Graetz bridge
Graetz bridges are bridge rectifiers. In this electronic bridge circuit ofdiodes, the positive and negative phases of an AC voltage signal are used for rectification, resulting in a rectified half-wave signal.
The Graetz bridge is constructed in such a way that for each half-wave of the AC voltage, two diode paths open and thus allow the half-wave to pass. If the positive half-wave is at the anode of diode D3, then the negative half-wave is simultaneously at the cathode of diode D2. Diode D3 lets the voltage through to the downstream filter circuit when the anode is positive, diode D2 switches the negative half-wave to ground. For the next half-wave, the positive voltage is at the anode of diode D4, which lets it through to the filter circuit, and the negative voltage is at the cathode of diode D1. This again closes the circuit.
At each half-wave, two diodes are always active and generate a half-wave current flow with double the mains frequency.