| 摘要 |
Circuit arrangements and methods are disclosed for providing a source of low power DC, direct and isolated from the main AC line. Applications of this circuitry include battery chargers and air ionizers. In this design, a high frequency ferrite transformer 16 is driven by signals created from a bilaterally conducting two state device 12 operating in series with a capacitor 15 . Utilizing a bilaterally conducting two state device 12 , capacitor 15 is alternately charged positive and negative to a certain voltage level depending on the characteristics of 12 . The device 12 will see an increasing voltage across it due to the increasing magnitude of the input AC waveform. When the voltage across 12 reaches the breakover voltage of the device, Vbo, it rapidly changes state from a blocking condition to one of full conduction. When this occurs the stored energy present in the capacitor 15 causes fast rise time pulses rich in high frequency harmonics to be impressed across the primary of the transformer 16 which has been designed with an operating frequency of 20 kHz or greater. A simple rectifier stage on the secondary consisting of 18 will convert the AC pulses generated on the secondary of 16 to the desired DC output voltage where it is filtered with capacitor 19 . For high voltage applications, a multi stage, Cockroft Walton voltage multiplier circuit may be utilized on the secondary of 16.
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