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| AN880 Datasheet, PDF (3/14 Pages) STMicroelectronics – A NEW HIGH VOLTAGE IC DRIVER FOR ELECTRONIC LAMP BALLAST | |||
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Figure 5: Bootstrap capacitor charge.
AN880 APPLICATION NOTE
15.6 V
ON
600V
120â¦
CHARGE PUMP CIRCUIT
LOGIC
L6569
ON
Figure 6: Basic diagram for 2x105 W lamp ballast in full bridge configuration.
VS
EXTERNAL
OSCILLATOR
100nF
BOOT
VS
RF
HVG 47
L6569
CF
OUT
GND
LVG 47
D02IN1386
STB9NK50Z
HV
100nF
BOOT
VS
47 HVG
RF
L6569
OUT
CF
47 LVG
GND
Typical industrial TL ballasts requires complex
control with dimming or automation interface.
Here the L6569 is a driver between the power
and control blocks. To use it with an external os-
cillator, pin CF is used as an 0-12V logic input,
and the L6569 becomes a high voltage buffer.
Applications with power above 150W require a full
bridge inverter. Figure 6 shows how two L6569
drive such a MOSFET bridge. If no external con-
trol is required, the first L6569 master can control
the switching with its oscillator, and synchronizes
the other driver as (slave).
The L6569 start up
Two versions of the L6569 are available with dif-
ferent start up characteristics. The L6569 drives
the lower MOSFET ON at power-up until the sup-
ply voltage reaches the Under Voltage Lock Out.
The bootstrap capacitor is precharged to 4.6V
and both the lower and the upper MOSFETs will
switch immediately with the oscillator. This is in-
tended for inverters which use only one DC block-
ing capacitor connected to the power ground, as
shown on figure 4 for CFL ballast.
3/14
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