powersoft LiteMod - Protections; Power Supply Protections; Amplifier Protections

Fault protections are systems designed to protect peo-
ple from severe or fatal electric shocks and avoid severe
damages on the amplier or the loudspeakers in case of
electrical parameters out of scaling or critical changes in
environmental conditions.
The architecture of Powersoft’s ampliers encompass
several protection mechanisms triggered by harmful sig-
nal and temperature. Protection systems and triggers are
independently implemented in the power supply section
(power supply protection) and the amplier section (ampli-
er protections) in order to minimize system damages and
maximize efciency.
11 : 4.Power supply protections
Power supply protections aim to isolate a faulty section
in electrical power system from the rest of the device in
order to prevent the propagation of the fault and limit device
damages.
11 : 4.1. Primary AC mains overcurrent protection
AC main overcurrent are ltered by a 5 A time-lag fuse
(also known as time-delay or low blow-fuse). The purpose
of the time lag fuse is to allow the supply in electricity for
a short time before the fuse actually blows. If the time-lag
fuse blows out the amplier switch off; replace the fuse
with a proper 5 A time-lag fuse in order to restore the full
functionality of the amplier.
11 : 4. 2. Primary AC mains overvoltage protection
AC mains overvoltage threshold is set to 280 V
RMS
. If the
AC mains voltage exceeds 280 V
RMS
the primary power sup-
ply stop working, but the auxiliary remain active.
The power supply turns on again when the AC mains
voltage drops under 275 V
RMS
.
AC mains peak overvoltage are well tolerated by the
power supply: non damages can be caused to the system
even in case of severe peak overvoltage up to 380 V
RMS
.
11 : 4.3. Primary thermal protection
The temperature is detected at power supply’s MOSFETs
located on the Main Board bottom surface and at the pri-
mary transformer.
When the actual temperature of the power supply com-
ponents exceeds the safety threshold, the system switch off.
T (°C) V
-40 4.82
-35 4.76
-30 4.69
-25 4.6
-20 4.5
-15 4.37
-10 4.22
-5 4.05
0 3.86
5 3.66
10 3.43
15 3.2
20 2.96
25 2.71
30 2.47
35 2.24
40 2.02
45 1.82
50 1.63
55 1.46
T (°C) V
60 1.3
65 1.16
70 1.04
75 0.93
80 0.83
85 0.75
90 0.67
95 0.61
100 0.55
105 0.5
110 0.46
115 0.42
120 0.38
125 0.35
130 0.33
135 0.31
140 0.29
145 0.27
150 0.25
12
Protections
11 : 5.Amplifier protections
Amplier protections are triggered by audio signal cur-
rent and voltage – by comparing input and output – and
NTC, negative temperature coefcient, thermistors. NTC
thermistors provide thermal feedback: NTC resistance de-
creases with increasing temperature. TABLE 1 displays the
relationship between temperature and voltage drop across
NTC thermistors. NTC’s voltage drop for each channel are
routed to the respective TEMPMON contacts (pin #12 and
#23) on PL1001.
Since the temperature is detected on the PCB surface
it does not represent the actual module temperature: be
aware that some parts of the amplier may be at higher
temperature.
TABLE 1: Temperature to voltage relation-
ship on TEMPMON pins in PL1001
Protections | 9