| 摘要 |
<p>An energy-saving variable brightness control for e.g. a conventional electric lamp which, by use of reliable electronic circuits requiring no special wiring steps by the user, ensures that a lamp always comes on dim when the conventional switch is first activated, and only comes on bright if the switch is turned off and on again, or otherwise as desired by the designer. An electronic fading memory element is employed, which maintains a first, "recently on" state for a few seconds after power to the lamp has been turned off, then enters a second "long off" state. The power applied to the lamp is made dependent upon the state of this electronic fading memory element. In preferred embodiments a pair of electronic subcircuits is employed, one of which has a rectifier which applies a first half-wave of alternating current to the lamp, the other of which is normally in a condition which prevents the second half-wave of the alternating current from reaching the lamp when the lamp is switched on, but provides a time interval beginning when the lamp is switched off, during which the second subcircuit is in a condition to apply at least part of the second half-wave of the alternating current to the light in response to a further switching on of the lamp. In certain preferred embodiments the electronic fading memory element comprises a capacitor or thermistor which requires no external source of power after the lighting circuit is switched off.</p> |
