Power Diode Series and Parallel Connection

Power Diode Series Connection and Parallel Connection

When the power electronic system designed with high power ratings, each and every power semiconductor devices (like power diodes, SCRs etc) have to meet the voltage and current requirements.
In some scenario, the demand for voltage and current ratings is so high that a single device cannot meet such requirements.
In such cases, the power semiconductor devices are connected in series manner to meet the high voltage requirement and in the parallel manner to meet the high current requirement.

In this post let us focus on series and parallel connection of the Power diodes only.

Power Diode Series Connection:

For some industrial applications, when the voltage or current rating of the selected diode is not enough to meet the designed rating, the diodes can be connected in series or parallel.

  • To meet the high voltage requirement, the diodes have to be connected in series manner.
  • But while Connecting the diodes in series, we should ensure that the diodes are properly matched especially in terms of their reverse recovery properties.
  • Otherwise, large voltage imbalances between the series connected diodes will occur during reverse recovery process.
  • In addition to that, some diodes may recover faster than others.
  • This will cause the slow recovery diodes bear the full reverse voltage for a significant amount of time.
  • These kind problems can be eliminated by connecting a capacitor and a resistor in parallel with each power diode as shown in the following figure.Power_diode_series_operation

Parallel Connection of Power Diode:

  • To meet the high current requirement, the power diodes have to be connected in parallel manner.
  • While connecting diodes in parallel, we should ensure the equal current sharing among the diodes.
  • To achieve equal current sharing we should select diodes with the same forward voltage drop properties.
  • In addition to that, the diodes have to be mounted on similar heat sinks, so that the cooling process will happen equally.
  • Remember that forward characteristics of diode is will vary with the device temperature.

In a short word,
Series Connection --> Reverse Recovery properties
Parallel Connection --> Forward voltage drop properties

You May also like to read:

SCR Series Operation Tutorial 
SCR Parallel Connection 
Diode Power Loss Calculation 
Power Diode - An Introduction 

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