NCP1603
http://onsemi.com
4
PIN FUNCTION DESCRIPTION
Pin
Symbol
Function
Description
1
V
aux
Auxiliary Supply
This pin connects to the V
CC1
pin externally. It delivers a bias voltage from the V
CC2
to the
PFC section. The V
aux
is disabled when either one of the following conditions occurs:
(1) V
aux
is initially off;
(2) Fault (V
FB2
> 3.0 V for more than 125 ms);
(3) Standby (V
FB2
< 0.75 V and then V
FB2
is smaller than 1.25 V for more than 125 ms);
(4) Overvoltage protection latch activated from CS2 pin;
(5) Thermal shutdown latch in the PWM section;
(6) Insufficient supply voltage (V
CC2
< 7.7 V).
The transistor turns on (or V
aux
is enabled) when V
FB2
is within the normal mode regulation
window (0.75 V < V
FB2
< 3.0 V).
2
FB2
PWM Feedback
An external optocoupler collector pulls the voltage of this pin V
FB2
down to regulate the
output voltage. The PWM regulation window between V
FB2
= 0.75 V and V
FB2
= 3.0 V. When
V
FB2
drops below 0.75 V, the controller enters standby operation.
When no feedback signal is received from the optocoupler, V
FB2
is internally pulled to be
higher than 3.0 V. If this condition lasts for longer than 125 ms, the controller enters
doublehiccup fault condition.
3
CS2
PWM Current Sense
This pin cumulates three different functions: currentmode PWM regulation, primary
overcurrent protection and overvoltage protection (OVP). If the voltage of this pin is above
3.0 V for OVP, the circuit is latched off until V
CC2
resets. The PWM Drive Output is disabled.
An external noise decoupling pForder capacitor is connected to the pin to prevent the latch
protection activated due to noise.
4
GND2
PWM Ground
5
Osc
PFC Oscillator
In oscillator mode, this pin is connected to an external capacitor to set the oscillator
frequency in DCM operation. In synchronization mode, this pin is connected to an external
driving signal. However, if the PFCstage inductor current is nonzero at the end of a
switching period, the PFCstage circuit will be forced to CRM and the Out1 is out of
synchronization to the Osc pin signal.
6
GND1
PFC Ground
7
Out1
PFC Drive Output
This pin provides an output to an external MOSFET in the PFC section.
8
V
CC1
PFC Supply Voltage
This pin is the positive supply of the PFC section. the operating range is between 9.0 V and
18 V with UVLO start threshold 10.5 V.
9
FB1
PFC Feedback
This pin receives a current I
FB1
that represents the PFC circuit output voltage. The current is
for the output regulation, PFC section overvoltage protection (OVP) and PFC section output
undervoltage protection (UVP). When I
FB1
goes above 107% I
ref
, OVP is activated and the
Drive Output is disabled. When I
FB1
goes below 14 mA, the PFC section enters a
lowcurrent consumption shutdown mode.
10
V
control
PFC Control Voltage
The control voltage V
control
directly controls the input impedance and hence the power factor
of the circuit. This pin is connected to an external capacitor to limit the control voltage
bandwidth typically below 20 Hz to achieve Power Factor Correction purpose.
11
CS1
PFC Current Sense
This pin receives a current I
S
that is proportional to the inductor current. The current is for
overcurrent protection (OCP), and zero current detection. When I
S
goes above 200 mA, OCP
is activated and the Drive Output (Out1) is disabled. When I
S
goes below 14 mA, it is
recognized to be a zero current for feedback regulation and DCM or CRM operation in the
PFC oscillator section.
12
Ramp
PFC Ramp
This pin is connected to an external capacitor to set a ramp signal. The capacitor value
directly affects the input impedance of the PFC circuit and its maximum input power.
13
Out2
PWM Drive Output
This pin provides an output to an external MOSFET in the PWM section.
14
V
CC2
PWM Supply Voltage
This pin is basically the positive supply of the PWM section. It is also the positive supply of
the whole device because the PFC section is also supplied from this pin indirectly through
V
aux
pin (Pin 1). The operating range is between 7.7 V and 18 V. The circuit resets when
V
CC2
drops below 4.0 V.
15
NC
No Connected
This pin is for high voltage clearance of the HV pin.
16
HV
High Voltage
This pin connects to the bulk DC voltage to deliver power to the controller in startup or fault
condition. The internal startup circuit is disabled in normal and standby condition for power
saving purpose. The UVLO stop and start thresholds of the startup circuit are V
CC2
= 12.6 V
and V
CC2
= 5.6 V.