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|Description||9-W STEREO CLASS-D AUDIO POWER AMPLFIER WITH DC VOLUME CONTROL|
|TPA3002D2 Datasheet PDF : 41 Pages |
SLOS402C − DECEMBER 2002 − REVISED JANUARY 2004
This section focuses on the class-D operation of the TPA3002D2.
Traditional Class-D Modulation Scheme
The traditional class-D modulation scheme, which is used in the TPA032D0x family, has a differential output
where each output is 180 degrees out of phase and changes from ground to the supply voltage, VCC. Therefore,
the differential prefiltered output varies between positive and negative VCC, where filtered 50% duty cycle yields
0 V across the load. The traditional class-D modulation scheme with voltage and current waveforms is shown
in Figure 31. Note that even at an average of 0 V across the load (50% duty cycle), the current to the load is
high, causing high loss, thus causing a high supply current.
Across Load 0 V
Figure 31. Traditional Class-D Modulation Scheme’s Output Voltage and
Current Waveforms Into an Inductive Load With No Input
TPA3002D2 Modulation Scheme
The TPA3002D2 uses a modulation scheme that still has each output switching from 0 to the supply voltage.
However, OUTP and OUTN are now in phase with each other with no input. The duty cycle of OUTP is greater
than 50% and OUTN is less than 50% for positive output voltages. The duty cycle of OUTP is less than 50%
and OUTN is greater than 50% for negative output voltages. The voltage across the load sits at 0 V throughout
most of the switching period, greatly reducing the switching current, which reduces any I2R losses in the load.
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