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LYT4217 Datasheet(PDF) 8 Page - Power Integrations, Inc. |
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LYT4217 Datasheet(HTML) 8 Page - Power Integrations, Inc. |
8 / 20 page Rev. B 02/13 8 LYT4211-4218/4311-4318 www.powerint.com Modified DER-350 25 W High Power Factor LED Driver for Non-Dimmable and Enhanced Line Regulation The circuit schematic in Figure 9 shows a high power factor LED driver based on a LYT4317 from the LYTSwitch family of devices. It was optimized to drive an LED string at a voltage of 36 V with a constant current of 0.7 A, ideal for high lumen PAR lamp retro-fit applications. The design operates over the low-line input voltage range of 90 VAC to 132 VAC and is non-dimming application. A non-dimming application has tighter output current variation with changes in the line voltage than a dimming application. It’s key to note that, although not specified for dimming, no circuit damage will result if the end user does operate the design with a phase controlled dimmer. Modification for Non-Dimmable Configuration The design is configurable for non-dimmable application by simply removing the component for SCR active damper (R6, R8, C3, and Q1), blocking diode D9 and R-C bleeder (R1, C1) changes and replacing the reference resistor R14 with 24.9 k W. (See Figure 9) Key Application Considerations Power Table The data sheet power table (Table 1) represents the minimum and maximum practical continuous output power based on the following conditions: • Efficiency of 80% • Device local ambient of 70 °C • Sufficient heat sinking to keep the device temperature below 100 °C • For minimum output power column • Reflected output voltage (V OR) of 120 V • FEEDBACK pin current of 135 µA • BYPASS pin capacitor value of 47 µF • For maximum output power column • Reflected output voltage (V OR) of 65 V • FEEDBACK pin current of 165 µA • BYPASS pin capacitor value of 4.7 µF (LYT4x11 = 4.7 µF) Note that input line voltages above 85 VAC do not change the power delivery capability of LYTSwitch devices. Device Selection Select the device size by comparing the required output power to the values in Table 1. For thermally challenging designs, e.g., incandescent lamp replacement, where either the ambient temperature local to the LYTSwitch device is high and/or there is minimal space for heat sinking use the minimum output power column. This is selected by using a 47 µF BYPASS pin capacitor and results in a lower device current limit and therefore lower conduction losses. For open frame design or designs where space is available for heat sinking then refer to the maximum output power column. This is selected by using a 4.7 µF BYPASS pin capacitor for all but the LYT4x11 which has only one power setting. In all cases in order to obtain the best output current tolerance maintain the device temperature below 100 °C Maximum Input Capacitance To achieve high power factor, the capacitance used in both the EMI filter and for decoupling the rectified AC (bulk capacitor) must be limited in value. The maximum value is a function of the output power of the design and reduces as the output power reduces. For the majority of designs limit the total capacitance to less than 200 nF with a bulk capacitor value of 100 nF. Film capacitors are recommended compared to ceramic types as they minimize audible noise with operating with leading edge phase dimmers. Start with a value of 10 nF for the capacitance in the EMI filter and increase in value until there is sufficient EMI margin. PI-6875a-101512 D S BP V R FB CONTROL FL1 T1 RM8 12 1 FL2 10 11 R10 2 M Ω 1% R15 200 k Ω R9 510 k Ω 1/8 W R24 47 k Ω 1/8 W R25 47 k Ω 1/8 W R2 47 k Ω 1/8 W L1 1 mH L2 1 mH R14 24.9 k Ω 1% 1/16 W R18 165 k Ω 1% 1/16 W R23 20 k Ω 36 V, 700 mA 90 - 132 VAC RTN L N R19 20 k Ω 1/8 W C5 100 nF 50 V R26 30 Ω R20 39 Ω 1/8 W R17 3 k Ω 1/10 W R27 10 Ω 1/10 W D2 DFLU1400 C7 2.2 nF 630 V D3 US1J D5 BAV16 Q2 MMBT3904 D8 BAV21 D6 BAV21 D7 BYW29-200 D4 US1D R22 1 k Ω 1/10 W BR1 MB6S 600 V RV1 140 VAC F1 5 A C11 330 µF 63 V C13 100 pF 200 V CY1 470 pF 250 VAC C12 330 µF 63 V C8 47 µF 16 V C15 100 nF 50 V C14 10 nF 50 V C9 56 µF 50 V LYTSwitch U1 LYT4317E C6 2.2 µF 250 V C4 100 nF 250 V L3 5 mH C2 100 nF 250 V Figure 9. Modified Schematic of RD-350 for Non-Dimmable, Isolated, High Power Factor, 90-132 VAC, 25 W / 36 V LED Driver. |
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