Datenblatt-Suchmaschine für elektronische Bauteile
  German  ▼
ALLDATASHEETDE.COM

X  

ML4802CS Datenblatt(PDF) 11 Page - Micro Linear Corporation

Teilenummer ML4802CS
Bauteilbeschribung  PFC/PWM Controller Combo with Green Mode
Download  15 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Hersteller  MICRO-LINEAR [Micro Linear Corporation]
Direct Link  http://www.microlinear.com
Logo MICRO-LINEAR - Micro Linear Corporation

ML4802CS Datenblatt(HTML) 11 Page - Micro Linear Corporation

Back Button ML4802CS Datasheet HTML 7Page - Micro Linear Corporation ML4802CS Datasheet HTML 8Page - Micro Linear Corporation ML4802CS Datasheet HTML 9Page - Micro Linear Corporation ML4802CS Datasheet HTML 10Page - Micro Linear Corporation ML4802CS Datasheet HTML 11Page - Micro Linear Corporation ML4802CS Datasheet HTML 12Page - Micro Linear Corporation ML4802CS Datasheet HTML 13Page - Micro Linear Corporation ML4802CS Datasheet HTML 14Page - Micro Linear Corporation ML4802CS Datasheet HTML 15Page - Micro Linear Corporation  
Zoom Inzoom in Zoom Outzoom out
 11 / 15 page
background image
ML4802
11
August 2000
Datasheet
PWM SECTION
Pulse Width Modulator
The PWM section of the ML4802 is straightforward, but
there are several points which should be noted. Foremost
among these is its inherent synchronization to the PFC
section of the device, from which it also derives its basic
timing (at twice the PFC frequency in the ML4802). The
PWM is primarily intended for current-mode operation. In
current-mode applications, the PWM ramp (RAMP 2) is
usually derived directly from a current sensing resistor in
the primary of the output stage, and is thereby
representative of the current flowing in the converter’s
output stage. DC ILIMIT, which provides cycle-by-cycle
current limiting, is internally connected to RAMP 2.
No voltage error amplifier is included in the PWM stage
of the ML4802, as this function is generally performed on
the output side of the PWM’s isolation boundary. To
facilitate the design of optocoupler feedback circuitry, an
offset has been built into the PWM’s RAMP 2 input which
allows VDC to command a zero percent duty cycle for
input voltages below 1.25V.
VIN OK Comparator
The VIN OK comparator monitors the DC output of the
PFC and inhibits the PWM if this voltage on VFB is less
than its nominal 2.5V. Once this voltage reaches 2.5V,
which corresponds to the PFC output capacitor being
charged to its rated boost voltage, the soft-start
commences.
PWM Control (RAMP 2)
RAMP 2 is the sampling point for a voltage representing
the current in the primary of the PWM’s output
transformer, derived from a current sensing resistor.
PWM Current Limit
The DC ILIMIT pin is a cycle-by-cycle current limiter for
the PWM section. It is connected internally to the PWM
control pin. Should the input voltage at this pin ever
exceed 1.5V, the output of the PWM will be disabled until
the output flip-flop is reset by the clock pulse at the start
of the next PWM power cycle.
Soft Start
Start-up of the PWM is controlled by the selection of the
external capacitor at SS. A current source of 25µA
supplies the charging current for the capacitor, and start-
up of the PWM begins at 1.25V. Start-up delay can be
programmed by the following equation:
where CSS is the required soft start capacitance, and
tDELAY is the desired start-up delay.
FUNCTIONAL DESCRIPTION (Continued)
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 CSS:
Generating VCC
The ML4802 is a voltage-fed part. It requires an external
15V±10% (or better) Zener shunt voltage regulator, or
other controlled supply, to maintain the voltage supplied
to the part at 15V nominal. This allows a low power
dissipation while at the same time delivering 13V
nominal of gate drive at the PWM OUT and PFC OUT
outputs.
LEADING/TRAILING MODULATION
Conventional Pulse Width Modulation (PWM) techniques
employ trailing edge modulation in which the switch will
turn on right after the trailing edge of the system clock.
The error amplifier output voltage is then compared with
the modulating ramp. When the modulating ramp reaches
the level of the error amplifier output voltage, the switch
will be turned OFF. When the switch is ON, the inductor
current will ramp up. The effective duty cycle of the
trailing edge modulation is determined during the ON of
the switch. Figure 5 shows a typical trailing edge control
scheme.
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 5. Typical Trailing Edge Control Scheme
CSS
tDELAY
25 A
1.25V
m
CSS 5ms
25 A
1.25V
nF
@
m
200


Ähnliche Teilenummer - ML4802CS

HerstellerTeilenummerDatenblattBauteilbeschribung
logo
Fairchild Semiconductor
ML4802CS FAIRCHILD-ML4802CS Datasheet
285Kb / 15P
   PFC/PWM Controller Combo with Green Mode
More results

Ähnliche Beschreibung - ML4802CS

HerstellerTeilenummerDatenblattBauteilbeschribung
logo
Fairchild Semiconductor
ML4802 FAIRCHILD-ML4802 Datasheet
285Kb / 15P
   PFC/PWM Controller Combo with Green Mode
logo
Champion Microelectroni...
CM6805BO CHAMP-CM6805BO Datasheet
255Kb / 15P
   10-PIN Green-Mode PFC/PWM Combo CONTROLLER
CM6805A CHAMP-CM6805A_10 Datasheet
203Kb / 15P
   10-PIN Green-Mode PFC/PWM Combo CONTROLLER
CM6805BO CHAMP-CM6805BO_10 Datasheet
203Kb / 15P
   10-PIN Green-Mode PFC/PWM Combo CONTROLLER
CM6805A CHAMP-CM6805A Datasheet
256Kb / 15P
   10-PIN Green-Mode PFC/PWM Combo CONTROLLER
logo
Fairchild Semiconductor
SG6902 FAIRCHILD-SG6902 Datasheet
856Kb / 22P
   Green-Mode PFC / Flyback-PWM Controller
logo
Champion Microelectroni...
CM6802 CHAMP-CM6802 Datasheet
338Kb / 18P
   NO BLEED RESISTOR GREEN MODE PFC/PWM CONTROLLER COMBO
logo
Fairchild Semiconductor
SG6932 FAIRCHILD-SG6932 Datasheet
696Kb / 20P
   Green-Mode PFC / Forward PWM Controller
SG6905 FAIRCHILD-SG6905 Datasheet
689Kb / 21P
   Green mode PFC/Flyback-PWM Controller
ML4805 FAIRCHILD-ML4805 Datasheet
125Kb / 13P
   Variable Feedforward PFC/PWM Controller Combo
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


Datenblatt Download

Go To PDF Page


Link URL




Privatsphäre und Datenschutz
ALLDATASHEETDE.COM
War ALLDATASHEET hilfreich?  [ DONATE ] 

Über Alldatasheet   |   Werbung   |   Kontakt   |   Privatsphäre und Datenschutz   |   Linktausch   |   Hersteller
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com