AND8098 Datasheet, PDF(6/10 Page) ON Semiconductor – Low-Cost 100 mA High-Voltage Buck and Buck-Boost Using NCP1052

English

English German Russian Spanish Italian Polish Chinese Japanese Korean French Portuguese	Language :

AND8098 Datasheet, PDF (6/10 Pages) ON Semiconductor – Low-Cost 100 mA High-Voltage Buck and Buck-Boost Using NCP1052

◁

AND8098/D

The proposed buck-boost is better in term of the standby

ability. It is because the VCC charging current in Figure 2(b)

only passes through the inductor. The charging current

pulses become an averaged energy stored in the inductor and

consume smaller amount of power comparing to the buck

case.

fault mode with the 4.5 V-8.5 V-7.5 V-4.5 V hysteresis

loop.

Another method to supply the VCC voltage is coupling

capacitor technique in Figure 8. The output voltage is

coupled to the inserted capacitor when the diodes are closed.

The voltage drop of the diodes compensate each other.

Hence, the diode voltage drop effect can be neglected. The

NCP1052 needs a nominal VCC voltage of 8V. The inserted

resistor consumes some voltage from the output voltage Vout

to make a 8V to the VCC pin. Based on the 0.5mA typical

current consumption of VCC pin. The inserted resistance

value is (Vout - 8) / 0.5 kW.

(a) Buck

(b) Buck-boost

Figure 7. Auxiliary Winding to improve standby

Abillity

The auxiliary winding to supply the VCC voltage in Figure

7 is a method to improve the standby ability. The auxiliary

winding keeps the VCC voltage above 7.5 V and disable the

VCC charging current and hence its standby loss. The

auxiliary winding is coupled from the inductor L with

polarity same as the regulated output voltage. The VCC

voltage in the auxiliary winding is designed to be between

the normal VCC limits of 7.5 and 8.5 V typically. The

frequency jittering feature loses when the VCC voltage is

fixed. When output is shorted, there will be no voltage

coming from the auxiliary winding and the circuit will enter

(b) Buck-boost

Figure 8. Coupling Capacitor Technique to

Improve Standby Abillity

Temperature Rise

The NCP1052 is a very compact package with the control

circuit and high-voltage power switch. Its typical on

resistance is 22 â¦. Temperature rise exists. It is

recommended to design the PCB board with a large copper

area next to the device as a heatsink. This heatsink decreases

http://onsemi.com

▷