CM6800 Champion Microelectronic Corp., CM6800 Datasheet - Page 12

• Manufacturer Part Number: CM6800
• Description: LOW START UP CURRENT PFC/PWM CONTROLLER COMBO
• Manufacturer: Champion Microelectronic Corp.

Z
GM
V
is 380V and we use the worst condition to calculate the Z
R
2.5V: The Amplitude of the PFC Leading Modulation Ramp
L: The Boost Inductor
There is a modest degree of gain contouring applied to the
transfer characteristic of the current error amplifier, to
increase its speed of response to current-loop
perturbations. However, the boost inductor will usually be
the dominant factor in overall current loop response.
Therefore, this contouring is significantly less marked than
that of the voltage error amplifier. This is illustrated in the
Typical Performance Characteristics.
2004/02/11
CI
OUTDC
S
: The Sensing Resistor of the Boost Converter
: Compensation Net Work for the Current Loop
I
: Transconductance of IEAO
: PFC Boost Output Voltage; typical designed value
Rev. 1.6
Champion Microelectronic Corporation
L
OW
S
TART-
CI
U
P
C
I
There are 2 purposes to add a filter at I
The I
Filter is between 100 ohm and 50 ohm because I
resistor can generate an offset voltage of IEAO. By selecting
R
than 5mV. Usually, we design the pole of I
fpfc/6, 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
C
URRENT
SENSE
FILTER
FILTER
1.) Protection: During start up or inrush current
2.) To reduce L, the Boost Inductor: The I
SENSE
Filter, the RC filter between R
, will be around 283nF.
equal to 50 ohm will keep the offset of the IEAO less
conditions, it will have a large voltage cross Rs
which is the sensing resistor of the PFC boost
converter. It requires the I
the energy.
also can reduce the Boost Inductor value since the
I
I
amplifier, IEAO.
SENSE
SENSE
Filter is a RC filter. The resistor value of the I
PFC/PWM C
Filter behaves like an integrator before going
which is the input of the current error
ONTROLLER
S
SENSE
and I
SENSE
CM6800/1
Filter to attenuate
SENSE
SENSE
SENSE
pin:
SENSE
Page 12
Filter at
:
OFFSET
Filter,
C
Filter
OMBO
x the
SENSE