JVC RX-D401, RX-D702 manual Background --What is PWM?, Heat Generation, PWM Pulse Width Modulation

Hybrid Feedback Digital Amplifier

JVC technologies for satisfying theBackgroundTHX Ultra2 certification-- What is PWM?

Background -- What is PWM?

RX-D702 RX-D402

*Also applies to RX-D401

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.

Switching Power Supply with Highly-Efficient Operations

OFFON

Power MOS FET

Switch

●Heat Generation

1.Loss from ON Impedance

2.Switching Loss

PWM (Pulse Width Modulation)

ON	+1
	+1
OFF
	0
OFF

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

ON -1 -1

Triangular

Waves

PWM

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