half bridge converter transformer design help

[aruna1]

Hi
I have to design and built a half bridge converter with following specifications

Vin = 12V-24V
Vout=6V
Iout=4A

Can some one tell me how to calculate ad design required transformer.
I have no idea about this and no additional data is available..if some one can give me or point me to all equations required to design the transformer it would be a great help.
thank you

 

[randell_xtian]

Hi!

is Vin in DC mode or AC mode already? perhaps, the transformer can't work on DC voltages. If it is in AC voltage then the formula could be:

Vp/Vs = Ip/Is
Np/Ns = Vs/Vp

Vp - primary voltage
Vs - secondary voltage
Ip - primary current
Is - secondary current

Np - number of turns at primary side
Ns - number of turns at secondary side

Then you can now calculate and design the desire output voltage of your transformer.

 

[FvM]

Vp/Vs = Ip/Is
Np/Ns = Vs/Vp

Unfortunately both "formulas" are wrong.

A converter with variable input voltage and intended constant output must involve a method of voltage regulation, either by PWM at the primary or a separate secondary switcher. The selection of a suitable converter topology also affects the transformer dimensioning. So choose the converter topology first.

P.S.: A fullwave two-diode rectifier with an additional inductor would be a standard solution, requiring a center tapped secondary winding.

 

[aruna1]

Unfortunately both "formulas" are wrong.

A converter with variable input voltage and intended constant output must involve a method of voltage regulation, either by PWM at the primary or a separate secondary switcher. The selection of a suitable converter topology also affects the transformer dimensioning. So choose the converter topology first.

P.S.: A fullwave two-diode rectifier with an additional inductor would be a standard solution, requiring a center tapped secondary winding.

well i know that infact i know how topology works.I can adjust pwm to make output constant.
my question is how to cal culate transformer with info I have. topology input is 12-24V DC so needs to calculate transformer parameters.
can you please help me with this?

 

[FvM]

I don't think, that the topology is clear from the specification up to now. You should show the intended circuit.

 

[aruna1]

I don't think, that the topology is clear from the specification up to now. You should show the intended circuit.

hi
here is the circuit

 

[ravslanka]

Hi
I have to design and built a half bridge converter with following specifications

Vin = 12V-24V
Vout=6V
Iout=4A

Can some one tell me how to calculate ad design required transformer.
I have no idea about this and no additional data is available..if some one can give me or point me to all equations required to design the transformer it would be a great help.
thank you

hi aruna,

for calculating pri turns

npri=vin min x10^8/kxfxbxae

vin min=12 volt (since half brdge vin/2)

k=4 for sine wave k=4.4

f=frequency of transformer i hertz

b=flux density of material you are going to use in guass (n97,3c94....)

ae=effective cross section are of core you are going to use in cm2 (eg etd 29 =76mm2 or 0.76cm2)

so for your requirement using 3c94 material, etd29 core, flux density =1600guass

=(12/2)x10^8/4x20000x1600x0.76

=6.16 turns or 16 turns

maximum primary current

power output=ioxvo

=4x6=24 watt

max primary current=po/vin min

=24/12=2ampere

for sec

nsec=nprxvox1.1/vin min x dc max (max duty cycle)

=16x6x1.1/6x0.90

=19.55 or 20 turns


regards

ravs

be a vegeterian....