출력전류 제어 기능이 향상된 고휘도 LED 구동 IC 설계

A conventional offline single-stage light-emitting diode (LED) driver with a high power factor usually produces a significant twice-line-frequency ripple LED current, where the ripple LED current is presented as flickering to human eye. This paper introduces a ripple cancellation method to remove the twice-line-frequency voltage ripple for an offline single-stage LED driver with a power factor correction. Consequently, a dc LED current can be produced to achieve flicker-free LED driving performance. At the same time, the required storage capacitor for the proposed LED driver can be greatly reduced, and the circuit implementation to achieve ripple cancellation is simple. Thus, the overall cost of the proposed LED driver is low. The proposed LED driver also features high efficiency because of its power structure. A 35-W Flyback experimental prototype and a 10-W Buck–Boost experimental prototype have been built to validate the proposed design and demonstrate its optimal performance.

This report presents the successful operation of a 1-bit counter circuit with an optical output as a demonstration of monolithic optoelectronic integrated circuits. The circuit was fabricated in a lattice-matched Si/III–V–N/Si heterostructure, using p-type metal oxide semiconductor field effect transistors and light emitting diodes (LEDs). The generation of structural defects was significantly suppressed and smooth surfaces were formed. The carrier concentration of the Si-capping layer was decreased to (0.8–1.2)×1017 cm-3 by increasing the growth temperature. In the resulting chips, the red light emission from the LEDs was in synchronization with the logical values of input and output voltages.

Light emitting diodes (LEDs) and Si-based metal oxide semiconductor field effect transistors (MOSFETs) were monolithically merged in a single chip which consisted of a Si layer and an InGaPN/GaPN double heterostructure layer lattice-matched to Si grown on a Si substrate by dislocation-free growth process for the first time. The developed fabrication process was conformed to a conventional planar MOSFET process. All LEDs and MOSFETs operated normally. Light emission from the LED was modulated by switching the MOSFET. The growth and fabrication technologies could be effective for realizing monolithic optoelectronic integrated circuits for massively parallel processing and optical interconnections.

The amount of light flicker in an AC–DC light-emitting diode (LED) driver is dependent on the size of filter capacitors. In this study, a study is conducted on reducing the size of filter capacitor in an AC–DC buck–boost/flyback LED driver using flicker index and per cent flicker light measures. Using this approach, a procedure for minimising the filter capacitance is presented. It is then concluded that relatively small filter capacitors such as film or ceramic capacitors can be chosen while meeting light flicker requirements. Hence, an LED drive with a longer lifetime can be achieved when compared with a driver using electrolytic capacitors. Experimental studies are presented for a 20 W AC–DC buck–boost/flyback LED driver prototype which utilises ceramic capacitors for driving Cree CR22-32L and XLamp XP-G LED strings.

The proposal of this paper is a modular three-phase ac-dc light-emitting diode (LED) driver for high-power luminaires based on LEDs that uses each phase to control an independent LED load removing in the process both the electrolytic capacitor and the second stage to increase both the lifetime and the efficiency. The driving of each LED load is done by means of a dc-dc converter operating as a loss-free resistor responsible for controlling the current across it. Furthermore, each dc-dc converter needs to achieve power factor correction (PFC) to comply with the restrictive IEC 61000-3-2 class C requirements, hence, achieving unity power factor and low total harmonic distortion. Taking advantage of the light properties, the output of the LED driver will be the sum of the light of each of the phases. Therefore, a theoretical study will be carried out to observe the feasibility of removing the electrolytic capacitor while guaranteeing a flicker-free behavior of the LED luminaire, even if the current of each string is pulsating at twice the mains frequency. This particular performance under high output current and voltage ripples requires reevaluating the well-known limits between the conduction modes in PFC converters. In addition, the theoretical analysis also discusses and proposes control methods for the LED driver, which thanks to its modularity can easily scale in power to drive high-power luminaires. In order to validate the theoretical analysis, a prototype has been built comprised three PFC boost converters disposing of their electrolytic capacitors. The designed prototype operates in the full range of the European three-phase line voltage, which varies between 380 and 420 V, and supplies an output light of 42.000 lm at a maximum power of 300 W while achieving an electrical efficiency of 97.5%.

This paper gives and explains the simulation results of single-event burnout (SEB) hardening in a power metal-oxide semiconductor field-effect transistor U-Shape Metal Oxide Semiconductor Field Effect Transistor (trench-gate MOSFET). It includes p+ plug enlargement and adds a buffer layer that is between the epitaxial layer and substrate. These two hardening solutions are compared and the optimized structure that can prevent SEB is given. The single event gate-rupture (SEGR) threshold voltages in different linear energy transfers are also compared with SEB results. In addition, the simulation results show that the change of gate bias can influence the occurrence of SEGR, and the natural radiation environment at cryogenic temperatures is also considered.

Single-crystalline GaN-based light-emitting diodes (LEDs) with high efficiency and long lifetime are the most promising solid-state lighting source compared with conventional incandescent and fluorescent lamps. However, the lattice and thermal mismatch between GaN and sapphire substrate always induces high stress and high density of dislocations and thus degrades the performance of LEDs. Here, the growth of high-quality GaN with low stress and a low density of dislocations on graphene (Gr) buffered sapphire substrate is reported for high-brightness blue LEDs. Gr films are directly grown on sapphire substrate to avoid the tedious transfer process and GaN is grown by metal-organic chemical vapor deposition (MOCVD). The introduced Gr buffer layer greatly releases biaxial stress and reduces the density of dislocations in GaN film and Inx Ga1-x N/GaN multiple quantum well structures. The as-fabricated LED devices therefore deliver much higher light output power compared to that on a bare sapphire substrate, which even outperforms the mature process derived counterpart. The GaN growth on Gr buffered sapphire only requires one-step growth, which largely shortens the MOCVD growth time. This facile strategy may pave a new way for applications of Gr films and bring several disruptive technologies for epitaxial growth of GaN film and its applications in high-brightness LEDs.

This paper presents a mean-peak current control (MPCC) buck dimmable light-emitting diode (LED) driver for automotive headlamp lighting applications. The proposed MPCC scheme can provide precise inductor current regulation during dimming operations by employing an integrator to enhance the accuracy of the LED average current. To address electromagnetic interference (EMI) issues in LED driver operation, adoption of a frequency jitter oscillator reduces the EMI amplitude of critical signals. Under typical operating conditions, the system clock signal exhibits random frequency jittering within $\pm 5 \%$ of the 175 kHz center frequency. The adoption of a soft-start circuit prevents potential chip damage caused by inrush current during startup by gradually ramping up the integrator reference voltage to eliminate surge current. Implemented in a $0.35-\mu \mathrm{m}$ HV CMOS process, the proposed LED driver achieves 1% LED current error and 96.7% peak efficiency over an input voltage range of 6 to 60 V while driving 1 to 20 LEDs.

In this study we propose the fabrication of advanced high-speed complementary metal oxide semiconductor field effect transistor (AHCMOS) by combining a P-carbon nanotube with n-metal oxide semiconductor (NMOS) on a single chip. The target is to achieve extremely high speed low-power dissipating miniaturized device with improved functionalities.  The technology of conventional metal oxide semiconductor field effect transistor (MOSFET) and nanotechnology are applied in this research. A P-carbon nanotube is complemented with the conventional NMOS all embedded on the same chip.  Although it is possible to fabricate both a P and N carbon nanotube to form a complementary pair, and also a PMOS and NMOS to form a complementary pair, however in this research we propose a hybrid structure with carbon nanotube transistor technology and complementary MOSFET technology. This device therefore combines the best characteristics of carbon nanotube technology and CMOS technology to provide enhanced logic functions that are optimized for the high-speed, low-power systems and miniaturized size ideal for very large scale integration (VLSI).

This paper proposes a single-stage high-efficacy fly back power-factor-correction (PFC) converter with optimization efficiency control for driving multi-string light-emitting diodes (LEDs). The LED driver consists of a fly back converter with PFC mechanism and a constant-current drive circuit with functionalities of efficiency optimization and dimming control. The proposed single-stage LED driver topology features benefits of high power factor and low total harmonic distortion (THD) in low-cost outlay. The pulse width modulation (PWM) dimming mechanism cooperating with the constant-current control circuit completes the LED dimming control. In order to reduce the power dissipations of the dimming circuits, a dynamic voltage regulation (DVR) control is presented to regulate the LED supply voltage by means of the sensing of the drain voltage of the MOSFET in the current controller. While maintaining the desired LED brightness, the DVR technique can minimize the voltage drop of the dimming circuit to enhance the LED driver efficiency further. A 30W white LED driver is devised and a corresponding driver prototype is realized. Testing results are shown experimentally to verify the effectiveness and performance improved of the proposed scheme.

This paper introduces a gate-driven mixed mode excitation that is applicable to dimmable electronic ballasts. The proposed approach combines the characteristics of self-oscillating mode and external excitation. In the mixed mode excitation, the metal oxide semiconductor field effect transistors in an electronic ballast are turned on by the resonant current and turned off by the gate driver, which is triggered by a low voltage control integrated circuit (IC). By adjusting this triggering point, the low voltage control IC controls the switching frequency of the electronic ballast. In the electronic ballast with mixed mode excitation, filament preheating, dimming, and protection are all implemented by the low voltage control IC, which is fabricated in a 3.3-V standard CMOS process. The proposed approach allows for the realization of a low cost and high performance electronic ballast

In this paper, a cost-effective single switch multi-channel LED (light emitting diode) driver is proposed. While conventional LED drivers require as many non-isolated DC/DC converters as the number of LED channels, the proposed LED driver needs only one power switch and several balancing capacitors instead of expensive non-isolated DC/DC converters. Therefore, the proposed driver features a simpler structure, with a lower cost and a higher efficiency. Because its power switch can be turned off under the zero current switching condition, it has very desirable advantages such as improved electromagnetic interference characteristics and high efficiency. Moreover, it uses only a small number of DC blocking capacitors with no additional active devices for the current balancing of multi-channel LEDs. As a result, the proposed driver exhibits high reliability and is cost effective. To confirm the validity of the proposed driver, a theoretical analysis is performed, and design considerations and experimental results obtained from a prototype that is applicable to a 46" LED-TV are presented.

In this paper, a light-emitting diode (LED) driver with a high power factor (PF) and low-frequency current ripple suppression over a wide input range is presented, and a flyback converter is designed to operate in the discontinuous conduction mode (DCM), with a digital controller used to keep the duty cycle constant for half of the utility cycle under a fixed load and input voltage. This method ensures that the input current is in phase with the universal input voltage, thus achieving a high power factor without utilizing feedforward control. Furthermore, on the secondary side, the time of the zero point of the utility voltage can be attained so that the duty cycle can be updated at this time. In addition, a simple auxiliary circuit is connected parallel to the output side to absorb the excess output current of the flyback converter or to release the current to the load to make up for the shortage of the output current of the flyback converter so that the low-frequency ripple of the output current can be inhibited. There are only two current-detecting resistors used in this study: one is the output current-sensing resistor of the flyback converter, and the other is the output current-sensing resistor of the auxiliary circuit.

With the development of new technologies, LEDs (light-emitting diodes) take a significant position in lighting due to their long-life spans and high luminous efficacy, which result in energy and maintenance cost savings. These efficient and innovative light sources require adequate ballast or electronic control gear, also known as LED drivers, for their operation. An LED driver provides appropriate voltage level and current for the operation of LEDs. It converts and rectifies higher voltages of alternating current to lower voltages of direct current and regulates the current flowing through LEDs at a nominal level. There are many advantages and disadvantages to using LEDs, primarily caused by LED circuits and LED drivers. The dimming influence of outdoor LED lighting on the LED driver performance is analysed in this paper, specifically the testing of an LED lighting driver by changing the load level. Results of LED driver efficiency calculated from measured input and output power, output voltage ripple measurements, and total harmonic distortion analysis are shown. Based on the measurement results, significant recommendations and concluding remarks are given.

The Moore’s law of scaling of metal oxide semiconductor field effect transistor (MOSFET) had been a driving force toward the unprecedented advancement in development of integrated circuit over the last five decades. As the technology scales down to 7 nm node and below following the Moore’s law, conventional MOSFETs are becoming more vulnerable to extremely high off-state leakage current exhibiting a tremendous amount of standby power dissipation. Moreover, the fundamental physical limit of MOSFET of 60 mV/decade subthreshold slope exacerbates the situation further requiring current transport mechanism other than drift and diffusion for the operation of transistors. One way to limit such unrestrained amount of power dissipation is to explore novel materials with superior thermal and electrical properties compared to traditional bulk materials. On the other hand, energy efficient steep subthreshold slope devices are the other possible alternatives to conventional MOSFET based on emerging novel materials. This dissertation addresses the potential of both advanced materials and devices for development of next generation energy efficient integrated circuits. Among the different steep subthreshold slope devices, tunnel field effect transistor (TFET) has been considered as a promising candidate after MOSFET. A superior gate control on source-channel band-to-band tunneling providing subthreshold slopes well below than 60 mV/decade. With the emergence of atomically thin two-dimensional (2D) materials, interest in the design of TFET based on such novel 2D materials has also grown significantly. Graphene being the first and the most studied among 2D materials with exotic electronic and thermal properties. This dissertation primarily considers current transport modeling of graphene based tunnel devices from transport phenomena to energy efficient integrated circuit design. Three current transport models: semi-classical, semi-quantum and numerical simulations are described for the modeling of graphene nanoribbon tunnel field effect transistor (GNR TFET) where the semi-classical model is in close agreement with the quantum transport simulation. Moreover, the models produced are also extended for integrated circuit design using Verilog-A hardware description language for logic design. In order to overcome the challenges associated with the band gap engineering for making graphene transistor for logic operation, the promise of graphene based interlayer tunneling transistors are discussed along with their existing fundamental physical limitation of subthreshold slope. It has been found that such interlayer tunnel transistor has very poor electrostatic gate control on drain current. It gives subthreshold slope greater than the thermionic limit of 60 mV/decade at room temperature. In order to resolve such limitation of