| 摘要 |
The forward current IL through a light-emission device such as series and/or parallel connected LED 3 for a traffic signalling system (fig 4) is regulated by determining a control value PA from measuring the forward voltage UL and the forward current IL. The forward current IL is regulated so that the control value approximates a reference value UR. The control value PA may be determined by either addition or multiplication of voltages representing forward current UIL and voltage UL2, which can be weighted by correction factors so that their influence on the control value PA is either the same or greater for the forward current IL. Addition of these voltages may be achieved by series connection of a current sensing resistor RIL and a voltage divider comprising resistors RUL1. RUL2. Monitoring the forward voltage takes account of fluctuations between individual diodes and helps to maintain colour uniformity. Faults can be detected by monitoring current (Fig 4, IS1, IS2, IS3 ) emitted to each traffic light. |
