• Journal of Power Electronics
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• v.16 no.3
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• pp.925-935
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• 2016

This paper proposes a new interleaved double-input three-level Boost (DITLB) converter, which is composed of two boost converters indirectly in series. Thus, a high voltage gain, together with a low component stress and a small input current ripple due to the interleaved control scheme, is achieved. The operating principle of the DITLB converter under the individual supplying power (ISP) and simultaneous supplying power (SSP) mode is analyzed. In addition, closed-loop control strategies composed of a voltage-current loop and a voltage-balance loop, have been researched to make the converter operate steadily and to alleviate the neutral-point imbalance issue. Experimental results verify correctness and feasibility of the proposed topology and control strategies.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.6
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• pp.442-450
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• 2020

A small-signal modeling approach for a three-level boost (TLB) converter and a design methodology for a double-loop controller are proposed in this study. Conventional modeling of TLB converters involves three state variables. Moreover, TLB converters have two operation modes depending on the duty ratio. Consequently, complex mathematical calculations are required for controller design. This study proposes a simple system modeling method that uses two state variables, unlike previous methods that require three state variables. Analysis shows that the transfer functions of the two operation modes can be expressed as identical equations. This condition means that the linear feedback controller can be applied to all operational ranges, that is, for full duty ratios. The design method for a double-loop controller using a PI controller is presented in step-by-step sequences. Simulation and experimental verifications are conducted to verify the effectiveness of the small-signal analysis and control system design.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.6
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• pp.29-36
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• 2015

This paper presents an LED backlight driver IC consisting of three linear current regulators and an output-voltage regulation loop with a self-adjustable reference voltage. In the proposed LED driver, the output voltage is controlled by dual feedback loops. The first loop senses and controls the output voltage, and the second loop senses the voltage drop of the linear current regulator and adjusts the reference voltage. With these feedback loops, the voltage drop of the linear current regulator is maintained at a minimum value, at which the driver efficiency is maximized. The output of the driver is a three-channel LED setup with four LEDs in each channel. The luminance is adjusted by the PWM dimming signal. The proposed driver is designed by a $0.35-{\mu}m$ 60-V high-voltage process, resulting in an experimental maximum efficiency of approximately 85%.

• Journal of Information Display
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• v.13 no.2
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• pp.73-82
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• 2012

In this paper, a light-emitting diode (LED) backlight driver integrated circuit (IC) for medium-sized liquid crystal displays (LCDs) is proposed. In the proposed IC, a linear current regulator with matched internal resistors and an adaptive phase-shifted pulse-width modulation (PWM) dimming controller are also proposed to improve LED current uniformity and reliability. The double feedback loop control boost converter is used to achieve high power efficiency, fast transient characteristic, and high dimming frequency and resolution. The proposed IC was fabricated using the 0.35 ${\mu}m$ bipolar-CMOS-DMOS (BCD) process. The LED current uniformity and LED fault immunity of the proposed IC were verified through experiments. The measured power efficiency was 90%; the measured LED current uniformity, 97%; and the measured rising and falling times of the LED current, 86 and 7 ns, respectively. Due to the fast rising and falling characteristics, the proposed IC operates up to 39 kHz PWM dimming frequency, with an 8-bit dimming resolution. It was verified that the phase difference between the PWM dimming signals is changed adaptively when LED fault occurs. The experiment results showed that the proposed IC meets the requirements for the LED backlight driver IC for medium-sized LCDs.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.556-560
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• 2001

In this paper, a soft-switching discontinuous mode (DCM) power factor corrected (PFC) converter is analyzed by applying the double Fourier series expansion. It is found that the fundamental component and higher-order harmonics included in the input current waveform are obtained by the Fourier series expansion of the mean value of the inductor current. From the theoretical analysis, a new method removing the distortion of the input current waveform is proposed. In spite of an open loop system, the proposed method makes a great improvement of the total harmonic distortion even if the ratio of output voltage to input voltage is very low.

• Journal of Information Display
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• v.11 no.4
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• pp.173-181
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• 2010

In this paper, light-emitting-diode (LED) backlight driving circuits and dimming method for medium-sized and large liquid crystal displays (LCDs) are proposed. The double loop control method, the intelligent-phase-shifted PWM dimming method, the fast-switching current regulator, and the current matching techniques are proposed to improve not only the current regulation characteristics and the power efficiency but also the current matching characteristics and the transient response of the LED current. The brightness of the backlight using the proposed local dimming method was determined from the histogram of the local block to reduce the power consumption of the backlight without image distortion. The measured maximum power efficiency of the LED backlight driving circuit for medium-sized LCDs was 90%, and the simulation results showed an 88% maximum power efficiency of the LED backlight driving circuit for large LCDs. The maximum backlight power-saving ratio of the proposed dimming method was 41.7% in the simulation with a high-contrast image. The experiment and simulation results showed that the performance of LEDs as LCD backlight units (BLUs) improved with the proposed circuits and method.