UBA2025T データシートの表示（PDF） - NXP Semiconductors.

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UBA2025T

CFL power IC

NXP Semiconductors. 

NXP Semiconductors

UBA2025

CFL power IC

capacitor connected to pin CI. The frequency during preheating will be approximately

90 kHz. This frequency is well above the resonant frequency of the load, which means

that the lamp is off. The load consists of L2, C5 and the electrode resistance only

(see Figure 6). The preheat time is determined by the capacitor connected to pin CPAV.

The circuit can be locked in the preheat state by connecting pin CPAV to ground. During

preheating the circuit monitors the load current by measuring the voltage drop over

external resistor RSHUNT at the end of conduction of T2 with decision level Vshunt. The

frequency is decreased as long as VRS > Vshunt. The frequency is increased for

VRS < Vshunt.

fstart

fbtm

preheat state

Fig 4. Operation in preheat mode

ignition

state

burn state

time

mgs992

7.5 Ignition state

The RS current monitoring function changes from Vshunt regulation to capacitive mode

protection at the end of the preheat time. Normally this results in a further frequency

decrease down to the bottom frequency fbtm (approximately 43 kHz). The frequency

change per ms is lowered with respect to the frequency change in the preheat mode.

During the downward frequency sweep the circuit sweeps through the resonant frequency

of the load. A high voltage will then appear across the lamp. This voltage will normally

ignite the lamp.

7.6 Failure to ignite

Excessive current levels may occur when the lamp fails to ignite. The IC does not limit

these currents in any manner.

7.7 Transition to the burn state

Assuming that the lamp has ignited during the downward frequency sweep, the frequency

normally decreases to the bottom frequency. The IC can transit to the burn state in two

ways:

• In the event that the bottom frequency is not reached, the transition is made after

reaching the ignition time tign.

• As soon as the bottom frequency is reached.

The bottom frequency is determined by resistor RIREF and capacitor CF.

UBA2025_1

Product data sheet

Rev. 01 — 16 October 2009

© NXP B.V. 2009. All rights reserved.

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