AN10713 UBA2024 UBA2024A UBA2024T/AT UBA2024/UBA2024A UBA2024P UBA2024T F/200 - Datasheet Archive

 

18 W CFL lamp design using UBA2024 application development tool and application examples Rev. 02 - 10 October 2009 Application

 

AN10713 AN10713 18 W CFL lamp design using UBA2024 UBA2024 application development tool and application examples Rev. 02 - 10 October 2009 Application note Document information Info Content Keywords UBA2024 UBA2024, CFL, CCFL, Integrated half-bridge driver and integrated switches, lighting Abstract Application note for the NXP UBA2024 UBA2024 and UBA2024A UBA2024A CFL driver AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Revision history Rev Date Description 02 20091010 Second issue. Modifications: · · · · · · 01 20090722 Section 1.2 "System benefits" updated. Section 3 "Design of an 18 W non-dimmable CFL" introduction updated. Section 3.2 "Choosing frequency, lamp inductor and capacitor" updated. Section 3.2 "Choosing frequency, lamp inductor and capacitor" figures updated. Figure 15 "Photo reference board UBA2024T/AT UBA2024T/AT (230 V (AC) version)" added. Section 7.4 "UBA2024 UBA2024 in a replaceable lamp configuration (match box ballast)" updated. First issue Contact information For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 2 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 1. Introduction The UBA2024 UBA2024 is an integrated half-bridge power IC, designed for use in an integrated/sealed Compact Fluorescent Lamp (CFL) with lamp powers of up to 22 W. Typical input voltages are 100 V (AC) to 127 V (AC) and 220 V (AC) to 240 V (AC). This application note describes typical integrated CFL applications in the 3 W to 18 W range, depending on lamp and input voltage. The term lamp is used when the burner and electronic ballast are meant. The UBA2024 UBA2024 includes both half-bridge power transistors with a level-shifter and drivers, bootstrap circuitry, an internal power supply, a precision oscillator and a start-up frequency sweep function for soft start and/or quasi-preheating. There are two versions of the UBA2024 UBA2024, the UBA2024 UBA2024, specified for (total) lamp powers of up to 15 W and the UBA2024A UBA2024A is intended for lamp powers that are above 15 W. The maximum lamp power depends on the lamp design and the dissipation of the IC. In this application note a non-dimmable 18 W application is presented. The UBA2024/UBA2024A UBA2024/UBA2024A is available as a DIP8 package (extension letter P after type code) and an SO14 package (extension letter T after type code). This document will mainly describe the DIP package, but the same can be applied to the UBA2024 UBA2024 in SO14 package. Due to the high level of integration, only a few external components are needed in a lamp ballast with the UBA2024 UBA2024. 1.1 Features · · · · Integrated half-bridge power-IC for CFL applications (both power and controller) Accurate oscillator with adjustable frequency Soft-start by frequency sweep down from start frequency Quasi preheat option (programmable sweep down timing) 1.2 System benefits · · · · · · · Allows for very compact integrated lamp ballast which fits a small shell Low cost CFL applications due to low component count Higher reliability due to low component count Longer lamp life due to quasi preheat Easy applicable Based on EZ-HV SOI (silicon on insulator) technology Can withstand a maximum voltage of 550 V AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 3 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 2. Circuit diagram Figure 1 shows the typical circuit diagram of the UBA2024 UBA2024. Figure 2 shows a version with a voltage doubler for use in 120 V (AC) applications. The voltage doubler is needed for medium and high powers in regions that have lower mains voltages. U1 LFILT 1 2 6 HV VDD 7 2 CFL ROSC 1 D1 D3 3 CHB1 K1 2 1 RFUS 1 2 2 CBUF LLA 1 2 D2 1 1 D4 RC 1 8 1 COSC CFS + 1 FS 1 2 3 1 2 2 2 5 4 OUT SW 1 1 C VDD 2 CHB2 1 CDV CLA 2 UBA2024P UBA2024P 1 4 PGND SGND 2 2 Fig 1. 2 Typical application diagram U1 LFILT 1 2 K1 2 1 RFUS 1 2 2 6 R9 1 M 2 + 2 D2 CBUF1 3 1 2 3 2 4 1 LLA 2 2 FS RC ROSC 8 1 UBA2024P UBA2024P Cfs 1 1 R10 1 M + 2 7 2 CHB1 5 OUT SW 1 COSC 1 2 1 1 CHB2 CBUF2 1 VDD 1 1 CON2 HV CFL 1 D1 Fig 2. 2 CSW 2 2 CLA 1 4 CDV 1 1 PGND SGND CVDD CSW 2 2 2 2 Typical application diagram with voltage doubler See the UBA2024 UBA2024 data sheet for a functional description. 3. Design of an 18 W non-dimmable CFL An application development tool has been made available to simplify the design of the lamp and the calculation of the resonance circuit. This chapter explains the selection criteria for the component values. It also clarifies how to feed the application development tool with the appropriate values for components. With the tool and with the help of some practical guidelines it should be easy to set up designs for different lamp powers. Throughout this document the light source itself is called the burner. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 4 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 3.1 Selecting input configuration, buffer capacitor and fuse-resistor Table 1 shows the values for the input section of the standard 230 V (AC) version and the 120 V (AC) version with and without a voltage doubler. Table 1. Advised input configuration Input voltage Driver IC Lamp power[1] Input CBUF1 configuration 100 V (AC) to 127 V (AC) UBA2024P UBA2024P 4W Standard UBA2024T UBA2024T 5 W to 6 W CBUF1, CBUF2 Fusistor[2] 10 F/200 F/200 V n.a. 18 /(0.25 W/23 W) 15 F/200 F/200 V n.a. 12 /(0.5 W/35 W) n.a. 10 F/200 F/200 V 10 /(0.5 W/47 W) n.a. 15 F/200 F/200 V 8.2 /(0.75 W/70 W) 12 W to 14 W n.a. 22 F/200 F/200 V 6.8 /(1 W/103 W) 15 W to 18 W n.a. 22 F/200 F/200 V 6.8 /(1 W/103 W) 2.2 F/400 F/400 V n.a. 47 /(0.25 W/23 W) 3.3 F/400 F/400 V n.a. 39 /(0.25 W/23 W) 9 W to 11 W 4.7 F/400 F/400 V n.a. 33 /(0.5 W/32 W) 12 W to 15 W 6.8 F/400 F/400 V n.a. 27 /(0.5 W/47 W) 15 W to 18 W 6.8 F/400 F/400 V n.a. 15 /(1 W/103 W) 7 W to 8 W 9 W to 11 W UBA2024AP UBA2024AP Voltage doubler UBA2024AT UBA2024AT 220 V (AC) to 240 V (AC) UBA2024P UBA2024P 5W UBA2024T UBA2024T 6 W to 8 W UBA2024AP UBA2024AP Standard UBA2024AT UBA2024AT [1] Overall lamp power including driver circuit [2] Minimum continuous power rating/minimum peak power rating (20 ms). 3.2 Choosing frequency, lamp inductor and capacitor 3.2.1 Input values The application development tool calculates the component values based on the following input parameters: · · · · · · Selection of the driver IC type (UBA2024A UBA2024A type for lamp power > 15 W) Burner power Burner ignition voltage Burner operating voltage Mains input voltage and frequency (typical operating voltage) Combined value of the DC blocking capacitors Figure 3 shows the part of the application development tool where the base values can be entered. The example shows the design of an 18 W lamp. This is the total lamp power, which means 16.8 W burner power and about 1.5 W loss in the electronic ballast. The burner used in this example is a replaceable burner. It is based on a G24q-2 fitting with the following parameters. · Burner power = 16.8 W · Burner voltage = 80 V · Ignition voltage = 600 V AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 5 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 The following actions need to be taken: 1. Enter the burner parameters 2. Select the mains voltage to be used for the 18 W lamp (230 V (AC) 3. Select the IC (in this case the UBA2024AP UBA2024AP, 8-pin DIL version) The UBA2024P UBA2024P cannot be used because the RDSon of its switches is too high. a. Burner parameters b. Mains voltage selection c. IC selection Fig 3. Entering the design parameters for an 18 W lamp For the lamp power given in Figure 3, the minimum value of the combined value of the parallel DC blocking capacitors, CHB1 and CHB2, is advised in Figure 4. For the 16.8 W burner power the advised minimum value is 2 × 68 nF, but 2 × 100 nF was chosen instead. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 6 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Based on the burner parameters mains voltage and frequency, the buffer capacitor listed in Table 1, and selected DC blocking capacitors, a first calculation of the LC resonance tank can be executed by pressing the Calculate button. The application development tool then calculates advisory values for the resonance inductor and capacitor. The default oscillator frequency is set to 42 kHz. After the Calculate button has been pressed for the first time, the actual values in Figure 4 have to be matched with the values in the advised fields on the right. This can be done in the left column (Actual) by entering values for the resonance capacitor and inductor shown in Figure 4. In this design the frequency is adjusted a little higher (45 kHz) to obtain an inductance of 2.1 mH and a capacitance value of 2.2 nF. Fig 4. Calculated advised values of the resonance circuit (blue fields, right) and actual entered values and operating frequency (green fields, left) When choosing the values for the L resonance (LLA) and C resonance (CLA) it is advisable to match the overall lamp power of the entered L and C resonance values with the calculated lamp power of the advised resonance values. See Figure 5 (middle column). Round off the C resonance to the nearest higher value available in the E range and later check in the lamp prototype if the chosen L and C resonances give a clean lamp turn-on as shown in Figure 12. If in the actual prototype the lamp turns on before ignition (the lamp current is already flowing before the ignition of the lamp and the voltage has dropped to a lower level), increase the value of C resonance to lower the ignition frequency, fign, and the lamp voltage during the quasi-preheat period. Ideally, fign should be close to 1.7 times the operating frequency, fout (see Section 3.4). Alternatively, a larger CSW capacitor (longer quasi-preheat time) can be a solution. L resonance is in most cases a custom design and not a standard component. So its value can be made to match closely with the advised value. Since the L mainly determines the lamp current and therefore the lamp power, it is best practice to round off to a higher value for the L resonance rather than to a lower value than advised. This can compensate for a higher line voltage tolerance on the oscillator frequency to preserve lamp life. The effect of line voltage tolerance can be added in the calculation by selecting a different percentage behind the mains voltage in Figure 3. Figure 5 shows the range of power in the lamp for the specified conditions. The values DO NOT indicate the minimum and maximum rectified AC mains voltage, but the minimum and maximum voltages measured with an oscilloscope on pin VHV under load conditions (see Figure 12, channel 2). The values in Figure 5 are based on the entered values shown in Figure 3 and Figure 4. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 7 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Fig 5. Average values (middle column) to set up the design 3.2.2 Calculation plots Figure 6, Figure 7, and Figure 8 are based on the values entered in Figure 3 and Figure 4. Figure 6 shows the most important is graph. This graph shows the lamp power based on the advised calculation (blue) and the lamp power based on the actual values (green) as function of the DC bridge voltage. If the values for LLA and CLA are correct the two lines should coincide. Fig 6. Lamp power versus bridge voltage AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 8 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Figure 7 shows the voltage to current phase shift between the voltage on and the current through the OUT pin of the IC caused by the L and C resonances, Cdv and the lamp. Fig 7. V-I phase shift versus half bridge voltage To guarantee safe operation, care must be taken that the phase shift between the output voltage and the output current is large enough to avoid capacitive mode. To be safe a phase shift lower than -20 ° is advised. The preferred safe operating range is a phase shift between -40 ° and -60 °. Lower phase shifts, lower than -60 °, will cause extra losses in the power FETs as the reactive current does add to the losses in the UBA2024 UBA2024. Figure 8 shows the continuous current through the UBA2024 UBA2024 FETs during normal operation. The RMS current should not exceed 270 mA for the UBA2024A UBA2024A type. Fig 8. FET currents as function of bridge voltage Figure 9 also shows the calculated ignition frequency. The ignition frequency depends on the burner and on the resonance circuit (LLA, CLA, DC-blocking capacitor and the voltage on Vbridge). The ideal ignition frequency for the UBA2024 UBA2024 is at 1.7 times the operating frequency. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 9 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Care must be taken that the ignition frequency is not lower than 1.6 times the operating frequency and not higher than 2.2 times the operating frequency. As the frequency sweep starts at 2.5 times the operating frequency, an ignition frequency that is too high will not give enough time for the quasi-preheat of the burner filaments. A warning will be given on the application development tool if the resonance frequency is outside this range. The application development tool has various built-in checks. It will generate a warning or an error message in the status field when the chosen design values go beyond specification limits of the IC. The status information on the design becomes available when pressing the Status button. When no suitable values for L or C resonances can be found, the operating frequency can be adjusted, so that a new set of values for L and C resonances can be calculated. Real values of available components should be entered in the "Application actual values" section. This can be repeated until a satisfactory solution has been found. For more information on the operating frequency see Section 3.3. 3.2.3 Coil In the section "Coil designs parameters" (example in Figure 9) the most important requirements for the inductor are shown. These together with the inductance entered in Figure 4, and the operating temperature of the inductor should be enough information to design a coil. Due to losses in the inductor the operating temperature of the inductor is higher than the lamp ambient temperature. When the coil is properly designed, the inductor temperature rise will be around 40 °C above the ambient temperature. In case a warm lamp is switched off and on again, the inductor should not saturate at this inductor temperature. Fig 9. Requirements for coil design 3.2.4 Thermal properties In this section the estimated dissipated power and the estimated junction temperature in the IC is calculated. See Figure 10 for an example. When the maximum ambient temperature at which the lamp needs to operate is entered, the expected junction temperature is calculated. The junction temperature must not exceed 150 °C. If the junction temperature does exceed the 150 °C the expected operating life time of the IC is reduced significantly. The maximum stress allowed during the ignition phase is 900 mA (peak) on the UBA2024 UBA2024 and 1.35 A (peak) on the UBA2024A UBA2024A at a case temperature of 25 °C (repetition rate is less than once per hour). The maximum stress period must not be longer than 1 second. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 10 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Fig 10. Dissipated power and expected junction temperature in the IC 3.2.5 Literature reference The formulas behind the calculations in the Excel spreadsheet are based upon: [1] - IEEE publication, An Improved Design Procedure for LCC Resonant Filter of Dimmable Electronic. [2] - Ballasts for Fluorescent Lamps, Based on Lamp Model, Fabio Toshiaki Wakabayashi Carlos Alberto Canesin 2003. 3.3 Operating frequency An operating frequency, fout, of up to 60 kHz (the maximum nominal output frequency for the UBA2024 UBA2024, corresponding with a start-up frequency of 150 kHz. See the data sheet for start-up sequence description) can be selected. However, an fout between 25 kHz and 30 kHz or between 40 kHz and 50 kHz is usually selected. This is because below 25 kHz there may be audible noise. Operation within the 30 kHz to 40 kHz band may result in interference with infrared remote controls. At higher than 50 kHz the third harmonic is in the range where conducted emission requirements for most countries have to be met. Since inductors and capacitors decrease in size and cost with increase in frequency, the 40 kHz to 50 kHz range is preferred. fout is set by ROSC and COSC according to Equation 1: 1 f out = -k OSC × R OSC × C OSC (1) Practical values for ROSC range from 50 k to 400 k. Note that the lower the value of ROSC is the higher the VDD output current is going to be, thus increasing the total package dissipation. Practical values for COSC range from 100 pF to 1 nF. The advised value for COSC is 180 pF for 40 kHz to 50 kHz and 270 pF for 25 kHz to 30 kHz. Figure 11 shows the oscillator constant kOSC. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 11 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Fig 11. Typical kOSC dependency of ROSC and COSC for UBA2024 UBA2024 3.4 Ignition frequency and quasi-preheating The IC output starting frequency is about 2.5 times the nominal output frequency and gradually decreases, depending on lamp type and temperature, until the nominal output frequency is reached. The lamp inductor LLA and the lamp capacitor CLA boost the lamp voltage gradually higher as the output frequency gets closer to their resonance frequency, until it is sufficient to ignite the lamp. In the meantime the current in the resonance circuit flows through the filaments providing quasi-preheating. The UBA2024 UBA2024 circuitry stops the frequency sweep at the resonance frequency, frsn, if the lamp has not ignited yet (see the UBA2024 UBA2024 data sheet for details). This ensures a maximum effort to ignite the lamp. The resonance frequency depends on LLA and CLA: 1 f rsn = -2 L LA × C LA (2) As the ignition frequency, fign, is higher than or equal to the resonance frequency the resonance frequency should be chosen so that the preferred ignition frequency is 1.6 × fout fign 1.8 × fout. The time needed to sweep down (set by CSW) from the start frequency to the resonance frequency can be used as an approximation for the ignition time. The sweep time is typically CSW (nF) × 10.3 ms. For large values the ignition time is shorter, because the lamp ignites before the resonance frequency is reached. The typical ignition time is 1 s when CSW = 330 nF. A larger CSW makes the sweep time longer and the preheating of the electrodes better. However, the rise of the preignition lamp ignition voltage is also slower. Both a quasi-preheat that is too short and a voltage rise that is too slow increase the glow time of the lamp. This reduces the lifetime of the lamp. During the glow phase the lamp is ignited, but the filaments and the gas inside the lamp are not at their final operating temperature. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 12 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 The UBA2024 UBA2024 has a mechanism to push extra energy into the lamp during this glow phase. This will make the lamp go to its final light output quicker which gives a longer lifetime for the lamp. Typical values for CSW are between 33 nF and 330 nF. 3.5 Choosing the other components For the rectifier bridge a bridge cell or separate diodes like the 1N5062 1N5062 can be used. The 1N4007 1N4007 can also be used but these diodes are more sensitive to voltage spikes. For a lamp current 150 mA with CDV = 220 pF and for a current 150 mA with CDV = 100 pF the value of CVDD and CFS is 10 nF. The advised half-bridge capacitors (C_HB1 and C_HB2) are greater than 47 nF when fout = 40 kHz to 50 kHz and greater than 68 nF when fout = 25 kHz to 30 kHz. The resonance frequency of the input pi filter, consisting of LFILT and CHB (CHB being the effective capacitor as seen on the HV pin of the IC, i.e. the series capacitance of CHB1 and CHB2), has to be at least two times lower than the nominal output frequency. Remark: Performance and lifetime cannot be guaranteed by using the values given in this chapter. The lamp and the UBA2024 UBA2024 performance strongly interact with each other and need to be qualified together as a combination. 3.6 About component tolerances For all components, typical tolerances can be used (20 % for electrolytic capacitors, 10 % for other capacitors (foil or ceramic) and 5 % for resistors and inductors). Since ROSC, COSC and LLA determine the lamp current, their tolerance also determines the spread in the lamp current. Therefore, the required lamp current accuracy may require closer tolerance for ROSC, COSC and LLA. · Example 1: If ROSC = ± 5 %, COSC = ± 10 %, LLA = ± 5 %, CLA = ± 10 % and the internal frequency of the IC = ± 3 %, the effective lamp current tolerance is 12.6 %. · Example 2: If ROSC = ± 1 %, COSC = ± 5 %, LLA = ± 5 %, CLA = ± 5 % and the internal frequency of the IC = ± 3 %, the effective lamp current tolerance is 7.1 %. 4. Quick measurements Table 2 compares the calculated values from the application development tool with measured values. Table 2. Measured values compared with the calculated values Lamp power (W) Power factor (pF) Input Input fout set voltage/ configuration (kHz) frequency (V/Hz) fout I lamp I lamp P burner measured calculated measured (W) (kHz) (mA) (mA) P burner measured (W) 18.3 0.59 120/60 doubler 45.5 43.0 208 211 16.5 17.1 18.0 0.54 230/50 standard 45.5 45.6 218 204 16.5 16.6 AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 13 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 5. Start-up and stop waveforms Fig 12. Cold start lamp waveforms. The first 650 ms there is quasi-preheating of the filaments. CSW = 220 nF. 6. Layout considerations The UBA2024 UBA2024 PCB layout, has a considerable influence on the performance of the IC, Issues to be taken into account are: · Coils with open magnetic circuits should not be placed opposite the IC (on the other side of the PCB). If an axial filter inductor is used for LFILT it should be placed in the same direction as the IC to minimize magnetic field pick-up. · The oscillator pin (pin 7, RC) and the sweep pin (pin 8, SW) should be shielded from output/lamp by a ground track. · Components on pins 7 and 8 should be placed as close to the IC as possible. · Capacitors CVDD and CFS should be placed close to the IC. · Mains input wires must not run parallel or near the half-bridge signal (pin 5, OUT) or near the output of the lamp inductor, bypassing the input filter. · If the UBA2024 UBA2024(A)T is used, all SGND pins need to be soldered to a copper plane for effective heat transfer. This copper plane is underneath the IC and extends as much as possible on both sides of the IC. Fixing the IC to the board using thermal conductive glue also helps cooling the IC. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 14 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 7. Application examples 7.1 Reference board 7.1.1 External lamp detection circuit The NXP evaluation board has an additional lamp detection circuit which is not required in mass production applications like CFLi (see Figure 13). In this section the functioning of this detection circuit is described. Fig 13. Circuit diagram demoboard with optional lamp detection circuit During start-up, in the quasi-preheat and the ignition phase, the voltage at the SW pin (pin 1) increases from 0 V to 3 V. At the same time the amplitude of the signal on the RC pin (pin 7) increases by the same amount. However, if the lamp is not ignited, because it is broken or missing, the sweep voltage will stay below the 3 V level or even drop to 0 V. The IC will not operate in Zero Voltage Switching mode (ZVS). Large currents run through the half-bridge causing the dissipation in the IC to exceed the maximum value. The half-bridge can only withstand the high dissipation until the junction temperature reaches 150 °C. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 15 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 At start-up the RC oscillator starts with an amplitude of 2 V on pin RC (pin 7). The half-bridge frequency is now running at 2.5 times the nominal operating frequency. When the burner is connected to the circuit the half-bridge operates in ZVS and the CSW capacitor charges. R6, R7 and C12 create an average DC voltage of the oscillator voltage on pin RC, which is basically half the amplitude. That voltage is then fed to the base of Q2-2, which functions as a comparator. At the same time that CSW is charging, C11 is charged by R3 from VDD. This takes place with a time constant of (R3//R4) × C11. The charging stops when the voltage on C11 reaches 1.6 V. The voltage on C11 is fed to the emitter of Q2-2 to compare it with its base voltage. Under normal conditions during start-up, when the lamp is connected, the average DC voltage from RC rises above 1.6 V at the end of the charging period for C11. The base emitter voltage of Q2-2 will stay reverse based and will not turn on. If, however, non-ZVS is detected in the switches of the half-bridge driver, because of an unconnected or broken lamp, the charging of CSW stops and the voltage on CSW drops to 0 V. The average DC voltage on the RC pin lowers to less than 1 V and Q2-2 starts to conduct. Q2-2 drives the latching transistor Q1-1 and the fault condition is latched by the left diode of the double diode, D5. At the same time the right diode of D5 will stop the UBA2024 UBA2024 half-bridge oscillator. The latch can be reset by power cycling the mains voltage with less than 1 s delay (for the test circuit this depends on the discharge time of C11 and R4). The latch circuit is designed in such a way that it is not noise sensitive. However, it is better to keep it away from the large signal tracks. Typically, the circuit triggers within 0.5 s from start-up when no lamp is connected. It also triggers when a lamp is removed while operating. When the protection has tripped, the dissipated power in the IC is about 0.6 W. The IC can dissipate this power continuously. Ensure that there is some reaction time margin (at room temperature) when choosing C11. Also, consider voltage derating of MLCC capacitors when low voltage types are used. It is advisable to choose an X7R type or an X5R type of at least 10 V. The protection circuit puts some additional capacitive loading (about 5 pF) on pin RC. This can become significant for small values of COSC. In this case the value of COSC is compensated for this effect by lowering ROSC from 200 k to 191 k (E96 series), giving an operating frequency of 45.9 kHz instead of 43.3 kHz. When the circuit is used it is advisable to add the extra 5 pF to COSC in Equation 1. Fig 14. Photo reference board UBA2024T/AT UBA2024T/AT (120 V (AC) version) AN10713 AN10713_2 Application note Fig 15. Photo reference board UBA2024T/AT UBA2024T/AT (230 V (AC) version) © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 16 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Fig 16. Photo reference board UBA2024P/AP UBA2024P/AP (120 V (AC) version) Table 3. Fig 17. Photo reference board UBA2024P/AP UBA2024P/AP (230 V (AC) version) Component values used for testing with 18 W PLC burner Reference Description Remarks Value/type 230 V (AC) Value/type 120 V (AC) RFUS fusible inrush current limiter resistor 10 /1 W 6.8 /1 W D1, D4 mains rectifier diodes 1N4007 1N4007 1N4007 1N4007 D2, D3 mains rectifier diodes 1N4007 1N4007 not mounted CBUF1 buffer capacitor 10 F/400 F/400 V 22 F/200 F/200 V CBUF2 buffer capacitor high temperature electrolytic type not mounted, place wire 22 F/200 F/200 V LFILT filter inductor axial type 1.8 mH 1.8 mH CHB1, CHB2 half bridge capacitors 100 nF/250 V (DC) 100 nF/250 V (DC) CLA lamp capacitor film type, capable of withstanding peak voltages of twice its DC-rating 2.2 nF/700 V (DC) 2.2 nF/700 V (DC) LLA lamp inductor E20-core 2.2 mH 2.2 mH CDV dV/dt limiting capacitor 220 pF/500 V (DC) 220 pF/500 V (DC) CFS floating supply buffer capacitor 10 nF/50 V 10 nF/50 V CVDD low voltage supply buffer capacitor 10 nF/50 V 10 nF/50 V COSC oscillator capacitor 2% 100 pF/50 V 100 pF/50 V ROSC oscillator resistor 1% CSW sweep time capacitor Table 4. 191 k/0.125 W 191 k/0.125 W 220 nF/25 V 220 nF/25 V Components values for the optional lamp detection circuit Reference Description Remarks R3 - 220 k/0.125 W R4 - 33 k/0.125 W R5 - 180 k/0.125 W R6, R7 - 1 M/0.125 W AN10713 AN10713_2 Application note Value/type © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 17 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Table 4. Components values for the optional lamp detection circuit Reference Description Remarks Value/type C11 ignition time-out capacitor MLCC X7R type or an X5R type with a voltage rating 10 V 3.3 F/10 V C12 - ceramic or MLCC C0G type D5 double diode common cathode Q1-1, Q2-2 PNP/NPN transistor in one package or use separate transistors (see below). hFE > 100 at 10 A BC847BNP BC847BNP Q1-1 hFE > 100 at 10 A BC847B BC847B Q2-2 hFE > 100 at 10 A BC857B BC857B 220 pF/16 V BAV70W BAV70W 7.2 UBA2024 UBA2024 with additional feed-forward circuit 7.2.1 Introduction With a typical half-bridge topology the output power and current depends on the bus voltage. When the mains voltage increases the dissipated power increases. This could cause lamp failure or the IC junction temperature to exceed the maximum allowed temperature (150 °C). By implementing a feed-forward circuit, this can be prevented. With feed-forward a higher bus-voltage will cause a higher operating frequency and thus a lower half-bridge current, compensating for the increase of the bus voltage. Typically, a feed-forward circuit is only needed if the mains voltage increases by e.g. 30 % for a long period of time, which only occurs in a few countries in the world. The application development tool calculation shows how much power will be put in the lamp and what the current will be. This limit differs from application to application. 7.2.2 Implementation Feed-forward can easily be applied via the additional circuit R1, R2 and Q1 as shown in Figure 18. The system should be designed so that the feed-forward circuit does not inject current in COSC at the typical operating point of the lamp. For a 230 V (AC) mains system the circuit should not operate at a voltage below 2 × 230 V (AC) = 325 V. This circuit starts to inject current in the oscillator capacitor when VHV equals: R1 V HV = ( V VDD ( min ) + 0.7 ) 1 + - R2 (3) In the example of Figure 18 this yields: 2.0M V HV = ( 11.7 + 0.7 ) 1 + - = 328V 78.7k (4) Above 328 V the injected current into the oscillator pin equals: V bus V bus I CF = - = -R1 2.0M (5) Results: AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 18 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 An 18 W CFL circuit has been applied with and without feed-forward as described above. The results can be seen in Figure 19. Fig 18. Example feed-forward circuit Input power versus HV voltage Pin feed-forward [W] Pin no feed-forward [W] 25 Input power [W] 20 15 10 5 0 270 290 310 330 350 370 390 Vbus [V] Fig 19. Feed-forward results 7.3 Driving a CCFL lamp with the UBA2024 UBA2024 By using a transformer instead of a coil, the UBA2024P UBA2024P can be used to drive CCFL lamps. Figure 20 shows the circuit diagram for a CCFL application. For EMI reasons a high voltage (2 kV) capacitor of 2.2 nF may need to be connected to pin 1 of the primary winding (grounded side) and to pin 3 of the secondary winding. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 19 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 U1 LFILT 1 6 2 K1 2 1 RFUS D3 1 VDD 7 2 ROSC CCFL 1 D1 HV 3 CHB1 FS RC 1 8 1 2 + 1 2 CBUF CLA 1 1 CON2 2 D2 D4 3 1 1 2 2 2 5 4 2 OUT SW 1 1 1 T1 CHB2 2 2 1 COSC UBA2024P UBA2024P CFS VDV 2 CVDD 1 4 PGND SGND CSW 2 2 2 Fig 20. Circuit diagram of UBA2024 UBA2024 for CCFL 7.4 UBA2024 UBA2024 in a replaceable lamp configuration (match box ballast) The UBA2024 UBA2024 in Figure 21 will not be powered unless a lamp is in place. Therefore when a lamp is replaced it will automatically start when the new lamp is inserted. This is particularly useful when the UBA2024 UBA2024 is used in so-called 'match box' ballasts driving 4-pin, PL-C, Dulux D/E Dulux T/E, DBX, or TBX type of burners. Since the IC is intended for use in low cost integrated CFL applications, it lacks an open or no load protection. Therefore the protection circuit, as described in Section 7.1.1 and shown in Figure 13, is a requirement for this application. With only three resistors and a single transistor an optional feed forward circuit can be added, limiting the lamp power if the mains voltage becomes too high. This extends the lamp lifetime. The UBA2024AP UBA2024AP is a recommended component to drive the higher power burners of up to 18 W. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 20 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Fig 21. Circuit diagram for replaceable lamp with required protection and optional feed-forward Table 5. Component values used for replaceable 18 W burner (80 V /210 mA Reference Description Remarks Value/type 230 C (AC) Value/type 120 V (AC) RFUS fusible inrush current limiter resistor 10 /1 W 6.8 /1 W D1, D4 mains rectifier diodes 1N4007 1N4007 Not mounted D2, D3 mains rectifier diodes 1N4007 1N4007 1N4007 1N4007 CBUF1 buffer capacitor 10 F/400 F/400 V 22 F/200 F/200 V CBUF2 buffer capacitor high temperature electrolytic type not mounted, place wire 22 F/200 F/200 V LFILT filter inductor axial type 1.8 mH 1.8 mH Cdc half bridge capacitor 150 nF/400 V (DC) 150 nF/400 V (DC) CLA lamp capacitor film type, capable of withstanding peak voltages of twice its DC-rating 2.2 nF/700 V (DC) 2.2 nF/700 V (DC) LLA lamp inductor E20-core 2.1 mH 2.1 mH CDV dV/dt limiting capacitor 220 pF/500 V (DC) 220 pF/500 V (DC) CFS floating supply buffer capacitor 10 nF/50 V 10 nF/50 V CVDD low voltage supply buffer capacitor 10 nF/50 V 10 nF/50 V COSC oscillator capacitor 2% 100 pF/50 V 100 pF/50 V ROSC oscillator resistor 1% 191 k/0.125 W 191 k/0.125 W CSW sweep time capacitor 220 nF/25 V 220 nF/25 V AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 21 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 Table 6. Components values for the lamp detection circuit and optional feed forward Reference Description Remarks Value/type R1A, R1B optional; feed forward 1 M/0.125 W R2 optional; feed forward 78.7 k/0.125 W R3 - 220 k/0.125 W R4 - 33 k/0.125 W R5 - 180 k/0.125 W R6, R7 - 1 M/0.125 W C11 ignition time-out capacitor MLCC X7R type or X5R type 3.3 F/10 V C12 - ceramic or MLCC C0G type 220 pF/16 V D5 double diode common cathode Q1-1, Q1-2 PNP/NPN transistor in one package or use separate transistors (see below). hFE > 100 at 10 mA BC857B/BC847 BC857B/BC847 or BC847BNP BC847BNP Q1-1 hFE > 100 at 10 mA BC847B BC847B Q2-2 hFE > 100 at 10 mA BC857B BC857B Q2 BAV70W BAV70W optional; feed forward BC857B BC857B AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 22 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 8. Legal information 8.1 Definitions Draft - The document is a draft version only. The content is still under internal review and subject to formal approval, which may result in modifications or additions. NXP Semiconductors does not give any representations or warranties as to the accuracy or completeness of information included herein and shall have no liability for the consequences of use of such information. 8.2 Suitability for use - NXP Semiconductors products are not designed, authorized or warranted to be suitable for use in medical, military, aircraft, space or life support equipment, nor in applications where failure or malfunction of a NXP Semiconductors product can reasonably be expected to result in personal injury, death or severe property or environmental damage. NXP Semiconductors accepts no liability for inclusion and/or use of NXP Semiconductors products in such equipment or applications and therefore such inclusion and/or use is at the customer's own risk. Applications - Applications that are described herein for any of these products are for illustrative purposes only. NXP Semiconductors makes no representation or warranty that such applications will be suitable for the specified use without further testing or modification. Disclaimers General - Information in this document is believed to be accurate and reliable. However, NXP Semiconductors does not give any representations or warranties, expressed or implied, as to the accuracy or completeness of such information and shall have no liability for the consequences of use of such information. Right to make changes - NXP Semiconductors reserves the right to make changes to information published in this document, including without limitation specifications and product descriptions, at any time and without notice. This document supersedes and replaces all information supplied prior to the publication hereof. Export control - This document as well as the item(s) described herein may be subject to export control regulations. Export might require a prior authorization from national authorities. 8.3 Trademarks Notice: All referenced brands, product names, service names and trademarks are the property of their respective owners. AN10713 AN10713_2 Application note © NXP B.V. 2009. All rights reserved. Rev. 02 - 10 October 2009 23 of 24 AN10713 AN10713 NXP Semiconductors 18 W CFL lamp design using UBA2024 UBA2024 9. Contents 1 1.1 1.2 2 3 3.1 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.3 3.4 3.5 3.6 4 5 6 7 7.1 7.1.1 7.2 7.2.1 7.2.2 7.3 7.4 8 8.1 8.2 8.3 9 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 System benefits . . . . . . . . . . . . . . . . . . . . . . . . 3 Circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . 4 Design of an 18 W non-dimmable CFL . . . . . . 4 Selecting input configuration, buffer capacitor and fuse-resistor . . . . . . . . . . . . . . . . . . . . . . . . 4 Choosing frequency, lamp inductor and capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Input values . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Calculation plots . . . . . . . . . . . . . . . . . . . . . . . . 8 Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Thermal properties . . . . . . . . . . . . . . . . . . . . . 10 Literature reference . . . . . . . . . . . . . . . . . . . . 11 Operating frequency . . . . . . . . . . . . . . . . . . . . 11 Ignition frequency and quasi-preheating . . . . 12 Choosing the other components. . . . . . . . . . . 13 About component tolerances . . . . . . . . . . . . . 13 Quick measurements. . . . . . . . . . . . . . . . . . . . 13 Start-up and stop waveforms . . . . . . . . . . . . . 14 Layout considerations. . . . . . . . . . . . . . . . . . . 14 Application examples . . . . . . . . . . . . . . . . . . . 15 Reference board . . . . . . . . . . . . . . . . . . . . . . . 15 External lamp detection circuit . . . . . . . . . . . . 15 UBA2024 UBA2024 with additional feed-forward circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Implementation . . . . . . . . . . . . . . . . . . . . . . . . 18 Driving a CCFL lamp with the UBA2024 UBA2024. . . . . 19 UBA2024 UBA2024 in a replaceable lamp configuration (match box ballast) . . . . . . . . . . 20 Legal information. . . . . . . . . . . . . . . . . . . . . . . 23 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 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. 2009. All rights reserved. For more information, please visit: http://www.nxp.com For sales office addresses, please send an email to: salesaddresses@nxp.com Date of release: 10 October 2009 Document identifier: AN10713 AN10713_2