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Moteur de recherche de fiches techniques de composants électroniques |
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Moteur de recherche de fiches techniques de composants électroniques |
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MC34262D Fiches technique(PDF) 6 Page - ON Semiconductor |
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MC34262D Fiches technique(HTML) 6 Page - ON Semiconductor |
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6 / 19 page  MC34262, MC33262 http://onsemi.com 6 0 1020 3040 VCC, SUPPLY VOLTAGE (V) VFB = 0 V Current Sense = 0 V Multiplier = 0 V CL = 1.0 nF f = 50 kHz TA = 25°C −55 −25 0 25 50 75 100 125 TA, AMBIENT TEMPERATURE (°C) Figure 14. Supply Current versus Supply Voltage Figure 15. Undervoltage Lockout Thresholds versus Temperature Startup Threshold (VCC Increasing) 16 12 8.0 4.0 0 14 13 12 11 9.0 7.0 8.0 10 Minimum Operating Threshold (VCC Decreasing) FUNCTIONAL DESCRIPTION Introduction With the goal of exceeding the requirements of legislation on line−current harmonic content, there is an ever increasing demand for an economical method of obtaining a unity power factor. This data sheet describes a monolithic control IC that was specifically designed for power factor control with minimal external components. It offers the designer a simple, cost−effective solution to obtain the benefits of active power factor correction. Most electronic ballasts and switching power supplies use a bridge rectifier and a bulk storage capacitor to derive raw dc voltage from the utility ac line, Figure 15. Figure 16. Uncorrected Power Factor Circuit AC Line Rectifiers Converter Bulk Storage Capacitor + Load This simple rectifying circuit draws power from the line when the instantaneous ac voltage exceeds the capacitor voltage. This occurs near the line voltage peak and results in a high charge current spike, Figure 16. Since power is only taken near the line voltage peaks, the resulting spikes of current are extremely nonsinusoidal with a high content of harmonics. This results in a poor power factor condition where the apparent input power is much higher than the real power. Power factor ratios of 0.5 to 0.7 are common. Power factor correction can be achieved with the use of either a passive or an active input circuit. Passive circuits usually contain a combination of large capacitors, inductors, and rectifiers that operate at the ac line frequency. Active circuits incorporate some form of a high frequency switching converter for the power processing, with the boost converter being the most popular topology, Figure 17. Since active input circuits operate at a frequency much higher than that of the ac line, they are smaller, lighter in weight, and more efficient than a passive circuit that yields similar results. With proper control of the preconverter, almost any complex load can be made to appear resistive to the ac line, thus significantly reducing the harmonic current content. Figure 17. Uncorrected Power Factor Input Waveforms Vpk Rectified 0 AC Line Voltage 0 AC Line Current Line Sag DC The MC34262, MC33262 are high performance, critical conduction, current−mode power factor controllers specifically designed for use in off−line active preconverters. These devices provide the necessary features required to significantly enhance poor power factor loads by keeping the ac line current sinusoidal and in phase with the line voltage. |
Numéro de pièce similaire - MC34262D |
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Description similaire - MC34262D |
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