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Why DC output voltage is greater than AC input voltage in rectifier ?

In a rectifier, the DC output voltage is not inherently greater than the AC input voltage. Instead, the rectifier’s primary function is to convert alternating current (AC) to direct current (DC) by allowing the flow of current in one direction.

The apparent increase in voltage is often associated with the measurement methods used, particularly when comparing root mean square (RMS) values of AC and DC voltages.

Here’s a breakdown of the process:

  1. AC Input:
    • The AC input voltage is typically represented by its RMS value. RMS is a way of expressing the equivalent constant DC voltage that would produce the same heating effect as the AC voltage.
    • For a sinusoidal AC waveform, the RMS value is approximately 0.707 times the peak value.
  2. Rectification:
    • The rectifier allows the positive half-cycle of the AC waveform to pass through, effectively converting AC to pulsating DC.
    • The DC component of the rectified waveform is not equivalent to the RMS value of the AC input; it is related to the peak value of the AC waveform.
  3. Measurement Consideration:
    • When comparing the AC RMS voltage to the DC output voltage, the DC output may appear higher because it is often measured as the peak value of the rectified waveform.

In reality, the average or DC component of the rectified waveform is less than the peak value of the AC waveform. The relationship between the peak voltage (V_peak) and the RMS voltage (V_RMS) for a sinusoidal waveform is given by V_RMS = 0.707 * V_peak.

So, if the rectifier is providing a DC voltage equivalent to the peak of the AC waveform, it might seem higher when comparing it directly to the RMS value of the AC input.

It’s essential to consider the measurement context and be aware that the rectifier doesn’t inherently increase the voltage; it transforms the AC waveform into a pulsating DC waveform, and the measurement methods may influence the perceived voltage values.

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