AND8098/D

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6

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

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.

Figure 7. Auxiliary Winding to improve standby

Abillity

(a) Buck

(b) Buck-boost

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

auxiliary winding is coupled from the inductor L with

voltage in the auxiliary winding is designed to be between

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

coming from the auxiliary winding and the circuit will enter

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

loop.

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

W.

Figure 8. Coupling Capacitor Technique to

Improve Standby Abillity

(a) Buck

(b) Buck-boost

Temperature Rise

The NCP1052 is a very compact package with the control

circuit and high-voltage power switch. Its typical on

resistance is 22

Ω. 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