• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.149-156
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• 2012

A digital input class-D audio amplifier is presented for digital hearing aid. The class-D audio amplifier is composed of digital and analog circuits. The analog circuit converts a digital input to a analog audio signal (DAC) with noise suppression in the audio band. An interpolated digital delta-sigma modulator is used to convert data types between digital signal processor (DSP) and digital-to-analog converter (DAC). An 16-bit, 25-kbps pulse code modulated (PCM) input is interpolated to 16-bit, 50-kbps by a digital filter. The output signal of interpolation filter is noise-shaped by a third-order digital sigma-delta modulator (SDM). As a result, 1.5-bit, 3.2-Mbps signal is applied to simple digital to analog converter.

• Journal of Korea Multimedia Society
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• v.21 no.9
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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.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.601-605
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• 2004

A new high efficiency and low profile on-board DC/DC converter for digital car audio amplifier is proposed. The proposed converter shows the continuous input current, no DC excitation current of the transformer, the minimized electro-magnetic interference (EMI), no output inductor, and the low voltage stress of the secondary rectifier diodes. The 60W industrial sample of the proposed converter is implemented for digital car audio amplifier and the measured efficiency is $88.3\%$ at nominal input voltage.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2704-2707
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• 1999

This paper presents a simple high power audio class amplifier which is controlled by a new current control switching method. Although this class D amplifier has an only one current control loop with the proposed switching method, a good performance can be obtained. And a novel switching strategy for driving stereo signal amplifier circuit with three phase full bridge is discussed also. With the simulation and experimental results, usefulness of the proposed amplifier is confirmed.

• The Journal of the Acoustical Society of Korea
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• v.26 no.5
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• pp.188-193
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• 2007

In general, analog amplifiers for 5.1 or more channels have been used to configure home theater systems. In order to make high-performance systems, it is desirable to process audio signals in digital techniques in consideration of output and efficiency of speakers. Especially we need 7.1-channel system to separate audio signals efficiently. In this paper we implemented the architecture of S/PDIF 7.1-channel digital amplifier for home theater systems. The amplifier shows good performance with less loss of original sounds because of both strong characteristics against noises and direct processing of input data.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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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.

• Journal of the Korea Convergence Society
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• v.7 no.3
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• pp.77-85
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• 2016

We propose a digital signal processing technic that can compensate the non-linearity inherent in audio amplifiers, and present the result of the simulation. The inherent non-linearity of the audio power amplifier arising from analog devices is compensated via a digital signal processing technic consisting of indirect learning architecture and an adaptive filter. The simulation results show that the compensator can be realized using a third-order polynomial and compensates odd-order non-linearity efficiently. The even-oder non-linearity is mainly due to the dc offset at the output, which is difficult to eliminate with the proposed method. Care must be taken in designing the bias circuit to avoid the DC offset at the output. The proposed technic has significance in that digital signal processing technic can compensate for the impairment that is an inherent characteristic of an analog system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.6
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• pp.251-257
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• 2014

An actuator system is a type of motor designed to control a mechanism operated by a source of energy, in the form of an electric current by converting energy into some kind of motion. As audio actuators, transforming electric voltage signal into audio signal, speakers and amplifiers are commonly used. In applications of industry, high output power systems are required. For these systems to generate high-quality output, it is essential to control output impedance of audio systems. We have developed an adaptable power supply for driving active amplifier systems with variable loads. Depending on the changing values of resistance of the speaker which produces audible sound by transforming electric voltage signal, the power supply source of the active amplifier can generate the maximum power delivered to the speaker by an adaptable change of loads. The amplifier is well protected from the abrupt increment of peak current and an excess of current flow.

• Journal of Power Electronics
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• v.6 no.1
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• pp.83-93
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• 2006

A new high efficiency and low profile on-board DC/DC converter for digital car audio amplifiers is proposed. The proposed converter shows low conduction loss due to the low voltage stress of the secondary diodes, a lack of DC magnetizing current for the transformer, and a lack of stored energy in the transformer. Moreover, since the primary MOSFETs are turned-on under zero-voltage-switching (ZVS) conditions and the secondary diodes are turned-off under zero-current-switching (ZCS) conditions, the proposed converter has minimized switching losses. In addition, the input filter can be minimized due to a continuous input current, and an output inductor is absent in the proposed converter. Therefore, the proposed converter has the desired features, high efficiency and low profile, for a viable power supply for digital car audio amplifiers. A 60W industrial sample of the proposed converter has been implemented for digital car audio amplifiers with a measured efficiency of $88.3\%$ at nominal input voltage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.899-900
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• 2010