DC12V to DC28V Converter with LM2585

This circuit is boost regulator,
input volt DC12V for output DC28V (28v relay)
The circuit is built around the LM2585,
and uses the energy stored in an inductor to boost the 12v to 28.
The circuit does it’s switching around 100 Khz,
but generates no noise if SMT components are used.
…

Note

1. A short-circuit on the output will kill U1 and D1. Always use a 1 ohm 5w resistor,
or a 2.5A fast fuse on the 12v input lead.
2. Do not omit the LED (D2); It provides a visual indicator of a properly operating boost condition,
but more importantly, it also provides a minimum load for the output,
preventing an output “spike” which will otherwise
appear when the load is disconnected abruptly.

3. Keep the ratio of r2 and r3 to 22 or less to keep the output voltage
within the ratings of C4 (C4 on my board is rated at 35wvdc).
This ratio plus 1, multiplied times 1.25v, determines the output voltage.

Source: http://www.w6pql.com/12_to_28v.htm

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