half bridge converter transformer design help

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!

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.

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

Click to expand...

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.

FvM said:

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.

Click to expand...

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?

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

FvM said:

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

Click to expand...

hi
here is the circuit

aruna1 said:

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

Click to expand...

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....