Jian-Fu Wu

National Cheng Kung University, 臺南市, Taiwan, Taiwan

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Publications (11)7.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A dual-mode electrochemical measurement and analysis system is proposed. This system includes a dual-mode chip, which was designed and fabricated by using TSMC 0.35 µm 3.3V/5 V 2P4M mixed-signal CMOS process. Two electrochemical measurement and analysis methods, chronopotentiometry and voltammetry, can be performed by using the proposed chip and system. The proposed chip and system are verified successfully by performing voltammetry and chronopotentiometry on solutions.
    Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 07/2013; 2013:3265-3268.
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    ABSTRACT: Light-emitting diodes (LEDs) are an efficient source of illumination for displays and backlights, providing extended lifespan, wide color gamut, and excellent dimming capability. The use of pulse-width modulation (PWM) for dimming makes LEDs susceptible to overcurrent, which can shorten the lifespan of the devices. This paper proposes a novel technique to suppress overcurrent in LEDs operating in PWM dimming mode. The proposed LED driver IC was designed in accordance with the TSMC 0.25-μm 60-V BCD fabrication process, and experimental as well as simulation results demonstrate the efficacy of the proposed approach.
    Power Electronics and Drive Systems (PEDS), 2013 IEEE 10th International Conference on; 01/2013
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    ABSTRACT: Heat sinks and cooling fans are currently the most common tools for regulating temperature within the application-specific integrated circuits of electronic products. Unfortunately, fans consume additional power; therefore, effectively monitoring ASIC temperatures and reducing the power consumption of fans are crucial. This study employed built-in thermal sensors to monitor the temperature within the ASIC and a boost DC-DC converter to drive cooling fans and improve power efficiency.
    SICE Annual Conference (SICE), 2012 Proceedings of; 01/2012
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    ABSTRACT: This paper presents an asynchronous boost-type light-emitting diode (LED) driver, integrating an ambient light sensor (ALS), based on a constant off-time control technique. The LED driver automatically regulates the LED current according to the surrounding illumination as sensed by the on-chip ALS. In backlighting applications, the brightness of the light source is adjusted inversely; therefore, we enabled the selection of two modes of operation: illumination and backlighting. The proposed design is capable of reducing power dissipation for both illumination and backlighting applications. For verification, a prototype was fabricated using the TSMC 0.25-μm 60-V bipolar-CMOS-DMOS process with a chip size of 1900μm × 1330μm.
    Electrical Machines and Systems (ICEMS), 2012 15th International Conference on; 01/2012
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    ABSTRACT: The grayscale resolution of liquid crystal displays (LCDs) can be improved by modulating the grayscale of the pixels in LCDs or by dimming the LCD backlight source. Changing the voltage or turned-on time of a pixel to achieve high-resolution grayscale requires either an accurate digital-to-analog converter or a very high frequency pulsewidth modulation (PWM) signal, which increases hardware cost and power consumption. The fast transient response of light-emitting diodes (LEDs) makes them useful as a backlight source for improving the grayscale resolution of an LCD without additional overhead. This paper presents an eight-channel LED backlight driver that can improve conventional dimming control circuits for LCDs. The proposed design was fabricated in a TSMC 0.25-μm 60-V bipolar-CMOS-DMOS process, and the chip area is 2.7 mm$^2$. A dimming ratio of 50 000:1 is achieved with a 500-Hz PWM signal. The maximum power conversion efficiency, including power consumption of the LED current regulators, is 89.3%, when the load is a 12 × 8 LED array, the input voltage is 20 V, and the LED current is set to 25 mA.
    IEEE Transactions on Power Electronics 01/2012; 27(11):4562-4570. · 5.73 Impact Factor
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    ABSTRACT: The current accuracy and power efficiency of a boost white light-emitting-diode (WLED) driver are usually design tradeoffs since the power efficiency is inversely proportional to the reference voltage, whereas the current accuracy is proportional to the reference voltage. Traditionally, a boost WLED driver with high current accuracy and high power efficiency demand a large chip area because mismatch decreases with increasing size. This paper proposes an offset calibration technique to improve both current accuracy and power efficiency while keeping the chip area relatively small. An overvoltage protection (OVP) circuit and an overcurrent protection (OCP) circuit prevent the proposed driver from being damaged due to WLED failure. The design is fabricated in a Taiwan Semiconductor Manufacturing Company 0.25-μm 60-V bipolar-CMOS-double-diffused-MOS process. The measurement results show that the current variation is less than 1% when the input voltage and the number of loaded WLEDs are varied in a wide range. The maximum power conversion efficiency is 86.7% at a 5-V input with four loaded WLEDs. The OVP is 58 V, and the OCP is 2 A.
    Circuits and Systems II: Express Briefs, IEEE Transactions on 05/2011; · 1.33 Impact Factor
  • IEEE Trans. on Circuits and Systems. 01/2011; 58-II:244-248.
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    ABSTRACT: Light-emitting-diodes (LEDs) are commonly used for backlighting and lighting applications. For LEDs to be used as lighting or backlighting sources for vehicles, it is important to simplify the dimming scheme for LED drivers. Since the number of required LEDs varies with application, a single-ended primary-inductor converter (SEPIC) topology is suitable for the LED drivers to operate in a single battery system. In this paper, a SEPIC LED driver with a hybrid dimming scheme is proposed for vehicle lighting and backlighting applications. The proposed scheme reduces the wiring complexity of vehicles and the cost of LED drivers.
    01/2011;
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    ABSTRACT: This paper presents a boost-type light-emitting-diode (LED) driver with an on-chip ambient light dimming for the liquid crystal display (LCD) backlight module in portable electronics. The proposed system integrates an ambient light sensor (ALS) to achieve the function of dimming control. By sensing the surrounding illumination, the LED driver automatically regulates the LED current, and, hence, the power dissipation of LED backlight module can be effectively reduced. As a result, the battery life can be extended.
    01/2011;
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    ABSTRACT: Size and battery life are important issues for portable devices. White light-emitting diodes (WLEDs) have thus replaced cold cathode fluorescent lamps as backlight sources. Since WLEDs are small and highly efficient, a good WLED backlight driver design can reduce the size of portable devices and extend their operation time. This paper proposes a high efficiency boost WLED driver with an integrated Schottky diode. The DC-DC converter structure allows high efficiency and the on-chip compensator and Schottky diode reduce the board area. The driver also enhances the substrate noise immunity. The simulation results show that the substrate noise was reduced from ±1.8 to ±0.8 V. The driver was fabricated in the TSMC 0.25-μm bipolar-CMOS-DMOS process. For a load of six VLEDs at an input voltage of 4.3 V, the power efficiency was 91.6%.
    01/2010;
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    ABSTRACT: Power efficiency is a very important issue for portable electronic devices since it determines the battery life. The backlight module usually accounts for the major part of power dissipation in a portable device. Thus, to extend the operation time of a portable device, a high efficiency backlight module should be employed. White light-emitting diodes (WLEDs) have replaced cold cathode fluorescent lamps as backlight modules in portable electronics in recently years due to their superior power efficiency. This paper presents a high efficiency WLED driver with an integrated boost DC-DC converter that can drive a series of WLEDs using a single lithium-ion battery, which is the most popular power source for portable devices. As unexpected operation conditions can result in the failure of the driver, battery, or inductor, the driver integrates protection circuits for over current, over voltage, and under voltage. The driver was fabricated in the TSMC 0.25-μm 60-V bipolar-CMOS-DMOS process. The over current protection level is set to 2 A. The over voltage protection is set to 50 V, allowing the boost converter to drive 12 WLEDs in series connection. The under voltage protection circuit turns off the converter when it detects an input voltage below 2.5 V to protect the battery.
    01/2010;