Entity

Time filter

Source Type

Hengyang, China

Yang H.-A.,National Chiao Tung University | Yang W.-H.,National Chiao Tung University | Chen K.-H.,National Chiao Tung University | Wey C.-L.,National Chiao Tung University | And 5 more authors.
Digest of Technical Papers - IEEE International Solid-State Circuits Conference | Year: 2016

Lighting flicker, a rapid and repeated change over time in the brightness of light, has long been known to cause illness in humans that ranges from headaches to seizures. Thus, [1] has specified the dimming frequency, fDIM, larger than 3kHz to achieve a no-observable-effect flicker level. State-of-the-art LED drivers employ the SIMO topology with four channels in Fig. 12.7.1, to deliver energy to each LED using the time-multiplexing (TM) control technique [2-4], in which the luminance is controlled by the dimming signals. Two major shortcomings for such approaches are: (1) Sequential dimming signals; and (2) Current cross-regulation (CCR) effects. In [2], the LED drivers with TM control result in only 9b color resolution at the dimming frequency of 1.5kHz, which may cause flicker hazard. Besides, the complete white-red-green-blue (WRGB) sequence needs a total of four switching periods to light up the 4 LEDs separately. On the other hand, due to inherent rising and falling delay of the hysteretic current control (HCC) circuit, tdr and tdf respectively, the CCR effect seriously affects the accuracy of the controller when the inductor current slope is varied. For example, with L=15μH, VIN=20V, VR=2.5V, VG=3.5V, tdr=300ns and tdf=250ns, the SIMO will result in 4% CCR between Iavg,R and Iavg,G when the average LED current is 1A. More specifically, with the same color in the sequence, voltage regulation may be disregarded when regulated constant current through the sensing resistor RSEN is used as a negative feedback control. However, when different colors are in sequence, where VO, =VR, VG, VB, or VW, are different, large voltage cross-regulation (VCR) across the RSEN occurs and so does the CCR. The CCR effects become an open question for enhancing LED current accuracy. For alleviating the CCR effect, the discontinuous conduction mode (DCM) has been applied for TM control in [3]. However, with the limited output current in DCM, low output power resulted and large output capacitors were required to suppress the VCR. © 2016 IEEE. Source


Lai S.-C.,Nan Hua University | Liu C.-H.,National Cheng Kung University | Wang L.-Y.,National Cheng Kung University | Chen S.-H.,National Chiao Tung University | Chen K.-H.,National Chiao Tung University
IEEE Transactions on Circuits and Systems I: Regular Papers | Year: 2015

This paper presents a novel algorithm and architecture design for 18-band quasi-class-2 ANSI S1.11 1/3 octave filterbank. The proposed design has several advantages such as lower group delay, lower computational complexity, and lower matching error. The technique we developed in this paper can be summarized as follows: 1) a simple low-pass filter (LPF) and discrete cosine transform (DCT) modulation are utilized to generate a uniform 9-band filterbank first, and then all elements of ${\rm z}-1 are replaced by all-pass filters to obtain a non-uniform filterbank; 2) a fast recursive structure and variable-length algorithm is further developed to efficiently accomplish DCT modulation. Thus, the spectrum of LPF can be easily spanned and flexibly extended to the location of the desired central frequency; 3) after employing the multi-rate algorithm, an 18-band non-uniform filterbank is generated from two 9-band sub filterbanks by following the proposed design steps and parameter determinations. Compared with the latest Liu 's quasi-class-2 ANSI S1.11 design, the proposed method-I (Proposed-I) totally has 72.8% reduction for multiplications per sample, 11.25-ms group delay, and 59 additions decreased per sample. Moreover, the maximum matching error of the proposed method-II (Proposed-II) is averagely equal to 1.79 dB much smaller than that of the latest Wei 's design. For the proposed variable-length DCT modulation, only 2 adders, 2 multipliers, 2 multiplexers, and 5 registers are required for hardware implementation after applying VLSI retiming scheme. Overall, the proposed filterbank design would be a new solution for future applications in the area of hearing aids. © 2004-2012 IEEE. Source


Li A.-K.,National Cheng Kung University | Lei S.-F.,National Cheng Kung University | Tsai W.-K.,Industrial Technology Research Institute of Taiwan | Lai S.-C.,Nan Hua University
Proceedings - IEEE International Symposium on Circuits and Systems | Year: 2014

This paper proposed a novel fast algorithm and common structure design of analysis and synthesis quadrature mirror filterbanks (AQMF, SQMF) on the spectral band replication (SBR) in digital radio mondiale (DRM). Based on recent Lai et al.'s concept, an extended issue is addressed from the view point of recursively computing the AQMF and SQMF coefficients. The proposed method also combines with the lifting scheme algorithm and canonical signed digit (CSD) multiplication. The results show that the proposed AQMF algorithm has a great improvement on computational complexity. For the recursive kernel computation (N=64), the proposed method has, respectively, 46.38% of multiplication reductions and 20.46% of addition reductions which can cover the shortcoming of the proposed SQMF. The overall complexity of the proposed algorithm (N=64) requires 1984 real multiplication and 128 CSD multiplication, 4704 real addition and 192 CSD addition, and 113 coefficients. It would be more efficient and more suitable than previous works for DRM applications. © 2014 IEEE. Source


Juan Y.-H.,National Cheng Kung University | Huang H.-Y.,National Taipei University | Lai S.-C.,Nan Hua University | Juang W.-H.,National Cheng Kung University | And 3 more authors.
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2016

This paper proposes a recursive discrete Fourier transform (RDFT) foreground digital calibration method for successive approximation (SAR) analog-To-digital converters (ADCs). This calibration method can lower the harmonic distortion caused by capacitor mismatch and dc offset of comparators to improve the resolution and performance of ADCs. Capacitor mismatch results in a digital-To-Analog converter (DAC) capacitor array that is unequal to 2n. RDFT can be adopted to evaluate the real radixes of a DAC capacitor array with a new digital output to compensate for the error caused by capacitor mismatch. Furthermore, the calibration technique can eliminate the dc offset error of a comparator circuit. The proposed novel digital calibration method that utilizes RDFT instead of the traditional fast Fourier transform has the advantages of variable transform length, lower complexity, faster computation, and less hardware cost. The analog block of SAR ADC with RDFT is implemented in the TSMC 0.18-μm standard CMOS process with a 200-kS/s sampling rate to validate the proposed method. Simulation results show that the total harmonic distortion (THD) is 64.97 dB before calibration, whereas a THD of 73.05 dB can be achieved after calibration. In addition, the effective bit numbers are 9.98 and 11.26 b before and after calibration, respectively. © 2004-2012 IEEE. Source


Chen S.-H.,Nan Hua University | Lee J.-M.,National Kaohsiung Marine University | Liu H.-H.,National Taipei University | Wang H.-C.,National Chung Hsing University | Ye C.-Y.,Overseas Chinese University
Health Policy and Planning | Year: 2011

This paper empirically identifies cross-price elasticities of betel nut and cigarette consumption in Taiwan based on the Central Bureau of Statistics demand model. It compares reduction of cigarette consumption as a result of the proposed Betel Nut Health Tax with reduction of betel nut consumption as a result of the Tobacco Health and Welfare Taxes levied in 2002 and 2006, in order to determine which tax is most effective. Results from a simulated comparative analysis indicate that the Betel Nut Health Tax reduces cigarette consumption to a much greater extent than the Tobacco Health and Welfare Taxes reduce betel nut consumption. © 2010 The Author. Source

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