POWER MODULE PWR207
(75W 6-Channel / 75W Twin Subwoofer)
(100W 6-Channel / 100W Twin Subwoofer)
TABLE OF CONTENTS
Class-D Amplifier circuit description ........................................................................................ 8-1
Exploded view + mechanical parts .......................................................................................... 8-2
SW-out (SPK II) Board - Circuit & layout diagrams (Twin Subwoofer versions only) ............. 8-3
Speaker (SPK I) Board - Circuit diagram ................................................................................. 8-4
Speaker (SPK I) Board - Componet & Chip layouts ................................................................ 8-5
Mains & ECO Stby Board - Circuit diagram ............................................................................. 8-6
Mains & ECO Stby Board - Component & Chip layouts .......................................................... 8-7
Mains & ECO Stby Board - Chip layouts Part A ...................................................................... 8-8
Mains & ECO Stby Board - Chip layouts Part B ...................................................................... 8-9
Supply Board - Circuit diagram .............................................................................................. 8-10
Supply Board - Component & Chip layouts ............................................................................8-11
Supply Board - Chip layout Part A ......................................................................................... 8-12
Supply Board - Chip layout Part B ......................................................................................... 8-13
Amplifier Board - Clock Generator & connector - circuit ....................................................... 8-14
Amplifier Board - Amplifier circuit ........................................................................................... 8-15
Amplifier Board - Bottom view ................................................................................................ 8-16
Amplifier Board - Top view ..................................................................................................... 8-17
Amplifier Board - Bottom view Part A ..................................................................................... 8-18
Amplifier Board - Bottom view Part B .................................................................................... 8-19
Amplifier Board - Top view Part C .......................................................................................... 8-20
Amplifier Board - Top view Part D .......................................................................................... 8-21
Electrical parts list - Mains, Supply, Speaker & SW-out ........................................................ 8-22
Electrical parts list - Amplifier board ...................................................................................... 8-23
8-1
8-1
6-channel class-D amplifier
Basic operation of a class-D amplifier
Basically, the output stage of a class-D amplifier outputs a continuous square wave swinging between positive and negative power supplies
with a fixed frequency (“clock” frequency) far beyond the audible range. The duty cycle of this square wave is modulated with the audio signal.
The output is followed by a low-pass filter which eliminates the clock frequency and allows only the audio signal going to the speaker. See
simplified drawing below.
Compared to a conventional power amplifier the benefits of the Class-D amplifier are:
• higher effiency
• lower power dissipation
• smaller heatsink required
• smaller mains transformer required
The main disadvantage of this concept is:
• The amplifier is operating with a high-frequency square wave at high amplitude and currents. This requires special precautions to prevent
excessive electromagnetic ratiation (EMC).
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