EFS Datasheet, PDF (9/14 Pages) STMicroelectronics – STARLIGHT-KIT

5/ THE DRIVER: FUNCTIONAL DESCRIPTION
EFS2A DRIVER Internal block diagram (50Hz operation)
EFS
State
tube
Shunt
Vcc
State tube detection
(Striked / Off)
Clock 1/8
0 current synchro
Pre-heat 1,5s
period or
counter 2.5s
ISO synchro
350mA
UVLO
8 attempts
Strikes counter
Current generator
30mA
Minimum
Power supply
Preheat
Select
G2
G1
GND
ALGORITHM
1. At switch on:
At switch on, an integrated Under Voltage Lock Out function (UVLO) resets the driver as long as the supply
voltage stays below a safety level.
2. Preheat:
AC MAINS ON
The ignition sequence begins with the preheat
phase. Two different duration’s can be selected with
PIN 2 (see table EFS STARLIGHT-KIT PARTS
SELECTION page 2).
During this phase, the driver maintains the ASD™ in
a full ON-state making the starter equivalent to a
bi-directional conducting switch.
UVLO RESET
Preheat *
1.5s or 2.5s
Strike
3. Ignition of the fluorescent tube:
Attempt = Attempt + 1
At the end of the preheat period, the starter strikes
the fluorescent lamp.
For that, the driver reads continuously the current
through the starter. When the current reaches the
Switch Off level (I_SO = 350mA), the driver turns off
the ASD™. This induces a high voltage pulse across
the lamp. This pulse amplitude is limited by the
ASD™ (′1350V).
Loop 2
Autosupply
Fail = 0
YES
Tube
Ignited?
NO
Fail = Fail + 1
Loop 1
NO
Fail = 8
Preheat *
0.75s or 1.25s
Loop 3
YES
Attempt <8
NO
4. If the lamp fails to strike:
Attempt = 0
YES
The driver detects the state of the tube (lit or off). If it
stays off during 8 mains cycles (loop 1), a new
Fail = 0
Autosupply
preheat period, shorter than the first one, starts
again (loop 3), followed by a new ignition attempt.
* see the preheat duration table § 6
The driver will try to fire the tube 8 times. If none of
the 8 attempts succeeds in striking the lamp, the driver turns in standby mode, and the whole starter is fully
stopped until the next mains removal and power supply reset.
5. If the lamp is ignited:
If the lamp is ignited, the driver stays in standby mode while monitoring the state of the lamp (loop 2).
During normal operation of the tube, this short pulse is masked by the lamp conduction. If the mains
interruption is really long enough to turn off completely the lamp, a new ignition sequence starts again (loop
3) with 8 other new possible attempts.
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