| 摘要 |
A dimming ballast circuit suitable for use with a phase dimmer has a switching network 70 consisting of a complimentary pair of switches 32, 34 which are driven by a low-power universally available controller IC 72. The controller IC 72 is configured with a floating ground arrangement 78. A current sensor 112 assists in generating a positive feedback signal 110 which is provided to an inverting input of operational amplifier 152 of compensation network circuit 62. A level shifted phase dimmer signal is generated by a level shifting circuit 60 and the error difference between the positive feedback signal 110 and the level shifted signal is amplified by operational amplifier 152 to, in turn, control the output frequency of controller IC 72. The level shifting circuit 60 shifts the dimming signal 68 from a ground reference system to a floating ground design. A resonant feedback circuit 18 includes capacitors 42 and 56 that couple energy from a resonant load 14 back to the input dimming signal 68 for the purpose of providing a continuous load to the phase dimmer and damping for an input EMI filter 220.
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