ncp1652 ON Semiconductor, ncp1652 Datasheet - Page 24

• Manufacturer Part Number: ncp1652
• Description: Power Factor Controllers
• Manufacturer: ON Semiconductor

has a nominal gain of 100 mS (or 0.0001 A/V). That is, an
input voltage difference of 10 mV causes the output current
to change by 1.0 mA. The AC EA has typical source and sink
currents of 70 mA.
frequency pole forces the average input current to follow the
reference generator output. A pole-zero pair is created by
placing a (R
by I
ramp compensation current. OUTA is terminated once the
voltage at the PWM non-inverting input reaches 4 V.
Current Sense Amplifier
applied to the current sense input, IS
The filtered input current is a high frequency signal. A low
The voltage at the PWN non-inverting input is determined
A voltage proportional to the main switch current is
ACEA(out)
R
IAVG
, the instantaneous switch current along and the
I
COMP
ACEA(out)
) and capacitor (C
I
AVG
+
2.8 * V
V
AC_REF
37.33k
POS
ACEA
. The current sense
+
−
gm
amplifier
AC COMP
g
AC error
Figure 62. AC EA Buffer Amplifier
@ 4
COMP
m
= 100mS
2.8V
) series
+
(eq. 1)
http://onsemi.com
R
AC_COMP
24
+
+
−
−
combination at the output of the AC EA. The AC COMP pin
provides access to the AC EA output.
current using a second transconductance amplifier. The
output of the inverting transconductance amplifier is
V
AC EA buffer. The AC EA buffer output current, I
is given by Equation 1.
amplifier is a wide bandwidth amplifier with a differential
input. The current sense amplifier has two outputs, PWM
Output and I
instantaneous switch current which is filtered by the internal
leading edge blanking (LEB) circuitry prior to applying it to
the PWM Comparator non inverting input. The second
output is a filtered current signal resembling the average
value of the input current. Figure 63 shows the internal
architecture of the current sense amplifier.
ACEA(buffer).
The output of the AC EA is inverted and converted into a
VDD
Figure 62 shows the circuit schematic of the
AVG
37.33kW
x 4
Output. The PWM Output is the
I
ACEA(out)
21.33kW
comparator
To PWM
ACEA(out)
,