PFS7323-7329
DRAIN (D)
BOOST DIODE CATHODE (K)
BIAS POWER (VCC)
VOLTAGE MONITOR (V)
IV
+
INTERNAL
SUPPLY
INPUT
LINE INTERFACE
VCC+
-
Peak
Detector
SOFT-
START
Input UV IVPK MON
CUV
FBOFF
/
(IUV+/IUV-
)
/
VREF
FBCOV
FBCUV
FBOV COFF IOCP VPG(H) IPGT
MOFF (IREF - IV)
~(VO-VIN
REFERENCE
(R)
)
REFERENCE
IREF
IV
AND BAND GAP
CINT
FBON
FBOFF
/
FEEDBACK
(FB)
+
Feedback-OVP/OFF
Comparator
VFB
-
VCC
VOFF is a function of the error-voltage
(VE) and is used to reduce the
average operating frequency as a
function of output power
Buffer and
De-Glitch Filter
FEEDBACK/
COMPENSATION Pin
OV/UV
+
FBCOV
Comparator
Comparator
-
senseFET
VCC
FBGM
Latch
+
-
-
Power
MOSFET
Frequency
Slide
IVPK Transconductance
VOFF
+
Error-Ampliꢀer
+
-
Internal
Reference
VREF
VE
1 kHz Filter
+
VE
FBCUV
+
-
COMPENSATION
IS
FBGM
LEB
+
-
-
(C)
mON is the switch
current sense scale
factor which is a function
of the peak input voltage
OCP
+
-
C-UV/OFF
Comparator
IOCP
+
PON × MON × IS
CUV/COFF
CINT
VCC
VFB
INPUT UV
OTP SOA
POWER GOOD
THRESHOLD
(PGT)
VPG(H)
+
IPGT
POWER GOOD
(PG)
SOURCE (S)
GROUND (G)
PI-6697-050312
Figure 3. Functional Block Diagram.
Functional Description
The HiperPFS-2 is a variable switching frequency boost PFC
solution. More specifically, it employs a constant amp-second
on-time and constant volt-second off-time control algorithm.
This algorithm is used to regulate the output voltage and shape
the input current to comply with regulatory harmonic current
limits (high power factor). Integrating the switch current and
controlling it to have a constant amp-sec product over the
on-time of the switch allows the average input current to follow
the input voltage. Integrating the difference between the output
and input voltage maintains a constant volt-second balance
dictated by the electro-magnetic properties of the boost
inductor and thus regulates the output voltage and power.
Since the volt-seconds during the on-time must equal the
volt-seconds during the off-time, to maintain flux equilibrium in
the PFC choke, the on-time (tON) is controlled such that:
#
VIN tON = K1
(2)
The controller also sets a constant value of charge during each
on-cycle of the power MOSFET. The charge per cycle is varied
gradually over many switching cycles in response to load
changes so it can be regarded as substantially constant for a
half line cycle. With this constant charge (or amp-second)
control, the following relationship is therefore also true:
More specifically, the control technique sets constant volt-
seconds for the off-time (tOFF). The off-time is controlled such
that:
#
IIN tON = K2
(3)
Substituting tON from (2) into (3) gives:
^
h
VO - VIN tOFF = K1
#
(1)
K2
K1
IIN = VIN #
(4)
4
Rev. B 06/13
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