Datasheet
A fraction of the oscillator ramp can be resistively summed
with the current sense signal to provide slope compensation
for converters requiring duty cycles over 50%.
Note that capacitor C forms a filter with R2 to suppress the
leading-edge switch spikes.
R
SENSE
I
SENSE
R2
R1
C
R
T
C
T
0.1 µF
V
REF
R /C
T T
I
SENSE
UC2843A
8
4
3
Power Supply Specifications
1. Input Voltage 95 VAC to 130 VAC (50 Hz/60 Hz)
2. Line Isolation 3750 V
3. Switching Frequency 40 kHz
4. Efficiency, Full Load 70%
5. Output Voltage:
A. 5%; 1-A to 4-A Load5 V ±
B. 3%; 0.1-A to 0.3-A Load; Ripple voltage: 100 mV P-P Max±12 V
C. -12 V 3%; 0.1-A to 0.3-A Load; Ripple voltage: 100 mV P-P Max±
R1
5
1 W
W
117 VAC
VARO
VM 68
C1
250 µF
250 V
R2
56 k
2 W
W
R12
4.7 k
2 W
W
R4
4.7 kW
R3
20 kW
C9
3300 pF
600 V
D4
1N3613
NP
C12
2200 µF
16 V
C13
2200 µF
16 V
C11
4700 µF
10 V
N5
N12
C10
4700 µF
10 V
N12
D8
UES1002
C8
680 pF
600V
D5
1N3613
+5 V
COM
+12 V
±12 V COM
–12 V
R11
2.7 k
2 W
W
Q1
UFN833
R10
0.55
1 W
W
R13
20 kW
R8
1 kW
C7
470 pF
USD1120
R7
22 W
T1
(Note 2)
D6
USD945
L1
(Note 2)
R9
68
3 W
W
C4
47 µF
25 V
C3
22 µF
C2
100 µF
25 V
R5
150 kW
C14
100 pF
R6
10 kW
C6
.0022 µF
C5
.01 µF
D2
1N3612
D3
1N3612
NC
UC2843A
1
2
3
4
5
6
7
8
D7
USF1002
UC2843A-Q1
SGLS384 – MAY 2008 ........................................................................................................................................................................................................
www.ti.com
Figure 8. Slope Compression
Figure 9. Off-Line Flyback Regulator
8 Submit Documentation Feedback Copyright © 2008, Texas Instruments Incorporated
Product Folder Link(s): UC2843A-Q1