UBA2021_4

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 04 — 25 July 2008

4 of 16

NXP Semiconductors

UBA2021

630 V driver IC for CFL and TL lamps

7.2 Initial start-up

Initial start-up is achieved by charging capacitor CS9 with the current applied to the

the voltage level on the VS-pin at which the circuit will be reset to its initial state and

reset to the start-up state.

7.3 Oscillation

oscillating in the preheat state. The internal oscillator is a current-controlled circuit which

generates a sawtooth waveform. The frequency of the sawtooth is determined by the

frequency is twice the frequency of the signal across the load. The IC brings MOSFETs

T1 and T2 alternately into conduction with a duty factor of approximately 50 %. Figure 4

represents the timing of the IC. The circuit block 'non-overlap' generates a non-overlap

7.4 Operation in the preheat mode

The circuit starts oscillating at approximately 2.5

× f

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

which means that the lamp is off, the load only consists of L2, C5 and the electrode

the preheat state by connecting the CP-pin to ground. During preheating, the circuit

the end of

Fig 4.

Oscillator timing

mgs991

0

0

0

0

time

start-up

internal

clock