Flyback design question
Flyback design question
(OP)
Hi all,
I've just received this flyback SMPS schematic for a on-field power supply. Please find the link below:
http:// files.engi neering.co m/getfile. aspx?folde r=b5204258 -897d-4bce -879e-1b2e fa7b8b6e&a mp;file=Fl yback1.gif
I'd appreciate any help finding any design flaws. Creative suggestions or enhancements are of course welcome.
Regards,
GonzaloEE
I've just received this flyback SMPS schematic for a on-field power supply. Please find the link below:
http://
I'd appreciate any help finding any design flaws. Creative suggestions or enhancements are of course welcome.
Regards,
GonzaloEE





RE: Flyback design question
Your converter is not a flyback...yours has primary and secondary conducting together.
It's some sort of forward converter but i think your secondary parallel diode should be on the other side of the series inductor (ie nearer the secondary winding).
I am trying to see how you are de-fluxing the core after switch off.
Could you give your output voltage and Watt rating?
RE: Flyback design question
Sec. windings could be in series or parallel to allow those output voltages. Here they are shown in parallel for 12V mode.
Seems like fine Vout adjustment is done by the TL431 V reference along with R8,R10,R11 and Radj pot. I'm checking that setup in the datasheet.
I'm also missing some free-wheel diode for core de-fluxing. Looks like that snubber network at top of secondary (R6, C6 at top) is the only way back for current when the Schottky goes off. I'm trying to contact the designer.
I'm not a power electronics expert, so I just hired a freelance designer for the job.
Thank you for your guidance!
RE: Flyback design question
D7 appears to be for a secondary battery supply.
RE: Flyback design question
As a side comment, this circuit is badly and non-standardly drawn, with ground going across, up and around all over the place. It also has a 4-way interconnect, which was deemed unacceptable over 30 years ago.
RE: Flyback design question
4-way interconnect?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Flyback design question
I'm guessing that the "Y" is for an
safety agency approved Y-cap.
I've been told it helps cancel the primary
to secondary capacitance of the transformer.
RE: Flyback design question
>4-way interconnect?
The anode end of D5 has a 4 way junction on the circuit. The older drawing convention was to draw little humps to cross over wires. Then they changed it so that you could drive straight across without the humps PROVIDED you never joined 4 wires at point. Joining 4 wires by making a bold blob at that point was considered bad form because you used to get blobs on the old dyeline prints (showing my age here I suppose).
RE: Flyback design question
They also often look like swastikas. LOL
Thanks, logbook.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Flyback design question
BTW, do you know any replacements for the TOP246Y switcher, or ferrite Xformer suppliers? Management here is planning a long-term supply contract with our client, so I'm prepared for non-stocked parts through the next months.
Thanks in advance!
RE: Flyback design question
Any suggestions on this issue are welcome!
RE: Flyback design question
There's probably some type of power management IC initially designed for laptop use that would do the battery charging and backup for you.
RE: Flyback design question
CY4 is a ceramic HV disc cap, same like those from the input EMI filter. As the design is for a non-US/EU client, you'll find there's no PF correction stage.
I don't like much the idea of having the battery warming-up the board through D7/R12 when mains is off. That's why I'm looking for some non-resistive approach.
Thanks Lionel for that lead on laptop batt. management ICs. Any suggestions are welcomed, of course.
Regards,
Gonzalo