поискавой системы для электроныых деталей |
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SB3100 датащи(PDF) 8 Page - Fairchild Semiconductor |
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SB3100 датащи(HTML) 8 Page - Fairchild Semiconductor |
8 / 12 page AN-9719 APPLICATION NOTE © 2010 Fairchild Semiconductor Corporation www.fairchildsemi.com Rev. 1.0.0 • 11/2/10 8 The typical voltage and current margins for the rectifier diode are as follows: 1.2 · (18) 1.8 · (19) where VRRM is the maximum reverse voltage and IF is the current rating of the diode. (Design Example) The diode voltage and current are calculated as: 12 373 5.8 76.3 · 1 5.8 · 0.31 1 0.48 0.48 1.87 5A and 100V diodes in parallel are selected for the rectifier diode. [STEP-10] Feedback Circuit Configuration Since FSL-series employs current-mode control, the feedback loop can be implemented with a one-pole and one- zero compensation circuit. The current control factor of FPS, K, is defined as: 2.5 (20) where ILIM is the pulse-by-pulse current limit and VFB SAT is the feedback saturation voltage, typically 2.5V. As described in Step-4, it is typical to design the flyback converter to operate in CCM for heavy-load condition. For CCM operation, the control-to-output transfer function of a flyback converter using current mode control is given by: · · ⁄ 2 · 1 ⁄ 1 ⁄ 1 ⁄ (21) where RL is the load resistance. The pole and zeros of Equation 21 are obtained as: 1 , 1 ⁄ 1 (22) here D is the duty cycle of the FPS and RC is the ESR of CO. Notice that there is a right-half-plane (RHP) zero (ωRZ) in the control-to-output transfer function of Equation 21. Because the RHP zero reduces the phase by 90 degrees, the crossover frequency should be placed below the RHP zero. Figure 13 shows the variation of a CCM flyback converter control-to-output transfer function for different input voltages. This figure shows the system poles and zeros with the DC gain change for different input voltages. The gain is highest at the high input voltage condition and the RHP zero is lowest at the low input voltage condition. Figure 13. CCM Flyback Converter Control-to-Output Transfer Function Variation for Different Input Voltage Figure 14 shows the variation of a CCM flyback converter control-to-output transfer function for different loads. Note that the DC gain changes for different loads and the RHP zero is the lowest at the full-load condition. Figure 14. CCM Flyback Converter Control-to-Output Transfer Function Variation for Different Loads When the input voltage and the load current vary over a wide range, it is not easy to determine the worst case for the feedback loop design. The gain, together with zeros and poles, varies according to the operating conditions. Even though the converter is designed to operate in CCM or at the boundary of DCM and CCM in the minimum input voltage and full-load condition; the converter enters into DCM, changing the system transfer functions as the load current decreases and/or input voltage increases. |
Аналогичный номер детали - SB3100 |
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Аналогичное описание - SB3100 |
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