Other Parts Discussed in Thread: LM3481
I've got the LM3481-FLYBACKEVM to use it as a testplatform for a LM3481-based Fyback-powersupply.
I changed the following parts: R13 from 162k to 105k (new switching frequency: 200 kHz)
R16 from 3.83k to 1k (new output voltage: 5 V)
T1 : Np:Ns (primary to secondary) = 11:14
Lp = 19 µH, ER11/5-Core, N87
The powersupply should deliver 1.5 W at the output. However at 700 mW the LM3481 starts to oscillate at the DR-Pin, the core
of the transformer saturates than too (see the screenshots from measurement). The duty-cycle of the PWM-Signal for the range from 0 to 700 mW is shown below.
Below there are some screenshots from measurements of the following signals:
CH1: LM3481:DR (PWM switching signal)
CH2: Rsense (sensed Primary current)
CH3: LM3481:COMP (output voltage feedback)
CH4: uds (drain source voltage of switching Transistor)
regards
Adam