Design to enhance the performance and reliability of high-power Class D audio amplifiers
The need for green energy standards, lower cost and higher audio fidelity is driving the use of Class D amplifiers in high power audio. Traditional analog implementations (such as Class AB topologies) are complex and inefficient, but they dominate the high-end audio market due to their high fidelity performance for audio. Class D systems are designed to be simpler, more efficient, and offer high fidelity capabilities comparable to analog amplifiers, and are rapidly closing the gap in the high-end audio market. A typical Class D audio system first converts an analog audio input signal into a digital PWM signal, performs power amplification in the digital domain, and then converts the digital signal into an analog audio signal output. As shown in Figure 1, the input audio signal is sent to a pulse width modulator (PWM), which consists of an operational amplifier and a comparator that generates a modulated duty cycle signal pair that is proportional to the instantaneous value of the audio input signal. Audio digitization. Figure 1: Basic block diagram of a Class D amplifier The PWM signal is properly level shifted and then sent to the gate driver, which controls the two-state power circuit consisting of MOSFETs (M1 and M2). The amplified signal is then passed through an output filter (eliminating the PWM carrier frequency), and finally only the amplified analog audio signal drives the speaker. By feeding the filter input signal back to the error amplifier input, external loop filtering reduces distortion and noise, further improving audio output fidelity. Class D amplifier design effect Conventional analog power amplifiers rely on linear amplification circuits and can easily cause high power losses. In contrast, Class D amplifiers can achieve power efficiencies of 90% or higher (depending on the design). This high efficiency benefit is inherent in Class D amplifier technology, which uses a binary conversion (usually a power MOSFET). These switches are either fully turned on or fully turned off, with little time spent on state transitions. Discrete switching action and low MOSFET on-resistance reduce I2R losses and improve efficiency. However, in practice, the switching transition time (dead time) must be long enough to avoid a sharp drop in efficiency when the two switches are operating simultaneously. High fidelity Audio fidelity can be defined as the integrity of sound reproduction. For audio systems, fidelity has always been synonymous with sound quality. At the same time, other indicators are also used to measure fidelity, and the measurement of some indicators is particularly challenging for designers. The two most challenging indicators are Total Harmonic Distortion (THD) and Noise (N), collectively referred to as THD+N. THD is an accurate measurement of the audio system, much like high fidelity itself. The error of the regenerative signal comes from the input frequency harmonics produced by other components, which is significantly different from the pure output signal. THD is the ratio of all excess harmonic frequency energy to the fundamental input frequency energy, typically measured at half power of a given system. THD performance is typically less than 0.1% for most non-high-fidelity audio applications, and discerning listeners typically require THD ratings as low as 0.05% or less. The output noise level is a measure of the noise floor level of the amplifier output without a signal input. For most speakers, the 100-500uV noise floor is inaudible within the normal listening range, and the noise floor of 1mV is too noisy, so THD+N is a measure of the audio fidelity of the amplifier. Very good indicator. Class D Driver IC: Features and Benefits Programmable dead time The dead time of the Class D amplifier (ie, the time period when both switches are off) directly affects efficiency and THD. Too short a dead time can cause a through current, reduce efficiency, and a long dead time will increase THD, which will adversely affect audio fidelity. The dead time must be accurately set to find the "best position" that optimizes both power efficiency and THD. Current typical high voltage audio drivers have inaccurate, overlapping dead time settings (ie, 1/n delay values). Therefore, most designers choose to use discrete components to handle dead time, which is costly and time consuming. A simple and economical solution is to integrate a gate driver with a high precision deadband generator. figure 2
Ganoderma
tea (Reishi Mushroom Tea/ Lingzhi Tea) is made of 100% USDA certified organic
Ganoderma Lucidum. The Ganoderma Lucidum ingredient used for this product comes
from our self-built organic Ganoderma farm located in Mt. Wuyi, Fujian, one of
the largest Ganoderma origins in China. The
whole cultivation process strictly follows the organic standards without any use
of pesticide, herbicide, and chemical fertilizer to ensure its highest quality
and efficacy.
This
organic Ganoderma Tea is very convenient to carry and make. Each box has 25
individually packaged tea bags. Just open
the sachet, put the tea bag in a cup and add hot water, a cup of warm and delicious
Ganoderma tea will be ready for you in just 1-2 minutes.
This
product has a unique mushroom flavor and a mellow sweet aftertaste. Different from other Herbal Tea on the market,
Ganoderma tea has many health benefits, such as enhancing overall immunity,
relieving stress, improving sleep quality and reducing allergy. It is gluten free, lactose free, and no additives or
preservatives whatsoever, therefore it Is suitable for all people especially
for people with low immunity or high stress.
Ganoderma Tea Ganoderma Tea,Reishi Tea,Reishi Mushroom Tea,Herbal Tea,Ganoderma Lucidum Tea,Lingzhi Tea Ganoherb International Inc. , http://www.ganoherb.us
