13
TD-001517-01
K.2 Series Service Manual
Power supply
The amplifier module’s switch mode power supply is a regulated, fixed frequency, active clamp flyback. It is similar to a typ-
ical flyback converter except that when the main switch is off another switch turns on and recovers the transformer energy
into a resonant tank. A typical flyback power supply has good cross-regulation and can operate over a wide input voltage
range, but the power dissipation of a passive clamp limits the power level a flyback can reasonably output; adding the active
clamp allows a flyback converter to scale to much higher power levels. The power supply accepts universal AC voltages, the
incoming mains voltage is bridge rectified to DC and stored in a bank of 2 primary capacitors in series. This rectified voltage
varies directly with mains voltage.
The main and clamp FETs, operating at approximately188 kHz, couple energy to the secondary diodes through the trans-
former. The regulated ±77V secondary voltage is stored in a pair of secondary capacitors, one per rail. Regulation is taken
across the 144V secondary voltage, relying on proper circuit operation to keep the rails balanced. Adjusting the duty
cycle of the PWM signal driving the power supply FETs keeps the power supply’s output voltage constant regardless of
changes to input voltage or load.
Auxiliary voltages of ±15V, ± 5V, and +12VLOW are created with separate transformer windings from the main secondary
rails, but all windings are tied together at ground. Under load, the amplifiers will pull energy from the main rails and the
power supply will increase the duty cycle to compensate and keep the main rails at ±77V; this means the housekeeping
voltages increase under load. The auxiliary voltages are used to power numerous circuits across the amplifier module, like
the op-amps, DSP, microcontroller, and amplifier drivers.
22AWG AUX
100X40AWG LITZ PRI
DNI
DNI
EE42 3C90
100X40AWG LITZ SEC
DNI
CURRENT SENSE
321MW EACH
DNI
DNI
(RC) CLAMP MODE
56K FOR PASSIVE
1 PCNT
2W
5 PCNT
100.0PF
5 PCNT
500.0 VDC
330
2W
330
1 PCNT
1 PCNT
1/8W
10K
5 PCNT
1/10W
10.0K
56.2K
1 PCNT
1W
0.68UF
5 PCNT
250V
220PF
100
20 PCNT
1W
1 PCNT
1 PCNT
1UF
MMBTA56
2.00K
1 PCNT
25V
10 PCNT
1/10W
1 PCNT
1000UF
20 PCNT
10 PCNT
10 PCNT
500V
200V
10 PCNT
500V
0.022UF
500V
0.022UF
0.022UF
500V
200V
KBU1005
10 PCNT
1N4148
100K
10K
1W
5 PCNT
10K
5 PCNT
5 PCNT
10K
1W
1/8W
10 PCNT
1W
5 PCNT
RB751S40T1
10
10K
100K
1/8W
0.0022UF
10
RB751S40T1
1/16W
STP11NM60FD
100K
1000UF
10K
1W
1 PCNT
1W
25V
1W
0.022UF
1/10W
1 PCNT
500V
20 PCNT
5 PCNT
1 PCNT
1/8W
1 PCNT
100K
1 PCNT
1 PCNT
10.0K
1/8W
1 PCNT
1/16W
RB751S40T1
10 PCNT
0.022UF
1W
10 PCNT
1UF
22.6
100
250VAC
100.0PF
1W
100
STP45N65M5
250VAC
100.0PF
5 PCNT
500.0 VDC
1 PCNT
100.0PF
5 PCNT
500.0 VDC
500.0 VDC
1 PCNT
100
1W
C122
C121
C126
C127
R129
R105
R147
R146
R165
C31
C55
R121
R7
R45
R52
R123
R150
R161
R162
T2
T2
C116
Q13
D40
Q18
R164
D35
D27
R166
C52
C124
Q14
R67
C128
T3
D51
T1
C137
T3
R152
R144
R172
R145
C132
C114
C112
BR1
C130
R157
R188
R189
C113
LINE_UV
AUX_OUT
QM_DR
PRI_LO
XF-MID
PSU-VSW
PRI_HI
PRI_MID
VIN
11
10
9
3
2
1
3
1
4
3
6
4
B2
B1
-
AC2
AC1
+
SEC 5
SEC 1
PRI 1
PRI 2
Figure 4.3.3 - Active flyback converter circuit used in the K.2 series SMPS
Figure 4.3.4 - SMPS circuit, PCB
AUX OUTS
DNI
VAC MONITOR = 657UA
+3.3VD CURRENT = 10.21MA + 270UA = 10.48MA
IN 50C AMBIENT, JUNCTION IS 95C
ON 10MM SQ PAD, THETAJA = ~55C/W
N15V RAIL IS AT +13.5V
TOTAL = 95.15MA (809MW)
+5VA CURRENT = 95.15MA
DNI
2X IRS2092 = 11MA * 2 = 22MA
NOMINAL -15V RAIL IS AT -13.5V
THETAJA = 180C/W
JUNCTION AT 25C=33
2X LO LEDS = 500UA * 2 = 1MA
HF DEADTIME = 948UA
TOTAL = 91MA
+12VLOW CURRENT:
HF + LF = 89MA (MEASURED)
-5VA CURRENT = 22MA
L79L05 = 6.25MA
MC33078 = 5.5MA
TOTAL = 22MA (187MW)
WITH ZERO COPPER
-5VA CURRENT:
+15V CURRENT:
DNI
-15V CURRENT:
TOTAL = 107.45MA
L78M05 = 6.8MA
MC33078 = 5.5MA
TOTAL = 33.75MA
100.0VDC
1.0UF
10PCT
100.0VDC
1.0UF
10PCT
IRLML2502
1000UF
0.1UF
22UF
25V
ES1D
25V
1000UF
20 PCNT
10UF
20 PCNT
6.3V
0.1UF
5 PCNT
243
1 PCNT
10 PCNT
200V
5A
243
1/10W
120PF
5 PCNT
200V
5A
1/10W
L78M05
MBR230
25V
10 PCNT
0.1UF
10 PCNT
25V
1N4148
10 PCNT
SMD110PL
10UF
LM79L05AC
20 PCNT
6.3V
25V
1 PCNT
22UF
NA
NA
0
25V
10 PCNT
24V
24V
20 PCNT
25V
1000UF
20 PCNT
ES1D
25V
0.1UF
25V
25V
0.1UF
10 PCNT
20 PCNT
1000UF
25V
SMD110PL
1 PCNT
2.00K
1/10W
2.00K
1 PCNT
1/10W
2.00K
1 PCNT
10K
1/16W
SMD110PL
1 PCNT
1N4148
MBR230
10 PCNT
SMD110PL
1/10W
1 PCNT
2.00K
SMD110PL
1/10W
120PF
R99
R73
D15
TP1
TP2
TP12
TP11
C95
R71
R56
C83
C82
D12
C4
C6
D1
U4
R156
D62
C94
D61
C92
C91
C86
C56
C19
D29
Q16
U7
C15
R70
C72
C74
C125
D37
D20
D36
D31
R68
C49
R69
C50
D32
F2
F1
T2
+12VLOW
1
7
6
3
2
5
3
1
2
8
7
6
VSS
A1
-5VA
GND
VIN4
VIN3
VIN2
VIN1
VOUT
A1
+15V
+15V
OUT
+5VA
OUT
GND
IN
-15V
SEC 3
SEC 2
Figure 4.3.5 - Auxiliary voltages on the secondary
Summary of Contents for K.2 series
Page 2: ...2 QSC LLC...
