Bose PACKLITE A1 Manual page 50

7. Protection Mechanism Summary
Fault Detection
Input Signal Output signal level re:
Level 0.865 of amplifier DC
Clipping supply
Output Output MOSFET 'on'
Signal voltage
Current
Limit
Output Detects output
Over-current
current limit over a
/O.C. (short settable time
circuit, constant
saturation)
Zobel
Over-voltage across
Protection
Zobel resistor
Thermal External Negative
Temperature
Coefficient resistor -
threshold detection
with hysteresis
Amp DC Percentage of
voltage amplifier DC supply
over/under voltage (typically
135%). Under voltage
detection optional to
insure controlled
startup.
Control Percentage of 5V
Voltage
voltage
(5 Vdc) DC
over / under
Converter Over-current
Converter
Thermal
THEORY OF OPERATION
What shuts
down
Per channel None
Per MOSFET None
Per channel OC
Shutdown OC
per channel
Both TH
amplifiers
Both EN
amplifiers
Both EN
amplifiers
System None
System None
50
Indicator Recovery when
Output fault is removed
Immediate
Immediate
Time settable by
resistor value
Time settable by
resistor value
System turns
back on when
NTC when
voltage above
threshold
(depends on
thermal constant
of system)
Capacitors are
given a discharge
path to prevent
long recovery
time - but enable
circuit has long
recovery
Immediate
Immediate
Depends on
thermal constant
of system
Notes Fault
LED
Detection NO
threshold tied to
DC over/under
voltage threshold
FET is shut off for NO
short time (1.25
usec) then
restored causing
"self-oscillation"
Time constants RED
shared with Zobel
protection
Shared time RED
constant with OC
One NTC resistor RED
per system - will
be two
Detection NO
threshold tied to
input signal
clipping threshold
NO
NO
NO