
77
THEORY OF OPERATION
Power Amplifier
Refer to the power amplifier channel block diagram below for the following information.
The 4400’s power amplifier section employs a number of protective devices and communication
circuits to ensure continued reliable operation, and to enable reporting and logging of any fault
conditions. In addition, there are several measurement circuits, whose primary purpose is to
provide information to Bose
®
FreeSpace
®
Installer™ software, enabling it to verify proper con-
figuration of the 4400 amplifier unit itself, and the speakers connected to it. The block
diagram provides a simplified view of one of the four channels, however many of the peripheral
functions are shared with one or more other channels. Refer to the schematics for more infor-
mation on exactly how the circuitry and functions throughout the units various PCB assemblies.
The power amplifier module itself consists of a single heatsink assembly with two circuit boards
mounted to it back-to-back. The upper PCB contains amplifier circuitry for output zones (chan-
nels) 1 and 2; the lower PCB contains amplifier circuitry for output zones 3 and 4, plus power
supply components shared by the entire unit. The power amplifier module receives analog
inputs and 2-way serial communications from the DSP and host processor sections via a 34-pin
ribbon cable. Power is also supplied from the Amp/PS module to the rest of the unit via this
cable.
Component designators in the block diagram refer to channel 4, see the schematic diagram to
find appropriate designators for other channels. The core of the power amplifier section is a pair
of high voltage MOSFETs (Q10 and Q11). These are driven by a “Class T” hybrid control mod-
ule from modulation pattern to drive Q10 and Q11’s gates. Contained in the hybrid module itself
are a proprietary analog/DSP IC operating from a 5 volt supply, and a pair of high
voltage half-bridge gate drive chips including charge pumps for high-side drive. There are also
other discrete components to perform level translation, gain scaling, buffering, etc.
Содержание FREESPACE 4400
Страница 87: ...87 Circuit Board Layout Diagrams Figure 12 DSP PCB Top Etch Board Layout Diagram ...
Страница 88: ...88 Circuit Board Layout Diagrams Figure 13 DSP PCB Bottom Etch Board Layout Diagram ...
Страница 90: ...90 Circuit Board Layout Diagrams Figure 18 Amplifier Upper PCB Top Etch Board Layout Diagram ...
Страница 91: ...91 Circuit Board Layout Diagrams Figure 19 Amplifier Upper PCB Bottom Etch Board Layout Diagram ...
Страница 92: ...92 Circuit Board Layout Diagrams Figure 20 Amplifier Power Supply Lower PCB Top Etch Board Layout Diagram ...
Страница 93: ...93 Circuit Board Layout Diagrams Figure 21 Amplifier Power Supply Lower PCB Bottom Etch Board Layout Diagram ...
Страница 100: ...100 TC9459F Volume Control PINOUT DIAGRAM BLOCK DIAGRAM PIN DESCRIPTION Integrated Circuit Diagrams ...