| 摘要 |
The driving circuit has a switching arrangement (5 to 20) controlled by a input signal (2) in such a way, that an LED (1) is short circuited during a first switch state. In a second switch state the LED is supplied by a current source circuit in such a manner, that a large current flows initially through the diode, which is reduced to a smaller value after a predetermined time. A first transistor is pref. connected in series to the diode, with a control terminal, connected to ground via a current limiting element, such as a resistor (7), and connected to a positive supply via a second transistor (6). The control input of the second transistor is connected to a reference voltage via a resistor (8), and to ground via a controlled current source (9). A third transistor is connected between the control input of the second transistor and ground, and its control input is connected to control input of the first transistor. The controlled current source provides a maximum current during a first state in which the diode is switched off, and a lower current, which is further reduced after a certain time, during a second state, in which the diode is on.
|
