AN11187 UBA2015/UBA2017 saturating inductor support during ignition Rev. 1 — 16 August 2012 Application note Document information Info Content Keywords UBA2015, UBA2017, saturating resonant tank inductor support Abstract This application note describes how to use a UBA2015/UBA2017 or in combination with a resonant tank inductor that saturates during lamp ignition. This application note also applies to the UBA2017 half-bridge controller IC without a PFC. AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition Revision history Rev Date Description v.1 20120816 first issue Contact information For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: [email protected] AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 2 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition 1. Introduction This application note describes how to use a UBA2015/UBA2017 in combination with a resonant tank inductor that saturates during lamp ignition. The ignition voltage Vign is applied to the lamp for time tign to ignite a fluorescent lamp. The Vign voltage is much higher than the nominal operating voltage of the lamp. Most lamp ballasts apply an open lamp voltage to the lamp connector during the ignition state. The open lamp voltage is applied for between 100 ms and 200 ms to ensure old and cold lamps ignite. Some lamp ballasts use a saturating inductor during the ignition state to reduce the size and cost of this inductor. The UBA2015/UBA2017 circuitry only supports saturation protection. The IC reduces the on-time of the low-side half-bridge transistor when the inductor saturates. However, the high voltage is not maintained over the total programmable ignition time-out period. The UBA2015/UBA2017 can also be used to control inductor saturation during the ignition time-out period. The saturation is controlled during the programmable ignition time-out period. This function requires an extra circuit that connects to the CF pin capacitor. This extra circuit is explained in this application note. Remark: Unless otherwise stated, all voltages are typical values. 1.1 Features • Operating the resonant tank inductor in saturation • Regulation is adjustable for several saturation levels 2. Circuit Diagram DDD Fig 1. Circuit to support inductor saturation AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 3 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition The additional parts for inductor saturation regulation are: DCF, D1, D2, RCF, Rsense(QLHB) and Csense(QLHB). To reduce the sense resistor values, Schottky diodes can be used on positions D1 and D2. 2.1 Extended Bill of Materials Table 1. Extended Bill of Materials Part reference Description CCF UBA2015/UBA2017 oscillator frequency setting CDC DC blocking capacitor Cdiv capacitive lamp voltage divider Csense(QLHB) filter capacitor to remove hard switching spikes Cres resonance capacitor D1 increases VCF when the L1A inductor saturates and QHHB is on D2 increases VCF when the L1A inductor saturates and QLHB is on DCF CF pin protection against negative voltages DVFB clamping diode to ground L1A resonant tank inductor L1B; L1C inductor L1 windings for heating the filaments RCF provide impedance to lift VCF RGHHB; RGLHB MOSFET gate damping resistors Rsense(QHHB) inductor current sense resistor when QHHB is on Rsense(QLHB) inductor current sense resistor when QLHB is on RVFB1; RVFB2 resistor divider VFB pin voltage RVFB3 VFB pin voltage offset 3. Operation and Performance At the end of the preheat state, the half-bridge frequency is swept down by increasing the voltage on the VCO input (pin CIFB). The current in the inductor increases during the sweep and the inductor starts to saturate. Figure 2 shows the first ignition attempt and a small part of the second and final ignition attempt. The resonance capacitor Cres integrates the current waveform to generate the ignition voltage. Figure 2 shows the CF pin voltage on channel C4. When saturation pulses are present, the CF pin voltage is increased because of the signal injected by diodes D1 or D2. Each time the CF pin reaches 2.5 V, the active MOSFET is switched off. AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 4 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition (1) C1=VCres. (1) C2 = VCPT. (1) C3 = IL1A. (1) C4 = VCF. Fig 2. First ignition attempt: lamp voltage, inductor current, CPT timer, CF pin voltage Figure 2 shows the fault timer counting on channel C2. The VFB pin activates counting and is necessary to shut down the ballast in case no lamp is present. The fault timer is activated using the VFB pin under the following circumstances: • In the ignition state: when the VFB voltage is > Vth(ov)(VFB) = 2.5 V and < Vth(ovextra)(VFB) = 3.35 V. • In burn state after flow detection = VCIFB = 3.0 V: when the VFB voltage > Vth(oveol)(VFB) > 880 mV (DIM pin left open, UBA2015A only) and < Vth(ovextra)(VFB) = 3.35 V In addition, the voltage feedback stabilizes the voltage increase on the CIFB pin. Figure 3 shows the CIFB pin voltage on channel 4. The CIFB voltage sets the operating frequency. However during saturation, the operating frequency is higher than set because the MOSFET on-time is reduced by triggering the CF threshold voltage Vth(CF) at 2.5 volts. AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 5 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition (1) C1=VCres. (2) C2 = VCPT. (3) C3 = IL1A. (4) C4 = VCIFB. Fig 3. First ignition attempt: lamp voltage, inductor current, CPT timer, CIFB pin voltage 4. Step-by-step guide The goal is to set the sense resistors for the correct open lamp voltage during an open lamp test. 1. Start with sense resistors Rsense(QHHB) and Rsense(QLHB) at 1 . Keep Rsense(QHHB) equal to Rsense(QLHB)). 2. Measure the open lamp voltage during ignition. 3. If the open lamp voltage is too low, reduce the value of Rsense(QHHB) and Rsense(QLHB). Then go to step 2. 4. If the open lamp voltage is too high, increase the value of Rsense(QHHB) and Rsense(QLHB). Then go to step 2. 5. Open lamp voltage is ok, Rsense(QHHB) and Rsense(QLHB). are correct. AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 6 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition 5. Simplified circuit It is possible to operate a saturating inductor with a smaller circuit for some ballast (large CIFB capacitor, non-dimmable). Remark: Test only using Rsense(QLHB) for inductor saturation regulation, do not mount Rsense(QHHB), D1 or DCF. The Rsense(QLHB) value obtained is higher compared to Figure 1. aaa-004406 Fig 4. Simplified circuit to support inductor saturation AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 7 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition 6. Star ground configuration The UBA2015/UBA2017 is subjected to large disturbances because of the high peak current during saturation. These disturbances are caused when the half-bridge switching node has commuted to the bus voltage Vbus. Place the star ground near the GND pin (15) of the UBA2015 to minimize the common impedance of the ground tracks. Route the bus voltage next to the ground between the bus capacitor C11 and half-bridge MOSFETs to minimize the magnetic field of the high di/dt signal. AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 8 of 12 xxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx x xxxxxxxxxxxxxx xxxxxxxxxx xxx xxxxxx xxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxx xxxxx xxxxxx xx xxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxx xxxxxxx xxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxx xxxxxxxxxxxxxx xxxxxx xx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxxxx xxxxxxx xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxx xxxxx x x NXP Semiconductors AN11187 Application note & & 5 5 5 ' ' & ' & 9EXV 4 6/+% /% /$ ,)% (2/ 9)% ,5() &,)% &) &37 QF 3+(1 5 & & 8 8%$ 4 5 5 & 5 5 /$03 *++% )6+% 6++% */+% 9'' *1' *3)& & & ' & & /& & ,& 5 67$5*5281' 3)& ' 5 ' ,& +% Star ground example to indicate board layout set-up 5 & DDD AN11187 9 of 12 © NXP B.V. 2012. All rights reserved. Fig 5. 5 5 & 5 4 $8;3)& & )%3)& 5 &203)& ' & UBA2015/UBA2017 saturating inductor support during ignition Rev. 1 — 16 August 2012 All information provided in this document is subject to legal disclaimers. & 5 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition 7. References [1] UBA2016A/15/15A — 600 V fluorescent lamp driver with PFC, linear dimming and boost function [2] UBA2017/UBA2017A — 600 V fluorescent lamp driver with linear dimming function [3] AN10958 — Fluorescent lamp driver with PFC using the UBA2015/16 family [4] UM10359 — UBA2016AT demo board 1 28 W dim and boost [5] UM10438 — UBA2015AP evaluation board 1 35 W T5 dimmable 120 V (AC) [6] UM10440 — UBA2015AT reference design 2 35 W T5 dimmable 230 V (AC) [7] UM10466 — UBA2015P reference design 2 35 W T5 non-dimmable 230 V (AC) [8] UM10486 — UBA2015P reference design 2 35 W T5 non-dimmable 120 V (AC) [9] UM10561 — UBA2017AT reference design for 420 V (DC) [10] UM10564 — UBA2017DB1064 2 x 28 W T5 demo board AN11187 Application note All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 10 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition 8. 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Customers are responsible for the design and operation of their applications and products using NXP Semiconductors products, and NXP Semiconductors accepts no liability for any assistance with applications or customer product AN11187 Application note design. It is customer’s sole responsibility to determine whether the NXP Semiconductors product is suitable and fit for the customer’s applications and products planned, as well as for the planned application and use of customer’s third party customer(s). Customers should provide appropriate design and operating safeguards to minimize the risks associated with their applications and products. NXP Semiconductors does not accept any liability related to any default, damage, costs or problem which is based on any weakness or default in the customer’s applications or products, or the application or use by customer’s third party customer(s). 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Notwithstanding any damages that customer might incur for any reason whatsoever (including without limitation, all damages referenced above and all direct or general damages), the entire liability of NXP Semiconductors, its affiliates and their suppliers and customer’s exclusive remedy for all of the foregoing shall be limited to actual damages incurred by customer based on reasonable reliance up to the greater of the amount actually paid by customer for the product or five dollars (US$5.00). The foregoing limitations, exclusions and disclaimers shall apply to the maximum extent permitted by applicable law, even if any remedy fails of its essential purpose. Translations — A non-English (translated) version of a document is for reference only. The English version shall prevail in case of any discrepancy between the translated and English versions. 8.3 Trademarks Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. All information provided in this document is subject to legal disclaimers. Rev. 1 — 16 August 2012 © NXP B.V. 2012. All rights reserved. 11 of 12 AN11187 NXP Semiconductors UBA2015/UBA2017 saturating inductor support during ignition 9. Contents 1 1.1 2 2.1 3 4 5 6 7 8 8.1 8.2 8.3 9 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Circuit Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 3 Extended Bill of Materials . . . . . . . . . . . . . . . . . 4 Operation and Performance . . . . . . . . . . . . . . . 4 Step-by-step guide. . . . . . . . . . . . . . . . . . . . . . . 6 Simplified circuit . . . . . . . . . . . . . . . . . . . . . . . . 7 Star ground configuration. . . . . . . . . . . . . . . . . 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Legal information. . . . . . . . . . . . . . . . . . . . . . . 11 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Please be aware that important notices concerning this document and the product(s) described herein, have been included in section ‘Legal information’. © NXP B.V. 2012. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: [email protected] Date of release: 16 August 2012 Document identifier: AN11187