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1 (JBE Vol. 21, No. 5, September 2016) (Regular Paper) 21 5, (JBE Vol. 21, No. 5, September 2016) ISSN (Online) ISSN (Print) LED a), b) Study of a LED Driver for Extension of Color Gamut Dong-Seok Shin a) and Chan-Soo Park b) LED Hybrid LED. Hybrid LED LED. CC PWM. RGB LED, 2%. CIE1931.,. Abstract This paper proposes a hybrid LED driving circuit and its control method for extension of the color gamut of LED. The proposed hybrid LED driving circuit provides the constant current by switching regulation in the high current and by linear regulation in the low current through LED. Furthermore, the magnitudes of the high current and low current were controlled by CC(Continuous Current) control method and PWM(Pulse Width Modulation) control method, respectively. We experimentally confirmed that the current through RGB LED is linearly controlled to 2% maximum current ratio by varying PWM in the proposed driving circuit and control method. As a result of the measurement of the output light color in CIE1976 chromaticity coordinates, we confirmed that the color, which not be expressed by the existing method, uniformly expressed. We confirmed that the color, which can not be expressed by the existing method, was uniformly output and verified that the color gamut was expanded by the low current controlled by the proposed driving circuit and control method. Keyword : Color gamut, LED driver, Hybrid, Dimming, Low Luminous Intensity a) (Division of Electrical and Electronic Engineering, Kangwon National University) b) (Mobile Communication Division, Samsung Electronics) Corresponding Author : (Chan-Soo Park) polar97@naver.com Tel: ORCID: Manuscript received February 17, 2016; Revised September 20, 2016; Accepted September 20, 2016.

1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). HD(High Definition), UHD(Ultra High Definition) 2018 KBS(Korean Broadcasting System) UHD. UHD 120., [1,2]. LED [3].

2 1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). HD(High Definition), UHD(Ultra High Definition) 2018 KBS(Korean Broadcasting System) UHD. UHD 120., [1,2]. LED [3]. LED. LED, LED. LED 1 [4]. LED.. 2 CIE1931 HD UHD LED [5,6]. LED,.,. 2 CIE1931 Fig. 2 Color gamut in CIE1931 color spaces. Hybrid LED 1. White LED - Fig. 1. Relative luminous flux versus forward current curve of white LED RGB LED, Hybrid LED,. Hybrid LED 3. MOSFET. LED,

3 (JBE Vol. 21, No. 5, September 2016) 3. Hybrid LED Fig. 3. Block diagram of a proposed method for hybrid LED actuation circuit. MOSFET (Saturation Region), MOSFET (Resister Region) VCR(Voltage Control Resister). 1. Hybrid LED Hybrid LED LED. Hybrid LED. 1.1 Hybrid LED 4. PWM 1 on/off LED PWM. PWM 1 on LED MOSFET - RDS. MOSFET VCR - VGS RDS LED 4. LED Fig. 4. Hybrid LED driving circuit for the low current through LEDs

4 1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). LED 5. PWM 1 Vref V(+) OP-AMP (+). PWM 1 on Vref, off 0. V(+) LED Vsense OP-AMP. 5. Hybrid LED Fig. 5. Waveform of hybrid LED driving circuit at low current control 1.2 Hybrid LED 6. LED CC. LED, LED. L LED, L LED. 7. VCO (Voltage Control Oscillator) 6. Fig. 6. Hybrid LED driving circuit for high current through LEDs

5 (JBE Vol. 21, No. 5, September 2016). VCO VO PWM 2 DC. PWM 2 VO,. 8., RLED, LED VF-string LED, LBUCK MOSFET - RDS [7]. Rsense. 7. hybrid LED Fig. 7. Waveform of hybrid LED driving circuit at high current control 2. Hybrid LED LED LED. LED, LED. Hybrid LED kh PWM. LED. PWM 1 on LED Hybrid LED 8. PWM on Hybrid LED Fig. 8. Equivalent circuit of hybrid LED driving circuit in PWM on time PWM 3kHz, on LED 100 ma LED 9. LBUCK, RLED, RDS t1. 10 ma on 33.3 μsec 10 μsec 9 LED Fig. 9 Current waveform through LED in the low current control mode

6 1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). (1). sec 10 LED V-I. LED. LED 100 ma, VF 26.5 V RLED 24.6 Ω. LED 100 ma MOSFET RDS 110 Ω. (1) LBUCK 480 μh PWM 10 ma. LED LED. LED IC. 3. Hybrid LED 10. White LED string V-I Fig. 10. Measured V-I curve of white LED string 11 Hybrid LED. LED, CC SUPERTEX HV9910B IC. OP-AMP ST LM358 MOSFET. MOSFET TOSHIBA 2SK Hybrid LED Fig. 11. Designed hybrid LED driving circuit

7 (JBE Vol. 21, No. 5, September 2016) HV9910 OP-AMP LM358 MOSFET ONsemiconductor MUX MC14052B Hybrid LED Hybrid LED. 13 LED 500 ma MOSFET VGS LED. 250 khz 100 map-p. 12 Hybrid LED 1. MARTIN Light Jockey DMX CC LED MOSFET - Fig. 13. LED current waveform and Gate-Source voltage waveform on MOSFET on the CC control in the high current control mode 14, MOSFET Hybrid LED Fig. 12. Experimental environment for hybrid LED driving circuit 1. Table 1. List of the equipments for experiment of hybrid driver FET DS 200 ma/div 20 V/div 2.00 μs/div Equipment Model Manufacturer Oscilloscope Waverunner 104MXI LeCroy Current Probe AP015 LeCroy Chroma Meter CL 200-A KONICA MINOLTA DMX512 Console Light Jockey MARTIN AC/DC Power Supply ES2000S NF 14. CC MOSFET - Fig. 14. Current waveform through MOSFET and Drain-Source voltage waveform on MOSFET on the CC control in the high current control mode

8 1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). MOSFET Saturation on MOSFET - 0 V, off 40 V. FET DS 200 ma/div 10 V/div 200 μs/div 2.2 Hybrid LED Hybrid LED. 15 PWM on, MOSFET VGS RDS LED 100 ma. MOSFET 3.4 V VGS. 16. PWM MOSFET MOSFET - Fig. 16. Current waveform through MOSFET and Drain-Source voltage waveform in MOSFET on the PWM control in the low current control mode 15. PWM LED MOSFET - Fig. 15. Current waveform through LED and Gate-Source voltage waveform in MOSFET on the PWM control in the low current control mode 17 LED Fig. 17 Waveform of the transient current through LED in the low current control mode 16, MOSFET -. MOSFET VCR. MOSFET, 15 VGS Ω, 100 ma. 17 Hybrid LED LED. LED μsec 10 μsec, 3 khz PWM. 18. LED LED Fig. 18. Relative luminous flux and LED current at low current control mode

9 (JBE Vol. 21, No. 5, September 2016) Hybrid LED PWM LED. PWM 1, 2%. LED 1% %, 3.73 %, 2.91 % Target color coordinates Measured color coordinates Color gamut line by used LEDs MacAdam ellipses for 5step 2.3 LED 2. #1 #2 2. LED Table 2. Color coordinates and maximum illuminance of the LED R LED G LED B LED #3 #4 CIE1931 Color coordinates Maximum illuminance (lx) x y #6 #5 Hybrid LED RGB LED, 3. x y 19. CIE1931 Fig. 19. Measured color coordinates on CIE Table 3. Measured color coordinates and illuminance Color Color #1 Color #2 Color #3 Color #4 Color #5 Color #6 x Target value y illuminance DMX512 Control level Measured value Error (%) R G B x y illuminance x y illuminance

1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). Hybrid LED. Hybrid LED MOSFET. MOSFET VCR RDS LED 100 ma, PWM 100 ma. MOSFET khz LED, 250 350 khz 500 ma.

[2] Ultra High Definition Television - Image Parameter Values for Program Production, SMPTE 2036-1, 2007. [3] IT SoC Association, The LED concept and the manufacturing process, IT SoC Magazine, vol.

10 1 : LED (Dong-Seok Shin et al.: Study of a LED Driver for Extension of Color Gamut). Hybrid LED. Hybrid LED MOSFET. MOSFET VCR RDS LED 100 ma, PWM 100 ma. MOSFET khz LED, khz 500 ma. Hybrid LED 80W RGB LED, 10 ma,. x y 1.73 %, 3.73 % 2.91 %. (References) [1] High Efficiency Video Coding, ITU-T H.265, [2] Ultra High Definition Television - Image Parameter Values for Program Production, SMPTE , [3] IT SoC Association, The LED concept and the manufacturing process, IT SoC Magazine, vol. 23, pp , [4] LUXEON Rebel General Purpose White PortfolioPhillips Lumileds, Royal Philips Electronics N.V., Amsterdam, [5] Parameter Values for the HDTV Standards for Production and International Programme Exchange, ITU-R BT.709-5, [6] Parameter Values for Ultra-High Definition Television Systems for Production and International Programme Exchange, ITU-R BT.2020, [7] R. L. Lin and Y. F. Chen, Equivalent circuit model of light-emitting-diode for system analyses of lighting drivers, in Proc. IAS, pp. 1-5, : () : ( ) : s ( ) ~ FPD - ORCID : - :,, : () : ( ) : ( ) ~ : - ORCID : - :,,

09권오설_ok.hwp

09권오설_ok.hwp (JBE Vol. 19, No. 5, September 2014) (Regular Paper) 19 5, 2014 9 (JBE Vol. 19, No. 5, September 2014) http://dx.doi.org/10.5909/jbe.2014.19.5.656 ISSN 2287-9137 (Online) ISSN 1226-7953 (Print) a) Reduction