Some embodiments include a resonant converter klystron driver. A resonant converter klystron driver, for example, may include an input power supply; a full-bridge circuit coupled with the input power supply; a resonant circuit coupled with the full-bridge; a step-up transformer coupled with the resonant circuit; a rectifier coupled with a step-up transformer; a filter stage coupled with the rectifier; and an output coupled with the filter stage. In some embodiments, the output could be coupled with a klystron.

A light source device includes: a lighting circuit that includes a direct-current power source, a transformer, and a switching element, and generates electromotive force in a secondary winding of the transformer in accordance with switching of an ON state and an OFF state of the switching element; a dielectric barrier discharge lamp that is connected to the secondary winding of the transformer, and a controller that performs ON/OFF control on the switching element. The controller performs: a starting mode for repeating ON/OFF control on the switching element at a predetermined frequency at a time of starting; and a steady-state operation mode for alternately performing first control and second control after the dielectric barrier discharge lamp has been started, the first control being performed to repeat ON/OFF control on the switching element at the predetermined frequency, the second control being performed to maintain the switching element in the OFF state.

An LED driver provides constant output power with wide range output current and voltage. A parallel resonant tank configuration is supplemented by resonant gain clamping circuit configured to partially cancel voltage across the resonant capacitor during half-bridge switching operation. Voltage between the resonant components is clamped to one-half a driver input voltage, ensuring inductive switching of the half-bridge. An output transformer has a primary winding coupled across the resonant capacitor, with a center tap defining first and second portions. An output voltage clamping circuit is coupled across the DC input power source and to the center tap, wherein maximum voltage across the primary is clamped based on a relationship between respective numbers of turns in the first and second portions, and maximum voltage across a secondary winding is clamped based on a relationship between the respective numbers of turns in the secondary winding and the first and second portions.

In an aspect of a discharge lamp driving device, the controller is configured to supply a driving current to a discharge lamp, the driving current alternately having a first period and a second period. The first period includes a plurality of consecutive first unit driving periods each of which is constituted of a first polarity period and a second polarity period. The second period includes a plurality of consecutive second unit driving periods. In the first unit driving period, a length of one polarity period is larger than the other polarity period, and a duration ratio which is a ratio of the length of the one polarity period to the length of the other polarity period is equal to or more than a predetermined value. In the second unit driving period, the duration ratio is equal to or more than 1, and is less than the predetermined value.