LNK3206GQ buck converter 5V
Hi I am trying to design a buck converter which operates from 60V to 550V with output of 5V and 200mA load current.I have few questions while referring the availabe documentation with the LNK3206GQ:
- Some documents site to a minimum input voltage of 30V , is it possible to reduce the input voltage down to 30V
-
Linkswitch App note:an-70_linkswitch-tn2_design_guilde.pdf (power.com) page 6 suggests Feedback diode forward drop should match with the freewheeling diode voltage drop.Does that mean if i use two diodes of 1.5V in series in the freewheeling part , i will have to find a feedback diode with voltage drop close to 3V, some of the ref designs in the PI websites itself doesnt follow this.der-965q_10w_non-isolated_buck_power_supply_for_400v_systems_using_linkswitch-tn2q.pdf
In the above design the Vf of the freewheeling diodes and the Feedback diode is 1.7V , but two diodes are used in series to the freewheeling , while only one used in the feedback section
Is my understanding correct?
评论
Attached the design calculation in the PI Expert , the feedback resistors acc to the spreadsheet is 2.49K and 5.49K , whereas the Fig22 in the application note also shows a 5V converter , but here the FB resistrs are 2.49K and 3.83K , why this difference?
| Attachment | 大小 |
|---|---|
| LinkSwitch-TN2 Automotive Buck Design3_5V_Copy00.pdf | 474.45 KB |
Hi Sabah.vs
Good day!
- The lowest input guarantee for the LNKTNQ to operate is 30Vdc.
- The ideal case is the Freewheel diode and Feedback diode have the same Vf. But this is not a hard requirement. If this is not followed, you just need to check the regulation and adjust the upper resistor divider to provide the required regulation level based on your application.
We do not have LTspice model of LNK3206
For the PIEXPERT and App notes value are the base line value. Regulation will depend on the feedback diode and Freewheel diode Vf. I think this is the difference between your PIEXPERT and App Note document. I suggest you follow the PIExpert since you have entered the the freewheel and feedback diode Vf. You can trim the upper resistor to provide the required regulation.
Thanks
Regards
PI-CHLOE
Is there a LTspice model available for the LNK3206