JVC RX-D702 Technical Manual page 44

Hybrid Feedback Digital Amplifier Hybrid Feedback Digital Amplifier
JVC technologies for satisfying the THX Ultra2 certification
Pulse Width Modulation (PWM) is a method of digitally encoding analog
signal levels. In the process, continuously varying value of input audio
signals is detected based on the reference voltage (Vref) by comparing
the signals with triangular waves. When the value is higher than Vref
level, the pulse is switched "ON", and when it gets below Vref, it's turned
"OFF". The higher than Vref the value is, the longer the pulse is kept
"ON". The lower than Vref the value is, the longer the pulse is left "OFF".
Thus, square-shaped waves are generated, representing either "ON" or
"OFF" state of the pulse -- length of the "ON" and "OFF" pulses
expresses the value of audio signals with respect to the Vref levels.
These waves are called "PWM signals". Precision of the PWM signals is
one of the elements that determine the sound quality delivered by a
digital amplifier. This is why "feedback" process is essential for delivering
high-quality sound.
PWM (Pulse Width Modulation)
+1
ON
+1
OFF
0
OFF
-1
ON
-1
Background -- What is PWM?
Background -- What is PWM?
Generation of PWM Signals
1. Values of input audio signals are detected by
comparison with triangular waves.
2. High-precision triangular waves are necessary.
Input Audio
Signals
Comparator
PWM
Triangular
Waves
RX-D702
Switching Power Supply with
Highly-Efficient Operations
OFF ON
Power MOS FET
Switch
● Heat Generation
1. Loss from ON Impedance
2. Switching Loss
RX-D402
*Also applies to RX-D401
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