поискавой системы для электроныых деталей |
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SB380 датащи(PDF) 6 Page - Fairchild Semiconductor |
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SB380 датащи(HTML) 6 Page - Fairchild Semiconductor |
6 / 12 page AN-9719 APPLICATION NOTE © 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com Rev. 1.0.0 • 11/2/10 6 Once LM is calculated from equation (7) after choosing KRF, the peak and RMS current of the MOSFET for the minimum input voltage and nominal load condition are obtained as: ∆ 2 (8) 3 ∆ 2 3 (9) where: · (10) and ∆ · · (11) I Δ 2 RF EDC I K I Δ = S PK D I Figure 10. MOSFET Current and Ripple Factor (KRF) (Design Example ) Choosing the ripple factor as 0.88, · 2· · · 79 · 0.48 2 · 15 · 100 10 ·0.88 540 · 15 79 · 0.48 0.4 ∆ · · 79 · 0.48 540 10 · 100 10 0.7 ∆ 2 0.4 0.35 0.75 3 ∆ 2 3 3 0.4 0.35 0.48 3 0.31 [STEP-5] Choose the Proper FPS Considering Input Power and Peak Drain Current With the resulting maximum peak drain current of the MOSFET (IDS PK) from Equation 8, choose the proper FPS for which the pulse-by-pulse current limit level (ILIM) is higher than IDS PK. Since FPS has ±10% tolerance of ILIM, there should be some margin when choosing the proper FPS device. The FSL-series lineup with proper power rating is summarized in Table 3. Table 3. Lineup of FSL1x7-Series with Power Rating Product ILIM at VIN=1.2V 85-265VAC Open Frame Min. Typ. Max. FSL127H 0.51A 0.61A 0.71A 16W FSL137H 0.74A 0.84A 0.94A 19W (Design Example) 0.75 0.84 . FSL137H is selected. [STEP-6] Determine the Minimum Primary Turns With a given magnetic core, the minimum number of turns for the transformer primary side to avoid the core saturation is given by: · · 10 (12) where Ae is the cross-sectional area of the core in mm 2, ILIM is the pulse-by-pulse current limit level, and BSAT is the saturation flux density in Tesla. The pulse-by-pulse current limit level is included in Equation 12 because the inductor current reaches the pulse- by-pulse current limit level during the load transient or overload condition. Figure 11 shows the typical characteristics of ferrite core from TDK (PC40). Since the saturation flux density (BSAT) decreases as temperature increases, the high-temperature characteristics should be considered. If there is no reference data, use BSAT =0.3 T. Figure 11.Typical B-H Characteristics of Ferrite Core (TDK/PC40) |
Аналогичный номер детали - SB380 |
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Аналогичное описание - SB380 |
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