Welcome Products Applications Support Contact Us Login CCFL Suggested testing AT Editor Schematic for CCFL The AT Editor software representation of the part is shown here to the left. AT Editor schematic AT Fixturing for CCFL The transformer package is a standard surface mount design, and as such is not suitable for Kelvin pins. The fixturing shown here is a zero insertion force socket (ZIF) in which pairs of blades are closed onto each pin from the side. This has the advantage of not putting the part under any mechanical strain whilst still maintaining a true Kelvin contact to each winding. ZIF (zero insertion socket) on 91-184 fixture ZIF (zero insertion socket) on 91-184 fixture AT Test Program for CCFL The winding resistances are checked first to validate continuity and connection. This is followed by and inductance check at the operating frequency on the primary. This is followed by three checks of the turns ratios; half primary to half primary, primary to feedback and primary to secondary. Note that the last test is performed by energizing the secondary as for optimum accuracy it is best practice to energise the winding with the greatest number of turns. Get PDF of test program Get At Editor ATP file for program Get AT Series Editor software We then test leakage inductance between primary and secondary; we find that the leakage is roughly 25% of the primary inductance as this is probably a deliberate design factor in the operation of the output LC circuit. For this we have used percentage limits around a nominal LL value, rather that checking LL is just below a maximum as is normally the case. As the secondary is made from fine wire, and subject to high voltages and even higher “strike” voltages to start the gas tube, we next use the SURG test to check for any Inter-winding coil weaknesses. This is performed by injecting high voltage pulses and measuring the characteristic ringing decay on the secondary winding. An empirical nominal from a known good transformer is selected for our limits. Any breakdown in the insulation will result in energy loss and hence a different decay response. See the link at the end of this section for more information on SURGE testing. Finally a HI POT test at 2 kV AC is used to check primary to secondary isolation. # Test Description Pins and Conditions Reason 1 R DC resistance pin 1-3, limits <135 mOhms To check the total primary winding resistance is below a maximum. Also acts as a check of correct wire gauge and good termination. 2 R DC resistance pin 4-5, limits <100 mOhms To check the feedback winding resistance is below a maximum. Also acts as a check of correct wire gauge and good termination. 3 R DC resistance pin 10-6, limits <175 Ohms To check the secondary winding resistance is below a maximum. Also acts as a check of correct wire gauge and good termination. 4 LS Series Inductance Pin 1-3, 100mV, 20 kHz, nominal 27 uH +/- 10% (as per published spec) Inductance as seen by the primary. To check the correct number of turns and correct operation of the core material 5 TR Turns Ratio Energise pins 1-3, 100 mV 40 kHz, check Turns ratio and phase 1-2:2-3 to be 1:1 +/- 5% To check correct ratio of windings between the two halves of the primary to the centre tap. 6 TR Turns Ratio Energise pins 1-3, 100 mV 40 kHz, check Turns ratio and phase 1-3:4-5 to be 4.6:1 +/- 5% To check correct ratio of windings from whole of the primary to the feedback winding. 7 TR Turns Ratio Energise pins 10-6, 100 mV 10 kHz, check Turns ratio and phase 10-6:1:3 to be 86:1 +/- 5% To check correct ratio of windings from secondary to primary. The winding with the most turns is energised as this is best practice for optimum accuracy. 8 LL Leakage Inductance Pins 1-3 Hi, Pins 10-6 Low, 100 mV, 40 kHz , check leakage is below 6.5 uH To check leakage is below specified limit as a validation of correct placement and operation of windings. 9 SURG Surge Stress Test Energise pins 10-6, 4000 V, 5 pulses. Check that mVs product is 166 mVs +/- 30% To check for weak points in the secondary inter turn insulation, to prove longevity of the part over its operational life. 10 HPAC AC Hi-Pot 2 kV AC,50Hz, 1 second, Pins 1,2,3,4,5 High, Pins 10,6 LO. Check <15 mA current To check isolation as per datasheet. AT5600 Run time 2.61 sec (AT3600 Run time 5.49 sec) Notes: As the Leakage Inductance is governed by turns ratio, and core response (already covered by TR and LS) and the physical positioning of the windings, some customers (using automatic winding methods) may have enough confidence in winding positioning to only audit this parameter occasionally, rather then on every part tested. AT Test Results for CCFL Links for CCFL Transformers The Eaton Electronics homepage The Eaton CTX210607 datasheet Wikipedia article on CCFL inverters Wikipedia article on Royer Oscillators Our article on Detecting Shorted Windings Our Article on Leakage Inductance Our article on the Audit Test option on the AT5600 Email Voltech USA 1-239-437-0494 EUR 44 1235 861173 ASIA 44-1235-364-012 Products Applications Support Service Contact Us Terms Of Business Terms Of Use Privacy Any problems or questions using this website? Let us know! 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