Patent ID: 8269421

Claim:
An electronic ballast for a gas discharge lamp, comprising: a first dc-to-dc switching power supply stage having a dc voltage input, a dc voltage output, and a storage capacitor coupled to said dc voltage output; a second dc-to-ac switching power supply stage having a dc voltage input coupled to said dc voltage output of said dc-to-dc switching power supply stage and an ac voltage output for driving said lamp; wherein said electronic ballast includes a single controlled active switch shared between said dc-to-dc switching power supply stage and said dc-to-ac switching power supply stage; and wherein said first dc-to-dc switching power supply stage includes a coupling capacitor coupled in series between said dc voltage input of said dc-to-dc switching power supply stage and said storage capacitor, said coupling capacitor having a capacitance of less than half a capacitance of said storage capacitor.