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Power-Factor-Slide4

However, most AC circuits do not have such ideal behavior. Consider a bridge rectifier with a capacitive filter circuit which is common in low power flyback converters in adapters, audio power amplifiers, and typical consumer electronics. The diode bridge elements only conduct current during the top of the AC waveform when it is possible to create a forward voltage drop across the diode between the AC line input and the power supply capacitor. This results in AC current conduction over a narrow interval, and changes the harmonic content of the load current waveform compared with the input voltage. The amount of usable power is dramatically decreased, and the high harmonic current typically results in excess heating of utility transformer laminations, which are designed and optimized for 50 Hz or 60 Hz line frequency, not a harmonic content up to ten times higher.

PTM Published on: 2011-09-02