Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Boost Converter Output Voltage When Duty Cycle is 0.9

Status
Not open for further replies.

mengghee

Full Member level 3
Joined
Nov 29, 2005
Messages
164
Helped
8
Reputation
16
Reaction score
5
Trophy points
1,298
Location
United Kingdom
Activity points
3,112
I have attached a schematic diagram of my circuit and also a graph plotted on Duty Cycle Vs Vout. In the graph, it shows that when my duty cycle increases to 0.9, the output voltage is lower than the output voltage when the duty ratio is 0.8. how can that be possible ? can anybody tell me why that happens ? and if that happens, how should i prevent it ? thank you.


thanks,
mengghee
 

eecs4ever

Full Member level 3
Joined
Jan 31, 2006
Messages
179
Helped
28
Reputation
56
Reaction score
10
Trophy points
1,298
Location
Analog Environment
Activity points
2,852
Here is how this boost converter works:

Phase 1:
When V1 is High, M1 turns on, pulling the voltage at node 2 low.
This reverse biases the diode and isolates the two halves of the circuit.
During this phase, the current going through the inductor increases, and additional
energy is stored in the inductor in the form of magnetic flux.

The output voltage / current is supplied by the Capacitor during this phase.

Phase 2:

V1 goes low. M2 turns off. node 2 increases in voltage, and the diode D2 becomes foward biased. The energy from the 5 volt Vdc and the energy stored in the inductor is injected to the right half of the circuit, causing the voltage to rise beyond 5 V.



Now to answer your question, if the Duty Cycle is too close to 1. Then there will be very little time for the Inductor to inject its energy to the right half of the circuit. and Vout will drop.

Thats my best guess.
 

    mengghee

    points: 2
    Helpful Answer Positive Rating

Davood Amerion

Advanced Member level 2
Joined
Mar 1, 2005
Messages
584
Helped
116
Reputation
232
Reaction score
24
Trophy points
1,298
Location
Persia
Activity points
6,351
Dear Mengghee
In boost convertor as opposed to step down convertor output voltage is not proporational to duty cycle.
This config usualy used maximum 50% duty cycle.
why?
1- because output voltage is not depend on duty cycle.
it is better to say that output power is proporational to duty cycle.

2- in phase 2 (transistor off) inductor must enough time to disharge its energy to output circuit via D2.
this time is not fix , and depend on output voltage. for greater voltage this time will reduced.

for example, you can check with (say) 200 ohm, for R8. you will see Vo/DC curve improved significantly.

Regards,
Davood Amerion.
 

    mengghee

    points: 2
    Helpful Answer Positive Rating

praveenkumar

Newbie level 1
Joined
Feb 11, 2006
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,288
using resonant converter how can we buck and boost the output voltage for the ups technology?
 

narccizzo

Full Member level 3
Joined
Jan 20, 2006
Messages
174
Helped
16
Reputation
32
Reaction score
11
Trophy points
1,298
Location
PATZCUARO,MICHOACAN,MEXICO
Activity points
2,819
using resonant converter how can we buck and boost the output voltage for the ups technology?


i dont really understand the question
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top