CM6805BO
10-PIN Green-Mode PFC/PWM Combo CONTROLLER
UVLO
The UVLO threshold is 13V providing 3V hysteresis.
PFCOUT and PWMOUT
Both PFCOUT and PWMOUT are CMOS drivers. They both
have adaptive anti-shoot through to reduce the switching
loss. Its pull-up is a 30ohm PMOS driver and its pull-down
is a 15ohm NMOS driver. It can source 0.5A and sink 1A if
the VCC is above 15V.
PWM Section
After 10mS digital soft start, CM6805BO’s PWM is
operating as a typical current mode. It requires a secondary
feedback, typically, it is configured with CM431, and photo
couple.
Since PWM Section is different from CM6800 family, it
needs the emitter of the photo couple to connected with V+
I instead of the collector. The PWM current information also
goes into V+I. Usually, the PWM current information
requires a RC filter before goes into the V + I.
Therefore, V+I actually is a summing node from voltage
information which is from photo couple and CM431 and
current information which is from one end of PWM sensing
resistor and the signal goes through a single pole, RC filter
then enter the V+I pin.
This RC filter at V+I also serves several functions:
1.) It protects IC.
2.) It provides level shift for voltage information.
3.) It filters the switching noise from current
information.
At normal operation, the threshold voltage of the V + I pin is
1.5V. When the V + I is greater than 1.5V, PWM output
driver will turn off the PWM Power MOSFET.
When the Soft Start is triggered, the V+I threshold is around
150mV.
Soft Start Can be triggered by the following conditions:
1.) During the startup (VCC is less than 10V)
2.) Vfb is below ~ 1.1V
During above 2 conditions, the V + I threshold is around
150mV until the conditions have been removed.
After above 2 conditions have been removed, the internal
Soft Start D to A will ramp up the voltage from ~150mV to
2V. Each Soft Start Ramp can last around 10mS.
Component Reduction
Components associated with the VRMS and IEAO pins of a
typical PFC controller such as the CM6800 have been
eliminated. The PFC power limit and bandwidth does vary
with line voltage.
2010/04/20 Rev 1.3
Champion Microelectronic Corporation
Page 12
CHAMP [ CHAMPION MICROELECTRONIC CORP. ]
