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參數(shù)資料
| 型號(hào)： | AND8099 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | 5.0 V, 2.0 A Flyback Converter |
| 中文描述： | 5.0五，2.0反激式轉(zhuǎn)換器 |
| 文件頁(yè)數(shù)： | 3/8頁(yè) |
| 文件大?。?/td> | 219K |
| 代理商： | AND8099 |
AND8099/D
http://onsemi.com
3
In order for the regulator to operate in discontinuous mode
under worse case conditions and to maximize power, the
maximum on time is 48% of the full period, therefore the the
maximum primary inductance is calculated based on a
maximum duty cycle of 48%. Using a larger inductance than
calculated will cause the power supply output to fall out of
regulation.
Vin(low)·
max
Ipeak· fop
duty cycle
Lpri
,
where
maxis the maximum
Lpri
80.2 · 0.48
0.667 * 100 · 103
0.577 mH
Primary flyback voltage:
VFB
Vin(low)· ton
toff
74.03 V, where
tonis 4.8 s
80.2 · 4.8 · 10- 6
5.2 · 10- 6
Primary to secondary turns ratio:
Npri
Nsec
Vout
By rearranging the above equation and solving for N
sec
yields
≈
1 turn.
Energy entering the core during on-time (when the power
switch is conducting):
Lpri· Ipeak2
2
measured in Joules.
VFB
VF
74.03
0.525
5
13.4
13 turns
Estored
,
where the stored energy is
Estored
0.577 · 10- 3· 0.6672
2
1.28
10- 4Joules
One can double check if the power capability of the
transformer is large enough to supply enough power to the
output with the following equation:
Lpri· Ipeak2
2
10- 4· 100 kHz
Pin(core)
· fop
Pout
Pin(core)
1.28
12.8 W
Pout
10 W
Input Snubber
Because of the high dv/dt characteristic of the power
transistor drain voltage and of the transformer leakage
inductance, voltage spikes and ringing occur at the drain
when the power switch is turned off. Resistor R1, C3, D5
compromise an RCD snubber. In parallel to the primary
winding are R2 and C4 which compromise an RC ringing
damper which slows down the dv/dt and reduces the
peak voltage therefore decreasing the ringing due
to high frequency noise. Since
i
capacitance will also reduce the magnitude of the voltage
ripple. The snubber and ringing damper act together to
protect the IC from voltage transients greater than 700 V and
reduce radiated noise.
C ·dt
, increasing the
Output Block
The output consists of a diode rectifier, a pi-filter, and a
voltage regulator. For a flyback converter with an output
voltage less than 7.5 V, a Schottky rectifier provides the
maximum efficiency and is therefore the best choice. The
Schottky rectifier used is the ON Semiconductor 1N5822, in
which V
R
= 40 V, I
F
= 3.0 A, and V
F
= 0.525 V. The main
purpose of this rectifier is to take the secondary voltage and
convert it to a DC voltage. The following equations are used
in selecting the Schottky rectifier:
Maximum reverse peak voltage (calculated at high line):
VRout
Vout
Vpeak(max)·Npri
VRout
5
375 ·13
33.85 V
For discontinuous mode, the maximum forward peak
current can be approximated using:
IFout
4 · Iout
Diode D6 along with C7, C8, C9, L2, and C11 rectify the
transformer secondary and filter the output in order to
provide a tightly regulated DC output . Capacitor C7, C8 and
C9 are placed in parallel in order to reduce ESR. In addition,
the voltage rating of C7, C8 and C9 should be high enough
for them to withstand the voltage spikes and the output
voltage. L2 and C11 form a low pass filter that attenuates
high frequency noise.
Output filter capacitor:
Iout(max)· Toff(max)
Vripple(desired)
1
fop
and Vripple(desired)
1
100 · 10
3
0.040
Output filter choke (designed for a break frequency of
4.0 kHz):
2
,
where C
is the corner frequency.
8 A
Cout
,
min·
where Toff(max)
40 mV
Cout
8 · 0.52 ·
1040 F
L
1
· f ·
2 ·
C
C11
330 F and f
L
1
2 ·
· 4k ·
330 F
2
4.8 H
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AND8099/D | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:5.0 V, 2.0 A Flyback Converter |
| AND8104/D | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:MicroIntegration Technology Solutions for Protection in High Speed I/O Data Lines |
| AND8109 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:LED CONSTANT CURRENT SOURCE SCHEME |
| AND8112 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:A Quasi-Resonant SPICE Model Eases Feedback Loop Designs |
| AND8116 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications |
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