Tools

Performance Measurement and Analysis of Non-isolated DC-DC Boost Converter

Theory

The circuit configuration of boost converter is given in Fig. 1

Fig. 1 Circuit configuration of Boost Converter.


Based on the operation of switch (Sw: ON/OFF-state) the operating principle of the converter is explained below briefly.

Mode – I : Switch (Sw): ON and Diode (Di): OFF


Fig. 2(a). Equivalent circuit in mode-I.

Mode – II : Switch (Sw): OFF and Diode (Di): ON


Fig. 2(b). Equivalent circuit in mode-II.


a) Voltage conversion ratio or voltage gain (M)

Voltage across inductor L:

Mode – I :

..(1)


Mode – II :

..(2)


Applying volt-sec balance on inductor (eqn. 1 and 2)

..(3)



On simplifying the eqn. 3

..(4)


b) Average current through inductor (IL):
Current through capacitor

Mode – I :



..(5)



Mode – II :

..(6)



Applying charge-sec balance on capacitor (eqn. 5 and 6)

..(7)


On solving eqn. 7

..(8)


c) Power balance under ideal condition (neglecting losses):

From Fig. 1, the source current itself is the inductor current and hence


..(9)


Simplifying eqns. 8 and 9 gives the current gain

..(10)


From eqns. 4 and 10

..(11)


Hence under ideal condition, the power drawn from the source is equal to power supplied to load.



..(12)


d) Inductor current ripple:

From eqn. 1,


..(13)


Therefore, the inductor ripple current is

..(14)




e) Current through various components:

The current through various components are given in Fig. 3.

Fig. 3. Current through various components.


  Mode-I
(DT) 		Mode-II
(1-D)T 		Average Current
imin imax imin imax Iavg
iL
iC 0
iSw 0 0
iDi 0 0


f) Voltage and current stress on various components:


Component Voltage stress Current Stress
Inductor (L)
Capacitor (C) V0
Switch (Sw) V0
Diode (Di) V0


g) Efficiency analysis:


..(15)


..(16)


The power loss occurring in various components are given below.

Power loss in inductor:


..(17)


Power loss in capacitor:

..(18)

Power loss in switch:


..(19)


Power loss in Diode:

..(20)

Total power loss:


..(21)




h) Effect of non-idealities on voltage gain expression:



Fig. 4. Circuit configuration of conventional boost converter with non-idealities.


Based on the operation of switch (Sw: ON/OFF-state) the operating principle of the converter is explained below briefly.



Voltage across inductor L

Mode – I :


..(22)


Mode – II :


..(23)


Applying volt-sec balance on inductor (eqn. 22 and 23)

..(24)

Therefore, voltage gain of non-ideal boost converter is


..(25)

("For more Information on mathematical analysis, see references")