Feedback Gain for Adjustable Outputs
Posted by: aliaykan
on
Hi,
How can I set feedback opto gain for adjustable outputs? Instead of directly connect the gain resistor to output, fixing the gain resistor's voltage via zener is useful like attachment?
Requirements:
3-25V / 10A output by Flyback
3-25V / 18A output by LLC
Files
Attachment | Size |
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Fixed Bias.jpg | 169.49 KB |
Yes it's a good idea but you may need to add a phase lead network, a series RC, from the output to the top of the opto LED.
Also 3 V is pretty low; you'll have to use either a TLV431 (1.25V), or have a separate winding from the transformer. For the flyback, a "forward" winding. Its voltage will vary less than 3-25V. For the LLC, a winding wound on the primary.
Also, note that an LLC running from 3-25V output voltage will have issues with making the feedback loop fast and stable across the wide ratio of input to output votlage as Vo goes from 3-25V. It helps to always make it run above resonance. However efficiency won't be so good.