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AL9910S-13 Datasheet(PDF) 11 Page - Diodes Incorporated |
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AL9910S-13 Datasheet(HTML) 11 Page - Diodes Incorporated |
11 / 16 page AL9910/AL9910A/AL9910-5 UNIVERSAL HIGH VOLTAGE HIGH BRIGHTNESS LED DRIVER AL9910/AL9910A/AL9910-5 Document number: DS35103 Rev. 7 - 2 11 of 16 www.diodes.com February 2012 © Diodes Incorporated Applications Information (cont.) Input Bulk Capacitor For Offline lamps an input bulk capacitor is required to ensure that the rectified AC voltage is held above twice the LED string voltage throughout the AC line cycle. The value can be calculated from: ≥ IN C MAX _ DC L MIN _ LINE CH IN V f 2 V 2 ) D 1 ( P Δ × × × − × Where ch D : Capacity charge work period, generally about 0.2~0.25 L f : Input frequency for full range (85~265VRMS) MAX _ DC V Δ Should be set 10~15% of MIN _ LINE V 2 If the capacitor has a 15% voltage ripple then a simplified formula for the minimum value of the bulk input capacitor approximates to: CMIN = 2 IN LEDs LED V 0.06 V I × × Power Factor Correction If power factor improvement is required then for the input power less than 25W, a simple passive power factor correction circuit can be added to the AL9910 typical application circuit. Figure 4 shows that passive PFC circuitry (3 current steering diodes and 2 identical capacitors) does not significantly affect the rest of the circuit. Simple passive PFC improves the line current harmonic distortion and achieves a power factor greater than 0.85. Fig. 4 Typical Application Circuit with Passive PFC Each of these identical capacitors should be rated for half of the input voltage and have twice as much capacitance as the calculated CMIN of the buck converter circuit without passive PFC (see above section on bulk capacitor calculation). For further design information please see AN75 from the Diodes website. R SENSE AL9910/A GATE CS LD PWM_D GND R OSC V DD V IN LED + LED - V AC IN Q1 L1 D1 R OSC C3 C4 BR1 Passive PFC C1 C2 R SENSE AL9910/A GATE CS LD PWM_D GND R OSC V DD V IN LED + LED - V AC IN Q1 L1 D1 R OSC C3 C4 BR1 Passive PFC C1 C2 |
Similar Part No. - AL9910S-13 |
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Similar Description - AL9910S-13 |
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