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Stabilized DC power supply with Graetz bridge and linear voltage regulator.

Monophase DC power supply with Graetz bridge, stabilized output.

Dimensioning of DC power supply with stabilized output and linear voltage regulation, full wave rectifier with silicon Graetz bridge and leveling capacitive filter.
The stabilizer can be any of the linear IC stabilizer (not switching) with fixed or regulable output voltage or also a circuit made by discrete components.

Data input
Transformer data (nominal values).

Nominal voltage of the PRIMARY winding

V ac NOM

Nominal voltage of the SECONDARY winding

V ac NOM

Transformer nominal power


Supply frequency.

50 Hz (sinusoidal)

60 Hz (sinusoidal)

Leveling capacitors data.

Total capacity of the filter . . . C


Define automatically an appropriate capacity
based on the above data

Wait value.
Characteristics of the voltage regulator (stabilizer).

Minimal admitted voltage difference between input and output of the regulator.
(e.g. 78XX, LM 317 = 0.6 - 1.7 V)

The voltage drop generated by the regulator is variable, increases with the load.
Depends on its internal resistance.


Working point of the power supply.

Real supply voltage:


V ac EFF

Real applied load:




Required stabilized output voltage:


Wait calculate.
Transformer :
Theoretical transformation ratio
Percentage of characteristic voltage drop at the nominal transformer power %
Secondary no-load voltage with real applied supply voltage V max
Voltage drop on the secondary winding related to the applied load V ac
Real output voltage of the secondary relative to the applied load V ac EFF
Secondary peak-to-peak voltage relative to the applied load V PEP
Rectifier + filter capacitors :
Rectified voltage related to the applied load Vp
RMS Rectified voltage related to the applied load V EFF
Output ripple related to the applied load and to the filter capacity choosed Vrpp
Real usable voltage by the voltage regulator (stabilizer) Vp - Vrpp - Vreg. Vu
Rectifier considered voltage drop V
Minimal dispersed power by the rectifier (bridge) with the applied load W (diodes)
Voltage regulator (stabilizer) :
Miminum required voltage in input by the stabilizer. For the correct functioning it must be lower than the Vu. Vmin
Minimum power dispersed by the stabilizer with the applied load W (reg)
Various :
Maximum global efficiency of the power supply with the applied load %

Voltage drop on the secondary caused by the load can change in function of construction or designing of the transformator itself.

The no-load output voltage of the transformator is obtained summing the expected drop at the maximum power at the nominal voltage. Pratically the output voltage at the nominal power will be equals to the nominal voltage.

The output ripple (Vrpp) can change in function of the quality of the used capacitors.

The ripple value (Vrpp) is made reasonably valid up to 50% of V RMS, beyond this value the inaccuracy increases.

Normally a supply must be able to work correctly with supply voltages which can change at least of +/- 10% respect to the nominal or the project value.

The voltage difference between the input and the output of the stabilizer depends on the kind of circuit and on the numer of junctions interested by the current passage. It is a value that increase with the increasing of the load, for example on a 7805 with maximum admitted current is 2 V.

The power dissipated by the regulator is what You have to consider when you design the heat sink.

To obtain the minor possible ripple on the stabilizer output is necessary that the minimum ripple voltage in input is never lower than Vmin.

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The applications for powersupply.

Not stabilized,
rectifier 1 diode.
Not stabilized,
rectifier 2 diodes.
Not stabilized,
bridge rectifier.
bridge rectifier,
linear voltage regulator.
  • Powersupply half-wave.
  • Powersupply full-wave.
  • Powersupply bridge rectifier.
  • Linear stabilized powersupply.