Series connection means a side by side connection. When two components are connected in series, they have one common junction. The variation of voltage and current in a series connection is as follows: • Potential difference across every component is different.
• The current across every component connected in series remains the same. The same properties also hold true for diodes when they are connected in a series configuration.
Diode Characteristics in Series Configuration
When connected in series, we observe the following properties to hold true among the diodes:
• Resultant diode’s forward voltage increases
• Reverse blocking capabilities of diodes are increased in series connection
Consider two diodes connected in series. The thing to be kept in mind over here is that all the diodes connected in series won’t have the same characteristics as shown in the graph below.
V-I characteristics show that the diodes have different blocking voltages. In forward biased state, the voltage drop and the forward current would be same on the diodes. While in the reverse biased the blocking voltage is different as the diodes have to carry the same leakage current.
This problem can be solved by connected resistances across every diode. Voltage would be shared equally; hence the leakage current would differ.
Total leakage current would now be:
IS = IS1 + IR1
= IS2+ IR2
Our requirement is: VD1 = VD2
We know, IR1 = VD1 / R1 and IR2 = VD2 / R2
so we get
IS1 + (VD1 / R1) = IS2 + (VD2 / R2)