Gisen Audio at Guangzhou Prolightsound 2024
Design Considerations for Analog Input Class D
by:Gisen
2020-06-13
Output power per channel
? The maximum output power mainly depends on the power supply (output voltage and current) and the impedance of the speaker.
? The typical efficiency of Class D amplifiers is between 80% and 0%, reducing the need for power supply design.
? The maximum input signal level specifies the required power amplifier gain to meet the required output power.
? In order to optimize the suppression of noise, the gain should be as small as possible.
Output filter design
? When the speaker line is shorter than 10cm, most Class D amplifiers can operate without filters.
? When the speaker line is long, you can configure a second-order low-pass (LC) filter and make it as close as possible to the output pin of the filter.
? The filter must be designed for the specific speaker resistance, because the impedance of the load will affect the quality factor of the filter, the Q value.
? Ferrite beads can also eliminate UHF interference.
Printed circuit board (PCB) wiring
? The decoupling capacitor and output filter should be placed as close as possible to the amplifier chip.
? When using a ferrite bead filter, the LC filter should be placed as close to the chip as possible.
? Always connect PowerPAD ? terminals to power ground
? When the PowerPAD packaged device in the amplifier system uses a central 'star' ground, only a single connection point should be used to connect the analog ground to the power ground
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