Drobnak is the founder and president of the Business Angels Club of Slovenia that he founded in 2007, which connects Slovenian startups with investors. The public knows him as the founder and director of the brokerage house Poteza, which he founded in 1992 when the investor market was still in its infancy.Now Drobnak is active in the company Arima and a member of the board of directors at Alta, recently acquired by the BKS bank. As a consultant, he advises several companies and is actively involved in the advisory boards of Businesses Acies Bio, X8 and Agencija za pospeševanje likvidnosti (APL).

As a business angel, Drobnak actively advises young entrepreneurs and invests in startups as an individual or in collaboration with other business angels. His previous investments include companies such as Acies Bio and Double Recall.