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PDF CM6805A Data sheet ( Hoja de datos )
| Número de pieza | CM6805A | |
| Descripción | 10-PIN Green-Mode PFC/PWM Combo CONTROLLER | |
| Fabricantes | Champion Microelectronic | |
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CM6805A
10-PIN Green-Mode PFC/PWM Combo CONTROLLER
GENERAL DESCRIPTION
The CM6805A is the Green-Mode PFC/PWM Combo
controller for Desktop PC and High Density AC Adapter.
For the power supply, it’s input current shaping PFC
performance could be very close to the performance of the
CM6800 or ML4800 leading edge modulation average
current topology.
CM6805A offers the use of smaller, lower cost bulk
capacitors, reduces power line loading and stress on the
switching FETs, and results in a power supply fully
compliant to IEC1000-3-2 specifications. The CM6805A
includes circuits for the implementation of a leading edge
modulation, input current shaping technique “boost” type
PFC and a trailing edge modulation current, PWM.
The CM6805A’s PFC and PWM operate at the same
frequency, 67.5kHz. A PFC OVP comparator shuts down
the PFC section in the event of a sudden decrease in load.
The PFC section also includes peak current limiting for
enhanced system reliability.
PFC has a PFCOFFB pin which can use for AC brown out
application and determine the GMth to turn off PFC.
FEATURES
10-Pin SOIC package.
Use RAC around 4~8 Mega Ohm at IAC pin.
Easy to configure into Boost Follower.
Enable lowest BOM for power supply with PFC.
Internally synchronized PFC and PWM in one IC.
Patented slew rate enhanced voltage error amplifier
with advanced input current shaping technique.
Universal Line Input Voltage
CCM boost or DCM boost with leading edge
modulation PFC using Input Current Shaping
Technique.
Feed forward IAC pin to do the automatic slope
compensation.
PFCOVP, Precision -1V PFC ILIMIT, PFC Tri-Fault
Detect comparator to meet UL1950
Low supply currents; start-up: 100uA typical,
operating current: 2mA typical.
Synchronized leading PFC and trailing edge
modulation PWM to reduce ripple current in the
storage capacitor between the PFC and PWM
sections and to reduce switching noise in the system
VIN-OK Comparator to guarantee to enable PWM
when PFC reach steady state
High efficiency trailing-edge current mode PWM
Exact 50% PWM maximum duty cycle
UVLO, REFOK, and brownout protection
Digital PFC and PWM soft start, ~10mS
Precision PWM 1.5V current limit for current mode
operation
PFCOFFB pin to sense light load to turn off PFC or
PFCOFFB pin to sense Input voltage as AC Brown
Out
2010/04/20 Rev 1.4
Champion Microelectronic Corporation
Page 1
1 page  
CM6805A
10-PIN Green-Mode PFC/PWM Combo CONTROLLER
ELECTRICAL CHARACTERISTICS Unless otherwise stated, these specifications apply Vcc=+14V,
TA=Operating Temperature Range (Note 1)
Symbol
Parameter
PFCOFFB Threshold Low
PFCOFFB Hysteresis
Voltage Stability
Temperature Stability
Total Variation
PFC Dead Time (Note 2)
Minimum Duty Cycle
Maximum Duty Cycle
Output Low Rdson
Output Low Voltage
Output High Rdson
Output High Voltage
Rise/Fall Time (Note 2)
Duty Cycle Range
Output Low Rdson
Output Low Voltage
Output High Rdson (Note 2)
Output High Voltage
Rise/Fall Time (Note 2)
Start-Up Current
Operating Current
Under voltage Lockout Threshold
Under voltage Lockout Hysteresis
Test Conditions
PFCOFFB
PFCOFFB
PFC Frequency
10V < VCC < 15V
Line, Temp (CM6805A)
PFC
IAC=100uA,VFB=2.55V, ISENSE = 0V
IAC=0uA,VFB=2.0V, ISENSE = 0V
IOUT = -100mA
IOUT = -10mA, VCC = 8V
IOUT = 100mA, VCC = 15V
CL = 1000pF
PWM
IC
At room temp
IOUT = -100mA
IOUT = -10mA, VCC = 8V
At room temp
IOUT = 100mA, VCC = 15V
CL = 1000pF
Supply
VCC = 11V, CL = 0
VCC = 15V, CL = 0
CM6805A
Min.
Typ.
Max.
4.75 5.0 5.25
350 500 750
1
2
60 67.5 74
0.3 0.45 0.65
1
90 95
15 22.5
0.8 1.5
0.4 0.8
30 45
13.5 14.2
50
49 49.5 50
15 22.5
0.8 1.5
0.7 1.5
30 45
13.5 14.2
50
135 150
24
12.35 13 13.65
2.7 3 3.3
Unit
V
mV
%
%
kHz
us
%
%
ohm
V
V
ohm
V
ns
%
ohm
V
V
ohm
V
ns
uA
mA
V
V
Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst-case test conditions.
Note 2: Guaranteed by design, not 100% production test.
2010/04/20 Rev 1.4
Champion Microelectronic Corporation
Page 5
5 Page 
CM6805A
10-PIN Green-Mode PFC/PWM Combo CONTROLLER
The ISENSE Filter is a RC filter. The resistor value of the
ISENSE Filter is between 100 ohm and 50 ohm. By selecting
RFILTER equal to 50 ohm will keep the offset of the IEAO less
than 5mV. Usually, we design the pole of ISENSE Filter at
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
ISENSE Filter, CFILTER, will be around 283nF.
IAC, RAC, Automatic Slope Compensation, DCM at high line
and light load, and Startup current
There are 4 purposes for IAC pin:
1.) For the leading edge modulation, when the duty
cycle is less than 50%, it requires the similar slope
compensation, as the duty cycle of the trailing
edge modulation is greater than 50%. In the
CM6805A, it is a relatively easy thing to design.
Use an more than 800K ohm resistor, RAC to
connect IAC pin and the rectified line voltage. It
will do the automatic slope compensation. If the
input boost inductor is too small, the RAC may
need to be reduced more.
2.) During the startup period, Rac also provides the
initial startup current, 100uA;therefore, the bleed
resistor is not needed.
3.) Since IAC pin with RAC behaves as a feedforward
signal, it also enhances the signal to noise ratio
and the THD of the input current.
4.) It also will try to keep the maximum input power to
be constant. However, the maximum input power
will still go up when the input line voltage goes up.
Start Up of the system, UVLO, VREFOK and Soft Start
During the Start-up period, RAC resistor will provide the
start up current~100uA from the rectified line voltage to IAC
pin. During the Start up, the soft start function is triggered
and the duration of the soft start will last around 10mS.
PFC section wakes up after Start up period
After Start up period, PFC section will softly start since
VEAO is zero before the start-up period. Since VEAO is a
slew rate enhanced transconductance amplifier (see figure
3), VEAO has a high impedance output like a current
source and it will slowly charge the compensation net work
which needs to be designed by using the voltage loop gain
equation.
Before PFC boost output reaches its design voltage, it is
around 380V and VFB reaches 2.5V, PWM section is off.
PWM section wakes up after PFC reaches steady state
PWM section is off all the time before PFC VFB reaches
2.25V. Then internal 10mS digital PWM soft start circuit
slowly ramps up the soft-start voltage.
PFC OVP Comparator
PFC OVP Comparator sense VFB pin which is the same the
voltage loop input. The good thing is the compensation
network is connected to VEAO. The PFC OVP function is a
relative fast OVP. It is not like the conventional error amplifier
which is an operational amplifier and it requires a local
feedback and it make the OVP action becomes very slow.
The threshold of the PFC OVP is 2.5V+10% =2.75V with
250mV hysteresis.
PFC Tri-Fault Detect Comparator
To improve power supply reliability, reduce system
component count, and simplify compliance to UL1950 safety
standards, the CM6805A includes PFC Tri-Fault Detect. This
feature monitors VFB (Pin 5) for certain PFC fault conditions.
In case of a feedback path failure, the output of the PFC
could go out of safe operating limits. With such a failure, VFB
will go outside of its normal operating area. Should VFB go
too low, too high, or open, PFC Tri-Fault Detect senses the
error and terminates the PFC output drive.
PFC Tri-Fault detect is an entirely internal circuit. It requires
no external components to serve its protective function.
VCC over voltage and generate VCC
For the CM6805A system, if VCC is generated from a source
that is proportional to the PFC output voltage. The PFC OVP
will avoid the VCC over voltage. Given that 16V on VCC
corresponds to 380V on the PFC output, 17.6V on VCC
corresponds to an acceptable level of 18V.
Typically, there is a bootstrap winding off the boost inductor.
The VCC isn’t built in the VCC OVP function. For the VCC
maximum rating, an external zener clamp is desirable and
proposed to limit VCC over voltage.
It is a necessary to put RC filter between bootstrap winding
and VCC. For VCC=15V, it is sufficient to drive either a
power MOSFET or a IGBT.
2010/04/20 Rev 1.4
Champion Microelectronic Corporation
Page 11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet CM6805A.PDF ] | |
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