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參數(shù)資料
| 型號： | ML4835 |
| 廠商： | Fairchild Semiconductor Corporation |
| 英文描述： | Compact Fluorescent Electronic Dimming Ballast Controller(小型熒光管整流器控制器) |
| 中文描述： | 緊湊型熒光燈電子調光鎮(zhèn)流器控制器（小型熒光管整流器控制器） |
| 文件頁數(shù)： | 11/17頁 |
| 文件大?。?/td> | 214K |
| 代理商： | ML4835 |
ML4835
REV. 1.0 10/12/2000
11
Highest lamp power, and lowest output frequency are
attained when voltage at LFB OUT is at its maximum
output voltage (V
OH
).
In this condition, the minimum operating frequency of the
ballast is set per equation 5 above.
For the IC to be used effectively in dimming ballasts with
higher Q output networks a larger C
T
value and lower R
T
value can be used, to yield a smaller frequency excursion
over the control range (voltage at LFB OUT). The
discharge current is set to 5.5mA.
Assuming that I
DIS
>>I
RT
:
t
C
DIS VCO
(
T
)
×
600
(9)
IC BIAS, UNDER-VOLTAGE LOCKOUT AND
THERMAL SHUTDOWN
The IC includes a shunt clamp which will limit the
voltage at V
CC
to 15V (V
CCZ
). The IC should be fed with
a current limited source, typically derived from the
ballast transformer auxiliary winding. When V
CC
is below
V
CCZ
– 1.1V, the IC draws less than 0.55mA of quiescent
current and the outputs are off. This allows the IC to start
using a “bleed resistor” from the rectified AC line.
To help reduce ballast cost, the ML4835 includes a
temperature sensor which will inhibit ballast operation if
the IC’s junction temperature exceeds 130°C. In order to
use this sensor in lieu of an external sensor, care should
be taken when placing the IC to ensure that it is sensing
temperature at the physically appropriate point in the
ballast. The ML4835’s die temperature can be estimated
with the following equation:
T
T
P
(
C W
/
J
A
D
+
+
°
)
65
(10)
STARTING, RE-START, PREHEAT AND INTERRUPT
The lamp starting scenario implemented in the ML4835
is designed to maximize lamp life and minimize ballast
heating during lamp out conditions.
The circuit in Figure 10 controls the lamp starting
scenarios: Filament preheat and lamp out interrupt. C
X
is
charged with a current of I
R(SET)
/4 and discharged through
R
X
. The voltage at C
X
is initialized to 0.7V (V
BE
) at power
up. The time for C
X
to rise to 4.75V is the filament preheat
time. During that time, the oscillator charging current
(I
CHG
) is 2.5/R
SET
. This will produce a high frequency for
filament preheat, but will not produce sufficient voltage
to ignite the lamp or cause significant glow current.
After cathode heating, the inverter frequency drops to
F
START
causing a high voltage to appear to ignite the
lamp. If lamp current is not detected when the lamp is
supposed to have ignited, the C
X
charging current is shut
off and the inverter is inhibited until C
X
is discharged by
R
X
to the 1.25V threshold. Shutting off the inverter in this
manner prevents the inverter from generating excessive
heat when the lamp fails to strike or is out of socket.
Typically this time is set to be fairly long by choosing a
large value of R
X
.
LFB OUT is ignored by the oscillator until INTERRUPT is
above 1.25V The C
X
pin is clamped to about 7.5V.
Care should also be taken not to turn on the VCCZ clamp
so as not to dissipate excessive power in the IC. This will
cause the temp sensor to become active at a lower
ambient temperature.
A summary of the operating frequencies in the various
operating modes is shown below.
OPERATING MODE
OPERATING FREQUENCY
[F(MAX) to F(MIN)]
2
Preheat
After
Preheat
Dimming
Control
F(START)
F(MIN) to F(MAX)
Figure 10. Lamp Preheat and Interrupt Timers
FUNCTIONAL DESCRIPTION
(Continued)
R
X
C
X
HEAT
INHIBIT
0.625
R
SET
LEA_ENB OR
DIMMING LOCKOUT
INTERRUPT
10
R
X
/C
X
S
R
Q
1.25/4.75
+
–
1.0/1.25
+
–
1.25/6.75
+
–
9
相關PDF資料 |
PDF描述 |
|---|---|
| ML4836 | Compact Fluorescent Electronic Dimming Ballast Controller(小型熒光管整流器控制器) |
| ML4841 | Variable Feedforward PFC/PWM Controller Combo(前饋可變PFC/PWM控制器組合芯片) |
| ML4851 | Low Current, Voltage Boost Regulator(小電流升壓穩(wěn)壓器) |
| ML4854IT | Adjustable, Low-Current, 2-Cell Boost Regulator with Shutdown and Low Battery Detect |
| ML4854 | Adjustable, Low-Current, 2-Cell Boost Regulator with Shutdown and Low Battery Detect |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| ML4835CP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Compact Fluorescent Electronic Dimming Ballast Controller |
| ML4835CS | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Compact Fluorescent Electronic Dimming Ballast Controller |
| ML4836 | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Compact Fluorescent Electronic Dimming Ballast Controller |
| ML4836CP | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Compact Fluorescent Electronic Dimming Ballast Controller |
| ML4836CS | 制造商:MICRO-LINEAR 制造商全稱:MICRO-LINEAR 功能描述:Compact Fluorescent Electronic Dimming Ballast Controller |
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