AND8098 Datasheet, PDF (8/10 Pages) ON Semiconductor – Low-Cost 100 mA High-Voltage Buck and Buck-Boost Using NCP1052

AND8098/D
14
12
10
8
6
4
V_IN = 100 Vdc
V_IN = 300 Vdc
2
V_IN = 200 Vdc
0
0
50 100 150 200 250 300 350
OUTPUT CURRENT (mA)
(a) Load Regulation
80
70
V_IN = 100 Vdc
60
50
V_IN = 200 Vdc
V_IN = 300 Vdc
40
30
20
10
0
0
50
100
150
200
250
300
OUTPUT CURRENT (mA)
(b) Efficiency
Figure 10. 12V / 100mA Buck Performance
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.
1N4005 1N4746
MUR160
5.1k
NCP1055P100
1N4005
1µF
MUR160
-24V / 200mA
Universal
AC Input
10µF
22µF
1.2mH / 92.3µH
MUR160
Figure 11. Dual Output Buck-boost
150µF
GND
220µF
-5V / 150mA
http://onsemi.com
8