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參數(shù)資料
| 型號： | ML4863 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | High Efficiency Flyback Controller(高效回轉(zhuǎn)電源控制器) |
| 中文描述： | 高效率反激式控制器（高效回轉(zhuǎn)電源控制器） |
| 文件頁數(shù)： | 6/10頁 |
| 文件大?。?/td> | 118K |
| 代理商： | ML4863 |
ML4863
6
REV. 1.0 10/12/2000
SYNCHRONOUS RECTIFIER CONTROL
The control circuitry for the synchronous rectifier does not
influence the operation of the main controller. The
synchronous rectifier is turned on during the minimum off
time, or whenever the SENSE pin is less than –18mV.
During transitions where the primary switch is turned on
before the voltage on the SENSE pin goes above –18mV,
the gate of the synchronous rectifier is discharged softly to
avoid accidently triggering the current-mode comparator
with the gate discharge spike on the sense resistor.
The part will also operate with a Schottky diode in place
of the synchronous rectifier, but the conversion efficiency
will suffer.
CURRENT LIMIT AND MODES OF OPERATION
The normal operating range and current limit point are
determined by the current programming comparator. They
are dependent on the value of the synchronous rectifier
current sense resistor (R
SENSE
), the nominal transformer
primary inductance (L
P
), and the input voltage.
R
SENSE
can be calculated by:
R
V
V
V
mV
I
V
V
I
SENSE
IN MIN
a
OUT
IN
OUT MAX
IN MIN
a
IN MAX
OUT MAX
=
+
×
+
×
×
F
H
I
K
×
f
f
f
f
f
150
20
η
(1)
FUNCTIONAL DESCRIPTION
(Continued)
where
η
= converter efficiency.
Once R
SENSE
has been determined, L
P
can be found:
L
V
R
P
IN MAX
a
SENSE
=
×
×
(
)
25 10
6
f
(2)
Three operational modes are defined by the voltage at the
SENSE pin at the end of the off-time: discontinuous mode,
continuous mode, and current limit. The following values
can be used to determine the current levels of each mode:
V
SENSE
< 0V: discontinuous mode
0V < V
SENSE
< 160mV: continuous mode
160mV < V
SENSE
< 235mV: current limit
Inserting the maximum value of V
SENSE
for each
operational mode into the following equation will
determine the maximum current levels for each
operational mode:
F
I
V
V
V
V
R
t
V
L
OUT
IN
+
OUT
IN
SENSE
SENSE
ON
2
IN
P
=
×
+
×
×
I
×
η
(3)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ML4863CS | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4863CS / ES WAF UP | 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4863CSX | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Fairchild Semiconductor Corporation 功能描述: |
| ML4863ES | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:High Efficiency Flyback Controller |
| ML4863IS | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:High Efficiency Flyback Controller |
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