摘要 |
A circuit ( 20 ) for powering a load ( 50 ) includes a rectifier circuit ( 200 ), a voltage clamping circuit ( 300 ), and a DC-to-DC converter ( 400 ) such as a buck-boost converter. Voltage clamping circuit ( 300 ) is coupled between the rectifier circuit ( 200 ) and the DC-to-DC converter ( 400 ), and functions to prevent the input voltage (V<SUB>IN</SUB>) of the DC-to-DC converter ( 400 ) from exceeding a predetermined acceptable level, so as to protect the DC-to-DC converter ( 400 ) from damage due to transients in a voltage (V<SUB>AC</SUB>) provided by an AC line source ( 40 ). Preferably, voltage clamping circuit ( 300 ) is realized by an arrangement that includes a voltage divider circuit ( 320 ), a voltage sensing circuit ( 340 ), and an energy-limiting circuit ( 360 ), and is well-suited for use in power supplies and in electronic ballasts for powering gas discharge lamps.
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