tea1566s NXP Semiconductors, tea1566s Datasheet - Page 5

• Manufacturer Part Number: tea1566s
• Description: Greenchip; Smps Module
• Manufacturer: NXP Semiconductors

Philips Semiconductors
In case of output short circuit, the Vaux capacitor is no
longer supplied by the auxiliary winding and its voltage
drops till it reaches the UVLO level. If the output is an open
circuit, the output voltage will rise till it reaches the Over
Voltage Protection (OVP) level. The IC will detect this state
and stop switching.
In absence of switching of the power device, the Vaux
capacitor will not be re-supplied and its voltage will drop till
it reaches UVLO level. Once the Vaux voltage drops to
UVLO level, the start-up current source is re-activated and
it charges the Vaux capacitor to its start level and the
system goes through a cycle similar to the start-up cycle.
Figure 5 shows the relevant waveforms during safe-restart
mode. The charging current (see symbol ‘Irestart-prot’ in
Chapter “Characteristics”) from the start-up circuit during
the safe-restart mode is lower than the normal start-up
current (see symbol ‘Istart-high’ in
Chapter “Characteristics”) in order to implement a low
“hiccup” duty cycle. This helps insure devices on the
output secondary winding do not get destroyed during
output short circuit, violating safety conditions.
The start-up current source also plays a key role in
implementation of burst mode stand-by (see symbol
‘Irestart-stby’ in Chapter “Characteristics”), which will be
explained later.
1999 Apr 20
handbook, full pagewidth
GreenChip ; SMPS module
(1) Start-up current source charges capacitor V
Vgate
Vaux
normal operation
aux
.
Fig.5 Safe-start mode waveforms.
switching
fault condition
off
(1)
5
(1) Start-up current charges capacitor V
(2) Charging of capacitor V
Vgate
Vaux
Vout
Fig.4 Normal start-up waveforms.
8.05 V
11 V
off
(1)
aux
MGR695
is taken-over by the auxiliary winding.
t
t
switching
Preliminary specification
aux
(2)
.
TEA1566
t
t
t
MGR694