Datasheet

V
CC
V
SW
V
ZCD
V
ZCD-ARM
V
ZCD-OVP
25.6V
13V
Startup
state
Low Freq state
Steady state
t
t
t
TPS92311
SNVS811B –MAY 2012–REVISED MAY 2013 www.ti.com
Startup Bias and UVLO
During startup, the TPS92311 is powered from the AC line through R
1
and D
1
(Figure 1). In the startup state,
most of the internal circuits of the TPS92311 are shut down in order to minimize internal quiescent current. When
V
CC
reaches the rising threshold of the V
CC-UVLO
(typically 25.6V), the TPS92311 is operating in a low switching
frequency mode, where t
ON
and t
OFF
are fixed to 1.5μs and 72μs. When V
ZCD–PEAK
is higher than V
ZCD-ARM
, the
TPS92311 enters normal operation.
Figure 16. Start up Bias Waveforms
Mode Decoder
The TPS92311 is capable of operating in two control modes as an isolated topology, Peak Current Mode (PCM)
or Constant On-Time (COT). The TPS92311 can also be configured in a non-isolated topology using COT
operation. Depending on system requirements, the designer will chose between the two modes of operation.
COT mode gives a high power factor, PCM can achieve a lower output current ripple. COT mode using a non-
isolated topology can achieve a higher efficiency and good load regulation. The above modes can be selected by
setting the MODE1 and MODE2 pins according to Table 1.
Table 1. MODE Configuration
MODE1 MODE2 Mode of operation
OPEN OPEN COT mode using isolated topology
GND OPEN PCM using isolated topology
OPEN GND COT mode using non-isolated topology
GND GND Reserved
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