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參數(shù)資料
| 型號： | MIC3832 |
| 廠商： | Micrel Semiconductor,Inc. |
| 英文描述： | Current-Fed PWM Controllers |
| 中文描述： | 電流型PWM控制器 |
| 文件頁數(shù)： | 10/10頁 |
| 文件大?。?/td> | 100K |
| 代理商： | MIC3832 |
MIC3832/3833
Micrel
4-144
April 1998
Magnetics Design
T1 : Magnetics Inc # 41303 – TC, P material, Primary = 26 turns 30 gauge wire, Secondary = 26 turns 30 gauge wire
T2: Seimen’s EFD25, N87 material. Primary = 20 turns 20 gauge wire, Secondary = 10 turns trifilar wound 20 gauge
wire. Both are center tapped.
L1: Seimen’s EFD20, N87 material. 13 turns 20 gauge wire. Gap for 20
μ
H
100kHz 100W Current-Fed Converter
Refer to Figure 5.
A 5V, 20A dc-to-dc converter uses the current-fed, push-pull
configuration for increased safety and reduced size and
transformer core area.
The input is an unregulated 14V to 32Vdc supply. An
MIC2951 low-dropout regulator supplies 12V to the MIC3833.
The main PWM switching element is an IRF540, with gate
drive provided by transformer T1. The two 50% duty cycle
outputs each drive an IRF540 directly, which in turn drive
respective sides of T2’s center tapped primary. The 1N6291A
transzorb is used to protect the MOSFETs from spikes.
Current-mode control simplifies the stability analysis, with the
0.2
, 5W resistor being used as the sensing element. As the
maximum duty cycle at light loads is greater than 50%, the
well characterized problem of subharmonic oscillations found
when using current-mode control was evident. A ramp,
introduced at the sensing element, provides slope compen-
sation. The 10k
and 470k
divider from the oscillator (ramp
source) to the sensing element provides the proper slope. A
large resistor value from C
T
to CMR makes buffering unnec-
essary.
Front-edge blanking eliminates the need for a filter network
around the sensing element and decreases the possibility of
turn-on transients that cause system instabilities.
Four inexpensive output capacitors in parallel reduce ESR to
an acceptable level of 80m
without adding too much size or
cost.
Error amplifier compensation uses a simple lead-lag network.
With current-mode control there is no need to compensate for
the LC filter pole.
Soft start is implemented to allow slow turn-on in the event of
a short circuit.
All magnetics were chosen to minimize losses at 100 kHz. T2
and L1 are wound using Siemen’s N87 material and T1 using
Magnetics Inc.’s P-type material. T2 and L1 use Siemen’s
EFD core and bobbin assemblies which are designed to
reduce the height/form factor of the finished supply. T1 is a
bifilar-wound toroid used as a 200kHz pulse transformer. T2
is not gapped, since a push-pull transformer has a minimum
dc current component, being a forward converter.
1 V OUT
2 SENSE
3 SHDN
4 GND
FB
7
V IN 8
5V TAP
6
ERROR 5
MIC2951
887k
1%
102k
1%
3.3μF
12V
100pF
3.3μF
1/2
MBR2535CT
2:1
1/2 MBR2535CT
1N6291A
IRF540
IRF540
20V
1N968
14—32V
20μH
IRF540
39k
39k
220μF
16V
220μF
16V
0.01μF
CER
0.1μF
MYLAR
MIC3833
1 GND
2 PWM
3 Q
4 V
5 5V REF
6 EA –
7 EA +
8 EA OUT
NC 9
SHDN 10
MDC/SS 11
C
T
R
14
Q 15
SYNC 13
CMR 12
5.1
k
5.1k
.01μF
200k
2.2nF
10k
2nF
0.2
5W
T2
0.1μF
10
0.1μF
T1
L1
10k
470k
MUR1605CT
1N6291A
1:1
+5V 20A
100
68k
68k
1μF
2000
μF
Figure 5: 100W Current-Fed, Push-Pull DC-to-DC Converter (Efficiency ~75%)
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MIC3832BN | Current-Fed PWM Controllers |
| MIC3832BWM | Current-Fed PWM Controllers |
| MIC3833BN | Current-Fed PWM Controllers |
| MIC3833BWM | Current-Fed PWM Controllers |
| MIC3839 | Flexible Push-Pull PWM Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MIC3832BN | 制造商:Micrel Inc 功能描述: |
| MIC3832BWM | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Current-Fed PWM Controllers |
| MIC3833BN | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Current-Fed PWM Controllers |
| MIC3833BWM | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Current-Fed PWM Controllers |
| MIC3838 | 制造商:MICREL 制造商全稱:Micrel Semiconductor 功能描述:Flexible Push-Pull PWM Controller |
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