| 摘要 |
Methods and apparatus are disclosed for supplying and controlling simmer current to a flashlamp 28. A direct current-to-direct current converter including a transformer 12, full-wave bridge rectifier 24, and first and second switching means 20 and 22 produces an output which is always higher than the maximum required by the flashlamp 28 at its lowest simmer current. The converter (12, 20, 22, 24) is coupled to flashlamp 28 through an inductor 26. The current I(s) through a pair of inductors 26, 30 is sensed by a lamp current sensing circuit 34 which turns the converter on or off, respectively, when a preselected minimum or maximum value is reached. The converter transformer 12 is maintained in its operating range by the switching of two devices such as power FET's 20, 22 so that one or the other of the two halves of the primary winding 14 is used alternately. The initial ionization of flashlamp 28 is provided by simmer trigger circuit 38. A transformer primary current sensing circuit 40 controls the toggling action which alternates the operation of switching means 20 and 22. The advantages of this method for supplying and controlling flashlamp simmer current include fast current response, extended flashlamp life, simplicity of design, high efficiency, and the avoidance of saturation and synchronization problems.
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