DC894C-C - Demo Manual

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
LT3825
DESCRIPTION
Demonstration circuit 894C-C is a 36V-72Vin,
synchronous flyback converter featuring the
LT3825. This circuit was designed specifically
to attain a high current, low ripple, synchronously rectified flyback to efficiently power 12V
loads at up to 5A from a typical telecom input
voltage range. This circuit features synchronous rectifier drive outputs, output voltage reg-
Table 1.
ulation without the need of an optocoupler,
self-starting architecture and input undervoltage lockout.
Design files for this circuit board are available. Call the LTC factory.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Performance Summary (TA = 25°C)
PARAMETER
CONDITION
VALUE
Minimum Input Voltage
36V
Maximum Input Voltage
72V
Output Voltage VOUT
VIN = 36V to 72V, IOUT = 0A to 5A
Maximum Output Current
12.0V
5A
Typical Output Ripple VOUT
VIN = 48V, IOUT = 5A
< 120mVP–P
Output Regulation
Over All Input Voltages and Output Currents
±1%
Peak Deviation with Load Step of 3.75A to 5A
(10A/us)
±250mV (< ±2.5%)
Load Transient Response
Settling Time
100us
Nominal Switching Frequency
Efficiency
200kHz
VIN = 48V, IOUT = 5A
92.5% Typical
OPERATING PRINCIPLES
The LT3825 controller exhibits a self-starting
capability. When an input voltage is applied, a
trickle charge resistor, R8, charges C10 (See
Figure 9) to power Vcc. Then, the IC begins a
controlled soft-start of the output voltage. As
this voltage begins to rise, Vcc power is quickly
taken over by T1, D2, and R7. When the softstart period is over, the LT3825 then regulates
output voltage by observing the pulses across
the auxiliary winding of T1 during the flyback
time. The Primary Gate drive (PG) and Synchronous Gate (SG) drive is then Pulse Width
Modulated (PWM) in order to keep the output
voltage constant. The synchronous gate drive
signal is transmitted to the secondary via the
small signal transformer, T2. The output of T2
then drives a discreet gate drive buffer, R26,
Q12, and Q13 in order to achieve fast gate
transition times, hence a higher efficiency.
The two-stage input filter, C25, L1, and C30 and
output filter, C1, C2, L2, and C29 are the reasons that this flyback has exceptionally low
conducted emissions.
1
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
QUICK START PROCEDURE
Demonstration circuit 894C-C is easy to set up
to evaluate the performance of the LT3825. Refer to Figure 1 for proper measurement equipment setup and follow the procedure below:
NOTE: When measuring the input or output volt-
age ripple, care must be taken to avoid a long
ground lead on the oscilloscope probe. Measure the output (or input) voltage ripple by touching the probe tip and probe ground directly
across the +Vout and –Vout (or +Vin and –Vin)
terminals. See Figure 2 for proper scope probe
technique.
3. Turn on the power at the input.
NOTE: Make sure that the input voltage never
exceeds 72V.
4. Check for the proper output voltage of 12V
5. Turn off the power at the input.
6. Once the proper output voltages are estab-
lished, connect a variable load capable of
sinking 5A at 12V to the output terminals
+Vout and –Vout. Set the current for 0A.
a. If efficiency measurements are desired, an
36V to 72V at a current of at least 2.5A to a
voltage of 36V. Then, turn off the supply.
ammeter or a resistor current shunt that is
capable of handling at least 5Adc can be
put in series with the output load in order to
measure the DC894C-C’s output current.
2. With power off, connect the supply to the in-
b. A voltmeter with a capability of measuring
1. Set an input power supply that is capable of
put terminals +Vin and –Vin.
a. Input voltages lower than 36V can keep the
converter from turning on due to the undervoltage lockout feature of the LT3825.
b. If efficiency measurements are desired, an
ammeter capable of measuring 2.5Adc can
be put in series with the input supply in order to measure the DC894C-C’s input current.
c. A voltmeter with a capability of measuring
at least 72V can be placed across the input
terminals in order to get an accurate input
voltage measurement.
at least 12V can be placed across the output terminals in order to get an accurate
output voltage measurement.
7. Turn on the power at the input.
NOTE: If there is no output, temporarily dis-
connect the load to make sure that the load is
not set too high.
8. Once the proper output voltage is estab-
lished, adjust the load within the operating
range and observe the output voltage regulation, ripple voltage, efficiency and other desired parameters.
2
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
Figure 1. Proper Measurement Equipment Setup
GND
VIN
Figure 2. Measuring Input or Output Ripple
3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
MEASURED DATA
Figures 3 through 8 are measured data for a typical DC894C-C. Figures 9 through 11 are schematics
and bill of materials
Efficiency vs. Load Current
94
92
Efficiency (%)
90
88
86
36Vin
84
48Vin
82
72Vin
80
78
76
74
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
Load Current (A)
Figure 3. Efficiency
Output Voltage vs. Load Current
12.25
Output Voltage (V)
12.15
12.05
36Vin
48Vin
72Vin
11.95
11.85
11.75
0
1
2
3
4
5
6
Load Current (A)
Figure 4. Regulation
4
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
Figure 5. Output Voltage Ripple (48Vin 5A)
Figure 6. Load Transient Response (10A/us)
5
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
Figure 7. Temp Data (48Vin, 5A, 100LFM airflow – front)
Figure 8. Temp Data (48Vin, 8A, 100LFM airflow – back)
6
E1
-VIN
E2
36V- 72V
+VIN
C30
22uF
100V
+
C25
2.2uF
100V
4.7uH
L1
R5
412K
1%
R14
15k
1%
R3
30.9k
1%
R20
12k
1%
R15
3.01k
8
PGDLY
UVLO
FB
R16
169k
1%
15
10
R7
68
0.125W
D2
BAS21LT1
VC C
2
TON
3
C10
47uF
20V
R8
47K
0.25W
R18
1.82k
1%
SYNC
5
+
ROC M P
14
0.1uF
C11
SG
1
U1
LT3825EFE
SG
16
PG
END LY
R19
100k
4
BAT760
D8
160
0.25W
R11
160
0.25W
R6
C13
0.1uF
47pF
VC
SENN
SENP
7.5k
R22
3.3n
C23
9
11
12
Q1
BSC320N20NS
C4
100pF
C17
OSC AP
7
SGN D/PGND
17
SF ST
6
CCM P
13
330p
C19
R9
0.012
0.5W
SG
470p
PA0184
T2
C8
0.1uF
R4
330
R2
15
0.25W
C3
T1
PA1736NL
BAT54
2.2nF D5
C20
R26
15
FMMT718
Q12
R13
10K
+VOUT
C7
4.7nF
250V
1uF
-VOUT
C29
12V @ 5A
SANYO
16CE150BS
C21
+VOUT
FMMT618
Q13
BSC028N06NS
Q3
C3225X5R1C226M
C1 C2
22uF
16V
L2
IHLP2525CZER1R0M
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
Figure 9. Simplified Schematic
7
-VIN
E2
C30
36V- 72V 22uF
100V
E1
+
L1
C12
OPT
4.7uH
R5
412K
1%
C25
2.2uF
100V
R14
15k
1%
R3
30.9k
1%
1%
R15
3.01k
R10
OPT
R20
12k
8
PGDLY
UVLO
FB
R16
169k
1%
15
10
R7
68
0.125W
D2
BAS21LT1
C10
47uF
20V
R8
47K
0.25W
R18
1.82k
1%
+
0.1uF
C11
SG
R1 0
U1
LT3825EFE
R19
100k
OPT
C18
47pF 10nF
C17
BAT760
D6
160
0.25W
R11
160
0.25W
R6
0.1uF
C13
VC
SENN
SENP
4
C23
7.5k
R22
3.3nF
9
11
12
123
R9
0.012
0.5W
BSC320N20NS 5 6 7 8
Q1
C4
100pF
CCMP
+VIN
2
VC C
TON
3
SYN C
5
ROCM P
14
1
SG
16
PG
EN D LY
4
OSC AP
7
SFST
6
S G N D /P G N D
17
D8
13
330p
C19
R2
15
0.25W
3
4
6
2
1
5
SG
1
8
T2
PA0184
C8
0.1uF
321
4
5
4
C1
22uF
16V
R26
15
4
OPT
OPT
BAT54
R13
10K
FMMT618
Q13
R27
OPT
OPT
Q3
D7
BSC028N06NS
C6
C5
2.2nF D5
C20
FMMT718
Q12
321
8765
C2
22uF
16V
1uF
C21
L2
C1, C2: C3225X5R1C226M IHLP2525CZER1R0M
8765
Q4
OPT
R4
330
470p
C3
10
11
12
7
8
9
T1
PA1736NL
R28
0
+VOUT
C7
4.7nF
250V
E4
-VOUT
C29
SANYO 12V @ 5A
16CE150BS
E3
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
Figure 10. Full Board Schematic
8
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
Item
Qty
Ref-Des
Description
Manufacturer's Part Number
REQUIRED CIRCUIT COMPONENTS1
1
2
C1,C2
CAP, 1210 22uF 20% 16V X5R
2
1
C3
CAP, 1206 470pF 5% 100V COG
3
1
C4
CAP, 1206 100pF 10% 630V COG
4
1
C7
CAP, 4.7nF 10% 250V X7R
5
3
C8,C11,C13 CAP, 0603 0.1uF 10% 50V X7R
6
1
C10
CAP, 6032 47uF 20% 20V TANT
7
0
C12
CAP, 0603 470pF 10% 25V NPO
8
1
C17
CAP, 0603 47pF 10% 25V NPO
9
1
C19
CAP, 0603 330pF 5% 50V COG
10
1
C20
CAP, 0603 2.2nF 5% 50V X7R
11
1
C21
CAP, 1206 1uF 20% 25V X7R
12
1
C23
CAP, 0603 3.3nF 10% 25V X7R
13
1
C25
CAP, 1812 2.2uF 10% 100V X7R
14
1
C29
CAP, 150uF 20% 16V
15
1
D2
DIODE, BAS21-7
16
1
D5
DIODE, SCHOTTKY
17
1
D8
DIODE, SCHOTTKY
18
1
L2
IND, 1.0uH
19
1
Q1
MOSFET, N-CH 200V 36A TDSON-8
20
1
Q3
MOSFET N-CH 60V 23A TDSON-8
21
1
Q12
XSTR, PNP
22
1
Q13
XSTR, NPN
23
1
R2
RES, 1206 15 OHMS 5% 1/4W
24
1
R3
RES, 0603 30.9k OHMS 1% 1/10W
25
1
R4
RES, 0603 330 OHMS 5% 1/10W
26
1
R5
RES, 0603 412K OHMS 1% 1/8W
27
2
R6,R11
RES, 1206 160 OHMS 5% 1/4W
28
1
R7
RES, 0805 68 OHMS 5% 1/8W
29
1
R8
RES, 1206 47K OHMS 5% 1/4W
30
1
R9
RES, 1206 0.012 OHMS 1% 0.5W
31
1
R13
RES, 0603 10K OHMS 5% 1/10W
32
1
R14
RES, 0603 15K OHMS 1% 1/10W
33
1
R15
RES, 0603 3.01K OHMS 1% 1/10W
34
1
R16
RES, 0603 169K OHMS 1% 1/10W
35
1
R18
RES, 0603 1.82K OHMS 1% 1/10W
36
1
R19
RES, 0603 100K OHMS 5% 1/10W
37
1
R20
RES, 0603 12K OHMS 5% 1/10W
38
1
R22
RES, 0603 7.5K OHMS 5% 1/10W
39
1
R26
RES, 0603 15 OHMS 5% 1/10W
40
1
T1
XFMR, PA1736NL
41
1
T2
XFMR, 1.4mH MIN, 50KHz
42
1
U1
IC, LT3825EFE
TDK C3225X5R1C226M
AVX 12061A471JAT
TDK C3216COG2J101K
MURATA GA343DR7GD472KW01L
TDK C1608X7R1H104K
AVX TAJC476M020R
AVX 06033A471KAT2A OPTION
AVX 06033A470KAT2A
AVX 06035A331JAT
AVX 06035C222JAT
AVX 12063C105MAT2A
AVX 06033C332KAT
TDK C4532X7R2A225K
SANYO 16CE150BS
DIODES INC. BAS21-7-F
DIODES INC. BAT54-7
DIODES INC. BAT760-7
VISHAY IHLP2525CZER1R0M
INFINEON, BSC320N20NS3 G
INFINEON, BSC028N06NS
ZETEX FMMT718TA
ZETEX FMMT618TA
VISHAY CRCW120615R0JNEA
VISHAY CRCW060330K9FKEA
VISHAY CRCW0603330RJNEA
VISHAY CRCW0603412KFKEA
VISHAY CRCW1206160RJNEA
VISHAY CRCW0805668R0JNEA
VISHAY CRCW120647K0JNEA
IRC LRC-LRF1206LF-01-R012-F
VISHAY CRCW060310K0JNEA
VISHAY CRCW060315K0FKEA
VISHAY CRCW06033K01FKEA
VISHAY CRCW0603169KFKEA
VISHAY CRCW06031K82FKEA
VISHAY CRCW0603100KJNEA
VISHAY CRCW060312K0JNEA
VISHAY CRCW06037K50JNEA
VISHAY CRCW060315R0JNEA
PULSE PA1736NL
PULSE PA0184NL
LINEAR TECH LT3825EFE
ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS2
43
0
C5
CAP, 1210 OPTION
44
0
C6
CAP, 1210 47uF 20% 6.3V X5R OPTION
45
0
C18
CAP, 0603 10nF 10% 25V X7R OPTION
OPTION
TDK C3225X5R0J476MT OPTION
AVX 06033C103KAT OPTION
9
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 894C-C
36V-72VIN, SYNCHRONOUS FLYBACK
46
47
48
49
50
51
52
53
1
0
1
0
1
0
0
1
C30
D7
L1
Q4
R1
R10
R27
R28
CAP, 22uF 100V
DIODE, OPTION
IND, 4.7uH
MOSFET N-CH 60V 23A TDSON-8
RES, 0603 0 OHM JUMPER
RES, OPTION
RES, OPTION
RES, 0603 0 OHM JUMPER
SUN ELECTRIC 100ME22AX
OPTION
VISHAY IHPL2525CZER4R7M01
INFINEON, BSC028N06NS OPTION
VISHAY CRCW06030000Z0EA
OPTION
OPTION
VISHAY CRCW06030000Z0EA
Notes:
1. Required Circuit Components are those parts that are required to implement the circuit function
2. Additional Demo Board Circuit Components are those parts that provide added functionality for the demo
board but are or may not be required in the actual circuit.
Figure 11. Bill of Materials
10
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