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參數(shù)資料
| 型號： | ML4821CS |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Power Factor Controller |
| 中文描述： | 1 A POWER FACTOR CONTROLLER, 115 kHz SWITCHING FREQ-MAX, PDSO20 |
| 封裝： | SOIC-20 |
| 文件頁數(shù)： | 6/12頁 |
| 文件大?。?/td> | 106K |
| 代理商： | ML4821CS |
ML4821
PRODUCT SPECIFICATION
6
REV. 1.0.2 6/19/01
Functional Description
Oscillator
The ML4821 oscillator charges the external capacitor
connected to C
T
with a current equal to 2.5/R
T
. When the
capacitor voltage reaches the upper threshold, the compara-
tor changes state and the capacitor discharges to the lower
threshold through Q1.
The oscillator period can be described by the following
relationship:
T
OSC
= T
RAMP
+ T
DISCHARGE
where:
T
RAMP
= C(Ramp Valley to Peak)
÷
(I
RT
/2)
and:
T
DISCHARGE
= C(Ramp Valley to Pk)
÷
(8.4mA
–
I
RT
/2)
The ML4821 oscillator includes a SYNC input for synchro-
nizing to an external frequency source. A positive pulse on
this pin of 2V (typ) resets the oscillators comparator and
initiates a discharge cycle for C
T
. The R
T
and C
T
component
values which set the ML4821 oscillator frequency should be
selected to produce a lower frequency than the external
frequency source.
VOLTAGE and Current ERROR Amplifiers
The ML4821 voltage error amplifier is a high open loop
gain, wide bandwidth amplifier with a class A output. The
soft start circuit controls the input to this amplifier for closed
loop soft start operation.
The current error amplifier (IA) is similar to the voltage error
amplifier but is designed for very low offsets to allow the
selection of a low value resistor for R
SENSE
.
Output Driver Stage
The ML4821 Output Driver is a 1A peak output high speed
totem pole circuit designed to quickly drive capacitive loads,
such as power MOSFET gates. The driver circuit’s output
voltage is internally limited to 17V.
Gain Modulator
The ML4821 gain modulator responds linearly to current
injected into the I
SINE
pin, and in an inverse-square fashion
to voltage on the V
RMS
pin. At very low voltages on the V
RMS
pin, the gain modulator enforces a power limit, or ”brown-
out protection”, upon the overall PFC circuit (Figures 6 and
7). The rectified line input sine wave is converted to a current
for the I
SINE
input via a dropping resistor. In this way, most
ground noise produces an insignificant effect on the refer-
ence to the PWM comparator. This gives the ML4821 a high
degree of immunity to the disturbances common in high-
power switching circuits.
CLOCK
t
D
C
T
RAMP PEAK
RAMP VALLEY
Figure 1. Oscillator Block Diagram
Figure 2. Oscillator Timing Resistance vs. Frequency
R
T
+
–
R
T
C
T
C
T
V
REF
8.4mA
Q1
Q2
1k
2k
SYNC
I
RT
2
I
RT
1000
100
10
0
10
20
1nF
30
40
50
R
T
(k
)
F
680pF
470pF
330pF
150pF
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ML4822 | ZVS Average Current PFC Controller(零電壓轉(zhuǎn)換和平均電流轉(zhuǎn)換的功率因數(shù)控制器) |
| ML4823 | High Frequency PWM Controller(高頻PWM控制器) |
| ML4823IQ | High Frequency Power Supply Controller |
| ML4823CP | High Frequency Power Supply Controller |
| ML4823CQ | High Frequency Power Supply Controller |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ML4821CS_Q | 功能描述:功率因數(shù)校正 IC PFC Controller RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| ML4821CSX | 功能描述:功率因數(shù)校正 IC PFC Controller RoHS:否 制造商:Fairchild Semiconductor 開關(guān)頻率:300 KHz 最大功率耗散: 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| ML4821IP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Power Factor Controller |
| ML4821IS | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Power Factor Controller |
| ML4822 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:ZVS Average Current PFC Controller |
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