UBA2016AP datasheet(12/42 Pages) PHILIPS

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UBA2016A_15_15A

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Objective data sheet

Rev. 1 — 20 May 2011

12 of 42

NXP Semiconductors

UBA2016A/15/15A

600 V fluorescent lamp driver

7.4.1 Reset

When voltage on pin VDD is below the reset voltage Vrst(VDD), both gates of the half-bridge

driver are LOW. All internal latches are reset. When voltage on pin VDD rises above

Vrst(VDD), the IC will enter STANDBY state.

7.4.2 Standby

In STANDBY state the low-side gate driver is on (GLHB is HIGH).The floating supply

capacitor CFSHB is then charged. When the VDD voltage rises above Vstartup(VDD), the

Preheat state is entered.

7.4.3 Oscillating states (Preheat, Ignition and Burn)

The highest and lowest oscillation frequency can be set with capacitor CCF connected to

the CF pin. The oscillator is implemented in such a way that the lowest frequency fsw(low) is

the most accurate. In any oscillating state (Preheat, Ignition or Burn), when VDD voltage

drops below Vstop(VDD) or overtemperature is detected, the half-bridge stops oscillation

when GLHB is HIGH and enters the STANDBY state.

7.4.4 Preheat

The oscillating frequency starts at fsw(high) (see Figure 10 “Resonance curve application

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

remains at that frequency until the PFC output is sufficient (the voltage at pin FBPFC rises

above the PFC voltage OK threshold voltage on pin FBPFC, Vth(VPFCok)FBPFC) and the

voltages at pins CPT and VFB settle above their pin short protection levels

(VVFB > Vth(osp)(VFB) and VCPT > Vth(scp)(CPT)). The half-bridge current is regulated when in

the Preheat state; see Figure 10 “Resonance curve application with UBA2015A” or Figure

11 “Resonance curve application with UBA2016A” point B. Pin CIFB supplies a current

Ich(CIFB) to the externally connected compensation network on this pin and its voltage will

rise. This will cause the switching frequency to decrease (pin CIFB is the input for the

voltage controlled oscillator). This will cause an increase in half-bridge current (assuming

the switching frequency is higher than the load resonance frequency). This current is

measured via pin SLHB using a resistor connected between the source of the low-side

switch and ground. When the voltage on pin SLHB rises above the preheat current control

voltage Vcrtl(ph)SLHB, discharge current Idch(CIFB) to pin CIFB and the frequency is

increased. When the voltage drops below Vth(ocp)SLHB, current Ich(CIFB) from pin CIFB

causes the frequency to decrease.

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