Texas Instruments TPS92310-12 Evaluation Module TPS92310-12FB/NOPB TPS92310-12FB/NOPB Datenbogen
Produktcode
TPS92310-12FB/NOPB
R2
R3
D2
C
ZCD
PGND
PGND
PGND
L3
VCC
ZCD
D
ZCD
GATE
ISNS
PGND
Q1
R
ISNS
TPS92310
PGND
SNVS792 – FEBRUARY 2012
Figure 21. R
ISNS
Resistor Interface
Figure 22. Auxiliary Winding Interface to ZCD
Auxiliary Winding Interface To ZCD
In
, R2 and R3 forms a resistor divider which sets the thresholds for over voltage protection of V
LED,
V
ZCD-OVP
, and V
ZCD-PEAK
. Before the calculation, we need to set the voltage of the auxiliary winding, V
LAUX
at open
circuit.
For example :
Assume the nominal forward voltage of LED stack (V
LED
) is 21V.
To avoid false triggering ZCD
OVP
voltage threshold at normal operation, select ZCD
OVP
voltage at 1.3 times of the
V
LED
is typical in most applications. In case the transformer leakage is higher, the ZCD
OVP
threshold can be set
to 1.5 times of the V
LED
.
In this design example, open circuit AUX winding OVP voltage threshold is set to 30V. Assume the current
through the AUX winding is 0.4mA typical.
through the AUX winding is 0.4mA typical.
As a result, R2 is 66k
Ω
and R3 is 11k
Ω
. Also, for suppressing high frequency noise at the ZCD pin, a 15pF
capacitor connects the ZCD pin to ground is recommended.
Auxiliary Winding V
cc
Diode Selection
The V
CC
diode D
2
provides the supply current to the controller, low temperature coefficient , low reverse leakage
and ultra fast diode is recommended.
Compensation Capacitor And Delay Timer Resistor Selection
To achieve PFC function with a constant on time flyback converter, a low frequency response loop is required. In
most applications, a 2.2µF C
most applications, a 2.2µF C
COMP
capacitor is suitable for compensation.
Copyright © 2012, Texas Instruments Incorporated
15
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