STMicroelectronics Double output SMPS for power line application using ALTAIR04-900 primary controller EVLALTAIR900-M1 EVLALTAIR900-M1 Data Sheet
Product codes
EVLALTAIR900-M1
ALTAIR04-900
Application information
Doc ID 18211 Rev 2
13/29
Figure 10.
Timing diagram: normal power-up and power-down sequences
5.3
Zero current detection and triggering block
The zero current detection (ZCD) and triggering blocks switch on the power MOSFET if a
negative-going edge falling below 50 mV is applied to the ZCD/FB pin. To do so, the
triggering block must be previously armed by a positive-going edge exceeding 100 mV.
negative-going edge falling below 50 mV is applied to the ZCD/FB pin. To do so, the
triggering block must be previously armed by a positive-going edge exceeding 100 mV.
This feature is used to detect transformer demagnetization for QR operation, where the
signal for the ZCD input is obtained from the transformer’s auxiliary winding used also to
supply the IC.
signal for the ZCD input is obtained from the transformer’s auxiliary winding used also to
supply the IC.
Figure 11.
ZCD block, triggering block
The triggering block is blanked after MOSFET’s turn-off to prevent any negative-going edge
that follows leakage inductance demagnetization from triggering the ZCD circuit
erroneously.
that follows leakage inductance demagnetization from triggering the ZCD circuit
erroneously.
This blanking time is dependent on the voltage on COMP pin: it is T
BLANK
= 30 µs for V
COMP
= 0.9 V, and decreases almost linearly down to T
BLANK
= 6 µs for V
COMP
= 1.3 V
Vcc
DRAIN
Vcc
ON
Vcc
resta rt
t
tt
t
Vin
V
Start
I
charge
5.5 mA
t
t
Power-on
Power-off
Normal operation
CV mode
CC mode
Normal operation
Vcc
DRAIN
Vcc
ON
Vcc
resta rt
t
tt
t
Vin
V
Start
I
charge
5.5 mA
t
t
Power-on
Power-off
Normal operation
CV mode
CC mode
Normal operation
60mV
ZCD
CLAMP
BLAN KIN G
TI ME
TU RN -ON
LOGI C
STAR TER
S
R
Q
LEB
+
-
Aux
Rf b
R zcd
To D riv er
Fr om CC /CV Block
F rom OC P
ZCD/FB
110mV