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

部品番号

コンポーネント説明

メーカー

UBA2025T

CFL power IC

NXP Semiconductors. 

NXP Semiconductors

UBA2025

CFL power IC

7. Functional description

7.1 Introduction

The IC is an integrated circuit for electronically ballasted compact fluorescent lamps and

its derivatives, up to a nominal mains voltage of 230 V (RMS). It provides all the

necessary functions for proper preheat, ignition and on-state operation of the lamp.

Besides the control function, the IC provides the level shift and drive for the two internal

power MOSFETs.

7.2 Initial start-up

Initial start-up is achieved by charging CS9 (see Figure 6) with the current applied to

pin RHV. The start-up of the circuit is such that (see Figure 1) T2 shall be conductive and

T1 shall be non-conductive, in order to make sure that CBOOT gets charged. This start-up

state is reached for a supply voltage Vrst, this is the voltage level at pin VS at which the

circuit will be reset to the initial state and maintained until the low voltage supply (VVS)

reaches a value of Vstartup.

7.3 Oscillation

If the low voltage supply (VVS) has reached the value of Vstartup the circuit starts 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 capacitor CF and

the current out of pin CF (mainly set by RIREF). The sawtooth frequency is twice the

frequency of the signal across the load. The IC brings alternately the power MOSFETs

T1 and T2 into conduction with a duty cycle of approximately 50%. Figure 3 represents

the timing of the IC. The circuit block 'non-overlap' generates a non-overlap time tno when

T1 and T2 are not conducting. This is dependent on the reference current.

VCF

0

internal

clock

0

start-up

V(GT1-S1)

0

V(GT2)

tno

0

Fig 3. Oscillator timing

tno

time

mgs991

7.4 Operation in preheat mode

The circuit starts oscillating at a frequency of approximately 2.5fbtm (108 kHz). The

frequency will gradually decrease until a defined value of the current through RSHUNT is

reached (see Figure 4). The slope of the decrease in frequency is determined by the

UBA2025_1

Product data sheet

Rev. 01 — 16 October 2009

© NXP B.V. 2009. All rights reserved.

4 of 17

Share Link: