ssl1750 NXP Semiconductors, ssl1750 Datasheet - Page 6

• Manufacturer Part Number: ssl1750
• Description: Smps Control Ic For Led Drivers
• Manufacturer: NXP Semiconductors

NXP Semiconductors
SSL1750_1
Product data sheet
7.1.1 Start-up and undervoltage lockout
Initially the capacitor on pin V
As long as V
V
increased until V
current is low again, ensuring a low duty cycle during fault conditions.
The control logic activates the internal circuitry and switches off the charge current when
the voltage on pin V
and the soft-start capacitors on the pins PFCSENSE and FBSENSE are charged. When
the voltage on pin LATCH exceeds the V
pin PFCSENSE is charged, the PFC circuit is activated. The supply current from the pin
HV is then switched on again and the PFC circuit charges the C
voltage on pin VOSENSE reaches the V
the flyback converter is activated (providing the soft-start capacitor on pin FBSENSE is
charged). The output voltage of the flyback converter is then regulated to its nominal
output voltage. The IC supply is taken over by the auxiliary winding of the flyback
converter. See
When the PFC is started, there is initially no supply takeover from the auxiliary winding. To
make a small V
long as the flyback converter has not yet started. Regulation is done by hysteretic control
with a limited (high level) charge current. The hysteresis is typically 300 mV.
If during start-up pin LATCH does not reach the V
V
Fig 4.
CC
th(UVLO)
is shorted to ground. For a short start-up time the charge current above V
, its output is deactivated and the charge current is switched on again.
Typical configuration of SSL1750
CC
Figure
CC
is below V
CC
capacitor possible, the V
CC
reaches V
Rev. 01 — 15 September 2008
5.
passes the V
trip
, the charge current is low. This protects the IC in case pin
CC
th(UVLO)
is charged from the high voltage mains via pin HV.
8
6
7
3
12
startup
. If V
11
start(fb)
en(LATCH)
SSL1750T
level. First, the output on pin LATCH is activated
CC
CC
2
is between V
9
level, the charge current is switched off and
voltage is regulated to the V
voltage and the soft-start capacitor on
en(LATCH)
16 13
10
4
1
SMPS control IC for LED drivers
th(UVLO)
level before V
bus
and V
capacitor. When the
SSL1750
© NXP B.V. 2008. All rights reserved.
startup
CC
startup
reaches
, the charge
trip
014aaa350
level, as
is
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