CM6802A CHAMP [Champion Microelectronic Corp.], CM6802A Datasheet - Page 17

• Manufacturer Part Number: CM6802A
• Description: EPA/80++ ZVS-Like PFC/PWM COMBO CONTROLLER
• Manufacturer: CHAMP [Champion Microelectronic Corp.]

http://www.championmicro.com.tw
PFC Voltage Loop
voltage loop error amplifier, V
response. Optimizing interaction between transient response
and stability requires that the error amplifier’s open-loop
crossover frequency should be 1/2 that of the line frequency,
or 23Hz for a 47Hz line (lowest anticipated international
power frequency).
deviate from its 2.5V (nominal) value. If this happens, the
transconductance of the voltage error amplifier, GMv will
increase significantly, as shown in the Typical Performance
Characteristics. This raises the gain-bandwidth product of the
voltage loop, resulting in a much more rapid voltage loop
response to such perturbations than would occur with a
conventional linear gain characteristics.
The Voltage Loop Gain (S)
Z
GM
P
V
380V.
C
PFC Current Loop
compensation is similar to that of the voltage error amplifier,
V
The crossover frequency of the
the voltage amplifier, to prevent interaction with the voltage
loop. It should also be limited to less than 1/6th that of the
switching frequency, e.g. 8.33kHz for a 50kHz switching
frequency.
2009/11/02
CV
IN
OUTDC
DC
EAO
There are two major concerns when compensating the
The
current amplifier should be at least 10 times that of
: Average PFC Input Power
: Compensation Net Work for the Voltage Loop
v
: PFC Boost Output Capacitor
: Transconductance of VEAO
with exception of the choice of crossover frequency.
=
≈
: PFC Boost Output Voltage; typical designed value is
current
ΔV
V
ΔV
OUTDC
OUT
EAO
Rev. 1.4
2
*
P
transcondutance
*
ΔV
IN
ΔV
ΔV
*
OUT
2.5V
FB
EAO
Design for High Efficient Power Supply at both Full Load and Light Load
*
*
ΔV
S
ΔV
EAO
*
EAO
C
FB
; stability and transient
DC
amplifier,
*
CM6802A/B/AH/BH
GM
Champion Microelectronic Corporation
V
EPA/80++ ZVS-Like PFC/PWM COMBO CONTROLLER
*
GMi,
Z
CV
I
EAO
The Current Loop Gain (S)
Z
GM
V
380V and we use the worst condition to calculate the Z
R
2.5V: The Amplitude of the PFC Leading Edge Modulation
Ramp(typical)
L: The Boost Inductor
error amplifier, V
that
transconductance of the error amplifier, GMv is at a local
minimum. Rapid perturbation in line or load conditions will cause
the input to the voltage error amplifier (V
I
The I
Filter is between 100 ohm and 50 ohm because I
resistor can generate an offset voltage of IEAO. By selecting
R
5mV. Usually, we design the pole of I
fpfc/6=8.33Khz, one sixth of the PFC switching frequency.
Therefore, the boost inductor can be reduced 6 times without
disturbing the stability. Therefore, the capacitor of the I
Filter, C
SENSE
1.) Protection: During start up or inrush current conditions, it will
2.) To reduce L, the Boost Inductor: The I
CI
OUTDC
SENSE
FILTER
The gain vs. input voltage of the CM6802A/B/AH/BH’s voltage
There are 2 purposes to add a filter at I
: Compensation Net Work for the Current Loop
I
: Transconductance of IEAO
have a large voltage cross Rs which is the sensing resistor
of the PFC boost converter. It requires the I
attenuate the energy.
L, the Boost Inductor: The I
Boost Inductor value since the I
integrator before going I
current error amplifier, IEAO.
SENSE
=
≈
Filter, the RC filter between R
: The Sensing Resistor of the Boost Converter
: PFC Boost Output Voltage; typical designed value is
equal to 50 ohm will keep the offset of the IEAO less than
under
FILTER
ΔV
V
S
ΔD
OUTDC
*
Filter is a RC filter. The resistor value of the I
ISENSE
L
, will be around 381nF.
(Dynamic Soft PFC/Green PWM)
OFF
*
2.5V
*
EAO
steady-state
R
*
S
has a specially shaped non-linearity such
ΔD
ΔI
*
GM
EAO
OFF
I
SENSE
*
*
SENSE
ΔI
Z
operating
ΔI
CI
SENSE
SENSE
SENSE
which is the input of the
EAO
Filter also can reduce the
FB
SENSE
and I
) to
Filter behaves like an
SENSE
SENSE
pin:
conditions
SENSE
Filter To reduce
SENSE
:
OFFSET
CI
Filter at
Filter to
17
x the
SENSE
SENSE
the