Full-wave MOSFET rectifier design

 This design basically is a cut-down version of the MOSFET bridge rectifier presented recently.  Two p-channel MOSFETs and two opamp sections are used.  The n-channel MOSFETs and their two driving opamp sections were deleted.  Also the 12.6 VAC center tapped transformer was simulated with two 6.3 VAC (8.9 = 6.3 x 1.414) sources in series with their common connection grounded.

full wave MOSFET rectifier

As with the original bridge circuit and the half-wave circuit, the gate drive varies depending on the load. Here is the output from a lightly loaded supply (just the sampling resistors). 

lightly loaded full wave input-output-gate drive

The gate drives are off with just a little bit of "scratchiness" near the positive and negative input voltage peaks.  

 Here is the output simulation with a 100 ohm load: 

full wave rectifier with 100 ohm load

The gates are on for a longer period but cut off just after the peak input voltage.

The design might be made better by using the two n-channel MOSFETs instead of the p-channel since n-channel parts usually offer better performance at a lower price.  But the p-channel version corresponds better to a normal presentation of a full-wave rectifier.

Now with modern (often toroidal) transformers it is usually possible to either center tap an output (needed for a full-wave rectifier) or parallel the windings (for 2x the current but a bridge rectifier is needed).  If the best efficiency is desired the full-wave with only one rectifier in the loop is preferred to the bridge rectifier where 2 rectifiers are essentially in series.  

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm