Browsing by Author "Chiu, Shao-Wei"

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93% Efficiency and 0.99 Power Factor in Pseudo-linear LED Driver
(2016-01-01)
Chiu, Shao-Wei
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Kuo, Chun-Chieh
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Chuang, Kai-Cheng
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Yang, Wen-Hau
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Chen, Ke-Horng
The proposed pseudo-linear LED driver can effectively solve the serious flicker in conventional linear LED driver (LLD). Besides, it has good electromagnetic interference (EMI) performance similar to that in conventional LLD at high AC input voltage. In the meanwhile, it has high power factor (PF) similar to boost switching regulator (SWR) LED driver at low AC input voltage. Furthermore, owing to the combination of line filter and the active full bridge rectifier, the pseudo-linear LED driver has a compact solution and high efficiency. The test chip was fabricated in 0.5 mu m 500V LDMOS process. Experimental results show 93% high efficiency, 6% total harmonic distortion (THD), and 0.99 PF at the power of 7W.
A True-Random-Number-Based Pseudohysteresis Controller for Buck DC-DC Converter in High-Security Internet-of-Everything Devices
(2020-03-01)
Yang, Wen-Hau
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Chiu, Shao-Wei
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Kuo, Chun-Chieh
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Lin, Yen-Ting
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Lai, Yan-Jiun
For high-security Internet-of-Everything (IoE) devices, a true random number (TRN)-based pseudohysteresis controller (PHC) is proposed to avoid both power side-channel attack (PSCA) and power injection attack (PIA) and reduce electromagnetic interference (EMI) without degrading performance of transient response and regulation. In addition, the TRN-based PHC uses an enhanced security randomizer to correctly generate a random number (RN) independent of the input power at the PSCA and PIA and converts the RN into a hysteresis window that constitutes the true random modulation switching frequency. Therefore, the TRN-based PHC ensures proper spread spectrum and low EMI. In addition, fast transient response is maintained due to inherent hysteresis control. Experimental results show that peak EMI noise is reduced from 89.72 to 54.32dBV and meets the specification of EN 55032 Class B even under the PIA interference up to 1 V. Furthermore, in case of 0.2A-to-0.8A load step, the method achieves a recovery time of 7.3 s and an output voltage drop of 53 mV at a switching frequency of approximately 1 MHz, and the peak efficiency is 92.4.
Delay-Lock-Loop-Based Inductorless and Electrolytic Capacitorless Pseudo-Sine-Current Controller in LED Lighting Systems
(2015-12-01)
Chiu, Shao-Wei
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Kuo, Chun-Chieh
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Su, Yi-Ping
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Chen, Ke-Horng
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電控工程研究所
Light-emitting diode lighting system with the proposed pseudo-sine-current controller removes most of the external passive components, which include inductor, electrolytic capacitor, freewheel diode, blocking diode, and the bleeding circuit for Triac dimming control, for low cost and small volume. Delay-lock loop control can ensure the in-phase operation of ac input voltage and current for high power factor (PF) and low total harmonic distortion (THD). In addition, redundant power loss in Triac dimming control is eliminated to get a high efficiency of 85%. Furthermore, a high PF of 0.997 and a low THD of 7.74% are also achieved owing to in-phase line voltage and current.