When you backup your dictionaries (.ld2) in Lingoes program, a .ldb backup is generated and saved to selected folder. This is not much of conversion, but more like a standard function of the program. You can of course restore the backups back to replace dicitionaries.
Convert Lingoes compiled dictionary file to Lingoes backup file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert ld2 to ldb on Windows
A dictionary and text translation program
Convert from ld2 file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.