Digital audio power amplifier based on DPPC2006

With the digital process of electronic products continue to evolve, audio equipment (in particular, is one of the key products PA) digital also put on the agenda. Amplification products currently on the market have played a lot of "digital" label, but many of them simply the product of some digital processing, in the strict sense can only be called a digital amplifier, the real audio signal or analog. Digital amplifier is In the signal processing is used in digital audio signal, with the switch to amplify the Xinhao. digital power amplifier features the greatest efficiency Gao, pair of power supply and cooling of the requirements Dadajiangdi, in addition to output power, frequency response Kuan, volume small, high signal to noise ratio advantages. I designed a direct digital amplifier technology, a dedicated audio processing chip DPPC2006 treatment, and then formed by high-speed VMOSFET complementary symmetric H bridge circuit to enlarge the pure digital power amplifier.

Circuits

The program consists of before and after class at the front stage by the DPPC2006 processing input signals into digital PWM wave output from the high-speed VMOSFET after the class consisting of H bridge complementary symmetry amplifier and low-pass filter. At the same time with the ADC (ADC) CS5333 analog signals to achieve compatibility, volume control by the MCU AT89S51 completed, display, channel, mute and other control functions. machine component shown in Figure 1.

Digital audio power amplifier based on DPPC2006

Figure 1, digital audio power-based DPPC2006

Chip Works

DPPC2006 digital amplifier processing chip is a completely independent intellectual property rights in China Hi-Fi class audio amplifier digital 6-channel coding processing chip. The chip has a six-channel digital (PCM) input and an independent pulse width encoding (PWM) output; volume per channel can be independently adjusted, 124 changes in adjustable; 352.8kHz or 384kHz high switching frequency; support 24bit multi-pulse width difference coding, noise shaping, equilibrium Bridge technology; 6-channel data input, sampling rate support 32kHz ~ 768kHz; built-in S / PDIF receiver sample rate support 44.1kHz ~ 96kHz; built-in input data set selection circuit; for Electric +3 V ~ +5.5 V; package in the form of QFP100A.

Technical indicators

Frequency response ± 0.5dB (20Hz ~ 20kHz); dynamic range of 95dB; total harmonic distortion <0.02%. The chip can directly receiving CD, DVD and other digital audio output coaxial or optical digital audio signal, digital signal amplification, processing, single IC can zoom in six-channel, separated before and after class, after class with different MOSFET, can achieve a different output power. with DPPC2006 digital power amplifier circuit composed of simple, functional, can be selected for each input fiber and coaxial data can also choose CD, VCD, DVD and other products within the DATA, BCK and LRCK format data, can support high sampling rate of data input; no digital signal input of local, external audio A / D converter, it also could Enter DPPC2006 for the selection, application is very flexible.

Compatible analog signal

In order to analog signals compatible with the common, DPPC2006 digital input interface to receive the serial ADC output data. As long as the line shown in Figure 2, the digital audio data input format can work (or so feet aligned by the DPPC2006 the MO configuration options) . The program launched by CIRRUS's 26bit, 96kHz stereo audio-specific analog CS5333.

Digital audio power amplifier based on DPPC2006

Figure 2 serial audio data format

After the amplification level PWM

After the amplification stage PWM full control by the H bridge Complementary Symmetry MOS amplifier and low pass filter (LPF) constitute the actual circuit shown in Figure 3 (the figure is only one channel). Graph R307, C303, L303, C307, C308 for the EMC component; L301, L302, C304 for the filter circuit; R308, C305 matching circuit for the speaker.

1) H bridge amplifier. Here U6 input for the FET drive circuits using 74HC541 chips or days of Austria's DB802. Choose different currents of MOSFET, you can get 80W ~ 300W of output power.

Digital audio power amplifier based on DPPC2006

After the level PWM amplifier

2) low-pass filter. Using second-order LC filter, required frequency of filter cap ≥ 20kHz, in the pass band characteristics of the basic flat. EWB simulation software by using the simulation, be L, C of the better argument for the L301 = L302 = 22μH, C304 = 0.47μF.

Function Control

On DPPC2006 control achieved by the 51 Series MCU AT89S51, complete chip mode settings, channel selection, volume control and display functions of operation. The microcontroller with the ISP (in-system programmable) function, you can directly download the wire-line development, easy to use. Microcontroller control program flow shown in Figure 4. Digital audio power amplifier based on DPPC2006

Figure 4 microprocessor control program flow chart

Waveforms and test results

1) PWM waveform: PWM output waveform shown in Figure 5. Chart a) is not modulated PWM output waveform, b), c) to have modulated PWM output waveform. Can be seen from Figure 5, input signal amplitude change has been transformed into the output pulse width changes.

2) The power efficiency. Power efficiency in Table 1. Can see from Table 1, the average efficiency η = (76.8 +66.0 +76.9 +68.8 +7717)% / 5 = 73.24%. From the test data showed that compared with traditional analog amplifiers, greatly improved the efficiency digital power amplifier, power amplifier efficiency and maximum output power without distortion and theoretical calculations have some differences, which is H bridge output circuit, driving circuit Cunzai static caused by the loss, especially when the impact of small power output more apparent.

Digital audio power amplifier based on DPPC2006

Digital audio power amplifier based on DPPC2006

Figure 5 DPPC2006 chip PWM output waveform

Conclusion

The system uses direct digital amplification technology (DDX) of dedicated digital audio signal processing chip DPPC2006 amplification core, can be directly input S / PDIF coaxial or optical digital signal. Through internal operations, the PCM signal into a PWM signal to the high-speed transmission VMOSFET tube form and symmetry H bridge circuit amplifier, the output amplified two-channel audio signals. At the same time allow expansion interface, compatible with common analog input signal, the output can easily be extended to 6-channel surround. By using a different MOSFET, very easy to get 80W ~ 300W of output power, in theory, the average efficiency of 90% or more, and sometimes even completely without amplification level heat sink. Flexible use of MCU control, for quiet, digital volume control, display and other functions. Can be used in DVD machine built-in amplifier, car amplifier, high-end desktop, music center, computer multimedia and various multi-channel AV amplifier design, cost-effective high have a very broad application prospects.

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