| 摘要 |
Direct current isolation and A.C. power line voltage reduction are provided in a first D.C. power supply by means of transformer coupling and in a second D.C. power supply by means of capacitor coupling which, additionally, provides suppression of differential mode and common mode components of high frequency noise or RF signals which may be present on the A.C. power line. The primary winding in the transformer coupled supply is switched and the D.C. output voltages produced by the supplies are combined to form a resultant bias signal of a first polarity and having relatively high current capability when the switch is closed, the bias signal being of a second polarity and having relatively limited current capability when the switch is open whereby high A.C. to D.C. conversion efficiency is achieved for either condition of the power switch. In a representative application of the bias supply, the first supply provides operating power for a video disc player and the bias signal controls the player antenna transfer switch.
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