puolijaksorectifierin

Puolijaksorectifierin, Finnish for "half-wave rectifier," is an electronic circuit that converts alternating current into pulsating direct current by allowing current to flow for only one half of each AC cycle. A simple version uses a single diode in series with a load, typically with an isolated AC source provided by a transformer.

In operation, during the positive half-cycle the diode becomes forward biased and conducts, delivering current to the load; during the negative half-cycle the diode is reverse biased and blocks current, so the load sees zero voltage. The result is a pulsating DC waveform whose peak follows the input peak minus the diode forward drop.

Key performance characteristics depend on the diode and load. With an ideal diode and a purely resistive load, the DC output voltage is Vdc = Vm/π, the DC current Idc = Vdc/R, and the rectifier efficiency η = Pdc/Pin equals 4/π^2 ≈ 0.405. In practice, diode drops (for silicon about 0.6–0.8 V) reduce Vdc and efficiency. The output contains substantial ripple at the same frequency as the input, making smoothing desirable for many applications.

Common variations include using different transformer voltages or adding filtering elements. A smoothing capacitor or an LC filter can reduce ripple and raise the average DC level, at the cost of higher peak currents and transformer stress.

Applications include signal demodulation (envelope detectors) and simple, low-power power supplies. Compared with full-wave rectifiers, the half-wave version is simpler and cheaper but provides poorer voltage regulation, higher ripple, and lower efficiency for most loads.