# How to calc Efficiency Of Boost Converter n its relatations

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#### mengghee

##### Full Member level 3 Hi, I am currently designing a boost topology with a feedforward control, i am just wondering if anybody knows how i can calculate the efficiency and also how do i estimate the loss in the mosfet or what affects the efficiency. thank you very much

#### huojinsi

##### Full Member level 5 Re: How to calc Efficiency Of Boost Converter n its relatati

The efficiency η=Po/Pin=Po/(Po+Ploss).Ploss is very complex,and it is relation with the Rds,D,f,Io,etc,and Ploss includes conduction losses,switch losses. i also know very little!

### mengghee

points: 2

#### scottieman

##### Full Member level 2 Re: How to calc Efficiency Of Boost Converter n its relatati

mengghee said:
Hi, I am currently designing a boost topology with a feedforward control, i am just wondering if anybody knows how i can calculate the efficiency and also how do i estimate the loss in the mosfet or what affects the efficiency. thank you very much
Sorry that I am not helping you here.
Still I am curious to know how feedforward control can be done in boost converter?

If it is not related to any IP issue, do you mind sharing it with us here?

Thanks
Scottie

#### mengghee

##### Full Member level 3 Re: How to calc Efficiency Of Boost Converter n its relatati

I am implementing it by taking the line input, feed it to a potential divider, and the potential divider is compared with a sawtooth waveform determining the pulse width.

#### rockycheng

##### Member level 5 Re: How to calc Efficiency Of Boost Converter n its relatati

Are you testing the real chip, or doing simulation in EDA? If it's EDA, there is a simple method. You can use a voltage source as the input voltage, so you know Vin (or Vg). And it is possible to get the rms value in steady state of output voltage (Vo), load current (Io), and the current flowing out of the voltage source (Iin). So you can calculate the efficiency η = (Vo*Io)/(Vin*Iin).

I think this way is theoretically correct.

• Ahmed Abd El Wahab

points: 2

### Ahmed Abd El Wahab

points: 2

#### mengghee

##### Full Member level 3 Re: How to calc Efficiency Of Boost Converter n its relatati

what do you mean EDA ? and yes i can get the input voltage in simulation. i am going to simulate it and build it soon ... but i don't understand the rms part .. what should i get ? i am a newbie .... sorry and thank you very much ...

#### rockycheng

##### Member level 5 If you do simulation with Cadence, you can use the "rms" function of calculator. "rms" means root mean square.

• Ahmed Abd El Wahab

points: 2

### Ahmed Abd El Wahab

points: 2

#### mengghee

##### Full Member level 3 Re: How to calc Efficiency Of Boost Converter n its relatati

But I don't know how to simulate it using cadence, I am using PSpice to simulate it. I am just wondering if there is a formula or if you do have some links about it. thank you .

#### rockycheng

##### Member level 5 mengghee,

I'm not familiar with PSpice. But I think you can use this method. There should be some corresponding commands in PSpice to implement.

#### mengghee

##### Full Member level 3 Re: How to calc Efficiency Of Boost Converter n its relatati

But I thought In a DC circuit. we shouldn't be bothered to much about RMS values... isn't that true ? thank you

#### zenisle

##### Full Member level 2 I suggest you try some common stracutre

#### mengghee

##### Full Member level 3 Re: How to calc Efficiency Of Boost Converter n its relatati

what do you mean by common structure ? thank you

#### rockycheng

##### Member level 5 Re: How to calc Efficiency Of Boost Converter n its relatati

mengghee said:
But I thought In a DC circuit. we shouldn't be bothered to much about RMS values... isn't that true ? thank you
Actually the output voltage and current are not DC value. They have ripples. But I think you can also get a roughly correct result, if you just use their required value instead. As to the total current through the voltage source, you should use the average value, because it changes dynamically.

### mengghee

points: 2

#### huojinsi

##### Full Member level 5 Re: How to calc Efficiency Of Boost Converter n its relatati

Hi mengghee:
If u are doing a simulation, no matter using pspice or cadence tool,the output voltage or current wave should be as the shape of picture, it has ripple wave and is not true DC voltage. At the steady-state, the out voltage or current wave look as if a sine wave, so u manualy calculate their averge value Io(av) respectively, the Po=Vo(av)*Io(av). Because the Vin and Iin is very easily obtained at the steady- state, u can calculate η=Po/Pin=Vo(av)*Io(av)/(Vin*Iin).
Hope it hepl u!

• Eshal

points: 2

### Eshal

points: 2

#### mengghee

##### Full Member level 3 Re: How to calc Efficiency Of Boost Converter n its relatati

Thank you Huojinsi, but i am just wondering how we should obtain the average value ? should it be calculated like V(av)= (Vmax-Vmin)/2 ?? sorry a bit dumb. and do you know anything about the power loss ? like switching loss, conduction loss etc. thank you very much

#### huojinsi

##### Full Member level 5 Re: How to calc Efficiency Of Boost Converter n its relatati

Thank you Huojinsi, but i am just wondering how we should obtain the average value ? should it be calculated like V(av)= (Vmax-Vmin)/2 ?? sorry a bit dumb. and do you know anything about the power loss ? like switching loss, conduction loss etc.
1. About average value, u can calculate it according to Vmax and Vmin of steady-state sine,V(av)=Vmin+(Vmax-Vmin)/2=(Vmax+Vmin)/2. ur formula V(av)= (Vmax-Vmin)/2 is a peak to peak value,and it doesn't include DC voltage value. Actually,this is a single estimate method,but it can estimate ur efficiency.
2. About the calculate of power losses, it is very complex and i also know quite little! Generally, for the calculate of efficiency, basically use the single formula η=Po/Pin=Vo*Io/(Vin*Iin).

Hope it help u. Pls correct me if i am wrong!

### mengghee

points: 2

#### edwintsu

##### Member level 4 Re: How to calc Efficiency Of Boost Converter n its relatati

1:Calc efficiency. Do tran sweep by changing current load(using step-function signal), and then measure steady state v(rms), i(vin).
2:Power loss Reference.
B. Arbetter, R. Erickson and D. Maksimovic, “DC-DC Converter Design for Battery-Operated Systems,” 26th Annual IEEE Power Electronics Specialists Conference, Vol 1, 1995, pp.103–109.
J. Stratakos, “High-efficiency Low-Voltage DC-DC Conversion for Portable Applications,” UCB,Ph.D.Thesis,1998.

Hope it help u!

### mengghee

points: 2

#### sumitj

##### Newbie level 6 Re: How to calc Efficiency Of Boost Converter n its relatati

hi

to know mathematical analysis of calculating efficiency you can refer to paper titled
" A comprehensive power analysis and a highly efficient, mode-hopping dc-dc converter"

In this paper one section explains power analysis of dc-dc converters

#### powerguy

##### Newbie level 2 Re: How to calc Efficiency Of Boost Converter n its relatati

mengghee said:
But I don't know how to simulate it using cadence, I am using PSpice to simulate it. I am just wondering if there is a formula or if you do have some links about it. thank you .
i am working on dc-dc converters and want to simulate on spice or cadence.
can you please tell me which library is used in spice.and which version of spice is used.

#### sw0ws1

##### Junior Member level 1 Re: How to calc Efficiency Of Boost Converter n its relatati

edwintsu said:
1:Calc efficiency. Do tran sweep by changing current load(using step-function signal), and then measure steady state v(rms), i(vin).
2:Power loss Reference.
B. Arbetter, R. Erickson and D. Maksimovic, “DC-DC Converter Design for Battery-Operated Systems,” 26th Annual IEEE Power Electronics Specialists Conference, Vol 1, 1995, pp.103–109.
J. Stratakos, “High-efficiency Low-Voltage DC-DC Conversion for Portable Applications,” UCB,Ph.D.Thesis,1998.

Hope it help u!
PLease i dont understand how to use step function to change current load??and can this be done by changing Rload??
anthor qes: when i press (print )in cadence calculator,it ask me to enter a value to print at .so which value it wants??