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PDF CM6903A Data sheet ( Hoja de datos )
| Número de pieza | CM6903A | |
| Descripción | Low Pin Count PFC/PWM CONTROLLER COMBO | |
| Fabricantes | Champion Microelectronic | |
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CM6903A
Low Pin Count PFC/PWM CONTROLLER COMBO
GENERAL DESCRIPTION
FEATURES
The CM6903A is a space-saving PFC-PWM controller
for power factor corrected, switched mode power supplies
that offers very low start-up and operating currents. For the
power supply less than 500Watt, its input current shaping
PFC performance could be very close to CM6800 or
ML4800 architecture.
Power Factor Correction (PFC) 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 CM6903A includes circuits for the implementation of a
leading edge, input current shaping technique “boost” type
PFC and a trailing edge, PWM.
The CM6903A’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.
Patent Number #5,565,761, #5,747,977, #5,742,151,
#5,804,950, #5,798,635
Pin to pin compatible with FAN6903/4
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, PFC VCCOVP, Precision -1V PFC ILIMIT,
Tri-Fault Detect comparator to meet UL1950
No bleed resistor required
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
VINOK Comparator to guarantee to enable PWM when
PFC reach steady state
High efficiency trailing-edge current mode PWM
UVLO, REFOK, and brownout protection
Digital PWM softstart: CM6903A (10ms)
Precision PWM 1.5V current limit for current mode
operation
APPLICATIONS
Desktop PC
AC Adaptor
Open Frame
PIN CONFIGURATION
SIP-09 (Z09)
Front View
123456789
2008/10/20 Rev1.4
Champion Microelectronic Corporation
Page 1
1 page  
CM6903A
Low Pin Count PFC/PWM CONTROLLER COMBO
ELECTRICAL CHARACTERISTICS (Conti.) Unless otherwise stated, these specifications apply
Vcc=+15V, TA=Operating Temperature Range (Note 1)
Symbol
Parameter
Minimum Duty Cycle
Maximum Duty Cycle
Output Low Impedance
Output Low Voltage
Output High Impendence
Output High Voltage
Rise/Fall Time (Note 2)
Duty Cycle Range
Output Low Impedance
Output Low Voltage
Output High Impendence
Output High Voltage
Rise/Fall Time (Note 2)
Start-Up Current
Operating Current
Undervoltage Lockout Threshold
Undervoltage Lockout Hysteresis
Test Conditions
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
CM6903A
IOUT = -100mA
IOUT = -10mA, VCC = 8V
IOUT = 100mA, VCC = 15V
CL = 1000pF
Supply
VCC = 11V, CL = 0
VCC = 15V, CL = 0
CM6903A
Min.
Typ.
Max.
0
90 95
15 22.5
0.8 1.5
0.4 0.8
30 45
13.5 14.2
50
0-49.5
13.5
15
0.8
0.7
30
14.2
50
0-50
22.5
1.5
1.5
45
100 150
2.5 4.0
12.74 13.0 13.26
2.85 3.0 3.15
Unit
%
%
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.
2008/10/20 Rev1.4
Champion Microelectronic Corporation
Page 5
5 Page 
CM6903A
Low Pin Count PFC/PWM CONTROLLER COMBO
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
CM6903A, it is a relatively easy thing to design.
Use a more than 800K ohm resistor for your
demand, 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, and VREFOK
During the Start-up period, RAC resistor will provide the start
up current~100uA from the rectified line voltage to IAC pin.
Inside of CM6903A during the start-up period, IAC is
connected to VCC until the VCC reaches UVLO voltage
which is 13V and internal reference voltage is stable, it will
disconnect itself from VCC.
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
2.45V. 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.
Tri-Fault Detect Comparator
To improve power supply reliability, reduce system
component count, and simplify compliance to UL1950 safety
standards, the CM6903A includes Tri-Fault Detect. This
feature monitors VFB (Pin 8) 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, Tri-Fault Detect senses the error
and terminates the PFC output drive.
Tri-Fault detect is an entirely internal circuit. It requires no
external components to serve its protective function.
VCC OVP and generate VCC
For the CM6903A system, if VCC is generated from a source
that is proportional to the PFC output voltage and once that
source reaches 17.9V, PFCOUT, PFC driver will be off.
The VCC OVP resets once the VCC discharges below
16.4V, PFC output driver is enabled. It serves as redundant
PFC OVP function.
Typically, there is a bootstrap winding off the boost inductor.
The VCC OVP comparator senses when this voltage
exceeds 17.9V, and terminates the PFC output drive. Once
the VCC rail has decreased to below 16.4V the PFC output
drive be enabled. Given that 16V on VCC corresponds to
380V on the PFC output, 17.9V on VCC corresponds to an
OVP level of 460V.
It is a necessary to put RC filter between bootstrap winding
and VCC. For VCC=13V, it is sufficient to drive either a
power MOSFET or a IGBT.
2008/10/20 Rev1.4
Champion Microelectronic Corporation
Page 11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet CM6903A.PDF ] | |
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