AND8098/D
14
12
OUTPUT VOLTAGE (V)
10
8
6
4
2
0
0
50
100
150
200
250
300
350
OUTPUT CURRENT (mA)
(a) Load Regulation
80
70
60
EFFICIENCY (%)
50
40
30
20
10
0
0
50
100
150
200
250
300
OUTPUT CURRENT (mA)
(b) Efficiency
V
IN
= 200 Vdc
V
IN
= 300 Vdc
V
IN
= 100 Vdc
V
IN
= 100 Vdc
V
IN
= 300 Vdc
V
IN
= 200 Vdc
Dual Output Buck-boost with Increased Output
Current Capability
Replacing NCP1052 by NCP1055, which is with a current
limit of 680 mA, the output current capability is increased.
Larger value of inductor L is selected for high current. On
the other hand, the current consumption of NCP1055 is
higher than NCP1052 and the startup transient time is longer
in a higher power application. Hence, the V
CC
capacitor is
increased. When the V
CC
capacitor increased, its charging
frequency is decreased. Output capacitor is also needed to be
increased to reduce this lower-frequency charging current/
ripple.
In addition, by adding one more auxiliary winding to the
inductor a secondary output is made. A typical example is
shown in Figure 11. In higher output current application, the
load regulation is the major problem. The 5.1kΩ resistor
plays an important role for the load regulation. The primary
output voltage is higher than the secondary because it can
increase the output current ability by stepping up the current
in the transformer. The line regulation is shown in Figure 12
when the output currents are constant.
Figure 10. 12V / 100mA Buck Performance
1N4005 1N4746
MUR160
5.1k
NCP1055P100
1N4005
1µF
MUR160
-24V / 200mA
22µF
Universal
AC Input
10µF
150µF
GND
1.2mH / 92.3µH
220µF
MUR160
-5V / 150mA
Figure 11. Dual Output Buck-boost
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