Power supply

Return to the Index.

This model helps in the design of simple DC power supplies. In the example variable sheet below, the model is being used to predict the average dc output voltage Vdc and the ripple voltage that would be obtained with a specified transformer secondary voltage Vrms, half-wave rectifier, filter capacitor C, and load current Idc. Set wave = 0.5 for a half-wave rectifier, or wave=1 for a full-wave (bridge) rectifier. The output voltage regulation can be determined by calculating Vdc as a function of Idc). (Note: The equations used in this model are approximate and are reliable only for small ripple factors < 0.2. The model assumes a constant voltage drop across the rectifier diodes of 0.6 volts per diode). 

Variable Sheet
_________________________________________________________________________________
St Input     Name    Output    Unit      Comment
             Vdc     10.206667 volts     average dc output voltage (V,mV)
   10        Vrms              V         rms transformer sec voltage (V,mV)
   .5        wave                        .5 for half-wave, 1 for full-wave rectif
   40        Idc               mA        average output current (A,mA,µA)
   60        f                 Hz        Line frequency (Hz)
   100       C                 µF        filter capacitance (F, µF)
             r       .18855332           ripple factor (unitless ratio)
             Iac     7.5421328 mA        rms value of ripple (A,mA,µA)
             RL      255.16667 Ohms      load resistance (Ohms, KOhms)
             Vripple 1924.5009 mV        rms ripple voltage (V,mV)
             PL      .40826667 watts     Power dissipated in load resistance (wat

Rule Sheet
_________________________________________________________________________________
S Rule
  Vdc=1.414*Vrms-Idc/(4*wave*f*C)-1.2*wave "Approx eqn for average output voltage
  Iac=r*Idc                               "definition of ripple factor (current)
  r=1/(4*sqrt(3)*wave*f*C*RL)             "Approximate equation for ripple factor
  Idc=Vdc/RL                              "Ohms Law or load resistance
  Vripple=r*Vdc                           "definition of ripple factor (voltage)
  PL=Vdc*Idc                              "Joules Law for load resistance