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Hwang J.T.,Samsung | Jung M.S.,Silicon Mitus | Kim D.H.,Samsung | Lee J.H.,Neofidelity Inc. | And 2 more authors.
IEEE Journal of Solid-State Circuits | Year: 2012

The off-the-line primary side regulation flyback LED lamp driver is proposed based on LED forward voltage tracking (VFT) and duty variation tracking (DVT) methods, which satisfy good line/load regulation, high power factor and TRIAC dimming possibility. This paper introduces that four derivative types (TYPE-I to IV) are possible to implement using supply voltage, MOSFET drain voltage and duty cycle signal with the four types of sensing circuits on the basis of VFT and DVT concepts. The load regulations of TYPE-I to IV show 0.89%, 0.51%, 0.43% and 0.56% [A/V], respectively. TYPEI to IV show ±8%, ±2%, ±2% and ±4% of line regulation over 180 to 260 V AC variation, respectively. Each type satisfies above 81% of efficiency when it delivers 6 to 12 W to the LED load at 220 VAC. The power factors of all types are above 0.9. The chip is implemented using 0.35 μm BCD process and occupies 0.76 mm2. © 1966-2012 IEEE.


Choi J.,Institute of Microelectronics, Singapore | Han H.-S.,Silicon Mitus | Lee K.,Korea Advanced Institute of Science and Technology
IEEE Transactions on Power Electronics | Year: 2015

A light-emitting diode (LED) driver compatible with fluorescent lamp (FL) ballasts is presented for a lamp-only replacement without rewiring the existing lamp fixture. Ballasts have a common function to regulate the lamp current, despite widely different circuit topologies. In this paper, magnetic and electronic ballasts are modeled as nonideal current sources and a current-sourced boost converter, which is derived from the duality, is adopted for the power conversion from ballasts. A rectifier circuit with capacitor filaments is proposed to interface the converter with the four-wire output of the ballast. A digital controller emulates the high-voltage discharge of the FL and operates adaptively with various ballasts. A prototype 20- W LED driver for retrofitting T8 36-W FL is evaluated with both magnetic and electronic ballasts. In addition to wide compatibility, accurate regulation of the LED current within 0.6% error and high driver efficiency over 89.7% are obtained. © 1986-2012 IEEE.


Hong S.W.,Silicon Mitus | Kim H.J.,Konkuk University | Park J.-S.,Konkuk University | Pu Y.G.,Konkuk University | And 3 more authors.
IEEE Transactions on Power Electronics | Year: 2011

This paper presents a low-profile low-cost (LLC) resonant controller IC for LED backlight units fully operating at the secondary side. The integrated dimming circuitry is proposed to improve the dynamic current control characteristics and the LED current density for the brightness modulation of a large screen liquid crystal display. A dual-slope clock generator, including a soft start, is proposed in order to overcome the frequency error due to the undershoot found in conventional approaches. In addition, a new dead-time generator is proposed in order to implement an accurate dead time independent of the output frequency of the clock generator. Protection circuits, such as a under voltage lock out, thermal shut down, open LED detector, and shorted LED detector, have been implemented in order to improve the reliability of the controller IC. The chip is fabricated using 0.35 μm bipolar CMOS DMOS decimal technology; the die size is 2mm × 2mm. The frequency of the clock generator ranges from 50 to 500kHz; the dead time ranges from 50 ns to 2.2 μs. The efficiency of the LED driving circuit is 91%. The current consumption of the LLC resonant controller IC is 40mA for a 100kHz operation frequency using a 15V supply voltage. © 2011 IEEE.


Hong S.-I.,Hanyang University | Han J.-W.,Hanyang University | Kim D.-H.,Silicon Mitus | Kwon O.-K.,Hanyang University
Digest of Technical Papers - IEEE International Solid-State Circuits Conference | Year: 2010

Light-emitting diodes (LEDs) are used as an alternative to the cold cathode fluorescent lamp (CCFL) for LCD backlight units (BLU) for their lower power consumption, wider color gamut, and better dimming capability, in addition to being mercury-free [1, 2]. Recently, various studies have focused on low-power solutions using LED BLUs in a multi-channel LED configuration [1-3]. While these methods effectively reduce power consumption of LED drivers with the phase-shifted backlight driving method [1], the transient response of the LED forward current is limited by the transient response of the boost converter in the LED driver IC. This makes it difficult to obtain a higher PWM dimming frequency than 1kHz in the LED BLU. In addition, the slow transition time of the LED current limits the minimum duty cycle and PWM dimming resolution. These problems generate audible noise and negatively affect the contrast ratio and power consumption of LCDs. To overcome these problems, we use an adaptive boost voltage with a double-loop control method. Here, the transient response of the LED current depends only on the transient response of the current regulator, which is significantly faster than that of the boost converter. ©2010 IEEE.


Kim D.-H.,Soongsil University | Jang J.-H.,Soongsil University | Park J.-H.,Soongsil University | Kim J.-W.,Silicon Mitus
Journal of Power Electronics | Year: 2013

The depletion of natural resources and renewable energy sources, such as photovoltaic (PV) energy, has been highlighted for global energy solution. The PV power control unit in the PV power-generation technology requires a high step-up DC-DC converter. The conventional step-up DC-DC converter has low efficiency and limited step-up ratio. To overcome these problems, a novel high step-up DC-DC converter using an isolated switched capacitor cell is proposed. The step-up converter uses the proposed transformer and employs the switched-capacitor cell to enable integration with the boost inductor. The output of the boost converter and isolated switched-capacitor cell are connected in series to obtain high step-up with low turn-on ratio. A hardware prototype with 30 V to 40 V input voltage and 340 V output voltage is implemented to verify the performance of the proposed converter. As an extended version, another novel high step-up isolated switched-capacitor single-ended DC-DC converter integrated with a tapped-inductor (TI) boost converter is proposed. The TI boost converter and isolated-switched-capacitor outputs are connected in series to achieve high step-up. All magnetic components are integrated in a single magnetic core to lower costs. A prototype hardware with 20 V to 40 V input voltage, 340 V output voltage, and 100 W output power is implemented to verify the performance of the proposed converter.


Huh Y.,Silicon Mitus
2011 Proceedings of Technical Papers: IEEE Asian Solid-State Circuits Conference 2011, A-SSCC 2011 | Year: 2011

Mobile devices such as smartphones have two major restrictions from the standpoint of design: thermal dissipation and the supply of battery power. Thermal dissipation restricts power consumption of AP (Application Processor), which additionally limits computational performance. Battery usage time is also determined by power consumption of the mobile device. Due to these reasons, power management to improve efficiency of electric power usage becomes a very crucial part of mobile product design. In this paper, we look into power management from two different hierarchical aspects: power management techniques at the processor design level and PMIC (Power Management IC) at the power analog circuit level. Particularly, PMIC in the smartphone is expanding its role to a multi-function solution chip from the traditional function of power conversion and distribution. Future direction of PMIC and engineering challenges will be also discussed. © 2011 IEEE.


Patent
Silicon Mitus | Date: 2014-12-17

Provided is a method of controlling a battery that supplies power to a system, the method including: providing a discharge path, outside of the system; monitoring an ON/OFF state of the system, a terminal voltage of the battery, and an ambient temperature; and discharging the battery through the discharge path when the system is turned off, the terminal voltage of the battery exceeds a first reference voltage, and the ambient temperature exceeds a reference temperature.


A control device and an LED light emitting device using the same are provided and technology of providing a high contrast ratio to the LED light emitting device and allowing the LED light emitting device to perform a stable operation is disclosed. The LED light emitting device includes a DC/DC converter reference voltage generator that generates a DC/DC converter reference voltage so that a minimum level of a channel voltage having a largest LED voltage drop agrees with a predetermined minimum reference voltage by detecting a plurality of channel voltages corresponding to LED voltage drops of each of a plurality of LED channels LED and an output voltage controller that controls an output voltage of the DC/DC converter using a distribution voltage corresponding to an output voltage and the DC/DC converter reference voltage.


Patent
Silicon Mitus | Date: 2010-06-29

An LED light emitting device and a method of driving the same are provided, and technology that can uniformly sustain the magnitude of a channel current flowing to a plurality of LED channels is disclosed. The LED light emitting device includes: a plurality of LED channels that are formed with a plurality of LED elements that are continuously connected in series; and a constant current source that controls each channel current flowing to the plurality of LED channels according to a predetermined channel reference current to be a predetermined setting channel current, wherein the constant current source includes a plurality of operating amplifiers that control the magnitude of each of the channel currents, and a feedback voltage generating according to a predetermined offset reference current is input to a second input terminal of an operating amplifier for an offset setting period that sets an offset voltage of the plurality of operating amplifiers, a reference voltage generating according to a channel reference current is input to a first input terminal of the operating amplifier, and an offset voltage of each of the plurality of operating amplifiers is set so that an actual channel current may be identical to a predetermined setting channel current.


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