ICE3BR0365 Datasheet, PDF (14/16 Pages) Infineon Technologies AG – Design Guide for Off-line Fixed Frequency DCM Flyback Converter

DCM Flyback
Design Note DN 2013-01
V1.0 January 2013
*Note; The load on the auxiliary winding is usually just the IC bias and MOSFET gate drive (~0.1A)
STEP 11: Transformer Construction and Winding Design Iteration
Using table AWG 29 diameter is 0.389mm, EE 20/10/6 winding area width and
height is 14mm and 4mm respectively. This will give us a TPL (turns per layer)
on the primary of 35Turns (14/0.389). For our required 66 turn we will need 2
layer on the primary winding.
For the secondary turns we will use triple insulated wire AWG 22, outside
diameter is 0.947. TPL fusing this wire is 14 turns (14/0.947) which means a
single layer 11 turns would fit in. For the auxiliary basic AWG 34 magnet wire
will be used (d=0.262mm).
Checking the winding stacked (0.389mm+0.389mm+0.947mm+0.262 ) is 2mm
which is less than the winding height. This should give us enough margin for the
actual build. We can then used a split primary transformer construction as shown in Figure 11.
STEP 12: Design the primary clamp circuit: For the primary clamp we will used a Diode-Zener clamp TVS
Diode is P6KE160 and fast recovery diode is BYB27C. An RCD clamp value can also be used as suggested on
reference design on [2]
STEP 13: Output Rectifier Diode Selection: Voltage and current rating for the schotky rectifier diodes are:
Choose 100V rated diode
STEP 14: Output Capacitor Selection
Choose IF>5.9A
Capacitance must be at least equal or higher
than this value
For Flyback output capacitance most of the time the limiting factor is the ripple current rating and ESR .
The combined RMS current rating of the output
cap(s) used should be higher than this value
Choose a combined paralleled
ESR lower that this value
14