Power Electronics

Single-phase full-wave diode rectifier


Single-phase full-wave diode rectifier

Single-phase diode rectifier, converting ac signal into a dc voltage, exist in two types – half-wave and full-wave one. Half-wave diode rectifier was mentioned before.

Full-wave diode rectifier can be two types as well – with a centre-tapped transformer and bridge rectifier. Both of them are depicted on the figure below.

In the case of center-tapped transformer, we have two half-wave rectifiers, combined. The DC currents of these half-wave transformers are equal but opposite. Each diode conducts in corresponding half-cycle of transformer. Below you can see the current and voltage wave-forms for this rectifier.

full-wave centre-tapped rectifier
Full-wave center-tapped rectifier


Bridge rectifier circuit is depicted below. Here we have four diodes instead of two. So in each half-cycle of transformer we have two conducting diodes. Below you can see voltage and current wave-forms for this rectifier.

full-wave bridge rectifier
Full-wave bridge rectifier


The average voltage is VDC=ωT0TVmsinωtdt.

So VDC=2Vmπ=0.636Vm.  Root-mean-square (RMS) value is RMS=1T0Tv2L(t)dt=ωπ0π(Vmsinωt)2dt

and VL=Vm2=0.707Vm.

The average value of load current Idc=VdcR=0.636VdcR. And the RMS value of load current is IL=0.707VmR.

The rectification ratio (RF), measures of rectification effectiveness  σ=PdcPL=0.81.

Form factor (FF) is a ratio of root-mean-square value of voltage or current to it’s average value. FF=VLVdc and FF=ILIdc. For full-wave rectifier FF=1.1.

Ripple factor (RF)  is the measure of ripple RF=VacVdc, where Vac=V2L+V2dc. Making several mathematical simplifications RF=(VLVdc)21=FF21=0.482.

Transformer utilisation factor (TUF) is a transformer merit measure TUM=VdcIdcVSIS where VS and IS are rms voltage and rms current ratings of secondary transformer. Where for full-wave transformer IS=0.707VmR .

Reader must note that only half-wave rectifier with resistive load produce harmonic currents in their transformers.

Datasheets of industrial single-phase full-wave diode rectifiers contain following important parameters:

  • Peak repetitive reverse voltage VRRM;
  • Ripple factor;
  • RMS input voltage per transformer leg VS;
  • Diode average current IF(AV);
  • Rectification ratio;
  • Output ripple frequency fr;
  • Peak repetitive forward current IFRM;
  • Transformer rating primary VA;
  • Diode RMS current IF(RMS) ;
  • Form factor;
  • Transformer rating secondary VA;
  • Form factor of diode current IF(RMS)IF(AV).

For instance, Digi-Key Electronics offers great range of single-phase full-wave and bridge rectifiers.