NCP1605, NCP1605A, NCP1605B
http://onsemi.com
6
PIN FUNCTION DESCRIPTION
Pin
Number
Name
Function
1
STBY
An external signal (typically, a portion of the feedback signal of the downstream converter or a filtered
portion of the SMPS drive pulses) should be applied to Pin 1. When the Pin 3 voltage goes below
300 mV, the circuit enters a burst mode operation where the bulk voltage varies between the regulation
voltage and 95.5% of this level.
2
BrownOut /
Inhibition
Apply a portion of the averaged input voltage to detect brownout conditions. If V
Pin2
is lower than
0.5 V, the circuit stops pulsing until V
Pin2
exceeds 1 V (0.5 V hysteresis).
Ground Pin 6 to disable the part.
3
V
CONTROL
/
SoftStart
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 high Power Factor
ratios.
Pin 3 is grounded when the circuit is off so that when it starts operation, the power increases slowly
(softstart).
4
Feedback
This pin receives a portion of the preconverter output voltage. This information is used for the
regulation and the output low detection (V
OUT
L) that drastically speed up the loop response when the
output voltage drops below 95.5% of the wished level.
5
Current Sense
Input
This pin monitors a negative voltage proportional to the coil current. This signal is sensed to limit the
maximum coil current and detect the core reset (coil demagnetization).
6
Current Sense
Output
This pin sources the Pin 5 current. Place a resistor between Pin 6 and ground to build the voltage
proportional to the coil current and detect the core reset. The impedance between Pin 6 and ground
should not exceed 3 times that of the Pin 5 to ground. You can further apply the voltage from an
auxiliary winding to improve the valley detection of the MOSFET drain source voltage.
7
Ct
(Ramp)
The circuit controls the power switch ontime by comparing the Pin 7 ramp to an internal voltage
(V
ton
) derived from the regulation block and the sensed dcycle (relative duration of the current cycle
over the corresponding switching period).
Pin 7 sources a current proportional to the squared output voltage to allow the Follower Boost operation
(optional) where the PFC output voltage stabilizes at a level that varies linearly versus the ac line
amplitude. This technique reduces the difference between the output and input voltages, to optimize the
boost efficiency and minimize the size and cost of the PFC stage
8
Oscillator /
synchronization
Connect a capacitor or apply a synchronization signal to this pin to set the switching frequency. If the
coil current cycle is longer than the selected switching period, the circuit delays the next cycle until the
core is reset. Hence, the PFC stage can operate in CRM in the most stressful conditions.
9
GND
Connect this pin to the preconverter ground.
10
Drive
The high current capability of the totem pole gate drive (+0.5/0.8 A) makes it suitable to effectively
drive high gate charge power MOSFETs.
11
V
CC
This pin is the positive supply of the IC. The circuit starts to operate when V
CC
exceeds 15 V (10.5 V
for NCP1605A) and turns off when V
CC
goes below 9 V (typical values). After startup, the operating
range is 10 V up to 20 V.
12
PfcOK / REF5V
The Pin 12 voltage is high (5 V) when the PFC stage is in a normal, steady state situation and low
otherwise. This signal serves to inform the downstream converter that the PFC stage is ready and
that hence, it can start operation.
13
STDWN
Apply a voltage higher than 2.5 V on Pin 13 to permanently shutdown the circuit. This pin can be used
to monitor the voltage across a thermistor in order to protect the application from an excessive heating
and/or to detect an overvoltage condition.
To resume operation, it is necessary to decrease the circuit V
CC
below V
CC
RST (4 V typically) by for
instance, unplugging the PFC stage and replugging it after V
CC
is discharged.
14
OVP / UVP
The circuit turns off when V
Pin14
goes below 300 mV (UVP) and disables the drive as long as the pin
voltage exceeds 2.5 V (OVP).
15
NC
Creepage distance.
16
HV
Connect Pin 16 to the bulk capacitor. The internal startup current source placed between Pin 16 and the
V
CC
terminal, charges the V
CC
capacitor at startup.