| 摘要 |
<p>A circuit and method for providing a DC control signal for setting the lighting level in an energy management control system, for maintaining the lighting level between preset minimum and maximum levels, and for providing either a gradual or a rapid transition between lighting levels, as desired.
<??>An oscillator provides a square or rectangular waveform the amplitude or duty cycle of which is controllable during each of a series of control intervals, each interval including the same number of waveform cycles. During the first interval one waveform cycle (or more) is set at an amplitude or duty cycle corresponding to the initial lighting level, while the other waveform cycles of the first interval are set at an amplitude or duty cycle corresponding to the initial lighting level. During each succeeding control interval the number of waveform cycles corresponding to the desired level is increased by one or more, while the number of waveform cycles corresponding to the initial level is similarly decreased, until the last control interval contains only waveform cycles corresponding to the desired level; after which the circuit continuously generates a waveform having an amplitude or pulse width corresponding to the (new) desired level.
<??>A rapid transition between the initial and desired levels can be provided by programmably reducing the number of control intervals to two, i.e. so that the first interval contains only waveform cycles corresponding to the initial lighting level and the second interval containing only waveform cycles corresponding to the desired lighting level.
<??>The oscillator waveform, thus amplitude or pulse width modulated, is rectified and filtered to provide a DC control signal which gradually or rapidly varies from the initial level to the desired new level. The control circuit is configured so that resistance values therein can be set to maintain the waveform amplitude or duty cycle within a selected range in response to minimum and maximum level set command signals. </p> |
