EVAL6569 Datasheet, PDF (5/14 Pages) Panasonic Semiconductor – THE L6569 A NEW HIGH VOLTAGE IC DRIVER FOR ELECTRONIC LAMP BALLAST

Figure 9. L6569 driver protection against voltage spikes.
BV OUT > 600V
15V
H.V.+
ON
AN880 APPLICATION NOTE
V OUT
L6569
I
OFF
The auxiliary supply of the converter
The circuit consumption is defined by the MOS-
mA, a secondary winding on the resonant choke
is an easy supply alternative.
FETs gate charge, the I.C. consumption, the os-
cillator, and the shunt regulator. Several circuits The ballast shutdown
are possible.
The L6569 allows several ways (see figg. 11, 12
In many applications a snubber is used to reduce and 13) to shutdown the ballast [4]: by acting on
the dissipation in the MOSFETs. When this snub-
ber is used in conjunction with a start up resistor
(RS in Figure 10), a non dissipative supply is
achieved almost for free.
At start up the I.C. is consuming 150 µA, and there-
fore only a small supply resistor is required. During
operation the capacitor provides the supply current.
To avoid cross conduction, the capacitance is lim-
ited by the driver dead time TD . Hence the capaci-
tive supply current IC is also limited.For a CFL bal-
last this circuit easily supplies the required
operating current. Using a CF18DT lamp ( IL > 230
mA) the required capacitance is 470 pF on 230 Vac
line. At 50 kHz the average capacitive current is 6
mA, as described in appendix B.
When the required driver current is higher than 10
the CF input oscillator pin to turn off the upper
MOSFET or by acting on the VS supply pin with
the Under Voltage Lock Out.
Acting on CF (Fig. 11) a limiting resistor RL has to
be used, and it has to be: RL ⋅ CF > 1µs.
When the shutdown is realized acting on Vs pin,
(see fig. 12) a limiting resistor Rs must be used to
slow down the discharge of the supply filter Cs.
The constant time of the discharge must be
greater than 10 periods of the switching fre-
quency:
RS
≥
10
C_s ⋅ f_sw
Connecting the CF pin to ground GND stops the
oscillator, and the lower MOSFET will remain ON.
Therefore the bootstrap capacitor remains
Figure 10: Non dissipative auxiliary supply using the transistor snubber.
1mA WHEN STARTING
220kΩ
Rs
6 mA WHEN 50 kHz SWITCHING
C _{470 pF}
bootstrap
circuit
Cs
L6569
310 V
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