7 - Elec1-Lec7.ppt - Electronics 1 Lecture 7 Diode types...

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Electronics 1 Lecture 7 Diode types and application
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Outline Working of Rectifier. Half Wave Rectifier. Full Wave Rectifier. Ripple effect Clippers Clampers Voltage multiplier (Doubler Circuit) References
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Half Wave Rectifier The diode only conducts when it is forward biased, therefore only half of the AC cycle passes through the diode to the output. The DC output voltage is 0.318 V m , where V m = the peak AC voltage .
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Full Wave Rectifier(FWR)
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Ripple Effect (RE)...
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cont... So far this rectifier is not very useful. Even though the output does not change polarity it has a lot of ripple. “The variation in the capacitor voltage due to charging and discharging is called the ripple voltage”. To generate an output voltage that more closely resembles a true d.c. voltage we can use a reservoir or smoothing capacitor in parallel with the output (load) resistance (prev slide fig b).
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Ripple Effect...
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Ripple Effect... For a given input frequency, the output frequency of a full wave rectifier is twice that of a half wave rectifier. As a result, a full wave rectifier is easier to filter because of the shorter time between peaks.
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Compraison of HWR & FWR
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Ripple Voltage Calculations V r(pp) = (1/fR L C)V p( rect) V DC = (1 – 1/2fR L C)V p (rect)
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Smoothed Half Wave Rectifier Circuit with reservoir capacitor Output voltage The capacitor charges over the period t 1 to t2 when the diode is on and discharges from t2 to t3 when the diode is off.
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Smoothed Half Wave Rectifier When the supply voltage exceeds the output voltage the (ideal) diode conducts. During the charging period (t 1 < t< t 2 ) v o = V M sin ( t) (The resistance in the charging circuit is strictly R f which we have assumed to be zero. Even for a practical diode R f C will be very small)
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  • Fall '19
  • Rectifier, Diode Clamper

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