TK75003
PWM CONTROLLER
FEATURES
s
Power Factor Correction/Line Harmonics
Reduction to Meet IEC1000-3-2 Requirements
s
Optimized for Off-Line Operation
s
Maximum Duty Ratio 88% (typ.)
s
Frequency Reduction for Improved Overcurrent
Protection
s
Low Standby Current for Current-Fed Start-Up
s
Current-Mode or Voltage-Mode Control
s
Internal User-Adjustable Slope Compensation
s
Functionally Integrated & Simplified 5-Pin Design
APPLICATIONS
s
Power Factor Correction Converters
s
Off-Line Power Supplies
s
Industrial Power Supplies
s
Telecom Power Supplies
s
Off-Line Battery Chargers
DESCRIPTION
The TK75003 is a simple primary side controller optimized
for off-line switching power supplies including power factor
correctors. It is suitable for both voltage-mode and current-
mode control and has advanced features not available in
controllers with a higher pin count. The key to full
functionality in a 5-pin design is that the current signal and
the error signal are added together and fed into the
feedback pin. A sawtooth current flowing out of the feedback
pin provides a slope compensation ramp (in current-mode
applications) or a PWM ramp (in voltage-mode
applications), in proportion to the resistance terminating
that pin. If the sum of the current sense signal, error signal
and ramp signal exceeds the Overcurrent Detector
threshold indicating that the Current Control Detector has
lost control of the switch current, the charging current of
the timing capacitor will be reduced to about 25% for the
remainder of the clock period. The reduced charging
current causes no more than a one-third reduction in
switching frequency, effectively preventing short-circuit
current runaway.
TK75003
DRV
VCC
NC
NC
GND
3
7500
GND
CT
FB
Note: Pins 2 and 3 must be externally
connected for proper operation.
BLOCK DIAGRAM
VCC
ICT
CT
ICHG
205 µA
OSCILLATOR
IFR
146 µA
IDS
2 mA
fCLK
BANDGAP
REFERENCE
14.5 V
10.5 V
17.5 V
UVLO
ORDERING INFORMATION
Q
R
FREQUENCY
REDUCTION
LATCH
S
TK75003D
Tape/Reel Code
Temperature Code
SLOPE
COMPENSATION
PWM LATCH
S
Q
R
DRV
OVERCURRENT
DETECTOR
1.35 V
TEMP. CODE (OPTIONAL)
I: -40 to +85 C
TAPE/REEL CODE
MG: Magazine
FB
0.98 V
CURRENT
CONTROL
DETECTOR
GND
January 1999 TOKO, Inc.
Page 1
TOKO [ TOKO, INC ]
