• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2145-2147
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• 1998

This paper presents a Class-D type switched mode audio power amplifier employing ZVT(Zero-Voltage-Transition) soft switching technique. In order to obtain a wide bandwidth and lower distortion for an audio amplifier a high switching frequency is essential. The ZVT switching scheme enables a high frequency switching without sacrificing the efficiency much as in a hard switching. A prototype amplifier is built to demonstrate the feasibility of this technique for the audio power amplifier.

• 전기의세계
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• 제29권12호
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• pp.798-803
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• 1980

A computer program for noise analysis of the audio circuit is developed. The application of the program to the equalizer, low frequency amplifier of radio circuit and cascaded amplifier show good results. The general noise analysis method for cascade operational amplifier is presented. The noise spectral power density is calculated for a resonator active filter.

• JSTS:Journal of Semiconductor Technology and Science
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• 제14권1호
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• pp.109-116
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• 2014

This paper presents a high-efficiency digital class-D audio amplifier using a composite interpolation filter for portable audio devices. The proposed audio amplifier is composed of an interpolation filter, a delta-sigma modulator, and a class-D output stage. To reduce power consumption, the designed interpolation filter has an optimized composite structure that uses a direct-form symmetric and Lagrange FIR filters. Compared to the filters with homogeneous structures, the hardware cost and complexity are reduced by about half by the optimization. The coefficients of the digital delta-sigma modulator are also optimized for low power consumption. The class-D output stage has gate driver circuits to reduce shoot-through current. The implemented class-D audio amplifier exhibited a high efficiency of 87.8 % with an output power of 57 mW at a load impedance of $16{\Omega}$ and a power supply voltage of 1.8 V. An outstanding signal-to-noise ratio of 90 dB and a total harmonic distortion plus noise of 0.03 % are achieved for a single-tone input signal with a frequency of 1 kHz.

• 한국멀티미디어학회논문지
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• 제20권9호
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• pp.1551-1558
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• 2017

Audio power amplifiers have been designed based on the premise that the impedance of loudspeakers is fixed at nominal 4 ohms or 8 ohms. However, it is known that the impedance varies with frequency and takes on the nominal value at some limited frequencies. The principle of the loudspeaker operation reveals that the sound pressure produced by the loudspeaker is proportional to the current flowing in the voice coil, not the voltage between the two terminals. We take the characteristics of the loudspeaker into account and compare the frequency responses of the loudspeaker in voltage-drive mode and current-drive mode via computer simulations, to conclude that the audio amplifier drive mode should be re-considered in an effort to improve the sound quality.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.976-979
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• 2002

A new controller for switching audio power amplifier with digital PWM input is proposed- Bi-directional Saw-tooth Error Correction (BSEC). This control method for high quality switching amplifier is based on a pulsed edge correction approach using PWM audio signal input as a reference of power switching digital to analog converter. The proposed controller has excellent features such as wide error correction range and no limitation on the modulation index. The controller is implemented in the half-bridge class D amplifier and the performance is verified through hardware experiments. It delivers 100W into 4${\Omega}$ load with less than 0.2% of total harmonic distortion (THD) all over operating range and an maximum efficiency of 82%.

• 대한전자공학회논문지SD
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• 제45권7호
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• pp.44-51
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• 2008

본 논문에서는 비대칭 펄스 폭 변조 파워-앰프를 갖는 스테레오 오디오 디지털-아날로그 변환기를 제안한다. 고 전력 오디오 기기에 주로 사용되던 class-D 증폭기를 헤드폰 응용에 적용하기 위하여, 증폭기가 디지털-아날로그 변환기와 한 칩으로 집적화될 때에 발생되는 채널 간 간섭에 의한 잡음을 분석하고 이 영향을 줄이기 위한 시그마-델타 변조기의 최적화 방안을 제시하였다. 또한, 비대칭 구조의 펄스 폭 변조 방식이 파워-앰프 단에서 발생되는 스위칭 노이즈와 전력 손실을 줄이기 위하여 구현되었다. 제안된 구조들은 0.13-mm CMOS 공정을 통해 설계 제작되었다. 제안된 오디오 디지털-아날로그 변환기는 단일 출력을 가진 파워-앰프를 포함하여 4.4-mW를 소모하면서 다이나믹-레인지 95-dB를 확보하였다.

• 한국멀티미디어학회논문지
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• 제21권9호
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• pp.1068-1075
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• 2018

We propose a method for driving loudspeakers from class D audio power amplifiers in current mode, instead of in conventional voltage mode, which was impossible with the feedback circuitry. Unlike analog audio amplifiers, Class D audio power amplifiers have signal delay between the input and output signals, which makes it difficult to apply the feedback circuitry for current-mode driving. The idea of the pre-distortion scheme used for the compensation of the non-linearity of RF power amplifiers is adapted to remedy the impedance variation effect of the loudspeakers for current driving. The method uses the speaker model for the pre-distorter to compensate for the speaker impedance variation with frequency. The simulation and test results confirms the validity of the proposed method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.905-908
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• 2005

본 논문에서는 class AB opamp 를 채용한 384kHz differential PWM 신호를 입력으로 하는 2-channel stereo audio amplifier 블록을 공급전압 3.3V 조건에서 SMIC 0.18um thick oxide 기술을 이용하여 설계한다. 여기서 class AB opamp 는 공정 변화에 따른 quiescent current가 변하는 것을 최소화하기 위하여 adaptive load 를 사용하며, 전체적으로는 3 차 Butterworth lowpass filter 와 differential-to-single converter 로 구성된 2 개의 audio amplifier 와 출력전압이 ${\frac{1}{2}}Vdd$ 인 common output 블록으로 구성된다. 이러한 설계를 통하여 32ohm 의 저항 load 를 구동할 수 있는 -60dB THD, 전체 quiescent current 2mA 대인 CMOS class AB stereo audio amplifier 를 구현하였다.

• 전기학회논문지
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• 제67권3호
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• pp.383-390
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• 2018

Piezoelectric micro-machined ultrasonic transducers for highly directional speaker need DC bias voltage. Most existing power amplifiers are not suitable for use in highly directional transducers because they are based on AC. In addition, since the piezoelectric micro-machined ultrasonic transducer has a large capacitive reactance, the power efficiency of the power amplifier is very low. Thus this paper proposes a new high efficiency power amplifier with DC bias voltage. In addition, by designing a matching circuit to compensate the capacitive reactance of the micro-machined ultrasonic transducer, the power efficiency of the power amplifier increases. The operating characteristics of the proposed power amplifier was verified by an experimental prototype. The proposed power amplifier is expected to be widely used in designing and implementing other related power amplifiers.

• 전자공학회논문지CI
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• 제48권6호
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• pp.56-61
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• 2011

본 논문은 코일형 스피커에 사용되는 D 클래스 오디오 앰프를 세라믹 평판스피커에 적용하는 기술을 제안하였다. 제안 방법은 전압 구동 방식의 G class와는 달리 전력 구동 방식의 D class 방식을 사용하였고 매칭 트랜스미터를 사용하여 결과적으로 보다 더 큰 전압 구동을 할 수 있었다. 목재, 플라스틱, 종이 등의 다양한 매질을 활용하여 음량에 대한 성능을 평가한 결과, 기존의 G class 오디오 앰프 방식에 비해 제안 방법이 약 10% 이상의 성능 향상을 보여주었다. 본 시스템은 휴대용 정보기기들의 외장 스피커 시스템으로 활용할 수 있다.