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UBA2015AP 数据表(PDF) 23 Page - NXP Semiconductors |
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UBA2015AP 数据表(HTML) 23 Page - NXP Semiconductors |
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23 / 42 page ![]() UBA2016A_15_15A All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved. Objective data sheet Rev. 1 — 20 May 2011 23 of 42 NXP Semiconductors UBA2016A/15/15A 600 V fluorescent lamp driver timer is no longer detected for a period longer than the fault release delay time td(rel)fault, the fault timer will be reset and at any new occurance of the fault, the timer will start from zero. Faults which activate the fault timer are shown as SlowFault in Figure 9 “State diagram”. The fault timer uses the same pin (CPT) to set the time with an external capacitor Cext(CPT) as the preheat timer. The ratio between the preheat time-out time tto(ph) and the fault time-out time tto(fault) can be changed by adding an external series resistor Rs(ext)(CPT) or an external parallel resistor Rp(ext)(CPT) to the external capacitor Cext(CPT); see Figure 15 “CPT connections”. The fault timer incorporates a protection that ensures safe operation conditions if the CPT pin voltage is below Vth(scp)(CPT) (shorted to GND) by holding the oscillation frequency at fsw(high). 7.6.12 Brownout protection Brownout protection is designed to maintain stable and safe lamp operation during dips in mains supply. Without this protection the current demand from the bus voltage to maintain constant lamp power would increase upon a drop in bus voltage. This creates an unstable situation with the mains input voltage dropping and the PFC reaching its regulation range limit. Brownout protection reduces the lamp power when the PFC is out of regulation. This situation is only allowed for a limited time to prevent excessive component stress. When the PFC is outside its regulation range and the bus voltage is still too low (VCOMPPFC =Vclamp(COMPPFC) and VFBPFC <Vreg(FBPFC)), a brownout current Ibo(CF) is added to the charge current at pin CF, thus increasing the fsw(low). A discharge brownout current Idch(bo)(CIFB) is also drawn from pin CIFB. Both Ibo(CF) and Idch(bo)(CIFB) are proportional to the difference between VFBPFC and Vreg(FBPFC). If VFBPFC <Vth(bo)(FBPFC) the fault timer will start. The start-up bleeder resistor and the regulation range of the PFC should be dimensioned in such a way that if the fault timer times out on brownout protection and the IC enters Stop state, the input mains voltage is too low to support the standby current of the IC via the bleeder resistor. The IC will then automatically reset and start-up in normal mode (and reignite the lamps) when the mains voltage has returned to normal. Fig 15. CPT connections 001aan210 Cext(CPT) Rp(ext)(CPT) Rs(ext)(CPT) CPT Cext(CPT) CPT Cext(CPT) CPT smaller ratio default ratio larger ratio tto(ph)/tto(fault) tto(ph)/tto(fault) tto(ph)/tto(fault) |
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