DC Power Supply 3

AC to DC CONVERSION (RECTIFIER)

•Single-phase, half wave rectifier

–Uncontrolled: R load, R-L load, R-C load

–Controlled

–Free wheeling diode

•Single-phase, full wave rectifier

–Uncontrolled: R load, R-L load,

–Controlled

–Continuous and discontinuous current  mode

•Three-phase rectifier

–uncontrolled

–controlled

Single-phase, half-wave, R- load

 

 
 
Half wave rectifier, R-C load
 
 


 Controlled half-wave

 

Controlled half-wave, R-L load

 

Freewheeling diode (FWD)

•Note that for single-phase, half wave rectifier with R-L load, the load (output) current is NOT continuos.

•

A FWD (sometimes known as commutation diode) can be placed as shown below to make it continuos

  
 Operation of FWD

•Note that both D1 and D2 cannot be turned on at the same time.

•For a positive cycle voltage source,

–D1 is on, D2 is off

–The equivalent circuit is shown in Figure (b)

–The voltage across the R-L load is the same as the source voltage.

–

•For a negative cycle voltage source,

–D1 is off, D2 is on

–The equivalent circuit is shown in Figure (c)

–The voltage across the R-L load is zero.

–However, the inductor contains energy from positive cycle. The load current still circulates through the R-L path.

–But  in contrast with the normal half wave rectifier, the circuit in Figure (c) does not consist of supply voltage in its loop.

–Hence the “negative part” of vo as shown in the normal half-wave disappear.