A novel monolithic white LED driver with dual dimming mode

Liu, Lianxi; Niu, Yue; Zou, Jiao; Zhu, Zhangming; Yang, Yintang

doi:10.1007/s10470-014-0260-x

Cited by 5 publications

(5 citation statements)

References 5 publications

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“…where, I ERR indicates the deviation of LED current between the actual value and the ideal value. The intermediate and the rightmost equation of formula (8) indicate that this deviation is controlled by the circuit's electrical characteristic parameters and does not vary with the LED dimming duty cycle. From the final result of formula (8), the error consists of three items, V os0_ max (T 0 ) K • 2 N −1 , V os (A 1 + 1), q inj_S 12 C 1 .…”

Section: Explanation Of Doc Op1 Gain=k Blockmentioning

confidence: 99%

“…the LED is linearly related to the duty cycle of the input dimming signal. The advantage of PWM is that it reaches high precision and achieves up to 50000:1 contrast [6], nevertheless, this approach suffers from electromagnetic interference (EMI) issues because of its high speed current transition [7], [8]. The other category is analog regulation, which is also called Amplitude Modulation (AM).…”

Section: Introductionmentioning

confidence: 99%

“…Its forward current is regulated linearly by the dimming signal duty cycle. This method can eliminate audio noise completely, reduce EMI, and achieve real brightness adjustment without flicker [8], [9].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A High Accuracy Weak Voltage LED Analog Dimming Method

Zhang

Gao

et al. 2019

IEEE Access

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A weak voltage analog dimming method for high precision light emitting diode (LED) current control with N-Bits analog static offset calibration (N-Bits ASOC), dynamic offset cancellation (DOC) and K-times dimming duty to voltage (KD2V) conversion is presented. The N-Bits ASOC circuit decreases the analog dimming error to V OSMAX /2 N − 1 by pre-calibrating the error amplifier offset. Moreover, through a smart combination of KD2V circuits and DOC amplifier, the KD2V and DOC operational amplifier magnify the dimming reference and LED current sense voltage K-times, respectively, which reduces the residual dimming error K-times without any modification to the LED current sampling resistor. Based on the 0.18µm 5V/40V Bipolar-CMOS-DMOS (BCD) process, experimental results for a cell phone backlighting driver show that the analog dimming I LED error reduces to 30µA at maximum 200mV LED current feedback voltage. This deviation mostly keeps constant through a dimming duty range of 0.5% to 100% and V IN range of 2.7V to 5.5V. Furthermore, a 200-sample measurement data suggests that this method is effective even when dimming duty is smaller than 0.5% for mass production.INDEX TERMS LED analog dimming, pulse width modulation (PWM) dimming, dynamic offset cancellation (DOC), analog static offset calibration (ASOC).

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Section: Explanation Of Doc Op1 Gain=k Blockmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A High Accuracy Weak Voltage LED Analog Dimming Method

Zhang

Gao

et al. 2019

IEEE Access

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“…It has been used in broad applications such as lighting systems, backlighting devices and automotive electronics. In recent years, LED driver technique has been a hot research topic in power electronics applications, and the studies mainly focus on high efficiency [4][5][6][7][8][9], dimming techniques [5,6,[10][11][12][13][14][15], high power [7,16], wide range of input and output voltage [6,16,17] and so on.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, several LED dimming techniques have been used to provide higher efficiency [4], higher dimming linearity [15], higher dimming ratio [11, 13, 22] and faster dimming speed [14]. Nowadays, LED drivers tend to integrate different kinds of dimming techniques to increase the flexibility of the system design [12].…”

Section: Introductionmentioning

confidence: 99%

Fixed‐frequency adaptive off‐time controlled buck current regulator with excellent pulse‐width modulation and analogue dimming for light‐emitting diode driving applications

Liu

Qian

Yang

et al. 2015

IET Power Electronics

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This study presents an ideal synchronous buck current regulator for variety of light-emitting diode (LED) loads from wide input voltage range. By using high-side power switch matched sense, the regulator maintains high current accuracy and high system efficiency. The adjustable current sense threshold provides a full-range analogue dimming and the fast output enable/disable function allows for high-frequency pulse-width modulation (PWM) dimming. In addition, the two dimming methods are easy to implement and have highly linear range. An adaptive off-time control is adopted to regulate an accurate constant current for its fast response and no need for control loop compensation, while its disadvantage of variation of switching frequency is overcome. The proposed circuit has been fabricated with 0.35 μm 40 V bipolar-CMOS-DMOS (BCD) process successfully. The experimental results confirm that the LED driver can operate within 6-40 V input voltage, and can drive a 1-10 output series connected LEDs. The switching frequency is fixed at 500 kHz with a variation of ±2%. The measured system peak efficiency is up to 95% at 1 A LED current and 10 V output voltage. The settling time at the PWM rising edge is <3.5 μs which is well beneficial for fast PWM dimming.

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Effects of Composite LED Light on Root Growth and Antioxidant Capacity of Cunninghamia lanceolata Tissue Culture Seedlings

Liang

Yang

2019

Sci Rep

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We used the 12 th generation of the Cunninghamia (C.) lanceolata tissue culture seedlings, and white light emitting diode (LED) light as control (CK). We applied five composite LED light treatments, red-blue 4:1, 8:1 (4R1B and 8R1B), red-blue-purple 8:1:1 (8R1B1P), and red-blue-purple-green 6:1:1:1, 8:1:1:1 (6R1B1P1G and 8R1B1P1G), to study the effects of light quality on root growth characteristics and antioxidant capacity of C. lanceolata tissue culture seedlings. The results showed that: (1) rooting rate, average root number, root length, root surface area, and root activity were higher with 6R1B1P1G and 8R1B1P1G treatments compared to 4R1B, 8R1B, 8R1B1P and CK treatments; and the root growth parameters under the 8R1B1P1G treatment were as high as 95.50% for rooting rate, 4.63 per plant of the average number of root, 5.95 cm root length, 1.92 cm 2 surface area, and 145.56 ng/(g·h) root activity, respectively. (2) The composite lights of 4R1B, 8R1B, 8R1B1P, 6R1B1P1G, and 8R1B1P1G are beneficial for the accumulation of soluble sugar content (SSC) and soluble protein content (SPC), but not conducive for the increase of free proline content (FPC); the plants under 6R1B1P1G and 8R1B1P1G treatments had higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) activity and lower malondialdehyde (MDA), polyphenol oxidase (PPO) activity. (3) Redundancy analysis showed that POD activity positively correlated with root activity; SPC, SOD and CAT activities positively correlated with root growth parameters; while SSC, MDA content, APX and PPO activities negatively correlated with root growth parameters. These results suggest that the responses of root growth and antioxidant capacity of the C. lanceolata tissue culture seedlings to different light qualities vary. The relationship between root growth parameters and antioxidant capacity was closely related. Red-blue-purple-green was the most suitable composite light quality for root growth of C. lanceolata tissue culture seedlings, and 8:1:1:1 was the optimal ratio, under which the rooting rate, root activity and root growth of tissue culture seedlings peaked.

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A novel monolithic white LED driver with dual dimming mode

Cited by 5 publications

References 5 publications

A High Accuracy Weak Voltage LED Analog Dimming Method

A High Accuracy Weak Voltage LED Analog Dimming Method

Fixed‐frequency adaptive off‐time controlled buck current regulator with excellent pulse‐width modulation and analogue dimming for light‐emitting diode driving applications

Effects of Composite LED Light on Root Growth and Antioxidant Capacity of Cunninghamia lanceolata Tissue Culture Seedlings

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