AND8098/D

http://onsemi.com

8

Figure 10. 12V / 100mA Buck Performance

OUTPUT CURRENT (mA)

150

10

50

4

350

0

0

14

2

6

8

250

200

100

12

300

OUTPUT CURRENT (mA)

150

50

50

20

300

0

0

80

10

30

40

250

200

100

60

70

(a) Load Regulation

(b) Efficiency

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

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 5.1k

Ω 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 11. Dual Output Buck-boost

Universal

AC Input

GND

1N4005

10

µF

1N4005 1N4746

MUR160

5.1k

MUR160

MUR160

22

µF

1

µF

150

µF

220

µF

-24V / 200mA

-5V / 150mA

1.2mH / 92.3

µH

NCP1055P100