LM5045 [NSC]
Input operating range: 36V to 75V Board size: 2.28 x 1.45 x 0.5 inches; 输入电压范围： 36V至75V主板尺寸： 2.28 X 1.45 X 0.5英寸
| 型号： | LM5045 |
| 厂家： | 
National Semiconductor |
| 描述： | Input operating range: 36V to 75V Board size: 2.28 x 1.45 x 0.5 inches |
| 文件： | 总12页 (文件大小：3057K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
National Semiconductor
Application Note 2111
Ajay Hari
LM5045 Evaluation Board
February 23, 2011
Introduction
Theory of Operation
The LM5045 evaluation board is designed to provide the de-
sign engineer with a fully functional power converter based
on the full-bridge topology to evaluate the LM5045 PWM con-
troller. The evaluation board is provided in an industry stan-
dard quarter brick footprint.
Power converters based on the full-bridge topology offer high-
efficiency and good power handling capability up to 500W.
Figure 1 illustrates the circuit arrangement for the full-bridge
topology. The switches, in the diagonal, Q1,Q3 and Q2,Q4
are turned alternatively with a pulse width determined by the
input and output voltages and the transformer turns ratio.
Each diagonal (Q1 and Q3 or Q2 and Q4), when turned ON,
applies input voltage across the primary of the transformer.
The resulting secondary voltage is then rectified and filtered
with an LC filter to provide a smoothened output voltage. In a
full-bridge topology, the primary switches are turned on alter-
natively energizing the windings in such a way that the flux
swings back and forth in the first and the third quadrants of
the B-H curve. The use of two quadrants allows better utiliza-
tion of the core resulting in a smaller core volume compared
to the single-ended topologies such as a forward converter.
Further, in a half-bridge topology, during power transfer when
one of the primary switches is active, the voltage across the
primary of the power transformer is 1/2 the input voltage (VIN)
compared to a full VIN in a full-bridge topology. Therefore, for
a given power, the primary current will be half as much for the
full-bridge as compared to the half-bridge. The reduced pri-
mary current enables higher efficiency as compared to a half-
bridge at high load currents.
The performance of the evaluation board is as follows:
•
•
•
•
•
•
•
•
•
Input operating range: 36V to 75V
Output voltage: 3.3V
Measured efficiency at 48V: 92% @ 30A
Frequency of operation: 420kHz
Board size: 2.28 x 1.45 x 0.5 inches
Load Regulation: 0.2%
Line Regulation: 0.1%
Line UVLO (34V/32V on/off)
Hiccup Mode Current Limit
The printed circuit board consists of 6 layers; 2 ounce copper
outer layers and 3 ounce copper inner layers on FR4 material
with a total thickness of 0.062 inches. The unit is designed for
continuous operation at rated load at <40°C and a minimum
airflow of 200 CFM.
30146201
Simplified Full-Bridge Converter
© 2011 National Semiconductor Corporation
301462
www.national.com
The secondary side employs synchronous rectification
scheme, which is controlled by the LM5045. In addition to the
basic soft-start already described, the LM5045 contains a
second soft-start function that gradually turns on the syn-
chronous rectifiers to their steady-state duty cycle. This func-
tion keeps the synchronous rectifiers off until the error
amplifier on the secondary side soft-starts, allowing a linear
start-up of the output voltage even into pre-biased loads.
Then the SR output duty cycle is gradually increased to pre-
vent output voltage disturbances due to the difference in the
voltage drop between the body diode and the channel resis-
tance of the synchronous MOSFETs. Once the soft-start is
finished, the synchronous rectifiers are engaged with a non-
overlap time programmed by the RD1 and RD2 resistors.
Feedback from the output is processed by an amplifier and
reference, generating an error voltage, which is coupled back
to the primary side control through an opto-coupler. The
LM5045 evaluation board employs peak current mode control
and a standard “type II” network is used for the compensator.
will give inaccurate measurements. This is especially true for
accurate efficiency measurements.
Source Power
The evaluation board can be viewed as a constant power
load. At low input line voltage (36V) the input current can
reach 3.5A, while at high input line voltage (72V) the input
current will be approximately 1.5A. Therefore, to fully test the
LM5045 evaluation board a DC power supply capable of at
least 85V and 4A is required. The power supply must have
adjustments for both voltage and current.
The power supply and cabling must present low impedance
to the evaluation board. Insufficient cabling or a high
impedance power supply will droop during power supply ap-
plication with the evaluation board inrush current. If large
enough, this droop will cause a chattering condition upon
power up. This chattering condition is an interaction with the
evaluation board under voltage lockout, the cabling
impedance and the inrush current.
Powering and Loading
Considerations
Loading
An appropriate electronic load, with specified operation down
to 3.0V minimum, is desirable. The resistance of a maximum
load is 0.11Ω. The high output current requires thick cables!
If resistor banks are used there are certain precautions to be
taken. The wattage and current ratings must be adequate for
a 30A, 100W supply. Monitor both current and voltage at all
times. Ensure that there is sufficient cooling provided for the
load.
When applying power to the LM5045 evaluation board certain
precautions need to be followed. A misconnection can dam-
age the assembly.
Proper Connections
When operated at low input voltages the evaluation board can
draw up to 3.5A of current at full load. The maximum rated
output current is 30A. Be sure to choose the correct connector
and wire size when attaching the source supply and the load.
Monitor the current into and out of the evaluation board. Mon-
itor the voltage directly at the output terminals of the evalua-
tion board. The voltage drop across the load connecting wires
Air Flow
Full power loading should never be attempted without pro-
viding the specified 200 CFM of air flow over the evaluation
board. A stand-alone fan should be provided.
30146202
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2
When applying power to the LM5045 evaluation board a cer-
tain sequence of events occurs. Soft-start capacitor values
and other components allow for a minimal output voltage for
a short time until the feedback loop can stabilize without over-
shoot. Figure 2 shows the output voltage during a typical start-
up with a 48V input and a load of 25A. There is no overshoot
during start-up.
Powering Up
It is suggested that the load be kept low during the first power
up. Set the current limit of the source supply to provide about
1.5 times the wattage of the load. As soon as the appropriate
input voltage is supplied to the board, check for 3.3 volts at
the output.
A most common occurrence, that will prove unnerving, is
when the current limit set on the source supply is insufficient
for the load. The result is similar to having the high source
impedance referred to earlier. The interaction of the source
supply folding back and the evaluation board going into un-
dervoltage shutdown will start an oscillation, or chatter, that
may have undesirable consequences.
A quick efficiency check is the best way to confirm that ev-
erything is operating properly. If something is amiss you can
be reasonably sure that it will affect the efficiency adversely.
Few parameters can be incorrect in a switching power supply
without creating losses and potentially damaging heat.
Over Current Protection
30146204
Conditions: Input Voltage = 48V
The evaluation board is configured with hiccup over-current
protection. In the event of an output overload (approximately
38A) the unit will discharge the SS capacitor, which disables
the power stage. After a delay, programmed by the RES ca-
pacitor, the SS capacitor is released. If the overload condition
persists, this process is repeated. Thus, the converter will be
in a loop of shot bursts followed by a sleep time in continuous
overload conditions. The sleep time reduces the average in-
put current drawn by the power converter in such a condition
and allows the power converter to cool down.
Output Current = 25A
Trace 1: Output Voltage Volts/div = 1V
Horizontal Resolution = 2.0 ms/div
FIGURE 2. Soft-Start
Performance Characteristics
Once the circuit is powered up and running normally, the out-
put voltage is regulated to 3.3V with the accuracy determined
by the feedback resistors and the voltage reference. The fre-
quency of operation is selected to be 420 kHz, which is a good
comprise between board size and efficiency. Please refer to
the figure 1. for efficiency curves.
100
36V
90
30146205
48V
Conditions: Input Voltage = 48V
80
Output Current = 15A to 22.5A to 15A
Upper Trace: Output Voltage Volts/div = 100mV
Lower Trace: Output Current = 5A/div
Horizontal Resolution = 200 µs/div
72V
V
= 3.3V
OUT
70
60
50
FIGURE 3. Transient Response
5
7
9 11 13 15 17 19 21 23 25 27 29
LOAD CURRENT (A)
30146203
FIGURE 1. Application Board Efficiency
3
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Figure 4 shows typical output ripple seen directly across the
output capacitor, for an input voltage of 48V and a load of 30A.
This waveform is typical of most loads and input voltages.
30146208
Conditions: Input Voltage = 72V
Output Current = 30A
Trace 1: SW1 Node (Q2 Drain) Voltage Volts/div = 20V
Horizontal Resolution = 1 µs/div
30146206
Conditions: Input Voltage = 48V, Output Current = 30A
FIGURE 6. Switch Node Waveforms
Trace 1: Output Voltage Volts/div = 50mV
Bandwidth Limit = 20MHz
Horizontal Resolution = 2 µs/div
Figure 7 shows a typical startup of the LM5045 into a 2V pre-
biased load. Trace 2 represents the output current that is
monitored between the output caps of the power converter
and the 2V pre-bias voltage supply. It can be inferred from the
Trace 2 that the SR MOSFET's do not sink any current during
the power-up into pre-biased load.
FIGURE 4. Output Ripple
Figures 5 and 6 show the typical SW node voltage waveforms
with a 25A load. Figure 5 shows an input voltage represents
an input voltage of 48V and Figure 6 represents an input volt-
age of 72V.
30146207
Conditions: Input Voltage = 48V
30146209
Output Current = 30A
Conditions: Input Voltage = 48V, Output Pre-Bias = 2V
Trace 1: SW1 Node (Q2 Drain) Voltage Volts/div = 20V
Horizontal Resolution = 1µs/div
Trace 1 (Channel 4): Output Voltage Volts/div = 1V
Trace 2 (Channel 2): Output Current Amps/div = 200mA
Trace 3 (Channel 3): SR Gate Voltage Volts/div = 5V
FIGURE 5. Switch Node Waveforms
FIGURE 7. Soft-Start into 2V Pre-Biased Load
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Bill of Materials
Item
Designator
AA
Description
Part Number
1
2
3
4
5
6
7
Printed Circuit Board
C1, C2, C3, C4
C5, C35
C7, C8
Ceramic 2.2uF, X7R, 100V, 10%, 1210 GRM32ER72A225KA35L
Ceramic 2.2uF, X7R, 16V, 10%, 0805
Ceramic, 2.2uF, X5R, 25V, 10%, 0805
Ceramic, 1uF, X7R, 50V, 10%, 0805
Ceramic 2.2uF 10V X7R 0603
GRM21BR71C225KA12L
GRM21BR71E225KA73L
GRM21BR71H105KA12L
GRM188R71A225KE15D
C1608X7R1C105K
C9
C6
C10, C11
Ceramic, 1uF, X7R, 16V, 10%, 0603
Ceramic,0.1uF, X7R, 25V, 10%, 0603
Ceramic, X7R,2000V, 2700pF,10%
8
9
C12, C15, C21, C32
06033C104KAT2A
C13
C14
C1808C272KGRACTU
10
11
Ceramic 0.1uF, 100V, +/-10%, X7R, 0603 GRM188R72A104KA35D
C16, C23
Ceramic, C0G/NP0 470pF, 100V, 10%, 12061A471KAT2A
1206
12
C17, C39
Cap 330uF, 4V, AL, 4V, 20%, 0.012 Ohm EEF-UE0G331R
ESR
13
14
C18, C19, C20
C22
Ceramic 47uF, X7R, 6.3V, 10%
GCM32ER70J476KE19L
C1005X7R1C223K
Ceramic 0.022uF, 16V, +/-10%, X7R,
0402
15
C34, C36
Ceramic 1000pF, 25V, +/-5%, C0G/NP0, C1005C0G1E102J
0402,
16
17
18
C26, C27
C28, R20, D4, L3
C29
Ceramic1uF, 16V, +/-20%, X7R, 0805
NU
GRM21BR71C105MA01L
NU
Ceramic 47pF, 50V, +/-5%, C0G/NP0,
0402
GRM1555C1H470JZ01
19
20
21
22
C30, C40
C24
Ceramic 100pF, C0G/NP0, 50V, 5%,
0603
C1608C0G1H101J
CAP, CERM, 0.056uF, 6.3V, +/-10%,
X7R, 0402
C0402C563K9RACTU
C25, C31, C37, C33
C38
CAP, CERM, 0.01uF, 16V, +/-10%, X7R, C1005X7R1C1103K
0402
CAP, CERM, 0.47uF, 6.3V, +/-20%, X5R, C1005X5R0J474K
0402
23
24
D2
Vr = 30V, Io = 1A, Vf = 0.38V
B130LAW-7-F
D3, D7, D10, D14
Vr = 40V, Io = 0.2A, Vf = 0.65V, Common CMPSH-3CE
Cathode
25
26
27
D5
D6
SMT 5.1V Zener Diode
SMT 8.2V Zener Diode
MMSZ5231B
CMHZ4694
D8, D12
Vr = 100V, Io = 1A, Vf = 0.77V, Schottky DFLS1100-7
diode
28
D9, D13
Vr = 40V, Io = 0.2A, Vf = 0.65V, Common CMPSH-3AE
Anode
29
30
31
32
D11
D16
D17
L1
SMT 11V Zener Diode
CMHZ4698
Vr = 30V, Io = 0.2A, Vf = 0.7V, Schottky BAT54WS-7-F
Diode, Zener, 4.7V, 250mW, SOD-323
CMDZ4L7
Shielded Drum Core, 2.2uH 4.15A,
0.0165 Ohm
DR73-2R2-R
33
34
35
L2
L3
L4
Shielded Drum Core, 0.08A, 11 Ohm
NU
LPS5030-225MLB
NU
Inductor, Shielded E Core, Ferrite,
800nH, 45A, 0.0009 ohm, SMD
SER2010-801MLB
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6
Item
36
Designator
P1, P3, P5, P6
P2
Description
Part Number
PCB Pin
3104-2-00-34-00-00-08-0
5015
37
Test Point, SMT, Miniature
PCB Pin
38
P4, P7
3231-2-00-34-00-00-08-0
FCX690BTA
39
Q1, Q3
NPN, 2A, 45V
PNP, 0.2A, 40V
40
Q2
CMPT3906
41
Q4, Q5, Q10, Q11
Q6, Q7, Q8, Q9
4.5A, 36nC, rDS(on) @ 4.5V =0.004 ohm SI7336ADP-GE3
42
MOSFET, N-CH, 100V, 9.3A, PQFN 8L IRFH5053TRPBF
5x6 A
43
44
45
Q12, Q13
R1
0.31A, 0.7nC, rDS(on) @ 4.5V =2.5 Ohm NTZD5110NT1G
RES 10 Ohm 1%, 0.125W, 0805
CRCW080510R0FKEA
CRCW040210k0FKED
R2, R28, R33, R34, R35, RES 10K Ohm 1%, 0.063W, 0402
R36
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
R3, R4
R5
RES 5.1K Ohm 5%, 0.125W, 0805
RES 1K Ohm, 5.1, 0.125W, 0805
RES 100K Ohm,1%, 0.125W, 0805
RES, 2.61k ohm, 1%, 0.063W, 0402
RES 20 OHM 1/8W 5% 0805 SMD
RES, 1.58k ohm, 1%, 0.063W, 0402
RES, 0 ohm, 5%, 0.063W, 0402
RES 4.99 Ohm,1%, 0.25W, 1206
RES, 1.69k ohm, 1%, 0.063W, 0402
RES 24K, 5%, 0.063W, 0402
ERJ-6GEYJ512V
CRCW08051K00FKEA
CRCW0805100KFKEA
CRCW04022K61FKED
ERJ-6GEYJ200V
R6
R7
R8
R9
CRCW04021K58FKED
RC0402JR-070RL
R10, R12
R11, R17
R13
CRCW12064R99FNEA
CRCW04021K69FKED
CRCW040224k0JNED
CRCW040230K1FKED
CRCW040220k0FKED
CRCW040215R0FKED
CRCW040210R0FKED
CRCW04021K00JNED
CRCW040225k5FKED
CRCW0402499RFKED
CRCW04025k11FKED
NU
R14
R15
RES, 30.1k ohm, 1%, 0.063W, 0402
RES 20k Ohm,1%, 0.063W, 0402
RES, 15.0 ohm, 1%, 0.063W, 0402
RES 10.0 ohm, 1%, 0.063W, 0402
RES 1.0K OHM 1/16W 5% 0402 SMD
RES 25.5k ohm,1%, 0.063W, 0402
RES 499 ohm, 1%, 0.063W, 0402
RES 5.11k ohm, 1%, 0.063W, 0402
NU
R16
R18
R19, R31
R21
R22
R23
R24
R25, R26
R27
RES 47 OHM .25W 5% 0603 SMD
RES 100 ohm, 1%, 0.063W, 0402
RES 15k ohm,1%, 0.063W, 0402
RES 1.82k ohm,1%, 0.063W, 0402
RES 0.0 ohm, 5%, 0.063W, 0402
RES 0.0 ohm, 5%, 0.063W, 1206
High Frequency Planar Transformer
SMT Current Sense Transformer
Full-Bridge PWM Controller
CRCW060347R0JNEAHP
CRCW0402100RFKED
CRCW040215k0FKED
CRCW04021k82FKED
CRCW04020000Z0ED
CRCW12060000Z0EA
PA0876.003NL
R32
R29
R30
R37
D1
T1
T2
PA1005.100NL
U1
LM5045MH
U2
Dual 5A Compound Gate Driver with
Negative Output Voltage Capability
LM5110-1SD
75
76
77
78
U3
U4
U5
U6
Low Input Current, High CTR Photo-
coupler
PS2811-1-M-A
RRIO, High Output Current & Unlimited LM8261M5
Cap Load Op Amp in SOT23-5
Precision Micro-power Shunt Voltage
Reference
LM4041BIM3-1.2
ISO-Pro Low-Power Dual-Channel Digital Si8420BB-D-IS
Isolator
7
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PCB Layouts
30146211
Top Side Assembly
30146212
Bottom Side Assembly
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8
30146213
Layer 1 (Top Side)
30146214
Layer 2
9
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30146215
Layer 3
30146216
Layer 4
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10
30146217
Layer 5
30146218
Layer 6 (Bottom Side)
11
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