| 摘要 |
A resonant discontinuous power convener has a bipolar junction transistor (BJT) switch 208 whose collector terminal switches power to a magnetic energy store to transfer power from the input to the output and whose voltage is resonant during an off period. A voltage clamping circuit clamps the base voltage of the BJT to limit an excursion of the collector voltage of said BJT towards or beyond its emitter voltage during a resonant portion, due to forward bias of the collector to base junction. In particular it inhibits reverse bias and possible breakdown of the base emitter junction and latch up of a CMOS controller. The base clamp can comprise a switch 222, , a base voltage detector having a base voltage sample and hold S3, Chold, and a voltage threshold and one or more sources of base current. The base current can be driven during an on-period of the BJT to compensate for demagnetising current continuing to flow into the collector after the switch is turned on using switch 408 to apply force current to initially saturate the transistor. |
