| 摘要 |
<p>A load resistance control circuit compares the actual value of a non-zero temperature coefficient load resistance to a desired load resistance magnitude, and generates a control signal varying as a function of the deviation of the actual load resistance from the desired resistance. A fixed portion of each of the load voltage and load current are sampled and compared to references, set such that the sampled portions will each be equal to an associated reference value, at the same time, if the load resistance is of the desired magnitude. An analog comparator can be used to add or remove charge to or from an integrating capacitor responsive to the actual load resistance being different from the desired load parameter. In a digital embodiment, a counter is incremented or decremented responsive to the actual load resistance differing from a desired value. The capacitor voltage or digital count then is used to affect a load resistance change, as, e.g. by establishing the time during which an additional load current, added to a constant load current, is allowed to flow through the load to change the load resistance. The constant load current and additional load current values are selected such that normal load operation requires at least some flow of additional load current, to place normal load current within the operational range of the load resistance control circuit.</p> |
