Young-Hun Ko

Non-load-balance-dependent high efficiency single-inductor multiple-output (SIMO) DC-DC converters

A single-inductor multiple-output (SIMO) DC-DC converter providing buck and boost outputs with a new control topology is presented. In the proposed switching sequence, which does not require any special blocks, energy delivery is always accomplished by flowing energy through an inductor, which leads to high conversion efficiency regardless of the balance between the buck and boost output loads. Implemented in 0.35-μm CMOS, the proposed SIMO DC-DC converter achieves high conversion efficiency regardless of the load balance between the outputs. The measured maximum efficiency reaches 82 % under heavy loads.

Load-Balance-Independent High Efficiency Single-Inductor Multiple-Output (SIMO) DC-DC Converters

A single-inductor multiple-output (SIMO) DC-DC converter providing buck and boost outputs with a new switching sequence is presented. In the proposed switching sequence, which does not require any additional blocks, input energy is delivered to outputs continuously by flowing current through the inductor, which leads to high conversion efficiency regardless of the balance between the buck and boost output loads. Furthermore, instead of multiple output loop compensation, only the freewheeling current feedback loop is compensated, which minimizes the number of off-chip components and nullifies the need for the equivalent series resistance (ESR) of the output capacitor for loop compensation. Therefore, power conversion efficiency and output voltage ripples can be improved and minimized, respectively. Implemented in a 0.35- μm CMOS, the proposed SIMO DC-DC converter achieves high conversion efficiency regardless of the load balance between the two outputs with maximum efficiency reaching up to 82% under heavy loads.

A 200-V 98.16%-Efficiency Buck LED Driver Using Integrated Current Control to Improve Current Accuracy for Large-Scale Single-String LED Backlighting Applications

This paper presents an average current mode buck dimmable light-emitting diode (LED) driver for large-scale single-string LED backlighting applications. The proposed integrated current control technique can provide exact current control signals by using an autozeroed integrator to enhance the accuracy of the average current of LEDs while driving a large number of LEDs. Adoption of discontinuous low-side current sensing leads to power loss reduction. Adoption of a fast-settling technique allows the LED driver to enter into the steady state within three switching cycles after the dimming signal is triggered. Implemented in a 0.35-μm HV CMOS process, the proposed LED driver achieves 1.7% LED current error and 98.16% peak efficiency over an input voltage range of 110 to 200 V while driving 30 to 50 LEDs.

A 45-dB, 150-Hz, and 18-mW Touch Controller for On-Cell Capacitive TSP Systems

A touch controller is proposed for on-cell capacitive touch screen panel systems, which adopts a newly proposed peaking noise detector and low-frequency rejection filters. Implemented in a 0.35-μmCMOS, the proposed touch controller with 3.3-V drive signal shows the maximum signal-to-noise ratio and scan rate of 45 dB and 150 Hz, respectively, while consuming 18 mW from a 3.3-V supply.

Calibration technique for sensitivity variation in RVDT type accelerator position sensor

This paper presents a calibration technique for RVDT sensitivity variation, which occurs as a result of using high excitation frequency and changing the distance between the coil printed on PCB and the magnetic core. An additional secondary coil and new signal processing are employed to calibrate the sensitivity variation. The output voltage amplitude of this additional coil is not affected from rotation of the magnetic core, and is changed by distance between the coil and the magnetic core. The proposed signal processing can calibrate the sensitivity variation without being influenced by environmental factors such as humidity and temperature. The proposed method calibrates sensitivity variation by 76% compared to the conventional method when the distance between the coil and the magnetic core changes by ±0.2 mm around 1.0 mm.

Low Phase Noise LC-VCO with Active Source Degeneration

A new CMOS voltage-bias differential LC voltage-controlled oscillator (LC-VCO) with active source degeneration is proposed. The proposed degeneration technique preserves the quality factor of the LC-tank which leads to improvement in phase noise of VCO oscillators. The proposed VCO shows the high figure of merit (FOM) with large tuning range, low power, and small chip size compared to those of conventional voltage-bias differential LCVCO. The proposed VCO implemented in 0.18-㎛ CMOS shows the phase noise of -118 ㏈c/㎐ at 1 ㎒ offset oscillating at 5.03 ㎓, tuning range of 12%, occupies 0.15 ㎟ of chip area while dissipating 1.44 ㎽ from 0.8 V supply.

A Fast Low Dropout Regulator with High Slew Rate and Large Unity-Gain Bandwidth

A low dropout regulator (LDO) with fast transient responses is presented. The proposed LDO eliminates the trade-off between slew rate and unity gain bandwidth, which are the key parameters for fast transient responses. In the proposed buffer, by changing the slew current path, the slew rate and unity gain bandwidth can be controlled independently. Implemented in 0.18- ㎛ high voltage CMOS, the proposed LDO shows up to 200 ㎃ load current with 0.2V dropout voltage for 1㎌ output capacitance. The measured maximum transient output voltage variation, minimum quiescent current at no load condition, and maximum unity gain frequency are 24 ㎷, 7.5㎂, and higher than 1 ㎒, respectively.

A Compact Flicker-Free Transformer-Less LED Driver With an Enhanced Power Factor for Omnidirectional Multichannel Smart Bulb Applications

In this paper, a flicker-free transformer-less multichannel light-emitting diode (LED) driver that adopts a new power factor enhancement technique is presented. The proposed LED driver divides the transmission path of the current to the LED string in two ways depending on the instantaneous input voltage in order to improve the PF relative to that of a conventional compact flicker-free LED driver that uses a fixed LED current regulation scheme with only one electrolytic capacitor. The proposed driver can be implemented with a minimum number of external components leading to a compact module that allows a light bulb with omnidirectional light emission. In order to enhance the expandability of the smart bulb, a conventional buck converter with 3-V output is integrated with the proposed LED driver to supply the peripherals of the module. The proposed LED driver IC is implemented in a 0.35-μm ultrahigh voltage CMOS process and occupies an area of 2.9 mm × 2.0 mm. A 10-W smart bulb prototype that adopts the proposed LED driver is flicker free and shows a power factor of 0.715 and power conversion efficiency of 77.5% for an ac supply of 120 V.