EFS Datasheet, PDF (10/14 Pages) STMicroelectronics – STARLIGHT-KIT

EFS
6/ PREHEAT PHASE DURATION 50-60Hz:
The driver determines the preheat duration by counting mains cycles. This numeric solution brings
naturally a good precision depending only on the mains frequency tolerance.
With the 2 driver versions, the EFS startlight-kit provides a choice of 4 preheat duration’s. The following
table gives the preheat duration before the first ignition attempt. The seven next preheat duration’s, in case
of unsuccessful ignition attempt, last the half of the first one
MAINS FREQUENCY
DRIVER VERSION
Pin 2 connection
PREHEAT DURATION
50Hz
EFS2A
EFS2B
GND
VCC
GND
VCC
1.5s
2.56s
0.74s
1.24s
60Hz
EFS2B
GND
VCC
0.62s
1.03s
7/ TUBE STATE DETECTION:
During the ignition sequence or once the lamp is lit, the starter checks the state of the lamp (lit or off).
To determine this state, the driver reads the lamp voltage through the resistor bridge (R1+R2+R3, R4).
- If the lamp is off, its voltage equal the mains voltage.
- If the lamp is lit, its voltage is only 80 V (for a 58W lamp).
Thus the lamp state is determined by comparison of the lamp voltage with a programmed detection level.
Tolerance effects:
Tolerances on resistors (R1, R2, R3 and R4) as
well as on the integrated comparator bring a
tolerance on the set detection level. Thus the
detection level is included in a range delimited by
the maximum and the minimum detection levels
(DL_MAX DL_min).
The driver checks the state of the lamp when
mains voltage is maximum, that is to say 5 ms after
the zero crossing mains voltage (50Hz). Here
again internal tolerances bring a tolerance on the
real checking moment (TC_min TC_MAX).
CORRECT SETTING = NO WAVEFORM
ACROSS THE GREY AREA
DL
MAX
DL
min
OFF Lamp
Voltage
LIT Lamp
Voltage
TC _min
TC _MAX
How to set the detection level?
Only the R4 resistor value can be set to adjust the detection level. Values of resitors R1 to R3 must match
values of the table RECOMMENDED COMPONENTS ACCORDING TO APPLICATION CONDITIONS of
the page 5. Practically the R4 resistor value has to be set so that neither the OFF lamp voltage nor the LIT
lamp voltage cross the grey area.
The DL_MAX and DL_min limits can be calculated as follows:
DL_MAX
=
1.265
x
(R4 min
+
R1MAX +
R4 min
R 2 MAX
+
R 3 MAX )
and
DL_min
= ^{1.122 x (R4 MAX + R1min+ R 2 min+ R 3 min)}
R4 MAX
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