Figure 4: Waveforms for sequence 1

Sequence 2Operation

In this sequence, the converter operates in third and fourth quadrant and the switch S₃ is permanently kept on . The switches S₁ and S₂ are controlled as per the following four steps:

• • Mode 1: S₂ is turned on at t = 0 but starts conduction only when the current changes sign. The diodes D₂ and D₃ conduct (Figure 5a) till the current changes itrs sign. The instantaneous output voltage across the load is .

• Mode 2: When S₂ is turned off at , the inductor continuous to drive the current in the reverse direction through S₃ and D₁ ( Figure 5b ).

• Mode 3: The switch S₁ is turned on at but does not conduct because the current flows in the negative direction and D₁ and S₃ conduct. Once the current changes the sign S₁ and D₃ conduct D₁ (Figure 5c).

• Mode 4: When S₁ is turned off at t = T , but positive current flows, hence, D₂ and D₃ conduct D₁ ( Figure 5d ).