AN2450 datasheet(23/35 Pages) STMICROELECTRONICS

23 / 35 page

DocID12784 Rev 6

23/35

AN2450

Design procedure

Based on the analysis presented so far, a step-by-step design procedure of an LLC

resonant converter is now proposed, which fulfills the following design specification and

requires the additional information listed below:



Design specification:

–

Input voltage range: Vdc.min - Vdc.max

–

Nominal input voltage: Vdc.nom

–

Regulated output voltage: Vout

–

Maximum output power: Pout

–

Resonant frequency: fr

–

Maximum operating frequency: fmax



Additional info:

–

Parasitic capacitance at node N: Czvs

–

Dead time of driving circuit: TD



General criteria for the design:

–

The converter will be designed to work at resonance at nominal input voltage.

–

The converter must be able to regulate down to zero load at maximum input

voltage.

–

The converter will always work in ZVS in the whole operating range.



10 step procedure:

–

Step 1 - to fulfill the first criterion, impose that the required gain at nominal input

voltage equals unity and calculate the transformer turn ratio:

Equation 54

–

Step 2 - calculate the max. and min. required gain at the extreme values of the

input voltage range:

Equation 55

Equation 56

Mnom

Vout

Vdcnom

-------------------

---

Vdcnom

Vout

-------------------



Mmax

Vout

Vdcmin

------------------

Mmin

Vout

Vdcmax

-------------------

AN2450 Datasheet(PDF) 23 Page - STMicroelectronics

AN2450 Datasheet(HTML) 23 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35

Datasheet Download

Link URL