DI-51 [POWERINT]
5 W Flyback DC-DC Converter; 5 W反激式DC -DC转换器
| 型号： | DI-51 |
| 厂家： | 
Power Integrations |
| 描述： | 5 W Flyback DC-DC Converter |
| 文件： | 总2页 (文件大小：54K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
®
Design Idea DI-51
DPA-Switch™
5 W Flyback DC-DC Converter
Topology
Flyback
Device
Power Output
Input Voltage
Output Voltage
Application
DC-DC Converter
5 W
36-75 VDC
DPA423R
5 V
Design Highlights
Resistor R3 programs the internal current limit of the
DPA423Rto53%ofnominal.Thislimitstheoverloadpower
that can be delivered in a fault condition.
• Small footprint: 35 mm x 20 mm (1.4 in. x 0.8 in.)
• High efficiency flyback (>80% min.)
• 8.8 W per cu. in.
Zener VR1 clamps the leakage inductance spikes to keep the
DRAIN voltage at a safe level. The bias supply for U1 is
provided from the auxiliary flyback transformer winding
(pins 2 and 4), rectified and filtered by diode D1 and
capacitor C23.
• Low component count
• Accurate line OV and UV protection
• Thermal, short circuit and output overload protection
• No current sense components
A snubber for diode D2 (capacitor and resistor) can be used,
but was not needed in this application. Inductor L2 and
capacitor C12 form a post filter to reduce high frequency
output switching ripple. A soft-finish network, C18, D3 and
R7, eliminates output turn-on overshoot. The remaining
components provide output voltage regulation and loop
compensation.
Operation
DPA-Switchgreatlysimplifiesthedesigncomparedtoadiscrete
implementation. Resistor R1 sets the input under/over voltages
to 33 V and 86 V, respectively. Including tolerances, these
thresholds guarantee the converter is operational between 36 V
and 75 V without the cost of additional line sense components.
C7 1 nF
R14
1.5 kV
10 Ω
L2
300 nH
6 A
L1
C12
100 µF
10 V
C10
C11
+ V
36-75 VDC
D2 SL23
1A/30 V
10 µH
IN
100 µF 100 µF
0.85 A
5 V, 1 A
RTN
10 V 10 V
T1
7,8
1
5,6
FL
D1 BAV19WS
2
3
C23
4.7 µF
20 V
4
R1
619 kΩ
1%
R10
18 kΩ
1%
U2
R7
10 kΩ
U2
C1
0.22 µF
100 V
C2
1 µF
100 V
DPA-Switch
C16
220 nF
U1
D3
BAV19WS
DPA423R
R6
R12
D
S
L
150 Ω
5.1 Ω
CONTROL
C
C17
1 µF
R9
220 Ω
C18
10 µF
10 V
R4
X
F
R3
1.0 Ω
VR1
14.4 kΩ
C5
47 nF
SMBJ
150 A
1%
U3
LM431AIM3
C6
68 µF
10 V
R11
18 kΩ
1%
-V
IN
PI-3547-062403
Figure 1. DPA-Switch Flyback DC-DC Converter.
.
July 2003
DI-51
www.powerint.com
DI-51
Key Design Points
TRANSFORMER PARAMETERS
• For the nominal under-voltage set point VUV:
R1 = (VUV – 2.35) / 50 µA
EFD-10
Core Material
Ferroxcube 3F3
AL of 100 nH/T2
VOV = (R1 x 135 µA) + 2.5 V
EDF-10 8 pin
(or equivalent)
Bobbin
• For highest efficiency designs: use continuous conduction
mode operation designed at approximately 0.4 KRP;
minimize turns in the transformer while keeping AC flux
density(BM)<3000Gauss;fullyfillasinglelayerforeach
winding to minimize leakage inductance and maximize
copperfillfactor;useaSchottkyrectifyingdiode(D2)with
a low forward drop (in this case, the SL23 diode has a
Vf = 0.320 V at 125 °C/2A).
• Resistor R3: the PIXls spreadsheet calculates the peak
current (IP) of the power supply. Resistor R3 is chosen to
settheinternalcurrentlimit10%to15%abovethecalculated
IP value. This limits overload power (worst case is at high
input line).
1/2 Primary (1-FL), Tape, Bias
(4-3), 5 V (5-8),
Tape, 1/2 Primary (FL-2), Tape
Winding Order
(pin numbers)
Primary Inductance
174 µH ± 10%
4.7 MHz (minimum)
1.0 µH (minimum)
Primary Resonant
Frequency
Leakage Inductance
Table 1. Transformer Construction Information.
• Set resonant frequency of post-filter (L2, C12) beyond
crossover frequency (typically 5% to 10% of switching
frequency).
85
84
83
82
81
• For main secondary current loop from transformer pin 8 to
diode D2 and capacitors C10, C11 and back to pin 6 of the
transformer: ensure identical path length for C10 and C11
to guarantee they equally share the ripple current.
• Due to the very tight size constraints on this power supply,
the drain voltage traces should be kept as short as possible
and where possible, shielded by surrounding them with
source potential traces. This will prevent noise coupling to
the low-voltage signal pins of the DPA-Switch.
80
79
36 VDC
48 VDC
72 VDC
78
77
76
75
1
2
3
4
5
Pout (W)
Figure 2. Efficiency vs. Output Power.
For the latest updates, visit our Web site: www.powerint.com
Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.
Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any license
under its patent rights or the rights of others. The products and applications illustrated herein (including circuits external to the products and
transformer construction) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign patent
applications assigned to Power Integrations. A complete list of Power Integrations’ patents may be found at www.powerint.com.
The PI Logo, TOPSwitch, TinySwitch, LinkSwitch and EcoSmart are registered trademarks of Power Integrations, Inc.
PI Expert and DPA-Switch are trademarks of Power Integrations, Inc. ©Copyright 2003, Power Integrations, Inc.
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