ncp1927 ON Semiconductor, ncp1927 Datasheet - Page 4

• Manufacturer Part Number: ncp1927
• Description: Combination Power Factor Correction Controller And Flyback Controller For Flat Panel Tvs
• Manufacturer: ON Semiconductor

PIN FUNCTION DESCRIPTION
Pin No.
10
11
12
13
14
15
16
1
2
3
4
5
6
7
8
9
Pin Name
Shutdown
IENABLE
PControl
POVUV
PSKIP
PDRV
PZCD
FDRV
GND
PCS
GTS
PFB
PCT
FCS
FFB
V
CC
The gate drive is disabled while V
typical).
This pin receives a portion of the pre−converter output voltage. This information is used for the
regulation and the “output low” detection that speeds up the loop response when the output voltage
drops below 95.5% (typ) of the programmed level.
Pull this pin above 1.0 V (typ) to disable the part. Ground this pin when not in use.
The error amplifier output is available on this pin. The capacitor connected between this pin and
ground adjusts the regulation loop bandwidth that is typically set below 20 Hz to achieve a high power
factor. This pin is internally grounded when the circuit is off so that when it starts operation, the power
increases gradually (soft−start).
The PCT pin sources a 210 mA (typ) current to charge an external timing capacitor. The circuit
controls the power switch on time by comparing the PCT voltage to an internal voltage derived from
the regulation block.
The voltage of an auxiliary winding is applied to this pin to detect when the inductor is demagnetized
for operation in critical conduction mode.
This pin monitors a negative voltage proportional to the coil current. This signal is sensed to limit the
maximum coil current and protect the PFC stage during overload conditions.
Pull this pin low to disable the PFC controller during standby mode. Standby mode can also be
entered by monitoring the feedback voltage of the flyback stage with an external resistor divider.
This pin senses the primary current for current−mode operation of the flyback stage. Ramp
compensation can be added with an external resistor.
Connecting this pin to ground through an optocoupler allows regulation of the flyback stage.
This is the the controller ground.
This is the driver’s output to an external MOSFET gate of the flyback power stage.
This pin is connected to an external auxiliary voltage.
This is the driver’s output to an external MOSFET gate of the PFC power stage.
To adjust the power level below which the PFC stage will enter skip mode, connect a resistor between
this pin and ground. To disable skip mode, connect this pin directly to ground.
This pin voltage is high (5 V) when the output of the PFC stage is in steady state regulation and low
at all other times. This signal serves to “inform” the backlight inverter that the PFC output is ready and
that it can start operation. It can also be used as a stable 5 V reference.
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4
POVUV
is below V
Pin Description
UVP
(300 mV typical) or above V
OVP
(2.5 V