Ballast a high pressure discharge lamp, comprising: - a DC converter (20) which is designed such that it receives an input DC voltage from a DC voltage source (10), wherein the DC-DC converter includes a switching element (24) which is driven so that it switches the input DC voltage repeated to a variable DC output to provide, applied for driving the discharge lamp; - a control device (70) which monitors the DC output and a closed-loop control will provide varying the duty ratio of the switching element on the basis of the monitored DC output, to regulate the DC output such that the DC-DC converter, a starting voltage for initiating a discharge the discharge lamp and an operating voltage to maintain operation of the discharge lamp supplies; - wherein the control device provides an open-loop control is available, which interrupts the closed-loop control in order to provide a starting assistance period (P1) is available, in which the switching element (24) is controlled so that there is a according to a predetermined pattern - on and off ...