NCP1650_15 Datasheet, PDF (23/31 Pages) ON Semiconductor – Power Factor Controller

NCP1650
D₁
V_in ^D2
D₃
D₄
DESIGN GUIDELINES
LOOP COMP
V_CC 1
C_in
7
4.24 V
+
-
4V
R₇
ERROR
FB/SD
C₇
6
+ ^AMP
-
4V
VOLTAGE/POWER
ORing NETWORK
REFERENCE
REGULATOR
+
-
P_COMP 3.68 V
0.85 V
-
+
SHUTDOWN
UVLO
R₈
R₉
C₈
8
P_max
9
C₉
R_ac1
AC INPUT
5
AC REF
a
POWER
MULTIPLIER
p
a
REFERENCE
MULTIPLIER
p
POWER
AMP
+
-
2.5 V
4V -
+
1.08 V_ref
OVERVOLTAGE
COMPARATOR
AC
REFERENCE
BUFFER
S
AC ERROR AMP
+
- _{0.75 Vline +}
k ⋅ I_in = V_ref
V−I
16 k
4V
-
+
SQ
PWM
R
4
25 k
4.5 V
6.5 V
2
V_ref
0.1 mF
C_ref
INRUSH
LIMITER
(OPTIONAL)
L₁
D₅
R_ac2
C_ac
AC COMP
3
C₄
R₃
C₃
GND
15
20 k
+
-
60 k
AVERAGE CURRENT
COMPENSATION
RAMP
COMPENSATION
OSCILLATOR
13
RAMP
COMP
R₁₃
14 CT
C_T
DRIVER
OUT
16
+
CURRENT
SENSE
AMPLIFIER
I_S−
−
12
I_avg 10 11 I_{avg fltr}
R₁₀
C₁₁
Q1
C_out
R_shunt
R_DC1
to FB
R_DC2
Note: This is a theoretical design, and it is not implied that a circuit designed by this procedure will operate properly without normal
troubleshooting and adjustments as are common with any power conversion circuit. ON Semiconductor provides a spread sheet that
incorporates the following equations, and will calculate the bias components for a circuit using the above schematic.
Figure 40. Typical Application Schematic
Basic Specifications
The design of any power converter begins with a basic set
of specifications. As a minimum, the following parameters
should be known before beginning:
Po_max (Maximum rated output power)
Vrms_min (Minimum operational line voltage)
Vrms_max (Maximum operational line voltage)
f_switch (Nominal switching frequency)
V_out
(Nominal regulated output voltage)
Most of these parameters will be dictated by system
requirements. The output voltage may not be defined. In
general, it should be slightly greater than the peak of the line
waveform at high line. For a 265 v_rms input, the peak line
voltage would be 375 volts, and 400 volts is a standard
output voltage. In no case should it be less than the peak
input line voltage.
Inductor
For an average current mode, fixed frequency PFC
converter, there is no magic formula to determine the
optimum value of the inductor. There are several trade−off’s
that should be considered. These include peak current vs.
average current, and switching losses vs. core losses. All of
these are a function of inductance, line and load. These
parameters determine when the converter is operating in the
continuous conduction mode and when it is operating in the
discontinuous conduction mode.
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