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樓主 |
發表於 2009-8-24 11:24:05
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請大家了解以下英文有閞vsen,isen是否到知中斷電源問題
5. Aged CCFL Ignition
OZ9938 provides a striking timer function to
ensure that any aged, slow-turn-on CCFL is
provided with sufficient voltage and time to ignite.
The transformer output voltage is sensed at
VSEN
(Pin 6). When the voltage at VSEN reaches a
threshold of approximately 3.0V, the IC regulates
the output voltage at the transformer secondary.
If the lamps are not ignited when the voltage at
TIMER (pin 3) reaches a threshold of
approximately 3V, the IC will shutdown and latch
The approximate striking time is calculated by the
following equation.
Tstr [Sec] = CTIMER [uF]
To resume normal operation, toggle the ENA
signal or reset VDDA.
6. Normal Operation
Once the lamps are ignited and the voltage at
ISEN (pin 5) is >0.7V, the IC enters the normal
operation mode and the PWM dimming control is
activated.
The operating frequency is determined by
resistor (R9) and capacitor (C9) connected to CT
(pin 13). The control loop regulates the average
current through the lamps by adjusting the duty
cycle of the output drives. Constant frequency
operation eliminates interference with the inverter
and LCD panel that often occurs in a variable
frequency inverter system. The peak and valley
of the CT waveform are 2V and 0V respectively.
The approximate operating frequency is
calculated by the following equation. |
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