UM10564 datasheet(8/21 Pages) PHILIPS

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UM10564

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User manual

Rev. 1 — 20 August 2012

8 of 21

NXP Semiconductors

UM10564

UBA2017DB1064 2 x 28 W T5 demo board

5.2.5 Electrode/filament heating

A winding coupled to the main LC tank inductor heats each electrode. The peak of the

transfer is at 90 kHz. The components Cfil and Lfil set this peak frequency. The resonance

frequency of the electrode circuit (Cfil, Lfil and electrode resistance) determines this peak

frequency. The UBA2017 sets the preheat frequency at 90 kHz.

There are several advantages to this type of heating circuit:

• During the preheat phase, there is enough energy to allow preheat times below 1

second.

• During the ignition phase, the load of the electrode resistance is small because of the

2nd order roll off the Cfil and Lfil filter. This feature increases the Q of the LC tank

enabling either:

– a higher ignition voltage to be achieved

– the use of a smaller resonance inductor

• During normal operation, the electrode current is small at 45 kHz because of the 2nd

order roll off from the Cfil and Lfil filter. This results in a lower Sum of Squares and

higher ballast efficiency.

(1) C1 = Vbus.

(2) C2 = VCPT.

(3) C3 = IT2A.

(4) C4 = Vlamp(connector)

Fig 7.

Open lamp ignition

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