a separate switching element when a non-zero voltage is inputted in a state where the switching element is being turned on, turns on the switching element, which has been turned on when the zero voltage is inputted, for a certain time, and thus can efficiently maintain dimming and prevent flicker from occurring in an LED. 
     Solution to Problem 
     In one embodiment, an input voltage transfer apparatus for an LED lighting system includes: a source voltage storage unit storing a source voltage; a zero voltage switching unit turning on according to the source voltage stored in the source voltage storage unit when a zero voltage is inputted; and a nonzero voltage switching unit turning on according to a current applied thereto through the zero voltage switching unit when a nonzero voltage is inputted, wherein when the nonzero voltage switching unit is turned on, the source voltage storage unit discharges the stored source voltage. 
     In another embodiment, an input voltage transfer apparatus for an LED lighting system includes: a source voltage storage unit storing a source voltage; a zero voltage switching unit turning on according to the source voltage stored in the source voltage storage unit when a zero voltage is inputted; a shutdown signal supply unit receiving the source voltage to supply a shutdown signal for shutting down a control circuit, when the zero voltage is inputted thereto; and a nonzero voltage switching unit turning on according to a current applied thereto through the zero voltage switching unit when a nonzero voltage is inputted, wherein when the nonzero voltage switching unit is turned on, the shutdown signal supply unit is turned off, and the source voltage storage unit discharges the stored source voltage. 
     Advantageous Effects of Invention 
     The input voltage transfer apparatus for an LED lighting system, according to the embodiments, turns on a switching element when a zero voltage is inputted as an input voltage, turns on a separate switching element when a non-zero voltage is inputted in a state where the switching element is being turned on, turns on the switching element, which has been turned on when the zero voltage is inputted, for a certain time, and thus can efficiently maintain dimming and prevent flicker from occurring in an LED. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a circuit diagram illustrating an input voltage transfer apparatus for an LED lighting system, according to an embodiment. 
         FIG. 2  is a diagram showing a waveform of an input voltage which is inputted to an input voltage transfer apparatus for an LED lighting system according to an embodiment. 
         FIG. 3  is a circuit diagram illustrating a modification example of an input voltage transfer apparatus for an LED lighting system according to an embodiment. 
     
    
    
     MODE FOR THE INVENTION 
     Hereinafter, exemplary embodiments of the inventive concept will be described in detail with reference to the accompanying drawings. In adding reference numerals for elements in each figure, it should be noted that like reference numerals already used to denote like elements in other figures are used for elements wherever possible. Moreover, detailed descriptions related to well-known functions or configurations will be ruled out in order not to unnecessarily obscure subject matters of the present invention. 
       FIG. 1  is a circuit diagram illustrating an input voltage transfer apparatus for an LED lighting system, according to an embodiment.  FIG. 2  is a diagram showing a waveform of an input voltage which is inputted to an input voltage transfer apparatus for an LED lighting system according to an embodiment.  FIG. 3  is a circuit diagram illustrating a modification example of an input voltage transfer apparatus for an LED lighting system according to an embodiment. 
     Referring to  FIG. 1 , an input voltage transfer apparatus  200  for an LED lighting system, according to an embodiment, may include a source voltage storage unit  220 , a zero voltage switching unit  210 , a shutdown signal supply unit  230 , and a nonzero voltage switching unit  240 . 
     The source voltage storage unit  220  stores a source voltage VCC transferred through a resistor R 2 , in which state the source voltage storage unit  220  discharges the stored source voltage VCC when the nonzero voltage switching unit  240  is turned on. Herein, the source voltage storage unit  220  includes a first resistor R 4  and a first capacitor C 2 . The resistor R 2  transfers the source voltage VCC to the source voltage storage unit  220 . 
     The zero voltage switching unit  210  is turned on when a zero voltage is inputted through a bridge circuit  100  (Vin during time t0-t1 in  FIG. 2 ), but when a nonzero voltage is inputted through the bridge circuit  100  (Vin during time t1 t2 in  FIG. 2 ), the zero voltage switching unit  210  applies a current to the nonzero voltage switching unit  240 . 
     The zero voltage switching unit  210  includes an n-channel metal oxide semi-conductor (NMOS) transistor Q 1  or an NPN bipolar junction transistor. The resistor R 1  transfers an input voltage Vin. 
     As described above, when the nonzero voltage switching unit  240  is turned on, the source voltage storage unit  220  discharges a stored source voltage VCC, and thus, when a voltage stored in the first capacitor C 2  is shifted to less than a threshold voltage of the NMOS transistor Q 1 , the zero voltage switching unit  210  is turned off. 
     Therefore, when the nonzero voltage is inputted, a turned-off time of the zero voltage switching unit  210  may be adjusted by regulating a time constant R 4 *C 2  of the source voltage storage unit  220 . That is, even when the zero voltage is inputted and then the nonzero voltage is inputted, the zero voltage switching unit  210  is not turned off but is turned on proportional to the time constant R 4 *C 2  and then turned off. Accordingly, even when the zero voltage is inputted and then the nonzero voltage is inputted, the zero voltage switching unit  210  and the nonzero voltage switching unit  240  are simultaneously turned on during the time constant R 4 *C 2  thereby applying a current. 
     The shutdown signal supply unit  230  is turned on by the source voltage VCC that is applied thereto when the zero voltage is inputted, and supplies a shutdown signal SD for shutting down a control circuit  400  to the control circuit  400 . However, when the nonzero voltage switching unit  240  is turned on, the shutdown signal supply unit  230  is turned off and does no longer supply the shutdown signal SD. 
     The shutdown signal supply unit  230  may include a p-channel MOS (PMOS) transistor or a PNP bipolar junction transistor Q 2 . The shutdown signal supply unit  230  may further include a Zener diode Z 1  connected between a base of the PNP bipolar junction transistor Q 2  and a ground. A resistor R 3  transfers the source voltage VCC. 
     When the nonzero voltage is inputted (Vin during time t1 t2 in  FIG. 2 ), the nonzero voltage switching unit  240  is turned on by a current that is applied thereto through the zero voltage switching unit  210 . 
     When the nonzero voltage switching unit  240  is turned on, the source voltage VCC is no longer applied to the source voltage storage unit  220  and the shutdown signal supply unit  230 . Thus, the source voltage storage unit  220  discharges a stored source voltage VCC, and the shutdown signal supply unit  230  does not supply the shutdown signal SD. 
     The nonzero voltage switching unit  240  includes an NMOS transistor or an NPN bipolar junction transistor Q 3 . Resistors R 5  to R 7  transfer a current that is applied by the zero voltage switching unit  210 . A capacitor C 3  prevents a noise signal from being applied. 
     In the input voltage transfer apparatus  200 , the zero voltage switching unit  210  is turned on when the zero voltage is inputted as the input voltage, and then when the nonzero voltage is inputted, the zero voltage switching unit  210  is not immediately turned off but is turned on proportional to the time constant R 4 *C 2  and then turned off, thus more efficiently maintaining dimming. 
     Accordingly the input voltage transfer apparatus  200  can more efficiently maintain dimming, and thus prevent flicker from occurring in an LED. 
     The input voltage transfer apparatus  200  may further include a reverse-current prevention unit  250  that prevents a current from being reversely applied to the zero voltage switching unit  210 . The reverse-current prevention unit  250  includes a diode D 1  that has a cathode connected to a resistor, and an anode connected to the ground. 
     The input voltage transfer apparatus  200  may further include an auxiliary storage unit  260  that stores an applied source voltage VCC while the zero voltage is being inputted and then discharges the stored source voltage VCC while the nonzero voltage is being inputted. The auxiliary storage unit  260  includes a second capacitor C 1 . 
     A modification example  1200  of the input voltage transfer apparatus  200  according to an embodiment will be described below with reference to  FIG. 3 . In describing the modification example  1200 , however, only a difference between the input voltage transfer apparatus  200  and the modification example  1200  will be described below. 
     Referring to  FIG. 3 , the modification example  1200  of the input voltage transfer apparatus  200  includes a shutdown signal supply unit  1230 . The shutdown signal supply unit  1230  includes an NMOS transistor or an NPN bipolar junction transistor Q 12 . The shutdown signal supply unit  1230  may further include a Zener diode Z 11  connected between a base of the NPN bipolar junction transistor Q 12  and a resistor R 12 . A resistor R 13  transfers the source voltage VCC. 
     As described above, the input voltage transfer apparatus for an LED lighting system, according to the embodiments, turns on a switching element when a zero voltage is inputted as an input voltage, turns on a separate switching element when a non-zero voltage is inputted in a state where the switching element is being turned on, turns on the switching element, which has been turned on when the zero voltage is inputted, for a certain time, and thus can efficiently maintain dimming and prevent flicker from occurring in an LED. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.