- It is a chopper which can work as step up chopper as well as step down chopper.
- When the chopper is switched ON during TON time, the energy stored in the inductor via path Vdc – CH – L – Vdc.
- The direction of current passing through inductor is shown in the figure B when the chopper CH is switched on.
- When chopper is switched OFF during TOFF time, the current passing through inductor is zero and voltage across inductor is L ( di/dt ).
- As the direction of voltage polarity across
inductor changes, the stored energy of inductor dissipates via path L – LOAD –
D – L.
- When chopper is switch ON, the energy stored in the inductor is
Wi = Vdc
I TON.......................(1)
- When chopper is switched OFF, the output energy
Wo = VoI
TOFF......................(2)
- The input energy is equal to output energy when there are no losses in the system. Therefore from equation ( 1 ) and ( 2 )
Vdc I TON =
VoI TOFF
Vo = [ TON / TOFF ]
Vdc
OR
Vo = [ TON / ( T – TON ) ] Vdc
Vo = [ 1 / ( T / TON – 1 ) ]
Vdc
Vo = [ 1 / ( 1 / K – 1 ) ] Vdc
Where K = Duty cycle = TON
/ T
Vo = [ K / ( 1 – K ) ] Vdc
The chopper works as
step down chopper if 0 < K < 0.5
Vo < Vdc
The chopper works as
step up chopper if 0.5 < K < 1
Vo > Vdc
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