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參數(shù)資料
| 型號： | ML4800CS |
| 廠商： | FAIRCHILD SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | Power Factor Correction and PWM Controller Combo |
| 中文描述： | 1 A POWER FACTOR CONTROLLER WITH POST REGULATOR, 250 kHz SWITCHING FREQ-MAX, PDSO16 |
| 封裝： | PLASTIC, SOIC-16 |
| 文件頁數(shù)： | 11/14頁 |
| 文件大小： | 154K |
| 代理商： | ML4800CS |
ML4800
REV. 1.0.2 3/7/2001
11
FUNCTIONAL DESCRIPTION
(Continued)
(6)
where C
SS
is the required soft start capacitance, and
t
DELAY
is the desired start-up delay.
It is important that the time constant of the PWM soft-start
allow the PFC time to generate sufficient output power for
the PWM section. The PWM start-up delay should be at
least 5ms.
Solving for the minimum value of C
SS
:
25
125
.
(6a)
Caution should be exercised when using this minimum
soft start capacitance value because premature charging of
the SS capacitor and activation of the PWM section can
result if V
FB
is in the hysteresis band of the V
IN
OK
comparator at start-up. The magnitude of V
FB
at start-up is
related both to line voltage and nominal PFC output
voltage. Typically, a 1.0
μ
F soft start capacitor will allow
time for V
FB
and PFC out to reach their nominal values
prior to activation of the PWM section at line voltages
between 90Vrms and 265Vrms.
Generating V
CC
The ML4800 is a voltage-fed part. It requires an external
15V,
±
10% (or better) shunt voltage regulator, or some
other V
CC
regulator, to regulate the voltage supplied to the
part at 15V nominal. This allows low power dissipation
while at the same time delivering 13V nominal gate drive
at the PWM OUT and PFC OUT outputs. If using a Zener
diode for this function, it is important to limit the current
through the Zener to avoid overheating or destroying it.
This can be easily done with a single resistor in series with
the Vcc pin, returned to a bias supply of typically 18V to
20V. The resistor
’
s value must be chosen to meet the
operating current requirement of the ML4800 itself
(8.5mA, max.) plus the current required by the two gate
driver outputs.
EXAMPLE:
With a V
BIAS
of 20V, a V
CC
of 15V and the ML4800 driving
a total gate charge of 90nC at 100kHz (e.g., 1 IRF840
MOSFET and 2 IRF820 MOSFETs), the gate driver current
required is:
I
kHz
nC
×
100
90
(7)
(8)
Choose R
BIAS
= 240
.
The ML4800 should be locally bypassed with a 1.0
μ
F
ceramic capacitor. In most applications, an electrolytic
capacitor of between 47
μ
F and 220
μ
F is also required
across the part, both for filtering and as part of the start-up
bootstrap circuitry.
RAMP
VEAO
TIME
VSW1
TIME
REF
EA
–
+
–
+
OSC
DFF
R
D
Q
Q
CLK
U1
RAMP
CLK
U4
U3
C1
RL
I4
SW2
SW1
+
DC
I1
I2
I3
VIN
L1
U2
Figure 4. Typical Trailing Edge Control Scheme
C
t
A
V
SS
DELAY
=
×
25
125
.
μ
C
ms
5
A
V
nF
SS
=
×
=
100
μ
mA
9
GATEDRIVE
=
=
R
V
I
CC
V
+
I
I
BIAS
BIAS
CC
G
z
=
+
R
V
9
V
+
mA
6
mA
mA
5
BIAS
=
+
=
20
15
250
相關(guān)PDF資料 |
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| ML4800 | Power Factor Correction and PWM Controller Combo(功率因數(shù)校正器和PWM控制器組合芯片) |
| ML4801CP | Variable Feedforward PFC/PWM Controller Combo |
| ML4801CS | Variable Feedforward PFC/PWM Controller Combo |
| ML4801IP | Variable Feedforward PFC/PWM Controller Combo |
| ML4801IS | Variable Feedforward PFC/PWM Controller Combo |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ML4800CS_Q | 功能描述:功率因數(shù)校正 IC PFC Controller PWM Combo 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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| ML4800CSX | 功能描述:功率因數(shù)校正 IC PFC Controller PWM Combo 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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| ML4800CSX_NL | 功能描述:功率因數(shù)校正 IC Power Factor PWM Contrl 0.2mA 81KHz 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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| ML4800IP | 功能描述:功率因數(shù)校正 IC PFC Controller PWM Combo 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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
| ML4800IS | 功能描述:功率因數(shù)校正 IC PFC Controller PWM Combo 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 安裝風格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel |
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