| 摘要 |
A lamp driving circuit (10) for operating a discharge lamp has a series arrangement of a first and a second switching device (Q1, Q2) connecting supply voltage input terminals. An inverter resonant circuit (20, 30) shunts one of the switching devices and has an inverter inductance (L1), an inverter capacitance (C1), and lamp connection terminals (O1, O2). A control circuit (40) controls the switching devices to generate a lamp current (IL) commutating at a commutation frequency. During a first interval of a commutation period, the control circuit renders the first switching device alternately conducting during a first time period and non-conducting during a second time period at a high frequency being higher than the commutation frequency, and during a second interval of the commutation period, the control circuit renders the second switching device alternately conducting during a third time period and non-conducting during a fourth time period at a high frequency being higher than the commutation frequency. At the start of the first and second intervals of the commutation period, the first time period and the third time period, respectively, are extended for realizing an increased speed of commutation of the lamp current. Alternatively, at the end of the first and second intervals of the commutation period, the second time period and the fourth time period, respectively, are extended for realizing an increased speed of commutation of the lamp current. |
