UBA2015AP datasheet(14/42 Pages) PHILIPS

14 / 42 page

UBA2016A_15_15A

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Objective data sheet

Rev. 1 — 20 May 2011

14 of 42

NXP Semiconductors

UBA2016A/15/15A

600 V fluorescent lamp driver

The preheat frequency for UBA2015 and UBA2015A can also be regulated via pin PH/EN.

UBA2015 and UBA2015A support current controlled preheat and fixed frequency preheat.

During preheat the output voltage of pin PH/EN is Vph(PH/EN). The output current that an

external resistor Rext(PH/EN) connected to this pin sinks is compared to 4⁄5 of the output

current of the VCO (the current at pin CF with no fault condition present and the capacitor

at that pin being charged minus the same current at fsw(low)). As long as the output current

of the VCO is bigger the frequency is being decreased (by charging pin CIFB with

Ich(CIFB)). If the current through the external resistor is bigger the frequency will be

increased (by discharging pin CIFB with Idch(CIFB)).

Current and fixed frequency control mechanisms are active at the same time. For fixed

frequency preheat using pin PH/EN, the half-bridge current sense resistor connected to

pin SLHB should be small enough not the activate the current control mechanism. If

current controlled preheat is used, pin PH/EN should be left open (except of course for the

open collector or open drain that drives the enable function). The preheat time tto(ph) can

be set with capacitor CCPT on pin CPT.

7.4.5 Ignition

After the Preheat state the IC enters the Ignition state. During the Ignition state the

switching frequency is decreased by charging pin CIFB with Ich(CIFB). This will result in

increasing lamp voltage until the lamp ignites (see point C in Figure 10 “Resonance curve

application with UBA2015A” or Figure 11 “Resonance curve application with UBA2016A”)

and lamp-on or fsw(low) (lowest frequency) is detected. Lamp-on detection occurs when the

average absolute voltage on pin IFB is above lamp-on detection threshold Vth(lod)(IFB) and

the voltage on pin VFB is more then 50 % of each clock cycle below the lamp-on detection

threshold Vth(lod)(VFB) and after a delay td(lod).

If either saturation, overvoltage or hard switching regulation (UBA2016A only) is triggered

it will overrule the frequency sweep down and hold the frequency at the border where the

fault appeared and start the fault timer. When the fault timeout tto(fault) is reached the IC

enters Auto-restart state if it was the first ignition attempt, otherwise it will go to the Stop

state; see Figure 9 “State diagram”.

7.4.6 Auto-restart

The Auto-restart state is entered after a fault time out in the Ignition state during the first

ignition attempt. See Figure 9 “State diagram”. When the IC is in Auto-restart state, it

draws supply current Irestart(VDD). This will slowly discharge the buffer capacitor on pin

VDD until the voltage on this pin drops below Vrestart(VDD). The IC then enters the Standby

state. Here the VDD capacitor will be charged again to start a second ignition attempt. The

bleeder current must be between standby current Istb(VDD) and Irestart(VDD). A time delay

can be set between the two ignition attempts with the capacitor at pin VDD to reduce

stress on the HB components.

7.4.7 Burn

In Burn state the lamp current regulation and all protection circuits are active. The boost

function (available in UBA2016A only) is also enabled.

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